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WPC

1. INTRODUCTION

1.1 WPCs Composite: According

to

German

definition,

wood-plastic

composite

(WPCs)

are

thermoplastically processible composites that consist of varying contents of wood, plastics and additives , and are processed by thermoplastic shape forming techniques such as extrusion, injection molding or compression molding. The wood contents, usually wood chips, flour or especially wood fibers, thermoplastics and to a minor degree biopolymers or other serve as matrix. Additives common in plastic processing for example bonding agents, UV protective agents, lubricants and pigments, etc. In America WPCs are usually low price and profiles are easily made from recycled plastics and wood, in Germany and rest of Europe WPC is becoming a more advanced specially material, normally made from new materials and used in many specifications. The potential price advantage through hard to achieve, plays a minor role for WPCs, with technical and marketing aspects being more important. Ecological advantages are important sales argument for WPC products for the end customers: for example, tropical timber, typically used for Veranda decking can be omitted for the most part and WPCs can benefit from extended useful life. The ‗wood fiber as CO2 repository‘ and the improved CO2 balance in the life cycle of the products are good arguments against today‘s solely mineral oil based plastics. A large variety of engineering resins have been provided over the last few years. These resins are available in a variety of grades, molecular weights, melting points, formulations, containing materials of great variability. We have found that not every engineering resin thermoplastic is useful in the manufacture of the wood fiber composites. The engineering resin must be compatible in the melt wood fiber to form a high strength composite. The wood fiber must be fully wetted and penetrated, in its cellular structure, with the thermoplastic to form a high strength composite material. Further, the engineering resin MIT, Pune

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WPC must have thermal properties (melt flow properties or M.P. is lower than 240째C) that permit successful composite manufacture. Lastly, the resin should provide sufficient structural properties to the composite material. The engineering resin can be combined with wood fiber and can be contaminated with substantial proportions of hot melt adhesives, paints, solvents or adhesive components, preservatives resin, Pigment, plasticizer, etc. the composition can achieve in a final product high modulus, high compressible strength, reproducible, stable dimensions, superior modulus of elasticity and coefficient of thermal expansion that matches wooden members

1.2 Current WPCs Technology Trends: Current hot issues in WPC technology are weight reduction of the products and enhancement of mechanical properties for structural uses. Weight reduction can be achieved by using physical or chemical blowing agents that create cavities inside the polymer matrix. Unlike the general foaming process in unfilled thermoplastics, WPCs, highly-filled thermoplastic composites, place restrictions on foaming properties since wood fillers can negatively impact the foaming mechanism. High filler content causes foaming instability since the cells created exist in an open system, resulting in cell coalescence and collapse. Moreover, the cell sizes are various because of the variety of particle sizes. High filler content can lead to cell coalescence in the worst case and relatively weaker strength in several mechanical properties. Even though it is well known that there is a decrease in strength for foamed plastics, the strength decrease in WPCs is greater than with other thermoplastics. Researchers have focused on development of physical blowing agents using a phase of super critical fluids that can be dissolved into polymer melts under high temperature and pressure. The solubility of physical blowing agents helps distribute the cells evenly and limits the cell size so that the significant mechanical deterioration can be avoided. Foamed styrene-wood composites have been produced using reactive extrusion.

Another important issue is the increase of WPC applications for structural uses. To increase the stiffness of WPC-based polyolefin polymers, a cross-linking process has been examined using silane cross linking. The silane cross-linked high density polyethylene wood MIT, Pune

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WPC composites were stored at high humidity and high temperature to increase the degree of cross linking. The toughness was significantly increased but the stiffness did not change. In another study of cross-linked WPCs, a silane compound was used as a coupling agent to improve the interfacial properties between wood fillers and HDPE and another silane compound was applied as the cross linking agent of the polymer matrix. The combined silane compounds did not have any incompatibility issues since they are similar chemical structures. It was found that both mechanical properties of stiffness and strength were significantly improved. Wood flour acts as a solid structure networked with the cross-linked polymer matrix. Mechanical stresses can be internally transferred into the wood particle, a relatively stiff component of the composite, from the cross-linked polymer matrix. It is believed that a loading of wood filler treated with a coupling agent could interact with the polymer matrix in the cross-linking mechanism, resulting in an enhancement of the close contact and physical linkages between two different materials. The flexural modulus of cross linked HDPE- wood composite was around 470,000 psi which is two times higher than those of HDPE- WPC‘s in the current market.

To upgrade the stiffness of WPCs, the selection of the polymer matrix is one of the major issues. Polyethylene terephthalate (PET), polyamide (PA, Nylon), and acrylonitrile butadiene styrene (ABS) are typical engineering plastics with superior mechanical and thermal properties. The melting or plasticizing temperatures, however, range from 230°C to 300°C which is enough to cause serious thermal degradation of the wood. Several strategies have been used to overcome this thermal degradation. Two extruders were combined to minimize the retention time for wood exposure to the high processing temperatures. One extruder feeds melted polymer into a twin screw extruder designed for efficient and rapid mixing to compound the polymer melt and cold wood flour. The retention time of wood to be exposed to very hot polymer melt was controlled at less than 4 minutes residence time. In this process, the severe thermal degradation could be avoided and nylon-wood composites could be produced. Another method of using engineering plastics in WPCs is viscosity modification of the pure engineering plastics. Several viscosity modifiers, which have low viscosity or special functional groups, were tested to examine the viscosity decreasing effect. Moreover, various polymer blends were tested as well to observe the changes in rheological properties. MIT, Pune

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WPC

Nanocellulose which can be fabricated by chemical and mechanical processes has recently become the focus of WPC manufacture. Due to the high aspect ratio and nanoscale sizes of nanocellulose, an expectation of remarkable increases in mechanical and physical properties of composites has received attention. In current processes, the nanocellulose, however, can only exist unagglomerated in water suspensions since the nano scale particles cannot be maintained after secondary processes, such as drying. During the drying process, the cellulose polymer chains are easily agglomerated due to hydrogen bonding between the polymer chains, resulting in increases of particle sizes. With this motivation, cellulose nanowhisker suspensions were plasticized using a plasticizer and pumped into an extruder to produce cellulose acetate butyrate composite reinforced with cellulose nano-whiskers. It was found that the tensile modulus and strength indicated an improvement with 300% and 100%, respectively, compared to control samples. Various studies are being conducted in developing efficient drying methods, fictionalization of nanocellulose, development of new processes directly using nanocellulose suspensions in thermoplastic matrices, etc.

Technology Status of WPCs: •

Global market size : 320,000MT in 2000

•

Expected Volume : More than double in 2005

Figure No.01 -Market Potential MIT, Pune

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WPC

1.3 Advantages and Disadvantages of WPCs WPCs do not corrode and are highly resistant to rot, decay, and Marine Borer attack, though they do absorb water into the wood fibers embedded within the material. They have good workability and can be shaped using conventional woodworking tools. WPCs are often considered a sustainable material because they can be made using recycled plastics and the waste products of the wood industry. Although these materials continue the lifespan of used and discarded materials, and have their own considerable half-life; the polymers and adhesives added make wood-plastic composite difficult to recycle again after use. They can however be recycled easily in a new wood-plastic composite, much like concrete. One advantage over wood is the ability of the material to be molded to meet almost any desired shape. A WPC member can be bent and fixed to form strong arching curves. Another major selling point of these materials is their lack of need for paint. They are manufactured in a variety of colors, but are widely available in grays and earth tones. Despite up to 70 percent cellulose content (although 50/50 is more common), the mechanical behavior of WPCs is most similar to neat polymers. This means that they have a lower strength and stiffness than wood, and they experience time and temperature-dependent behavior The wood particles are susceptible to fungal attack, though not as much so as solid wood, and the polymer component is vulnerable to UV degradation It is possible that the strength and stiffness may be reduced by moisture absorption and freeze-thaw cycling, though testing is still being conducted in this area. Some WPC formulations are also sensitive to staining from a variety of agents. The next generation of composite decking includes a durable plastic cap that adds added protection. A PVC cap surrounding the wood plastic composite material helps reduce staining, fading and scratching that may occur with 1st generation composite decking. Capped composites cost considerably less than pure plastic decking as the core is still wood plastic composite materials. Although PVC capping is one type of cap, there are many different types of caps that are coming out on the market. They will also have the same properties of reducing staining, fading, and scratching.

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WPC

1.4 Application benefits •

Improved dimensional stability - increased strength

Lower processing temperatures - less energy used

Increased heat deflection temperature - reduced thermal expansion

Up to 30% reduced cycle time for injection molded products - increased productivity

Approximately 10 - 20% lower specific gravity- lighter products

Reduced shrinkage - lower internal shear in pultrusion application

Low volumetric cost

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WPC

2. LITERATURE SURVEY Wood Plastic Composites (WPCs) are produced by thoroughly mixing ground wood particles and heated thermoplastic resin. The most common method of production is to extrude the material into the desired shape, though injection molding is also used. WPCs may be produced from either virgin or recycled thermoplastics including HDPE, LDPE, PP, PVC, PS, ABS, PET and PLA. Polyethylene based WPCs are by far the most common. Additives such as colorants, coupling agents, UV stabilizers, blowing agents, foaming agents, and lubricants help tailor the end product to the target area of application. Extruded WPCs are formed into both solid and hollow profiles. A large variety of injection molded parts are also produced, from automotive door panels to cell phone covers. In some manufacturing facilities, the constituents are combined and processed in a pelletizing extruder, which produces pellets of the new material. The pellets are then remelted and formed into the final shape. Other manufacturers complete the finished part in a single step of mixing and extrusion. With up to 70% cellulose content, wood plastic composites behave like wood using conventional woodworking tools. At the same time, they are extremely moisture resistant. There is little or no water present, thus increasing resistance to rot. Wood-polymer composites are already widespread in outdoor use for decking, cladding, park benches, etc. There is also a growing market for potential indoor uses such as door frames, trim, and furniture.

2.1 Compounding Manufacturing of WPCs can be done using a variety of processes; however, the key to making any WPC is through efficient dispersion of the wood component into the thermoplastic matrix (‗compounding‘). Generally, this can be accomplished in twin-screw extruders, two roll mill or other melt-blending processes. Once the materials are sufficiently mixed, the composite can then be formed into the final shape using forming technologies such as extrusion or injection molding. The raw materials are mixed either in batches or by a continuous process, and the Mixture forced through a die (sheet or profile extrusion), injection molded or Compression MIT, Pune

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WPC molded. Most WPCs are profile extruded, ranging from solid sections in Common sizes, to hollow profiles. The processing temperature depends on the plastic Used in the mix but is typically around 150° C.

2.2 Additives Development and Growth of WPC While the bulk of a WPC is wood flour and thermoplastic polymer, a variety of materials are added in relatively small quantities. These additives are included for a variety of reasons: • Lubricants help the molten WPC mixture move through the processing equipment • Coupling agents improve the wood and polymer interaction. Wood is naturally hydrophilic (attracts water), while the thermoplastic polymers are hydrophobic (repel water). This basic chemical incompatibility makes it very difficult to bond polymers to wood. The use of coupling agents can help to overcome this incompatibility. • Fillers, such as talc, are used to reduce the cost of materials and to improve stiffness and durability. • Biocides can be added to protect the wood component of WPCs from fungal and insect attack. Zinc borate is the most commonly used wood preservative added to WPCs. Fireretardant chemicals reduce the tendency of the WPCs to burn. UV stabilizers help protect the plastics from degrading in the sun. • Pigments are added to provide a desired color to the product. UV stabilizers can help to protect the color, but some fading and whitening will occur with most WPC‘s exposed to sunlight. •

Tailor-made lubricants

Antimicrobials

Blowing agents

Flame Retardants

Fly Ash

Coupling Agent as compatibilizer

Plasticizers

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WPC •

Thermal stabilizers

EVA

Antioxidants.

Pigments

2.3 Material Selection of WPC To ensure the quality of finished components, it is critical to utilize high-quality thermoplastic pellets. There are two main areas of the pellet composition to focus on: 1.

Dryness. Surface moisture should be less than 1.5% while internal pellet moisture should be less than 1%. Failure to control moisture content can result in visible splay and increased brittleness.

2.

Proper encapsulation and uniformity. Pellets should be clean and relatively consistent in size and shape. There should be no fines, chads, or streamers. In addition, there should be no powdery residue, which is a sign of improper equipment design or maintenance on the part of the pellet manufacturer. One of the benefits of the current generation of WPCs is that they can be blended very

efficiently with additional unfilled PP or other resin. In this manner, molders can still reduce their material costs and obtain the ―green‖ benefits of the material while tailoring the woodfiber level. Through blending, molders can achieve different performance characteristics—for example, improve the shatter resistance of components such as car bumpers or increase the structural rigidity of neat resin. Not every engineering resin is useful in the wood polymer composite materials. First the engineering resins must have a surface energy such that the material is compatible with the wood fiber. The resins are not compatible with the wood fiber to intimately bond and penetrate the wood fiber to obtain sufficient engineering properties. Surface energy is greater than about 40 dyne/cm. further; we have found that the engineering resin must have sufficient viscosity at processing temperatures substantially less than the decomposition temperature of wood fiber. Accordingly, the processing temperature of the thermoplastic material must be substantially less than about 340◦C preferably between 180 to 240° C

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WPC

3. EXPERIMENTAL WORK

3.1 Objectives The objective of the present work is to prepare wood flour based composite for applications like furniture, window profile, building construction application, interior decoration purposes, decking, etc. Wood flour has been used as a filler material. It is waste product from the lumber industry. Therefore its cost very low, which is in tons, reduces the cost of the composite. The composite can be termed environmental friendly for utilization of the waste material. Various mechanical properties of the composite were studied. Tensile test was carried out to study the effect of wood flour on the strength and modulus or stiffness of the composite. Impact test was carried out for determine the impact energy absorption and study the nature of material. DSC test carried out for thermal behavior of the Nylon 6-Eva blend and composite material.

3.2 Material The engineering resin NYLON 6 was used as a major matrix material and EVA as a minor material. It was a blend of NYLON 6 and EVA. EVA was added as polymeric plasticizer improves processing characteristics and it also act as an impact modifier. Wood fiber had a minimum length of at least about 0.1 mm because wood flour tends to be explosive at certain wood to air ratios. Further, wood fiber of appropriate size of aspect ratio greater than 1.5 tends to increase the physical properties of the extruded material.



Nylon 6

M28RC (N) grade of NYLON 6 material manufactured by Gujlon Ltd, India was used. The density of NYLON 6 was 1.14 gm/cc and MFI was 2.8 gm/10 min.

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WPC Extremely high melting temperature can be achieved by adjusting the relative amount of the aromatic component. Good mechanical properties at elevated temperatures. Good resistance to chemicals. Good dielectric properties. Dimensional stability is in the presence of moisture. It‘s having Low moisture absorption, good impact resistance, good dielectric properties, good resistance to chemicals, easy to process.

Table No.01 -Data sheet of Nylon 6 Properties

Units

Melting temperature

◦K

Glass transition temperature

Density

◦K

gm/cm³

Condition -

-

-

Values 583-613

473

1.18

Linear thermal expansion coefficient

Tensile modulus

Tensile strength

Heat Deflection Temperature

MIT, Pune

%

Mpa

Mpa ◦K

60◦C

Dry and Moist

Dry and Moist

At 624 psi

0.2

3200

90

473

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WPC

Ethylene Vinyl Acetate Copolymer ‗Relene EVA 1802‘ grade of Ethylene Vinyl Acetate (EVA) manufactured by Reliance

Polymers, India. Ethylene vinyl acetate (also known as EVA) is the copolymer of ethylene and vinyl acetate. The weight percent vinyl acetate usually varies from 10 to 40%, with the remainder being ethylene. It is a polymer that approaches elastomeric materials in softness and flexibility, yet can be processed like other thermoplastics. The material has good clarity and gloss, barrier properties, low-temperature toughness, stress-crack resistance, hot-melt adhesive water proof properties, and resistance to UV radiation. EVA has little or no odor and is competitive with rubber and vinyl products in many electrical applications.

Relene EVA1802 is a co-polymer of Ethylene and vinyl acetate. It is produced by continuous bulk polymerization process using stirred autoclave reactors. EVA1802 is recommended for injection, extrusion, compression and blow molding process. This material exhibits good flexibility, good transparency, good impact strength and superior ESCR.

Regulatory Information Meets the requirement stipulated in standard IS: 10146-1982 on ―Specification for Polyethylene for safe use in contact with foodstuffs, pharmaceuticals, and drinking water‖. It also conforms to positive list of constituents as prescribed in IS: 10141- 1982. The grade and the additives incorporated in it also comply with the FDA: CFR Title 21.177.1520, Olefin polymers. MIT, Pune

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WPC Table No.03- Data sheet of EVA Property

Test Method

UNIT

TYPICAL VALUE

RIL Test Method

%

18

Density (23 ° C)

ASTM D 792

gm/cm

0.936

Melt Flow Index

ASTM D1238

gm/10 min

2

ASTMD638

Mpa

20

Elongation at Break

ASTM D638

%

750

Vicat Softening

ASTMD 1525 ( 1 Kg

Temperature

Load )

°C

64

Vinyl Acetate Content

Tensile Strength at Break

Applications: Microcellular Products, Profiles, Injection and Blow molded components.

Storage Recommendations Bags should be stored in dry/closed conditions at temperatures below 50°C and protected from UV / direct sunlight

Wood Flour Wood fiber, in terms of abundance and suitability can be derived from either soft

wood or evergreens or from hard wood commonly known as broad leaf deciduous trees. Soft woods are generally preferred for fiber manufacture because the resulting fiber is longer; contain high percentage of hemicelluloses than hard woods. While soft wood is the primary source of fiber for the invention, additional fiber make-up can be derived from a number of secondary or fiber reclaim sources including bamboo, rice, sugar cane and recycled fibers from newspapers, boxes, computer printouts, etc.

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WPC The wood fibers are by-product of sawing or milling soft woods commonly known as sawdust or milling tailings. Such wood fibers have a regular reproducible shape and aspect ratio. The fibers based on random selection of about 100 fibers are commonly at least about 0.1 mm in length, up to about 1 mm in thickness and commonly have an aspect ratio of at least 1.5 preferably, at least about 1.8. Preferably, the fibers are about 0.1 to 5mm in length with an aspect ratio between about 2 and 7, preferably about 2.5 to 6. Wooden members are commonly ripped or sawed to size in a cross gain direction to form appropriate lengths and widths of wood materials. The byproduct of such sawing operations is a substantial quantity of saw dust. In shaping a regular shaped piece of a wood through machines; which selectively removes wood from the peace leaving the useful shape. Such milling operations produce substantial quantities of sawdust. Wood Flour Used In This Project: The wood project used in this project is from the same variety of wood commercially available in India as ‗Ghana Teak‘; generally Tactonna Grandis. The tensile strength and pin bearing properties of the wood from fully grown tree were tested and are given below for the purpose of reference. Obviously woof flour will have altogether different properties. Properties of the Wood Used: Pin bearing strength: 34 Mpa Tensile properties: 

Tensile strength in fiber direction: 73.275 Mpa

Modus in fiber direction: 9562.3 Mpa

Moisture Absorption: 40.23% Wood flour of 90 meshes was used for this experimental work. It was dried for 8 hours at 120°C.

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WPC

Fly Ash Fly ash is a residue formed after burning of coal in thermal electrical power plant. In

India, 75% of the power is generated in the thermal power plants which is use as coal as fuel. Disposal and use of fly ash is major issue as it has potential to contaminate surface and ground water. There are various applications proposed for use of fly ash. They include: 

Cement and concrete application

Ceramic sand refractions

Plastic fillers

Metal matrix composites

Carbon adsorbent

Fly ash is the finely divided mineral residue resulting from the combustion of the ground or powdered coal in the electric generating plants. The amount of the fly ash was produced depend on the source and grade of coal used. Generally, it is 12% to 16% of the coal burned. It consists of inorganic matter present in the coal that has been fused during combustion. The material is solidified while suspending in the exhaust. It is collected from the exhaust by electrostatic precipitators. As the particle solidified while suspended in the exhaust, they are generally, spherical in shape. Fly ash particle collected in electrostatic precipitators are usually 0.74-0.005mm in size. Fly ash contains both crystalline and glassy phase materials. The type of phase depends on the combustion and gasification process used. When the maximum temperature of the combustion is above 1200°C and cooling time is short, the ash produced is glassy phase. When the cooling process is gradual a crystalline phase compound is formed.

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WPC Fly ash used in project work Pozzoplast: Pozzoplast is a specialized fly ash, obtained by selection from power station. Fly ash has resulting from the combustion of pulverized bitumous coal. Pozzoplast is subjected to strict quality control. Pozzoplast is used as a partial cement replacement material in repairing mortar for plasters masonry work. Table No.04- Data Sheet of Pozzoplast Fly ash: Fineness-Specific surface by Blaine‘s Permeability Method

280

ROS(Residue on Sieve) 25micron sieve

Not Specified

ROS 45 micron sieve

25

Loss on Ignition (max.)

2.0

Lime Reactivity

4.5

Moisture Content (max.)

0.50

Soundness by Autoclave

0.05%

Compressive strength At 28 Days -% of Plain Cement Mortar

80%

3.3 Physical Properties 

Density and Porosity

The density of the product, porosity or void content of the product and water absorption is important from application point of view. Density was determined by using the Density Meter based on Archimedes Principle as per ASTM D792- Method A. Theoretical value of density for all the composites was determined by using rule of mixtures. Porosity was determined based on theoretical density. Scope: Density is the mass per unit volume of a material. Specific gravity is a measure of the ratio of mass of given volume of material at room temperature to the same volume of MIT, Pune

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WPC deionized water. Specific gravity and density are especially relevant because plastic is sold on cost per pound basis and lower density or specific gravity means more material per pound or varied part weight. Test Procedure: The specimen is weighed in air then weight when immersed in distilled water at room temperature using a sinker and wire to hold the specimen completely submerged as required. Density and specific gravity are calculated as: Density, kg/m3= (specific gravity) x (997.6) Specific gravity= a / [(a+w)-b] Where, a= mass of specimen in air. b= mass of specimen and sinker (if used) in water. W= mass of totally immersed sinker if used and partially immersed wire. Equipment used: Mettler Balance. Fixture for weighing samples in water Porosity: Porosity was determined based on theoretical density. 

Moisture and Water Absorption

Moisture absorption of plastic is related to properties such as electrical insulation resistance, dielectric losses, mechanical strength, appearance and dimensional stability. Increase in moisture content affects the insulation resistance and elastic modulus. There is decrease in insulation resistance and modulus with increase in water absorption. MIT, Pune

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WPC For the present experimental work, hygroscopic wood flour is used as filler in the hygroscopic Nylon 6-EVA matrix. The moisture content of wood in the trees varies from 30% to 200%. So, addition of wood flour, even in dried form, will lead to increase in moisture absorption of the composites. The effect of water absorption on the properties of the composite depends on type of exposure that is by immersion in water or exposure to high humidity. Also it is dependent on the shape of part and inherent properties. Water absorption was carried out according to ASTM D570-98. The specimen was conditioned at 105 to 110°C for 1 hour. 24 hour immersion procedure was used. This test method covers determination of water absorption of plastic when immersed.

3.4 Mechanical Properties 

Impact Properties

Izod impact strength testing is an ASTM D-256 standard method of determining impact strength. Notched and un-notched samples are generally used to determine impact strength. The objective of izod impact strength is to measure the relative susceptibility of standard test specimen to the pendulum type impact load. The results are expressed in terms of kinetic energy consumed by the pendulum in order to break the specimen. The energy needed to break a standard specimen is actually the sum of energies needed to deform it, to initiate its fracture, and to propagate the fracture across it and the energy expended in the tossing the broken ends of the specimen. The specimen used in izod test must be notched. The reason for the notching the specimen is to provide a stress concentration area that promotes a brittle rather than a ductile failure. A plastic deformation is prevented by such type of notched in specimen. The impact values are seriously affected because of notch sensitivity of certain types of plastic material. The izod test required a specimen to be clamp vertically as a cantilever beam. The specimen struck by a swing by a pendulum released from a fixed distance from the specimen clamps. Impact values are read directly in joules from the scale. The impact strength is calculated by dividing the impact values obtained from the scale by thickness of the specimen. MIT, Pune

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WPC Apparatus and Test Specimen: The testing machine consists of heavy base with a vise for clamping a specimen in placed during the test. A pendulum type hammer with an antifrictional bearing is used. Additional weights may be attached to the hammer for breaking the tougher specimens. The test specimen can be prepared either by molding or cutting them from sheet. The izod test specimen is 2.5×0.5×0.125 in. The notch is cut into a specimen very carefully by a notchcutting machine. The recommended notch depth is 0.100 in. 

Tensile Properties:

Tensile elongation and tensile modulus measurements are among the most important indications of strength in the material and are most widely specified properties of plastic materials. Tensile tests in a broad sense, is a measurements of ability of material to withstand forces that tends to pull it apart and to determine to what extent the material stretches before breaking. Tensile modulus, an indication of relative stiffness of the material, can be determined from stress-strain diagram. Apparatus: Tensile testing machine of a constant rate of crosshead movement is used. It has a fixed or essentially stationary member carrying one grip and a movable member carrying second grip. A controlled velocity drive mechanism is used. A load indicating mechanism capable of indicating total tensile load with an accuracy an extension type indicator commonly known extensometer is used to determine to distance between two designated points located within the guage length of the test specimen as the specimen is stretched. Test Specimen and Conditioning: Test specimens are prepared either injection molded or compression molded. ASTM D 638 type tensile test specimen most commonly used for test. Test conducted in the atmosphere of 23 ± 2°C and 50 ± 5 % relative humidity. Test specimen is dumbbell shape having dimensions 4.5× 0.3 × 0.12 inch.

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WPC Procedure: The speed of testing is the relative rate of motion of the grips or test fixture during the test. The most frequently employed speed of testing is 0.2 inch per minute. The test specimen is positioned vertically grips of testing machine. The grips are tightened evenly and firmly to prevent any slippage. The speed of testing is set at the proper rate and the machine started. As the specimen elongates, the resistance of specimen is increases and is detected by load cell. This load value is recorded by the instrument. The elongation of specimen is continued until the rupture of the specimen is observed. The tensile strength and modulus are calculated as followed: Tensile strength

Tensile modulus



Compression Testing

Compressive properties describe the behavior of material when it is subjected to compressive load at a relatively low and uniform rate of loading. Apparatus: The universal testing machine used for testing compressive strength of material. A deflectometer or a compressometer is used measure any change in distance between two fixed points on the test specimen. Test Specimen: The test specimen can be prepared either by molding or cutting them from sheet. The test specimen is 2.5Ă—0.5Ă—0.125 inch.

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WPC Procedure: The specimen is placed between the surfaces of the compression tool, making sure that ends of the specimen are parallel with the surface of the compression tool. The test is commenced by lowering the movable crosshead at a specified speed over the specimen. The maximum load carried out by specimen the test is recorded. Compressive strength is calculated by dividing the maximum compressive load carried by the specimen during the test by the original minimum cross-sectional area of the specimen. The result is expressed in lb/in². Compressive modulus is calculated by dividing the change in stress by corresponding change in strain.

3.5 Characterization 

Differential scanning Calorimetry (DSC) Differential Scanning Calorimeter, the most widely used thermal analysis technique,

the heat flow rate to the sample (differential power) is measured while the temperature of the sample, in a specified atmosphere, is programmed. Because all materials have a finite heat capacity, heating or cooling a sample specimen results in a flow of heat in or out of the sample. The heat flux DSC employs a disk containing sample and reference positions which are heated by a common furnace. The differential heat flow to the sample is proportional to the temperature difference that develops between sample references junctions of thermocouple. The power compensations approach controls a temperature enclosure around the sample and reference individually. Through amplified feedback from platinum resistance thermometers, it records the differential energy flow necessary to maintain the sample on the specified temperature program. With either approach the output is heat flow, normally expressed in milliwats, watts/gram (normalized), or watts/gram-degree. Test Procedure: A small quantity of sample, usually 5-10 mg, is weighed out into an inert capsule. The encapsulated sample is placed in the DSC sample holder or onto the sample platform of a DSC cell disk. In the attached control module or computer, the operator selects a temperature MIT, Pune

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WPC range and heating rate, or perhaps a more temperature program. The hypothetical DSC curve has showing both endothermic and exothermic changes in a polymer. Constant energy input is required to heat the sample at a constant rate. This establishes a baseline. At a transition point, the sample requires either more or less energy depending on whether the change is endothermic or exothermic. For example, when the glass transition point is reached, the heat capacity increases. The midpoint is taken as the glass transition temperature. When a polymer reaches the melting point, it requires more energy (endothermic) to melt the crystalline structure. The area of the peak in units of energy is the enthalpy of the enthalpy of the fusion, the heat of melting. The temperature dependence of the peak and its shape give information about degree of crystalline, the molecular weight the molecular weight distribution, degree of branching, copolymer blend ratio and or processing history. When a sample cures, more energy is released, and the change is exothermic. The area of the curing peak is proportional to the number of crosslink that were formed. This indicates degree of cure. The shape of the curing curve can be analyzed to obtain the reaction kinetic parameters.

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WPC

4. PROCESSING TECHNIQUE OF WPC

4.1 Preparation of Blends A polymer blend is a thermodynamic mixture of the two polymers to create a new polymer which having different physical properties. The blending with suitable elastomeric material has become one of the important means for the improvement of the toughness of a brittle plastic. Nylon is one of the most important engineering plastics. It is characterized by high stiffness and good resistance to hydrocarbon solvents. However, as a pseudo ductile polymer, it usually has high Unnotched but low notched impact strength. (This refers to its resistance to fracture using standard tests without and with preset notches carved into the material.) Blending with suitable elastomers can dramatically increase the material‘s notched resistance to breakage. Nonpolar hydrocarbon elastomers are used most commonly, 3–5 while their high-polarity counterparts have rarely been reported as impact modifiers to toughen nylon.

Ethylene-vinyl acetate (EVA) copolymer forms either a type of plastic or an elastomer, depending on its vinyl-acetate (VA) content. Nylon 6, with a high notched impact strength of approximately 50kJ/m2, can be obtained by incorporating EVA (with a VA content of 18% by weight, wt %) and maleic anhydride (MAH). However, high- VA-content (40wt %) EVA is not known as an impact modifier for nylon. We therefore systematically investigated the toughening effects of EVA with 18% VA contents on nylon, with maleic anhydride (MAH) grafted onto it (EVA-g-MAH: maleated EVA) as a compatibilizer (which ensures the stability of the copolymer blends).

Here these two polymers are Nylon 6 and EVA. It is immiscible type of blend. Nylon 6 was dried for 4-5 hours in the oven at 80-85°C. After that EVA was dissolved in the xylene (because xylene is colorless liquids having characteristics odor and is used as a solvent and diluents for lacquers) and placed in the oven at 70°C.

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4.2 Composition and Pellet Manufacture In the manufacture of the composition and pellet of the invention, the manufacture and procedure requires two important steps. A first is blending step and a second is pelletizing step. During the blending step, the nylon 6, EVA and wood fiber are intimately mixed by two roll mill mixing component to form polymer wood composite The material feed to Two Roll Mill can comprises from about 30 to 40 wt % of sawdust including recycled impurity along with the balance an engineering resin composition. Preferably, about 35 to 40 wt% wood fiber is combined with 60 to 70 wt % of resin. The resin feed is communally in small particulate size which can take the form of flake, pellet, powder, etc.

Figure No.02- Two roll mixing process of WPC When the mixing is started the evaporation of xylene takes place because it‘s having very low boiling point. The temperature of the first roll is 230°C and second roll 250°C. The speeds of the both rollers are also different because homogeneous mixing takes place on to the rollers. Fly ash added into the mixture and after that in the whole mixture a small quantity of maleic anhydride added as a compatibilizer. Two roll mill having salient features: MIT, Pune

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WPC 

The rolls are electrically heated with cartridge heaters for optimum heat distribution over the entire roll surface with programmable PID auto tune type temperature controllers. Temperature of two rolls can be sensed individually by a separate thermocouple system. The maximum roll temperature up to 400°C can be achieved.

The surface of the rolls is hard chrome plated, ground and mirror polished.

The drive system consists of AC geared motor with programmable variable frequency drive to give very high starting torque. The transmission of speed is through heavy duty chains which results into precise nip gap adjustment without any negative effect. Digital or Dial type nip gap indication is also available optional.

The Roll RPM can be set from 2 to 20 RPM.

The control cabinet in mounted on a swing arm enabling a multitude of position for best viewing possibility.

The cooling of this roll is done by water cooling arrangement and water is collected in a stainless steel water collecting tank which is at the other end of roll shaft. This system will help in cooling of the rolls rapidly during the shutdown or change over requirement. The second step is pelletizing step. For the pelletizing of the thick sheet the Granulator

is used. Plastic granulators are large, shredder-like machines found primarily in the plastics industry. They are used to break plastic products down so they can be recycled. It is no secret that plastic trash such as bottles, bags, packaging, and other plastic products represent as much as 40% of the solid waste that goes into our landfills. It is also no secret that plastic is not biodegradable – meaning it does not break down naturally to become part of the earth and may subsist for thousands of years. How Plastic Granulators Operate

Plastic granulator takes in wood-polymer composite sheet which was made on the two roll mill and grind them down into flakes. The resulting plastic-flake product was created by plastic granulators. With the help of sifter the same size of granules were sieved into the chamber.

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WPC

Figure No. 03 WPC Pelletizing Process

Plastic granulators are comprised of: 

A large electric motor that turns a rotor

Cutting blades are attached to the rotor

These blades are available in a diverse array of shapes and sizes

When used plastic material is placed inside the chamber, the rotating blades shred it into granules.

Additionally, a screen is placed inside. This screen acts as a sifter, making sure the plastic is small enough to be useful on the open market. Plastic pieces too large to be sold - more than .125 to .375 inches (0.318 to 0.953 centimeters) - are caught by the sifter and reprocessed until they are small enough.

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Figure No.04 WPC Manufacturing Process

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4.3 Processing Guidelines

When article molded using proper temperatures, speeds and a non-restricted flow path, WPC parts will exhibit uniform color and dispersion of wood fibers, minimal stress, smooth surfaces, and no evidence of gassing. The two most important principles to keep in mind for molding WPCs and other biocomposites are to avoid excessive heat and shear. While traditional thinking might suggest that the wood fiber in WPCs would act as a flow inhibitor, Wood/Nylon 6- EVA blend actually flows very quickly at low temperatures and pressures. As a result, injection molders can achieve significant energy savings. They can also achieve shorter cycle times and higher productivity due to reduced filling and cooling times.

Figure No. 05- Injection Molded WPC Specimen Typical temperatures for molding wood/ Nylon 6- EVA blend composites are 190 to 200째C for the rear zone, 220-225째C for the middle zone, 230-235째C for the nozzle tip. Molding pressures of course depend on the design of the part as well as the runner system and gates.

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WPC Filling speeds for WPC molding deserve attention. While the material tends to flow very quickly, it is important to avoid excessively short fill times as the material is shear sensitive. The nozzle tip used in the molding process should have an orifice as close as possible to the diameter of the sprue to minimize shearing. Smaller tips may cause increased shear as well as discoloration caused by overheating of material as it enters the mold. Injection molded WPC components are rather ―natural‖ in appearance, with a lightbrown tone and a uniform grain. However, a high-gloss finish is achievable, and the material can be dyed in various colors with excellent color uniformity.

Figure No.06- Injection Molding Machine used for specimen preparation

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5. TEST RESULTS AND DISCUSSION

5.1 Physical Properties Following three properties were evaluated:1. Density and Porosity 2. Moisture Absorption 3. Water Absorption 

Density And Porosity:

Theoretical density of the composites was calculated by using the rule of mixture,

ρc

(

) (

) (

)

Where, ρc= density of composite ρ1 ,

ρ2,

ρ3….

ρn = density of components 1 to n

W3….Wn = weight fractions of component 1 to n

W1, W2,

The system consisting following components: 

Nylon 6

Eva

Wood flour

Fly ash

Maleic anhydride Individual components densities are: 1.

Density of Nylon 6 = 1.13 gm/cc

2. Density of EVA = 0.935 gm/cc MIT, Pune

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WPC 3. Density of Wood = 1.54gm/cc 4. Density of Fly ash = 2.218gm/cc 5. Density of maleic anhydride= 1.48gm/cc. The void content or porosity can be calculated by formula

Where, Vv= volume fractions of voids or porosity ρc= theoretical density ρ= actual density experimentally measured Table No.05 Results of density and porosity: Actual

Sr.

Formulations

No.

1.

2.

Nylon 6-EVA Blend (EVA dispersed in xylene) Nylon 6-EVA Blend (without xylene)

Theoretical Density

Density

% of Porosity

gm/cc

gm/cc

0.95

1.025

7.32

0.945

1.023

7.62

3.

Blend + 40WF

1.07

1.209

11.49

4.

Blend + 30WF

1.053

1.172

10.15

5.

Nylon 6

1.121

1.13

0.80

6.

EVA

0.929

0.935

0.64

Moisture Absorption

The moisture content was determined as per ASTM D-570 by using the formula,

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The test was carried out by weighing a small quantity of material and placed it in an oven at specified temperature 100° C for 2 hours. The material was removed from the oven at the end of the test period and placed in desiccator for 30 minute and allowed to cool. Dry material was reweighed to the nearest 0.001gm Table No.06-Results of % of Moisture Absorption: Materials

% of Moisture Absorption

Nylon 6

3.0

EVA

0.08

Nylon 6-EVA Blend (xylene)

2.66

Nylon 6-EVA Blend (without xylene)

2.71

Blend + 40WF

2.81

Blend + 30WF

2.25

Water Absorption

This test was also determined as per ASTM D-570. The specimens were conditioned by drying in an oven at temperature 100° C for 2 hours, cooled in a desiccator and immediately weighed. Then specimens immersed in water at temperature 100° C for 2 hours, and then removed for weighed. The % increase in weight during immersion is calculated as follows:

The increased in % weights (Water absorption) given below: MIT, Pune

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WPC Table No. 07- Results of % of water absorption Materials Formulation

% of water Absorption

Nylon 6

1.8

EVA

0.05

Nylon 6-EVA Blend (xylene)

2.03

Nylon 6-EVA Blend (without xylene)

2.83

Blend + 40WF

1.69

Blend + 30WF

1.90

5.2 Mechanical Properties 

Impact Strength: Table No.08-Result of Impact Strength Notched Sample

Sr. No.

Materials Formulation

Impact Energy (J)

Nylon 6-EVA Blend 1.

3.

4.

MIT, Pune

Strength(J/m)

Impact Energy (J)

Impact Strength(J/m)

0.8

266.6

1.6

533.3

1.0

333.3

1.4

466.6

Blend + 40WF

0.1

33.30

0.2

66.60

Blend + 30WF

0.12

40.00

0.23

76.60

(xylene) Nylon 6-EVA Blend

2.

Impact

Unnotched Sample

(without xylene)

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WPC

Figure No.07-Impact Testing Machine

Figure No.08- Notch Cutting Machine MIT, Pune

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WPC Graph No.1-Sample 1 Nylon 6-EVA Blend (EVA dispersed in xylene)

Graph No.2-Sample 2 Nylon 6-EVA Blend (EVA not dissolved in xylene)

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WPC Graph No.3-Sample 3 Blends + 40WF

Graph No.4-Sample 4 Blend + 30WF

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WPC

Result and Discussion (Table no. And graph no 1 to 8) EVA is a polymeric plasticizer, in addition of that it act as impact modifier. The notched impact strength of pure nylon 6 is about 19 J/m. while the nylon 6-Eva blend possess at a weight ratio 50/50; a notched impact strength of about 266.6 J/m as shown in graph 1. However the compatibilizer maleic anhydride generated bridges between the nylon 6 and EVA components. This major increased in notch impact strength of were obtained as result of compatibilization. For small amount of maleic anhydride, the sample achieved the high notched impact strength of 333.33 J/m as shown in graph 3, which represents a tough behavior. Unnotched impact strength of blend sample no. 1 and 2 shows values 533.3 J/m and 466.6 respectively as shown in graph no. 2 and 4. With increase in wood flour content in blend, impact strength gets reduced. This is because wood flour, which is filler, acts as an impurity in the matrix. Low stress transfer between blend matrix and filler resulting in decrease in impact strength. The result obtained showed strong dependence on percentage porosity along with wood flour content. As it can be seen from the result blend matrix and wood flour have higher porosity than that of blend of nylon 6-EVA. WPCs impact strength is lower than that of blend due to both higher porosity and addition of wood flour which shown as graph no. 5, 6, 7, and 8.

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

Tensile Strength: Table No.09 Result of Tensile strength

Sr.

Tensile

No. Materials Formulation

1.

Tensile

%

Strength

Modulus

Elongation

N/mm2

N/mm2

Nylon 6-EVA Blend 18.014

Strain

1.36

13.24

136

0.714

23.49

71

(xylene) 2.

Nylon 6-EVA Blend 16.776 (non xylene)

3.

Blend + 40WF

16.544

0.145

113.83

14.53

4.

Blend + 30WF

16.508

0.16

98.45

16.76

Figure No.09-Universal Testing Machine

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WPC Tensile Test Sample Formulation 1 Nylon 6-EVA Blend (EVA dissolved in xylene)

Tensile Test Sample formulation 2 Nylon 6-EVA Blend (EVA not dissolved in xylene)

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WPC Tensile Test Sample Formulation 3 Blend+ 40% WF

Tensile Test Sample Formulation 4 Blend+ 30% WF

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WPC Tensile Test Result and Discussion: Nylon 6-EVA blend shows ductile failure. On addition of wood flour the failure mode immediately shifts from ductile to brittle. This is due to limitations of imposed on the molecular movement by the wood flour. Decrease in tensile strength is attributed to poor interfacial adhesion between blend matrix and wood flour. The modulus shows corresponding increase with increase in wood flour content. Increase in modulus is due to the restraining effect of filler on the polymer molecules.



Compressive Strength:

Table No.10-Result of Compressive Strength

Sr. No.

Materials Formulation

Compressive Strength Mpa

1.

Nylon 6-EVA Blend (xylene)

38

2.

Nylon 6-EVA Blend (without xylene)

46

3.

Blend + 40WF

21

4.

Blend + 30WF

22

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WPC

Compression Test Result and Discussion Nylon 6- EVA blends having good compression strength than WPC sample no. 3 and 4 because of wood flour act as a filler. So as increase the wood flour content into the blend; decrease in the compressive strength as shown in graph.

Figure No.10-Compressive tes

5.3 Characterization Test 

Differential Scanning Calorimetry (DSC)

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WPC DSC Test Sample formulation Nylon 6-EVA Blend

DSC Test Sample Formulation 3 Blend+ 40% WF

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WPC DSC Test Sample Formulation 4 Blend+ 30% WF

DSC Result Discussion: The thermal and structural characteristic of WPC‘s made of polymer blends were evaluated by differential scanning calorimetry. Three cycles of heat-cool-heat were applied on the specimens, with a starting temperature of 30°C. The samples were heated up to 250°C, kept at this temperature for 2 minutes and then cooled and heated again at a heating rate of 10°C/min. All DSC traces showed distinct melting and crystallization peaks for the blend of Nylon 6-EVA (melting Tm and crystallization Tc peaks shows in DSC graphs), indicating that two crystallizable components co-exist in the blend and WPC systems. From that we can say Nylon 6 and EVA were immiscible with each other and their blend gave phase separation. Reason behind this, we adding inadequate quantity of Maleic anhydride as compatibilizer or should be chose proper compatibilizer

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CONCLUSION

Composites made of wood and nylon 6-EVA blend have been tested mechanically, physically and thermally to determine the impact of extensive mixing and the introduction of polymer blends on the structure and the macroscopic behavior of these WPC‘s. Brittle materials are characterized by a low ductility and break suddenly, leaving these products potentially more dangerous than ductile materials. The increase in the brittleness is a serious issue that needs overseeing and might interfere with a WPC‘s usefulness. The additional blending action was probably helped the dispersion of the polymers and the wood flour, possibly improving the homogeneity of the blends and insure a better adhesion of the components to one another. This increased adhesion would have developed better stress transfer, thus strengthening the composites. Improved blending could also have eliminated voids and increased the overall water resistance. Finally, the polymer blends did not influence the behavior of the composites, in fact this behavior was strongly linked to the nature of the polymer used. No disadvantage in using blends of polymers appeared during the different tests, should these tests be on the strength of the composites or on their morphology. Using blends of polymers presents many advantages and opportunities that need to be investigated and evaluated during future investigations. Certainly, new applications of WPC‘s might be found with polymer blends and this new area of research needs more specific attention. The processing advantages thermoplastics have, however, present considerable opportunity in direct manufacture of product. Wood flour provides mechanical advantages over fiber and particles, however an effective coupling agent must be used to improve the stress transfer between the wood and thermoplastic component, and wood flour improves thermal stiffness machining and cost properties. The material was compounded into the two roll mill. The compounded material can then be formed using extrusions, compression or injection molding technique. Processing MIT, Pune

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WPC steps play a large role in forming the material structure. Many compounding steps degrade the wood element at enclosed condition. Final material structure has a large influence on the material properties. Continued research is need in the relationship between processing method, material structure and properties.

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WPC

REFERENCES

 Brackley, A. and M. P. Wolcott. 2008. Economic Development – Market for wood composite decking material and impact of local economics. Alaska Wood Tides, Issue No. 7. Pacific Northwest Research Station, USDA FS, Sitka, Alaska.  Evergreen Engineering. 2005. Prospectus: The Opportunity to Manufacture Wood Plastic Composite Products in Louisiana. Project #1655.0, Eugene, OR.  Kim J-W, DP Harper and AM Taylor. 2008. Effect of wood species on water absorption and d urability of wood-plastic composites.  Wood and Fiber Science 40(4):519-531 Klyosov AA. 2007. Wood-Plastic Composites. Wiley-Interscience. 698 pages - ISBN 0470148918  Rowell RM, Sanadi AR, Caulfield DF, and Jacobson RE. Utilization of Natural Fibers in Plastic Composites: Problems and Opportunities. In Lignocellulosic Plastic Composites, 1997.  Us3956541- Structural Member Of Particulate Material And Method Of Making Same  US5518677- Advanced Polymer/Wood Composite Pellet Process  US6117924- Extrusion Of Synthetic Wood Material  US6153293- Extuded Wood Polymer Composite And Method Of Manufacture  US6637213- Cooling Of Extruded And Compression Molded Materials  US6958185- Multilayer Synthetic Wood Component  US3888810- Thermoplastic Resin Composition Including Wood and Fibrous Materials.  www.wpccorp.com (Tokyo, Japan) MIT, Pune

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WPC  A Technology And Review Of Wood Plastic Composites -Michael P. Wolcott And Karl Englund (Washington State University, Pullman, Washington.)  Plastic Material Book By Brydson  Plastic Additives Handbook , Hanser Publication Edited By- R. Gachter And H. Muller  Mechanics Of Composite Materials Edited By Robart M. Jones  Wood Plastic Composite Handbook, A John Wiley & Sons, Inc., Publication Author- Anatole A. Klyosov.  Handbook Of Plastic Testing By Vishu Shah.  Characterization of Highly Filled Wood Flour-PVC Composites: Morphological and Thermal Studies. -D. S. Marathe, P.S.JOSHI  Fibre Reinforced Composite By P.K.Malik

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Profile for VISHAL91

Final wpc project report  

The invention relates to composition including a Blend of Nylon 6-EVA material and wood fiber composite that can be used in the form of line...

Final wpc project report  

The invention relates to composition including a Blend of Nylon 6-EVA material and wood fiber composite that can be used in the form of line...

Profile for vishal91
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