ELIX Vicat Guidelines (CH)

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VICAT TEST Recommendations for improved consistency in measured values

1. Introduction

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2. Report objective

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3. Analysis and results

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a. Effect of injection machine and testing equipment

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b. Effect of drying time

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c. Effect of sample storage time

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d. Effect of heating rate

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4. Conclusions

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VICAT TEST Recommendations for improved consistency in measured values

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VICAT softening point or VICAT hardness is the determination of the softening point for materials which have no definite melting point, such as amorphous polymers. The value is taken as the temperature at which the specimen is penetrated to a depth of 1mm by a flat-ended needle with a 1 mm2 cross-section.

Different loads can be used, depending on the type of VICAT test. Heating rate is another variable that fluctuates depending on the VICAT test values, depending on the type of measuring device used.

Standards for performing the VICAT test are ISO 306 and ASTM D1525. Indeed, the standards recognize a maximum difference of 1% in the measured values, depending on the type of measurement device used. ELIX has observed a higher variation rate due to injection moulding, sample preparation process and the measuring equipment used. The standards also include a repeatability study in order to assess differences detected when measuring samples.

Due to the significant differences observed in the VICAT test in specimens measured by our customers and ELIX quality laboratory, ELIX has performed a study to determine which factors affect the final VICAT value and how those variations can be reduced or avoided in order to increase the consistency of the measured values. The following criteria, present in the ISO 306 standard, are variable for VICAT determination. Thus, changes in these criteria could lead to poor consistency in the measured values: •Representative sample size •Drying time •Sample injection conditions •Time between injection and testing •Measuring equipment •Heating rate / applied load.

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VICAT TEST Recommendations for improved consistency in measured values

In order to detect the influence of the variable criteria already commented, ELIX performed the VICAT measurements following the ISO 306 standard under different conditions.

•Samples were processed in different injection machines with the same processing conditions •Samples were tested in different equipment •Samples were dried over different times •Time lapsed from the manufacturing to the testing of the samples was also studied •Standard measuring methods B50 and B120 were compared

a.

Effect of injection machine and testing equipment.

Two different Arburg 270H injection machines were used to prepare specimens for VICAT property determination. Processing conditions were the same for both machines and set as described in table 1.

Two different measurement devices were used to determine VICAT temperatures from the same supplier: OKO VICAT machine. Clear differences in the measured values are noticeable depending on the moulding machine and measuring device, even when the same manufacturer and model are used.

108

TESTING DEVICE 1

107

TESTING DEVICE 2

106 105 104 103 102 101

VICAT (ºC)

100 99 98

INJ 1

INJ 2

Fig. 1. Influence of testing device and injection machine on VICAT measurements.

VICAT TEST Recommendations for improved consistency in measured values

Fig. 2. ARBURG 27oH

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Fig. 3. OKO VICAT

INJECTION PARAMETERS MASS TEMPERATURE

240 + 5

ºC

HOLDING FIRST PRESSURE

1000

bar

MOULD TEMPERATURE

70 + 3

ºC

HOLDING SECOND PRESSURE

250

bar

INJ. FIRST PRESSURE

1200

bar

CYCLE TIME

34

sec

INJ. SECOND PRESSURE

900

bar

INJ. RATE

30

ccm/S

Table 1. Injection conditions for manufacturing VICAT probes.

b.

Effect of drying time.

Sample specimens were dried in a desiccant hot-air drier at 80ºC and then removed from the drier at different times for VICAT measurements. From Fig. 4 it is clear that a drying time of 4 hours is needed to achieve constant VICAT values.

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VICAT TEST Recommendations for improved consistency in measured values

108 107 106 105 104

VICAT (ºC)

103 102 101

1

2

3

4

5

6

Drying time (h) Fig. 4. Infuence of drying time on VICAT measurements

c.

Effect of sample storage time.

Sample specimens were stored for different times after injection molding and before performing the test. Measured values show that there is a decrease in the softening point of the material until day 8 (192h) and afterwards, the values remain constant. This can be explained by the relaxation process in the sample specimens

108

107

106

105

104

VICAT (ºC)

103

102

101

0

50

100

Time until probes are measured (h) Fig. 5. Infuence of storage time of probes on VICAT measurements

150

200

VICAT TEST Recommendations for improved consistency in measured values

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d.

Effect of heating rate.

The ISO 306 standard stablishes four methods for performing the VICAT measurements, depending on the applied load and heating rates: ISO 306 MEASURING METHODS HEATING RATE (ºC/h)

APPLIED LOAD (N)

A50

50

10

B50

50

50

A120

120

10

B120

120

50

Table 2. ISO 306 measuring methods.

The most widely-used methods in the plastic industry are B50 and B120 and they show differences in the measured values for the same material. Below is a table with some values resulting from measuring ELIX materials present in our portfolio with both methods.

GRADE

B50 (ºC)

B120 (ºC)

GRADE

B50 (ºC)

B120 (ºC)

P2H-AT

98

101

H605

101

103

P2M-AT

98

101

H604

102

104

P2M-V

97

100

HH 3105

103

105

P3H-AT

96

100

HH 3110

108

110

M210TF

95

98

HH 3114

112

114

M203FC

99

101

H801

105

108

M205FC

98

101

Ultra 4105

106

109

P2MC

95

98

Ultra HH4115 HI

113

115

HH P2MC

103

105

PC/ABS 5120

118

120

Ultra HH4115 PG

113

115

PC/ABS 5130

128

130

Table 3. Comparative table of VICAT measuring methods for the ELIX portfolio.

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VICAT TEST Recommendations for improved consistency in measured values

•Injection machine and VICAT measurement equipment play an important role in consistency between VICAT measured values.

•Drying time must be at least 4h at 80ºC in desiccant hot-air driers.

The use of other types of driers may need readjustments in the required time.

•Sample specimens should be tested as soon as they are manufactu red. Storage times longer than 8h may cause differences in the measured values and should not be accepted.

•Due to the variations detected when measuring with different equipment, validation procedures should be carried on in order to establish equivalence rules between measuring devices.

ELIX POLYMERS S.L. / Technical Customer Service