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1 SCOPE

The purpose of this standard operation procedure is to determine the melting point of polymers by differential scanning calorimetry (DSC). This test method is applicable to polymers in granular form (below 60mesh preferred, avoiding grinding if possible) or to any fabricated shape from which appropriate specimens can be cut.

2 PRINCIPLE

      This test method consists of heating or cooling the test material at a controlled rate in a specified purge gas at a controlled flow rate and continuously monitoring with a suitable sensing device the difference in temperature or the difference in heat input between a reference material and a test material due to energy changes in the material. A transition is marked by absorption or release of energy by the specimen resulting in a corresponding endothermic or exothermic peak or baseline shift in the heating or cooling curve.

3 Responsibility

Approval of procedure：Lab supervisor or manager

Performance of procedure：Lab authorized testing staffs

Examination of test result：Lab authorized checked staffs 

4  REFERENCE DOCUMENTS

4.1 ASTM D3418-12 e1Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning Calorimetry.

4.2 ASTM E794-06 (2012) Standard Test Method for Melting and Crystallization Temperatures by Thermal Analysis

4.3 Code of Federal Regulations Title 21

5DEFINITION

5.1 DSC: Differential Scanning Calorimetry

5.2 Teim: melting extrapolated onset temperature, °C

5.3 Tpm: melting peak temperature,° C

5.4 Te: extrapolated onset temperature for fusion, ℃

6 Calibration

6.1 Calibrate the DSC temperature signal using Practice E 967, use two point calibration.

6.1.1 Select two calibration materials, Indium and Lead. Melting temperature see table 1.

Table 1：

6.1.2  Into a clean specimen holder, place a 5mg-8mg weighed amount of calibration material. Load the specimen into the instrument chamber, purge the chamber with dry nitrogen at a flow rate of 50ml/min throughout the experiment.

6.1.3  Heat the calibration material rapidly to 30℃ below the calibration temperature and allow to stabilize.

6.1.4  Heat the calibration material at 10℃/min through the transition until baseline is reestablished above the transition. Record the resulting thermal curve.

6.1.5 From the resultant curve, measure the temperatures for the desired points on the curve, Te retaining all available decimal places.

6.1.6 Using the apparent transition temperature thus obtained. Using the standard temperature values taken from table 1.

7 Sample

7.1 Powdered or Granular Specimens—Avoid grinding if the preliminary thermal cycle is not performed. Grinding or similar techniques for size reduction often introduce thermal effects because of friction or orientation, or both, and thereby change the thermal history of the specimen.

7.2 Molded or Pelleted Specimens—Cut the specimens with a microtome, razor blade, hypodermic punch, paper punch, or cork borer or other appropriate means to appropriate size, in thickness or diameter and length that will best fit the specimen containers and will approximately meet the desired weight in the subsequent procedure.

7.3 Film or Sheet Specimens—For films thicker than 40 μm, see 6.2. For thinner films, cut slivers to fit in the specimen capsules or punch disks, if the circular specimen capsules are used.

8 PROCEDURE

8.1 The purge gas shall be used during testing. The flow rate of the gas shall be the same as used in the calibration (50ml/min).

8.2 Use a specimen mass appropriate for the material to be tested. In most cases a 5mg-8mg specimen mass is satisfactory. Avoid overloading. Weigh the specimen to an accuracy of ±10μg.

8.3 Intimate thermal contact between the pan and specimen is essential for reproducible results. Crimp a metal cover against the pan with the sample sandwiched in between to ensure good heat transfer. Take care to ensure flat pan bottoms.

8.4 Perform and record a preliminary thermal cycle by heating the sample at a rate of 10°C/min from at least 50°C below to 30°C above the melting temperature.

8.5 Measure the temperatures for the desired points on the preliminary heating cycle: Teim and Tpm. See Fig.1

                                     Fig.1

9Result

9.1 Results of the melting point measurements using the temperature parameters cited in Fig. 1. Tpm is commonly used as single characteristic temperatures for melting point of semicrystalline polymers. Because Tpm of PA66 exceeds melting point range in FDA, Teim is commonly used as melting point of PA66.

9.2 Melting point range of common semicrystalline polymers in FDA see table 2.

Table 2:

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