Differential Scanning Calorimetry (DSC) for Testing the Differences between PA6 and PA66 (Nylon)

Modified plastics refer to plastic products that are processed and modified through filling, blending, strengthening, and other methods on the basis of general plastics and engineering plastics, improving their flame retardancy, strength, impact resistance, toughness, and other properties.

PA6 and PA66 (nylon 6 and nylon 66) are important varieties of engineering plastics with strong vitality. Secondly, they achieve high performance after modification. Secondly, the automotive, electrical, telecommunications, electronics, machinery and other industries have increasingly strong requirements for product high performance. The rapid development of related industries has promoted the process of high-performance engineering plastics, making them play an increasingly important role. Nylon is a crystalline polymer. The melting point is obvious and relatively high, with PA6 having a melting point between 215~225 ℃ and PA66 having a melting point between 250~270 ℃; Therefore, nylon needs to be molded at higher temperatures, and the thermal stability of nylon in a molten state is poor and prone to decomposition. Therefore, it is necessary to strictly control the process conditions. The stability of modified plastics is not significantly different in appearance and color. Differential scanning calorimetry can be used to distinguish whether they contain PA6 and PA66, as well as the ratio of these two materials.

1、 DSC testing of PA6 and PA66 in engineering plastics

1. Test material: Nylon (PA) material

2. Measuring instruments:DZ-DSC300 Differential Scanning Calorimeter

3. Testing principle:

Differential scanning calorimetry is a technique for measuring the heat flux difference and temperature or time between a substance and a reference substance under programmed temperature control and a certain flow rate atmosphere. Based on the analysis of the heat flux difference signal, the characteristic temperature and calorimeter parameters of the sample are obtained. Whenever the physical state of a material changes, such as melting, transitioning from one crystalline form to another, or undergoing a chemical reaction, it always absorbs or releases heat, and these changes often only require changing the temperature of the material to occur. DSC measures the relationship between the heat difference and temperature between the sample and reference material under program-controlled temperature.

2、 Setting and selection of experimental parameters

1. Instrument selection

The testing instrument selected for this test is the high-precision DSC300 series from Nanjing Dazhan Instrument. Its advantage is that its sensitivity can reach 0.001 ℃, which can accurately and clearly test the differences in the content of different components of the sample. At the same time, it can be set in multiple temperature stages to achieve heating, constant temperature and cooling, PID intelligent temperature control, bidirectional operation, which is more convenient and fast.

2. Test parameter requirements

2.1 Test parameter settings

Temperature: 300 ℃

Speed: 10 ℃/min

Atmosphere: N2, 50ml/min

2.2 There are three groups of samples tested, some of which are PA6, some are PA6 and PA66 mixture, and some have added other auxiliary materials; By using DZ-DSC300 differential scanning calorimeter to test the differences of products, the quality of the products can be controlled.

2.3 Each sample should be weighed before testing, and after weighing, it should be placed in the testing crucible.

2.4 Test Chart Analysis

In the spectrum of Sample 1, two endothermic peaks are observed, namely PA6 and PA66; The content of PA66 is slightly higher than that of PA6;

In the spectrum of Sample 2, there is an endothermic peak near 158 ℃, indicating the presence of other plastics mixed into the material; The other peak is the peak of PA66; PA66 content is relatively high;

In the spectrum of sample three, there are three peaks and two peaks near 210 ℃, which may be due to some differences in stability between partially recycled materials and PA6 new materials; The third peak is the peak of PA66;

The above data is from the DZ-DSC300 high-precision differential scanning calorimeter test; If the accuracy is low, small peaks of variation may not be captured.