Multiple Copolycondensation Preparation, Structure And Properties Of Transparent Polyamide

To fulfill the needs of transparent polyamide and solve the problem of import, a new type of semi-aromatic transparent polyamide (SATPA for short) has been developed by College of Material Science and Engineering of Zhengzhou University cooperating with Pingdingshan HuaLun Plastics Co. Ltd. SATPA has excellent transparency and mechanical properties, but compared with foreign equivalence it also has some shortcomings. Its fallbacks include weak impact strength, small molecular weight, single product grade, and so on. Therefore, it is difficult to satisfy the needs of different molding process and high toughness transparent polyamide products.In order to improve the impact strength of SATPA, enhance its mechanical properties and widen its practical range. This project makes a series of new type transparent polyamides by using several aromatic diamine monomers and several aliphatic dicarboxylic acid monomers as raw materials, using self-made series of semi-aromatic amide salts and long carbon chain aliphatic amide salts for the first time, and by means of water-medium-copolycondensation with a high-pressure reactor. In this paper we will focus on the formula of transparent polyamide, research the preparation condition, and characterize transparent polyamide with many methods, which include structure analysis, thermal behavior analysis, mechanical properties measurement, etc. The solutions are as fallows:(1) Synthesis PA6T and PA6I by means of water-medium-copolycondensation. The results show that: we can obtain high degree polymerization PA6T and 6I respectively by making 6T salt and 6I salt at the condition of pH 7.5 and pH 7.7.(2) Study on the formula of transparent polyamide and the results show that: When 6T salt and 6I salt is binary copolycondensation, if the contents of 6I salt is over 65%, transparent polyamide can be made; when 6I salt and 610 salt is binary copolycondensation, if content 6I salt is more than 30%, transparent polyamide can also be made; when 6T salt and 610 salt is binary copolycondensation, no matter what the ratio of copolymerization, transparent polyamide cannot be made. A series of ternary co-condensation transparent polyamide were prepared by adjusting the ratio of salts and they could suitable for many different fields.(3) Study on the condition of production of transparent polyamide and a reasonable condition is obtain. The results show that: When the prepolycondensation temperature is between 180℃and 210℃, the time for the prepolycondensation is about three hours, slow discharge time is 2.5 to 3 hours, continue polymerization temperature is 260℃to 270℃, polymerization time is 2.5 to 3.5 hours, we can produce semi-aromatic polyamide with relative viscosity of 2.4 to 2.5.(4) Analysis on infrared spectral show that multi-co-condensation polyamide is a sort of semi-aromatic transparent polyamide; analysis on X-ray diffraction and polarized light microscopy show that, multiple-copolycondensation transparent polyamide is non-crystalline polyamide(5) Analysis on DSC shows that: the glass transition temperature of ternary copolycondensation transparent polyamide is between 40℃and 80℃; from T1 to T5, the glass transition temperature is 42℃, 47℃, 55℃, 69℃, 70℃. This results in line with the DMA analysis. It shows that the transparent polyamide has good heat resistance.(6) Analysis on TG shows that: the thermal degradation process is one-step decomposition; the degradation temperature is over 440℃. This shows that the produced transparent polyamide has excellent thermal stability.(7) Ternary copolycondensation transparent polyamide could smoothly shaping by injection molding process and we obtain a better molding process condition by comparing with samples. Test on mechanical properties shows that: the tensile strength of M series transparent polyamide can reach to above 59MPa, the flexural strength can achieve over 58MPa, the flexural modulus keeps more than 1760MPa, the elongation at break can achieve to more than 150%, and Izod notched impact strength can achieve to 7.9kJ/m~2. The result shows that transparent polyamides have excellent impact strength and comprehensive mechanical properties.(8) Comparing with digital photographs of other polyamide, the result shows that: The injection molding test strips have better transparency at common molding conditions.