The Preparation, Structure And Property Of Anti-aging Ternary Co-condensation Transparent Polyamide

Transparent polyamide is a kind of special polyamide that doesn’t crystallization or has a very slowly crystallization speed. It not only has excellent performance which the general polyamide has, but also has advantages such as excellent transparency, good dimension stability, good environmental stress cracking, anti wear property and so on. So it has been widely used in the electric mechanical parts area and so on.The overseas development of transparent polyamide always keeps ahead. The domestic development of transparent polyamide starts late, so many demanded transparent polyamides have to be imported.Currently the semi-aromatic transparent polyamide (SATPA) in the market is developed by the materials science college of Zhengzhou University and Pingdingshan Hualun Plastic Co. Ltd. Although SATPA series transparent polyamide material has excellent transparency and good mechanical properties, but there are deficiencies in its heat resistance and toughness, at the same time it has single trademark which can not meet the needs of a variety of molding and then limits its application. So our laboratory is committed to the development of SATPA product,deeply focus on improving the viscous flow temperature and impact strength, some progress has been made, but the samples has insufficiency in transparency and the anti-aging properties. The main purpose of this subject is to develop a serie of anti-aging microcrystalline structure transparent polyamide with excellent transparency, heat resistance and impact strength.This thesis uses aromatic and aliphatic monomers, monomer salt, though high-pressure reaction vessel, adding nucleating agents and antioxidants, adopt co-condensation synthesis, a series of transparent polyamide have been condensated. Through the study we find:(1) The optimal synthesis of transparent polyamide conditions show as below: prepolymerization temperature is180℃, prepolymerization time is 2 hours long, slow deflation duration is 4 hours long, the polymerization temperature is 260-270℃, the polymerization time is 3 hours long. The intrinsic viscosity number of the preparation transparent polyamide is 70.0ml/g.(2) The X-ray diffraction analysis and polarizing microscopy show that:after adding nucleating agent, the transparent polyamide crystallization to some extent, the grain size is relatively small, crystallization is not perfect.(3) Thermal analysis and Dynamic mechanical analysis show that:after the addition of nucleating agents and antioxidants, the Tg of transparent polyamide is up to 70℃, the transparent polyamide has good heat resistance. The thermal degradation process of the transparent polyamide is one step degradation, thermal degradation temperature are more than 444.9℃, so it has good thermal stability.(4) Dynamic mechanical analysis shows that the transparent polyamide has three basic relaxation changes in the sample peak. As the frequency increases, the transition temperature peaks are shifted to high temperature. At-125℃transparent polyamide has a obvious low-temperature loss peak, then we can guess it has good low temperature toughness.(5) The transparent polyamide can be molded by injection. Mechanical property tests show that the tensile strength of transparent polyamide is up to 78MPa, breaking elongation is up to 125%, bending strength can reach 70MPa, notched impact strength can achieve 9.5kJ/m2.Its’mechanical properties are not improved after treated in water. After anneal treatment, the mechanical properties of transparent polyamide are improved. The tensile strength is improved from 69MPa to 74.4MPa, breaking elongation increases from 160% to 175%, flexural modulus increases from 2240MPa to 2300MPa, notched impact strength increases from 5.7kJ/m2 to 5.9kJ/m2.(6) The water absorption of the preparation transparent polyamide is relatively small. The water absorption of transparent is only0.40% after soaking in water at 23℃for 24 hours. The higher the temperature of water, the more the water absorption of the sample. The sample size has a little change after water absorption, so it has good dimensional stability.(7) When there is not antioxidants in the transparent polyamide, in the polymerization process, the transparent polyamide materials change yellow easily, its’ light transmission rate is only about 60%; by adding antioxidants, in the polymerization process, the transparent polyamide materials change yellow difficultly, the light transmission rate of transparent polyamide achieves 86%, it has excellent transparency.