Study On The Condensed State Structure Regulation And High-performance Modification Of Polyamide 6

Polyamide 6(PA6)is one of the most widely used engineering plastics.It has the advantages of good mechanical properties,wear resistance,oil resistance and solvent resistance.However,the amide groups of PA6 makes it have strong water absorption,and the material swells due to water uptake,so that its gas barrier and moisture barrier properties are drastically reduced,and its strength and dimensional stability are also deeply affected.Therefore,how to reduce the water absorption of PA6,on the basis of maintaining or minimizing the loss of thermal and mechanical properties of itself,is a problem that is closely related to people and urgently needs to be solved.In this work.The interaction between a series of organic and inorganic nanofillers and PA6 and its influence on the condensed state structure of PA6 matrix were studied.The results show that the performance of PA6 was improved,and the effect of structure on properties was well discussed.Main work is as follows:In the first part,two nano-CaCO3 with different functional groups on the surface were selected,nano-CaCO3 with carboxyl group on surface(mCC)and nano-CaCO3 treated with stearic acid(nCC).The functional groups on the surface of nanofillers were studied for fillers and PA6.The influence of the matrix interaction,the influence of different fillers on the crystallization behavior,spherulite morphology,mechanical properties and water absorption properties of PA6 have been studied.The result reveals that mCC has a stronger interaction with PA6 matrix than nCC,and mCC can significantly increase the crystallinity of PA6.On the one hand,the hydrogen bonding between mCC and PA6 reduces the probability of bonding with water.On the other hand,the higher crystallinity is conducive to hindering the penetration of water molecules,so mCC greatly reduces the water absorption of PA6.In addition,the tensile strength and toughness of PA6 nanocomposites were improved when mCC content is between 0.05%and 1.0%;while nCC increased the strength of PA6 to a certain extent,but its toughness was reduced.For PA6/apige blends,the morphology shows two-phase structure and the disperse phase(apigenin)is uniformly dispersed.When the apigenin content is 0.05%～0.5%,heterogeneous nucleation is dominant,the non-isothermal crystallization is accelerated,the melting point increases,and the spherulite size is small;during the isothermal crystallization,the y-form crystal converses to a,the water absorption rate of PA6 has a decrease from 12%to 24%,and surface water contact angles increase ranged from.6.5%to 13.7%The addition of apigenin increases tensile strength and modulus of PA6,and PA6 blends showed ductile fracture.With 0.05%to 1.0%apigenin,the elongation at break remained above 62%of that of neat PA6.The third part studies the modification of PA6 by two organic phosphate nucleating agents(NA-21,NA-11)and a sorbitol derivative nucleating agent(TM6).The nucleation effect of NA-11 is not obvious.0.05%NA-21 and 0.05%,0.1%TM6 contribute to the PA6 nuclei of crystallization,increase the crystallization rate,reduce the spherulite size;they can reduce water absorption of PA6.All of three nucleating agents can increase the tensile strength and elastic modulus of the PA6 blends.When the nucleating agent is added in the range of 0.05%to 0.5%,the elongation at break of the PA6 blends can be maintained at more than 60%of that of neat PA6.