Flash DSC Characterization Of Crystallization Kinetics Of Nylon-6 And Its Copolymers

There are many kinds of nylon.In this paper,the most representative nylon 6 is the main research object.The comparative methods are used to classify the samples to explore the crystallization kinetics of nylon 6 and its copolymers.With the development of polymer characterization technology,there are more and more methods to study the crystallization kinetics of materials.Among them,the ultra-fast temperature rise and fall rate of Flash DSC can prevent the structural changes of materials during the measurement process and ensure the reliability of experimental results.In Chapter 1,we mainly explained the crystallization kinetics mechanism of polymers.Since this topic is mainly for the characterization of nylon materials,this chapter also introduces the structure and properties of nylon,the composition and crystal structure of nylon.At the end of the chapter,the research results of the thermodynamics and dynamic properties of nylon and the main research contents of this paper are presented.In Chapter 2,we introduced the development process of the experimental instrument Flash DSC used by our group,the advantages of the instrument and the method of measuring the crystallization kinetics by using Flash DSC.In Chapter 3,we compared the isothermal experiments of nylon 6 with polyketone.By comparison,it is found that when the two samples are in the low temperature zone,the hydrogen bonding effect of the nylon in the molecule reduces the diffusion ability of the molecular chain,and the diffusion coefficient is small at low temperature,resulting in a lower crystallization rate.In the high temperature zone,the strong hydrogen bonding in the nylon 6 molecule is higher than that of the polyketone,which reduces the free energy of the nuclear surface and greatly promotes the nucleation ability of the polymer crystal.As the temperature increases,the crystallinity of nylon 6 in the high temperature region(T>140?)is greater than that of the polyketone.In Chapter 4,we used Flash DSC to isothermally anneal nylon 6,nylon 66 and copolymerized nylon 6/66 in the same temperature range,and obtained three crystallization kinetic curves.The crystallization kinetics of nylon 66 is a "double down" type,probably due to changes in the nucleation mechanism within the molecule over different temperature ranges.Nevertheless,in the wide range of 100?200?,the crystallization rate of nylon 66 is always higher than that of nylon 6,indicating that the hydrogen bond density has a certain influence on the intramolecular nucleation rate.As the hydrogen bond density increases,the nylon crystallization rate becomes faster.The copolymerized nylon 6/66 synthesized by the two monomers is a random copolymer,and since the molecular chain formation by copolymerization is low,the crystallization rate of the copolymerized nylon is much smaller than that of the monomeric polymer.In Chapter 5,we classified the results of the nylon isothermal experiments in this paper.After comparing the isothermal experiments of the above nylon samples,the crystallization kinetics of nylon and its copolymers were analyzed,and the progress of polymer crystallization mechanism was promoted from the perspective of nylon.