Study On Crystallization Kinetics And Application Of CBT/PA6 Blends

As the most widely used engineering plastics,nylon has the characteristics of high mechanical strength,good elasticity,toughness,wear resistance,oil resistance and good chemical stability,which is widely used in automotive,electronic,electrical appliances,aerospace and other fields.Because nylon has the properties of very strong absorbent,water absorption,the reduce of elastic modulus,impact strength after absorption and worse size stability,its stability and mechanical properties of the product size are not very good.Also,its high viscosity,high processing temperature,poor process performance and other factors limit its scope of application.A large number of literatures show that grafting,copolymerization or blending modification(adding inorganic particles or small molecule oligomer to nylon)can improve the liquidity.The advantages of simple operation and low cost of the blending modification have been highly concerned by people.CBT(cyclic butylene terephthalate)is a ring of thermoplastic materials,degree of polymerization of n=2~6.Its viscosity in the molten state is very low and the wetting ability is very strong.It has good compatibility with a variety of polymer materials.This paper takes CBT as the additive and CBT/PA6 blends are prepared by solution blending method.The effect of CBT on PA6 in crystal morphology,crystallization kinetics and thermal stability was studied.The macro kinetics of CBT/PA6 process was analysed.Then get the basic data on the best processing conditions of nylon.The composite material which reinforced by carbon fiber and based CBT/PA6 was produced.The interlayer shear strength and bending strength with the change of CBT content was studied.The viscosity analysis results show that CBT can quickly decrease melt viscosity of PA6 to 50 Pa.s.The viscosity increased with CBT content decreased.However,the decreasing trend is not obvious when CBT content exceeds 1%.This paper uses the DSC method to study the effect of the CBT on the crystallization kinetics of PA6.The result shows as follows: First,in the procrss of isothermal crystallization,the Avrami index of n decreased,the crystallization rate constant K and the crystallization rate of G becomes large,t1/2 and tmax decreased when adding CBT in PA6.The crystallization rate constant shows that CBT can contribute to the crystallization rate of PA6.Second,in the procrss of non isothermal crystallization,the CBT can reduce the Jeziorny equation n indexand increase the crystallization rate constant Zc;lg? and lgt with good linear relationship processed by Mo equation.F(t)value of the system decreased quickly after putting the CBT.It shows that under the same conditions,the CBT/PA6 system crystallizes more rapidly than PA6 system.Macro kinetic shows that during the machining process of a certain shape and thickness PA6 material,the internal temperature and relative crystallinity of the existence of spatial distribution,because of the crystallization exothermic,internal heat is not timely,produce heat shock,resulting in uneven temperature distribution,the PA6 should select the smaller cooling rate.Refering to the dynamics research above,this paper uses CBT/PA6 as substrate in the preparation of carbon fiber reinforced nylon composite material and the interlaminar shear strength and the bending strength was tested.The results show that the interlaminar shear strength of composite value is 47.61 MPa ~70.99 MPa and flexural and flexural strength value is 437.09 MPa ~732.69 MPa.