Crystallization Kinetics And Toughening Modification Of Graphene Oxide/Nylon 6 Composites

Nylon 6 is an engineering material widely used in modern society.It has many excellent physical and chemical properties,such as high mechanical strength and corrosion resistance.So it can be applied in the fields of automobiles,electrics,electronics,and other fields.However,there are also some shortcomings,such as high water absorption and poor low temperature toughness.As a kind of crystalline polymer material,nylon has a close relationship between its structure and properties.The crystal structure and crystallization behavior have an important influence on the properties of crystalline polymers.The grain size,crystal type and crystal perfection degree are related to the mechanics of the material.Through the study of the crystallization kinetics of the polymer,the correspondence between the crystallization process of the polymer and the crystallization principle can be found,which has far-reaching significance for exploring the relationship between the structure and properties of the polymer material.(1)In this paper,we compared the non-isothermal crystallization behavior of graphene oxide/nylon 6 composites prepared by in-situ polymerization and solution blending at different cooling rates.Ozawa equation,Mo zhishen equation and new method of least squares fitting a quadratic curve were used to study the non-isothermal crystallization kinetics.Using the Ozawa equation for linear simulation,the fitted curve was poorly correlated.Therefore,based on this,a new data processing method that comprehensively considered the effect of cooling rate on crystallization performance was proposed.Mo zhishen model could fit the curve better.The results showed that pure PA6 had a faster crystallization rate than the graphene oxide/nylon 6 composites,and the solution blending could complete the entire crystallization process faster than in-situ polymerization.The Kissinger equation was used to study the crystallization activation energy of the material.It was found that the crystallization activation energy of the composites system was higher than that of pure nylon,and the crystallization activation energy of the composite prepared by solution blending method was lower than that of the in-situ polymerization.(2)The low content graphene oxide/nylon 6 composites were prepared by solution blending method,and the effects of different graphene oxide contents on the non-isothermal crystallization behavior of the composite system at different cooling rates were studied.Using Ozawa equation,least square method and Mo zhishen equation to study the non-isothermal crystallization kinetics of the composite system.It was found that when the graphene oxide content was 0.3wt%,the composite system had the fastest crystallization rate,and when the graphene oxide content was greater than 0.3wt%,the crystallization rate was gradually lowered,because the addition of graphene oxide hindered the regular alignment of the matrix molecular segments,thereby suppressing the crystallization process.(3)The 0.2wt% graphene oxide/nylon 6 composite prepared by in-situ polymerization had poor toughness,so we used elastomer ethylene vinyl acetate grafted maleic anhydride(EVA-g-MAH)and rigid polymerization polycarbonate(PC)to toughen.It was found that when 10 phr EVA-g-MAH and 5 phr PC were synergistically modified,the toughness of the composite was improved greatly,the elongation at break was increased by 10 times,the impact strength was improved nearly 3 times,and the material had the best overall performance.