Study On Structure And Performance Of Wollastonite Filled PLA/PBAT Blend System

Polylactic acid(PLA)is a kind of aliphatic polyester material that has been studied more deeply and has a higher degree of industrialization due to its biodegradability.However,PLA has been restricted its application and promotion owing to its own high brittleness,low degradation rate,and poor heat resistance.Therefore,it is important to solve the deficiencies of PLA.According to existing research,there are three ways to modify PLA to improve its performance,i.e.chemical modification,physical modification and physical-chemical cooperative modification.Specifically,Poly(butyleneadipate-co-terephthalate)(PBAT)which has been produced by random copolymerization of butadiene adipate(PBA)and butylene terephthalate(PBT)esters is widely used to modify PLA because of its high elongation at break,high impact strength and biodegradability.In recent years,PLA-based composite materials that has been suitable for different fields were developed by researchers.But its at a higher manufacturing cost and mechanical strength loss,so it has certain limitations.Thus,we propose to use wollastonite to fill the modified PLA/PBAT blend system to reduce production costs and improve its comprehensive performance base on previous work.Subsequently,The effect of wollastonite on the structure and properties of PLA/PBAT composites has b een systematically studied.The specific work content of this paper is as follows:(1)The effect of chain extender Joncryl ADR 4380 on the structure and performance of PLA/PBAT(60/40)blending system was studied.The results show that the chain extender Joncryl ADR 4380 has a significant effect on improving the compatibility of the PLA/PBAT blend system.The principle of compatibilization is to use hydroxyl or carboxyl groups in PLA and PBAT to react with epoxy groups to form a branched molecular structure,thus acting as a bridge between PLA and PBAT phases and improving compatibility.With the addition of the chain extender,the lengths of the PLA and PBAT segments are extended,and the movement of the segments is hindered,so that the glass transition peak of PLA gradually moves to a high temperature.As the amount of Joncryl ADR 4380 increases,the crystallinity o f PLA in the PLA/PBAT blend gradually decreases.This is because chain extensio n interferes with the crystallization process,resulting in a large number of end groups and branches forming imperfect crystallites.These crystallites limit PLA crystallization.Due to the addition of chain extender,the entanglement of th e molecular chains in the PLA/PBAT blend is enhanced,so that the storage modulus and loss modulus of the PLA/PBAT blend gradually increase as the content of the compatibilizer increases.The mechanical property test shows that after the introduction of chain extender,the tensile strength and impact strength of the PLA/PBAT blend are significantly improved,and the maximum is at 2.4wt%.(2)Using Joncryl ADR 4380 as a compatibilizer,using wollastonite as a filler reinforcement material,PLA/PBAT/wollastonite composite materials were prepared by melt blending,and the effect of wollastonite on the properties and structure o f PLA/PBAT composites was also studied.The results show that wollastonite is physically dispersed in PLA/PBAT composites,and no obvious chemical bonding occurs between it and PLA/PBAT matrix.Wollastonite is wea kly bound to PLA/PBAT matrix,and with the increase of wollastonite content,wollastonite gradually aggregates.With the increase of the amount of wollastonite,the crystallinity of PLA showed a trend of increasing first and then decreasing,and the melti ng peak of PLA moved towards the high temperature direction.After the addition of wollastonite,the tensile strength and impact strength of the PLA/PBAT composite material were slightly improved,and reached the maximum when adding 1wt%wollastonite.(3)The silane coupling agents KH550 and KH570 were selected as the surfactants of wollastonite,and the modified wollastonite GY4000-KH550 and GY4000-KH570 were prepared through the grafting reaction.Then,with the coating rate as the index,the modification conditions were systematically investigated and optimized.The results show that the best conditions for the modification effect of KH550 are:the mass ratio of KH550 to wollastonite is 2.5,the reaction time is 18 h,and the reaction temperature is 40~oC.Under the best conditions:the coverage o f KH550 on the surface of modified wollastonite is 15.29%.In addition,the conditions for the best modification effect of KH570 are:the mass ratio of KH570 to wollastonite is 3.5,the reaction time is 20 h,and t he reaction temperature is 40~oC.Under the best conditions,the coating ratio of the modified wollast onite surface KH570 is 16.85%.(4)Using modified wollastonite GY4000-KH550 and GY4000-KH570 as filler materials,PLA/PBAT/modified wollastonite composite materials were prepared by melt blending,and the enhancement effects of the two modified wollastonite were studied.The results show that the modified wollastonite GY4000-KH550,GY4000-KH570 can enhance the mechanical properties of PLA/PBAT composite materials,and when the addition amount is 1wt%,the mechanical properties of the composite materials with modified wollastonite GY4000-KH570 and GY4000-KH550are better than those with wollastonite GY4000.Compared with GY4000-KH550,the bond between GY4000-KH570 and PLA/PBAT matrix is tighter and the dispersion is more uniform,so it shows better enhancement than GY4000-KH550.With the addition of modified wollastonite,the crystallinity of PLA/PBAT composites showed a trend of increasing first and then decreasing,and GY4000-KH570 was better than GY4000-KH550 in improving PLA crystallization ability.