| Polylactic acid(PLA)is the most active and fastest-growing biodegradable polymer material developed and researched in recent years.A large number of research scholars have done a lot of research work on the problems of poor toughness,poor heat resistance,and low crystallization rate through some methods such as grafting,copolymerization and blending modification.PBAT not only has good ductility and elongation at break,but also has good heat resistance and impact properties.It is often used to improve the mechanical properties of PLA.In order to obtain PLA-based blends or composites with excellent overall performance and relatively low cost,based on previous work,this paper makes out the idea of using fiberglass-reinforced PLA/PBAT blends to control the strength and toughness of PLA.Characterize and study the structure and properties of PLA/PBAT/glass fiber composites.Based on this,this paper has done the following work:(1)The effects were studied that chopped glass fiber treated by two kinds of coupling agents(KH550,KH570)on the structure and properties of PLA/PBAT blends.The results have shown that:glass fiber has a significant reinforcing effect.Through compositing fiberglass,PLA/PBAT blends tensile strength and impact strength are significantly improved.GF550 has good compatibility with PLA/PBAT matrix and can be well dispersed in the matrix,so it shows superior to GF570 reinforcement.The addition of glass fiber has little effect on the Tg and thermal stability of PLA/PBAT blends.The degree of crystallinity shows a slight decrease with the increase of GF addition.(2)The effects of annealing process on mechanical properties and crystallization properties of PLA/PBAT/GF550 composites were studied.The results show that the tensile strength,bending strength and impact strength of GF550-25%composites increase first and then decrease with annealing temperature increasing.When the temperature is 90?,the tensile and bending strengths are increased by 35.5%and 21.5%,respectively,compared with the unannealed samples.Its crystallinity increase first and then tend to be stable.The effects of annealing time on the properties of the sample was studied under constant annealing at 90?.The results show that when the annealing time reaches lOmin,the tensile strength,bending strength and impact strength reach the peak,which improved by 27.3%,28.9%and 30.7%than the unannealed samples respectively.The cold crystallization temperature decreases,and the crystallinity increases first then slightly lower with annealing time prolongs.The samples annealed are all higher than the unannealed specimens at 90? for 10 minutes.(3)The effects were studied that tensile deformation on the structure and properties of PLA/PBAT/GF550 composites.The PLA/PBAT/GF550 samples were tensiled at 50?,60? and 70?,respectively.The results showed that at 60? and 70? the samples with 20%glass fiber content showed large deformation(deformation quantity>460%).The tensile strength increases continuously with the increase of the stretching rate that under 100 mm/min.The microstructure evolution of GF550-20%composites was studied at 60? and 50mm/min.The sample yielded at a strain of about 30%,and strain hardening occurred above the strain of 80%.XRD results showed that the crystallinity of the sample gradually increased with the increase of deformation.Under the conditions of large deformation,a series of processes such as disentanglement,orientation and recrystallization of the molecular chains induce a new crystalline structure. |
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