The Effect Of Modified Lignin And Annealing Process On Crystallization Rate And Heat Resistance Of PLA

Poly(lactic acid)(PLA)is a semi crystalline and all biodegradable polymer.It is widely used in many aspects for its good transparency,biocompatibility and physical properties.However,the slow crystallization rate,low crystallinity and poor heat resistance of PLA will seriously restrict the further application of PLA.Therefore,we need to modify the PLA,aiming to speed up the crystallization rate of PLA and improve its heat resistance.Nucleating agents can provide more nucleation sites to obviously accelerate the crystallization rate of PLA.Annealing can improve the crystal structure,the crystallization and the heat resistance of PLA.In this article,a combined method that adding nucleating agent and annealing will be discussed,which is expected that the crystallization rate and heat resistance of PLA can be obviously improved.The paper has some practical and theoretical significance.In this paper,modified lignin(MZS)was used as a nucleating agent for PLA(4032D and 3100HP).The PLA/MZS material was prepared by melt blending,and the effect of modified lignin on the crystallization rate of PLA was studied.The results showed that MZS is an effective nucleating agent for PLA.When the mass fraction of MZS was 1.0%,the nucleating effect of PLA was better.With the addition of MZS,the crystallization time of PLA was obviously shortened,and the crystallization rate was significantly improved.Under the action of MZS as a nucleating agent,PLA still exhibited a faster crystallization rate under the condition of rapid cooling(-45 C/min),and its crystallinity can reach 31%.The annealing treatment of PLA/MZS was carried out.Synergistic effect of nucleating agent and annealing on the crystallization and heat resistance of PLA was studied.The results showed that annealing can improve the crystal structure,the crystallization and the heat resistance of PLA,The crystal form of PLA was a stable alpha crystal.With the increase of annealing temperature,the beta crystal of PLA will be formed.Nucleating agents and annealing can synergistically promote the crystallization and heat resistance of PLA.When the PLA/MZS material was annealed in water,its crystallinity and heat resistance increased significantly at lower annealing temperature and shorter annealing time.