| Polylactic acid(PLA)is a biodegradable and bio-based aliphatic polyester.It has received extensive attention in recent years due to its great environmental and economic value.And it has a great impact on the plastics industry.However,the inherent brittleness characteristics of PLA polylactic acid and its high production costs and low melt strength have been the major limitation for its use in variety of application.In this paper,first of all,the biodegradable materials polybutylene terephthalate(PBAT)as a toughening agent to improve the toughness of PLA was added.And in-situ compatibilized PLA/PBAT blends were prepared by using dicumyl peroxide(DCP)as a free radical initiator.Then,addition of corn starch which was modified by aluminum-zirconium coupling agent to decrease the price of PLA/PBAT blends.The impact of the content of corn starch on the properties of PLA/PBAT composite materials were investigated.Finally.And the effect of DCP on the melt strength and mechanical properties of PLA/PBAT/corn starch composite materials were studied.The results show that the PBAT domains are embedded loosely in the PLA matrix with large domain size,and the interface are distinguishable.The domain size becomes uniform and smaller after addition of DCP,demonstrating the compatibility of PLA and PBAT is improved.The shear thinning behavior becomes more and more pronounced with the DCP content.Mechanical properties testing results showed that DCP could improve the toughness of PLA/PBAT composites.The notched impact toughness of PLA/PBAT composites increases from 4.9KJ/m2 to 8.0KJ/m2 when the content of DCP was 0.4wt%.The crystallinity of PLA was decreased due to the increase of melt viscosity.The thermal stability and the number of spherulites are maximum when the content of DCP was 0.4 wt%.For PLA/PBAT/corn starch composite materials,starch particles distributed evenly in PLA/PBAT matrix in the presence of aluminum zirconate coupling agent,and the compatibility among starch and PLA/PBAT was improved.The mechanical properties and the heat-resistant shear of the blends were decreased with the corn starch content.In order to reduce the costs but keep the strength of the composites the content of corn starch should not more than 20wt%.It was found the thermal stability of the blends were decreased with the introduction of corn starch.It has a significantly effect of heat treatment condition on the Vicat softening point(Tw)of the PLA/PBAT/corn starch composite materials.Tw of the composites with 20wt% corn starch increases from 56? to 81? after annealed at 100? for 10 min implying that the heat resistance was significantly improved,but the crystal form of PLA has not changed.The mechanical properties of PLA/PBAT/corn starch composite materials was improved in the presence of DCP due to the compatibility among corn starch and PLA/PBAT matrix was increased.When the content of DCP was 0.4wt%,the notched impact strength of the composites was maximum,ditto the elongation at break of the composites.Storage modulus(G')and complex viscosity(?*)were increased with DCP content,ditto the equilibrium temperature and the equilibrium torque.Meanwhile the MFR gradually declined with the DCP content.All the above shows that the melt strength of the blends increased with the DCP content.Moreover,the cold crystallization temperature of PLA shifted to higher temperature as the DCP content increased. |
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