Preparation And Properties Of Poly (Lactic Acid)(PLA)/biodegradable Polyester Elastomer Particles Composites

Poly(lactic acid)(PLA) has attracted wide attention due to high strength,good biocompatibility and biodegradability. However, its brittleness and poor toughness limit its application in more field. Blending PLA with some elastomer to prepare the PLA composites with high toughness has become the most common and effective methods. Unfortunately, the elastomers do not has the biodegradation. How to prepare the poly(lactic acid)(PLA) composites with high strength and toughness while not sacrificing the biodegradability and compatibility is an urgent project in polymer field. In this article, the biodegradable polyester elastomer particles and the PLA/biodegradable polyester elastomer particles composites materials were prepared.Moreover, we aslo studied the mechanical properties, degradation properties and crystallization of the PLA composites.1. Preparation of the biodegradable polyester elastomer particles. Two kinds of aliphatic unsaturated polyesters with different repeating units are synthesized by melt polycondensation with 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, itaconic acid, fumaric acid, succinic acid and sebacic acid monomers, followed with emulsification, radiation crosslinking and spray drying, then the biodegradable polyester elastomer particles with glass transition temperature(Tg) of-54.3 oC and-44.8 oC respectively are prepared.2. Preparation and characterization of the PLA/biodegradable polyester elastomer particles composites. PLA/biodegradable polyester elastomer particles composites were prepared through melt blending.Mechanical properties of the PLA composites. The biodegradable polyester elastomer particles can significantly improve the toughness of PLA composites.Compared with the elongation at break of pure PLA(1.3 %), the PLA composites containing 10 wt% biodegradable polyester elastomer particles are increased to 31.7%and 28.6 %, respectively. Furthermore, the fracture surface of the impact and tensile PLA composites exhibit obvious roughness and plastic deformation with a large number of craze and microvoids.Crystallization property of the PLA composites. The biodegradable polyester elastomer particles with smaller size and lower Tg acts as a nucleating agent, which shorten remarkably the half crystallization time of the modified PLA, and accelerated the crystallization rate and increased the crystallization speed. When the content of biodegradable polyester elastomer particles is 8 wt%, the crystallization rate constant of the PLA composite is nearly twice as large as the pure PLA. And the half crystallization time is shortened from 12.07 min to 7.11 min. The biodegradable polyester elastomer particles with larger size and high Tg have little effect on the crystallization rate of PLA. The diffraction peak of(200)/(110) crystal plane of the PLA modified by two kinds of biodegradable polyester elastomer particles move to low 2θ, which prompting the formation of α’ crystal.Degradability of the PLA composites. The degradability of PLA composites are affected by the lipase, degeradation period, p H value of environment and the loading of biodegradable polyester elastomer particles in PLA composites. The degradation rate of PLA composites can be promoted by lipase and increased with lipase concentration increasing. In neutral phosphate buffer with 5 g/L lipase, the mass loss rates of two kinds of PLA composites containing 10 wt% biodegradable polyester elastomer particles are increased to 3.2 % and 2.3 %, respectively in 10 days, which are 2.4 and 1.7 times than that of pure PLA. The effect of p H values on the degradation rate of PLA composites is as follows: p H=6.86 <p H=1 <p H=13. Compared with the soil degradation mass loss rate of pure PLA(0.31 %), two kinds of PLA composites containing 10 wt% biodegradable polyester elastomer particles are increased to 1.44 %and 0.59 %, respectively, which are increased 3.65 and 0.9 times.