Study On The Crystallization Behavior And Properties Of Poly(Lactic Acid)/Thermoplastic Poly(Propylene Carbonate) Polyurethane Blends

In this paper,the biodegradable thermoplastic poly?propylene carbonate?polyurethane?PPCU?was used to tougheningpoly?lactic acid??PLA?.The PLA/PPCU blends and PLA/PPCU/ACR blends were obtained by the melt blending method,respectively.The crystal properties,mechanical,thermal properties and enzyme degradation performanceof the two kinds of materials were systematically studied.The toughening mechanism and the effect on crystallization on properties of the materials were analyzed.The results show that:1.Mechanical test showed that the impact strength and elongation at break of PLA/PPCU blends were remarkably higher than those of pure PLA.The impact strength was enhanced from 4.78 kJ/m²for pure PLA to 102.8 kJ/m²for the 50/50 PLA/PPCU blend.The impact testing showed obvious ductile fracture when PLA was blended with PPCU.It was found that the PLA matrix showed large plastic deformation?shear yielding?in the blend subjected the impact tests,which was an important energy-dissipation process and led to a toughened polymer blend.PPCU could act as impact modifier of PLA.The maximum improvement in cold crystallization temperature(T_cc)value was observed for PLA/PPCU blends where T_ccc was increased from 113 ^oC to 128 ^oC.PPCU enhanced the ability of crystallization for PLA,but the function of nucleating was weaken when the content of PPCU was further increased.The incorporation of PPCU did not alter the crystal structure of the PLA matrix.The PLA/PPCU blends were high strength and high toughness entirely biodegradable materials,which gave important security for manufacturing and application.2.PLA/PPCU/ACR blends were studied on the crystallization behavior and properties.Results showed that the addition of ACR can obviously improve the crystallinity of the blend materials,and the crystallinity of materials were improved obviously.In the process of heating up,the double melting peak could can seen.ACR promoted to the formation of?'crystal form after blending PLA with 3wt%ACR.Thermo-gravimetric data showed that the thermal stability of blends was improved obviously after mixing of ACR and the temperature of maximum weight loss rate(T_max)was improved above 20°C.Rheological test showed that the viscosity of the material was increased obviously after blending ACR with the PLA/PPCU blends.But the effects of ACR were weaken with the further increasing of frequency on the viscosity.Mechanical test showed that the impact strength of PLA/PPCU/ACR blends was increased nearly 20 kJ/m² when the content of ACR was3wt%.The tensile strength of the materials was improved with the further increase of ACR,but the elongation at break of blends was decreased.