Study On Crystallization Behavior And Rheological Properties Of PLA/LMPA6 Composite System

Poly lactic acid(PLA) has been synthesized by ring-opening polymerization of lactide with lactic acid monomers derived from renewable resources,such as corn and starch.As one kind of the most promising mature polymer materials,PLA has attracted wide attention from various fields such as medicine,food packaging,automotive,agricultural forestry,and electronic appliances due to its excellent performances including biodegradability,biocompatibility,and good mechanical and optical properties.However,the poor thermal stability?crystallization rate and brittleness of PLA limit its processing and application.For improving the processing and mechanical properties PLA,PLA is usually modified by melt blending with other polymer,added chain extenders or filled with filler which are the effective and most commonly used method.The main work and contents of this paper are as follows:Firstly,The polyamide 6(PA6)/KCl composites were prepared by melt blending method.The effect of KCl content on the crystallization behavior,as well as rheological and mechanical Properties of the composities was studied,the mechanism of confined crystallization was also systematically investigated.The results show that the tensile strength,notch impact strength increased first and decreased finally with the increase of KCl content.The dynamic mechanical property measurement results demonstrated that the storage modulus of composite materials was higher than that of pure PA6 in the measuring temperature range,and the storage modulus of the composites increased with the increase of KCl content,The crystallization behavior results reveal that the with addition of content KCl,the temperature of nucleation,the growth temperature of crystal,the melt temperature of crystal and the glass transition temperature of spherulites dramatically decreased,The density and the rate of nucleation also decreased gradually,the crystallization ability of PA6/KCl composite decreased,the crystallization induction time gradually increased.The rheological properties of results show that with the increase of KCl content,composites zero shear viscosity increased and all the system showed pseudo plastic fluid behavior,the phenomenon of shear thinning became more and more obvious,the changes in relaxation mechanism led to the gradually increase in the characteristic relaxation time ?1,?2 and ?3.Secondly,Low-Melting-Point polyamide-6(LMPA6)was used to toughen Poly(lactic Acid)(PLA),and epoxy51 was used as compatibilizer.It found that PLA/ LMPA6 composites were incompatible blend systems.The results indicated that the addition of LMPA6 into PLA/LMPA6 composites increased the density of bound node and restricted the mobility of PLA chain,which could significantly reduce the crystallinity and melting temperature of PLA and increase the cold crystallization temperature and glass transition temperature,and significantly improved complex viscosities,storage modulus and loss modulus.Moreover,the peristaltic relaxation time of PLA/LMPA6 composites was longer than that of PLA.The study of degradation behavior shows that the addition of LMPA6 can promote the thermal degradation and natural degradation of the PLA/LMPA6 composite system,and also enhance the barrier properties of the composite system.the tensile strength and impact strength increase with the increase of LMPA6 content,When the amount of LMPA6 was(22)Phr,the tensile strength,notch impact strength of the PA6/LMPA6 composities reached the maximum values at 72.8Mpa MPa and 5.0 KJ/m~2,respectively,which presented 10.8% and 78.5% improvement compared to those of the pure PLA.Lastly,PLA/LMPA6/OMMT composites were prepartion by the melt blending method using extruder.Using universal testing machine through mechanical properties test,X-ray diffraction analysis(XRD),thermogravimetric analysis(TG)the performance of the blend was studied.Was studied by differential scanning calorimetry different content of OMMT on the crystallization properties of the blend system.The crystallinity of the composite is related to the content of OMMT,when the OMMT content is less than 5%,the crystallinity increased with the increase of OMMT content increases,more than 5%,the crystallinity was worse instead.Rheological properties research results show that with the increase of the content of OMMT composite system of the energy storage modulus and loss modulus showed a trend of increase.In addition,the addition of OMMT can effectively improve the thermal stability of materials and barrier property.Mechanical properties of the research results show that with the increase of OMMT content,the tensile strength?elongation break and bending strength increased firstly and decreased finally with the increase of OMMT content.When incorporation the amount of 3% OMMT into composites,the tensile strength,elongation break and notch impact strength of the e PLA/LMPA6/OMMT composities reached the maximum values at 61.92Mpa?6.60% and 5.3KJ/m~2.Making use of the synergistic effect of LMPA6 and OMMT to modified PLA,which can improve the mechanical properties and blocking performance of PLA,a new way was provided for the preparation of high performance polylactic acid(PLA)composite material,It is conductive to the expansion of engineering application field for PLA.