The Effect Of Low Melting Point SnPb Alloy Powder On The Structure And Properties Of HBP Modified PLA

Polylactic acid(PLA)is a degradable thermoplastic with goo d biocompatibility and environmental friendliness,and can be naturally degrad ed into CO2 and H2 O under the action of microorganisms.PLA have a wide range of applications in the areas of biology,manufacturing Industry and medicine because of these two advantages.Modification of PLA with physical methods and addition of low-melting point metal is currently hot topic.In this paper,PLA was modified by adding lubricant hyperbranched polyester(HBP)and Sn Pb alloy powder and injection molded.The mechanical properties(tensile strength,bending strength,Vickers hardness and impact Strength),rheological properties and crystal structure of the composite materials are studied,the main conclusions are as follows:1.As the content of HBP increases,the tensile strength,flexural strength and Vickers hardness of the composite material increase firstly and then decrease.The maximum values appear when the HBP content is 1.5wt%,,which shows that the addition of HBP enhances the mechanical strength of the matrix,and the optimal amount of HBP is 1.5wt%.And then the mechanical properties of the composite material decline with the increase of HBP content continuously.2.HBP content is positively correlated with the melt flow rate of the composite material,indicating that as the amount of HBP increases,the melt fluidity of the composite material becomes better and the melt viscosity decreases.The plasticity uniformity of PLA-1.5wt%HBP is general and the fracture mode is brittle fracture.3.As the lubricant,HBP improves the fluidity of the melt and increases the athletic ability of molecular chains when the melt cools and crystallizes in the mold to increase the regularity of their molecular chains.Therefore,with the addition of HBP,the relative crystallinity of PLA-based composite materials increases firstly and then decreases,but it shows an increasing trend comparing with pure PLA.4.HBP has both internal and external lubrication functions.The lubrication between the molecular chains enhances the fluidity of the melt and the degree of plasticization of the melt,but it cannot form a stable bond w ith the matrix so that it cannot chang the distance between the molecular chains,so there is basically no increase of Toughness effect in matrix.But the lubrication reduces the friction between the melt and the cavity of the injection molding machine,so that PLA would not be scorched or decomposed during the injection molding process due to excessive friction.5.With the increase of Sn Pb content,the tensile strength,flexural strength and Vickers hardness of the composite material tend to increase firs tly and then decrease.The maximum point appears when the Sn Pb content is 2wt%.This shows that the addition of Sn Pb improves the mechanical strength of the matrix and the optimal amount of Sn Pb alloy powder is 2wt%;6.By studying the fracture morphology and surface morphology of PLA-1.5wt% HBP-2wt%Sn Pb,the component with the best mechanical properties,the fracture characteristics were found to be brittle fracture,but Sn and Pb were dispersed on the matrix around some metal parti cles This distribution is equivalent to forming a metal network around the alloy particles,which strengthens the interface between the matrix and the large particles.7.The melt fluidity of the composite material is strengthened with the increase of the Sn Pb content.SnPb absorbs heat in the screw and melts,which is a very viscous mobile phase.As the screw rotates,it flows in the PLA melt,reducing the apparent viscosity of the composite,so the MFI of PLA-1.5wt%HBP-2wt% improves.And Adding SnPb the composite material did not generate new substances with addition of alloy powder.The relative crystallinity of Sn Pb/PLA composite reached its maximum value when the content of Sn Pb alloy powder is 2wt%,which also determines that the optimum amount of SnPb added to the composite is 2wt%.