Influence of the Structure of Low MolecularWeight Esters on Poly(lactic acid) in the Plasticization Process - part 1

Abstract

Polymers derived from renewable sources which are additionally subject to degradation processes are currently an interesting alternative to conventional polymers of petrochemical origin. One of such polymers is poly(lactic acid) (PLA), which can be used in the packaging, textile and also medical industries. Its great advantage is the susceptibility to biodegradation and the nontoxicity of the degradation products. Because of high brittleness and stiffness, the modification of PLA is necessary to improve its plastic deformability, which can expand the new application possibilities. As part of the research work, the modification of PLA by plasticisation was undertaken to improve its plastic deformability properties. The low molecular mass esters from the citrate group and glycerol triacetate were used. The samples extruded from plasticised polymer were characterised using Differential Scanning Calorimetry (DSC) and Gel Permeation Chromatography/Size Exclusion Chromatography (GPC/SEC). The mechanical properties and melt flow rate after modification were determined. The aim of the research was to determine the relationship between the structure of a plasticiser and its ability to reduce the interactions in the polymer chain in order to develop an optimal polymer-plasticiser arrangement. Based on this research, there was no relationship between the efficiency of the plasticisation process and the increasing molecular mass of the plasticiser. The additional chemical (acetyl) group in the plasticiser also does not increase the efficiency of the PLA plasticisation process. In the next steps of the research, functional forms will be produced, i.e. fibers, films, and fittings from the selected polymer-plasticiser systems.