Preparation Of Poly (Lactic Acid) Grafted Glycidyl Methacrylate And Its Influence On Poly (Lactic Acid)/Wood Flour Composites

During the experiment, poly(lactic acid) grafted glycidyl methacrylate(PLA-g-GMA) were produced by reactive extrusion. In order to prepare composites with better mechanical strength and processability, PLA-g-GMA were used as compatibilizers in Poly(lactic acid)/wood flour(PLA/WF) composites. The discussion was focused on the copatibility between PLA and WF in blend composites, and the main research contents and conclusions were showed as follows:PLA-g-GMA were prepared by twin-screw extruder via reactive extrusion, and dicumyl peroxide(DCP) was used as inititor. The chemical structure of the products were characterized by 1H NMR and FT-IR after purified, and it turned out that the GMA groups were grafted on PLA chains successfully. The grafting degree of purified PLA-g-GMA was determined by back titration, and the technologies of ractive extrusion(tenperature, content of GMA, content of DCP) were discussed. It was found that the grafting degree of PLA-g-GMA became 4.33% when the extrusion temperature was 185?, and the content of GMA and DCP were 20% and 0.8% to the quality of PLA, respectivity. The molecular weight of PLA-g-GMA decreased compared with pure PLA, and the molecular weight distribution became wider, which suggested the degradation of PLA during extrusion. The tensile strength and elongation at break showed decrease trend with the increase of PLA-g-GMA grafting degree. The storage modulus of PLA-g-GMA and pure PLA were similar under glass state, but the distortion temperature and glass transition temperature showed decrease trend with the increase of grafting degree.PLA/WF composites were prepared via twin-screw extruser and injection molding process, and PLA-g-GMA were added to the composites as compatibilizers to study the influence on the properties of blend composites. The tensile, flexural and impact strength of composites incerased with the increase content of PLA-g-GMA(4.33%), but the mechanical strength decreased after the content were above 15%. The tensile, flexural and impact strength could increase greatest by 31%, 21% and 35% compared to composites without PLA-g-GMA, respectively. Micromorphologic investigation revealed the interfacial adhesion between PLA and WF had been improved by the introduction of PLA-g-GMA, and cavities and gaps on tensile fracture surface diminished gradually with the increase content of PLA-g-GMA. The mechanical strength of composites increased with the increase grafting degree of PLA-g-GMA(from 2.63% to 4.33%), which indicated the better compatibility was achieved by higher grafting degree of comatibilizers.The pilot plant test to prepared PLA-g-GMA compatibilizer was conducted by Coperion twin-screw extruder CET-20 via reactive extrusion, and composites with and without PLA-g-GMA were also pilot plant test prepared. The results indicated that molecular weight of PLA-g-GMA showed decrease significantly compared with pure PLA, which revealed the severe degradation of PLA-g-GMA. The melt index was two double higher than pure PLA, and the extrusion melt pressure and current were high than the extrusion of pure PLA. After the addition of PLA-g-GMA, composites showed increase mechanical strength, and the tensile, flexural and impact strength could increase nearly 27.7%, 21% and 52.7% compared with uncompatibilized composites. The melt index increased with the addition of 15% PLA-g-GMA, and it showed 25% higher than that of the uncompatibilized PLA/WF composites.