No abstract

The aim of this study was to develop fiber reinforced polylactic acid (PLA) composites via twin screw extrusion with the addition of a compatibilizer. Initial studies were performed to establish the optimum initiator percentage in terms of grafting efficiency between PLA and maleic anhydride (MA). Results show that PLA MA 7 obtained the highest level of grafting efficiency. Subsequent viscometric titration analysis on the compatibilized and uncompatibilized PLA composites showed an increase in the interfacial adhesion for the compatibilized PLA composites. Tensile and flexural properties also confirmed this increase in interfacial adhesion for the compatibilized composites, where the mechanical properties improved considerably, compared with virgin PLA and uncompatibilized composites. Results showed that the mechanical properties increase as PLA‐g‐MA loading increased. Finally, the rate of compostability of compatibilized composites decreased with the addition of PLA‐g‐MA. This was attributed to a lack of water absorption due to the bonding of hydroxyl groups on the fibers surface with MA. POLYM. COMPOS., 35:1792–1797, 2014. © 2014 Society of Plastics Engineers

Many authors have reported on the property enhancements possible by compounding high density polyethylene (HDPE) with fillers to produce composites. It is accepted that polyethylene combined with materials such as nanoclay or wood flour will not yield favorable properties unless a compatibilizing material is used to form a link. In this work, compatibilized HDPE was produced by grafting maleic anhydride (MA) to its backbone in a twin screw extruder using a peroxide initiated reactive process. Fourier transform infrared spectroscopy (FTIR) was used to examine the effects of varying peroxide and MA levels on the grafting percentage and it was found that a high percentage could be achieved. The gel content of each HDPE-g-MA batch was determined and twin bore rheometry analysis was carried out to examine the effects of crosslinking and MA grafting on the melt viscosity. These HDPE-g-MA compatibilizers were subsequently compounded with nanoclay and wood flour to produce composites. The composite materials were tested using a three point bending apparatus to determine the flexural modulus and strength and were shown to have favorable mechanical properties when compared with composites containing no compatibilizer. X-ray diffraction (XRD) was used to examine the effects of grafted MA content on the intercalation and exfoliation levels of nanoclay composites. The results from XRD scans showed that increased intercalation in polymer nanoclay composites was achieved by increasing the grafted MA content. This was confirmed using a scanning electron microscope, where images produced showed increased levels of dispersion and reductions in nanoclay agglomerates.

Biodegradable nanocomposites comprising of organically modified montmorillonitereinforced polylactic acid (PLA) and polyhydroxybutyrate (PHB) were assessed. This study investigates different nanocomposites mixing techniques as methods of achieving exfoliation. The incorporation of reverse flow mixing sections resulted in an increase in exfoliation of nanoclay platelets in PLA nanocomposites. PHB nanocomposites were shown to be more sensitive to thermal degradation and therefore benefited from a reduction in the number of processing steps utilised. Further development of the process was observed with the incorporation of compatibilisers for both polymers which led to considerable improvements in terms of mechanical properties exhibiting superior flexural properties. It was shown using x-ray diffraction that improvements in intercalation was observed which affected the compostability of both composites. Composites with increased interlayer spacing degraded faster and the nanocomposites in general degraded at a faster rate than the virgin polymers.

No abstract