ABSTRACT:The correlation between molecular microstructure with crystallization behavior and environmental stress cracking resistance (ESCR) for three commercial grades of high-density polyethylene and their nanocomposites has been investigated. Molecular architecture was characterized using high-temperature gel permeation chromatography (GPC) test. Qualitative comparison of crystallinity and side chain branches of neat high-density polyethylenes (HDPEs) has been performed using FTIR test and results were in good accordance with GPC results. Investigation of crystallinity and effect of side chain branches on the crystallite's dimensions has been carried out by DSC and XRD tests. Moreover, it was found that addition of nano-TiO 2 to HDPE causes an increase in crystal content and a decrease in crystal size, simultaneously. It was concluded from ESCR characterization that molecular weight and side chain branches are the most important structural parameters affecting ESCR properties of HDPE. The significance of side chain branches is higher compared to molecular weight.

In this study, different blends based on polylactic acid (PLA)/polyolefin elastomer (POE) and compatibilized PLA/POE was prepared by melt mixing. The compatibilizer glycidyl methacrylate-grafted-polyolefin elastomer (POE-g-GMA) was synthesized in a separate process. The Fourier transform infrared spectrum confirmed the reaction of POE and glycidyl methacrylate. Meanwhile, the morphology of dispersed phase was observed by scanning electron microscope. The results indicated that the compatibilizer has improved the compatibility and interfacial adhesion between PLA and POE phase. The rheological test results revealed that the introduction of compatibilizer could enhance the storage modulus and melt complex viscosity of PLA/POE blends. The foamability was studied in the presence of azodicarbonamide as a chemical blowing agent in the batch foaming process. Morphology of foams such as porous cell size, porous cell population density, and foam density were studied. It was found that the presence of POE in PLA foams has a great influence on their mechanical properties and the toughness. Addition of POE-g-GMA in samples increased elastic modulus of foams and decreased their strain at break.