Samples of low-density polyethylene (LDPE) were photodegraded using accelerated weathering instruments and outdoor exposure. The physical properties and chemical structures of the photodegraded samples were studied through a tensile test, gel chromatography, and infrared spectroscopy. The molecular weight distribution of a photodegraded sample by using a fluorescent UV lamp at a high black panel temperature (80℃) was more similar to that of an outdoor-degraded sample than that of other artificially photodegraded samples by using a Xenon lamp at the standard black panel temperature (63℃) . It is estimated that accelerated weathering tests at a high sample temperature could accelerate cross-linking than chain scission, consequently recreating moleculeenlargement similar to the outdoor-degraded sample.
The size dependent hardening in Al-4wt%Cu thin film on Si substrate has been investigated by the numerical calculation of indentation stress field and the observation of plastic zone microstructure of indented film. Distribution of internal stress predicted by triangular dislocation loop (TDL) model shows no size dependency with the different number of dislocations when the constant line density is assumed at the contact surface. TEM cross-sectional observation reveals that the plastic deformation is dominantly induced inside the film, and the growth of plastic zone is restricted at the interface of hard Si substrate. The size dependent hardening in soft film and hard substrate system is discussed from the change in dislocation density with respect to the plastic zone microstructure.
Abstract. The surface displacement of the indented layered composite has been observed by AFM and TEM, and the elastic recovery due to the indentation residual stress is compared with the prediction of the triangular dislocation model. At the shoulders of the indentation, the upheaval of Al-4wt%Cu film is smoothly connected, whereas that of Al 2 Cu film is localized as the intensive sheared displacement. The magnitude of the elastic recovery in film/substrate composite is larger than the predicted value, which might be attributed to the repulsive interaction between the glide dislocations and the hard Si substrate.
LDPE (low-density polyethylene) photo degraded through various accelerated weathering tests has the molecular weight distribution curves unlike that through outdoor exposure. The authors therefore developed new weathering test condition based on the existing accelerated weathering test using a xenon arc lamp. Samples of LDPE were photo degraded using various accelerated weathering test conditions and outdoor exposure. The physical properties and chemical structures of the photo degraded samples were studied through a tensile test, infrared spectroscopy, and gel chromatography. The authors found that the molecular weight distribution curve of a sample photo degraded using a xenon lamp at a higher BPT (black panel temperature) (73 °C) was more similar to that of an outdoor-exposed sample than that of a sample photo degraded at the standard BPT (63 °C). It is considered that higher temperature accelerates radical recombination, consequently recreating molecular enlargement similar to the outdoor-exposed sample. Multiple regression analysis using newly introduced Mp (peak-top molecular weight) and Mw (weight-average molecular weight) as explanatory variables was conducted, which successfully enabled the authors to provide a simple explanation for the decrease in polymer tensile strength.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.