Comparison of Photo Degradation Behavior of LDPE using Accelerated Weathering Instruments

Abstract

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.

New Indoor Accelerated Weathering Condition for Approximating Molecular Weight Distribution of Outdoor-Exposed LDPE

“…The 1,715 cm -1 absorption peak began to form after the 1,740 cm -1 peak began to form; therefore, it is considered that esters are formed by path 1 at the initial stage of photo degradation and attributable fraction of esters formation by path 2 increase gradually at the next stage. In this and previous studies [12,16], the following two findings were obtained. The mechanism of these phenomena in this study is considered to be as follows.…”

“…Table 3 shows average Mn, Mp, Mw between the irradiated and reverse sides of the test pieces. These data were obtained in current and the authors previous studies [16].…”

“…5) did not exhibit a noticeable absorption peak at 1,715 cm -1 as with the outdoor-exposed samples. In the authors previous study using FUV [16], the carbonyl absorptions of photo degraded LDPE samples at low temperature and/or low UV irradiation tended to be larger than those at high temperature and/or high UV irradiation. In this current study, the IR spectra of photo degraded LDPE were compared among XWOM-ST/-HT and SXWM-ST/-HT.…”

“…3 shows the relationship between tensile strength (retention percent) and elongation (retention percent) for all samples. The data obtained in the authors previous study [16] was added to Fig. 3.…”

“…In the authors previous study [16], the authors found that the molecular weight distribution of LDPE (low-density polyethylene) photo degraded using a FUV (fluorescent UV lamp) at a higher BPT (black panel temperature) (80 °C) was more similar to that of an outdoor-degraded sample than those of other samples artificially photo degraded using a xenon arc lamp at standard BPT (63 °C) or using a FUV at standard BPT (60 °C). It was considered that the accelerated weathering tests at higher sample temperature could accelerate cross-linking by radical recombination more than chain-scission for molecules of high molecular weight, consequently recreating molecular-enlargement similar to that of the outdoor-exposed sample.…”