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The effect of accelerated weathering exposure time on the bioplastic, poly(3-hydroxybutyrate- co -3-hydroxyvalerate) (PHBV) was studied. The chemical structure and thermophysical property changes of solvent cast PHBV films were examined by a combination of optical microscopy, size exclusion chromatography, FTIR and 1 H NMR spectroscopies, tensile testing, and differential scanning calorimetry (DSC). The exposed PHBV surfaces experienced surface crazing upon weathering. The molar mass of weathered PHBV was shown to decrease due to chain scission which was dominant over the crosslinking reaction mechanism, and compositional analysis showed the polymer degradation was non-random between the hydroxybutyrate-hydroxyvalerate units. The degree of crystallinity for PHBV was shown to increase significantly (by about 20%) upon weathering. Tensile tests showed that the weathered PHBV exhibited reduced ultimate strength and elongation to break, while the Young's modulus increased ascribing to an increase in crystallinity. Different degradation mechanisms (Norrish I/II, radical initiation, crosslinking, and hydrolysis) of PHBV are proposed and confirmed based on the experimental findings. This study provides degradation insight for PHBV exposed to both UV radiation and moisture. [ABSTRACT FROM AUTHOR]

Abstract: Poplar wood fibers were chemically modified by esterification (acetate, propionate, benzoate) and then compounded with high density polyethylene (HDPE) into wood plastic composites (WPC). The esterified fibers were characterized (spectroscopy, TGA and contact angle) and shown to be more thermally stable and hydrophobic than unmodified fibers. The WPC were characterized for their mechanical and rheological properties, adhesion factor, water resistance, accelerated weathering and biodurability performance. Color change, surface morphology and extent of oxidation on the surface of weathered WPC were monitored using colorimetry, microscopy and FTIR spectroscopy, respectively. Benzoylated fiber based WPC experienced the least surface crazing and color change due to weathering. Esterification of fibers significantly reduced weight losses in the resulting WPC when it was exposed to brown-rot and white-rot fungi as compared to unmodified fiber WPC. Esterification of wood fibers resulted in more biodurable and photostable WPC. [Copyright &y& Elsevier]

Abstract: The effects of outside and accelerated (xenon-arc and UVA) weathering on the visual appearance and chemical changes of wood plastic composite (WPC) formulations based on high density polyethylene (HDPE) and polypropylene (PP) were investigated. Colorimetry, scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), and pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) were employed in this study. The study showed that for both outside and accelerated weathering, longer exposure time increased the degree of color change (and lightness), carbonyl concentrations, and wood loss on weathered WPC surfaces. HDPE-based WPC exhibited decreased lightening, carbonyl concentrations, and wood content loss when compared to PP-based WPC. From this study, relationships between chemical and color changes that occurred during exterior weathering of HDPE-based WPC were established. Oxidation and degradation of wood lignin influenced WPC color changes (lightening) during weathering. [Copyright &y& Elsevier]

The plastic waste accumulation has been increasing and a solution other than landfilling is required. Due to the high cost of recycling, thermal treatment could be an option. However, the existence of polyvinyl chloride (PVC) would release hydrochloric acid which would cause emission problems as well as damage to the reactor systems. The thermal degradation of PVC has been studied over the years. However, the mechanism of the PVC thermal degradation is not fully developed. Specifically, the mechanism of the PVC thermal degradation at medium temperatures, which is more practical for industries, is still lacking. A degradation temperature of 300 °C was used to study the dehydrochlorination behavior of PVC. A rather comprehensive mechanism with four consecutive reactions has been developed based on the micro-pyrolysis experiments and has been validated and proved by predicting the mass loss, chlorine content, heat content and elemental composition with high precision experimental data in different reactors with/without heat transfer coupling. • A four consecutive reaction mechanism was developed for PVC degradation at 300 °C. • The mechanism was based on the release of HCl, benzene, naphthalene and anthracene. • The mechanism was proved by predicting Cl/H/C/heat-content data in other reactors. [ABSTRACT FROM AUTHOR]

Corrugated cardboard (CCB) was pyrolyzed at different temperatures (350, 400 and 450 °C) to produce biochar fibers. The biochar and CCB control fibers were then compounded with high density polyethylene (HDPE) and maleated polyethylene (MAPE) to prepare wood plastic composites (WPC). The effect of different pyrolysis temperature biochars on the WPC's mechanical, thermal and viscoelastic properties, water absorptions, rheological behavior, weatherability and biodurability performance were evaluated. The CCB composite melts showed higher modulus and viscosity than biochar composites, indicating better melt strength. Compared with CCB composites, an increase of tensile strength (4%) and tensile modulus (30%) could be observed in composites made from CCB 350 °C biochar. In addition, the CCB biochar composite showed lower tan δ and adhesion factor, indicating the strong interfacial interaction between biochar fibers and HDPE. The composite melting temperatures (T m) were not significantly different. The degree of HDPE crystallinity in the biochar composites decreased relative to the CCB composites, while the thermal properties of the composites improved compared with CCB composites. The CCB composite displayed the highest water absorption (3.9%) and thickness swell (3.8%) after 70 d. The CCB biochar (450 °C) composite experienced the least color change, lightless and carbonyl concentrations due to weathering. Pyrolysis of CCB reduced weight loss in the resulting composites exposed to fungi compared with the CCB composite. Using CCB biochar led to a more biodurable WPC. • This study compared cardboard and cardboard biochar fibers for use in HDPE composites. • Biochar fibers improved composite mechanical properties, dimensional stability, photostability and biodurable properties. • CCB350 composite showed the best mechanical properties. • CCB400 composite showed the best dimensional stability. • CCB450 composite showed the best photostability and biodurability against fungal attack. [ABSTRACT FROM AUTHOR]