Under Glass Weathering of Hemp Fibers Reinforced Polypropylene Biocomposites: Degradation Mechanisms Based on Emitted Volatile Organic Compounds

Abstract

The durability of hemp fibers reinforced polypropylene biocomposites was investigated after one year under glass exposure. Volatile organic compounds emissions were assessed using a new passive sampling method. Degradation pathways were examined in order to understand the weathering mechanisms. The polymer matrix was decomposed into oxygenated products due to UV rays and high temperatures. As regards hemp fibers, different degradation steps of the carbohydrates were highlighted according to the nature of the detected furans. At a non-weathered state, dehydrations preceded the ring-opening mechanism, often catalyzed by Maillard reactions. The further cyclization induced the formation of 2-or 5-substituted furans emitted by nonweathered materials. Reactions between identified products after weathering which were not yet found in literature were proposed in this paper. They often implied a keto-enol tautomerism but also dehydrations that induced the formation of 3-and 4substituted furanones. These differences can be explained by a primary decomposition of carbohydrates favored at a non-weathered state and a secondary one occurring at a weathered state.

Effect of thermal and ultraviolet exposure on volatile organic compounds emitted from basalt‐hemp reinforced polypropylene

“…Overall, the 30HF composite panels had the lowest amount of total detected VOCs and, when they were present, it was only at high temperatures. This could be due to the structure of the hemp beginning to break down when exposed to the high temperatures 13 . However, unlike Badji et al 13 and Kim, 14 furfural was not detected in high quantities in the materials for panels containing hemp.…”

“…This could be due to the structure of the hemp beginning to break down when exposed to the high temperatures 13 . However, unlike Badji et al 13 and Kim, 14 furfural was not detected in high quantities in the materials for panels containing hemp. Trace amounts of furfural were detected in the hybrid panels at all temperature levels, and was not detected at all in the 30HF panels until 77°C was reached, where then only 1 μg/m 3 was detected.…”

“…Librelon 7 removed small pieces of eight components from the vehicle and tested each separately determining which compounds are emitted. Recently, a year‐long study in France was conducted by Badji et al 13 on VOC emissions off‐gassing from weathered PP panels and hemp‐reinforced PP biocomposite panels. The panels were placed under windshield glass in a stainless‐steel box and exposed to the natural elements.…”

“…The same trend was detected for acetaldehyde from the hemp panels as the PP panels, but furfural compounds were the main emissions detected. Furfural is a compound emitted as a result of biomass degradation and the breakdown of hemicellulose 13,14 . Though concentrations of compounds being emitted were analyzed in this study, the main focus was on the mechanisms responsible for the off‐gassing.…”

“…Furfural is a compound emitted as a result of biomass degradation and the breakdown of hemicellulose. 13,14 Though concentrations of compounds being emitted were analyzed in this study, the main focus was on the mechanisms responsible for the off-gassing.…”