Transparent Ultraviolet (UV)-Shielding Films Made from Waste Hemp Hurd and Polyvinyl Alcohol (PVA)

Abstract

This work proposes a new approach to fabricate highly transparent and flexible composite films that exhibit enhanced UV-shielding properties. Lignin has innate UV-shielding properties. However, when purified lignin, which is conventionally extracted through chemical treatment, is mixed with polymeric materials, its presence negatively influences the transparency of the resulting composite. High transparency and UV-shielding are desirable properties for many applications. In this study, composites were made by mixing lignocellulose particles and polyvinyl alcohol (PVA), where lignocellulose particles were obtained from ball-milled waste hemp hurd without chemical treatments. The UV-shielding properties of the resulting composite film, as a function of hemp/PVA weight ratios, were investigated. The intermolecular interactions between the hemp particles and the PVA were characterized using infrared spectroscopy with the presence of –C=O group at 1655 cm−1, providing evidence that the chemical structure of lignin was preserved. The fabricated hemp/PVA films exhibit stronger UV-shielding, in the UVA-I range (340–400 nm) than TiO2/PVA films. The composite films also showed comparable water vapor permeability (WVP) with commercial packaging plastic film made of HDPE (high-density polyethylene). The optimization experiments were reported, with aim at understanding the balance between the UV-shielding and mechanical properties of the hemp/PVA films. The findings of this work can be applicable to the packaging, food and cosmetic industries where UV shielding is of utmost importance, hence adding value to hemp hurd waste.

Use of Chènevotte, a Valuable Co-Product of Industrial Hemp Fiber, as Adsorbent for Pollutant Removal. Part I: Chemical, Microscopic, Spectroscopic and Thermogravimetric Characterization of Raw and Modified Samples

“…The analysis of the data showed that the treatments of the hemp shives did not cause significant structural variations, considering that only slight peak shifts towards higher 2θ angles related to the decrease of the interplanar distance of the cellulose’s planes, were observed. However, the intensity of the diffraction peak at 2θ ≈ 30° was increased after all treatments, which is in agreement with the data reported by Zhang et al [ 41 ]. This observation was interpreted by the lower preferential orientation of the cellulose fibers [ 37 ].…”

Lignin–Cellulose Nanocrystals from Hemp Hurd as Light-Coloured Ultraviolet (UV) Functional Filler for Enhanced Performance of Polyvinyl Alcohol Nanocomposite Films

“…Hemp hurd particle (50 g) was wet ball-milled with an Attritor mill (2S, Union Process, USA) at an agitator speed of 280 rpm for 20 h, as reported before [10]. In our previous study with hemp hurd, we have intensively studied the influence of ball-milling time on the crystallinity of hemp [10].…”

“…Native lignin can be a better choice for light-coloured UV-shielding filler, as less chemical treatment is required. In our previous study [10], we obtained native lignin with the ball milling method. The light-coloured native lignin-cellulose was further added into the PVA matrix as a filler.…”

Nanocomposites of PVA/cellulose nanocrystals: Comparative and stretch drawn properties

“…Fractured surfaces of stretch‐drawn samples were prepared by embedding with epoxy resin for 12 h and then frozen in liquid nitrogen. [ 16 ] Immediately after removal from the liquid nitrogen, samples were broken manually.…”