A Comparative Study of Glycerol and Urea-Modified Polyvinyl Alcohol/Oil Palm Ash Biocomposite Films

Abstract

Utilisation of oil palm ash (OPA) in plastic packaging is concerned to environment-friendly, improving performance, and saving the costs of plastics. This study further discussed and compared the properties of un-plasticised polyvinyl alcohol (PVOH)/OPA (80/20) films with PVOH/OPA (80/20) film plasticised with glycerol and urea at different concentrations. Glycerol-plasticised PVOH/OPA (80/20) film showed a decrease of tensile strength but an increase of elongation at break, whereas ureaplasticised film showed gradual increase of both tensile strength and elongation at break when concentration of plasticising agents was increased. This is due to the extensive hydrogen bonding and formation of stable dimeric structure with the addition of urea to PVOH/OPA (80/20) films, which was confirmed by the Fourier transform infrared (FTIR) spectroscopy analysis. In water absorption measurement, the increased concentration of plasticising agent exhibited a decreased water uptake percentage. Both plasticised PVOH/ OPA (80/20) films showed substantial weight loss in natural soil burial study but ureaplasticised films had lower weight loss as compared to glycerol-plasticised films at similar plasticiser concentration. Thermal analysis proved the increase of segmental mobility of polymeric chain in glycerol-plasticised film by showing lower glass transition temperature (T g), while urea-plasticised films exhibited higher T g due to urea solidification and better interfacial interaction with the hydroxyl group of PVOH and OPA. Also, urea-plasticised films showed higher decomposition temperature than glycerol-plasticised films.

Superhydrophilic Poly(2-hydroxyethyl methacrylate) Hydrogel with Nanosilica Covalent Coating: A Promising Contact Lens Material for Resisting Tear Protein Deposition and Bacterial Adhesion

“…That was because the amide bond in urea with a lower reactivity than hydroxyl group was hard to dehydrate with the hydroxyl group in PVA by a warm drying, unless in the presence of oil palm ash 43 or methanol. 44 Additionally, 7%NSHC-pHEMA hydrogel without dehydration presented a similar spectrum to the pHEMA hydrogel, indicating few nanosilica were stably anchored on the surface. These results confirmed that the dehydration facilitated the stable fastening of more nanosilica on the surface of NSCC-pHEMA hydrogel via Si−O covalent bonding, as opposed to much less nanosilica coating on 7%NSHC-pHEMA hydrogel by hydrogen bonding without dehydration.…”

“…However, it was different from the poly­(vinyl alcohol) (PVA)–urea hydrogel system, where a drying treatment at ∼60 °C just enhanced the hydrogen bonding due to the close contact of PVA chains and urea molecules. That was because the amide bond in urea with a lower reactivity than hydroxyl group was hard to dehydrate with the hydroxyl group in PVA by a warm drying, unless in the presence of oil palm ash or methanol . Additionally, 7%NSHC-pHEMA hydrogel without dehydration presented a similar spectrum to the pHEMA hydrogel, indicating few nanosilica were stably anchored on the surface.…”