Weijun Yang

Melt free radical grafting of glycidyl methacrylate (GMA) onto fully biodegradable poly(lactic) acid films: effect of cellulose nanocrystals and a masterbatch process

This article reports the preparation, by means of a masterbatch procedure, of poly (lactic acid) (PLA)/cellulose nanocrystal (CNC) films via premixing 1% wt of CNC into PLA or glycidyl methacrylate (GMA) grafted PLA (g-PLA). These films were obtained by reactive extrusion and subsequent film processing. In this study, 10% wt of GMA with respect to neat PLA was used in the extrusion phase, after that a final grafting degree of 5.69% was obtained. The film obtained by using the masterbatch steps were compared with the system obtained by a direct extrusion of 1% wt of CNC in PLA/g-PLA. Thermogravimetric, crystallization and mechanical properties, as well as morphology of CNC reinforced PLA nanocomposites were characterized. Differential scanning calorimetry and thermogravimetric analysis showed enhanced crystallization ability and an improved heat resistance for the resulting nanocomposites obtained after the use of masterbatches, for example field emission scanning electron microscopy confirmed that the masterbatch preparation procedure was beneficial to the dispersion of CNC in the final nanocomposites. Furthermore, different mechanical performance was obtained when using different masterbatches, which were considered to contribute to extend the applications of PLA based composites as food packaging materials in different sectors.

Effect of cellulose and lignin on disintegration, antimicrobial and antioxidant properties of PLA active films

This study reports the effects on antimicrobial, antioxidant, migration and disintegrability activities of ternary nanocomposite films based on poly(lactic acid) incorporating two biobased nanofillers, (cellulose nanocrystals (CNC) and lignin nanoparticles (LNP)), in two different amounts (1 and 3% wt.). Results from antimicrobial tests revealed a capacity to inhibit the Gram negative bacterial growth of Xanthomonas axonopodis pv. vesicatoria and Xanthomonas arboricola pv. pruni along the time, offering innovative opportunities against dangerous bacterial plant pathogens. LNP proved to be highly efficient in antioxidation activity, based on the disappearance of the absorption band at 517nm of the free radical, 2,2-diphenyl-1-picrylhydrazyl (DPPH) upon reduction by an antiradical compound; moreover the combination of LNP and CNC generates a synergistic positive effect in the antioxidation response of PLA ternary films. Furthermore, all the studied formulations showed a disintegrability value up to 90% after 15days of incubation in composting conditions. Migration results showed that the films can be considered suitable for application in food packaging field.

Polyvinyl alcohol/chitosan hydrogels with enhanced antioxidant and antibacterial properties induced by lignin nanoparticles

Polyvinyl alcohol/chitosan (PVA/Ch) hydrogels containing 1 and 3wt% of lignin nanoparticles (LNPs) were prepared through a freezing-thaw procedure. Results from microstructural, thermal and mechanical characterization of LNPs based PVA/Ch demonstrated that the lowest amount of LNPs (1wt%) was beneficial, whereas the presence of agglomerates at higher LNP content limited the effect. Moreover, a different swelling behaviour was observed for hydrogels containing LNPs with respect of PVA/Ch, due to the formation of a porous honeycomb-like structure. A synergic effect of Ch and LNPs was revealed in terms of antioxidative response by DPPH (1,1-Diphenyl-2-picryl-hydrazyl) activity of migrated substances, whereas results from antimicrobial tests confirmed LNPs as effective against Gram negative bacteria (E. coli) when compared to Gram positive (S.aureus and S. epidermidis) strains. The obtained results suggested the possible use of produced PVA/Ch hydrogels incorporating LNPs in many different sectors, such as drug delivery, food packaging, wound dressing.

Bio-Based Nanocomposites in Food Packaging

Abstract This chapter reviews different types of biodegradable bio-based matrices for food packaging applications, by considering synthetic and natural biodegradable polymeric (polysaccharide- and protein-based composites), with special emphasis on the advantages of nanotechnology application for the improvement of functional properties. A revision of intensive academic and industry research has been carried out to investigate the state of the art for new production methods, sources, and properties; to obtain biopolymers and bio-based nanocomposites that may replace conventional synthetic and nonbiodegradable materials in the packaging sector. The deep analysis of the market forecast for the specific sector confirmed how nanotechnology is expected to change the entire packaging industry, reducing fabrication costs and infrastructure, providing more flexible packaging methods, fresher and more customized products, producing competitive products in performance and price.