RESUMEN
Owing to the environmental pollution caused by petroleum-based packaging materials, there is an imminent need to develop novel food packaging materials. Nanocellulose, which is a one-dimensional structure, has excellent physical and chemical properties, such as renewability, degradability, sound mechanical properties, and good biocompatibility, indicating promising applications in modern industry, particularly in food packaging. This article introduces nanocellulose, followed by its extraction methods and the preparation of relevant composite films. Meanwhile, the performances of nanocellulose composite films in improving the mechanical, barrier (oxygen, water vapor, ultraviolet) and thermal properties of food packaging materials and the development of biodegradable or edible packaging materials in the food industry are elaborated. In addition, the excellent performances of nanocellulose composites for the packaging and preservation of various food categories are outlined. This study provides a theoretical framework for the development and utilization of nanocellulose composite films in the food packaging industry.
RESUMEN
Fast-growing Chinese fir wood has shortfalls such as loose structure and low strength because it grows faster than natural trees. Resin impregnation is a great way to increase the strength of fast-growing fir. However, the resin used for impregnation is a kind of urea-formaldehyde resin, phenolic formaldehyde resin, melamine formaldehyde resin, and the like, which introduce harmful substances such as formaldehyde or phenolic into the wood. In this paper, Chinese fir wood was impregnated with natural shellac polymer, and the effects of impregnation variables on the mechanical properties of the wood were examined. The increase in strength in compression perpendicular to grain (SCPG) of wood samples impregnated with 15% shellac solution achieved a maximum value of 39.01%, but the modulus of rupture (MOR) was slightly reduced. The effects of the impregnation pressure, time, and their interaction were investigated by the response surface method (RSM). ANOVA analysis revealed that the impregnation pressure and time and the interaction between the two seemed to have a significant effect on ∆SCPG. Based on the response face model, the corresponding optimal parameters obtained are 1.0 MPa and 16.0 min for impregnation pressure and time, respectively. By impregnating fir wood with the above optimal conditions, the SCPG increased by 85.78%, whereas the MOR decreased by the least amount.
RESUMEN
With rising interior air pollution, health, and food shortage concerns, wood adhesives derived from non-food sustainable materials have therefore attracted considerable attention. Here we developed an eco-friendly cottonseed-lignin adhesive consisting of non-food defatted cottonseed flour (DCF), alkali lignin (AL), and graphene oxide (GO). The cation-π interaction, and hydrogen and covalent bonds between AL@GO and DCF collectively enhanced the cross-linking structure of the cured cottonseed-lignin adhesive, based on the Fourier-transform infrared spectroscopy, thermogravimetric analyses, scanning electron microscopy, and sol-gel tests. The high performance of the developed cottonseed-lignin adhesive was evidenced by its increased wet/dry shear strength and decreased rheological properties before curing and improved thermal stability and decreased soluble substances after curing. Particularly, the highest wet shear strength of poplar plywood bonded with cottonseed-lignin adhesive was 1.08 MPa, which increased by 74.2 and 54.3% as compared to the control and requirement of the Chinese standard GB/T 9846-2015 for interior plywood (≥0.7 MPa), respectively. The technology and resultant adhesives showed great potential in the preparation of green woody composites for many applications.
RESUMEN
Development of eco-friendly adhesives from renewable biomass has attracted considerable attention in recent years. Here, we present a novel approach via combination of waste newspaper (WNP) powder, oxidized glutinous rice starch, and polyamidoamine-epichlorohydrin (PAE) to prepare a formaldehyde-free starch-cellulosic adhesive (SCA) for woody composites. The oxidation treatment made the carboxyl/carbonyl groups more available in starch. Plywood bonded by the optimum SCA with 50 wt% of the WNP powder showed a wet shear strength of 0.83 MPa exceeding that of the oxidized starch adhesive by 130.5 %. During the curing process of SCA, the oxidized starch and WNP fiber participated into the crosslinking reaction with PAE via ester and ether bonds, as evidenced by FTIR analysis. The resulting cured adhesive had enhanced crystalline structures, thermal properties, hydrophobicity, wet-cohesion, rheological properties, and adhesiveness to wood. The SCA showed great potential in wood composites as an alternative to formaldehyde-derived adhesives.
RESUMEN
In order to solve the practical problem of heat transfer during the hot pressing process of a novel wood-plastic composite plywood, this paper investigates the perforation treatment of polyvinyl chloride (PVC) plastic films and their plywood composites. The PVC films were pretreated by the physical punching method, and the effects of PVC perforation diameter, hot pressing time and hot pressing temperature on the mechanical properties of the plywood composites were investigated by orthogonal experimental design. The results showed that the optimum hot pressing time was 7 min, the hot pressing temperature was 170 °C, and the PVC perforation diameter was 15 mm for the optimum mechanical properties. The punching pretreatment of PVC films gave rise to a reduction of the hot pressing time by 51 s due to improved heat transfer and heat loss by 5.06%, and allowed an increase in the initial moisture content of the veneer by 2-3%, thereby cutting down the drying cost in the veneer production process, which is conducive to energy conservation and environmental protection.
RESUMEN
Soy-based adhesives have attracted much attention recently because they are environmentally safe, low cost, and readily available. To improve the gluability and water resistance of soy-based adhesives, we prepared an enzyme-treated soy-based adhesive modified with an epoxy resin. We investigated the wet shear strength of plywood bonded with the modified adhesive using the boiling-water test. Fourier transformed infrared spectroscopy (FTIR) and ¹H nuclear magnetic resonance analysis were used to characterize the reaction between epoxy groups and â»NH2 groups in the modified soy-based adhesives. FTIR analysis confirmed the cross-linking structure in the cured adhesives. Viscosity and the solid content of soy-based adhesives gradually increased with the increasing amount of epoxy resin, but had little effect on its operability. Wet shear strength of plywood samples increased as the amount of epoxy resin was increased, whereas the inverse trend was observed regarding the water absorption of cured adhesives. Compared to an unmodified adhesive, the addition of 30% of epoxy resin increased the wet shear strength of plywood samples by 58.3% (0.95 MPa), meeting the requirement of the Chinese National Standard for exterior plywood. Differential scanning calorimetry and thermogravimetric analysis showed the improved thermostability of the cured adhesives after curing at 160 °C. These results suggest that epoxy resin could effectively improve the performance of enzyme-treated soy-based adhesives, which might provide a new option for the preparation of soy-based adhesives with high gluability and water resistance.
RESUMEN
This study aimed to establish human IFN-gamma (hIFN-gamma) in vitro release assay and to apply it in diagnosis of human tuberculosis. Human IFN-gamma gene was cloned and expressed in Escherichia coli. The recombinant hIFN-gamma was purified and used as immunogen to immunize mice and rabbits respectively. Monoclonal and polyclonal antibodies were respectively developed and a sandwich ELISA was established. The heparized whole blood from 111 active tuberculosis patients and 292 clinical healthy controls were collected. The blood was stimulated with tuberculosis specific fused antigen ESAT-6/CFP-10 and the plasma was collected for IFN-gamma detection. The sensitivity for tuberculosis diagnosis was 95.5%, whereas the positive detection rate for the healthy controls was 16.7%. There was a significant difference between the patients and healthy controls (P<0.01) indicating that this assay had a high sensitivity and specificity, and thus could be promising in tuberculosis diagnosis.