No abstract

As a part of an ongoing project on the production of composite materials based on poly(vinyl alcohol) (PVA) and polymeric materials from renewable resources, the present paper reports on the incorporation of agricultural waste materials as organic fillers in a film matrix based on PVA as continuous phase. In this study lignocellulosic fibers byproducts, derived from sugar cane (SC) and apple (AP) and orange (OR) fruit juice extraction, were cast from PVA aqueous solutions. The effect of fiber type and composition on the relative properties of cast films was evaluated and compared. OR resulted to be suitable for blending in higher amounts by weight than SC and AP. Glycerol and urea were added as plasticizing agents and were observed to be effective in giving flexible films. Additionally, cornstarch was added to further increase the composition of polymers from renewable resources in cost-effective and ecoefficient composite film formulations. The prepared films resulted sensitive to moisture and water. To reduce water sensitivity, hexamethoxymethylmelamine (HMMM) was tested as a cross-linking agent for the present composite formulations. Cross-linked films exhibited significant improvement in water-resistance that can be taken as a tuneable structural feature for customized applications. The mechanical properties of the prepared composite films (elongation at break, tensile strength, Young modulus) were found to be dependent upon the nature and content of the filler and on environmental conditions.

No abstract

No abstract

No abstract

An environmentally friendly wood adhesive was developed by crosslinking cornstarch and poly(vinyl alcohol) (PVOH) with hexamethoxy‐methylmelamine (Cymel 323). Citric acid was used as a catalyst and latex (UCar 443) was added to improve moisture resistance. The adhesive was evaluated for its utility in plywood manufacture. It exhibited excellent mechanical properties comparable to many of the commercially available urea‐formaldehyde plywood adhesives used for interior applications. The viscosity of the adhesive at 27 % (w/v) was 7000 mPas, allowing easy application to wood surfaces by brush. The minimum concentration of crosslinking agent needed to achieve good mechanical properties in plywood was 15 % (w/w proportion of total solids). Optimum curing temperature and curing time were 175 °C and 15 min, respectively. Addition of latex to the adhesive formulation improved both moisture resistance and physical properties of plywood test samples. Samples prepared with an optimal adhesive formulation, when completely immersed in water for 2 h or exposed at 93 % or 50 % relative humidity (RH) for 30 days, exhibited > 90 % failure in the veneer as opposed to < 10 % failure in the adhesive joints.

No abstract

Rewritable paper is meaningful to the recyclable and sustainable utilization of environmental resources and thus has been extensively investigated for several decades. In this work, we demonstrated an efficient and convenient strategy to fabricate rewritable paper based on reversible hydrochromism of donor−acceptor Stenhouse adducts (DASAs). The kinetics and efficiency of isomerization could be well-controlled by adjusting the surrounding temperature and humidity. Monocolored rewritable paper was prepared by coating cyclic DASA• xH 2 O on the paper surface. Writing, printing, stamping and patterning were realized on the rewritable paper. The information could be controllably erased by treatment in a humid atmosphere. More importantly, the rewritable paper was upgraded to multicolored by combination of two DASA materials. The color of chirography was switched by controlling the writing speed.