Biomaterial based novel polyurethane adhesives for wood to wood and metal to metal bonding

Abstract

Polyurethane adhesives made from synthetic chemicals are non-biodegradable, costly and difficult to find raw materials from local market. To avoid solid pollution problem, cost effectiveness and easy availability of raw materials, biomaterials based polyurethane adhesives are used in current industrial interest. Direct use of castor oil in polyurethane adhesive gives limited hardness. Modification on active sites of castor oil to utilize double bond of unsaturated fatty acid and carboxyl group yields new modified or activated polyols, which can be utilized for polyurethane adhesive formulation. In view of this, we have synthesized polyurethane adhesives from polyester polyols, castor oil based polyols and epoxy based polyols with Isocyanate adducts based on castor oil and trimethylolpropane. To study the effects of polyurethane adhesive strength (i.e. lap shear strength) on wood-to-wood and metal-to-metal bonding through various types of polyols, cross-linking density, isocyanate adducts and also to compare adhesive strength between wood to wood and metal to metal surface. These polyols and polyurethanes were characterized through GPC, NMR and IR-spectroscopy, gel and surface drying time. Thermal stability of PU adhesives was determined under the effect of cross-linking density (NCO/OH ratio). The NCO/OH ratio (1.5) was optimized for adhesives as the higher NCO/OH ratio (2.0) increasing cross-linking density and decreases adhesion. Lower NCO/OH ratio (1.0) provideslow cross-linking density and low strength of adhesives.

Thermoplastic Polyurethanes Stemming from Castor Oil: Green Synthesis and Their Application in Wood Bonding

“…To further investigate whether the CPUs have the potential to be used as wood adhesives, their wood-to-wood bonding properties were evaluated. As shown in Table 1, lap shear strength of the CPUs was found to be between 12.0 and 18.9 N/m 2 , which is comparable to previous reports [49][50][51]. The lap shear strength increased with the decrease of the chain length in CPUs.…”

Bio-Renewable Sources for Synthesis of Eco-Friendly Polyurethane Adhesives—Review

“…Other work describe the performance of castor oil based novel polyurethane adhesive system for wood to wood and metal to metal bonding by using polyester polyols, castor oil-polyester polyols and epoxy-polyester polyols with different isocyanate adducts having different NCO/OH ratio. Castor oil-polyester polyols were synthesized through the transesterification reaction between castor oil and polyester polyols [117]. Castor oil based polyester polyols were synthesized by the condensation polymerization of different dicarboxylic acids such as, maleic acid, fumaric acid, and oxalic acid with castor oil.…”

Castor oil and commercial thermoplastic polyurethane membranes modified with polyaniline: a comparative study

“…Among the conventional polymers, polyurethanes (PUs) show good mechanical properties, such as stiffness and flexibility [11][12][13] . Polyurethanes are segmented polymers with microphase separated morphology 14 . It is noteworthy in the engineering thermoplastic PU application the morphology of this material.…”