Polyurethane (PU) adhesives were prepared from the reaction of polycaprolactone (PCL) polyols based on palm kernel oil based polyesteramide (PPKO) with an aromatic and cycloaliphatic diisocyanate. Four different formulations of PU adhesives were prepared by varying the NCO : OH ratio, in order to investigate the effects of NCO : OH ratios on adhesion strength. The adhesive strength of metal-metal bonding both in dry and hydrothermal ageing-was determined by single lap shear joint testing. The resistance to hydrolysis of the PU adhesives was determined by performing water absorption tests. The water absorption test samples suggested that the durability of the adhesives correlated to lower water absorption due to higher NCO content. The correlation between the crosslinking of the PU network and adhesive strength was also studied by performing swelling tests. The higher NCO content showed that, the higher crosslink density of PUs led to higher cohesion and adhesion strengths. PU1.7 showed optimal properties in terms of durability and resistance to hydrolysis, whereas PU2.0 revealed deterioration in durability and resistance to hydrolysis due to the presence of greater micro-voids content in the PU2.0 matrix. (C) 2014 Wiley Periodicals, Inc.

Surface treatment of aluminium alloy plays a significant role in improving the strength of the adhesive bond. In this study, an aluminium alloy 2024-T3 was treated by two different methods of surface treatments i.e. by alkaline etching and warm water treatment followed by silanization method in order to enhance the adhesive bonding. Three different formulations of polyurethane adhesive by varying the NCO:OH ratios which were prepared from polyol polycaprolactone (PCL) based on palm kernel oil polyesteramide (PPKO) with a blend of aromatic and cycloaliphatic diisocyanate. Surface morphology, surface chemical analysis, wettability and surface roughness of the treated samples were characterised using field emission scanning electron microscopy and energy dispersive X-ray analysis (FESEM/EDX), X-Ray Photoelectron Spectroscopy (XPS), contact angle goniometry and surface profilometry, respectively. The influences of surface treatment techniques and conditions on durability of the joint strength and interfacial properties were explored by performing the single lap shear test and wedge test. The effects of NCO:OH ratios on PU adhesive strength were also investigated. Durability of PU adhesive bonding is found to display an interesting dependence on the surface treatments. (C) 2014 Elsevier Ltd. All rights reserved.

The main objective of this study was to investigate the effect of different types and molecular weight (MW) of polyol on the shape memory properties of palm kernel oil-based shape memory polyurethane (SMPU) prepared by two step bulk polymerization procedure. Poly(ethylene glycol) (PEG) and poly(epsilon-caprolactone) (PCL) with MW 2000 and MW 4000 were used as the main material for soft segment. The addition of palm kernel oil polyol (PKO-p) in the SMPU system is due to the concern of the renewable resources. Shape fixity and shape recovery properties were investigated using bending test to evaluate the shape memory effect. The results indicate that the shape fixity of SMPU depends primarily on the types of polyol whereas MW had a slight effect towards the shape fixity. SMPU synthesized from PEG with MW 2000 performed a good shape fixity, about 96% compared to that of PCL with MW 2000, about 29%. In the case of PCL - based SMPU, the increase of shape fixity is proportional to the increase of MW. All samples, except the one based on PEG4000, exhibited excellent shape recovery (100%). (C) 2019 Elsevier Ltd. All rights reserved.