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.
Polycaprolactone (PCL) polyol was prepared by a ring opening polymerization of ε-caprolactone initiated by palm kernel oil (PKO) based polyol and 1,6-hexanediol to form a PCL/PKO based polyol. The properties of polyol were varied by their initiator:co-initiator weight ratio. The completion of polyol formation was characterized through Fourier Transformation Infrared (FTIR) spectroscopy. Other parameters such as acid number and hydroxyl number of polyol were also studied to monitor the progress of reaction. FTIR results showed the significant changes particularly for the OH and C=O stretching peaks.
The effect of substrate surface roughness on the wettability of SAC237 (Sn 99.9%, Ag 0.3%, Cu 0.7%) with difference percentage of CNT on copper substrate was investigated. Solder paste of SAC 237 without CNT, 0.01% and 0.04% of CNT were reflowed at 270°C on different surface roughness of Cu substrate (abrasive number 240, 400, 600, 800). Contact angle of soldered samples measured by Infinite Focus Microscope (IFM). As a result, contact angle value of investigated solders range 7° to 20°. Contact angle obtained decreases with the increasing surface roughness of Cu substrate. This demonstrates that rougher substrate enhance the wettability of the solders. Addition of CNT also effects the wettability of investigated solders. Higher composition of CNT show better wettability.
Polyurethane (PU) adhesives were prepared from three different polyols based on polycaprolactone (PCL)/palm kernel oil (PKO) with an aromatic and cycloaliphatic diisocyanate. The adhesives were characterized through Fourier Transformer Infrared (FTIR) spectroscopy in order to ensure the formation of urethane and the completeness of polymer reaction. The effects of NCO/OH ratios and types of diisocyanate on PU adhesive strength were investigated. The adhesive strength of metal to metal bonding was determined by single lap shear joint testing. The correlation between crosslinking of PU network and adhesive strength was also studied by performing swelling tests.
Polyurethane is a highly versatile polymer that may be used in various types of applications with a wide range of properties. The combination of different types and ratios of isocyanate and polyol allows for the control of the desired end properties. Due to its unique properties, it has found applications in the fi elds of medical, military, automobile, and aerospace industries. Recently, there has been a prodigious interest in producing polyurethane-based smart polymers, especially shape memory polyurethane (SMPU). This is due to its excellent ability to change shape upon the application of external stimuli such as heat, electric fi eld, magnetic fi eld, and light. The existence of phase-separated structure known as soft-and hard-segment domains contributes toward the shape memory properties of polyurethane. The soft-segment domains are responsible for maintaining the temporary shape, while hard segments fi x the permanent shape. This chapter comprehensively aims to address a wide overview of polyurethane-based smart polymer and the chemistry behind the shape memory properties. In addition, this chapter also summarizes the recent studies on the exploration of SMPU using vegetable oils along with petroleum-based polyol and the potential applications of smart polyurethane.
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