Study of Effect of NCO/OH Molar Ratio and Molecular Weight of Polyol on the Physico-Mechanical Properties of Polyurethane Plaster Cast
2 Abstract: Polyurethane plaster cast was an open weave fabric bandage, prepared by coating polyurethane prepolymer on raschel knitted fiberglass and polyester fabric. Curing takes place by coming in contact with water to form hard rigid cast. Polyurethane prepolymers were synthesized by reacting molar excess of diphenyl methane diisocyanate (MDI) with polypropylene glycol (PPG) at 60°C for 2 hours. This effect of different NCO/OH molar ratio and molecular weight of polyol on the tack free time, setting time, diametral compression strength, percent elongation and tensile strength of polyurethane plaster cast were investigated.. It was observed that with increase in NCO/OH molar ratio, tack free time and setting time of the cast decreases, whereas diametral compression strength increases. Tensile strength was determined in universal testing machine and was found to increase with increasing NCO/OH ratio while opposite trend was observed in case of percent elongation. With increase in polyol molecular weight, tack free time and setting time of the cast increases, whereas diametral compression strength decreases. Blended polyols i.e. PPG 1000 with PPG 400 in 50/50 ratio gives tensile strength and diametral compression strength in between their unblended counterparts. In comparison to fiberglass cast, polyester cast has higher percent elongation and diametral compression strength.
Effect of PEG Molecular Weight on the Polyurethane-Based Quasi-Solid-State Electrolyte for Dye-Sensitized Solar Cells
Nanosilica was surface modified with polyaniline and incorporated into polyurethane to form a polymer matrix capable of entrapping a liquid electrolyte and functioning as quasi-solid-state electrolyte in the dye-sensitized solar cells. The effect on the S−PANi distribution, surface morphology, thermal stability, gel content, and structural change after varying the PEG molecular weight of the polyurethane matrix was analyzed. Quasi-solid-state electrolytes were prepared by immersing the polyurethane matrix into a liquid electrolyte and the polymer matrix absorbency, conductivity, and ion diffusion were investigated. The formulated quasi-solid-state electrolytes were applied in dye-sensitized solar cells and their charge recombination, photovoltaic performance, and lifespan were measured. The quasi-solid-state electrolyte with a PEG molecular weight of 2000 gmol−1 (PU−PEG 2000) demonstrated the highest light-to-energy conversion efficiency, namely, 3.41%, with an open-circuit voltage of 720 mV, a short-circuit current of 4.52 mA cm−2, and a fill factor of 0.63.
Effects of number‐average molecular weight of liquid hydroxyl‐terminated polybutadiene on physical properties of the elastomer
The relationship between the molecular weight of liquid hydroxyl-terminated polybutadiene (HTPB) and the physical properties of the elastomers were investigated. HTPB having various molecular weights were cured with 4,4′-diphenylmethane diisocyanate (MDI) by the one-shot method and the physical properties of these elastomers obtained were measured. The tensile strenght, modulus, tear resistance, and the hardness decreased with increase in the molecular weight of HTPB, and this phenomenon was remarkable in the low molecular weight HTPB (below about 3000). On the other hand, the ultimate elongation increased linearly with increase in the molecular weight of HTPB. The effects of incorporating a short-chain diol, N,N-bis(2-hydroxypropyl)aniline, on the physical properties on the elastomers are also discussed.