Interpenetrating polymer networks based on castor oil polyurethane/cellulose derivatives and polyacrylic acid

摘要

Castor oil, 2,4-tolylene diisocyanate (2,4 TDI), cellulose acetate, and hydroxiethyl cellulose, based polyurethane (PU) - polyacrylic acid (PAA) sequential interpenetrating polymer networks (IPN's) were synthesized. PU's were prepared by reaction of hydroxyl groups from castor oil, and cellulose acetate or hydroxiethyl cellulose with 2,4 TDI, using dibutyl tin dilaurate (DBDTL) as catalyst. PU's were swollen in acrylic acid monomer solution and subsequently polymerized by radical polymerization initiated with 4,4-azobis(4-cyanovaleric acid) (ACVA), and N,N'-methylenebis acrylamide (NNMBA) as crosslinking agent. Series of three PU/PAA ratios (75/25, 50/50, 25/75) were prepared. Viscoelastic properties were studied by means of dynamic mechanical analysis (DMA), showing a maximum modulus for IPN with 25% PAA content. Tan d curve showed two main peaks, and ? relaxation which is due to lateral chains of PU, suggesting phase separation. The existence of two Tg in each IPN was also confirmed by differential scanning calorimeter DSC). Morphology of samples was observed using a scanning electron microscope (SEM), which revealed different fracture surfaces between the compatible and incompatible PU/PAA ratios studied. Fractures were decreasing to turn into roughness surfaces when the PAA was increasing within the IPN's.