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Reinforcement of Segmented Polyurethanes with Cellulose Crystals
M. L. AUAD; T. RICHARDSON; M. A. MOSIEWICKI; N. E. MARCOVICH; M. I. ARANGUEN
Simposio; XI Simposio Latinoamericano y IX Congreso Iberoamericano de Polímeros; 2008
Departamento de Ciencias. Universidad Católica
Segmented polyurethanes are produced by reacting a long chain diol with a diisocyanate compound and a chain extender. These materials tend to phase separate (depending on the nature of the chemicals used in the synthesis) to give soft and hard blocks/segments. Depending on the type and on the composition of the soft and hard segments and the preparation procedures, the structure-property relationships of polyurethanes can be tailored to obtain diverse properties. The existence of two phases may lead to shape memory behavior, in which the rigid phase behaves as a physical crosslink, while the soft phase offer the possibility of fixing a transient shape [1,2]. In this work, linear segmented polyurethanes (SPUs) were synthesized using 4,4-methylene-bis-phenyl diisocyanate (MDI) and poly(tetramethyleneglycol) (PTMG, molar mass = 2000) with 1-4 butanediol (BD) as chain extender. Sets of polyurethanes (PU) were prepared with a variable MDI/BD-based hard segment (HS) content ranging from 23 to 45 wt%. The synthesized PU showed shape memory properties, depending of the final structure. The effects of hard segment content on the thermal and mechanical properties were investigated. In order to increase the stiffness of these polymers without significantly decreasing the good shape memory properties, the SPUs were reinforced with small amounts of nano/micron size cellulose crystals.