The Effect of the Isobornyl Groups of the Grafted Poly(acrylate) Chains on the Tensile Properties and Low Temperature Flexibility of Polyurethane

A series of polyurethanes (PUs) grafted with poly(isobornyl acrylate) (PIBA) was prepared to form a series (denoted the I series), which was compared with the PUs containing free PIBA (denoted the C series). The bulky and rigid bicyclic isobornyl groups attached to the PIBA chains were intended to hinder the molecular interactions between PU chains and improve the low temperature flexibility of the PUs. The soft segment melting temperature (T-m) was not changed by the increase of the isobornyl acrylate (IBA) content; however, the enthalpy change of melting (Delta H-m) sharply decreased. The C series PUs did not exhibit similar differences in response to the IBA content change. The tensile strength of the I series sharply increased at low IBA content due to the physical crosslinking and decreased at high IBA content due to the repulsion between PU chains. The I series demonstrated an improved low temperature flexibility compared with the unmodified and the C series PUs.