Effects of silicon carbide whisker on shape memory polymers from benzoxazine- epoxy binary systems

Abstract

Recovery stress enhancement is one of the major research topics in shape memory polymers. One simple and practical way of enhancing recovery stress in SMPs is by making a reinforced composites using suitable reinforcing agent such as carbon nanotube or silicon carbide whisker. This research aims to study effects of silicon carbide whisker (SiCw) on thermal, mechanical and shape memory properties of benzoxazine-epoxy SMPs particularly on recovery stress enhancement. The composition of SiCw-filler in benzoxazine-epoxy SMPs is in a range of 5 to 20wt%. The SiCw-filled benzoxazine-epoxy shape memory polymer was compression molded at 170oC, and pressure of 10MPa for 3 hours. The experimental results reveal that glass transition temperature of the composite samples increases with increasing SiCw contents. The maximum glass transition temperature of benzoxazine-epoxy SMPs is 170oC at 20wt% of the filler. The flexural modulus and flexural strength at room temperature of the SMP samples are found to be 8.1 GPa and 178.0 MPa, respectively and those values of the SMP samples at rubbery stage are determined to be 174.1 and 10.9MPa, respectively. From shape memory test, benzoxazine-epoxy SMPs exhibit about 99% of shape fixity. The recovery time of benzoxazine-epoxy SMPs is in a range of 8 to 27 minutes. Furthermore, the incorporation of SiCw in benzoxazine SMPs provides outstandingly high recovery stress up to 11.2MPa of benzoxazine-epoxy SMPs at 20wt% of the SiCw. Recovery time of benzoxazine-epoxy shape memory composites under microwave heating is significantly shortened to be in a range of 3 to 5 minutes. These results suggest potential use of these materials as microwave responsive sensors and other medical devices.