(98j) Room Temperature Shape Memory Polymers
Temperature controlled shape memory polymers can be synthesized via a facile method using long chain fatty acid and cross-linked natural rubber. For this experiment, rubber was swollen in liquid stearic acid (75 °C). Different weight percent loadings of acid were achieved by differing swelling times in one hour increments from 1 hour to 5 hours. The normal shape memory cycle consist of increasing the temperature of the swollen polymer above the melting point of the acid, stressing the polymer, then immediately quenching the heat in room temperature water. The rubber will hold stress without relaxing until heated above the melting point of stearic acid again, thus returning the rubber to its original state. Obtaining shape memory behavior at temperatures lower than 75 °C is desirable to mitigate safety concerns and reduce heating required, improving process economics. Investigation of the room temperature shape memory behavior was conducted through modifying the shape memory cycle. It was found that stearic acid swelled natural rubber exhibits a 30% fixity over a 24 hour period. The stress can be relaxed by heating the swelled rubber above the melting point of stearic acid.