Effects of Low Castor Oil on Mechanical Properties of Polyurethane Foams

Abstract

The polyurethane foam industry in Nigeria depends largely on imported feedstocks based on fossil sources at exorbitant cost and high foreign exchange. Furthermore, emissions from some of these chemicals during processing have been reported to cause negative environmental impact effects and also carcinogenic to both animal and humans. It is for these reasons that this present research explores and exploits alternative nonconventional or supplement local sources of raw materials such as castor oil (CO) for the commercial manufacture of polyurethane foams in our quest for local content development. Mechanically extracted (CO) was characterized for physico-chemical properties such as refractive index, relative viscosity, pH, specific gravity, boiling point and acid, hydroxyl, saponification and iodine values by conventional and titrimeric methods were found to be within the ASTM D 1639 – 90, 1994 standard specifications. IR spectral analysis of the oil shows characteristic absorption bands of hydroxyl, carbonyl and olefinic groups. These results show that CO properties compare reasonably with those of conventional (CPO) and polymer (PPO) polyols. Foam formulations based on CO and various blend compositions with CPO and PPO were investigated for physico-mechanical properties such as density, tensile stress, tensile strain, elongation at break, compression set, and creep recovery (resilience). The results obtained show a critical blend composition at CPO/CO (90/10, % w/w) and PPO/CO (90/10, % w/w). This blend composition displays a good balance of density, tensile strength, elongation at break and creep recovery compared to other blend compositions. It also shows higher values than those of 100% CPO or PPO, for instance, tensile strength at CPO/CO (90%:10%) displayed a value of 11.06N/cm2 as against 6.81 N/cm2 at CPO/CO (100%:0%), while tensile strength value at PPO/CO (90%:10%) showed 9.49 N/cm2 as against 6.03 N/cm2 at 100% PPO. Similarly, values for elongations at break,indicate 49.99mm at CPO/CO (90%:10%) as against 73.98mm for 100% CPO, while at PPO/CO (90%:10%), the value was 37.05mm compared to 44.75mm for 100%: PPO. However, 100% CO shows a low tensile strength of 2.04 N/cm2 with a high elongation at break of 89.95mm. Furthermore, results of creep recovery indicate a value of 30.21% at CPO/CO (90%:10%) compared to 21.52% at 100% CPO, while the corresponding value for PPO/CO (90%:10%) was 25.49% as against 14.65%. for 100% PPO. Similar trends were observed for mechanical testing of factory trials of Iso-block foams.