Characterization of thermoplastic polyurethane elastomer coated pineapple leaf fiber

Abstract

Pineapple leaf fibers (PALFs) have several advantages such as low cost, ecofriendly and high specific strength but their brittleness limit the application. To overcome this limitation, PALFs were coated with thermoplastic polyurethane elastomer (TPU) to enhance their elasticities and flexibilities. TPU was synthesized using a two-stage route method which consists of polyurethane (diisocyanate react with polypropylene glycol), forming pre-polymer (polyurethane with short chain), and to increase the chain length, chain extender was added into pre-polymer. Prior to this coating, PALFs were treated with sodium hydroxide at 5% concentration to improve their surface areas of the PALF. Three parameters were varied during the preparation of TPU coated PALF which were dipping times (5 min, 10 min, 15 min and 20 min), curing temperatures (30 °C, 55 °C, and 85 °C) and curing times (6, 12 and 24 hours). From scanning electron microscope it was found that sample with 10 minutes dipping time showed a clean and rough surface which favorable for coating with TPU. These were supported by tensile strength that showed sample with 10 minutes high in modulus around 900 MPa with 30% elongation at break. The formation of hydrogen bonding was thought contributed to the increase as shown by the plots of Fourier Transform Infrared at 3300 cm-1 and at 1530 cm-1 indicates PALF fully coated with TPU. Thermal analysis has been studied by using differential scanning calorimetry. The existence of hydrogen bonding had increased the thermal stability as measured with thermogravimetric analysis at around 500 °C of end set temperature. It was found that there is a formation of hydrogen bonding between PALF and TPU. The optimum requirement of TPU coated PALF were 10 minutes dipping time at 85 °C curing temperature and for 6 hours curing time in order to enhance the elasticity and flexibility of the fiber due to their brittleness. As a conclusion, coated PALF with TPU with optimum condition have improved the properties of an elastic yarn.