32. Influence of Crumb Rubber Reinforcement on the Properties of Medium Density Fiberboard

Recycling of scrap tires in the form of crumb rubber is one way to address the environmental concern of tire disposal. In this investigation we have utilized crumb rubber to reinforce medium density fiberboard (MDF). For the purpose of comparison, a baseline MDF material is prepared by mixing polypropylene pellets and wood flour in the ratio of 1:2 by weight using a double helical screw mixer at 165 ^∘C. The crumb rubber reinforced MDF (CR–MDF) material is prepared by adding crumb rubber particles of a size between 1.2 to 1.4 mm, into to the polypropylene pellets and wood flour mixture. Subsequently, the prepared samples are molded into the desired dimension using a hot press. The bulk density of CR–MDF materials is found to be 19% higher than the baseline MDF samples. This indicates that crumb rubber assists in the consolidation process. Prepared MDF and CR–MDF specimens are mechanically characterized as per ASTM D 1037. Compressive modulus of CR–MDF shows an increase of 200%, as compared to baseline MDF. With the addition of crumb rubber, flexural modulus and flexural strength of the MDF samples are improved by 120% and 75%, respectively. Scanning electron microscopy (SEM) on failed CR–MDF samples indicates extensive tearing of crumb rubber particles which suggests that particle bridging is the dominant strengthening mechanism. In addition, water immersion experiments show that the presence of crumb rubber improves the resistance to moisture absorption. Finally, Fourier Transform Infrared Spectroscopy (FTIR) of CR–MDF samples indicates sulfur–sulfur bonds and the CN group from the nitrile component of the crumb rubber.