There is increasing awareness and pressure to reduce formaldehyde (and other toxic) based emissions from wood panel boards in indoor environments. A new technique was developed to make highly loaded (up to 90 %) formaldehyde free natural fiber boards. In these materials, linear thermoplastic polymer chains act as an adhesive and the product resembles a typical wood based panel (e.g., phenol formaldehyde fiber board). The process involved the use of small amount of glycerine in the fiber to enhance processibility in a thermo-kinetic mixer followed by hot pressing at 190 °C. It is likely that the glycerine acts as a plasticizer and the key appears to be the increase in the mobility of the amorphous polymers such as hemicellulose and lignin.
Maleated polypropylene (MAPP) was used to improve the adhesion and stress transfer between the adhesive and kenaf (lignocellulosic) fiber. A combination of a high melt index (low molecular weight) and high anhydride content of the MAPP resulted in the best panel properties. The effect of mold pressure, polymer type and compatibilizer chemical characteristics on panel properties will be reported. DMTA spectra of the panel boards will also be presented. In this paper, we report the flexural properties of 85 % by weight kenaf fiber boards using polypropylene as the adhesive and maleated polypropylenes as the compatibilizer. The effect of pressure and compatibilizer chemical characteristics along with other parameters on panel properties is reported. It is anticipated that any thermoplastic polymer can be used as long as the processing temperature is lower than the degradation temperature of the lignocellulosic fiber. However, a significant amount of research needs to be done before these new materials can be commercialized. If successful, these new materials could be used in many indoor furniture products. New polymers such as ABS and SBS copolymers could also be used for application such as high toughness.
Keywords: natural fiber composites, highly filled systems, formaldehyde free boards, kenaf panel boards
Authors
Sanadi A.R.
Department of Geosciences and Natural Sciences (IGN), Biomass Science & Technology Group, University of Copenhagen, Frederiksberg, Denmark
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