Rice husk and saw dust reinforced hybridized blends of bio-benzoxazine/epoxy based composites: Thermal, Mechanical, and Acoustic Absorption Properties

Abstract The prime objective of the present work is to develop bio-wastes (rice husk and saw dust) reinforced composites with varying weight percentages composition of hybridized blend made from bio-based cardanol-melamine, cardanol-aniline benzoxazine and epoxy resin (bio-benzoxazine : epoxy resin 0:100 and 50:50 wt%)for acoustic proof applications. The breakthrough achieved in the present work is the cardanol benzoxazine is made in the form of hybrid matrix with epoxy resin, which cures significantly at lower temperature of 1050C in the absence of any curatives and also cures at room temperature in the presence of isophorone diamine curative,whereas the cardanol-melamine and cardanol-aniline based benzoxazines cure at very high temperature of 221˚C and 275 ˚C respectively. The low temperature cure behaviour achieved in the present work facilitates the amenable fabrication of bio-composites using both low heat resistant bio-based reinforcements and high temperature cure bio-benzoxazines for making cost competitive green building materials. Cardanol-melamine (C-m) and cardanol-aniline (C-a) based benzoxazines were synthesised using cardanol separately with melamine (m) and aniline (a) in the presence of paraformaldehyde under suitable experimental conditions. The benzoxazine (C-m and C-a) obtained was blended with varying weight percentages of bisphenol-A epoxy (DGEBA) resin separately followed by reinforcing with rice husk and saw dust and then cured at room temperature with stoichiometric quantity of isophorone diamine to obtain corresponding hybrid bio-composites. Mechanical properties (tensile strength, modulus, percentage elongation and hardness), thermal conductivity, thermal resistance, and sound absorption coefficient were studied as per standard methods. Results obtained from different studies infer that hybrid blended cardanol benzoxazine composite panels reinforced with rice husk and saw dust possess appreciable thermal, mechanical and acoustic properties. Data obtained from acoustic studies, it was observed that the highest value of sound absorption coefficient of 6400 Hz was noticed for composite specimens developed using both rice husk and saw dust reinforced with hybridized blend of bio-benzoxazine (50wt%) and epoxy resin (50wt%) and these hybrid composite panels can be used as sound absorption material in the ceiling and wall construction applications.