Biocomposites of Cellulose Acetate Butyrate with Modified Hemp Cellulose Fibres Sirisart Ouajai, Robert A. Shanks * Introduction Interest in composite manufacture has recently shifted towards the use of natural fibres for reinforcement because of their environmental benefits. Biodegradable cellulose-based polymer composites are receiving increased attention due to material availability and sustainability. Good modulus, strength and biodegrad- ability of composites are desirable for embedded reinfor- cing fibres and the selected matrix. The use of a biodegradable matrix merits consideration, since this will result in completely biodegradable composites. The matrix phase is crucial for the performance of polymer compo- sites. Thermoplastic matrix composites provide low processing cost, design flexibility and ease of moulding for complex parts. [1] The selection of suitable thermoplastic biopolymer matrices for cellulose-fibre-reinforced composites is vital. Several aspects are of concern. The biodegradable polymer can be made from petroleum feed stocks; for example: polyester-amide (Bayer BAK polymer), polycaprolactone (PCL) and Dupont Biomax copolyester. [2] The matrix can be derived from renewable resources, such as poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB), providing ready degradation by hydrolysis. These polymers can provide suitable composite density, mechanical properties and temperature related properties, [3] although the slow crystallisation and brittleness of PHB impact on proces- sability. Copolyesters of PHB and poly(3-hydroxyvalerate) (PHV) provide increased flexibility. High cost has limited PHB and its copolyesters from commercialisation. Cellu- lose is becoming a favoured matrix material because of its availability and sustainability, and the price of cellulose esters is lower than that of PLA and PHB copolymers. A variety of cellulose ester derivatives are obtained by controlling the degree of substitution (DS). The most common commercial cellulose esters are cellulose acetate (CA), cellulose acetate propionate and cellulose acetate butyrate (CAB). Their composite mechanical properties are potentially comparable with polypropylene composites. [4] Full Paper S. Ouajai King Mongkut University of Technology, North Bangkok (KMUTNB), Thailand R. A. Shanks Applied Sciences, RMIT University, GPO Box 2476V, Melbourne, 3001, Australia E-mail: robert.shanks@rmit.edu.au Cellulose acetate butyrate biocomposites, plasticized with tributyl citrate at volume fraction V f ¼ 0.1–0.3, were prepared with modified hemp. Inclusion of modified hemp fibres at V f ¼ 0.4 enhanced the modulus and strength of the flexible plasticized cellulose acetate butyrate. Composites containing pectate lyase enzyme treated fibres showed a modulus greater than untreated or alkali treated fibres, when compared at a similar fibre length of 100 mm. Composites containing the shortest alkali treated fibres of 45 mm gave the greatest prop- erty improvement, while 500 mm fibres showed wor- sened properties. Ball-milled fibres provided reduced values of properties due to cellulose structural disrup- tion, while compression moulding gave better compac- tion by removing voids. Macromol. Mater. Eng. 2009, 294, 213–221 ß 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim DOI: 10.1002/mame.200800266 213