Cellulose-polymer composites mechanical properties

J.M. Felix, P. Gatenholm, and H.P. Schreiber. Controlled interactions in cellulose-polymer composites. 1 effect on mechanical properties. Polym. Composites, 1993, 14(6), 449-457. 

Felix JM, Gatenholm P. 1993. Controlled Interactions in Cellulose-Polymer Composites. 1 Effect on Mechanical Properties. Polym Composite 14(6) 449 57. 

Electric discharge methods are known [31] to be very effective for nonactive polymer substrates such as polystyrene, polyethylene, polypropylene, etc. They are successfully used for cellulose-fiber modification to decrease the melt viscosity of cellulose-polyethylene composites [32] and to improve the mechanical properties of cellulose-polypropylene composites [28]. 

The mechanical properties of composites reinforced with wood fibers and PVC or PS as resin can be improved by an isocyanate treatment of those cellulose fibers [41,50] or the polymer matrix [50]. Polymethylene-polyphenyl-isocianate (PMPPIC) in pure state or solution in plasticizer can be used. PMPPIC is chemically linked to the cellulose matrix through strong covalent bonds (Fig. 8). 

The results of mechanical properties (presented later in this section) showed that up to 20 phr, the biofillers showed superior strength and elongation behavior than CB, cellulose being the best. After 30 phr the mechanical properties of biocomposites deteriorated because of the poor compatibility of hydrophilic biopolymers with hydrophobic natural rubber(results not shown). While increasing quantity of CB in composites leads to constant increase in the mechanical properties. Scanning electron micrographs revealed presence of polymer-filler adhesion in case of biocomposites at 20 phr. 

Fig. 17. Effect of interdiffusion of the functionalized polymer with the matrix on the mechanical properties of PP/cellulose composites. Molecular weight of MA-PP (O) non-treat-ed, (A) 350, (V) 4500, ( ) 3.9X10 ...

By analogy with the works which dealt with cellulose micro crystal-reinforced nanocomposite materials, microcrystals of starch [95] or chitin [96, 97] were used as a reinforcing phase in a polymer matrix. Poly(styrene-co-butyl acrylate) [95,96], poly(e-caprolactone) [96], and natural rubber [97] were reinforced, and again the formation of aggregates or clustering of the fillers within the matrices was considered to account for the improvement in the mechanical properties and thermal stability of the respective composites processed from suspensions in water or suitable organic solvents. 

Various reports are present in the literature on the usage of cellulose fibers in the preparation of composites. Cellulose fibers like banana, sisal, oil palm, jute, pine apple leaf fiber were found to have a very good reinforcing effect on polymer matrices [38 2]. The mechanical properties and water absorption were found to be dependent on the amount of micro-fibrils. 

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