Performance of biocomposites from surface modified regenerated cellulose fibers and lactic acid thermoset bioresin

Abstract

The effect of surface treatments, silane and alkali, on regenerated cellulose fibers was studied by using the treated fibers as reinforcement in lactic acid thermoset bioresin. The surface treatments were performed to improve the physico-chemical interactions at the fiber-matrix interface. Tensile, flexural and impact tests were used as indicator of the improvement of the interfacial strength. Furthermore, thermal conductivity, viscoelasticity measurements as well as microscopy images were made to characterize the fiber surface treatments and the effect on adhesion to the matrix. The results showed that silane treatment improved the mechanical properties of the composites as the silane molecule acts as link between the cellulose fiber and the resin (the fiber bonds with siloxane bridge while the resin bonds with organofunctional group of the bi-functional silane molecule) which gives molecular continuity in the interphase of the composite. Porosity volume decreased significantly on silane treatment due to improved interface and interlocking between fiber and matrix. Decrease in water absorption and increase in contact angle confirmed the change in the hydrophilicity of the composites. The storage modulus increased when the reinforcements were treated with silane whereas the damping intensity decreased for the same composites indicating a better adhesion between fiber and matrix on silane treatment. Thermogravimetric analysis indicated that the thermal stability of the reinforcement altered after treatments. The resin curing was followed using differential scanning calorimetry and the necessity for post-curing was recommended. Finite element analysis was used to predict the thermal behavior of the composites and a non-destructive resonance analysis was performed to ratify the modulus obtained from tensile testing. The changes were also seen on composites reinforced with alkali treated fiber. Microscopy images confirmed the good adhesion between the silane treated fibers and the resin at the interface.

End-Of-Life Textiles as Reinforcements in Biocomposites

“…5). T g obtained from DMTA was slightly higher than that of T g from DSC, and a similar trend was noticed in our previous research [20]. This was mainly due to DMTA sensitivity towards the glass transition temperature.…”

“…This was interesting as it revealed that the cellulose degradation in the reinforcement shifted on alkali treatment. Similar trends were obtained from the composites produced from regenerated cellulose fibres [20]. …”

“…Figure 3 shows the TGA curves of the composites from different resins with 50% reinforcement, and all the composites behave in the same manner. The resins and the composites were relatively stable up to 300 °C, while the addition of reinforcement to the resins changed the thermal stability slightly as anticipated [20].…”

“…This was studied and reported in later in this article. Alkali treatment on cellulose fibres was studied in detail in our former studies [12,20].…”

“…Storage modulus of the cured resin corresponds to the polymer chain packing density in the glassy state. The movements of the chain segments are restricted due to high cross-linking density [20].…”