Mechanical, viscoelastic and gas transport behaviour of rotationally molded polyethylene composites with hard- and soft-wood natural fibres

Rotomolded uncompatibilized composites of LLDPE with softwood and hardwood flour dispersed phases are compared and contrasted with respect to their static (tensile, flexural and impact) and dynamic (creep modelling, storage and loss moduli) mechanical properties and transport (oxygen permeability). The static and dynamic mechanical properties are analysed as a function of dispersed phase weight fraction and pre and post ethanol sorption. Vital structural properties such as the equilibrium modulus, Kelvin Voigt modulus, Kelvin Voigt viscosity and relaxation times along with creep compliance trends are analysed. The interfacial porosity generated is then correlated to the overall gas transport using oxygen as the probe molecule. Two models are compared and it is found that the model of Alter which uses overall density as the modelling parameter, is able to predict composite gas permeability with high accuracy. Overall, owing to the uncompatibilized nature, most mechanical properties reduce with wood flour incorporation independent of the type of dispersed phase. However, these properties remain consistent pre and post ethanol sorption as long as the dispersed phase weight fraction is around 5%. This indicates that with some external scaffolding type support structures, the rotomolded composites have potential for use as storage units for liquid materials.

Automated summary

This study compares and contrasts the mechanical properties, transport characteristics, and adsorption of uncompatibilized LLDPE composites with softwood and hardwood flour dispersed phases in rotational molding. The results show that the addition of wood flour reduces most mechanical properties, but the properties remain consistent pre and post ethanol sorption when the dispersed phase weight fraction is around 5%. It is suggested that with proper support structures, these composites have potential for use as storage units for liquid materials.