Evaluation of the morphology, mechanical and thermal properties of cork and green polyethylene ecocomposites

Abstract

Ecocomposites of green high-density polyethylene, natural cork powder and coupling agent were developed with the objective of investigating the potential of these materials for application in civil construction. The cork and the compatibilizer functionalized with maleic anhydride were incorporated into the polymer matrix by means of a twin screw co-rotating extruder. The composites obtained were molded by injection and evaluated morphologically by scanning electron microscopy, thermal and mechanical performance through thermogravimetry and under tension test, respectively. The morphological analysis indicated that the cork incorporation reduced the deformation, which was attenuated in the samples treated with coupling agent and, despite the existence of voids and agglomerates, it was possible to observe good dispersion of the cork in the thermoplastic matrix. The modulus of elasticity of the composites did not change significantly with the incorporation of the vegetal reinforcement, presenting values close to the pure matrix; when the treated samples showed a small reduction of this property. In relation to the breaking stress, the sample GHDPE/5CP presented greater value among the proposed ecocomposites. The yield stress of the ecocomposite containing 5% of cork presented a similar result to that of the pure GHDPE matrix. However, the composites with 10 and 15% of cork had reduction of this property. The use of coupling agent promoted the increase of this property for the ecocomposites, due to a higher interfacial adhesion between filler and matrix. Thermal degradation analysis confirmed that cork is thermally stable at processing temperatures of polymeric composites (200 °C) and that the incorporation and increase of the cork content slightly reduced the thermal stability of the ecocomposites in relation to the matrix. The results showed that the use of cork particles and compatibilizer in the production of sustainable materials could be an alternative to develop products for non-structural applications in construction.