Highly filled polyethylene/phlogopite composites

Mica is used as reinforcing filler in the polymer industry mainly because of the two-dimensional isotropic nature of reinforcement. Phlogopite and muscovite are under the more common micas with phlogopite found in abundance in South Africa. Phlogopite/linear low-density polyethylene (LLDPE) composites containing 20% and less LLDPE were manufactured to yield a composite with an application area similar to wood composites. The outstanding fire, chemical and heat resistance of phlogopite makes it especially suitable for this application. When modified LLDPE is used as a binder in these composites, the bending modulus reaches a maximum (895 MPa) around 15% polymer. This value is obtained when the LLDPE is modified by compounding it with 10% maleic acid anhydride as adhesion promoter and cross-linking agent. Furthermore, modifications to LLDPE that lead to cross-linking enhance the bending modulus of these composites. The optimum yield strength was found to be 11.5 MPa, also at 15% LLDPE modified with 10% maleic acid anhydride. The other LLDPE modifications tested showed that using less maleic acid anhydride, or irradiating the LLDPE before composite manufacture results in a composite with lower yield strength and bending modulus. (C) 2002 Elsevier Science B.V. All rights reserved.