EFFECT OF FILLER TREATMENT ON THE RHEOLOGICAL AND MECHANICAL PROPERTIES OF POLYETHYLENE COMPOSITES

Abstract

Mechanical and Theological properties of a high density polyethylene (HDPE) filled with mica flakes, rutile and carbon black are investigated. Experimental results show that the Young modulus and the tensile strength of mica and rutile-HDPE composites are significantly enhanced by surface treatment of fillers with silane and titanate coupling agents. Surface treatments are shown to reduce the peak of the loss tangent (tan δ) and slightly increase the glass transition temperature (T _g). This is an indication of improved adhesion at the filler-matrix interface. The carbon black composites, however, hardly show any improvement by these treatments. The Theological properties are also effected by surface treatments, particularly at low shear rates. The low-shear rate viscosities (η _O) and characteristic time (λ ₀) of these systems are determined and compared. It is found that η ₀ and λ ₀ of carbon black composites are much higher than those of mica composites. This is probably due to the poor dispersion and/or agglomerates formation of the carbon black in the HDPE matrix. It is also suggested that the coupling agent, depending on its chemical structure and nature of the filler, may act as an adhesion promoter or as a lubricating agent.

KEYWORDS:

• Thermoplastic composites
• Coupling agents.