Mechanical and permeation properties of HDPE/organoclay composites with improved petroleum swelling behaviour

VALERIA PETTARIN; LAURA FASCE; STELLA MOSCHIAR; VICTOR PITA; MARCOS LOPES DIAS; PATRICIA FRONTINI

Buenos Aires, Argentina

Conferencia; 3rd International Conference on Science and Technology of Composite Materials COMAT 2005; 2005

Composite materials are increasingly used in the oil and gas industry instead of conventional carbon steel for pipeing and fuel tanks manufacturing. The main reason is their better corrosion resistance. The overall barrier performance to low molecular weight penetrants are of crucial importance for these materials. As thermoplastics can satisfy these demands, several types of reinforced thermoplastic systems are currently under development. The use of polymer-layered silicate nanocomposites containing low levels of exfoliated clays has increased as one of the most important areas for the reinforcement of polymeric materials. Melt processing is often preferred because it minimizes capital costs due to its compatibility with existing processes. The objective of this work was to prepare polyethylene/(organo-montmorillonite) nanocomposites with improved petroleum and fuel swelling behaviour by melt compounding. Three different Na+-montmorillonites – a Wyoming Bentonite, a Brazilian clay, and an Argentinean montmorillonite – were modified with a quaternary alkyl ammonium salt in order to obtain organoclays. Five composites were prepared with 3%wt of organoclay and two grades of high-density polyethylene: a blow grade, and a pipe grade, in a twin screw extruder. The extent of clay exfoliation in the composites was determined by X-ray diffraction (XRD). Even if both PE matrixes were not chemically modified, exfolliation of the organoclay was achieved in most cases. The mechanical behaviour of composites was studied by uniaxial tensile experiments and biaxial impact tests (puncture). Tensile modulus, yield strength and impact strength of PE matrixes were influenced by the reinforcement giving place to an overall better mechanical performance. Relative petroleum uptake was experimetally determined and the derived diffusion coefficients of polyethylene composites were calculated. In these experiments petroleum was simulated by a mixture of n-hexane and toluene.. Results showed that composites are less sensitive to organic low molecular weight penetrants.