Wear 270 (2011) 576–583 Contents lists available at ScienceDirect Wear journal homepage: www.elsevier.com/locate/wear Abrasive wear of HDPE/UHMWPE blends Alessandra de A. Lucas a,∗ , José D. Ambrósio b , Harumi Otaguro b , Lidiane C. Costa b , José A.M. Agnelli a a Department of Materials Engineering – DEMa, Federal University of São Carlos – UFSCar, SP, Brazil b Materials Characterization and Development Center – CCDM, DEMa/UFSCar, SP, Brazil article info Article history: Received 6 April 2010 Received in revised form 11 January 2011 Accepted 19 January 2011 Available online 26 January 2011 Keywords: Polymer Abrasion Solid lubricants Wear testing Electron microscopy abstract Blends of high density polyethylene (HDPE) with ultra-high molecular weight polyethylene (UHMWPE) were obtained by mixing in a melted state at concentrations ranging from 10 to 30% by weight in an intermeshing co-rotating twin screw extruder (ICTSE). The abrasive resistance of the blends was eval- uated according to the DIN53516 standard, and it was observed that the volumetric loss of the blends decreased with increasing concentration of UHMWPE. The mechanical properties of the samples were analyzed in terms of flexural, tensile, and impact strength; in general, the HDPE/UHMWPE blends had a good set of properties, most of which were better than the properties of pure HDPE. Thermal analysis of samples was made by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and no significant difference was observed between the blends and pure HDPE. The morphological anal- ysis conducted by scanning electron microscopy (SEM) showed that the UHMWPE is present in the HDPE matrix as a second phase, but there is a good interface between the two. We found an inverse relationship between the volumetric loss in the abrasive wear of the samples and the product between the tensile strength at yielding and strain at yielding,  y ε y , as proposed by Lancaster and Ratner (Sinha and Briscoe, 2009 [1]). © 2011 Elsevier B.V. All rights reserved. 1. Introduction High density polyethylene (HDPE) is a polymer commonly used in pipes for water supply, sewage, and the three-layer coating of steel pipes, with the primary function of protecting the pipes from damage caused by corrosion, transportation, and pipe installation (e.g., impact, bending, and stress). These buried (in humid or dry environments) or underwater (fresh or salt water) pipelines are used for the transport of gas, oil, minerals, and water, among other uses. The temperature range of use varies between 40 and 80 ◦ C [2]. For this purpose, the HDPE that is used must have a good set of prop- erties, such as resistance to abrasive wear, impact resistance, and tensile and flexural strength. Wear resistance becomes an impor- tant factor since the coating is always in contact with sand soil, or with solid particles suspended on water or rubbing against solid particles located at the contact between the surface of the pipe, coated or not, and other surfaces during storage, transportation, installation and usage. HDPE has good flow properties and is widely used in commod- ity markets, as it can be transformed by traditional processes of extrusion, blow molding, injection molding, and rotational mold- ∗ Corresponding author at: DEMa/UFSCar, Rodovia Washington Luis, km 235, São Carlos, SP CEP13565-905, Brazil. Tel.: 55 16 3351 8532; fax: 55 11 3351 8850. E-mail address: alucas@ufscar.br (A.A. Lucas). ing. In addition, it is sold at a low price. Ultra-high molecular weight polyethylene (UHMWPE) has the remarkable properties of excel- lent abrasion resistance, impact resistance, fatigue resistance, and chemical resistance, and it is commonly compared to engineering polymers [3–5]. However, the high molecular weight of UHMWPE (in the range of 3–10 million g/mol) gives it a very high viscos- ity, which prevents its flow in conventional techniques of polymer processing. This is because in practice this material does not flow, thereby limiting its applications. In this context, the mix between these two polymers is a very interesting alternative since it has the potential to combine the excellent properties of UHMWPE and the good processability of HDPE. The basic idea is to add as much UHMWPE to HDPE as possible, taking the advantage of both: the processability of HDPE under conventional techniques and the outstanding wear and mechanical performance of UHMWPE. For extrusion, for example, the viscosity of the blends will be a limitant factor. These blends have been extensively studied recently [3–14], which adds to the knowledge of various aspects of the behavior of UHMWPE under abrasion and wear in various conditions, especially for applications such as biomaterials in orthopedic implants. Abrasive wear is caused by hard asperities on the counterface and/or hard particles that move over the polymer surface. This mode of wear occurs when the roughness is the determinative parameter in friction [1]. Abrasion results in scratches, gouges, and scoring marks on the worn surface. The phenomenon that controls the resistance of plastics is not yet fully understood. The classic 0043-1648/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.wear.2011.01.011