http://hdl.handle.net/2117/3624 2013-05-21T14:03:37Z http://hdl.handle.net/2117/18809 Title: Foamed polypropylene for industrial applications Authors: Sousa Pais Antunes, Marcelo de; Velasco Perero, José Ignacio Abstract: There is a great deal of industrial interest in the development of increasingly lighter materials based on polymer foams with improved specific properties for the most varied purposes, from flexible foams for packaging to rigid ones for structural applications. Due to its good combination of properties and reduced cost, foamed polypropylene (PP) could come as a good option. Depending on the base material, foam density and developed cellular structure and microstructure, PP foams may cover a wide range of characteristics and properties wich, combined with the incorporation of functional fillers, could ultimately result in the development of multifunctional lightweight materials. This chapter presents a review of the most recent developments in polypropylene foams, starting out by the commercially available PP grades thought out for foaming applications, the different types of PP-based foams depending on their characteristics and final uses, from low-density flexible foams for cushioning and packaging to medium-high density foams for structural purposes, and the main industrial foaming processes, going from melt-like foaming to solid state chemical and physical foaming. Recent developments in the field of PP foams are also considered, focusing on the combination of cellular structure control via foaming and the incorporation of micro and nanosized functional fillers, with the ultimate objective of developing PP-based foams with a wide range of properties and unique characteristics, from electrically conductive foams through the incorporation of conductive carbon-based nanofillers to foams with direction-dependent transport properties. 2013-04-15T17:58:18Z http://hdl.handle.net/2117/13491 Title: Essential work of fracture (EWF): a useful tool for the fracture toughness characterization of particulate polyolefin composites Authors: Arencón Osuna, David; Sousa Pais Antunes, Marcelo de; Velasco Perero, José Ignacio Abstract: The characterization of the fracture toughness of polyolefin composites filled with inorganic particles is commonly solved by means of standardized testing procedures based wherther on the Linear Elastic Fracture Mechanics (LEFM) and the Elastic-Plastic Fracture Mechanics approaches. Fracture parameters as Kc, Gc and Jc are obtained and managed as "material" parameters in plain strain conditions. Nevertheless, particulate polyolefin composites are often in form of film or sheet, making difficult to achieve the specimen size criteria for fracture toughness characterization under plain strain conditions. In such cases, the concept os Essential Work of Fracture (EWF) is nowadays being increasingly applied and considered as a reliable way of fracture toughness determination for this kind of composites. The EWF has traditionally been used for fracture characterization of metals and ductile polymers under plain stress conditions, and most recently applied to ductile particulate composites. In the present chapter, the application of the EWF testing method to the particulate polyolefin composites is reviewed analyzed with regard to the variables of the testing method and the composite characteristics, such as the polyolefin nature and its ductility , the reinforcing particle characteristics and concentration, and the interfacial adhesion level, among others. 2011-10-11T17:40:07Z http://hdl.handle.net/2117/13420 Title: Heat transfer in polyolefin foams Authors: Sousa Pais Antunes, Marcelo de; Velasco Perero, José Ignacio; Solórzano Quijano, Eusebio; Rodríguez-Pérez, Miguel Ángel Abstract: This chapter is dedicated to the study of heat transfer in polyolefin-based foams, particularly thermal conductivity, as a function of their structure and chemical composition. A small review of the main experimental techniques used to measure the thermal conductivity of these materials is also given, focusing on the transient plane source method (TPS), as well as different theoretical models commonly used for estimating its value. Alongside cellular structure (cell size, anisotropy, etc) and composition considerations, particular importance is given to the analysis of the presence of micrometric and nanometric-sized fillers in the resulting cellular composite thermal properties. This is a novel research field of particular interest, thought to extend the application range of these lightweight materials by tailoring their conductivity. 2011-10-04T15:28:44Z