Polypropylene Blends and Composite: Processing-Morphology-Performance Relationship of Injected Pieces

A. CONSTANINO; C. ROSALES; V. PETTARIN

Polypropylene

IntechOpen

Año: 2019; p. 1 - 14

Polypropylene (PP) is a plastic commodity, which currently is in a transition zone between massive use and engineer applications due mainly to its limited mechanical properties, such as low tensile and impact resistance. Moreover, several years ago the replacement of conventional materials with lighter ones has attracted the attention of many industries, especially the automotive ones. Replacement of traditional materials is achieved with the development of new composite materials, which meet both the desired properties?mechanical, thermal, esthetic?and a low weight, i.e., high relative properties. These are the main reasons why PP is usually modified with additives and particles to improve its mechanical and thermal performance and thus meet the requirements demanded by engineer applications. Originally, PPs were modified with fillers as talc only to reduce their costs, but currently the purpose is focused on improving properties such as rigidity, strength, toughness, dimensional stability, and even esthetics of PP parts [1]. To achieve this purpose, several particles have been used, such as glass fibers (GF), nanoclay (NC), carbon nanotubes (CNT), and rubber. In a further step, hybrid materials formulated by two or more of these components have been proposed.From an engineering point of view, mixing a polymer matrix with a particle is an effective low-cost way to achieve the required properties when parts are produced by injection molding. However, it is important to understand the way in which particles and processing affect the structure and properties of processed parts. It is important to keep in mind that PP composites? performance depends not only on their intrinsic properties but also on processing conditions. PP is also strongly sensitive to defects produced during manufacturing processes such as injection molding, which deteriorate and decrease a lifetime of composite parts [2]. These defects are even more pronounced in the case of composites. In recent years, a number of texts regarding properties of injection-molded reinforced polypropylenes have been published [3, 4, 5]. However, because of the continuing developments of PP composites, the achievable property values are continuing to improve. In structural and semi-structural applications, particularly, in addition to high stiffness and mechanical strength, adequate fracture toughness is often required. In order to optimize these properties, the knowledge of the relationship between morphology and deformation behavior seems to be essential. The understanding of the fracture, micro-deformation, and mechanics of failure of composites is therefore crucial for engineers. This chapter will summarize the relationship between processing and performance of several PP composite?micro, nano, and hybrid?injected parts aiming to generate a bridge between technologic knowledge and scientist knowledge.