Properties of Polymer Composites with Cellulose Microfibrils

Denis Mihaela Panaitescu, Adriana Nicoleta Frone, Marius Ghiurea, Catalin Ilie Spataru, Constantin Radovici and Michaela Doina Iorga

National Institute of Research and Development in Chemistry and Petrochemistry

Romania

1. Introduction

Plastic materials are indispensable in our lives but they are an important source of environmental pollution. In order to reduce the environmental load generated from the disposal of used plastic materials, a growing interest has been focused on biodegradable polymers based materials. These polymers can be completely converted into water and carbon dioxide by the action of microorganisms after disposal.

Owing to their good mechanical properties, polymer composites with micro or nano cellulose fibers are promising substitutes for glass-fiber-containing composites in many industrial fields like automotive, construction, electronics, biomedicine, cosmetics, and last but not least, the packaging industry. Among the advantages of using cellulose fibers as reinforcements in polymer composites renewability, low cost, low density, low energy consumption, high specific strength and modulus, high sound attenuation, low abrasivity and relatively reactive surface are the most important. Cellulose fibers modified at nanometer size induce much higher mechanical properties to polymer matrices as regard to common cellulose fibers because of their higher crystallinity and mechanical properties combined with higher surface area and better interfaces.

The production of nano-scale cellulose fibers and their application in composite materials has gained increasing attention in the past two decades (Hubbe et al., 2008). Two main methods have been used to generate nano-scale cellulose fibers: the chemical way, mainly by strong acid hydrolysis, which removes the amorphous regions of cellulose fiber and produces nano-size fibrils and the mechanical method, by high pressure refiner treatment (Chakraborty et al., 2005), grinder treatment (Taniguchi and Okamura, 1998), microfluidizer (Zimmermann et al., 2004), and high-pressure homogenizer treatment (Istvan and Plackett, 2010).

In this chapter the discussion is focused on the physical and mechanical properties of polyvinyl alcohol (PVA) as a biodegradable matrix reinforced with three types of cellulose fibers prepared by different methods. This chapter will first discuss the most used methods for cellulose nanofibers preparation and the reinforcing effect of these cellulose fibers in different polymer matrices. This will be followed by the experimental results obtained in our laboratory on PVA composites prepared with cellulose fibers isolated by mechanical treatment, acid hydrolysis and ultrasound treatment. The isolated cellulose fibers were

characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) and PVA composites, prepared through film casting method, by XRD, thermal analysis and mechanical characterization.