ABSTRACT
Polymer blends are generated by the mixing of two or more polymers together in order to combine the characteristics of individual polymers. The compatibilization of the phases in the blends is also achieved by a number of physical (e.g., addition of compatibilizers viz. polyethylene-co-maleic anhydride) or chemical (e.g., chemical reactions with the phases for chemical linking) means. Polymer blends are widely used materials in the modern polymer industry owing to their wider range of properties as compared to individual polymers and ease of tailoring of properties. As a result, polymer blends †nd applications in numerous †elds such as adhesion, colloidal stability, and design of composite and biocompatible materials [1]. The dispersed phase in certain systems can also acquire a speci†c morphology bene†cial for applications like platy morphology, useful for barrier applications. Both solution as well as melt mixing techniques to generate the polymer blends have found their application, though melt mixing is more environmentally friendly as no solvent is required. On the other hand, melt mixing required the use of high temperature and shear for the generation of blends, which may degrade the heat-sensitive polymers, therefore requiring optimum use of mixing conditions. The studies on the polymer blends have signi†cantly increased
CONTENTS
1.1 Introduction ....................................................................................................1 1.2 Functional Polymer Blends: Examples .......................................................3 References ............................................................................................................... 24
in number in recent years leading to generation of further functional blend systems with superior properties. Both miscible and immiscible blends have been studied along with new pathways to achieve compatibilization of the phases in immiscible blends. Some of these developments have been discussed in the following paragraphs. As an example, Figure 1.1 shows polyvinyl chloride/polymethyl methacrylate (PVC/PMMA) blends with varying amounts of components and the resulting effects on the strength and transparency of the generated blends [2]. The change in morphology as well as strength and transparency are observed by changing the composition of the blend constituents. The PMMA is observed to form †nely dispersed particles of 300 to 400 nm in diameter at low concentrations in the PVC matrix. However, when PMMA is the continuous phase and PVC is the dispersed
phase, the PVC domains are much bigger in size. The strength was observed to increase with increasing PMMA concentration until 70% to 80% after which a sharp decrease was observed. The transparency, on the other hand, decreased at different rates with increasing PMMA content until 70% after which it increased sharply indicating a strong relation between the morphology and the properties.
