Polymers alloys, blends and composites

The automotive industry started to use plastics in 1946. Since then, its content steadily increases (see Figure 16.4). Today, the plastics for automotive apphcations are dominated by polymer alloys, blends, and composites. The reason for it is the need for automotive parts to show a wide range of performance characteristics that are virtually impossible to meet using a single-component polymer. Thus, for example, in Saturn, front fenders and rear quarter panels are from PA/PPE, door outer skins are from PC/ABS, the bumper fascias are TPO, etc. 

At present, polymer alloys, blends, and composites consume over 80 wt% of all plastics. 

At present, polymer alloys, blends, and composites consume over 80 wt% of all plastics. In addition, the polymer blends segment of the plastics industry increases about three times faster than the whole plastics industry. Blending has been recognized as the most versatile, economic method to produce materials able to satisfy complex demands for performance. By the year 2000, the world market for polymer blends is expected to reach 51 million tons per annum, worth well over US 200 billion. The tendency is to offer blends that can be treated as any other... 

Polymer Alloys, Blends, and Composites. The fatigue behavior of multicomponent poljuners can be complex. On one hand, the addition of inhomogeneities produces stress concentrations that can reduce the fatigue life of a structure dramatically. On the other hand, the heterogeneities may provide mechanisms of reinforcement, enhanced energy dissipation, or other features that may dramatically improve the overall fatigue life of a material (see Polymer Blends). 

Breakthroughs made possible by advances In alloying, blending and composites technology included supertough nylons, acetals and polyesters from Du Pont. Technologies such as these have eneO>led polymer producers to tailor properties to the specific requirements and preferences of customers in an increasingly competitive business environment. 

Use of polymer alloys and blends as matrices for composites, reinforcements, and foams. 

ABS Three-component copolymer of acrylonitrile, butadiene, and styrene, alloy Rubber-toughened materials in which the matrix can be a mixture of polymer tyrpes. alternation copolymer Ordered copolymer in which every other building is a different mer. azeotropic copolymer Copolymer in which the feet and composition of the copolymer are the same, blends Mixtures of different polymers on a molecular level may exist in one or two phases, block copolymer Copolymer that contains long sequences or runs of one mer or both mers. 

In the area of specialty polymers, we are seeing an explosion of new polymer blends, alloys, and composites. The properties of novel polymer alloys, for example, are significantly better than those of the materials from which they are blended, but many aspects of these alloys are not well understood. Most of the materials consist of multiple polymer phases. But there is still uncertainty as to the desired characteristics and size of the polymer domains and the mechanisms by which forces are transferred through the material. All of these questions will benefit from the chemical engineering approach. 

From the point of view of the applicability of the iso-free-volume concept, it is of great interest to test it for some systems more complicated than simple polymeric liquids, despite the fact that, as we have already shown, this concept has failed in many cases even for simple polymers. The more complicated cases considered are compositions and polymeric blends and alloys. 

At low concentration of the second polymer, blends have dispersed-phase morphology of a matrix and dispersed second phase. As the concentration increases, at the percolation threshold volume fraction of the dispersed pase, ([) = 0.16, the blends structure changes into co-continuous. Full co-continuity is achieved at the phase inversion concentration, ( ). The morphology as well as the level of stress leads to different viscosity-composition dependencies (for more details see Chapter 7. The Rheology of Polymer Alloys and Blends ). 

Handbook of Polypropylene and Polypropylene Composites, edited byHanitun G. Katian Polymer Blends and Alloys, edited by Gabriel 0. Shonaike and George P. Simon Star and Hyperbranched Polymers, edited by Munmaya K. Mishra and Shiro Kobayastv Practical Extrusion Blow Molding, edited by SamuelL. Belcher... 

These materials, known as polymer blends or polymer alloys (see Table 1.3), are generally prepared by mixing two or more thermoplastics. They combine, in an advantageous manner, the properties of the thermoplastic components, and in some cases, the properties of the blends are superior to those of the individual components. (Polymer mixtures also result from the recycling of mixed plastics which have to be identified before they can be reused.) Because of the large number of possible blend components, and the fact that usually so-called compatibilizers of often rather complicated chemical composition are present, a complete analysis of polymer blends is not possible with simple methods. However, by means of some screening tests and selected special tests, one can at least obtain qualitative information about the main components of such systems. 

A miscible polymer blend is one for which the miscibihty and homogeneity extend down to the molecular level, so that there is no phase separation. An immiscible blend is one for which phase separation occurs, as described in the next section. An immiscible blend is called compatible if it is a useful blend wherein the inhomogeneity caused by the different phases is on a small enough scale not to be apparent in use. (Blends that are miscible in certain useful ranges of composition and temperature, but immiscible in others, are also sometimes called compatible blends.) Most blends are immiscible and can be made compatible only by a variety of compatibilisation techniques, which are described in section 12.2.4. Such compatibilised blends are sometimes called polymer alloys. 

Computer controls design Polymer blends, alloys and composites Plastics Compounding Total Quality Control Polymer Chemistry Physics... 

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