Polymers engineering

Polymers such as PA (Nylon) or polyesters are normally predried before compounding operations to prevent degradation by hydrolysis. It will also be necessary to dry the filler before addition to the polymer in compounding. Discolouration of polyacetals after compounding and under service conditions is usually initiated by additives, including antioxidants [21]. 

Polybutylene terephthalate (PBT) is one of the engineering thermoplastic polyesters that offers excellent performance for a variety of applications. Compounding of PBT with PO provides impact modification depending upon the type of PO used and the suitability of the compatibiliser [22-28]. 

The high crystallinity of both PE with PBT, together with differences in processing temperatures makes the penetration of either PE into PBT or vice versa difficult when compounding due to a lack of compatibility between the phases. Use of very low-density polyethylene(s) (VLDPE), having low crystallinity and a narrow MW distribution, may result in better properties [29]. 

Engineering polymers are characterised by high ratings for mechanical, thermal, electrical and chemical properties. Their properties are reproducible and predictable and also retained over a wide range of environmental conditions. Distinct from the high volume/low volume commodity plastics, engineering polymers are in a special category [36]. 

Specialised polymers, which are mainly used in engineering applications in the automobile, aircraft and machinery industries, are known as engineering polymers. In this group, aliphatic polyamides are the most important and most widely used. A large number of aliphatic polyamides are obtained from vegetable oil-based products. Among these nylon 6,10, nylon 11, nylon 6,9 and poly(amido amine) are very important. One of the most important commercially used polymers, nylon 11, is obtained entirely from castor oU, whereas vegetable oil-derived components are only partly used to prepare other polymers. 

2 Preparation of polyfamido amine) from fatly acid. 

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Also, PBT is blended with poly(ethylene terephthalate) (PET), polysulfone, and SMA (303). PET may also be blended with a number of other engineering polymers, such as PC and impact modifiers. 

New product introductions are generally heavily supported by the technical service function. Many customers using chemical feedstocks to produce multicomponent products for the consumer market require extensive on-line evaluations of new raw materials prior to their acceptance for use. An example of this would be the use of a new engineering polymer for the fabrication of exterior automobile stmctural panels. Full-scale fabrication of the part foUowed by a detailed study of parameters, such as impact strength, colorant behavior, paint receptivity, exterior photodurabiHty, mar resistance, and others, would be required prior to making a raw materials change of this nature. 

What is the range of temperature in which Tc lies for most engineering polymers ... 

In this chapter we introduce the main engineering polymers. They form the basis of a number of major industries, among them paints, rubbers, plastics, synthetic fibres and paper. As with metals and ceramics, there is a bewilderingly large number of polymers and the number increases every year. So we shall select a number of "generic" polymers which typify their class others can be understood in terms of these. The classes of interest to us here are ... 

Thermoplastics are the largest class of engineering polymer. They have linear molecules they are not cross-linked, and for that reason they soften when heated, allowing them to be formed (ways of doing this are described in Chapter 24). Monomers which form linear chains have two active bonds (they are bifunctional). A molecule with only one active bond can act as a chain terminator, but it cannot form a link in a chain. Monomers with three or more active sites (polyfunctional monomers) form networks they are the basis of thermosetting polymers, or resins. 

With the expiry of the basic ICI patents on poly(ethylene terephthalate) there was considerable development in terephthalate polymers in the early 1970s. More than a dozen companies introduced poly(butylene terephthalate) as an engineering plastics material whilst a polyether-ester thermoplastic rubber was introduced by Du Pont as Hytrel. Polyfethylene terephthalate) was also the basis of the glass-filled engineering polymer (Rynite) introduced by Du Pont in the late 1970s. Towards the end of the 1970s poly(ethylene terephthalate) was used for the manufacture of biaxially oriented bottles for beer, colas and other carbonated drinks, and this application has since become of major importance. Similar processes are now used for making wide-neck Jars. 

Much trade literature is of a high standard, particularly that of suppliers of the so-called engineering polymers . In many cases these manufacturers supply a range of such polymer types and they provide much useful comparative material. This may be in the form of descriptive material and tables of numerical data. Suitable choice of graphs and other diagrams can often give the reader a more immediately absorbed visual comparison. 

Synthetic fibers such as polyester and acrylic engineering polymers such as acrylonitrile butadiene styrene (ABS) ... 

Montell Polyolefins Polypropylene HPPP, CPPP, Reinforced Polymers, Aesthetic Polymers, CP, HP, Olefinic Polymer Engineering Polymers, Elastomeric... 

Resultant multiphase copolymers displayed properties ranging from soluble thermoplastic elastomers and engineering polymers to intractable thermosets, depending on the backbone composition and orientation, and especially the level of ODA incorpora-... 

Cletir and comprehensive, this volume is not only an informative guide for practitioners in the Held of plastics but also an indispensable aid for plastics engineers, polymer scientists, chemists, physicists, and materials scientists. 

New developments are hydroxylamines and lactones (for processing stability), which operate at an earlier stage during stabilisation. Lactone (benzofuranone) chemistry has been identified as commercially viable, and marks a revolutionary advance in comparison to hindered phenols and phosphites [18]. New lactone chemistry (Figure 10.1) provides enhanced additive compatibility, reduced taste and odour (organoleptics), resistance to irradiation-induced oxidation, and inhibition of gas fade discoloration. The commercial introduction of fundamentally new types of stabilisers for commodity and engineering polymers is not expected in the near future. 

Department of Chemical Engineering, Polymer Materials and Interfaces Laboratory, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 6496... 

Coordination polymerization Can engineer polymers with specific tacticities based on the catalyst system Can limit branching reactions Polymerization can occur at low pressures and modest temperatures Otherwise non-polymerizable monomers (e.g., propylene) can be polymerized Mainly applicable to olefinic monomers... 

The most desirable property of polycarbonates is their high ductility on impact, relative to other engineering polymers in the unmodified state. There is no consensus on the mechanism of ductility researchers continue to explore this behavior through molecular dynamics studies of chain segment motion during the formation of crazes and propagation of the failure. 

Nylons belong to the class of polymers known as engineering polymers that is, they are strong, tough, and heat resistant. We can readily extrude and mold nylons to form a wide variety of useful objects, such as tubing, furniture casters, and automotive air intake ducts. Nylons are commonly spun into filaments or fibers. These can be used directly, or braided, or twisted to form threads, yarns, cords, and ropes, which may be further woven to make fabrics. In their fibrous forms, nylons are used in carpets, backpacks, and hosiery. 

Polyesters exhibit excellent physical properties. They have high tensile strength, high modulus, they maintain excellent tensile properties at elevated temperatures, and have a high heat distortion temperature. They are thermally stable, have low gas permeability and low electrical conductivity. For these reasons, polyesters are considered engineering polymers. 

Engineering polymers are often used as a replacement for wood and metals. Examples include polyamides (PA), often called nylons, polyesters (saturated and unsaturated), aromatic polycarbonates (PCs), polyoxymethylenes (POMs), polyacrylates, polyphenylene oxide (PPO), styrene copolymers, e.g., styrene/ acrylonitrile (SAN) and acrylonitrile/butadiene/styrene (ABS). Many of these polymers are produced as copolymers or used as blends and are each manufactured worldwide on the 1 million tonne scale. 

The terms thermoplastic and thermoset refer to the processability of a particular polymer and the properties of the finished article. Thermoplastic polymers are mostly a linear or branched linkage of monomers containing many thousands of repeat units. All the commodity polymers and most of the engineering polymers are thermoplastic. 

Engineering polymers generally comprise a high performance segment of synthetic plastic materials that exhibit premium properties. In this paper, engineering thermoplastics developed for advanced applications, and particularly for enhanced thermal stability are considered. 

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