Standard thermoplastics

PP is one of the standard plastics. It is largely nonpolar and has a crystallinity of 60 to 70%. The glass transition temperature of PP homopolymers is about 0 °C. Above this temperature the material is tough. 

If not placed under mechanical loading, parts made of PP have a maximum long-term service temperature of about 110 C. A temperature of 140 °C is permissible for 

PP has no inherent flame-retardant properties. High shrinkage means that dimensional stability is poor. This shortcoming can be countered only by using talc-reinforced, mineral-filled, or glass-ball-filled PP for reduced and more isotropic shrinkage. Talc reinforcement reduces heat distortion resistance [8,40, 48]. 

The types highly reinforced with glass fiber can be soldered with all the common soldering processes and even with lead-free solders [8, 40,48). 

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Standard thermoplastic processing techniques can be used to fabricate FEP. Thermal degradation must be avoided, and a homogeneous stmcture and good surface quaUty must be maintained. 

As the author pointed out in the first edition of this book, the likelihood of discovering new important general purpose materials was remote but special purpose materials could be expected to continue to be introduced. To date this prediction has proved correct and the 1960s saw the introduction of the polysulphones, the PPO-type materials, aromatic polyesters and polyamides, the ionomers and so on. In the 1970s the new plastics were even more specialised in their uses. On the other hand in the related fields of rubbers and fibres important new materials appeared, such as the aramid fibres and the various thermoplastic rubbers. Indeed the division between rubbers and plastics became more difficult to draw, with rubbery materials being handled on standard thermoplastics-processing equipment. 

All three types of material have now been available for some years and it is probably also true that none have yet realised their early promise. In the case of the thermoplastic elastomers most of the commercial materials have received brief mention in earlier chapters, and when preparing earlier editions of this book the author was of the opinion that such materials were more correctly the subject of a book on rubbery materials. However, not only are these materials processed on more or less standard thermoplastics processing equipment, but they have also become established in applications more in competition with conventional thermoplastics rather than with rubbers. 

Melt processing is a common alternative that is particularly useful for dealing with thermoplastic polymers and holds great interest because of the ease with which the process could be scaled up to industrial standards. Thermoplastic polyurethane nanocomposites can be fabricated by melt compounding of CNTs with polymer resin. Melt processing makes use of the fact that thermoplastic polymers soften when heated. Amorphous polymers like elastomer... 

Product development and improvement has a crucial role to play in the further development of the biodegradable polymers market. These include development of more reliable and lower cost raw materials for manufacture of biodegradable polymers, improvement in performance properties vis-a-vis standard thermoplastics, improvement in processing performance and development of new polymers and blends. 

Table 4.1 shows the changes in average standard thermoplastic prices for the years 2003-2005 in Western Europe. 

Table 4.1 Average standard thermoplastic prices 2003-2005, Western Europe ( /tonne) ...

During the period 2000 to 2005, world consumption of synthetic biodegradable polymers has increased from 3,900 tonnes to 14,000 tonnes. In 2010, world consumption of synthetic biopolymers is projected to reach 32,800 tonnes. This represents a compound annual growth rate of 18.6% during the period 2005-2010. These forecasts assume that producers are successful in lowering the cost of production and that the price differential between synthetic biopolymers and standard thermoplastics continue to narrow. 

Styrene-butadiene-styrene (SBS) rubbers are either pure or oil-modified block copolymers. They are most suitable as performance modifiers in blends with thermoplastics or as a base rubber for adhesive, sealant, or coating formulations. SBS compoimds are formulations containing block copolymer rubber and other suitable ingredients. These compounds have a wide range of properties and provide the benefits of rubberiness and easy processing on standard thermoplastic processing equipment. 

Relatively cheap materials (graphite and standard thermoplastics)... 

As matrix polymers for the bipolar plate standard thermoplastic and technical polymers can be considered. For the developments at the Fraunhofer ICT polypropylene (PP) was used as a suitable polymer because of its material properties and also its low material price. With a service temperature of 100 °C PP is in the uncritical temperature range for the operating conditions in a PEMFC. 

Research was carried out in commercial laboratories into wholly aromatic polyesters, especially those based on the self-condensation of p-hydroxybenzoic acid, to produce materials of higher potential strength and stability [9-11]. It was found that such homopolymers were extremely refractory materials, and could not be processed by normal techniques used for standard thermoplastics. 

With a pair of such films, the raised embossments are preferably in opposed direction so as to form substantially sealed raised cells with entrained air inside. Of course, such cushioning materials are commercially available made from standard thermoplastic films. 

Polystyrene belongs to the group of standard thermoplastics that also includes polyethylene, polypropylene, and polyvinyl chloride. Because of its special properties, polystyrene can be used in an extremely wide range of applications. 

To conclude, UV-curable fluoropolymeric systems are a very promising alternative to standard thermoplastic materials to easily obtain high-durability coatings to be successfully employed in LSC and light management applications. 

A standard thermoplastic extruder design, built using special materials of construction, with a length to diameter (E/D) ratio of 20 1 to 30 1 can be used to extrude fiuoropolymers. High E/D machines are required to obtain sufficient contact surface area for heat transfer to melt the resin. Eower E/D results in a lower output, and barrel temperatures would have to be raised which can lead to an increase in the polymer degradation. Table 8.4 shows the relationship between diameter, output, and motor size for different extruders. Restriction of flow imposed by the sizing die usually reduces the extruder capacity. 

It is difficult to agree on a precise definition of a high performance plastic. There is indeed a clear overlap across the entire classification spectrum of thermoplastic materials. Some commodity plastics can be modified through reinforcements to compete with traditional engineering resins. Glass fibre-reinforced polypropylene is a good example of a standard thermoplastic material that is challenging polyamide and ABS in many different fields of application. 

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