Expensed engineering

Phenolics are consumed at roughly half the volume of PVC, and all other plastics are consumed in low volume quantities, mosdy in single apphcation niches, unlike workhorse resins such as PVC, phenoHc, urea—melamine, and polyurethane. More expensive engineering resins have a very limited role in the building materials sector except where specific value-added properties for a premium are justified. Except for the potential role of recycled engineering plastics in certain appHcations, the competitive nature of this market and the emphasis placed on end use economics indicates that commodity plastics will continue to dominate in consumption. The apphcation content of each resin type is noted in Table 2. Comparative prices can be seen in Table 5. The most dynamic growth among important sector resins has been seen with phenoHc, acryUc, polyurethane, LLDPE/LDPE, PVC, and polystyrene. 

In a steel product manufacturing plant involving acid pickling operation, disposal of hazardous metal sludge is the most expensive engineering task, and treatment of pickling liquor and rinse water is the second most expensive engineering task. 

Figure 2.17 shows that the cost per volume of the commodity thermoplastics is intermediate between steel and aluminium, which explains their development in packaging and the poor penetration of the much more expensive engineering thermoplastics. 

Applications that are currently being implemented include use in electric transmission bottlenecks and in expensive engine systems such as those found in submarines. 

For performance under severe conditions, they compare very favorably with more expensive engineering thermoplastics as shown in Table 15.17. 

Aluminum is an excellent conductor of electricity. Silver and copper are better conductors than aluminum but are much more expensive. Engineers are looking for ways to use aluminum more often in electrical equipment because of its lower costs. 

Reactor TPOs, reportedly offering better combination of toughness and stiffness, are gaining increasing penetration into the automotive market, in both the soft bumper fascia applications as well as other rigid applications replacing the more expensive engineering resins. 

The development of polypropylene copolymer multiphase systems is continuing at a robust pace. These polymer systems, based on simple and inexpensive polymer budding blocks, are being improved for applications historically reserved for more expensive engineering thermoplastics. The understanding of the structure/property relationships in polypropylene copolymers will indeed be a driver for further innovation in the commercial application of these polymers. 

The high-heat capability, low combustion ratings, and resistance to grease- and oil-induced cracking have made CPVC a strong contender for applications in automotive interiors. With its combination of excellent properties of PVC and the added ability to perform at elevated temperatures, CPVC is beginning to penetrate markets formerly dominated by metals or the more expensive engineering polymers. 

In most processes, for either small or large production runs, the cost of the plastics used compared to the total cost of production in the plant may be at least 60 percent. The proportion might be only 30 percent, but it is more likely to exceed 60 percent so it is important to handle material with care and to eliminate unnecessary production problems and waste. Where small-quantity users or expensive engineering resins are concerned, containers such as bags and gaylords are acceptable but for large commercial and custom processors, these delivery methods are bulky and costly. Resin storage in this form is also expensive. 

Mixtures of two thermoplasts are also known as polymer alloys. They are produced in order to improve the impact strength, the frictional wear, and/ or the processability of bulk plastics in an economic manner. Thus, polymer alloys fill the gap between economic commodity plastics and the expensive engineering plastics. 

The four major thermoplastics—polyethylene, polypropylene, PVC, and polystyrene—together represent over 85% by volume of world plastics consumption. Because of their lower prices, these commodity materials dominate the market, and in any materials selection procedure there are good economic reasons for considering them first before turning to the more expensive engineering plastics. 

Blends constitute about a third of all the world s polymer consumption. They offer a good balance of technical properties or the motive may be economic, as when a cheap commodity polymer is added to a more expensive engineering polymer to reduce costs. Incorporating an impact modifier in a brittle polymer also creates a blend. Finally, recycled post-consmner waste often consists of a blend of one polymer contaminated and weakened by another. 

This concept is essentially different from the concepts of the reactors currently in operation and under development in its radically new approach to safety. Instead of addition of expensive engineered features and systems, safety rehes mostly on fundamental natural behavior patterns and processes, feedbacks, physical and chemical properties inherent in a fast reactor, its fuel, coolant, and other components. Also important in this respect are the design solutions that allow using to the utmost the natmal safety properties. 

Commercial applications for reinforced PPS compounds generally exploit the plastic material s exceptional combination of resistance to thermal degradation, dimensional integrity at elevated temperatures, resistance to chemical attack, and inherent flame-retardant behavior. It is one of these performance features, or a combination thereof, that leads designers to select PPS. Without the need for such enhanced performance benefits, less expensive engineering plastics will often suffice. 

Heat deflection temperature is defined as the temperature at which a standard test bar deflects by a standard amount under a standard load. Generally loads of 0.45 and 1.80 MPa are used. The values of heat deflection temperature of various plastics are compared at different loads in Table 14. It can be seen Ifom the table that the heat deflection temperature of PP is higher than the PE but, it is outranked by more expensive engineering thermoplastics. 

S. Karlsson and A.-C. Albertsson, Recycling of Cheap Packaging Waste Versus Expensive Engineering Materials, J. Kahovec (ed.), 38th Microsymposium on Recycling of Polymers, Pragne, Czech Republic, WUey, VCH (1997). 

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