Metals with plastics

In the automobile industry, technical developments to reduce fuel consumption have been promoted to reduce carbon dioxide emissions. In automotive lightweighting, the substitution of metal with plastic components from plant origin is desirable. Durability of these bioplastic components for at least 10 years is required along with demanding physical properties to meet various automotive end-use requirements. PP has mainly been used as the automotive plastic material. As PLA may be inferior in thermal resistance, impact resistance, and durability in comparison to PP, a variety of technologies have been developed so that these issues can be resolved. Figure 28.19 shows examples of the improvement... 

The process of electrodeposition has been developed to provide uniform, highly adhesive, corrosion-resistant primer coats, particularly for the automotive industry. (The ultimate solution to the corrosion problem is simply to replace metal with plastic, as is done for many applications.) In the most common form of the process, polymers that contain carboxylic acid functionalities are produced. These polymers are then solubilized in an aqueous medium by partial neutralization with a base to give macroanions (P represents a polymer backbone) the macroanions are beheved to exist as micelles. 

Rusting can be prevented by painting or coating with a continuous layer of another metal which does not itself corrode rapidly, for example zinc or tin. More recently, steel has been coated with plastics by electrophonetic decomposition from an emulsion of the plastic. 

Polymer-based rocket propellants are generally referred to as composite propellants, and often identified by the elastomer used, eg, urethane propellants or carboxy- (CTPB) or hydroxy- (HTPB) terrninated polybutadiene propellants. The cross-linked polymers act as a viscoelastic matrix to provide mechanical strength, and as a fuel to react with the oxidizers present. Ammonium perchlorate and ammonium nitrate are the most common oxidizers used nitramines such as HMX or RDX may be added to react with the fuels and increase the impulse produced. Many other substances may be added including metallic fuels, plasticizers, stabilizers, catalysts, ballistic modifiers, and bonding agents. Typical components are Hsted in Table 1. 

With metal and plastic parts and other components... 

FWWMR Finish. The abbreviation for fire, water, weather, and mildew resistance, FWWMR, has been used to describe treatment with a chlorinated organic metal oxide. Plasticizers, coloring pigments, fiUers, stabilizers, or fungicides usuaUy are added. However, hand, drape, flexibUity, and color of the fabric are more affected by this type of finish than by other flame retardants. Add-ons of up to 60% are required in many cases to obtain... 

Many cellular plastic products are available with different types of protective faces, including composite metal and plastic foils, fiber-reinforced plastic skins, and other coatings. These reduce but do not eliminate the rate of aging. For optimum performance, such membranes must be totally adhered to the foam, and other imperfections such as wrinkles, cuts, holes, and unprotected edges should be avoided because they all contribute to accelerated aging. 

NonmetalHc centrifugal pumps utilize polymers for all components coming into contact with the pumping media. Even the steel (qv) shaft is sleeved with plastic to isolate the shaft from the fluid. Mechanical seals are reversed so that the metal face does not come into contact with the corrosive... 

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