Under the hood

Current requirements for vehicles are more pronounced for warm conditions than for cold for many reasons e.g., improved aerodynamics, transversal placement of the motor, generally higher temperatures under the hood, such that the automobile manufacturers prefer a reduction, rather than increase in RVP. 

Cross-linked polyethylene-based compounds that contain dame-retardant components and compounds based on PVC cross-linked by radiation have also received high temperature rating. They find use not only in appHance wires but also in manufacturing under-the-hood automotive wires. 

Phenohc resins are produced by the condensation of phenol or a substituted phenol, such as cresol, with formaldehyde. These low cost resins have been produced commercially for more than 100 years and in the 1990s are produced by more than 40 companies in the United States. They are employed as adhesives in the plywood industry and in numerous under-the-hood appHcations in the automotive industry. Because of the cycHc nature of the automotive and home building industry, the consumption of phenol for the production of phenohc resins is subject to cycHc swings greater than that of the economy as a whole. 

In automotive and aerospace end uses, the apphcations ate also often electrical. Polysulfones do not have as good solvent resistance as poly(phenylene sulfide). They perform well in hydrocarbons like gasoline and oil, or in antifreeze, but ate attacked by the alcohol-blend fuel mixtures. This may limit their under-the-hood apphcations. 

Polyester, thermoplastic TP polyesters have different grades. Polybutylene tereph-thalate (PBT) a crystalline polymer and an excellent engineering material. It has marginal chemical resistance but resists moisture, creep, fire, fats, and oils. Molded items are hard, bright colored, and retain their impact strength at temperatures as low as — 40°F (-40°C). Uses include auto louvers, under-the-hood electricals, and mechanical parts. 

Polyphenylene sulfide PPS is able to resist 450°F (232° C), and has good low temperature strength as well. It has low warpage, good dimensional stability, low mold shrinkage. Use includes hair dryers, cooking appliances, and critical under-the-hood automotive and military parts. 

Phenolic phenol formaldehydes (PFs) are the low-cost workhorse of the electrical industry (particularly in the past) low creep, excellent dimensional stability, good chemical resistance, good weatherability. Molded black or brown opaque handles for cookware are familiar applications. Also used as a caramel colored impregnating plastics for wood or cloth laminates, and (with reinforcement) for brake linings and many under-the-hood automotive electricals. There are different grades of phenolics that range from very low cost (with low performances) to high cost (with superior performances). The first of the thermosets to be injection-molded (1909). 

Polymers that are rigid at high temperatures are known as engineering plastics . This class of polymers includes polyacetal and many nylons. These polymers are used in applications such as small gears in office equipment and under the hood of automobiles. 

We use a variant of flexural testing to measure a sample s heat distortion temperature. In this test, we place the sample in a three point bending fixture, as shown in Fig. 8.6 b), and apply a load sufficient to generate a standard stress within it. We then ramp the temperature of the sample at a fixed rate and note the temperature at which the beam deflects by a specified amount. This test is very useful when selecting polymers for engineering applications that are used under severe conditions, such as under the hoods of automobiles or as gears in many small appliances or inside power tools where heat tends to accumulate. 

Fiber reinforcement of polymers allows us to use them in engineering applications that were previously off limits, We use fiber reinforced injection moldings in many under-the-hood automotive applications, such as rocker box covers and front end modules, which support the radiator, cooling fan, and hood latch, that are subjected to a wide range of temperatures. 

Four hundred and sixty grams (250 ml., 4.7 moles) of concentrated sulfuric acid is added to the filtrate to precipitate mercuric sulfate. The mixture is boiled under the hood for 1 hour, cooled to 10-25°, and filtered with suction through sintered glass. 

Flame-retarded grades are widely used for various computer connectors and circuit board components. Representative applications are edge card connectors, grid arrays and memory modules. Non-flame-retarded grades find use in automotive under-the-hood applications, typically connectors and related parts. As higher temperature soldering techniques become more common in the automotive industry, the use of high-temperature plastics such as PCT is expected to increase. It is also possible to formulate unreinforced PCT with crystallization aids and... 

Poly(butylene terephthalate) (PBT) (1) resins are semicrystalline thermoplastics used in a wide variety of applications, most commonly in durable goods that are formed by injection molding. Applications include electronic and communications equipment, computers, televisions, kitchen and household appliances, industrial equipment, lighting systems, gardening and agricultural equipment, pumps, medical devices, food handling systems, handles, power and hand tools, bobbins and spindles, and automotive parts in both under-the-hood and exterior applications. Additionally, PBT is very widely used to form electrical connectors. PBT, through its many blended products, can be tailored to suit numerous applications. 

PEN is a good candidate for labels where temperature tolerance is required, such as multi-layer labels for automobile bodies when being painted and dried at high temperatures. PEN is ideally suited for bar code labels where dimensional stability and registration are required at elevated temperatures. PEN labels have dimensional-excellence performance on printed circuit boards, in solvent- and aqueous-based painting operations, and in under-the-hood applications. PEN labels also provide substantially improved performance over PET or vinyl labels when the label must survive in harsh chemical environments. PEN performs extremely well in applications where the label must be in contact with organic solvents, such as acetone, ethers, toluene and phenol, as well as strong bases (30 % NaOH) and moderate acids. 

Weathering/Aging - the combined effect of cyclic exposure to varying moisture, temperature and sun exposure, or specific cyclic application conditions such as under the hood grease, oil and temperature variations. 

Transportation Body panels, under the hood components, truck cabs, tractor components, structural elements... 

Sheet molding compounds (SMCs) and bulk molding compounds (BMCs) are the dominant materials used in automotive applications. These composites of unsaturated polyester resin, fillers and fiberglass have advantages of high stiffness, heat resistance and low coefficient of expansion. Coupled with low creep resistance, which is a distinct advantage over thermoplastic competition, and low-profile additives, which can yield Class A surfaces, these materials are well suited for applications from exterior body panels to under the hood components. 

Under-the-hood parts, ventilation and air conditioning units, battery boxes, air ducts, air vents, ventilation nozzles, fan blades, fan bases, fan shrouds, heating device housings, belt covers, corrugated sheaths for wires and cables, windscreen washer parts. .. 

Automotive under-the-hood components, fuel pumps and other fuel system components, ball cocks and caps for gasoline systems, gears, cams, bushings, clips, lugs. .. 

Under-the-hood components, impellers for water pumps in engine cooling. .. 

Under the hood tubes and connectors, plugs, bumpers, grommets for steering, air induction systems, fuel line systems. .. 

Under-the-hood and other mechanical parts subjected to a harsh environment characterized by high temperatures, aggressive fluids (fuel, oils, coolant fluids, brake fluids, ozone. ..). On the other hand, there is no exposure to UV or light. 

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