Molds plastic

Application Criteria. The desiga and constmction of axial fans is dictated by size and function. Small fans ate usually molded plastic having... 

Cheese products generally must be maintained under refrigeration using closed flexible plastic, or plastic cups or tubs for packaging. Ice cream packaging is generally minimal, ie, lacquered or polyethylene extmsion-coated paper-board cartons, molded plastic tubs, or spinal wound composite paperboard tubs or cartons. 

A basic dmm is often supplemented by blow-molded plastic inserts that fit closely into the interior cavity. These inserts generally are provided with molded fittings for filling and sealing. The combination, which is referred to as a composite dmm, enhances the fiber dmm for additional appHcations,... 

The amide linkage characterizes nylons. In the first commercial nylon, nylon-6,6, R = (CH2 )g and R = (CH2 )4. Nylon-6,6 is familiar as a textile fiber (nylon stockings) and a molded plastic (see Polyamides). 

Some amino resins are used as additives to modify the properties of other materials. For example, a small amount of amino resin added to textile fabric imparts the familiar wash-and-wear quaUties to shirts and dresses. Automobile tires are strengthened by amino resins which improve the adhesion of mbber to tire cord (qv). A racing sailboat may have a better chance to win because the sails of Dacron polyester have been treated with an amino resin (1). Amino resins can improve the strength of paper even when it is wet. Molding compounds based on amino resins are used for parts of electrical devices, botde and jar caps, molded plastic dinnerware, and buttons. 

Both urea— and melamine—formaldehyde resins are of low toxicity. In the uncured state, the amino resin contains some free formaldehyde that could be objectionable. However, uncured resins have a very unpleasant taste that would discourage ingestion of more than trace amounts. The molded plastic, or the cured resin on textiles or paper may be considered nontoxic. Combustion or thermal decomposition of the cured resins can evolve toxic gases, such as formaldehyde, hydrogen cyanide, and oxides of nitrogen. 

Cell Construction. Nickel—2iac batteries are housed ia molded plastic cell jars of styrene, SAN, or ABS material for maximum weight savings. Nickel electrodes can be of the siatered or pocket type, however, these types are not cost effective and several different types of plastic-bonded nickel electrodes (78—80) have been developed. 

Large quantities of secondary cellulose acetate are used worldwide in the manufacture of filter material for cigarettes. Because of its excellent clarity and ease of processing, cellulose acetate film is widely used in display packaging and extmded plastic film for decorative signs (see Packaging materials). Injection-molded plastics of cellulose acetate are used in toothbmsh handles, computer bmshes, and a large variety of other appHcations (7). 

Insulators. Molded plastics serve as insulators for multicontact connectors and glass is used in hermetic connectors intended for bulkhead... 

Most molded plastics have a very smooth, hydrophobic surface that must be modified. Chemical etchants are used to oxidize and roughen the surface. The resultant hydrophilic surface promotes good metal-to-plastic adhesion. The etchant is usually a solution of chromic acid and sulfuric acid pure chromic acid can also be used. 

Fan blades can be made of aluminum, molded plastic, laminated plastic, carbon steel, stainless steel, and Monel. 

As applied to molded plastics, the process of heating material to a specified temperature and slowly cooling it to relieve stresses. 

Molding, transfer Process of molding plastic articles from powdered,... 

Aside from SMC molded plastics, BMC molded natural fiber plastics with good mechanical properties can be produced. Owolabi et al. [59] made such plastics with coir fibers, their basic recipe is shown in Table II. 

Figure 16 Characteristic values of glass fiber and flax fiber SMC molded plastics (absolute values and in reference to density) [58].

Figure 18 Tensile strength of B.M.C. molded plastics as dependent on their fiber content. %fibers = g fibers/100 g UP resin.

Blind holes in molded plastics are created by a core supported by only one side of the mold. The length of the core and depth of the hole are limited by the ability of the core to withstand the bending forces produced by the flowing plastic without excessive deflection. For this reason, the depth of a blind hole should not exceed three times its diameter or minimum cross-sectional dimension. For small blind holes with a minimum dimension below 1/4 in., the L/D ratio should be kept to two. With through holes the cores can be longer, since the opposite side of the mold cavity supports them (3). 

When using molded plastics parts such as the connectors and the circuit supports, it is important to make sure that the moldings, in addition to being made to close tolerances, be made under molding conditions that make for stable products. Electrical products are subjected to strong electrical fields in addition to the usual environmental abuse. Distortion of the product can lead to serious electrical malfunction by changing spacings that will alter electrical characteristics and if... 

Fig. 6-24 Example of effects of number of times in recycled injection molded plastics.

Sound-deadening material is used to make door and drawer operation quieter than formerly. One manufacturer features drawer fronts of molded plastic, which makes it possible to have the handles recessed. 

Blow molding is widely used to make polymeric containers of all sorts. In many markets blow molded plastic products have largely displaced such traditional materials as glass, ceramics, or metal. The inherent advantages of polymeric containers include their light weight, clarity, toughness, and versatility. —... 

Contents Introduction to Materials. Manufacturing Considerations for Injection Molded Parts. The Design Process and Material Selection. Structural Design Considerations. Prototyping and Experimental Stress Analysis. Assembly of Injection Molded Plastic Parts. Conversion Constants. 

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