Molding applications

There are far too many applications for injection molded products to thoroughly cover here. However, a few examples will help provide an idea of some of the important mold design and machining considerations. 

Let s consider the humble bottle cap just a little further. It has threads on the inside to attach it to the bottle. Recall that when this part is molded, a core forms the inside of the prodnct After cooling, ejection is actu- 

---

Molding Applications. Mol ding is accompHshed by three different methods blow mol ding, injection mol ding, and rotational mol ding, although the use of LDPE in these appHcations has been declining since the introduction of LLDPE on the market. 

Table 16. Properties of Resin for Injection-Molding Applications ...

Isophthalic acid s main use is for producing polyesters that are characterized hy a higher abrasion resistance than those using other phthalic acids. Polyesters from isophthalic acid are used for pressure molding applications. 

Molding applications dominate the market of phenolic resins. Articles produced by injection molding have outstanding heat resistance and dimensional stability. Compression-molded glass-filled phenolic disk brake pistons are replacing the steel ones in many automobiles because of their light weight and corrosion resistance. 

Cellulosic They are tough, transparent, hard or flexible natural polymers made from plant cellulose feedstock. With exposure to light, heat, weather and aging, they tend to dry out, deform, embrittle and lose gloss. Molding applications include tool handles, control knobs, eyeglass frames. Extrusion uses include blister packaging, toys, holiday decorations, etc. Cellulosic types, each with their specialty properties, include cellulose acetates (CAs), cellulose acetate butyrates (CABs), cellulose nitrates (CNs), cellulose propionate (CAPs), and ethyl celluloses (EC). 

Thermoplastic molding applications for VDC copolymers, 25 726-727 Thermoplastic olefin polymer of amorphous structure (TOPAS), 16 113 Thermoplastic polyester bottles, recycling, 20 54-56... 

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. 

Foam accounts for less than half of the polystyrene output. The remaining products have properties very different from foam. PS is an excellent plastic for molded automobile and refrigerator parts. It accepts color so well that it is widely used in molding applications to simulate wood. Probably the wood on your BMW dash is PS. 

Figure 11.24 Simulated axial pressure profile for the 152.4 mm diameter screw running HOPE resin in a high-speed blow-molding application...

Used in molding applications, appliances, TVs, automotive parts, filler, impregnating paper, varnishes, decorative laminates, electrical parts, countertops, toilet seats, adhesive for plywood, sandpaper, brake linings, abrasive wheels No large industrial applications... 

Depending on the application, different demands are placed on the melt viscosity of the polymer. For injection molding applications, lower melt viscosities are required than for extrusion applications. For a given comonomer composition and processing temperature, the melt viscosity of the cycloolefin copolymers increases with the mean molecular weight. 

Copolymers of acrylonitrile are used in extmsion and molding applications. Commercially unportant comonomers for barrier applications include styrene and methyl acrylate. 

Injection molding is the second largest market for LLDPE, accounting for over 10% of its total consumption. Over half of the LLDPE consumed in injection-molding applications is used for housewares. 

LLDPE resins formulated for the blow molding applications have superior environmental stress-cracking resistance and low gas permeability. These features opened new bottle markets where such properties are important. A large variety of molded articles with a complex configuration... 

Because of the low level of emulsifiers and protective colloids, the suspension polymer types are most suitable for electrical applications and end uses requiring clarity, This form is also employed in the bulk of extrusion and molding applications. Cost is lower than for emulsion and solution forms. The emulsion or dispersion resins are employed mainly for organosol and plastisol applications where fast fusion with plasticizer at elevated temperature will occur as a result of the fine particle size of the resin. 

Recycling. The methods proposed for the recycling of polyurethanes include pyrolysis, hydrolysis, and glycolysis. Regrind from polyurethane RIM elastomers is used as filler in some RIM as well as compression molding applications. The RIM chips are also used in combination with rubber chips in the construction of athletic fields, tennis courts, and pavement of working roads of golf courses. 

Vinylidene chloride-vinyl chloride copolymers were originally developed for thermoplastic molding applications, and small amounts are still used for this purpose. Extrusion of VDC-VC copolymers is the main fabrication technique for filaments, films, rods, and tubing or pipe, and involves the same concerns for thermal degradation, streamlined flow, and noncatalytic materials of construction as described for injection-molding resins. A significant application for vinylidene chloride copolymer resins is in the... 

Pellets for injection-molding, extmsion, and blow-molding applications include mineral-filled, glass-filled, pigmented, and dame-retarded grades. 

To illustrate the effect of fiber orientation on material properties of the final part, Fig. 8.60 [5] shows how the fiber orientation distributions that correspond to 67 50 and 33% initial mold coverage affect the stiffness of the finished plates. The Folgar-Tucker model has been implemented into various, commercially available compression mold filling simulation programs and successfully tested with several realistic compression molding applications. 

---