Plastics joining steps

Polyesters are step-growth polymers in which the monomer units are joined together by ester groups. They have found wide commercial use as fibers, plastics, and coatings. The most common polyester is known by the trade name Dacron and is made by the transesterification (Section 17.10) of dimethyl terephthalate with ethylene glycol. High resilience, durability, and moisture resistance are the properties of this polymer that contribute to its wash-and-wear characteristics. 

A process in which melted plastic is injected into a mold cavity, where it cools and takes the shape of the cavity. Bosses, screw threads, ribs, and other details can be integrated, which allows the molding operation to be accomplished in one step. The finished part usually does not require additional work before assembling. Any IPN in which the individual polymers are thermoplastic. The polymers may contain physical cross-links as in ionomers where ionic clusters join two or more chains together. Nowadays, phase-separated polymeric systems, e.g., block and graft copolymers or thermoplastic polyurethanes, are frequently considered thermoplastic IPNs. 

Figure 8.25 Step fitments (a) external step fitment and (i>) internal step fitment. (Source Jordan I. Rotheiser, Joining of Plastics Handbook for Designers and Engineers, Hanser Publishers, Munich-Hanser Gardner Publications, Inc., Cincinnati, 1999.)...

By definition, a structural bond involves the formation of a load-bearing joint between high-strength materials, typically metal, wood, ceramic, and certain plastics. The first step in the selection of a joining method should be a comparison of the relative merits of the available techniques.In addition to structural adhesives, these include a number of mechanical fastening methods, such as screws, bolts, nails, staples, and rivets, as well as metal fusion processes. Many of these techniques are usually associated with the joining of metal structures. 

Figure 15.3 Basic layout scheme of a biowaste fermentation and composting plant showing alternative routes for compostable plastic bags used for collecting biowaste. Route 1 bioplastics entering the fermentation step. Route 2 bioplastics sorted out and joining the final composting step, and Route 3 bioplastics sorted...

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