Integral hinge

Viseoelastie behaviour must be taken into account in the design of mouldings. In preeision engineering, it is accepted that the deformation of the component over a given period of time should not exceed 0.25%. This condition is related to a given stress. If greater deformation is permissible within the same period of time, the stress may also be higher. It should be remembered that the mechanical properties of a plastic are dependent on time, temperature and stress. 

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Clear or drop impact resistant containers, boxes, hot filled bottles, dessert pots, horticultural pots, integrated hinge boxes, bottles and other cans up to several litres, caps and closures for beverage and cosmetic applications, medical disposable trays, containers for irrigation, parenteral, haemodialysis solutions. .. 

Polypropylene (PP) resembles PE, but is somewhat harder and stiffer than HDPE. It is crystalline as well, and melts at 165 °C. Its impact strength at lower temperatures is quite poor therefore PP is often modified with a certain amount of rubber (mostly built-in as a copolymer). Main applications are film for packaging, fibres, crates, pipes, automotive parts (often with reinforcing fillers). A special feature of PP is its ability to form integral hinges with a practically unlimited resistance against repeated bending. 

Lo r density. stifFer. and higher temperature resistance than PE used for water pipes, integral hinges, sterilizable hospital equipment. e.g. Propathenet Novoien, Moplen, Hostalen, Mariex. 

Narrow, thin sections, that run straight across injection mouldings, can act as integral hinges (Fig. 1.15). These replace the metal pins, pressings and... 

Coining n. A term borrowed from the metalstamping industry for a process of forming integral hinges from plastics. In the case of a polypropylene article, the hinge is... 

Plastics made a brief but successful entry into the area of control pedals in the early 1960s, when several General Motors models were equipped with floor-mounted accelerator pedals in polypropylene mouldings incorporating an integral hinge. These represented a two-thirds cost reduction compared with the steel and rubber equivalent. 

Although integral hinges are feasible with a number of thermoplastics (e.g., the polyolefins, acetal, nylon, styrene-butadiene, etc.), the concept is generally associated with polypropylene. This section discusses the integral hinge as it is generally applicable to polypropylene. 

There are three techniques used to fabricate integral hinges molded-in (by injection or blow molding), cold worked, extruded, and coining. 

An integral hinge can be injected molded by conventional techniques, provided certain factors are kept in mind. 

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