Injection-moulded articles

In 1930 BASF, then part of IG Farhen, installed a plant for producing 100 tonnes of polystyrene per annum and in 1933 the first injection moulded articles were produced. In the US semi-plant-scale work at the Dow Chemical Company showed promise of commercial success in 1934. As a consequence there became available shortly before World War II a material of particular interest because of its good electrical insulation characteristics hut otherwise considerably inferior to the polystyrene available today. Because of these excellent electrical characteristics prices were paid of the order of several dollars per pound for these polymers. 

The iQ automotive battery incorporates a micro-chip which monitors and controls the electrochemical process of the lead-acid battery, as well as its physical environmental and operating conditions. The thermal insulation of the battery also plays an important role. Neopolen P, a thermoplastic particle foam from BASF which can be processed completely without blowing agents, was chosen for this application. The foamed battery container calls for a solid frame that can be mounted onto the car body, and this frame is configured as a solid PP injection-moulded article, and fused to the container. 

Polybutylene terephtalate (PBTP) differs in its chemical structure only slightly from PETP its melting point is somewhat lower and its processability is better. The applications in injection moulded articles are similar to those for PETP. 

The surface structure of a plastic may exert a considerable influence on the friction an example is given by injection moulded articles of PP, which show, in touch with each other, a coefficient of 0.7, while for sand-blasted surfaces a value of only 0.3 is found. For injection-moulded nylon // = 0.65, for machined surfaces 0.47. As a matter of fact, lubrication has a strong influence the value of 0.47 for nylon is reduced to 0.19 with water lubrication and to 0.08 with oil. 

Most biodegradable polymers can be used for making injection moulded articles. Starch-based polymers are used to manufacture a wide range of items such as pencil sharpeners, rulers, cartridges, combs and toys, plant pots and bones. 

A variety of injection moulded articles can be produced using Mater-Bi. These include pencil sharpeners, rulers, cartridges, toys, plant pots, and bones. As an antistatic material, combs made of Mater-Bi do not produce the electrical charge given by conventional combs. 

There are situations where this ease of orientation in polymers is undesirable. For example, orientation occurs readily in injection moulding, and if an injection-moulded article is highly anisotropic, it is likely to... 

Fig. 1. Inspection of injection moulded article between crossed pokiroids. (Photo-graph kindly supplied by M. G. Griffin Brunei University.)...

In order to minimise as far as possible the influence of processing variables, studies have been carried out using tensile creep tests on carefully prepared compression moulded specimens. It must be realised that, vv ith injection moulded articles, the creep properties will also be subject to variation with the amount and direction of residual flow orientation, while, with crystalline polymers such as the polyolefins, the creep effects will also be influenced by variations in density caused by a combination of flow orientation, compressive packing, and cooling effects. Stresses will generally be complex and will often involve compressive and flexural components. However, articles should normally be designed to limit the strains occurring to quite low levels, where a reasonable correlation can be expected between tensile, compressive, and flexural creep data. 

Injection moulded articles represent only a small proportion (5%) of the consumption of LDPE and LLDPE. This proportion is not insignificant, however, considering the total volume of 300,000 tonnes per year. LDPE and LLDPE parts produced by injection moulding are used in a wide range of applications, for example, for domestic storage containers and closures in cosmetic, food, and pharmaceutical applications. High environmental stress crack resistance and low warpage are required for LLDPE applications. 

Table 34 Pilot recipes for injection moulded article ...

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