Injection moulding polypropylene

Characterising glass fibres in an injected moulded polypropylene plate (a) Fibre length distribution (Mine, R J. et aL, Compos. Sci. Tech., 62, 1445, 2002) (b) theoretical angular distribution (Mine, R J. et al., Compos. Sci. Tech., 64, 1081, 2004) Elsevier. 

Is the mean length of the glass fibre reinforcement in injection-moulded polypropylene (fig. 4.28a) sufficient enough to give optimal stress transfer to the fibres Explain how the stiffness anisotropy in such a moulding arises. What new mechanisms of energy absorption arise when polystyrene is converted into a low density closed cell foam, and how can the compressive yield stress be controlled over a range of values ... 

Fujiyama, M., Wakino, T. and Kawasaki, Y. (1988) Structure of skin layer in injection moulded polypropylene. /. Polymer Sd., Part B, Polymer Phys., 35, 29-49. 

Kalay, G., Zhong, Z, Allan, P and Bevis, M.J. (1996) The occurrence of the y-phase in injection-moulded polypropylene in relation to the processing conditions. Polymer, 37, 2077-2085. 

Karger-Kocsis, J. and Friedrich, K. (1989) Effect of skin-core morphology on fatigue crack propagation in injection moulded polypropylene homopolymer, Int. J. Fatigue, 11, 161-168. 

Trotignon, J.P., Lebrun, J.L. and Verdu, J. (1982) Crystalline polymorphism and orientation in injection moulded polypropylene. Plastics Rubber Processing Applic. 2, 247-251. 

The subject of crystallization from stressed melts has been reviewed (Kumaraswamy 2005) and one frequent occurrence in the time sequence of this crystallization is the formation of row nuclei which give rise to structures known as shish-kebabs . Polypropylene is the polymer best known for its remarkable propensity for forming row structures, which often contain considerable amounts of P-phase material (Olley et al. 2014), and are a major feature of the skin-core stmcture of injection-moulded polypropylene (Shinohara et al. 2012), but they are also found in polyethylene (An et al. 2006), isotactic polystyrene (Azzurri and Alfonso 2008), poly(phenylene sulfide) (Zhang et al. 2008) and polylactide (Xu et al. 2013). 

In injection-moulded polypropylene products, densely packed row stmctures are typically found near the surface of the object. At least one process has been developed which is able to deliver this morphology throughout the moulded object, namely shear-controlled orientation injection moulding (SCORIM) (Kalay and Bevis 1997). 

Injection moulded polypropylene-PIB-silica samples were studied using TA Instruments DSC 2920. The samples were heated and cooled twice from 0°C to +210°C with scan rate 10°C/min. 

D. E. Mouzakis, T. Harmia, J. Karger-Kocsis (2000) Fracture behaviour of discontinuous long glass fibre reinforced injection moulded polypropylene, Polym. Polym. Compos. 8, 167. 

Injection moulded polypropylene is used extensively in the manufacture of food storage containers either thick walled or thin walled. Polypropylene, due to its higher softening point when compared to polyethylene, is useful in food packaging applications where... 

One unfortunate characteristic property of polypropylene is the dominating transition point which occurs at about 0°C with the result that the polymer becomes brittle as this temperature is approached. Even at room temperature the impact strength of some grades leaves something to be desired. Products of improved strength and lower brittle points may be obtained by block copolymerisation of propylene with small amounts (4-15%) of ethylene. Such materials are widely used (known variously as polyallomers or just as propylene copolymers) and are often preferred to the homopolymer in injection moulding and bottle blowing applications. 

Whilst it is inevitable that polypropylene will be compared more frequently with polyethylene than with any other polymer its use as an injection moulding material also necessitates comparison with polystyrene and related products, cellulose acetate and cellulose acetate-butyrate, each of which has a similar rigidity. When comparisons are made it is also necessary to distinguish between conventional homopolymers and the block copolymers. A somewhat crude comparison between these different polymers is attempted in Table 11.7 but further details should be sought out from the appropriate chapters dealing with the other materials. 

In broad tonnage terms the injection moulding markets for high-density polyethylene and polypropylene are very similar. The main reasons for selecting polypropylene have been given above. In favour of HDPE is the inherently better oxidation and ultraviolet resistance. Whilst these properties may be greatly improved in polypropylene by the use of additives these may increase the cost of polypropylene compounds to beyond that which is considered economically attractive. It is for this reason that HDPE has retained a substantial part of the crate market. 

In recent years general purpose polystyrene and high-impact polystyrenes have had to face intensive competition from other materials, particularly polypropylene, which has been available in recent years at what may best be described as an abnormally low price. Whilst polystyrene has lost some of it markets it has generally enjoyed increasing consumption and the more pessimistic predictions of a decline have as yet failed to materialise. Today about 75% of these materials are injection moulded whilst the rest is extruded and/or thermoformed. 

The RIM process was originally developed for the car industry for the production of bumpers, front ends, rear ends, fascia panels and instrument housings. At least one mass-produced American car has RIM body panels. For many of these products, however, a number of injection moulding products are competitive, including such diverse materials as polycarbonate/PBT blends and polypropylene/EPDM blends. In the shoe industry the RIM process has been used to make soling materials from semi-flexible polyurethane foams. 

Polypropylene is also used in the manufacture of filament, injection moulding and film. Polypropylene is widely used for manufacturing ropes and seat covers. Due to its low cost and low density, polypropylene could ultimately compete heavily with cotton and rayon fibres. 

Plastic sealed door module is injection moulded from long-glass fibre polypropylene pellets by Faurecia for the Ford Fiesta. 

Ford Focus is injection moulded from HPP30GR20BK, a glass fibre reinforced polypropylene allowing a zero-maintenance engine air filter. 

Journal of Vinyl and Additive Technology 2, No.2, June 1996, p.167-9 MICROCELLULAR FOAMING OF POLYPROPYLENE CONTAINING LOW GLASS TRANSITION RUBBER PARTICLES IN AN INJECTION MOULDING PROCESS Chicheng Wang Cox K Campbell G A Clarkson University... 

INJECTION MOULDED STRUCTURAL FOAM MADE FROM POLYPROPYLENE... 

In addition to the nature of particulate platelet orientation induced during injection moulding, the associated consequences on molecular orientation and crystalline order of the host thermoplastic matrix have also been reported with particular regard to various flake-filled polypropylenes [174], together with an attempt to interrelate these higher order structural parameters with physical properties of the composites [175]. 

Medina, E.M.G. (1996) Alignment and management of talc platelets in polypropylene matrix by the application of shear controlled orientation injection moulding (SCORIM) technology. PhD thesis, Brunei University, UK... 

Cases are now almost exclusively fabricated by injection moulding using synthetic polymers which have replaced the bitumen and hard rubber widely used in the past. Polypropylene has excellent mechanical and... 

Hunt et al. [ 17] have investigated the role of various coupling agents, such as zirconates, titanates, and zircoaluminates, in zirconia-polypropylene suspensions for use in the production of ceramics by injection moulding. All the coupling agents were observed to reduce the melt viscosity. 

The dithiocarbamates have the pentacoordinate binuclear structure (44). The diamyl- and diethyl-dithiocarbamate complexes have been found to inhibit the hardening of asphalt, but the effect appears too weak to be useful.127 The latter complex is an effective antioxidant for polyethylene,128 polypropylene,129 polystyrene,130 poly(methyl methacrylate)130 and an isoprene-styrene copolymer.131 The di-n-butyldithiocarbamate complex is important in the vulcanization and injection moulding of rubber,132 as a stabilizer against photolytic and thermal degradation. 

Even yet experts say that the best combs are saw-cut from flat uniform pieces of bone (and such combs remain on sale in more-expensive shops). Combs can be cut in the same way from plastic sheet, achieving comparable quality, but the stock must be prepared suitably and the work as a whole is more costly than the commercial method of making plastic combs in large numbers—injection moulding using materials such as nylon or polypropylene from the moulding process, after removal of the sprues, fully finished, saleable products (teeth included) can be obtained in a few seconds. 

During gas injection moulding a gas such as nitrogen is injected into the melt in such a way that it stays in discrete pockets in the thicker sections and as the material cools these pockets of gas help to keep it in contact with the walls of the mould. Moulding of polypropylene in thick section may be done by this... 

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