Extrusion blow moulding


Extrusion blow moulding of bottles has been successfully accomplished in reeent years by attention to the points mentioned above. It is to be noted here that UP VC has a much lower average specific heat between the proeessing temperature and room temperature than polyethylene and, being essentially amorphous, no latent heat of fusion. This leads to much less heat needing to be removed on cooling of mouldings and very short cycle times are possible.  [c.350]

PFA fluoropolymers may be proeessed by injection moulding, extrusion, extrusion blow moulding and transfer moulding. All machine parts coming into contact with the melt should be made from highly corrosion-resistant high nickel content alloys. Processing melt temperatures can be as high as 420°C and mould temperatures may be in the range 50-250°C.  [c.378]

Extrusion blow moulding  [c.564]

Early interest in the material centred round the ability of the polymer to be thermoformed at draw ratios as high as 4 1 without blushing or embrittlement. Because of its good melt strength the material performs well during extrusion blow-moulding whilst the low moulding shrinkage facilitates injection moulding.  [c.729]

Extrusion Blow Moulding  [c.268]

The convention extrusion blow moulding process may be continuous or intermittent. In the former method the extruder continuously supplies molten polymer through the annular die. In most cases the mould assembly moves relative to the die. When the mould has closed around the parison, a hot knife separates the latter from the extruder and the mould moves away for inflation, cooling and ejection of the moulding. Meanwhile the next parison will have been produced and this mould may move back to collect it or, in multi-mould systems, this would have been picked up by another mould. Alternatively in some machines the mould assembly is fixed and the required length of parison is cut off and transported to the mould by a robot arm.  [c.269]

Extrusion blow moulding is continually developing to be capable of producing even more complex shapes. These include unsymmetrical geometries and double wall mouldings. In recent years there have also been considerable  [c.269]

Since this is less than the melt fracture stress (6 MN/m ) these production conditions would be suitable. These are more worked examples on extrusion blow moulding towards the end of Chapter 5.  [c.272]

In Section 4.2.7 we considered the process of extrusion blow moulding which is used to produce hollow articles such as bottles. At that time it was mentioned that if molecular orientation can be introduced to the moulding then the properties are significantly improved. In recent years the process of injection blow moulding has been developed to achieve this objective. It is now very widely used for the manufacture of bottles for soft drinks.  [c.303]

During extrusion blow moulding of 60 nun diameter bottles the extruder output rate is 46 X 10 m /s. If the die diameter is 30 mm and the die gap is 1.5 mm calculate the wall thickness of the bottles which are produced. The flow curves in Fig. 5.3 should be used.  [c.409]

Figure 8.1. (a) Extrusion—material is pumped, in the above ease with a screw pump, through a die to give a product of constant cross-section, (b) Injection moulding—material is pumped by a screw pump to the front end of the injection cylinder with the screw moving to the rear in order to provide space for the material the screw then moves forward as a ram injecting molten material into a relatively cool mould into which the material sets, (c) Extmsion blow moulding—the extruder tube is inflated in the mould while still above softening point, (d) Calendering—softened material is flattened out into sheet between rolls  [c.160]

Melt elasticity is of considerable importance in understanding much of the behaviour of polyethylene when processing by film extrusion techniques and when blow moulding. The complex relationships observed experimentally here have been summarised by the author elsewhere.  [c.223]

Polystyrene and closely related thermoplasties such as the ABS polymers may be proeessed by sueh techniques as injection moulding, extrusion and blow moulding. Of less importance is the processing in latex and solution form and the  [c.455]

Acetal resins may be processed without difficulty on conventional injection moulding, blow moulding and extrusion equipment. The main points to be considered are  [c.542]

Structurally viscous grades are based on branched polymers (branching being effected by the use of tri- or higher functional phenols). These polymers exhibit a sharp decrease in viscosity with increasing shear rate which makes them particularly suitable for extrusion and blow moulding and also, it is claimed, in reducing drip in case of fire.  [c.564]

For extrusion and blow moulding the polysulphones used are of higher molecular weight. Melt temperatures for blow moulding are of the order of 300-360°C with mould temperatures about 70-95°C.  [c.601]

Example 4.4 A blow moulding die has an outside diameter of 30 mm and an inside diameter of 27 mm. The parison is inflated with a pressure of 0.4 MN/m to produce a plastic bottle of diameter 50 mm. If the extrusion rate used causes a thickness swelling ratio of 2, estimate the wall thickness of the bottle. Comment on the suitability of the production conditions if melt fracture occurs at a stress of 6 MN/m.  [c.271]

Extrusion Stretch Blow Moulding  [c.272]

Fig. 4.25 Extrusion stretch blow moulding Injection Stretch Blow Moulding Fig. 4.25 Extrusion stretch blow moulding Injection Stretch Blow Moulding
Fibre reinforced thermoplastics can be processed using most of the conventional thermoplastic processing methods described earlier. Extrusion, rotational moulding, blow moulding and thermoforming of short fibre reinforced thermoplastics are all possible, but the most important commercial technique is injection moulding. In most respects this process is similar to the moulding of un-reinforced thermoplastics but there are a number of important differences. For example the melt viscosity of a reinforced plastic is generally higher than the unreinforced material. As a result the injection pressures need to be higher, by up to 80% in some cases. In addition the cycle times are generally lower because the greater stiffness of the material allows it to be ejected from the mould at a higher temperature than normal. However, the increased stiffness can also hamper ejection from the mould so it is important to have adequate taper on side walls of the cavity and a sufficient number of strategically placed ejector pins. Where possible a reciprocating screw machine is preferred to a plunger machine because of the better mixing, homogenisation, metering and temperature control of the melt. However, particular attention needs to be paid to such things as screw speed and back pressure because these will tend to break up the fibres and thus affect the mechanical properties of the mouldings.  [c.327]

Cast material is stated to have a number average molecular weight of about 10. Whilst the Tg is about 104°C the molecular entanglements are so extensive that the material is incapable of flow below its decomposition temperature (approx. 170°C). There is thus a reasonably wide rubbery range and it is in this phase that such material is normally shaped. For injection moulding and extrusion much lower molecular weight materials are employed. Such polymers have a reasonable melt viscosity but marginally lower heat distortion temperatures and mechanical properties.  [c.405]

Both homopolymers and copolymers are available in a range of molecular weights (Af 20000-100000). The materials are normally characterised by the melt flow index using basically the same test as employed for polyethylene. For general purpose work polymers with an MFI of about 9 are employed but high-precision work and complex mouldings polymers with MFIs as high as 27 (viz. lower molecular weight polymers) may be used. For extrusion and thick-walled mouldings a polymer with MFI about 2.5 (M, ca 45 000) is often employed although for extrusion blow moulding the special polymers used have MFIs of about 1.0.  [c.543]

This process evolved originally from glass blowing technology. It was developed as a method for producing hollow plastic articles (such as bottles and bairels) and although this is still the largest application area for the process, nowadays a wide range of technical mouldings can also be made by this method e.g. rear spoilers on cars and videotape cassettes. There is also a number of variations on the original process but we will start by considering the conventional extrusion blow moulding process.  [c.268]

The high crystallinity which develops on cooling results in a shrinkage of about 0.020 cm/cm. Because of the low glass transition temperature, crystallisation can take place quite rapidly at room temperatures and aftershrinkage is usually complete within 48 hours of moulding or extrusion. In processing operations injection moulds, blow moulding moulds and sizing dies should be kept at about 80-120°C in order to obtain the best results.  [c.543]

According to the end use application, PEs are processed by various techniques, which include injection moulding, blow moulding, rotomoulding, and film extrusion. However, since the bulk of the processed material is used as film in the area of packaging, the discussion in this chapter focuses mainly on processing behavior and the ultimate properties of tubular blown film.  [c.278]

TPEs are a new class of materials, combining the pro-cessibility ease of thermoplastics and the functional performance of conventional thermoset elastomers. TPEs need no vulcanization and can be processed using conventional techniques, such as injection moulding, blow moulding, extrusion, etc. The morphology of the TPE provides unique properties to it, and it is a phase-separated system. The first phase is hard and solid, while the second one is soft and rubbery at room temperature. The properties depend on the nature and amount of the hard phase present. The temperature range of applications is determined by the combined effect of the glass-transition temperature of the soft phase and the melting point of the hard phase. There are two categories of TPEs (1) Block copolymers of two or more monomers, and (2) Simple blends of thermoplastics and elastomers.  [c.653]

In the usual range of moulding and extrusion materials an increase in molecular weight leads to comparatively small improvements in such properties as tensile strength. It does, however, lead to the usual steep increase in melt viscosity and to an increase in impact strength. This is indicated in Table 20.2, which also indicates the recommended processing method. Polymers with number average molecular weights below 20000 are generally unsuitable as plastics wjulst those with molecular weights above 50 000 (particularly those in range of = ca 70000) are mainly processed into film by solution casting methods.  [c.564]


See pages that mention the term Extrusion blow moulding : [c.304]   
Plastics engineering Изд.3 (2002) -- [ c.268 ]