Melt temperature blow moulding

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. 

Dried granules may be injection moulded, blow moulded and extruded without undue difficulty with melt temperatures of 220-260°C. The moulding shrinkage (0.003-0.004 cm/cm) is very low and a somewhat greater than normal draft may be required in deep draw moulds. 

Processing temperatures should not exceed 180°C, and the duration of time that the material is in the melt state should be kept to a minimum. At the end of a run the processing equipment should be purged with polyethylene. When blow moulding, the blow pin and mould should be at about 60°C to optimise crystallisation rates. Similarly, injection moulds are recommended to be held at 60 5 C. 

PET is a material that finds widespread use for soft drink and beverage bottle applications. For injection or blow moulding applications, high-molecular-weight PET Mn > 30000 is required. While PET with of 15 000 — 25 000 can be achieved by a standard melt-polymerization process, the high-molecular-weight PET grades require a solid-state polymerization process. Commercial solid-state polymerization process systems are usually composed of a crystallizer and a polymerization reactor. First, melt-polymerized chips are fed into the crystallizer unit and crystallized to the extent of about 40 %. In a second step, tlie crystallized chips are fed into a polymerization reactor vessel and then polymerized in the solid state at a temperature of around 220 °C. 

Only a very small amount of PP is processed by the blow moulding technique. As a blow moulding material, PP has never enjoyed the success of HOPE. This is in large measure because mouldings of PP require more attention to equipment design and operating conditions. The initial development of the machinery for blow moulding was optimised for HOPE due to its earlier invention. The difficulty with PP is that its melt viscosity is far more sensitive to temperature and shear rate than is the case for PE. 

This technology accoxmts for an annual production of 4-5 million tons of HDPE. The process involves polymerization of ethylene at temperatures below the melting point of the polymer using a solid catalyst to form solid polymer particles suspended in an inert hydrocarbon diluent. Recovery of polymer (by filtration, centrifugation, or flashing) is economic. The chromium oxide-on-silica catalyst developed by Phillips yields polymers which can be easily extruded and blow-moulded. The process is unable to produce copolymers of density below 0.937 g/cm. For a density of 0.92 g/ cm or below, the polymer swells, becomes sticky, and starts to dissolve in the reaction diluent. 

The material most generally used is HDPE, and grades with MFR values as low as 0.1 or even 0.01 can be blow moulded quite readily. For LDPE a MFR range from 0.5 to 0.8 is suitable. A typical melt temperature is 191 °C. 

Biaxially oriented products have been made by extrusion blow moulding using a die temperature below the melting temperature. However, the biaxial orientation as well as the properties vary through the thickness of the product and depend strongly on the thermomechanical conditions of the process. For LCP materials with slow crystallization rates, blow moulding in the supercooled state represents a possible method of obtaining multidimensional properties. ... 

Copolymers more prevalent than homopolymers as easier to process. Melting Point 160 to 180°C. Processible by injection moulding, extrusion and blow moulding with melt temperatures of 180 to 220°C. 

The first step in the Pro/Mechanica steady state thermal analysis is to supply the boundary conditions i.e. the temperature values in the mould. The die cavity resembles the shape of the bottle. The parison is formed by extrading the melted plastic through a die. Since the parison is inflated to form the shape of the bottle, the plastic will be in direct contact with the mould. So the temperature of the mould surface will be eqital to the temperature at which the plastic melts. Data from the blow moulding machine show that the plastic melts at a temperatirre of 190°C. So this temperatme of 190°C is... 

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