Plastics process molten

The welded joint differs from all others in that an attempt is made to produce a continuity of homogeneous material which may or may not involve the incorporation of a filler material. There are a large variety of processes by which this may be achieved, most of which depend upon the application of thermal energy to bring about a plastic or molten state of the metal surfaces to be joined. The more common processes used are classified in Table 9.6. 

Sevruk VD, Prokunin AN, Fridman ML (1984) Regularities of molten polymer extension and their manifestation in plastic processing. NIITEHIM, Moscow... 

Esters of saturated, long-chain fatty acids with long-chain fatty alcohols, such as stearyl stearate, have a waxy characteristic. These waxes develop lubricating effects in plastics processing which means they prevent friction between plastic molecules and thus permit faster transport of the molten plastic mass through the processing machines (internal lubrication). At the same time they reduce the friction of the molten plastic with the surrounding machine parts (external lubrication). 

Reducing moisture content below 0.02 to 0.07% can result in stiffer flow. The residual moisture present in dried pellets will plasticize the molten polyamide during melt processing. Tbo low a moisture content can also lead to further polyamide polymerization during processing, and higher polyamide molecular weight could contribute to stiffer flow. 

An open mill is also used in plastic processing departments and is short for an open plastic mixing mill. In a plastic factory, people generally call it a two-roller machine. An open mill is a kind of mixing plastic equipment applied earlier in a plastic products factory. Its role is to blend and plasticize evenly mixed raw materials and form uniformly mixed and plasticated molten material. When cable materials are produced, an open mill could directly plasticize mixed powder into molten material. 

Temperature and pressure are known to be two of the most influential variables in the rheological characteristics of polymer melt in plastics processing. It has long been realized by those in practice that the flow behavior of molten polymer is highly dependent upon these two variables. 

In plastics processing temperature is a decisive process control parameter. Time dependent temperatures can be measured with high accuracy and short response time (msec) using IR sensors that detect the heat radiation from molten plastic [34]. 

If the volatile products which occur during plastics processing do not contain water or other dissociative substances, any wear in the melt region cannot be traced back to electro-chemical corrosion. Electro-chemical corrosion can only be caused by ions. It must then be a purely chemical corrosion caused by degradation products of the polymers or by the functional groups, even in the molten state, as well as optionally by pigments and other additives. 

A mechanical recycling process suitable for mixed plastics, where molten materials are fed into simple moulds. 

The most common tools in plastics processing are molds. A mold is a premade object, which is used to guide the final form or shape of another object. Molds can be open, like a baking pan, allowing for soft or molten material to be poured or draped over the mold surface. After the material cools or solidifies into its final shape, it is then removed from the mold, and the mold is used again. Molds can also be closed, with internal hollow spaces, allowing soft or molten material to fill these spaces. Closed molds are usually made of several parts, and fabricated in such a way that the mold can be opened, allowing for part removal after the plastic material has solidified. 

The most common use of additives are to aid in specific areas of processing. Many of these additives are hidden from sight, as it were, as they are designed to affect the viscous properties of the molten resin, to help it flow better, or to be more homogeneous, or to cool and solidify (and shrink) in a more consistent manner. Some additives are intended to preserve the equipment used in plastic processing, to prevent corrosion of the metals, or enhance the release of the solidified plastic from the mold... 

During the filling stage in a injection molding process, molten plastic forces the gas out of the mold cavity from the vent. If the gas can not vent out before the molted plastic fronts meet, then there will be a v-notch formed between the plastic and the mold wall. The locations of the weld lines are usually decided by the part shapes and the gate locations. Weld lines can be eliminated by the following methods, namely. 

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