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Factors which affect the basic process of plastics

Jul. 01, 2019

Factors affect the basic process of plastics shared by Custom PE Plastic Extrusion Profile supplier.

The heating elements

We know that extruded plastic is hot plastic, which melts when heated and solidifies again when cooled. Melt plastic heat, mainly feed preheating and cylinder/mold heater from the role. But the motor can also input energy -- the motor can overcome the resistance of the viscous melt, and the friction heat generated in the cylinder when rotating the screw is the most important heat source for all plastics. For all other operations, it should be known that the cylinder heater is insufficient. The main heat source in operation, the temperature of the rear cylinder, is probably still the most important because it affects the speed at which solid material is transported in the gear or feed, and the die head and die temperature should normally be melt temperature or close to it. Therefore, we should keep in mind that the thermal degradation of thermoplastics is proportional to the heating time when extruding plastics. In general, in order to improve the internal quality of extrusion products, the thermal degradation of the melt should be prevented as far as possible, that is, the melt should not stay in the die head for too long.

Feed area elements

Is known to all, each input feed extruder than feeding area of the cylinder and the screw surface temperature is low, feeding area of the cylinder surface, however, are almost always on plastic melting range, it is through contact with the feed grain cooling, heat from hot front-end backward heat transfer and controlled heating and maintain, or even the end by the viscous friction heat, keep and do not need cylinder heat input, the need to open the heater. In particular, the general groove type feeding barrel, specially for low pressure polyethylene, in order to make a single screw extruder smooth barrel feeding area solid grain conveying volume to reach the maximum, plastic particles should be on the barrel and slide to the screw. If this material sticks to the root of the screw, and nothing pulls it down, the volume of the channel and the amount of solid inlet decreases. Most plastics slide naturally through the roots, so they are cold when they enter, and friction forces do not heat the roots to the same heat as the walls of the cylinder, for example, highly plasticized PVC and some of the adhesive polyolefin copolymers desired for eventual use.

PVC Plastic Extrusion Profile

For the barrel, the plastic is adhered to the barrel so that it is removed and pushed forward by the thread of the screw. There should be a high friction coefficient between the grain and the wall, and the friction coefficient is strongly affected by the temperature of the back cylinder. If the grain does not adhere, just turn on the spot and do not push forward, this is the smooth feed is not good reason.

Surface friction is not the only factor affecting feed. Many particles do not contact the barrel or the root of the screw, so there must be friction and mechanical and viscosity linkage in the barrel. Some machines with slots in the barrel of course is another case. The tank is thermally insulated from the rest of the cylinder in the feed area and is also deeply water-cooled. The thread pushes the particles into the groove and forms a high pressure over a considerable distance, which increases the bite tolerance of the same output lower screw speed, resulting in less friction heat at the front end and lower melt temperature. This may mean that cooling limits the flow of water out of the membrane production line faster. Therefore, canister grooving is particularly suitable for polyethylene.

That's all for the sharing, thanks for your reading, and we also supply PVC Plastic Extrusion Profile for sale, if you have any demand for our products, just feel free to contact us.

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