Polymer processing

In most cases, polymer processing includes converting any form of polymerizable resin (powder, pellets, granules) in solid (or liquid) form into solid plastic products with specific shapes, sizes, properties and attributes. This can be achieved through conversion processes, such as extrusion, injection molding, calendering, coating, hot pressing and other processing. In order to achieve the purpose of the above transformation, this processing generally includes the following operations, such as solid conveying, compression, heating, melting, mixing, molding, cooling, curing and surface treatment. Of course, these operations do not necessarily occur in the above order, and friendly operations can be performed simultaneously.

In order to achieve the required shape and size, materials need to be shaped. This involves a combined operation of viscoelastic deformation and heat transfer, usually by liquid curing of the product.

Molding includes: (1) two-dimensional processing, such as molding, calendering and coating, and (2) three-dimensional molding and modeling processing. Two-dimensional processing includes continuous and stable processing, such as film and sheet extrusion, wire coating, paper and sheet coating, calendering, fiber spinning, tube extrusion and so on. , including batch processing, such as batch blow molding in extrusion. Generally speaking, casting processes are intermittent, so they often involve unstable conditions. Hot pressing, vacuum forming and other similar processes can be regarded as secondary molding processes because they usually involve changing the shape of molded products. In some cases, such as blow molding, the molding process includes primary molding (semi-finished glass, bubble formation) and secondary molding (semi-finished glass, bubble expansion).

Molding involves simultaneous or staggered fluid flow and heat conversion. In two-dimensional machining, curing usually follows molding, while in three-dimensional machining, molding and curing often occur at the same time. The water flow system depends on the properties of materials, equipment used and processing conditions. It usually includes the combination of shear flow, epitaxial flow and compressed flow, as well as closed flow or free surface flow.