compression ratio changes in the three sections are often not the same, the extrusion process Mainly in the feed is completed, so the feed section of the compression ratio and slice the apparent density (or 100 grain weight). When the true density of the polyester resin chips / apparent density (or 100-seed weight) = the compression ratio of the feed section, the air between the slices is exactly passed into the molten plasticizing section, usually to ensure sufficient exhaust The true density / apparent density is smaller than the compression ratio of the feed section. The true density is essentially constant, and the variable density is related to the shape and size of the slice. Small particles of the apparent density of large, is conducive to extrusion exhaust, so the particle size of the bottle is much smaller than the fiber slices.
The compression ratio of the molten plasticized section is determined by the change in density before and after the slice is melted. Polyester crystal melting when the density becomes smaller, the volume increases, so this section of the compression ratio is generally not designed to be large, because the melting process takes some time, this time there may be with the extrusion exhaust, so although It is difficult to clearly delineate the boundaries between the feed and the melt-plasticized sections, but it is certain that the principle of complete exclusion of air into the melt. The small pieces of chips help to shorten the time required for the melt-plasticizing process, thereby increasing the melt plasticizing efficiency and effectiveness of the extruder. Ash ash indicates the content of inorganic components in the polyester resin chips. The source of dust, mainly from the polyester production process to add a variety of additives, such as catalysts, heat stabilizers, toner and sliced ??inorganic impurities. Inorganic components caused by the ash will make the thermal stability of the slice and thermal oxygen stability decreased, easy to lead to the product when the viscosity increase, product quality decline. Ash is also a degree of crystallization of the nucleus, so the ash content of high prone to preform fog. Ash will also affect the color of the preform to a certain extent. ● Surface oxidation or variegated particles due to solid phase polymerization is carried out at a higher temperature for a long time, so the slice hue has a great impact, the general viscosity of 0.85dl / g of the bottle grade polyester chips solid phase viscosity b value Increase by about 3 units. Normal slices of the hue through the color value of the project control, and may produce different color particles in addition to the manufacturer of the process of visual monitoring, the injection molding manufacturers also need to strengthen the visual.

? The crystallization temperature (Tc) temperature continues to rise, and multiple molecular chains with intermolecular interactions are locally rearranged to produce spherical crystals. As the PET ring benzene ring rearrangement is very slow, PET maximum crystallization of about 55%, can produce an orderly crystallization zone. ● Melting temperature (Tm) At this temperature all the crystals have been melted. This temperature corresponds to the minimum ordered state of the substance. 1) Application Because PET has excellent physical properties, easy to process, so widely used.