System control is the key to ensure the long-term stability of PVC profile quality. It includes four items: “formulation quality, process quality, appearance quality, physical and chemical indicators”. The first two items are the premise and basis of the latter two, and also the quality control and technical management. The top priority.

1. The uniformity of the mixing of the resin and the additive and the apparent density of the mixture will have a greater impact on the impact strength of the PVC.

2. PVC processing temperature has a certain range. If the temperature is too high, PVC is easy to decompose; if the temperature is too low, PVC plasticization is not sufficient, and uneven dispersion of various components will lead to increased brittleness.

3. The main engine speed reflects the shearing action of the extruder on PVC. If the rotation speed is too large and the shearing force is increased, the low temperature performance and the welding angle strength of the product will be lowered.

4. The high molding pressure is beneficial to improve the mechanical properties of the profile, especially the low temperature impact strength.

5. The profile forming cooling function is to cool and stretch the stretched macromolecular chain in time to meet the requirements of the product. The slow cooling allows the macromolecular chain to stretch for a sufficient time, so that the internal stress is small, which can reduce the warpage, bending and shrinkage of the product, thereby improving the impact strength and the welding angle destructive force of the product.

formula

Discuss that the formula cannot be separated from the raw materials. The quality of the formulation does not depend entirely on the proportion of the components and depends to a large extent on the intrinsic properties and quality of the raw materials.

Composite stabilizers are the most important type of additives in PVC processing and have an impact on all indicators of PVC profiles. The composite stabilizer acts both as a stabilizer and as a lubricant. Stabilization is to prevent the degradation of PVC molecules during processing and use, so as to ensure that PVC profiles can have the mechanical properties required for doors and windows; the combination of internal and external lubricants affects fluidity and viscosity, which in turn affects the cold impact and weld angle of PVC profiles. , dimensional change rate, post-heating condition and surface finish.

Mixing equipment

Mixing ingredients is an important part of the production of PVC profiles. The mixing process is not only the mechanical mixing between the components, but also the process of friction and collision between the components, and the materials are continuously heated and gradually gelled. Therefore, the quality of the dry blend directly affects the physical properties and chemical properties of the PVC profiles. . Foreign experts believe that a good mixer can make up for the poor plasticizing extruder, but even the best extruder can not make up for the shortage of the mixer, the importance of the mixer.

Analysis of common problems in the extrusion process