Processing aids Although rigid PVC has high viscosity, its melt strength is low, and melt fracture may occur at normal shear rates. After adding processing aids, it is entangled and adhered with PVC. , Can effectively prevent melt fracture, significantly improve its tensile strength, bending strength, elongation at break, impact strength and appearance quality, which is very important for high-speed extrusion to increase productivity Meaning. ACR Processing Aid The molecular structure of processing aids determines the intrinsic properties. Different molecular weights have different effects on processing aids. Different molecular weight and viscosity have a great influence on PVC melt plasticization performance and melt strength. And the appearance of products have different effects. According to its melting point and molecular weight, it can be divided into lubricity, promote plasticization, and improve strength. Low molecular weight processing aids mainly act as internal lubricants and plasticizers. Although plasticized Fast speed, good material dispersion, good for plasticization, but bad for melt strength. Medium molecular weight processing aids mainly play a role in promoting plasticization. Medium viscosity is mostly used in the production of profiles and pipes Number of ACR. High-molecular-weight processing aids can increase the strength of the melt through the entanglement of the molecular chain on the resin. Collectively referred to as foaming regulators in rigid low-foaming products. Processing aid zone with ACR In addition, the molecular weight of the former is above 300W, the molecular chain is longer, the viscosity is higher, the entanglement between the PVC molecular chains is relatively strong, the pressure is high, the melt strength can be improved, and the later plasticization ability is strong . The disadvantage is that the plasticization speed is slow, the fluidity is poor, and the plasticization temperature needs to be increased; the molecular weight of the former is generally about 20W-30W, and the melting point is low. It is first plasticized in the PVC melt and has good compatibility with PVC. , It can adhere to PVC particles, increase friction, generate internal heat, and improve the transfer of melt heat and shear force. Under the condition of less external heat supply, it can promote PVC plasticization, and the melt flow and heat transfer performance are good. , The plasticizing speed is fast, and the plasticizing degree is balanced, but the melt viscosity and strength are low. The two are the same type of material, and the molecular weight is very different. The molecular weight has a great relationship with the melt extension ability, and the promotion of plasticization decreases with the increase of molecular weight. Therefore, ACR cannot replace Foam regulators and foam regulators cannot replace ACR either. Foaming regulator The processing aid ACR is a high molecular polymer with low melting point, high molecular weight and intrinsic viscosity, and high friction coefficient. After plasticization, it can be uniformly dispersed and filled into the gaps of PVC particles. It becomes a flowing heat conductor, and at a relatively low temperature of about 160 degrees, PVC can be transformed into a shear-flowing wall-sticky melt, which increases the friction characteristics and wall-stickiness of the material. Eliminate only adding stabilizers The phenomenon that rigid PVC and lubricants slide in the extruder can effectively promote plasticization and reduce the melting process without increasing the plasticization temperature. The presence of processing aids may change the solubility of other additives in PVC, and the effect on lubricants is particularly important. Due to the change of melting degree, some internal lubricants may migrate Increased and converted to external lubrication, but will increase the sliding wall performance, when encountering this situation, the amount of lubricant should be adjusted appropriately, or the lubricant should be changed. ACR processing aid is commonly used in the extrusion of plastic door and window profiles. The domestic grades are ACR-401 and ACR-801, both of which have similar performance, and 801 has better effects.
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