Mixed modified heat shrinkable tube
日期：2022/3/17 8:45:07 / 閱讀： / 來源：本站
Mixed modified heat shrinkable tubeFor the connection of insulated wires, especially the tight and beautiful connection of two kinds of insulated wires with different diameters, heat shrinkable tubes shall be used. Common gauge shrink tubes include PVC heat shrink tubes and PE heat shrink tubes. PVC heat shrinkable pipe has the advantages of flame resistance and good flexibility, but the heat shrinkable rate is low, so it is not suitable for the connection of insulated wires with large diameter difference; PE heat shrinkable pipe has high heat shrinkable rate. However, the disadvantage is that it is flammable, and when it is cured by electron beam irradiation, the surface is uneven and the appearance is poor. PVC resin and CPVC resin are mixed, and polytetrafluoroethylene powder and corresponding additives are added at the same time The heat shrinkable tube was prepared. The tube is flame-retardant, soft, has high thermal shrinkage, tight and beautiful wire joints, and will not crack at high temperature.
1. Material selection and formula design (1) the average polymerization degree of PVC is 1300 industrial grade; PVC, average polymerization degree 2500, industrial grade; CPVC, chlorine content 63%, industrial grade; DOP, industrial grade; Pn150, produced by greater Japan ink industry company; Polytetrafluoroethylene powder, industrial grade; Tribasic lead sulfate (tribasic salt), industrial grade; Stearic acid, industrial grade; Clay, industrial grade; Light CaCO, industrial grade. (2) The average polymerization of VC resin is 800 ~ 3000, preferably 1200 ~ 1500. In this range, the processing performance is good. If the chlorine content of CPVC resin exceeds 70%, the processability and thermal stability will become worse, and the chlorine content is preferably 63% ~ 65%. The mass ratio of PVC resin to CPVC resin should be 90:10 ~ 50:50. If the amount of PVC resin is more than 90 phr and CPVC resin is less than 10 phr, the shrinkage will be reduced. If the amount of PVC resin is less than 50 parts and the amount of CPVC is more than 50 parts, the processing performance becomes worse. The dosage of polytetrafluoroethylene should be 1 ~ 10 parts in 100 parts of basic resin (i.e. PVC resin and CPVC resin). If it is less than 1 part, the pipe is easy to break during expansion; If it is higher than 10 phr, the mechanical properties and extrusion processability of the composite are not good, and the best dosage is 3-5 phr. The dosage of plasticizer depends on the hardness and heat resistance of the product, and the general dosage is 40 ~ 70 parts. Three salts are selected as heat stabilizers, preferably three salts, dibasic lead stearate, lead stearate and calcium stearate. These four heat stabilizers are used in combination, because there is a "synergistic effect" between them, which is better than that of a single tube
The thermal stability effect of using three salts alone is better.
2. Main equipment: Banbury mixer, single screw extrusion granulator, single screw pipe extruder, expansion rate and thermal shrinkage detection device.
3. Preparation process (1) process flow: batching → internal mixing → granulation → pipe extrusion → determination of expansion rate → determination of thermal shrinkage rate.
(2) Molding process 1) ingredients. Ingredients according to the formula requirements. 2) Internal refining. Put the prepared material into Banbury mixer for internal mixing to make each component mix evenly. 3。 Put the good material into the single screw extrusion granulator for granulation. 4。 The good material is put into the single screw pipe extruder and extruded into a pipe; The extruder temperature is 140-170 ℃.
4. Determine the inner diameter a of the extruded tube by measuring the expansion rate, and then heat the tube at 140 ℃ to expand the tube as much as possible, and measure the inner diameter B of the expanded tube. Calculate the expansion rate of the pipe according to the following formula: expansion rate = - X100% thermal shrinkage measurement. It has been measured that the inner diameter of the expanded pipe is B. cool and harden the expanded pipe, and then measure the inner diameter C of the cooled and hardened pipe. Calculate the shrinkage of the thermal expansion pipe according to the following formula: thermal shrinkage = No. X100%