For rigid PVC heat shrinkable film, it is best to use suspension type 6 or 7 resin. Although the heat shrinkable film for wire and cable connection, its volume resistivity is not as high as that of type 2 or 3 resin, but type 7 The resin has good moldability, and production practice has proved that it is difficult to mold when using type 2 or type 3 resin. The hard PVC heat shrinkable film produced is hard and brittle and cannot be folded and wound. When the pvc film is plasticized with a plasticizer, the heat shrinkage temperature decreases with the increase of the plasticizer content. For example: using suspension type 3 PVC resin powder, adding 30 ~ 50 PHR DOP plasticizer, can be in 70 Two-way stretching at a temperature of about ℃, its products can shrink at about 40 ℃, can not be stored on hot days.
Moreover, as the plasticizer content increases, the volume resistivity of the heat shrinkable sleeve for wire and cable decreases. Therefore, when producing PVC heat shrinkable sleeve for wire and cable joints, we still use 6 or 7 type resins that are easier to process. In order to improve the insulation, the transparent PVC film uses the thermal stabilizer combined with tri-salt and di-salt and appropriately increases the thickness of the film to ensure the insulation. P83 nitrile rubber not only has good processability, elasticity, cold resistance, but also can improve the strength and improve the stress crack resistance of PVC products. Active CaCO3 mainly improves product insulation, flame retardancy, and reduces costs.