Calender

The calender generally adopts the vertical three roll calender. When used for film production, the middle roller is fixed, and the speed ratio of the middle roller is (1.1 ~ 1.4) ∶1 faster than that of the upper roller. The speed of the lower roller is the same as that of the middle roller. When the calender is started, the temperature of the upper roller should be 50℃, the middle roller should be kept at room temperature, and the lower roller should be cooled with cooling water. Calendering speed is generally 60 ~ 300cm? Min-1, not too fast, first adjust the roll distance (middle and lower rolls) at a low speed to ensure a certain calender thickness, and then increase to the normal speed for continuous operation.

Glue
Gumming refers to the silicone rubber rubber slurry with dipping or scraping method evenly distributed on the fabric to improve the strength and flexural properties of film products, so that the fabric moisture resistance, in order to produce high temperature resistant electrical insulation materials.

(1) Preparation of glue
The vulcanization agent of silicone rubber compound used for making rubber slurry is mostly benzyl peroxide (BP), the dosage is slightly larger than that of general model products. If the reinforcing filler is used in the gas phase method, the dosage should not exceed 40 parts, and appropriately increase the dosage of the structure control agent, and use toluene or xylene and other volatile solvents.

(2) Fabric pretreatment
Silicone rubber coating with the bottom of the fabric generally used glass cloth, nylon and polyester. The glass cloth has many applications because of its good heat resistance, high strength and low hygroscopicity. In the process of drawing, glass fiber film is coated with paraffin lubricant (accounting for 0.2% ~ 0.5% of the quality of the fabric), which is volatile at the vulcanization temperature, which affects the combination of the glue and the fabric, and must be dewaxed before coating. The thermal deformation of nylon and polyester is large, which affects the combination of rubber and fabric. Therefore, the thermal setting must be carried out before the glue is applied, that is, the fabric is subjected to a short heat treatment under a certain drawing. The treatment temperature of nylon is 170 ~ 175℃, and the treatment temperature of polyester is 215 ~ 220℃.

(3) the glue
Fabric after pretreatment, but also for surface adhesive treatment, and then can be coated with glue. The adhesive is a solution consisting of alkoxy silane, borate, curing agent and solvent (ethyl acetate or ethanol).

Bond
Silicone rubber can be bonded with many materials, including metals, plastics, ceramics, fibers, silicone rubber itself and some other rubber. The adhesive that can be vulcanized at the same time with silicone rubber itself can make the best bonding between silicone rubber and the coating. The bonding between silicone rubber vulcanizates is generally adhesive. Examples of common adhesive formulations are as follows: vinyl silicone rubber 100; Gaseous silica 35; Ferric oxide 5; N-butyl borate 3; Paste curing agent DCBP 3.