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Common problems and solutions of mixing silicone rubber

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1. Raw rubber eats powder slowly

1. The molecular weight of raw rubber is high,
2. Raw silicone rubber with trifunctional groups slightly cross-linked in DMC

deal with:
1. Select the appropriate molecular weight of raw rubber or reduce the molecular weight of raw rubber to use
2. Appropriately add 500cs~1000cs dimethyl silicone oil or low molecular weight or water during mixing

2. The transparency of the rubber compound is poor

1. Silica particles are hard to disperse.
2. The low molecules are not removed completely, and there is fog in the vulcanizate
3. The number of wrapping rolls is not enough
4. Dirt in raw materials
5. Poor sanitation
6. The equipment is poorly sealed, and dirt enters the glue when vacuuming
7. Short high temperature time during hot refining
8. Improper operation of nitrogen filling

3. The appearance of the glue is inconsistent

1. Color difference between batches of silica
2. The cooling time is inconsistent
3. The appearance of accessories is different

deal with:
1. Heat refining time and temperature should be uniform
2. Pay attention to the color difference between batches of silica, and replace it in time after it occurs
3. The glue should be sent out at the same time during delivery to prevent the glue from reacting with the air for a long time and causing the glue to change color.

Fourth, the unification of raw materials

1. High plasticity value of rubber compound
2. Roller temperature is too low

deal with:
1. Increase the roll temperature and turn off the cooling water
2. Control the appropriate mixing time
3. Add appropriate additives

5. Poor resilience

1. The formula of raw rubber vinyl is unreasonable
2. Too many additives
3. The refining time is not enough, and the infiltration of white carbon black and raw rubber is poor
4. High cooling temperature

deal with:
1. Add an appropriate amount of polyvinyl silicone oil to improve the vinyl
2. Appropriate dosage of dispersion
3. After the white carbon black is eaten, extend the cooling to 45min
4. Guaranteed cooling temperature

6. Poor tear strength

1. Raw rubber vinyl is unreasonable
2. Coarse white carbon black, small specific surface area
3, vulcanization is not cooked
4. The glue is brittle

deal with:
1. Use polyvinyl silicone oil or select vinyl raw rubber to adjust the vinyl content
2. Replace the silica filler, choose silica with large specific surface area and good performance, and replace the product with high quality grade
3. Adjust vulcanization amount and vulcanization time
4. Lower vinyl, adjust with methyl silicone oil or low vinyl raw rubber

7. Adhesive

1. The polymerization of raw rubber is not good, there are too many low molecular substances, or the molecular weight of raw rubber is too low
2. Vacuuming is not good
3. Excessive dosage of adjuvant
4. Less release agent
5, vulcanization is not cooked
6. The mold is not clean

deal with:
1. Exchange or send high molecular weight raw rubber for splicing
2. The degree of vacuum is properly controlled
3. Reduce the dispersing dose, use glue and glue together
4. Add release agent
5. Increase the temperature of the vulcanizate and prolong the vulcanization time
6. Regularly clean the mold
7. Use another type of release agent

8. Large permanent deformation

1. Unreasonable glue ratio, too much low molecular weight and low vinyl glue
2. Low vinyl
3. The vacuum is not good
4. Short curing time

deal with:
1. Add high vinyl raw rubber to increase vinyl content, or add additives as appropriate
2. Extend the vacuum time
3. Extend the high temperature kneading time

Nine, gum yellow

1. Raw rubber contains NH2 and CL- ions
2. Silica contains more Fe3+
3. Insufficient high temperature and short vacuum time
4. The choice of white carbon black is unreasonable, and the appearance is yellow
5, vacuum or nitrogen is not good

deal with:
1. Add anti-yellowing such as hydrogen-containing silicone oil, the purpose is to react with NH2 and CL- ions to generate NH3 and HCL when vacuuming
2. Ensure the high temperature time and temperature, otherwise the reaction of the auxiliary agent with NH2 and CL- ions will not be sufficient
3. Use other grades of silica
4. Guaranteed vacuuming and nitrogen filling time

10. Unpleasant powder during mixing

1. Less structural dose
2. The hydroxyl content in the structurant is too low
3. The molecular weight of raw rubber is high, and the molecular weight distribution is too narrow
4. There are micro-crosslinked silicone rubber raw rubber in the raw rubber
5. The amount of white carbon black and additives is not proportional. 6. The temperature of opening or kneading is too low

deal with:
1. Add structurant
2. Use raw rubber with uniform molecular weight distribution
3. Add in proportion to the structuring agent during feeding
4 Appropriately increase the opening or kneading temperature.

11. Explosion during rubber mixing

1. Methanol and ethanol flammable gases are produced
2. Friction produces static sparks during shearing
3. The equipment is not well sealed and the N2 protection is not enough

deal with:
1. Select substances that do not produce explosive substances or have a relatively narrow explosion limit as dispersants
2. The equipment is well sealed
3. Filling with nitrogen to isolate oxygen

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