3.Uneven foam hole (too large or too small)
If the foam hole is too large, the hardness and density of the product are not up to standard, the closed hole will become a joint hole, the microhole will become a small hole, and some parts will collapse or some parts will not rise.
The reason:
(1) foaming agent clumps or particles are too coarse;
(2) mixing is not uniform;
(3) The water content of the compound is too high, and there is air or impurities mixed in the rubber material;
(4) insufficient vulcanization, continue to hair holes after the mold.
Countermeasures:
(1) Check the foaming agent, if there is clumping phenomenon should be sifted, coarse particles should be crushed, fully mixed (or thin) to disperse evenly;
(2) Too much water in the compound should be used after drying, remove the air or impurities in the compound, and make it fully vulcanized.
4. Over-curing or under-curing
(1) Overvulcanization
General surface discoloration, small holes, high hardness, product edge split, the cause is improper operation, or general surface discoloration, small holes, high hardness, product edge split, the cause is improper operation, or the temperature is too high, vulcanization time is too long or instrument failure, should check whether there is a problem with each valve and instrument, and then strictly implement the operating rules.
(2) undervulcanization
When the vulcanization is insufficient, the internal pressure of the pores is greater than the external pressure, and if the rubber continues to perforate, the hardness is too low, the strength is poor, and the deformation is large. Heavy hole burst. Check whether there is a problem with the instrument and valve, and strictly follow the operating rules.
Note: Foam products control quality index
(1) The apparent density, the smaller the better;
(2) Mechanical strength is generally 0.5-1.6Mpa;
(3) static compression permanent deformation;
(4) hardness;
(5) impact elasticity;
(6) continuous fatigue;
(7) aging test (70 degrees *70 hours; 100 degrees *24 hours);
(8) Low temperature test.
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