In the case of high ambient temperature (higher than 30 ℃), the amount of accelerator (such as cobalt) and the amount of curing agent can be reduced to prolong the gelation time. The effective cobalt content of cobalt salts promoters in the market is 0.6-8%. In order to facilitate site construction weighing, low concentration cobalt salts promoters can be selected.
The addition of MEKP curing agent should also be strictly controlled to no less than 1% to ensure that the resin can be fully cured. It is suggested that the amount of cobalt ISO octanoate with cobalt content of 1% should not be less than 0.2%. If the curing agent and accelerator have reached the minimum, the recommended dosage can not meet the construction requirements. It is also possible to prolong the gel time by adding inhibitor.
Heat or UV can also cause curing agent and resin curing. When the temperature is higher or the sunlight is direct, the gelation time of the resin will be greatly shortened.
If the site gel time is very fast and affects the construction speed, the following methods can be used to speed up the batching speed:
First, a small test was made to determine the amount of solid and promoter and adjust to the appropriate gel time. A batch resin (such as 100kg) was added to the accelerator 2 times the weight of the small test. Another batch of resin was added to the curing agent which was 2 times the amount of the small test. Two kinds of premixed compound of the same volume are taken in the preparation of the compound, and the construction can be completed after the mixture is uniform. This method is easy to weigh curing agent and accelerator, easy to disperse uniformly, and short batching time. It should be noted that the resin of premix and accelerator should be used up as far as possible in the same day, especially the compound with curing agent should be placed away from light.
High and Medium Temperature Curing：
It is suitable for hot pressing or pultrusion process. The common curing systems are oxidized benzoyl (BPO) paste and tert-butyl peroxide benzoate (TBPB) initiator, and the curing effect is good. The initiator used in warm curing processes such as pultrusion and winding is:
1.Benzoyl peroxide (BPO): dosage is 1.0-2.0%, suitable temperature is 80 ~120℃.
2.Tert-butyl peroxide benzoate (TBPB): 1.0-2.0% dosage, suitable temperature 120 ~150 ℃.