9 Jul, 2019 By Johny 2 Comments
In the manufacturer process of Hand Lay Up after Resin gels,why does it become soft,non-hardened or low strength?
1.Low amount or active ingredient of curing agent and accelerator in hand lay up process.
The amount of curing agent (MEKP, CHP) should not be less than 1%, so as to ensure that there are enough free radicals to initiate the full curing of resin. The effective content of cobalt salts accelerators should be above 0.8%. Low effective content will increase the amount of accelerators. The introduction of too many small molecular diluents will lead to poor curing of the resin. Therefore, when buying accelerants, don't be greedy for cheapness. Buy a large number of accelerants with diluents at low prices, which can't achieve the use effect of resin because of small losses.
Choose the appropriate solid accelerator system and check whether the curing agent and accelerator are invalid. Peroxide curing agent storage for a long time will also lead to a decrease in activity. A small test is needed to confirm the applicability of the curing agent with a long storage time before it is used in large quantities. It is better to buy it now. It is also possible to forget to add curing agent or accelerant in the construction process, or there is no accurate measurement when weighing. It is strongly recommended that special mixing personnel and weighing and measuring equipment be equipped in the construction.
2.Reactivity of resin and curing agent is not suitable in hand lay up process.
Usually unsaturated polyester resins have higher activity than vinyl ester resins, so unsaturated polyester resins are more suitable for curing agents with higher activity, such as methyl ethyl peroxide (MEKP) with high content of small molecule peroxides (such as hydrogen peroxide), and some MEKP products on the market are added with large amount of small molecule peroxides to improve the content of reactive oxygen. This kind of curing agent is often used for curing unsaturated polyester resin. There is no obvious problem for curing agents. If cured for vinyl ester resin, it may cause bad curing after gel. This is mainly due to the large number of small molecule peroxide in the initial reaction of gel. It can be seen that a large number of bubbles can not produce enough free radicals after the initial setting of the resin to make the resin fully cured. Emphasize again not to buy solid and accelerator products with too low price.
3.Low temperature in using environment, resin, base or tooling in fiberglass hand lay up process:
Using environment, resin, base or mold temperature as far as possible to maintain at 15-30 ℃.
4.Resin bulk has a long post-curing time.
According to different process requirements, resin suppliers may provide different active resins, such as large FRP products, summer high temperature formula, etc. the resin body activity is slower and the gel is slower. Before use, the resin should be communicated with the resin supplier to select the suitable resin.