In hand lay-up and spray forming, the resin is layered over the open mold. In particular, spray molding, resin spray, part of the mist, deposited, and thus, before the resin is fully cured, Styrene is continuously volatilized from the resin and is emitted into the air of the workshop. This part loses a part of styrene and pollutes the environment on the other hand. Especially in the case of insufficient ventilation in the workshop, the styrene content in the air is high. Workers have long been in this atmosphere and are harmful to health. Therefore, countries around the world have set the threshold limit (TLV) for styrene, which is the average styrene concentration in the air measured in a 40h working week on an 8h working day. The highest value. For example, the threshold value of styrene in the United Kingdom and the United States is 100, that is, the highest content of styrene vapor in air is 100g/m3. Sweden is 50g/m3.
In order to ensure that the air in the workshop is below the threshold limit, the workshop must be ventilated. However, ventilation alone will bring down the room temperature in winter and increase the cost of air conditioning. Therefore, the amount of styrene in the polyester resin must be reduced.
The early low-wafer resin contains a small amount of paraffin as a volatilization inhibitor. When cured, a wax film is formed on the surface to isolate the resin from the air. However, after the wax is added, the layering of the laminate is easily caused.
Later, it was improved to use a combination of high melting point and low melting point paraffin and various polymers, such as polybutylene fumarate, polybutyl acrylate.
There is also a volatilization inhibitor (such as paraffin) and a compound called "adhesion promoter". This adhesion promoter is a hydrophobic ether with two hydrocarbon groups and at least one double bond per alkyl group. Ester; there are unsaturated isoprene (meta) compounds and ethers or esters thereof, such as linseed oil, dipentene and trimethylolpropane dienyl ether, etc. The amount of paraffin is 0.05%~0.5 % (mass fraction), the amount of adhesion promoter is 0.1% to 2% (mass fraction)
In addition, in order to reduce the volatilization of styrene, the amount of styrene can be reduced, or some (or all) styrene can be replaced by a low volatility monomer. However, lowering the styrene content causes a decrease in the performance of the resin after curing, and other substitutes tend to Not comparable to styrene (low styrene price, more sources, better overall performance)
In order to reduce the volatility of styrene, the process of hand lay-up and spraying process is also promoted to the closed mold forming (such as resin injection molding process).