The curing of unsaturated resins is the process of linear macromolecules forming a three-dimensional network through the action of crosslinking agents, but the curing process cannot consume all the active double bonds in the resin to reach 100%. Degree of cure. In other words, the degree of curing of the resin is difficult to achieve. The reason is that in the late stage of the curing reaction, the viscosity of the system increases sharply, which hinders the diffusion. Generally, it can only be considered that the curing is complete when the material properties tend to be stable.
The degree of curing of the coating resin has a great influence on the performance of FRP. The higher the degree of curing, the mechanical properties, physical and chemical properties of FRP products are fully exerted. Some people have done experiments to test the physical properties of UPR resin at different stages after curing, and the results show that its bending strength does not increase with time, and it does not stabilize until one year later. In fact, for the glass fiber reinforced plastic products that have been put into use, one year later, due to the aging of heat and light and the corrosion of the medium, the mechanical properties began to gradually decline again.
There are many factors that affect the degree of curing. The composition of the artificial stone resin itself, the amount of initiator and accelerator, curing temperature, post-curing temperature and curing time can all affect the degree of curing of the polyester resin. Vinyl resin, also known as epoxy acrylic resin, is a new type of resin developed in the 1960s. It is characterized by unsaturated end resins in polymers.
Vinyl resin has good comprehensive properties: ① Because the unsaturated double bond is located at the end of the polymer molecular chain, the double bond is very active, and it is not affected by steric obstacles during curing, and can be passed through the phase under the trigger of organic peroxide It can be cross-linked and cured between adjacent molecular chains, and it can also be cured with monomer styrene; ②The R group in the resin chain can shield the ester bond and improve the chemical resistance and hydrolysis resistance of the ester bond; ③Vinyl resin The ester bond per unit relative molecular mass is about 35%-50% less than that of ordinary unsaturated polyester, which improves the hydrolytic stability of the resin in acid and alkali solutions; ④Secondary hydroxyl groups on the resin chain Wetting and bonding with glass fiber or other fibers to improve the strength of the composite; ⑤ epoxy resin main chain, which can impart toughness to the vinyl resin, the ether bond in the molecular main chain can make the resin have excellent acid resistance Sex.