Unsaturated polyesters are highly versatile and can be tailored for a wide range of applications depending on the raw materials used. These resins are typically formed by the reaction of dibasic acids or anhydrides with glycols, followed by the addition of vinyl monomers to act as crosslinking agents. In industrial production, unsaturated dibasic acids or anhydrides such as maleic anhydride, fumaric acid, and tetrahydrophthalic anhydride are commonly employed. On the other hand, saturated dibasic acids like phthalic anhydride, isophthalic acid, and adipic acid are also frequently used, depending on the desired properties of the final product. The most common glycols in the formulation of unsaturated polyesters include propylene glycol, diethylene glycol, and dipropylene glycol, which contribute to the flexibility and mechanical strength of the resin. For crosslinking, vinyl monomers such as styrene, methyl methacrylate, and diallyl phthalate are added to enhance the curing process and improve the overall performance of the material. In addition to these primary components, various additives play a crucial role in the final characteristics of the polyester. These may include polymerization inhibitors to control the reaction, catalysts or initiators to speed up the curing process, accelerators to improve efficiency, fillers to modify physical properties, dyes for coloration, and lubricants to aid in processing. The combination of these ingredients allows for the customization of unsaturated polyesters to suit specific industrial needs. Among the many possible formulations, the most widely used unsaturated polyesters are those synthesized from maleic anhydride, phthalic anhydride, and propylene glycol. This blend provides a good balance of cost, performance, and versatility, making it ideal for a variety of applications, including laminates, coatings, and composite materials. Steel box girder and steel and concrete composite box girder are used for large spans, which need to minimize the weight of the bridge, and their excellent high torsional stiffness is particularly useful. The clean lines of the box girder bridge usually have no obvious external hardening. It is generally considered to have excellent appearance and durability, and it has no traps for dust and moisture. Box-shaped cross-sections are sometimes used as compression members, such as in cable support structures or arched towers. Box Girder Formwork,Box Girder Structure,Metro Box Girder Formwork,Bridge Box Girder Formwork Anshan Lijian Engineering Group Co. LTD , https://www.lijianformwork.com
Unsaturated polyester - raw materials