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What are the general characteristics of unsaturated polyester resins?

Jan 23, 2019

General properties of unsaturated polyester resins

Resin is a commonly known, refers to the manufacture of plastic products used by the polymer raw materials, any of the raw materials can be called resin.Polyester is a polymer formed by the condensation of dicarboxylic acid and diol.Polyester resins can be divided into two categories: saturated polyester resins, which have no non-aromatic unsaturated bonds in their molecular structure, such as polyethylene terephthalate.It is a thermoplastic resin that can be injected into a "polyester" fiber or made into a film, a "polyester" film.The other is unsaturated polyester resin, which contains non-aromatic unsaturated bonds in its molecular structure and can be cross-linked by appropriate initiator to become a thermosetting plastic.The unsaturated polyester resin described in this paper belongs to this category and is often referred to as polyester for convenience.Before curing, unsaturated polyester molecules are long-chain molecules, whose relative molecular weight (hereinafter referred to as molecular weight) is generally 100 to 3000. Such long-chain molecules can be cross-linked with unsaturated monomers to form large network molecules with complex structures.

This network molecule comes in three forms.

(a) is a roughly uniform continuous network structure;

(b) is a non-uniform continuous network structure, in which there are less dense chain molecules connecting with each other between the dense continuous network

(c) is a discontinuous network structure, and a dense continuous network is dispersed among unbonded components.

Unsaturated polyester resin curing mainly formed a second kind of network structure of macromolecules.This structure can be studied by electron microscopy or by observing the swelling process of the resin.Unsaturated polyester is the most commonly used resin in reinforced plastics.In the field of reinforced plastics, the amount of thermosetting resin accounts for about 75%, and the amount of thermoplastic resin is increasing.There are a variety of thermosetting resins, of which the amount of unsaturated polyester is much higher than other resins, because unsaturated polyester has a particularly favorable processing conditions, and cheap price.For example, although the price of phenolic resin is lower than polyester, but in the process of curing to discharge water, the formation of steam, must use a higher molding pressure (generally 8 ~ 30MPa) and heating conditions, so the need for a larger press to produce.Unsaturated polyester does not emit water or other by-products during curing, so it can be formed at lower pressure and temperature.In fact, unsaturated polyester is widely used in room temperature and contact pressure processing into a variety of products, which is incomparable to other resins.The performance comparison of polyester and other two commonly used thermosetting resins after curing is shown in table 1-1.Although unsaturated polyester resin can become insoluble and infusible thermosetting material after curing, its mechanical properties are very low, which cannot meet the requirements of most applications.Such as glass fiber reinforced into a composite material, commonly known as glass fiber reinforced plastics.It has light weight, high strength, resistance to chemical corrosion, electrical insulation, microwave penetration and many other excellent performance, and the molding method is simple, can be a large molding or a complex configuration of products, has become a new material with great advantages.

The specific strength of PFRP is higher than that of steel, duralumin and fir, but the specific modulus is lower.After reasonable structural design, it can make up for the lack of elastic modulus, and give full play to its high specific strength and other excellent performance.


QuanZhou Neweco High Polymer Material Co.,Ltd.

Neweco is one of the leading unsaturated polyester resin manufacturers and  suppliers,widely used in automobiles, ships, rail transit, wind power  generation, pipe cans, heat and corrosion protection, building  materials, stone repair, sanitary ware, artificial stone and other  industries. Suitable for hand lay-up, spray, pultrusion, winding,  molding, vacuum introduction / RTM, casting and other molding processes. Neweco Resin is committed to excellence and focuses on the application  of composite materials to provide customers with comprehensive  solutions.

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