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What are the physical and chemical properties of unsaturated polyester resins?

Nov 28, 2018

Physical and chemical properties of unsaturated polyester resins

1. Physical properties the relative density of unsaturated polyester resin is about 1.11 ~ 1.20, and the volume shrinkage rate is large during curing. Some physical properties of the cured resin are as follows:

Heat resistance.The vast majority of the thermal deformation temperature of the unsaturated polyester resin in 50 ~ 60 ℃, some good resin heat resistance up to 120 ℃.Red heat expansion coefficient alpha 1 (130 ~ 150) x 10-6 ℃.

The mechanical properties.Unsaturated polyester resin has high tensile, bending and compression strength.

Chemical corrosion resistance is good.Unsaturated polyester resin resistance to water, dilute acid, dilute alkali performance is better, poor resistance to organic solvents performance, at the same time, the chemical corrosion resistance of resin with its chemical structure and geometric switch, can have great differences.

Of dielectric properties.The dielectric properties of unsaturated polyacid resin are good.

2. Chemically unsaturated polyester is a linear polymer compound with multifunctional groups. It has polyester chain bonds and unsaturated double bonds on its backbone chain, while carboxyl and hydroxyl groups are present at both ends of the macromolecular chain.

The double bond on the main chain can be copolymerized and cross-linked with the vinyl monomer to change the unsaturated polyester resin from soluble and fusible state to insoluble and fusible state. 

Ester bonds on the main chain can undergo hydrolysis reactions, which can be accelerated by acids or bases.If copolymerized with styrene and crosslinked, hydrolysis reaction can be greatly reduced.

In acidic media, hydrolysis is reversible, not complete, so polyester can withstand the erosion of acidic media;In alkaline media, due to the formation of resonant stable carboxylic acid anion, hydrolysis becomes irreversible, so polyester alkali resistance is poor.

Carboxyl groups at the end of polyester chain can react with alkaline earth metal oxides or hydroxyl compounds [such as MgO, CaO, Ca(OH)2, etc.] to expand the molecular chain of unsaturated polyester and eventually form complexes.Molecular chain expansion can make the initial viscosity of the viscosity of the liquid resin 0.1 ~ 1.0pa ·s viscous, in a short period of time, the viscosity increases to more than 103Pa·s, until it becomes a non-flowing, non-stick hand like gel.When the resin is in this state, it is not crosslinked. It can still be dissolved in suitable solvent and has good fluidity when heated.


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