Unsaturated polyester resins are produced by the polycondensation of saturated and unsaturated dicarboxylic acids with glycols. Unsaturated polyester resins form highly durable structures and coatings when they are cross-linked with a vinylic reactive monomer, most commonly styrene. The properties of the cross-linked unsaturated polyester resins depend on the types of acids and glycols used and their relative proportions.
On their own, cross-linked unsaturated polyester and vinyl ester resins have limited structural integrity, so they are often combined with fiberglass or mineral fillers before cross-linking to enhance their mechanical strength. Resins combined with fiberglass are referred to as fiberglass-reinforced plastic (FRP). Both lightweight and durable, FRP composites are consumed primarily by the construction, marine and land transportation industries, although they find use in a variety of other applications. Nonreinforced cross-linked unsaturated polyester resin is used to make cultured marble and solid surface countertops, gel coats, automotive repair putty and filler, and other items such as bowling balls and buttons.
The North American market, with four producers representing 82% of total capacity, is relatively concentrated, while the Western European market has four producers accounting for 70% of total regional capacity. The Japanese industry is composed of four major producers, accounting for 77% of total capacity.
The following pie chart shows world consumption of unsaturated polyester resins:
The world market is consolidating and shifting to China, India and other Asian countries (excluding Japan, the Republic of Korea, and Taiwan). The market is at continued high risk for consolidation of some regional producers to increase the number of global players.
The recycling potential for unsaturated polyester is poor. The automotive industry, for one, is trying to reduce the number of polymers and use mainly unreinforced thermoplastics that can be more readily recycled. In Japan, recycling of used products (waste) is the key issue allowing the expansion of UPR markets.
The unsaturated polyester resin industry is mature and largely dependent on general economic conditions. Consumption growth will be highest in China, with an average annual growth rate of just over 5% for 2011–2016; growth in Asia will increase at an average annual rate of almost 5% during that time frame. The Middle East and Africa will also have an average annual growth rate of almost 5%. Central and Eastern Europe will have an average annual growth rate of about 4.5%, as will Central and South America. Consumption will grow in North America at an average annual rate of 3.5%. In Japan, unsaturated polyester resin consumption will grow at an average rate of 0.7% per year during the period.