Polyester resins are liquid solutions of the polyester and cross-linking monomers. The polyester itself is made in plants that ensure specific technical parameters, e.g. high temperature heating (above 200ºC) and fast cooling. Once it has been made, it is dissolved in styrene as standard to form a polyester resin. Depending on the target application of the resin (e.g. polymer concrete, laminates or others), it is modified with various additives, such as those reducing the emission of volatile substances into the atmosphere (paraffins), lowering the heating temperature at curing (copper compounds) or improving curing (amines).

From a chemical point of view, the application of polyester resin is based on an irreversible process of transition into a solid state during cross-linking. From the point of view of the processor, it is a curing process with the use of an accelerator and a curing agent. Cobalt compounds and peroxides are most commonly used in this stage. Polyester resins always act as a binder for other materials, which, depending on the application, are glass fibres, carbon fibres or various types of mineral fillers. These resins show very good resistance to water and to various other substances, including inorganic hydracids and diluted oxidizing acids. Products based on polyester resins also have good mechanical and electrical insulating properties, which account for their constant and high popularity on the markets.


Estromal® unsaturated polyester resins produced by LERG are based on a wide range of starting materials:

  • • Orthophthalic
  • • Terephthalic
  • • Isophthalic
  • • Iso/npg
  • • DCPD

Resins produced under the Estromal® brand are used in virtually all known applications. They are used, among others, for the production of pipes and tanks of polymer concrete, castings, polyester-glass laminates (including for joining with acrylic and ABS boards in bathtubs and shower trays), garden figures as well as in the CIPP technology of trenchless repair of sewer systems. Estromal® resins intended for the production of boats are certified for this application by Germanischer Lloyd. Estromal® terephthalic resins, which are made based on recycled PET, are particularly noteworthy. These resins have greater chemical resistance comparable to isophthalic resins. The state-of-the-art filtration system ensures that Estromal® resins come at a par with orthophthalic type polyester resins in terms of clarity and purity. All Estromal® resins undergo a multi-stage control process, which guarantees conformity to the declared specifications and supply of resins with fixed physical and chemical properties.

Polymer concrete

This modern product of a multitude of applications is used with a range of highly reactive resins with the parameters closely adjusted to the individual Customer’s requirements. Polymer concrete is an excellent material for the manufacture of pipes, sewer wells, manholes, linear drainage, fencing, etc.

Polyester-glass laminates

ESTROMAL® ortho- and terephthalic resins for the production of polyester-glass laminates are pre-accelerated, thixotropic resins with reduced styrene emission during processing. Construction orthophthalic resins used for the production of floating equipment are certified by DNV.

CIPP resins

This modern technology goes with a number of resins of high mechanical and chemical resistance properties. Each product can be tailored to fit our Customer’s strict requirements. Our ESTROMAL® resins show good processing parameters and finished goods reveal excellent parameters, particularly chemical resistance and mechanical strength.


We offer polyester resins for use as adhesives in the production of blasting cartridges. These resins are characterized by a low viscosity, high stability over time and excellent strength parameters.

Fancy goods

Polyester resins designed for processing by casting and centrifugal moulding methods. These are medium-reactive orthophthalic colourless resins, characterized by flexibility and transparency.

RTM composites

Our ESTROMAL® resins are characterized by low viscosity, very good mechanical properties and a high HDT. They are perfect for the production of repeatable and precision components in the RTM technology, such as housings and car body parts.

Bathtubs and shower trays

ESTROMAL® resins designed for the reinforcement of ready-made acrylic products, i.e. bathtubs and shower trays. They are characterized by a low exothermic peak and good adhesion to acrylic and ABS.

Artificial marble

When the mixture is prepared, polyester resins accept large amounts of fillers, and during post-curing, they are characterized by a low exothermic peak. Finished products show minimal shrinkage.


Polyester resins based on terephthalate are characterized by excellent processing parameters. They offer low viscosity, and a specially selected mixture ensures short post-curing times.


Vinyl ester resins are made in a reaction of epoxy resin and unsaturated monocarboxylic acid, followed with dissolution in styrene or other acrylic reactive monomer. The processing is similar to that of polyester resins; these products are recommended for use in the manufacture of materials exposed to adverse environmental conditions, i.e. high temperature, corrosive agents, stresses, and contact with water.

Vinyl ester resins are characterized by:

• high resistance to a range of chemical compounds, comparable to that of epoxy resins,
• their use enables the production of flexible and highly thermally resistant composites,
• excellent adhesion to glass, carbon and aramid fibres,
• excellent resistance to osmosis and hydrolysis,
• good adhesion to elements made of polyester and epoxy resins.

Key application industries:

• construction – in the production of tanks, pipes, scrubbers, chimneys, chemical plant components, wind turbines, CIPP (cured-in-place),
• transport – in the production of railway car parts, truck panels, vehicle bodies, yachts,
• in the construction of swimming pools.


ESTROFTAL® saturated polyester resins made by LERG find a wide range of applications in the production of paints and varnishes.

PAINTS AND VARNISHES At the core of our offer is the range of ESTROFTAL® resins intended for the production of alkyd paints. We have also developed a “high solid” resin version for the most demanding Customers.
Estroftal® are fatty alkyd resins modified by oil of plant origin. These are polyesters whose solvent is odour-free naphtha. Consequently, toxicity is reduced to a minimum, and the finished product gives off mild odour.
Estroftal® are flexible resins, so the finished product (paint, enamel, base) shows high resistance to mechanical damage and a superb adhesion to the surface. There is no shrinking in volume when the coat sets, no micro or macro cracks.
A novelty among our variety of alkyd resins is Estroftal® PLS 651B80 of a high content of non-volatile matter (80%) and low emissions of volatile organic compounds (VOC).

Ask about product

Agnieszka Motak


t: +48 14 680 63 86

k: +48 660 738 126

Zbigniew Heller


t: +48 14 680 63 35

k: +48 602 660 301

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