Polyester resin - Things to know about polyester resin

Polyester resin results from the esterification of unsaturated and saturated dicarboxylic acids with alcohol. One speaks here of unsaturated polyester resin, i.e. polyester resin. The term unsaturated polyester resin results from the fact that some of the dicarboxylic acids involved in the reaction have carbon-carbon double bonds. These bonds are chemically unsaturated.

The fiber composite materials manufactured with the help of polyester resin belong to the group of duroplastics. Fiber composite materials are products that are usually made from a composite of synthetic resin and reinforcing fibers. In contrast to thermoplastics, thermosets are plastics that cannot be plastically deformed again after curing. They are insoluble, non-weldable and non-fusible.

Polyester resin forms the so-called matrix in a fiber composite material. The matrix is ​​the embedding material for the reinforcement fabric. The most common reinforcement fibers are glass fiber mats, glass filament fabrics, glass fiber fabrics and carbon fabrics. In addition, it ensures that the forces that occur are introduced into the fibers. The protective function of the matrix, which encloses and protects the fibers, should also not be neglected.

Polyester resin plays a prominent role in the processing of composite fiber materials. The main arguments for using polyester resin are the ease of processing and the lower price compared to epoxy resin, vinyl ester resin or polyurethane resin.

Polyester resin forms long-chain unbranched molecules when curing. The cross-branching of polyester resin can be forced by styrene, for example.

Due to the restriction on the shipping and sale of polyester resin containing monostyrene, a further development of polyester resin has recently started. Monostyrene-free polyester resins today achieve just as good and sometimes better production results. These can usually be processed and used in the same way as polyester resins containing styrene.

Polyester resin has the advantage that its processing time can be "adjusted" within a certain range by adding the amount of hardener. The curing time for polyester resin is usually determined by the pre-acceleration and the amount of hardener. In contrast to epoxy resin, which requires a precise ratio of epoxy resin to hardener, when processing with polyester resin, adding hardener allows for a certain degree of flexibility in the processing time.

Another advantage of polyester resin is its freedom of use in relation to the reinforcement fabric. Glass fiber mats, glass fiber fabrics or glass filament fabrics are usually used as reinforcement fabrics for components made of polyester resin.

It can be used with glass fiber mats, glass filament fabrics and glass fiber fabrics.

Processing polyester resin
A suitable working environment must be ensured at the beginning of the processing process. This includes a clean working environment to avoid later inclusions in the top layer. Gelcoat and topcoat are usually referred to as topcoat resin. Sufficient ventilation of the processing environment must also be ensured. In addition, all workpieces must be clean, dry and free of grease. Acetone is well suited for degreasing. Acetone is a cleaning agent and is also used as a solvent.

When working with fiber composite materials, it is recommended to wear disposable gloves with sufficient sensitivity. Fiber composite materials are products that are usually made from a composite of synthetic resin and reinforcing fibers.

The ambient temperature is of great importance. Polyester resin and also epoxy resin, gelcoat and topcoat are usually adjusted for processing at room temperature (20 °C). This should not be below 15 °C. 18-25 °C is ideal. At higher temperatures the pot life is reduced while at lower temperatures the pot life is increased. If the processing temperature is too low, this can lead to non-curing or non-curing of the polyester resin. The same applies to gelcoat and topcoat based on polyester resin.

The mixed quantity of polyester resin MEKP hardener should be tailored to the size of the workpiece. For example, with a large boat hull and a laminator, it is disadvantageous to mix the entire amount of polyester resin with the MEKP hardener right at the beginning if the specified gel time / gel time / open time is 30 minutes. The addition of the MEKP hardener to the polyester resin should be as accurate as possible. Scales, syringes and pipettes are considered very helpful for dosing.

When mixing, ensure that the polyester resin-MEKP hardener system is thoroughly mixed. The bottom of the mixing cup should be scraped repeatedly