Testing and qualifiying resins: The main standards - Coolmag

05 Jun.,2025

 

Testing and qualifiying resins: The main standards - Coolmag

Resins are used in a lot of formulations of Coatings, Inks, Paints, and dispersions of fillers, quartz, pigments that have functional application.

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As a definition of resin:

A thick, sticky substance that is produced by   some trees and that becomes yellow and hard after it is collected, or any of various similar substances produced by a chemical process for use in industry:

Or

any of various solid or semisolid amorphous fusible flammable natural organic substances that are usually transparent or translucent and yellowish to brown, are formed especially in plant secretions, are soluble in organic solvents (such as ether) but not in water, are electrical nonconductors, and are used chiefly in varnishes, printing inks, plastics, and sizes and in medicine.

On industry, Natural resin are still used in some applications but synthetic resins are more common where manufacturers develop specific product for each particular technical demand.

Main use is as a carrier of different pigments and fillers and should be formulated under premise that compatibility with solvent and rest of raw materials than are on formula and the end uses of the mixing.

Main function of the resin is to be cured by evaporation of solvent, by reaction of two component (resin and catalyst) by energy process of curing (UV light or LED).

The most values to test in a resin are focused in its performance and physical properties as  original form before cured process and after it when all resin has been cured at final application.

Most popular liquid resin uses in Potting system are liquid rubber cured under room temperature, typical values that you can find on TDS:

Appearance:

Liquid resin comes in forms of different appearances commonly described as clear, transparent, translucent, or in different colours, as an example showed on table detailed below:

Appearance assessment is a simple and easy way to estimate the quality of the liquid resin. A change in color indicates a change in wavelength absorption of visible light by the resin. Hence, it could be important to assess the appearance of the resin to ensure the quality of the resin as the change can indicate contamination or impurities in the raw material, process variations caused by heating and oxidation, or degradation of products exposed to weathering over time. There is no existing standard test method specifically for liquid resin. However, visual tests have been established by comparing the sample to a known standard. Objective measurements can also be done with color spectrophotometers that give reliable data on a consistent basis. ASTM and ASTM provide some information about the standard method to assess the color of any liquid materials.

Gardner Colour Scale:

The Gardner Colour scale as specified in ASTM D is a single number colour scale for grading light transmitting Scale samples with colour characteristics ranging from light yellow to brownish red. It is widely used for oils, paint and chemicals, such as resins, varnishes, lacquers, drying oils, fatty acids, lecithin, sunflower oil, linseed oil. The scale is defined by the chromaticities of glass standards numbered from 1 for the lightest to 18 for the darkest.

ASTM

The major objective of the visual platinum-cobalt (Pt-Co) method of colour measurement is to rate specific materials for yellowness. This yellowness is frequently the result of the undesirable tendency of liquid hydrocarbons to absorb blue light due to contamination in processing, storage or shipping.

Clear liquids can be rated for light absorbing yellowish or brownish contaminants, using scales that simulate the long-established visual-comparison method just cited. Where needed, dimensions of colour can be reported to identify any pinkness or greenness (one dimension), or greyness.

Viscosity:

The term Viscosity requires a separate study, detailed below the most common methods:

Brookfield Viscosity:

The operation of the Brookfield viscometer is based on the principle of rotational viscosimetry; It measures the viscosity by capturing the torque required to rotate at a constant speed a spindle immersed in the sample of fluid to be studied.

The torque is proportional to the viscous resistance on the submerged shaft, and consequently, to the viscosity of the fluid.

Brookfield viscometers are easy to install and versatile and do not require great operational knowledge.

Each viscometer is composed of the following elements:

  • Viscometer body, consisting of an electric motor and a reading dial.
  • Interchangeable Spindler: these spindlers are numbered from 1 to 7, with 1 being the thickest. They have, on their axis, a signal that indicates the level of immersion in the liquid.

The adjustment and calibration of these stems is carried out by the manufacturer himself. Other adjustments and subsequent checks may be carried out using Newtonian liquids of known viscosity.

  • Thermostatic bath, to keep the product to be tested at the test temperature.
  • Support, to allow to hold the device and move it in a vertical plane.
  • Vessels, between 90 and 92 mm in diameter and 116 to 160 mm high.

Choice of speed and stem:

The viscosity / spindler ratio will be chosen, depending on the value of the viscosity to be measured, the desired accuracy and the velocity gradient tested.

It is necessary to make the choice so that the reading on the dial is between 20 and 95% of the scale. For better accuracy, it is advisable to use the interval between 46 and 95%.

Calculations:

Brookfield RV viscosity, in cP, of the sample to be tested, is obtained according to the following expression:

Viscosity calculation

K being a coefficient that depends on the speed / rod ratio used and L the average value of the two readings given as valid.

Höppler Viscosity:

A Type C Ball Drop Höppler Viscometer measures the viscosity of transparent non-Newtonian fluids very accurately and can be used in the temperature range of -20 to 120 ° C.

The determinations with this viscometer are based on the measurement of the time it takes for a ball to travel between the two extreme marks indicated on the viscometer. A Höppler type viscometer can be seen in the attached figure.

The apparatus contains, as a fundamental element, a thick-walled glass tube that has two annular signals marked in the vicinity of its ends and which in turn is inserted into another much wider tube intended to accommodate circulating water as a thermostatic medium. The assembly is arranged in a slightly inclined position on a support similar to that of a microscope and can be rotated 180 ° around an axis perpendicular to both tubes.

The Höppler viscometer is very accurate and is frequently used in the chemical industry (polymer solutions, solvents, inks) in the pharmaceutical industry (excipients, glycerin) and in the food industry (jellies, sugar solutions), as well as among the manufacturers of mineral oils.

Calculations:

The time it takes for the ball to travel between the two extreme marks of the viscometer will be measured several times and the results will be averaged. This value is multiplied by the factor of the ball used, which can be found in the equipment manual. The result gives the viscosity, expressed in mPa.sec, which is equivalent to cPs. Is given by

El tiempo que tarda la bola en recorrer el espacio entre las dos marcas extremas del viscosímetro, se medirá varias veces y se promediarán los resultados. Este valor se multiplica por el factor de la bola utilizada, que se encontrará en el manual del equipo. El resultado da la viscosidad, expresada en mPa.seg, que equivalen a cPs. viene dado por:

Viscosity calculation

For more Elastic Polyester Resins for Consumer Electronics Coatingsinformation, please contact us. We will provide professional answers.

Viscosity (Kpa.seg) = cP = T (Db-Ds) x K

Where:

  • T indicates the fall time, in seconds,
  • Db is the density of the ball,
  • Ds is the density of the sample solution prepared
  • K is the ball constant, taken from the viscometer manual

Hardeness (Shore A):

As a definition:

Shore Hardness is a measure of the resistance a material has to indentation. There are different Shore Hardness scales for measuring the hardness of different materials (soft rubbers, rigid plastics, and supersoft gels, for example). These scales were invented so that people can discuss these materials and have a common point of reference.

DIN ISO -2:

A method for determining the indentation hardness of vulcanized or thermoplastic rubber by means of a pocket hardness meter calibrated in IRHD. The hardness of rubber, as measured by an IRHD pocket meter or a Shore durometer, is determined from the complex response of the rubber to an applied indentation. An IRHD pocket meteris a portable hand-held durometer calibrated to measure on the IRHD scale. The measurement will depend upon:

  1. The elastic modulus of the rubber
  2. The viscoelastic properties of the rubber
  3. The thickness of the test piece
  4. The geometry of the indentor
  5. The pressure exerted
  6. The rate of increase of pressure
  7. The interval after which the hardness is recorded

Because of these factors, it is inadvisable to relate results obtained using an IRHD pocket meter directly to Shore durometer hardness values, although correlations have been established for some individual rubbers and compounds.

Tensile Strength:

As a definition:

A measure of the ability of a material to withstand a longitudinal stress, expressed as the greatest stress that the material can stand without breaking

ASTM D412

Is the most common standard for determining the tensile properties of vulcanized (thermoset) rubber andthermoplastic elastomers. Compounds in this family are used to create a vast array of consumer goods such as tires, footballs, and rubber bands. This family also produces highly specialized materials, such as O-rings on space shuttles, which must perform reliably under extreme environmental conditions.

ASTM D412 measures the elasticity of a material while under tensile strain, as well as its behavior after testing when the material is no longer being stressed. ASTM D412 is conducted on a universal testing machine (also called a tensile testing machine) at a rate of 500 ± 50 mm/min until the specimen fails. Though ASTM D412 measures many different tensile properties, the following are the most common:

Tensile strength – the maximum tensile stress applied in stretching a specimen to rupture.

Tensile stress at a given elongation – the stress required to stretch the uniform cross-section of a test specimen to a given elongation.

Ultimate elongation – the elongation at which rupture occurs in the application of continued tensile stress.

Tensile set – the extension remaining after a specimen has been stretched and allowed to retract in a specified manner, expressed as a percentage of the original length.

Elongation at Break %

As a definition:

Elongation at break is the percentage increase in length that a material will achieve before breaking. A higherpercentage usually indicates a better quality material when combined with a good Tensile Strength.

Solid Rubber that exhibits a high Elongation at Break but a low Tensile Strength may be indicative of a poorly mixed or under cured polymer, which if used to produce Rubber Gaskets or Seals will see premature failure.

References

All about working with polyester resin! - Polyestershoppen.com

Polyester for beginners

What is polyester resin and what can you use it for? In this article we explain the basics of working with polyester resin. At Polyestershoppen you will find all the materials you need to start your polyester project. Our specialists are also ready to advise you and help you get started with your project. So feel free to contact us!

What is polyester resin?

Polyester is a synthetic resin that hardens after adding a hardener. This process is irreversible, so polyester cannot be melted. Polyester does not rot or rust and can be processed with a minimum of tools. With a polyester repair kit, you can easily carry out minor repairs. For example, on caravans, boats or swimming pools.

Polyester is usually combined with fibreglass, to obtain a strong, impact-resistant and rigid product. Examples of polyester products include boats, ponds, swimming pools, car bumpers, gutters, works of art, scooter covers, waterproof coverings and much more.

Benefits of polyester:

  • Polyester does not rot or rust.
  • Cheap and easy method to manufacture plastic or to do repairs.
  • Suitable for a huge number of applications.
  • Polyester is a strong and rigid system.

Combining polyester resin with glass fibre is called laminating. The resulting plastic is called a laminate, named after the different layers of fibreglass it is made up of.

Polyester is ideal for products where freedom of shape is paramount. Polyester with glass fibre is always laminated against a mould (temporary or otherwise). This temporary mould can be made of any material and can also become part of the construction. Examples of moulds are: polyester moulds, moulds made of wood, foam or plaster, stretched T-shirt fabric or chicken wire. You can make products in a mould, but also clad objects. In short, if you need something to laminate the polyester against, it can be made with polyester.

Polyester products can be finished in various ways. Against a smooth mould, gelcoat can be used, an approximately 0.3 mm thick thoroughly coloured layer based on polyester. This layer takes on the surface texture of the mould. A mirror-smooth finish is usually aimed for. For filling small holes and a tight finish, please use polyester putty. This product has a fast cure and is easy to sand.

Application Features RESION Polyester laminating resin
  • Coating with glass mat
  • Making adhesives and fillets
  • Polyester repairs
  • Impact-resistant
  • Fast curing
  • Easy to process
  • Economical
  • Stick-free curing
  • Low styrene emission
RESION Polyester casting resin
  • Casting ornaments
  • Casting organic materials (flowers, insects)
  • Casting figurines
  • Jewellery
  • Fast-curing
  • Highly transparent
  • May show shrinkage (approx. 5%)
  • Reactivity adjustable
  • UV-resistant
RESION Vinylester resin
  • Mould making
  • Non-shrink coatings
  • Chemically resistant floors, horse trailers, cattle transport, walls, etc.
  • Feed throughs
  • High temperature resistance
  • Very high chemical resistance
  • Stronger than polyester
  • Fast curing
  • Osmosis resistant
RESION Polyester topcoat
  • Finishing polyester ponds, swimming pools
  • Finishing glass fibre laminate
  • Repair of gelcoat damage
  • Fast curing
  • Easy processing
  • High layer thickness
  • Thixotropic
  • Stick-free curing
  • Good water resistance
RESION Polyester gelcoat
  • Finishing polyester ponds, swimming pools (1st layer)
  • Colour coating in moulds
  • Fast curing
  • Easy processing
  • High layer thickness
  • Thixotropic
  • Good water resistance
RESION moulding gelcoat
  • Surface layer for durable moulds
  • High temperature resistance
  • High scratch resistance
  • High gloss level
  • Low porosity
RESION moulding resin
  • Construction material for durable moulds
  • Shrink-free curing
  • Suitable for high-speed lamination
  • Stick-free curing
  • 5 mm thickness wet-on-wet lamination
RESION abrasive gelcoat 
  • Bodywork repairs to polyester parts
  • For repaintable polyester products
  • Easy to sand
  • Very good adhesion with various paint systems
  • Thixotropic
  • High layer thickness
  • Easy processing
Polyester putty
  • Fine finishing of polyester laminates
  • Repair of scratch damage
  • Filling metal parts (bodywork)
  • Filling bumpers
  • Fast curing
  • Good sandability
  • Good adhesion to various substrates
  • Not water-resistant (use Epoxy putty under water)
Polyester fibreglass putty
  • Plugging holes
  • Repairing cracks
  • Stronger than polyester putty
  • Fast curing
  • Tear resistant
  • Good adhesion to various substrates
  • Not water-resistant (use Epoxy putty under water)

On the other side of the polyester product, or if an object is coated, a polyester topcoat can be used. This layer is also a ca. 0.3 mm thick through and through coloured layer, but the surface structure depends mainly on the application technique (brush, roller or even spray) and will always be silky gloss and have some structure. It is possible to sand and/or polish this topcoat finish completely smooth.

Projects with polyester resin

There are several applications for polyester. For some applications, we have written a manual:

  • Polyester pond making.
  • Polyester repair of holes and cracks.
  • Boat mirror repair and restoration with polyester.
  • Repairing a plastic shower tray with polyester or epoxy.
  • Sealing walls and floors.
  • Covering an object with polyester.
  • Wooden hot tub waterproofing with vinylester or epoxy. 
  • Polyester mould making.
  • Making a new floor in the boat with polyester.
  • Making a boat stand.
  • Preventive anti-osmosis treatment.
TIP: have something in mind but would like some advice first? Then contact our customer service. Our staff all have experience with polyester and can advise you on your project.

Reinforcement fibres

With polyester resin, we usually use a glass mat. This is a mat made of fibres about 5 cm long that are criss-crossed. These glass fibres are held together by an adhesive that dissolves in polyester resin. By spreading polyester resin on the mat, the mat will become flexible and take the underlying shape. So once the resin cures, we have a product that gets its strength from the glass fibre and stays in its shape because of the resin.

Application Features Fibreglass chopped strand mat 225gr/m2
  • Suitable as first layer behind gelcoat
  • Suitable as first layer for over polystyrene-free polyester
  • Suitable as final layer for finer finishing of fibreglass laminate
  • Thickness approx. 0.5 mm
  • Resin consumption 500gr/m2
  • Fine texture
Fibreglass chopped strand mat 300gr/m2
  • Suitable for polyester repairs
  • Suitable for covering wood (2x 300gr/m2)
  • Thickness approx. 0.7 mm
  • Resin consumption 700gr/m2
Fibreglass chopped strand mat 450gr/m2
  • Universal use
  • For rapid build-up of layer and thickness
  • Suitable for mould making
  • Thickness approx. 1 mm
  • Resin consumption gr/m2
  • Economical
Glass fleece 30gr/m2
  • Suitable as first layer behind gelcoat
  • Suitable as first layer in mould construction
  • Suitable as final layer for fine finishing of glass fibre laminate
  • Thickness approx. 0.1 mm
  • Resin consumption 100gr/m2
  • High chemical resistance
  • Prevents print-through in gelcoat
Woven roving 300gr/m2
  • Suitable for extra-strong laminate in alternation with fibreglass mat
  • Alternate woven roving with fibreglass chopped strand mat 300gr/m2
  • Increases impact resistance
  • Thickness approx. 0.5 mm
  • Resin consumption approx. 500gr/m2
Woven roving 600gr/m2
  • Suitable for extra-strong laminate in alternation with fibreglass mat
  • Alternate woven roving with fibreglass chopped strand mat 450gr/m2
  • Increases impact resistance
  • Thickness approx. 1 mm
  • Resin consumption approx. gr/m2
Spherecore 2 mm
  • For extra rigid polyester laminates
  • For lighter polyester laminates
  • Suitable for laminating round shapes
  • Increases stiffness
  • Faster build-up of thickness
  • Thickness approx. 2 mm
  • Resin consumption approx. gr/m2
Spherecore 3 mm
  • For extra rigid polyester laminates
  • For lighter polyester laminates
  • Suitable for laminating round shapes
  • Increases stiffness
  • Faster build-up of thickness
  • Thickness approx. 3 mm
  • Resin consumption approx. gr/m2
Spherecore 4 mm
  • For extra rigid polyester laminates
  • For lighter polyester laminates
  • Suitable for laminating round shapes
  • Increases stiffness
  • Faster build-up of thickness
  • Thickness approx. 4 mm
  • Resin consumption approx. gr/m2

How do you make polyester resin?

Never prepare more polyester resin than you can process in 10 minutes. Approximately 2% hardener is added to polyester resin.

  • Don't mix too much polyester resin.
  • For small quantities (< 5 ml) of hardener, use a pipette.
  • Determine the amount of hardener according to the ambient temperature.
  • Mix resin and hardener carefully and scrape bottom and sides of the mixing cup.

How much polyester hardener do you need for polyester laminating resin?

The chart below shows how much hardener you need for polyester laminating resin.

Hardener 12-17 ℃ 18-23 ℃ 23-30 ℃ Resin: 2.5% 2% 1.5% 100 grams 2.5 ml 2 ml 1.5 ml 250 grams 6.25 ml 5 ml 3.75 ml 500 grams 12.5 ml 10 ml 7.5 ml grams 25 ml 20 ml 15 ml

How much polyester hardener do you need for polyester laminating resin?

The chart below shows how much hardener you need for polyester laminating resin.

MEKP Potlife Full cure Thickness 1 cm 1% 25 min. 10 hours 1.5% 22 min. 3 hours 2% 20 min. 2.5 hours Thickness 3 cm 0.4% 40 min. 2 hours 0.7% 27 min. 1.5 hours 1% 25 min. 45 min. Thickness 6 cm 0.3% 48 min. 45 min. 0.35% 43 min. 30 min. 0.4% 40 min. 30 min.

Laminating

Lamination is the technique/process of manufacturing a material in multiple layers (so that the composite material achieves improved strength) using a reinforcing material such as glass mat and polyester laminating resin. The reinforcing material is "wetted" with the polyester resin by using a brush or roller.    

Commonly used auxiliary materials when laminating:

  • Disposable flat brushes
  • Fleece rollers
  • Mixing cups
  • Paddle roller
  • Mixing spatulas
TIP: we also have complete packages with all the auxiliary materials you use a lot when laminating.

Finishing polyester with polyester topcoat

After laminating, the laminate may be a bit rough. To finish the laminate and increase its weather resistance, you can coat it with a polyester topcoat. Lightly sand the laminate with 60-grit sandpaper to prepare it for the topcoat.

In the video above, Kees shows how to finish polyester with polyester topcoat. After curing, your product is protected from the weather and has the colour you want.

Polyester repair kit

Buy your polyester repair kit at Polyestershoppen.com. Our set is fully equipped with all the tools needed to carry out various repairs. Everything in one set! Easily repair holes, cracks and fractures in polyester items. Besides a small repair kit, we also have a polyester repair kit for the somewhat larger projects. Here, for example, we have laminating kit.

Personal protection

Styrene fumes from polyester is harmful to health and the environment. Ventilate the area you will be working in well and preferably wear a half mask, especially in a small space. Also make sure to avoid skin contact with polyester resin and hardener by wearing suitable gloves, such as latex gloves, nitrile gloves or household gloves.  

Other commonly used protective materials:

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  • Safety glasses
  • Vapour mask with A2 vapour filters
  • Full face mask (for full face protection) with A2 vapour filters
TIP: Polyestershoppen has a complete package with all the protective materials you need while working with polyester.

Do you have any questions about polyester processing?