Browse these topics to find out more about polymers, how to use them and some of the terminology in our instructions.



hr02 What is the Shelf Life?

On all Unique Polymer Systems products there is a label on the container, which lists the "BATCH NUMBER" of the product and its "DATE OF MANUFACTURER"

Two pack products do not "CROSS-LINK" until they are mixed, and so the shelf life is normally quoted as being indefinite in UNOPENED containers, provided these are stored at reasonable temperatures. WATER BASED products should always be stored above FREEZING TEMPERATURE, otherwise they may become unusable.

Some products (commonly 1 pack), cross link slowly in the can. For these products a MINIMUM STORAGE PERIOD is quoted. In most cases, if the quoted storage time has elapsed the product will still be usable, but the viscosity may be higher.

After taking the lid off, STIR the Material BEFORE USE, to ensure that any SETTLEMENT is thoroughly re-dispersed.

If you are unsure if the product is still usable, contact the supplier to ask for advice, or simply apply a small trial area and evaluate the properties of application and the dry film.


What is Viscosity?

Viscosity is a measure of the resistance of a fluid to deformation under shear stress. It is commonly perceived as "thickness", or resistance to pouring. Viscosity describes a fluid's internal resistance to flow and may be thought of as a measure of fluid friction. Thus, water is "thin", having a low viscosity, while vegetable oil is "thick" having a high viscosity.

What are Volume Solids?

(Dry Film Thickness - dft) - (Wet Film Thickness - wft)

Volume Solids is a value that allows you to calculate the DRY FILM THICKNESS (dft) that will result from the Applied Wet Film Thickness (wft).

Thinners that are in the product "AS SUPPLIED" and those that have been added at "POINT OF APPLICATION" will EVAPORATE leaving behind the SOLID film.

i.e. - If the product to be supplied has a Volume Solids of 60%, then for every 100 microns of Wet Film Thickness applied, only 60 microns of Dry Film Thickness will be achieved when the coating is cured.

i.e. - If the Specification for that material demands that the coating be applied to a dft of 120 microns, then 200 microns of wft should be applied, (or 2 coats with wft of 100 microns)

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What is a Micron?

There are 1000 microns in 1 Millimetre (Metric System)

1 Mills (USA IMP) = 1000 / 1 inch

What are Theoretical Coverage Rates?

This value allows you to calculate how much product will be required to coat a given AREA at a given dft (Dry Film Thickness)

The Theoretical Value is Purely a mathematical calculation, which uses the Volume Solids and the Required Dry Film Thickness to work out how much area can be coated by a given Volume of WET Product AS SUPPLIED.

Square Meters per Litre Covered (m²/l) =
% Volume Solids X 10
Dry Film Thickness (microns)

i.e. If a product has a volume solids of 100% it will suffer NO SHRINKAGE, and at a dft of 1mm (1000 microns) it will cover 1 m²/litre

i.e. If the same product were applied at 100 microns - then it would cover 10 m²/litre

It should be remembered that the THEORETICAL COVERAGE RATE quoted on a product data sheet / price list - is a calculated value, assuming the substrate to be completely SMOOTH and NON-POROUS.

In reality the WORKING COVERAGE RATE will always be lower than the theoretical value, as it is influenced by many factors such as:

      • Surface Roughness
      • Surface Temperature
      • Operator / Applicator Skill
      • Substrate Porosity
      • Dimensions of Surface
      • Environmental Conditions
      • Method of Application

All of these factors reduce the apparent surface area that may be coated by a given volume of product. The only accurate way of determining the PRACTICAL COVERAGE RATE is to apply a TRIAL AREA.

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What is the Recommended Film Thickness?

These values are the normally achieved Film Builds for a single coat application.

Both Wet Film Thickness (wft) and Dry Film Thickness (dft) are quoted, assuming that the Volume Solids is "As Supplied". If Thinners are added at the point of application then the Volume Solids will be reduced, and so the Dry Film Thickness will be reduced for a given Applied Wet Film.

For most products, the coating can be applied at a wide range of Wet Film Builds.

HOWEVER - if too little is applied, the resultant dry film will not provide the Protection expected of the coating. If too mush is applied in a single coat, then the coating may SAG or suffer SOLVENT BOIL, and the practical coverage rate will be reduced.

It is therefore advisable to check the Wet Film Thickness periodically throughout the application using a "Wet Film Comb".

What is the Usable Life?

Usable Life or Pot Life is for 2 Pack Products only. It is the maximum time a product can be used after it has STARTED to be mixed. Usable Life is normally quoted at temperatures 20oC (68oF)

It should be remembered that, as the quantity of material to be mixed increases, so too will the time required to mix the two components satisfactorily. This will reduce the amount of time left to apply the product before the Usable Life expires.

Any mixed material that remains UNUSED after this period should be discarded.

In order to reduce such wastage, quite often Part Mixing of the 2 Pack materials is possible. The operator may mix a smaller amount of material, which they are confident can be applied before the Usable Life has expired.

The main factor that influences Usable Life is Temperature. As the TEMPERATURE of the material INCREASES, the USABLE LIFE DECREASES.

i.e. Of at 20o'C a product may have a USABLE LIFE of 30 minutes. BUT at 30oC the USABLE LIFE will only be about 15 minutes.

Some products (typically solvent free materials) have EXOTHERMIC reactions once the two components have been mixed. A LOT of heat can be generated by these chemical reactions. This generated heat increases the temperature of the mix, which in turn ACCELERATES the Cross-Linking and so REDUCES the Usable Life.

For materials which react EXOTHERMICALLY, if it is possible to spread the material out in a tray or on a mixing board, then this generated heat will be lost to the environment more rapidly, and so the Usable Life will be extended.

Prior to any application it is always advisable to store the materials under reasonable conditions, so that the materials temperature when first mixed is approximately 20oC

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What are Drying / Curing Times?

These values give information that is useful to the operator. They are quoted assuming a Curing Temperature of 20oC

TOUCH DRY - The period normally expected for the coating to become hard enough to be touched with LIGHT PRESSURE BRIEFLY and not mark permanently.

HARD DRY - The period normally expected for the coating to become hard enough to be touched with HEAVY PRESSURE BRIEFLY and not mark permanently.

FULL CURE - The period normally expected when ALMOST ALL of the cross-linking has been completed.

MINIMUM and MAXIMUM OVERCOATING - If the coating is too FRESH there may be an adverse reaction if another product is applied over it too soon. As the coating cures it reaches a point where it will accept further applications on top of it. This is the MINIMUM OVERCOATING time.

HOWEVER, the coating continues to cure, becoming harder. For most coatings a state of cure is reached where the coating has become so hard that further applications over the top of it will be unsuccessful. This is the MAXIMUM OVERCOATING time.

These Minimum and Maximum values present an OVERCOATING WINDOW to the operator.

i.e. Minimum Overcoating = 6 Hours
Maximum Overcoating = 24 Hours

Therefore any subsequent coatings should be applied within this window.

Many factors influence these Curing or Drying Rates:

      • Temperature of Substrate
      • Temperature of Product
      • Air Movement
      • Radiation
      • Temperature of Environment
      • Application Method
      • Applied Wet Film Thickness
      • Humidity

The MAIN FACTOR is TEMPERATURE. The HIGHER the temperature, the more RAPID the REACTION, and so the SHORTER the DRYING PERIOD.

Having shorter curing times is generally considered beneficial, and so occasionally the coating is heated after application. However, this heating process will also reduce the Overcoating Window.

If use of heating after application is being considered, then enough time should be first be allowed for any solvents to evaporate from the coating to prevent "Solvent Boil". This period between application and use of heat is called the FLASH OFF PERIOD.

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What are the Environmental Conditions?

The product may not be tolerant to certain conditions. These conditions impart restrictions on the application of the product. Any such limitations are listed on the Product Data Sheet.

Common restrictions that prohibit the application of the material are:

      • Relative Humidity is above a certain level
      • Air Temperature is below a certain level
      • Temperature of surface is less than 3oC above the DEW POINT
      • Substrate moisture content is above a certain level

RELATIVE HUMIDITY: This is a measure of the amount of moisture in the atmosphere. Measured using a Whirling Hygrometer.

DEW POINT: This is the temperature at which water will condense on the surface. It is dependant upon the Relative Humidity and Temperature of the Air. It is dependant upon the Relative Humidity and the Temperature of the air. Found by using a Slide Scale that relates Relative Humidity and Air Temperature.

i.e. If the Dew Point is found to be 15oC and the temperature of the surface to be coated is found to be 14oC then a layer of water droplets will have condensed on the surface.

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Tell me about Solvent Based Products

Many coatings are termed SOLVENT BASED, as they use HYDROCARBON SOLVENTS as the thinners. There are many different types available. The choice of depends largely on the type of resin, as one type of solvent will not be compatible with all resin types.

i.e. Xylene, Mineral Spirit, Acetone etc

Typically a blend of solvents is used, to promote specific coating and application properties.


      • Fire Hazard
      • Solvent Vapours (Health of personnel, environmental concerns)
      • Health and Safety (Dermatitis etc)

Because of these concerns, these hydrocarbon solvents must be declared. This declaration is know as "VOLATILE ORGANIC CONTENT" (VOC). The VOC level is declared for all solvent based products on the Health and Safety Data Sheet, which is always supplied with the product.

These concerns have also encouraged the development of "WATER BASED" and "SOLVENT FREE" coatings.

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Tell me about Water Based Products

Many resins are now available that can be thinned with WATER.

Some water based products may have a small amount of some special hydrocarbons solvents when supplied to the customer. Consequently it is possible to have a WATER BASED product that has a VOC level declared. However these VOC levels are much lower than for SOLVENT BASED products. Even if the WATER BASED product has a VOC, the product will NOT present a FIRE HAZARD, and the product is always thinned at the application stage with WATER.

Many of Unique Polymer Systems water based products have absolutely no VOC LEVEL ( ZERO VOC )


      • NO Fire Hazard
      • Limited or NO SOLVENT VAPOUR
      • Health and Concerns are Reduced or Eliminated
      • Thinners are FREE from the tap, but water must be cleaned


Tell me about Solvent Free Products

Some resins are fluid enough to allow the product to be applied without the need for adding thinners.

The coating manufacturer incorporates no solvent, and none are needed at the "point of application". These products are termed SOLVENT FREE COATINGS.

Hydrocarbon Solvents are required ONLY to CLEAN the application equipment after use.

Because there is no solvent in the product at the POINT OF APPLICATION, there is nothing to evaporate from the coating as it cures. Therefore there is NO SHRINKAGE of the film coat.

i.e. If you apply the coating at a WET FILM THICKNESS (wft) of 100 microns to the substrate, once cured the DRY FILM THICKNESS (dft) will also be 100 microns.

The Volume Solids of a Solvent Free Product is 100%

i.e. The resultant DRY FILM THICKNESS (dft) is 100% of the value of the WET FILM THICKNESS (wft)


      • NO Fire Hazard
      • Health and Concerns are Reduced or Eliminated
      • No SHRINKAGE of allied film


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Tell me about the Mixing Ratio

The Mixing Ratio applies to 2 Pack Products only.

For liquid applied materials the MIXING RATIO is normally expressed as a volume.

e.g. TR240 has a mixing ratio of 3 part base : 1 part activator by volume (3:1 v/v)

The products are supplied so that the BASE and ACTIVATOR COMPONENTS are to the correct MIXING RATIO if the whole unit is MIXED.

PART MIXING is a simple process, but care is needed to ensure that these smaller quantities are mixed to the same ratio as that quoted on the product data sheet.

For LIQUID APPLIED Coatings the Mixing Ratio is often CRITICAL. It is therefore very important to PART MIX as accurately as possible. Graduated Mixing sticks or Graduated Beakers or Jugs may be used for this purpose.

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Tell me about Coating Faults

The following terminologies have been extracted from BS2015 – Glossary of Paint Terms

The description applied to a paint or varnish containing bits of skin, gel, flocculated material or foreign particles, which project above the surface when the paint or varnish is applied in a manner appropriate to its type and purpose.
The term PEPPERY is sometimes used when bits are small and uniformly distributed.
The term SEEDY specifically denotes bits which have developed in a paint or varnish during storage.

The process of diffusion of a soluble substance from, into, and through a paint or varnish coating from beneath, thus producing an undesirable staining or discoloration. Examples of soluble materials that may give rise to this defect are, certain types of the following classes of materials: bituminous paints, wood preservatives, pigment dyestuffs
and stains.

The formation of dome – shaped or blisters in paints or varnish films by local loss of adhesion and lifting of the film from the underlying surface. Such blisters may contain liquid, vapor, gas or crystals.

A deposit like the bloom on a grape which sometimes forms on a glossy enamel, paint or varnish films, causing loss of gloss and dulling of color. Sometimes bloom may be removed by wiping with a damp cloth.

The formation of a friable, powdery coating on the surface of a paint film caused by disintegration of the binding medium due to disruptive factors during weathering (ultraviolet light and / or moisture). The chalking of a paint film can be considerable affected by the choice and concentration of the pigment.

A defect in which a wet paint or varnish film recedes from small areas of the surface leaving either no coating or an attenuated one.

e.g. crazing, crocodiling, mud-cracking
Generally, the splitting of a dry paint or varnish film, usually as a result of ageing. The following terms are used to denote the nature and extent of this defect.

  • Hair cracking: Fine cracks which do not penetrate the top coat. They occur erratically and at random.
  • Checking: Fine cracks which do not penetrate the top coat are distributed over the surface giving the semblance of a small pattern.
  • Cracking: Specifically, a breakdown in which the cracks penetrate at least one coat and which may be expected to result ultimately in complete failure.
  • Crazing: Resembles checking but the cracks are deeper and broader.
  • Crocodiling or alligatoring: A drastic type of crazing producing a pattern resembling the hide of a crocodile.

The formation of a small bowl shaped depressions in a paint or varnish film.

A downward movement of paint film between the times of application and setting, resulting in an uneven coating having a thick lower edge. The resulting sag is usually restricted to a local area of a vertical surface and may have the characteristic appearance of a draped curtain, hence the synonymous term curtaining.

Not a paint defect. It is the development of a crystalline deposit on the surface of a brick, cement etc., due to water containing soluble salts, coming to the surface, and evaporating so that the salts are deposited. In some cases the deposit may be formed on the top of any paint film present, but usually the paint film is pushed up and broken by the efflorescence under the coat.

Lifting of the paint from the underlying surface in the form of flakes or scales.

The development of loosely coherent solid aggregates in pigment-vehicle dispersion.

The showing through of the underlying surface, due to the inadequate opacity of a paint film that has been applied to it.

Skipped or missed areas, left uncoated with paint.

Failure caused by the swelling of a dry film of paint or varnish when another coat is applied over it and usually manifested by a wrinkled appearance.

The pock-marked appearance, in particular of a sprayed film, resembling the skin of an orange due to the failure of the film to flow out to a level surface.

The formation of minute holes in a film during application and drying. Sometimes due to air or gas bubbles in a wet film which burst, forming small craters that fail to flow out before the film has set.

A finish in which the brush marks have not flowed out, this being the normal appearance of a paint or varnish having poor leveling properties. A similar appearance may also be produced in paint, which normally has good leveling properties, by continuing to brush the paint after the film has begin to set.

In general, the formation of a soap by the reaction between a fatty acid ester and an alkali. In painting practice, saponification refers to the decomposition of the medium of a paint or varnish film by alkali and moisture in a substrate, e.g. new concrete or rendering based on cement, sand and lime. Saponified paint or varnish films may become sticky and discolored. In very severe cases the film may be completely liquefied by saponification.

The development of wrinkles in a film during drying, usually due to the initial formation of a surface skin.


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Ratio and Thickness

To estimate the coverage of polymers

An AVERAGE calculation that can be used for guidance is - 1 kilo / litre of product will cover 1m² @ 1mm thickness

To work out the mixing ratio - divide the SMALL unit into the LARGE unit.

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