Polyaspartic Polyurea Encyclopedia: Chemistry, Performance, Applications and Installation

7. Technical parameters: what the numbers actually mean

1. Amine value and amine equivalent weight are different

Amine value is commonly expressed as milligrams of potassium hydroxide equivalent per gram of sample and characterizes basicity or amine-related properties under a specified method. Amine equivalent weight expresses the mass of material corresponding to a relevant reactive equivalent and is important for formulation calculations. Interpretation depends on the test method, composition and supply form.

Certain conversions can be established for ideal materials with known structures. Commercial raw materials, however, may contain different amines, diluents or other ingredients. Amine value should not be casually converted into a finished product’s site mixing ratio. Formulators should use the appropriate reactive equivalents; applicators should follow the finished product’s specified ratio.

2. NCO content is not free isocyanate monomer content

NCO content is the mass proportion of isocyanate groups and relates to reactive capacity. Free monomer content measures unbound monomer and is a different composition parameter. Covestro’s published Desmodur N 3600 information lists NCO content and monomeric HDI separately, illustrating the distinction. Desmodur N 3600 product information

Low free monomer does not mean almost no reactive groups, and higher NCO content does not directly imply high free monomer. Interpret both alongside the safety data sheet and intended application.

3. Equivalent ratio differs from packaged weight ratio

An equivalent ratio compares the reactive groups taking part in the reaction; a weight ratio compares the masses of the two formulated components. Pigments, fillers, additives and possible diluents mean that identical reactive equivalent ratios need not correspond to identical packaged mixing ratios.

In a simplified system containing one ideal amine component and one NCO component, dividing each mass by its equivalent weight gives the reactive equivalents for calculating the NCO/NH ratio. Other reactive ingredients in real formulations must also be included. This explains formulation calculations; it is not a basis for modifying mixing ratios on site.

4. Viscosity requires measurement conditions

Viscosity describes resistance to flow, but temperature, instrument, spindle and shear conditions can affect the result. Raw resin, an unmixed component and the mixed coating are also different states. Ranking values measured under different conditions provides limited useful information.

For fast-reacting materials, elapsed time after mixing is particularly important. A material that rolls easily at first but thickens noticeably after several minutes requires different site organization from one that remains workable longer. Technical information should identify timing and measurement conditions wherever possible.

5. Check the basis of solids content and density

Solids by weight, solids by volume and density are different inputs in consumption calculations. Confirm whether figures apply to a single component or to the correctly proportioned mixture. Substituting component A’s density for mixed-product density can distort coverage estimates.

Solids testing also involves specified heating, duration or other method conditions. Compare like-for-like data. Project planning ultimately needs to connect the required dry-film thickness with wet-film thickness, consumption and actual film formation, rather than rely on a percentage alone.

6. Pot life, gel time and open time have distinct meanings

Pot life is the period during which the mixed material remains suitable for its specified application. Gel time concerns a defined loss of flow. “Open time” can have different meanings in different documents, so check the definition instead of treating similar terms as interchangeable.

Application quality can deteriorate before the material gels. If only gel time is supplied, confirm the practical spreading and edge-blending window. Fast-track projects must separately plan pot life, pedestrian access, vehicle traffic and full cure.

7. Identify the hardness and strength test

Pencil hardness, Shore hardness and other methods assess different things and cannot be directly converted into a universal ranking. Tensile strength depends on specimen geometry, thickness, test conditions and conditioning; elongation should likewise be compared under consistent conditions.

Free-film tensile results and crack-bridging assessments on a substrate provide different evidence. Repeated movement in waterproofing requires relevant movement evaluation, rather than an assumption that high elongation permits bridging every joint.

8. Read data in the order: object, method, conditions, result

First establish the product and layer tested, then the method, specimen preparation and curing, and finally the result. A high number is difficult to turn into a site decision when its subject or conditions are unclear.