Carbodiimides. Alternatives to isocyanates as crosslinkers.

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Carbodiimides. Alternatives to isocyanates as crosslinkers.

Monday, 15 January, 2024

Polycarbodiimides are water-borne resins that contain carbodiimide groups with hydrophilic segments, as shown in the diagram:

They are crosslinkers that do not add VOCs to formulations and are environmentally less polluting than diisocyanates. They are used to crosslink two-component water-borne paints containing carboxylic functional groups (polyurethane dispersions, acrylics, water-dispersible polyesters, etc.).

Comindex distributes these products thanks to its partnership with its represented company Nisshinbo, which manufactures these carbodiimides under the brand:

Features:

  • Environmentally friendly, less toxic than diisocyanates and do not require labelling.
  • A long pot-life: they are slow-reacting, but their reaction speed vs. stability can be adjusted: decreasing the pH accelerates the speed. If more stability is needed, the pH is increased. It can be formulated as a single component and remains stable for weeks and several months.
  • Reacts at room temperature, but the drying temperature can be increased to accelerate curing.
  • Maintains flexibility, boosting chemical resistance.
  • Easy to disperse.
  • Improves the final paint’s adhesion owing to the interaction between polar groups on the material’s surface and the carbodiimide groups.
  • Benefits from good anti-hydrolysis properties.
  • The dosages for crosslinking are lower than those for diisocyanates.
  • It is the safest crosslinker in applications for food contact. Certain grades comply with FDA and Swiss Ordinance regulations.


 


Applications in which carbodiimides may be used:

  • Wood coatings/varnishes (parquet/wooden floors), countertops, indoor and outdoor furniture, etc.
  • Coatings for concrete floors, micro-cement, with resistance to tire marks.
  • Industrial coatings on metal and fibreglass.
  • Inks (involving food contact).
  • Paints/varnishes, DIY application both indoors and outdoors.
  • Leather tanning industry.
  • Coatings on plastics.
  • Thermoplastics, enhancing the anti-hydrolysis properties of polymers such as: PLA, PBS, PET/recycled PET, PBT, elastomeric polyester, PA, starch-based resin, etc. Applications: plastic bags, appliance covers, food containers, agricultural film, interior parts of cars, cable coating, toys and stationery.

Other types of crosslinkers are available on the market for these types of formulations, such as aziridines, blocked isocyanates, melamines, oxazolines, etc., but carbodiimides specifically are far more effective to use on balance when considering all aspects such as their toxicity, reactivity, pot-life and reaction temperature.

The Carbodilite products from Nisshinbo that we market constitute a safe, environmentally-friendly solution both in high-performance water-borne coating applications and in plastics.

For further information about these products, please contact our Team of Technical Sales Advisors.

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