Aliphatic polyisocyanate of low volatility. Desmodur® DN is a solvent-free liquid polyisocyanate that is emulsifiable in water. Any occasional turbidity or precipitation visible is caused by very small amounts of processing aids These have no adverse effect on the processing and final properties of the cured adhesives. It can be used as the crosslinker for largely pH-neutral aqueous polymer dispersions including polyurethane, polyvinyl acetate, polyacrylate and synthetic rubber dispersions. Crosslinking increases the resistance of the bonds to heat, water, plasticisers and many solvents. Compared with Desmodur® DA, Desmodur® DN is characterised by its much lower viscosity and is not prone to turbidity at low storage temperatures. Properties / Applications: To ensure the optimum distribution of Desmodur® DN, the adhesive dispersion must be stirred well by mechanical means. Manual stirring is not sufficient to ensure good homogenisation, especially in the case of low-viscosity adhesive dispersions. Inadequate dispersion may result in the formation of granular deposits in the adhesive. After addition of Desmodur® DN, the ready-to-use two-component adhesive must be used within the pot life. This is governed not only by the polymer content but also by the other constituents (resin, thickener, plasticiser, etc.). The end of the pot life – usually several hours – is not always marked by gelling. It can be established by determining the resistance properties of the bonds, above all the resistance to heat and water. An addition of 3 - 10 % by wt. Desmodur® DN is recommended to crosslink 100 pbw of an adhesive dispersion with a polymer content of 40 - 60 % by wt. Desmodur® DN is generally processed without further additives. Should Desmodur® DN nonetheless be modified with an additive this may contain no groups which react with isocyanate and no secondary components which may do so. In particular, any additives used must be free of secondary components which are alkaline or have a catalytic effect on isocyanate groups. Even at a very low concentration these can cause an increase in viscosity or even solidification. Information provided by Covestro |