HDI trimer

Heterocyclic block copolymers, 282-284 Heterocyclic diamines, rigid, 281 Heterocyclic polymers, structure-property relationships in, 273-274 Heterocyclic ring formation, PQ and PPQ synthesis by, 309-310 Hexadecyltrimethylammonium bromide (HTMAB), 549-550 Hexamethylene diisocyanate (HDI), 199, 210. See also HDI trimer Hexamethylenediamine-adipic acid salt, 169, 170... 

Figure 6.2.13 Uncatalyzed reaction of a polyester polyol with HDI trimer. -A- NCO %, Viscosity (cps)...

Table 6.2.8 Potlife of high solids polyester/HDI trimer with DBTDL as a catalyst and 2,4-pentanedione as a stabilizer ...

Aliphatic isocyanates blocked with different blocking agents. HDI trimer or IPDI. DBN = 1,5-diazobicyclo[4.3.0]non-5-ene Bi, Ca, Co, Cr, Mn, Zn, 2-ethylhexanoic acid salts... 

Aqueous two-component polyurethane systems for automotive topcoats are under development. Currently the automotive topcoats are made from solvent-based two-component or blocked one-component systems based on HDI trimer (Desmodur N) or IPDI trimer (Desmodur Z) or both in conjunction with an acrylic polyol. The polyurethane topcoats provide the vehicles with a tough and durable finish with excellent long-lasting glossy appearance ( wet look ) One-component aqueous dispersions are already used in electrodeposition primers and pigmented base coats. Soft-feel polyurethane coatings are increasingly used for instrument panels and seat covers. 

In terms of resin chemistry, the clearcoats are based on a hydroxy-functional polyester and aciylic-resin blend. The polyester is responsible for providing the high flexibility at low temperature. The hardener is based on hexamethy-lene diisocyanate (HDI) trimer. Ultraviolet absorbers (UVA), and hindered amine light stabilizers (HALS) are additives added to absorb UV light, protect the basecoat pigments and to quench free radicals that could deteriorate and decompose the backbone resins. 

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