C528 (RC)

Trade Name:RC
Chemical Composition:Contain 26% aromatic polyisocyanate and 74% ethyl acetate

The almost colorless Hartdur C528, similar to Desmodur RC, is designed as a curing agent for adhesive based on hydroxyl polyurethane (PU), natural rubbers and synthetic rubbers. Owing to Hartdur C528 features good photo-resistance, it’s particularly suitable for light-colored polyurethane adhesive system. Because the solvent is ethyl acetate, Hartdur C528 can be used in those countries where the use of methylene chloride is restricted.

Hartdur C528 is a crosslinker of a polyisocyanurate of toluene diisocyanate (TDI) in ethyl acetate, and has excellent initial strength and outstanding heat resistance. Hartdur C528 improves the adhesion to difficult-to-stick objects, such as plasticizer PVC, oily SBR, top leather, silk and etc. It especially suit for pale-colored adhesives to bond rubber materials. Mostly applied in  footwear industry.

Compatibility with Solvents

Hartdur C528 can be diluted with anhydrous and alcohol-free ethyl acetate, dichloropropane trichloroethylene acetone, methyl ethyl ketone toluene and other similar solvents. The addition of relatively large proportions of aliphatic hydrocarbons can cause turbidity; but it can be re-dissolved by using larger proportions of the solvents mentioned above.


  1. 0.80 KG/ Aluminum bottle; 20 bottles/carton (16kgs/carton).
  2. 180 KG / Iron Drum.

It can be packaged on demand. Please inquire.     

Hartdur C528 is a two-component adhesive. After adding a certain proportion of Hartdur C528 to the adhesive, the ready-to-use double-component adhesive should be applied within a period (pot life) which is determined not only by its content of rubber, but also by the other ingredients of the formulation (e.g. resins, antioxidants, solvents, and etc.). If the adhesive is not used within this period of time, it may become increasingly difficult to apply and its viscosity increases rapidly until irreversible gel time ultimately occurs. Thus, it’s no longer to be used.


For curing adhesive of 100 parts by weight (p.b.w.) based on:

Graft-Chloroprene rubber

(rubber content approx. 16%)

3-5% p.b.w. Hartdur C528

Chloroprene rubber

(rubber content approx. 20%)

5-7% p.b.w. Hartdur C528

Hydroxyl polyurethane

(polyurethane content approx. 15%)

3-5% p.b.w. Hartdur C528





Chemical compositionContains 26% aromatic polyisocyanate and 74% ethyl acetate;Polyisocyanate of TDI
Intrinsic colorAlmost colorless to very light color liquid
NCO%6.0 ± 0.2 %
SolubilitySoluble in various esters, ketones and aromatic solvents
Storage stabilityReacts readily with moisture; for best performance it should be kept dry and stored at temperatures between 5℃ and 32℃.
Package0.8 kg / Aluminum bottle
 180 kg /Iron Drum


Being TDI trimer, Hartdur C528 has high reactivity. It is generally used as a curing agent for fast-drying two-component polyurethane coatings, applied on  furniture paint, industrial online coating, etc. In addition, Hartdur C528 can also be used as a curing agent for room-temperature curing two-component polyurethane adhesives components. Enable the paint film outstanding quick-drying and filling properties, high hardness and good heat resistance. The disadvantage is that it’ll be yellowing after 6 months.