1

Inconsistent   curing speed and pot life — bottlenecks, incomplete cure, surface tackiness.

Polyether   hydroxyl value variation, TDI NCO content fluctuation, moisture contamination.

Specify   polyether with tight hydroxyl tolerance (±1 mg KOH/g); require TDI with NCO   content ±0.1%; use nitrogen-blanketed packaging to prevent moisture; provide   precise NCO/OH ratio calculation guidance.

2

Poor   adhesion to substrates — delamination, bond failure, sealant detachment.

High   hydrolyzable chloride in TDI, low-purity polyether with oligomer impurities,   incorrect NCO/OH ratio.

Use   low-hydrolyzable-chloride TDI (<0.01%); specify high-purity polyether with   low oligomer content; recommend primer or adhesion promoter; ensure correct   stoichiometric ratio for optimal wetting.

3

Insufficient   weatherability / UV resistance — chalking, cracking, gloss loss outdoors.

High   unsaturation in polyether leading to UV degradation, lack of UV stabilizers,   aromatic TDI yellowing.

Use   low-unsaturation polyether (<0.02 meq/g) for UV stability; recommend   HALS/UV absorber additives; consider aliphatic isocyanate (HDI/IPDI) for   topcoats; use UV-stabilized TDI prepolymers.

4

High   viscosity / poor application — difficult spraying, uneven film, poor   leveling.

High-MW   polyether with broad MWD, high functionality increasing viscosity, low   solvent compatibility.

Select   lower-MW polyether (MW 1000–2000) for sprayable viscosity; use narrow-MWD   polyether for consistent viscosity; recommend reactive diluent or compatible   solvent; specify low-viscosity TDI adducts.

5

Bubbles   and pinholes — aesthetic defects, reduced barrier, premature corrosion.

Excessive   moisture in polyether/TDI, high volatile content, improper degassing.

Require   ultra-low-moisture polyether (<0.03%) and TDI; use nitrogen-blanketed   drums; recommend vacuum degassing; specify low-volatile-grade raw materials;   control application humidity.

6

Inadequate   chemical resistance — softening, degradation, swelling in industrial   environments.

Insufficient   crosslink density, low-hard-segment content, polyether type selection.

Use   higher-functionality polyether (3–4) for crosslink density; increase BDO   chain extender content for hard segments; consider polyester polyol blend for   solvent resistance; optimize NCO index (1.05–1.15).

7

VOC   and regulatory compliance — REACH, EPA, CARB, low-odor indoor air quality.

High   residual monomer in TDI prepolymer, volatile additives, low-purity raw   materials.

Use   low-free-TDI prepolymers (<0.1% free TDI); specify low-VOC polyether   grades; ensure REACH registration for all substances; provide SDS and   regulatory documentation; recommend water-borne or high-solids formulation.