Hydroxypropyl Starch Ether (HPS): field notes from job sites and labs

If you’re sizing up hydroxy starch for modern dry-mix mortars, here’s the short version: HPS is the quiet additive that makes trowels glide, tiles stay put, and mixes age gracefully. It’s a fine white powder—plant-based, highly etherified, spray-dried, no plasticizers—and yes, very different from ordinary starch. I’ve watched buying teams shift to HPS because it stabilizes recipes without blowing up cost. Trends? Greener binders, leaner cement, higher filler loads; HPS slots right in.

Where HPS shines (and why teams keep it)

• Tile adhesives (EN 12004), gypsum and cement plasters, self-leveling underlayments, EIFS basecoats, block adhesives.
• Benefits reported by applicators: longer open time, smoother spread, anti-sag on walls, fewer re-temperings. Many customers say it “feels creamier” at the same water.
• Low dosage (≈0.05–0.3%) with big impact on water retention and workability; real-world use may vary by filler and temperature.

Technical specs at a glance

Origin: Room 2308, Dongsheng Plaza 2, No. 508 Zhongshan East Road, Chang’an District, Shijiazhuang, Hebei, China.

Process and QC (short version)

Natural starch → alkaline activation → etherification with propylene oxide (controlled DS/MS) → neutralization → washing → spray drying → milling → packaging. QC covers DS, moisture, pH, viscosity profile, and sieve residue. Facilities I’ve visited run ISO 9001, with batch retention samples and COAs. Shelf life ≈ 24 months sealed, cool/dry.

Application data and standards

• Tile adhesive (C1T baseline): with 0.15% hydroxy starch, EN 1348 tensile adhesion: 1.1–1.4 MPa dry; open time ≥ 0.5 MPa at 30 min; slip ≤ 0.5 mm. Lab data; your fillers and cement will nudge numbers.
• Gypsum plaster: EN 1015-3 flow kept 180–190 mm at 20°C; water retention ≥ 95% (filter test).
• Self-leveler: maintains viscosity window while reducing segregation; ASTM C1708 rheology indexes within spec.
• Service life of finished systems depends on formulation; EIFS adhesives typically validated 10–25 years under ETAG/ETICS regimes—conditions matter.

Vendor snapshot (what buyers compare)

Customization tips

Ask for viscosity curves at your shear rate, water-retention at 0.1–0.2% dosage, and compatibility with your HPMC/EVA. Also, request side-by-side EN 1348 and EN 1015 data—saves weeks later. For hot climates, a slightly higher MS can stabilize pot life.

Two quick cases

• Southern tile plant: swapped 0.05% cellulose-only to 0.05% cellulose + 0.15% hydroxy starch. Open time +10–15 minutes; installers reported “less slump on verticals.” Adhesion stayed >1.0 MPa (EN 1348, dry).
• Gypsum skim coat: introduced 0.12% hydroxy starch. Edge tearing disappeared; sanding became more uniform; water demand dropped ≈3% at same flow.

Final note: specs are one thing; how it “feels” under a steel trowel is another. Do the lab, then do the wall.

References

1. EN 12004-2:2017 Adhesives for tiles — Test methods for cementitious adhesives.
2. EN 1015 series: Methods of test for mortar for masonry (flow, water retention, strength).
3. ASTM C109/C109M: Compressive strength of hydraulic cement mortars; ASTM C1708: Rheology of hydraulic cement-based materials.
4. ISO 9001:2015 Quality management systems — Requirements.