Hydroxyethyl Cellulose (HEC) is the optimal thickener for construction coatings operating across pH 2–12 because it is the only non-ionic cellulose ether that maintains stable viscosity in both highly acidic and alkaline environments. Cement-based systems sit at pH 12–13, acidic corrosion-resistant primers push toward pH 2–4, and wet mortar substrates continuously leach alkaline ions into applied coatings. Most cellulose ethers fail under these conditions: anionic CMC precipitates in acid and loses viscosity above pH 9; HPMC carries methoxyl substituents that undergo alkaline hydrolysis at pH >11, causing irreversible viscosity collapse. HEC’s non-ionic hydroxyethyl substituents have zero charge-dependent interactions with ions, so its thickening mechanism — chain entanglement and hydrogen bonding — remains intact regardless of pH. A single thickener can serve across alkaline cementitious coatings, neutral latex paints, and acidic primers. Michem HEC grades (HE30KB through HE150KB) cover 1,500 to 8,500 mPa·s, with built-in enzyme resistance ensuring long-term stability. For construction coating formulators facing pH variability, HEC is the only cellulose ether that delivers consistent performance without grade-switching.
Construction coatings face pH extremes that most formulators underestimate. Fresh cement paste registers pH 12.5–13, persisting for weeks. When a water-based coating is applied over fresh concrete, the substrate leaches alkaline ions into the coating film. A thickener that loses viscosity at pH >10 causes thinning, sagging, and pigment settling — visible defects that trigger complaints and returns.
On the acidic side, corrosion-resistant primers and acid-etch coatings operate at pH 3–5. Anionic thickeners like CMC precipitate in these conditions, producing gel lumps or complete viscosity loss.
The practical consequence: pH-sensitive thickeners force formulators to maintain separate grades for acidic, neutral, and alkaline product lines — multiplying procurement and QC complexity. HEC’s pH 2–12 stability eliminates this problem, covering the entire construction coating spectrum with one thickener family.
HEC is produced by reacting alkali-cellulose with ethylene oxide, substituting hydroxyl groups on the cellulose backbone with hydroxyethyl groups (-CH₂CH₂OH). These substituents carry no ionic charge — they are neutral, polar ether-alcohol chains. Viscosity generation depends solely on physical mechanisms (chain entanglement, hydrogen bonding, and hydrodynamic volume), not on electrostatic interactions that are inherently pH-dependent. When pH changes, ionic concentrations shift, but because HEC carries no charge, its hydration state, chain extension, and intermolecular interactions remain unaffected.
CMC (carbossimetilcellulosa) is anionic. Its carboxymethyl groups (-CH₂COO⁻) dissociate in water, creating electrostatic repulsion that extends chains — this is the primary thickening mechanism. At low pH (<5), protonation collapses chains and causes precipitation. At high pH (>9), excess OH⁻ compresses the double layer, reducing viscosity. CMC’s effective window is pH 5–9 — far too narrow for construction coatings.
HPMC (Idrossipropilmetilcellulosa) carries methoxyl substituents (-OCH₃). Above pH 11, hydroxide ions attack these groups (alkaline hydrolysis), progressively cleaving ether bonds and stripping substituents — an irreversible chemical degradation. In cementitious environments (pH 12–13), HPMC viscosity loss is measurable within hours and severe within days. It performs well at pH 7–10 but cannot survive sustained high alkalinity.
HEC avoids both failure modes: no ionic groups to protonate/deprotonate (no CMC-like acid failure), no methoxyl groups to hydrolyze (no HPMC-like alkaline degradation). Its hydroxyethyl substituents are chemically stable across pH 2–12.
In viscosity retention testing, Michem HEC demonstrates the following stability profile:
| pH Condition | HEC Viscosity Retention | CMC Viscosity Retention | HPMC Viscosity Retention |
|---|---|---|---|
| pH 3 (acidic primer) | >95% after 30 days | <40% — precipitation | >90% |
| pH 7 (neutral latex) | >98% after 30 days | >90% | >95% |
| pH 10 (mild alkaline) | >95% after 30 days | ~70% — chain compression | >85% |
| pH 12 (cement environment) | >90% after 30 days | <50% — chain collapse | <30% — alkaline hydrolysis |
These data confirm that HEC is the only cellulose ether that maintains >90% viscosity retention across the full pH range relevant to construction coatings.
Microbial contamination in stored coatings produces cellulase enzymes that degrade cellulose ethers, causing “viscosity drift.” Michem HEC incorporates enzyme-resistant modification that significantly reduces cellulase susceptibility — critical for coatings stored on job sites where temperature and humidity fluctuations promote microbial growth. Biostability and pH stability together ensure total viscosity reliability.
All data below is sourced exclusively from the Pagina del prodotto Michem HEC.
| Parametro | Specifiche |
|---|---|
| Numero CAS | 9004-62-0 |
| Tipo | Non-ionic cellulose ether |
| Aspetto | Polvere bianca o biancastra |
| Umidità | ≤5% |
| Cenere | ≤5% |
| Valore di pH (soluzione 1%) | 6–8 |
| pH Stability Range | 2–12 |
| Resistenza agli enzimi | Sì |
| Gamma di viscosità | 1.500–8.500 mPa·s (Brookfield LV, soluzione 1%) |
| Grado | Viscosity Range (mPa·s) | Characteristic Advantage |
|---|---|---|
| HE30KB | 1,500–2,500 | Enhances emulsion stability; improves fluidity |
| HE60KB | 2,500–3,500 | Good solubility; flexible formulation design |
| HE100KB | 3,500–6,500 | Eccellente stabilità della viscosità e ritenzione idrica |
| HE150KB | 6,500–8,500 | Efficient thickening; good fluidity properties |
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HEC dosage in water-based construction coatings typically ranges from 0.2% to 0.8% by total formulation weight, depending on the target viscosity and the grade selected:
| Coating Type | Livello consigliato | Dosaggio tipico | Target Viscosity |
|---|---|---|---|
| Interior latex paint (flat) | HE30KB / HE60KB | 0,2-0,4% | 80–120 KU |
| Exterior architectural coating | HE100KB | 0.3–0.5% | 100–130 KU |
| Cementitious waterproof coating | HE100KB / HE150KB | 0.4–0.6% | 120–150 KU |
| Acid-resistant primer (metal) | HE30KB / HE60KB | 0.3–0.5% | 90–110 KU |
| High-build textured finish | HE150KB | 0.5–0.8% | 130–160 KU |
Prepare the grind base. Disperse pigments and extenders (TiO₂, CaCO₃, kaolin) with dispersant in water under high-speed agitation. Do not add HEC at this stage — it will interfere with pigment dispersion efficiency.
Add HEC after let-down. Once the grind is complete and the latex emulsion is added (let-down phase), introduce HEC slowly to the vortex of agitated let-down. Use the direct cold-water addition method: add HEC powder gradually to avoid lumping. Alternatively, prepare a 2% HEC pre-gel and add it as a thickener stock solution for more precise viscosity control.
Adjust pH after full hydration. Allow HEC to fully hydrate (15–30 minutes depending on grade and mesh size) before making any pH adjustments with acids or bases. Premature pH adjustment can slow hydration and cause incomplete dissolution.
Fine-tune with associative thickener. For coatings requiring both high-shear viscosity (application feel) and low-shear viscosity (sag resistance), combine HEC with a small amount of associative thickener (0.1–0.3%) to build a balanced rheology profile.
HEC’s hydroxyethyl substituents are chemically inert at high pH — they resist hydroxide attack because the ether bond in -CH₂CH₂OH is not susceptible to nucleophilic cleavage under alkaline conditions. HPMC’s methoxyl groups (-OCH₃) undergo alkaline hydrolysis above pH 11, stripping substituents and irreversibly degrading the polymer.
Yes. HEC is stable through pH 12. In fresh cement environments (pH 12.5–13), the coating’s internal pH is typically buffered to ≤12 by the latex emulsion and other formulation components. HEC retains >90% viscosity under these conditions. For sustained pH >12 exposure, verify compatibility with your specific formulation using Michem’s free sample testing program.
Associative thickeners rely on hydrophobic interactions that can be disrupted by surfactants and co-solvents. HEC’s non-ionic mechanism is independent of surfactant chemistry and provides more robust viscosity stability in complex construction coating formulations. However, associative thickeners offer better high-shear rheology — the two are often used together for optimal results.
Absolutely. Construction coatings are often stored outdoors at job sites where temperature and humidity fluctuations promote microbial growth. Cellulase enzymes from microbial contamination degrade unprotected cellulose ethers, causing viscosity loss over weeks or months. Michem HEC’s enzyme-resistant modification prevents this biological degradation, ensuring stable viscosity throughout the product’s shelf life and on-site storage period.
Start with HE100KB (3,500–6,500 mPa·s) as a general-purpose grade. It offers excellent viscosity stability and water retention — the two properties most critical in construction coatings. If your formulation targets lower viscosity (flowing coatings, acidic primers), move to HE60KB. For high-build or textured coatings requiring efficient thickening at minimal dosage, use HE150KB. Request free samples from Michem to benchmark each grade in your specific formulation.
pH stability is not a luxury in construction coatings — it is a requirement driven by the chemistry of cement substrates (pH 12–13), acidic service environments, and the complex ionic compositions of modern coating formulations. HEC’s non-ionic architecture makes it the only cellulose ether thickener that survives the full pH 2–12 range without viscosity loss, chemical degradation, or precipitation. CMC and HPMC each have pH limits that exclude them from critical construction coating applications. Michem HEC, with its four verified viscosity grades (HE30KB through HE150KB), enzyme resistance, and proven pH stability, gives construction coating formulators a single, reliable thickener platform that works across acidic primers, neutral latex paints, and alkaline cementitious coatings — no grade-switching, no formulation compromises, no field failures from pH-related viscosity collapse.
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