{"id":15347,"date":"2026-08-19T06:20:05","date_gmt":"2026-08-19T06:20:05","guid":{"rendered":"https:\/\/tenessy.com\/?p=15347"},"modified":"2026-08-19T06:20:15","modified_gmt":"2026-08-19T06:20:15","slug":"hpmc-per-massa-autolivellante","status":"publish","type":"post","link":"https:\/\/tenessy.com\/it\/hpmc-per-massa-autolivellante\/","title":{"rendered":"HPMC per composti autolivellanti: una guida tecnica completa"},"content":{"rendered":"\t\t
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HPMC for self-leveling compound is a low-viscosity, precisely dosed cellulose ether that stabilizes bubbles, prevents aggregate settling, and controls water loss \u2014 without killing the flow that makes a floor level itself. This is the opposite of tile adhesive HPMC: in self-leveling underlayment (SLU), the goal is a highly fluid, self-densifying slurry that cures to a flat, pinhole-free surface, so the HPMC grade must be low in viscosity and the dosage kept in the 0.05\u20130.15% range. This guide covers the mechanism, grade selection, defoamer and flow-agent interaction, and how to fix pinholes and bleeding.<\/p>

Introduction<\/h2>

Self-leveling compound (SLC), also called self-leveling underlayment, is a high-flow cementitious (or gypsum) system poured at 2\u201310 mm thickness over concrete subfloors to create a perfectly flat surface for flooring, tile, or wood. Unlike troweled mortars, SLC must flow, de-aerate, and self-level within minutes of pouring \u2014 then set hard without segregation, pinholes, or shrinkage. That combination of fluidity and stability is precisely why self-leveling HPMC is a special product category.<\/p>

Hydroxypropyl methyl cellulose (HPMC) plays a supporting but essential role in SLC, and the rules are reversed compared to other mortars. Where a tile adhesive needs 75000\u2013100000 mPa\u00b7s HPMC to hold a 3 mm bed on a wall, self-leveling compound typically uses 400\u20131000 mPa\u00b7s HPMC at 0.05\u20130.15%<\/strong>. The reasons are physical: in a self-leveling slurry, viscosity build-up fights the very flow you need, while a complete absence of HPMC leads to bleeding, settling, and surface defects. The art is in the low dose. At TENESSY Chemical, where we supply HPMC to SLC producers in over 40 countries, we find that most formulation trouble in SLC comes from treating it like a mortar and applying mortar logic to a fluid system.<\/p>

The Role of Low-Viscosity HPMC in Self-Leveling Systems<\/h2>

In a self-leveling slurry, the HPMC performs four functions \u2014 none of which is “thickening for the sake of thickness”:<\/p>

1. Air-bubble stabilization and control.<\/strong> Fresh SLC is mixed with a high-shear paddle, which entrains air. Without a stabilizer, large bubbles rise and burst, leaving pinholes and craters in the surface. HPMC increases the viscosity of the liquid phase just enough to slow bubble rise and coalescence, and its polymer film stabilizes the bubbles so they can be broken by the defoamer in a controlled way rather than erupting at the surface. This is the number-one job of HPMC in SLC: surface quality.<\/p>

2. Anti-sedimentation of fine and coarse particles.<\/strong> The SLC slurry contains cement, fine sand, and fillers of different densities. Given a minute of rest, particles settle and water bleeds to the surface \u2014 a phenomenon called segregation or bleeding. Even 0.05\u20130.1% of low-viscosity HPMC raises the yield stress of the water phase enough to suspend the fines and slow the settling of heavier grains, keeping the mix uniform as it flows and sets.<\/p>

3. Water retention against porous subfloors.<\/strong> Concrete subfloors absorb water aggressively. Where the floor is dry and porous, the bottom of the SLC layer can lose water before setting, producing a weak, dusty interface and curling. A small HPMC dose holds water in the layer \u2014 but here’s the twist: the dose must be low enough that the surface still dries and hardens predictably. Overdosing SLC with HPMC produces a surface that stays soft (“wet trowel marks”) and retards the set.<\/p>

4. Consistency and tolerance to water variation.<\/strong> Site water addition varies. HPMC damps the viscosity difference between a slightly wet and slightly dry mix, giving the applicator a more forgiving product \u2014 as long as the grade is low enough not to sacrifice flow.<\/p>

Choosing the Right Viscosity Grade<\/h2>

Self-leveling systems divide into cement-based (the global majority) and gypsum-based (calcium sulfate) types. Selection differs slightly:<\/p>

Application<\/p><\/td>

Recommended HPMC viscosity<\/p><\/td>

Recommended dosage<\/p><\/td>

Notes<\/p><\/td><\/tr>

Cementitious SLC, 2\u20135 mm<\/p><\/td>

400\u20131000 mPa\u00b7s<\/p><\/td>

0.05\u20130.12%<\/p><\/td>

Standard interior underlayment<\/p><\/td><\/tr>

Cementitious SLC, 5\u201310 mm thick<\/p><\/td>

600\u20131000 mPa\u00b7s<\/p><\/td>

0.08\u20130.15%<\/p><\/td>

Higher layer weight needs more suspension<\/p><\/td><\/tr>

Gypsum SLC<\/p><\/td>

400\u2013800 mPa\u00b7s<\/p><\/td>

0.05\u20130.10%<\/p><\/td>

Gypsum sets fast; keep dose minimal<\/p><\/td><\/tr>

Heavy-duty \/ trafficable SLC<\/p><\/td>

600\u20131000 mPa\u00b7s<\/p><\/td>

0.08\u20130.12%<\/p><\/td>

Balance with high-strength binder<\/p><\/td><\/tr>

Repair \/ patch leveling (thin)<\/p><\/td>

400\u2013600 mPa\u00b7s<\/p><\/td>

0.03\u20130.08%<\/p><\/td>

Minimal retention; fast set desired<\/p><\/td><\/tr><\/tbody><\/table>

Why not 40000 mPa\u00b7s? Test it once and you’ll see: a 40000-grade at any effective dose makes the slurry thixotropic and “sticky,” it refuses to self-level, the surface sets up with trowel ridges, and air bubbles get trapped as coarse foam. Low-viscosity grades (which in reality are medium\/low molecular weight HPMC) give you the suspension and retention effects with a small fraction of the viscosity penalty.<\/p>

Also consider particle size and surface treatment.<\/strong> For SLC mixed at site with a paddle, surface-treated low-viscosity HPMC disperses without lumps. In pre-blended bags poured through automated mixing pumps, untreated grades may be fine. In both cases, the HPMC is pre-blended with the dry powder \u2014 never added directly to the mixing water.<\/p>

Interaction with Defoamers and Flow Agents<\/h2>

Self-leveling formulation is a three-way balance among HPMC, defoamer, and flow agent (superplasticizer):<\/strong><\/p>