HPMC Selection Guide — How to Choose the Right Grade for Your Dry Mix Mortar

Quick Answers

1. What Parameters Define an HPMC Grade?

Viscosity is reported in mPa·s, but the numerical value depends entirely on the test method. The same HPMC sample measured under different methods produces vastly different numbers.

Note: Brookfield LV and NDJ give comparable readings at low to medium viscosities (up to ~60,000 mPa·s). At higher viscosities (100,000 mPa·s and above), NDJ readings are approximately 40-50% of Brookfield LV readings. For example, HP 100M shows 80,000-120,000 mPa·s on Brookfield LV but 40,000-50,000 mPa·s on NDJ. CHARING uses NDJ as the standard method. All viscosity values in this guide use Brookfield LV unless otherwise noted.

Key conversion reference: Dow WALOCEL datasheets report viscosity using the Haake method. At 2%, a Dow viscosity of 40,000-45,000 mPa·s (Haake) corresponds approximately to 100,000 mPa·s on Brookfield LV. A Dow viscosity of 60,000-80,000 corresponds approximately to 200,000 on Brookfield LV. Always verify which test method a viscosity number refers to before comparing products.

Commercial construction grades range from 400 mPa·s to 200,000 mPa·s (Brookfield LV).

> Note: Viscosity recommendations for other applications (EIFS, render, putty, grout, gypsum plaster) depend on local conditions, formulation goals, and raw material quality. The above table only covers applications with established CHARING product recommendations.

Why large-format tile adhesive uses lower viscosity: Large tiles require longer open time for positioning and better surface wetting to achieve full contact between the adhesive and the low-porosity tile surface. Higher viscosity HPMC reduces wetting and can trap air at the interface. At C2 level, RDP provides the primary strength and flexibility contribution — the HPMC grade can be lower viscosity to optimize workability without sacrificing water retention. Standard C1 tile adhesive uses 80,000-120,000 mPa·s because it relies more heavily on HPMC for both water retention and sag resistance.

Gel temperature is the temperature at which an HPMC solution transitions from liquid to gel, losing its water-retention capability. Standard HPMC gels around 55-65°C.

Why this matters: In hot climates where substrate temperatures exceed 40-50°C (common in the Middle East, North Africa, South and Southeast Asia), standard HPMC can gel prematurely on the substrate surface. The result is a dramatic drop in open time — from 20 minutes to as little as 7-10 minutes.

- Methoxy (DS): 1.3-2.0 for construction grades. Higher DS improves water solubility and raises gel temperature.

- Hydroxypropyl (MS): 0.1-0.3 for construction grades. Higher MS improves cold-water solubility.

Standard HP series: methoxy 23-27%. HK series: methoxy 19-22% — lower methoxy but higher gel temperature (65°C vs 60°C). This trade-off is deliberate: HK sacrifices some water retention for better high-temperature stability.

- Non-surface treated (M grades): Dissolve rapidly in cold water but can form lumps if not dispersed properly before water contact. Examples: HP 60M, HP 100M.

- Surface treated (MS grades): Dissolve slowly and uniformly, preventing lump formation during on-site mixing. Examples: HP 60MS, HP 100MS.

For factory-produced dry mix mortar with controlled mixing, non-surface-treated grades are standard. For on-site applications or where mixing quality cannot be guaranteed, surface-treated grades provide insurance against lumping.

2. How to Choose HPMC for Tile Adhesive

This is the most frequently asked question by formulators. The answer depends on three factors:

By tile format:

- Standard ceramic tiles (≤600 mm), C1: 80,000-120,000 mPa·s

- Large-format porcelain (≥800 mm), C2: 45,000-75,000 mPa·s — lower viscosity for better wetting and longer open time

Large-format tiles need better surface wetting to achieve full bond contact with low-porosity surfaces. Lower viscosity HPMC improves wetting and extends open time for tile positioning. At C2 level, the high RDP dosage (30-55 kg/t) provides the primary strength and flexibility — HPMC can be lower viscosity to optimize workability.

By adhesive grade:

- C0/C1: HP 100M or HK 100M (80,000-120,000 mPa·s) is the workhorse grade

- C2: HP 60M (45,000-75,000 mPa·s) — lower viscosity balances workability with high RDP loading

- C2S1/C2TES1 (flexible, large format): HP 100M, or HP 60M depending on climate

By climate (this is the biggest variable):

- Tropical (Southeast Asia, Middle East, Africa, South America): HP 200M for C0/C1, HP 100M for C2. HK 100M is also very popular in these markets due to its 65°C gel temperature — higher heat resistance, but shorter open time (within 20 minutes).

- Temperate (China, Europe, North America): HP 100M for C1, HP 60M for C2.

- Cold (Russia, Canada, Northern Europe): HP 60M or HP 40M. Lower viscosity dissolves faster and improves cold-weather workability.

This is a real-world consideration that many guides overlook. Thicker applications (5 mm or more) lose water more slowly through the mortar body, so HPMC dosage can be at the lower end of the range (2.0-2.5 kg/t). Thin-bed applications (3 mm or less) expose more surface area relative to volume, accelerating water loss — dosage should be at the upper end (2.5-3.0 kg/t). This variation is more significant than the difference between C1 and C2 formulations.

3. Choosing HPMC by Application — Full Matrix

Self-leveling demands ultra-low viscosity. Higher viscosity traps air and reduces flow. HP 400 is purpose-built for this application.

4. Climate Zone Selection Guide

Key insight for tropical markets: Many manufacturers in hot countries use low HPMC dosage with high-viscosity grades (HP 200M or HK 100M). The high viscosity compensates for low dosage by holding more water in the matrix. The trade-off is reduced surface moisture and workability. HK 100M is particularly popular in Southeast Asia and the Middle East — its 65°C gel temperature provides better heat resistance than HP series, and the cost is lower. The downside is a shorter open time, typically within 20 minutes.

5. CHARING HP, HK, and MH Series — How to Choose

MHEC (Methyl Hydroxyethyl Cellulose) is produced with ethylene oxide instead of propylene oxide, resulting in a fundamentally higher gel temperature. Where HP series gels at 55-65°C and HK at 65-70°C, MH series maintains full performance up to 70-90°C. This is not a marketing claim — it is a chemical difference in the etherification process.

For formulators in Gulf states or equatorial regions where substrate temperatures routinely exceed 50°C in summer, MH series is the only reliable option. Standard HPMC at 55°C gel temperature will lose water retention within minutes on a 50°C substrate.

- Non-S (M grades): HP 60M, HP 100M, HK 100M — for factory dry mix production with controlled mixing. Standard choice.

- S grades (MS): HP 60MS, HP 100MS — for on-site mixing or applications where operators may not follow precise mixing procedures. The delayed solubility prevents lump formation.

6. Frequently Asked Questions

Selecting viscosity based on price rather than performance. Inexpensive HPMC often has poor substitution uniformity, causing batch-to-batch water retention variation. One batch may hold water for 20 minutes, the next for only 10. Always test gel temperature alongside viscosity before committing to bulk supply.

No. The choice depends on the adhesive grade, not on whether the tile goes on a wall or floor. Most floor tile adhesives are C0 or C1 grade — these use HP 100M or HP 200M, or HK 100M or HK 200M. Wall applications are more varied: standard wall tiles may also be C1 using the same HPMC, but large-format or porcelain wall tiles require C2 grade, which calls for HP 60M. The HPMC changes because the grade changes, not because the surface changes. HP 60M is a premium grade with a higher cost structure — there is no reason to use it in a basic floor tile formulation where HP 100M or HP 200M, or HK 100M or HK 200M already performs well.

Substrate temperatures in the Gulf can reach 50-65°C in summer. Standard HPMC with 55-65°C gel temperature will fail. Use HK series (65°C minimum) or MH series (70-90°C). HK 200M is the most commonly used grade in Saudi Arabia and UAE markets — the high viscosity compensates for rapid water evaporation while the 65°C gel temperature provides adequate heat resistance at a competitive cost. Installers must work within the shorter open time window typical of HK series.

1. Replace part of coarse sand with fine sand (70-140 mesh)

2. Avoid rapid-hardening cement

3. Use HP series instead of HK — HP has inherently longer open time

4. Add cellulose fiber (1-3 kg/t)

No. Above certain thresholds, high viscosity reduces substrate wetting, entrains air, and can decrease tensile bond strength. The effect is application-specific: in self-leveling, high viscosity is a defect. In tile adhesive, 100,000-150,000 mPa·s is the upper practical limit for most formulations. Beyond this, workability suffers without proportional gain in water retention.

Water retention drops below the level needed for complete cement hydration. The result: a weak, powdery bond layer at the tile-adhesive interface. This is the number one cause of tile debonding in hot, dry conditions. The minimum water retention rate for a professional tile adhesive is 94%.

MHEC (Methyl Hydroxyethyl Cellulose) uses ethylene oxide in the etherification process, giving it a higher gel temperature (70-90°C vs 55-65°C for standard HPMC). In temperate climates, MHEC offers no advantage. In tropical and desert climates, the higher gel temperature is the deciding factor between a formulation that works and one that fails. MHEC is also used where the local market standard requires it — for example, some European specifications mandate MHEC for exterior applications.

7. Quick Reference — CHARING Product Grades

Note: All recommendations are based on typical formulation conditions. Cement quality, sand gradation, and local climate vary. Laboratory trials with your specific raw materials are essential before production.

For technical inquiries: info@sdcharing.com

Shandong Charing Industry Co., Ltd.

www.sdcharing.com