For formulators and engineers seeking reliable, fast-curing epoxy systems — particularly under challenging low-temperature conditions — the choice of curing agent is critical. Toray POLYTHIOL QE-340M has long been a recognized option in this field. Today, we present SINOMER® PM839: a technically comparable, domestically produced, and cost-competitive alternative that matches or exceeds key performance benchmarks, offering a reliable solution for your supply chain.
This direct comparison demonstrates how SINOMER® PM839 serves as a drop-in replacement for QE-340M, with the added benefits of transparent data, accessible support, and enhanced value.
Test Formulation: E51/BER-128 : PM839 : DMP-30 = 100 g : 100 g : 10 g
Property | Condition | Result |
Gel Time | –5°C | 3 min 20 s |
27°C, 70% RH | 2 min 40 s | |
Hardness (Shore D), 24h | –5°C | 75 |
27°C, 70% RH | 84 | |
Lap Shear Strength (MPa), 24h | –5°C | 9 |
27°C, 70% RH | 19 |
Notes:
Hardness sample size: φ35 mm × 6 mm
Lap shear substrate: steel, 25 mm × 100 mm × 1.6 mm
SINOMER® PM839 cures rapidly even at low temperatures and develops high hardness. Data shown for –5°C and 27°C / 70% RH.
Formulation A: E51/BER-128 : PM839 : DMP-30 = 100 : 100 : 5
Formulation B: E51/BER-128 : PM839 : DMP-30 = 100 : 100 : 10
Time | Formulation A | Formulation B | ||
–5°C | 27°C, 70% RH | –5°C | 27°C, 70% RH | |
0.5 h | 66 | 73 | 68 | 78 |
1 h | 67 | 75 | 70 | 82 |
3 h | 65 | 76 | 75 | 82 |
24 h | 70 | 78 | 75 | 84 |
3 d | 68 | 79 | 74 | 82 |
*Note:
DMP-30 is 2,4,6-Tris(dimethylaminomethyl)phenol.
Hardness sample size: φ35 mm × 6 mm.*
Figure 1.
Hardness development of E51(BER-128) / PM839 / DMP-30 at –5°C and 27°C / 70% RH
(Left: 100:100:5; Right: 100:100:10)
SINOMER® PM839 develops high lap shear strength quickly, even at low temperatures.
Formulation A: E51/BER-128 : PM839 : DMP-30 = 100 : 100 : 5
Formulation B: E51/BER-128 : PM839 : DMP-30 = 100 : 100 : 10
Time | Formulation A | Formulation B | ||
–5°C | 27°C, 70% RH | –5°C | 27°C, 70% RH | |
0.5 h | 4 MPa | 7 MPa | 6 MPa | 12 MPa |
1 h | 5 MPa | 8 MPa | 9 MPa | 16 MPa |
3 h | 6 MPa | 10 MPa | 7 MPa | 18 MPa |
24 h | 11 MPa | 18 MPa | 9 MPa | 19 MPa |
3 d | 12 MPa | 20 MPa | 9 MPa | 17 MPa |
Note: Substrate for lap shear: steel, 25 mm × 100 mm × 1.6 mm.
Figure 2.
Lap shear strength development of E51(BER-128) / PM839 / DMP-30 at –5°C and 27°C / 70% RH
(Left: 100:100:5; Right: 100:100:10)
The table below provides a clear, side-by-side comparison of core specifications and curing performance, based on publicly available TDS data and our internal testing.
| Property / Test | Toray POLYTHIOL QE-340M | SINOMER® PM839 | Key Takeaway |
|---|---|---|---|
| Appearance | Clear liquid | Colorless transparent liquid | Comparable |
| Viscosity @ 25°C | 10.0–18.0 Pa·s | 12,000–14,000 mPa·s | Similar range |
| Color (APHA/Hazen) | ≤ 300 (Typ. 15) | ≤ 20 | Superior color |
| Mercaptan Content | 10.0–14.0 wt% | 12.5 wt% | Directly comparable activity |
| Gel Time @ ~5°C | 7.5 min (at 5°C) | ~3.3 min (at -5°C) | Faster cure under more severe conditions |
| Gel Time @ Ambient | 3.5 min (23°C) | 2.7 min (27°C) | Comparable / faster |
| Hardness, 24h (Shore D) | 79 (5°C) / 84 (23°C) | 75 (-5°C) / 84 (27°C) | Achieves same final hardness |
| Lap Shear Strength, 24h | 15 MPa (5°C & 23°C) | 9 MPa (-5°C) / 19 MPa (27°C) | Higher strength at ambient |
| Low-Temp Validation | Data at 5°C | Data at -5°C | Tested under harsher conditions |
*Note: Gel time and strength tests for SINOMER® PM839 conducted with catalyst DMP-30. Toray data uses catalyst EHC-30. Both catalysts are tris-dimethylaminomethyl phenol derivatives, ensuring comparable acceleration mechanisms.*
Curing Speed: PM839 demonstrates a significantly faster gel time at lower temperatures, potentially improving production cycle times.
Final Properties: It achieves the same high final hardness (Shore D 84) and offers higher lap shear strength at room temperature.
Low-Temperature Assurance: With performance data validated at -5°C, PM839 provides extra confidence for applications in cold environments.
Cost-Effectiveness: As a domestically manufactured product, SINOMER® PM839 typically offers a favorable price-to-performance ratio, reducing formulation costs without sacrificing quality.
Logistical Simplicity: Avoid import delays, complex logistics, and currency fluctuations. Enjoy shorter lead times and reliable supply.
Direct Technical Support: Access direct communication with our application engineers for formulation troubleshooting and optimization support.
For a direct substitution in formulations currently using QE-340M, we recommend the following starting point:
Replace QE-340M with SINOMER® PM839 on a 1:1 weight basis.
Use the same amine catalyst (e.g., DMP-30, EHC-30, or similar tertiary amines) at the standard recommended dosage (e.g., 5-10 phr).
Conduct a small-scale gel time and property verification test to fine-tune for your specific epoxy resin and process conditions.
This straightforward approach minimizes reformulation effort and accelerates your validation process.
Choosing SINOMER® PM839 is not just about finding an alternative; it's about making a strategic decision for equal performance, greater security, and better value. It delivers the rapid, low-temperature cure required for demanding applications in adhesives, coatings, and composites, while providing the tangible benefits of a localized, responsive supply chain.
