To determine the quality of the epoxy accelerator DMP-30 (2,4,6-tris(dimethylaminomethyl)phenol),
a comprehensive
evaluation can be conducted from aspects
such as **appearance and physical property testing**, **chemical index analysis**,
**application performance testing**, and **impurity and safety assessment**.
The specific methods are as follows: ### **I. Appearance and Physical Property Testing**
1. **Appearance and State** - *
*Normal Standard**: Colorless to light yellow transparent liquid,
free of suspended matter or precipitation. -
**Abnormality Judgment**: Dark color (such as tan), turbidity, or layering may indicate raw
material oxidation, impurity residue, or deterioration due to improper storage.
2. **Odor** - **Normal Standard**: Characteristic amine odor (similar to ammonia or weak alkaline smell),
without pungent stench or peculiar smell.
- **Abnormality Judgment**: Strong rancid or putrid odor may indicate product decomposition or
contamination.
3. **Density and Viscosity**
- **Testing Method**: Measure using a densitometer or
viscometer (such as a rotational viscometer), with reference to standard values
(typically density: approximately 0.97–0.99 g/mL; viscosity: approximately 20–50 mPa·s/25°C).
- **Quality Correlation**: Deviations from the standard range in density or viscosity may indicate
unstable production processes or adulteration with other solvents. ###
**II. Chemical Index Analysis**
1. **Amine Value (Key Index)**
- **Testing Principle**: Determine the amino content through acid-base titration to reflect the
active ingredient concentration.
- **Standard Range**: Theoretical amine value is approximately
**500–530 mgKOH/g** (purity ≥ 99%).
- **Quality Judgment**: - Amine value close to the theoretical value:
High purity and strong promoting effect. - Low amine value: May contain water,
low-molecular impurities, or incomplete synthesis.
2. **Moisture Content** - **Testing Method**: Karl Fischer method (volumetric or coulometric method).
- **Standard Requirement**: High-quality products have a moisture content ≤ 0.5% (some high-end
products require ≤ 0.3%).
- **Risk Warning**: Excessive moisture can cause emulsification in the epoxy resin system,
affect curing effects, and even corrode metal substrates.
3. **pH Value** - **Testing Method**: Measure the pH of a 10% aqueous solution using a
pH test strip or pH meter.
- **Normal Range**: Alkaline, with a pH of approximately 10–12.
- **Abnormality Judgment**: A pH lower than 9 (e.g., <9) may indicate the presence of acidic
impurities or decomposition products,
affecting the accelerator's activity.
4. **Purity and Impurities**
- **Testing Method**: Analyze using gas chromatography (GC) or high-performance liquid
chromatography (HPLC). - **Key Indicators**: - Main component (DMP-30) content ≥ 99%.
- Impurities (such as free amines and phenolic by-products) ≤ 1%.
- **Risk Points**: Impurities may cause abnormal curing speed, product discoloration,
or degradation of mechanical properties. ### **III.
Application Performance Testing**
1. **Curing Promotion Effect** - **Testing Method**: - Mix at a fixed ratio (e.g., 100 parts epoxy resin,
0.5–2 parts DMP-30) and observe the gel time (25°C).
- High-quality products should control the gel time within **30–60 minutes**
(specific time varies by epoxy resin type).
- **Judgment Basis**: - Too short gel time: May contain excessive catalyst, leading to insufficient
working time. - Too long gel time: Low accelerator activity, possibly due to insufficient purity or failure.
2. **Properties of Cured Products**
- **Testing Items**:
- **Mechanical Properties**: Tensile strength, flexural strength (refer to standards such as
GB/T 2568 and GB/T 2567). - **Thermal Properties**: Glass transition temperature (Tg, DSC method),
heat resistance (e.g., water resistance, aging resistance).
- **Quality Correlation**: - High-quality accelerators should enable cured products to meet
industry standards (e.g., tensile strength ≥ 30 MPa, Tg ≥ 60°C).
- Significantly lower-than-expected performance may indicate poor compatibility between
the accelerator and resin or cross-linking structure interference from impurities.
3. **Color Stability** - **Testing Method**: Age the cured epoxy resin sample under ultraviolet
light or high temperature and observe color changes.
- **Quality Requirement**: High-quality products should prevent yellowing or blackening of
cured products, especially for light-colored or transparent products.
### **IV. Impurity and Safety Assessment**
1. **Heavy Metals and Harmful Substances**
- **Testing Items**: Lead (Pb), mercury (Hg), cadmium (Cd), etc. (refer to RoHS and REACH regulations).
- **Application Scenarios**: For applications in food contact, medical, and other fields,
strict control of harmful impurities is required (e.g., Pb ≤ 10 ppm).
2. **Storage Stability** - **Testing Method**: Store the sample at 50°C for 7 days and observe
changes in appearance and amine value.
- **Quality Requirement**: Qualified products should show no obvious discoloration or layering,
with an amine value decrease ≤ 5%.
### **V. Reference Standards and Supplier Qualifications**
1. **Implementation Standards**: - Domestic reference: General requirements for amine-based
curing agents in HG/T 4883-2016 *Amine Curing Agents for Epoxy Resins*.
- International reference: ASTM D2073 *Standard Test Methods for Amine Curing Agents*.
2. **Supplier Qualifications**: - Request a COA (certificate of analysis) and MSDS (material safety data sheet)
, focusing on amine value, moisture, and purity data. - Prioritize manufacturers certified under the
ISO 9001 quality management system to reduce batch stability risks.
### **Summary: Quick Judgment Steps**
1. **Preliminary Screening**: Observe appearance and odor, measure density/viscosity, and eliminate
obviously abnormal products.
2. **Core Testing**: Commission third-party testing agencies to determine amine value, moisture,
and purity (GC/HPLC).
3. **Application Verification**: Test curing speed and product performance through small samples
to ensure they meet actual requirements. For extremely high-quality requirements
(e.g., aerospace, electronic packaging), long-term aging tests and toxicological evaluations
are recommended to avoid potential risks.
