JC/T 2556-2020 in English
VALIDDetermination of vinyl acetate content in waterproof board modified by ethylene-vinyl acetate copolymers
- Issued on:2020-04-16
- Implemented on:2020-10-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
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本标准规定了测定乙烯-乙酸乙烯酯共聚物（EVA）改性防水板中乙酸乙烯酯（VA）含量的测定方法,二次蒸馏-水解返滴定法和红外光谱法。
本标准规定的二次蒸馏-水解返滴定法适用于VA含量为1%～14%之间的EVA防水板，不适用于ECB防水板。
本标准规定的红外光谱法适用于VA含量在3%～14%之间的EVA防水板和ECB防水板。
当二次蒸馏-水解返滴定法和红外光谱法同时适用时，二次蒸馏-水解返滴定法为仲裁法。
Introduction
Standard Technical Background
With the widespread application of ethylene-vinyl acetate copolymers in waterproof materials, JC/T 2556-2020 has established a standardized determination method for the content of vinyl acetate (VA) in EVA waterproof sheets for the first time. This standard was jointly developed by the China Building Materials Federation and several other organizations including the China Building Materials Inspection and Certification Group, filling the gap in the standard for the detection of modified waterproof sheet components.
Comparative analysis of methods
| Dimension | Secondary distillation-hydrolysis back titration method | Infrared spectroscopy |
|---|---|---|
| Scope of application | EVA waterproof board with VA content of 1%-14% | EVA/ECB waterproof board with VA content of 3%-14% |
| Detection limit | 1% | 3% |
| Precision requirement | ≤10% in the same laboratory, ≤20% in different laboratories | Standard curve needs to be established |
| Arbitration validity | Preferential use | Auxiliary methods |
Key operating points
Secondary distillation-hydrolysis back titration method
Typical experimental steps: weigh 1g±0.1mg sample → add xylene to dissolve → potassium hydroxide-ethanol solution to hydrolyze → excess acid to neutralize → sodium hydroxide back titration. In the calculation formula, 0.08609 is the conversion factor for the molar mass of vinyl acetate.
Infrared spectroscopy method
Five reference samples with different VA contents (3%-14%) need to be prepared, and a standard curve of the absorbance ratio of 1740cm-1 (C=O) to 720cm-1 (CH2) needs to be established using a Fourier transform infrared spectrometer. The sample thickness should be ≤200μm.
Implementation recommendations
- ECB waterproofing board must use infrared spectroscopy
- Low VA content (<3%) samples are recommended to use hydrolysis back titration
- The arbitration test requires three parallel measurements to take the average value
- The infrared spectroscopy method requires regular verification of the standard curve
Technology evolution trend
This standard refers to international methods such as ASTM D5594, and innovatively combines traditional chemical analysis methods with modern instrumental analysis methods. Rapid detection technologies such as near infrared spectroscopy may be introduced in the future, but at this stage, hydrolysis back titration is still the most reliable benchmark method.
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