Plastics - Phenolic resins - Determination of pH
This standard is identical to the international standard ISO 8975-89 Plastics - Phenolic resins - Determination of pH.
1 Subject content and application scope
The standard specifies a method for the determination of the pH of liquid phenolic resins at the manufacturing stage or on the market.
This standard is applicable to liquid phenolic resins. See Annex A for solid phenolic resins. With liquid resins having a viscosity greater than 2Pa·s, it may be necessary to use Annex A.
2 Principle
The potential difference between a glass electrode and a reference electrode immersed in the same solution is used to determine the pH.
3 Reagents
3.1 Potassium hydrogen phthalate standard solution
c(KCOOC6H4COOH) = 0.05mol/L, pH = 4.00 at 23℃.
Dissolve 10.21g of potassium hydrogen phthalate, previously dried by heating at 100℃ to 130℃ for 2h, in water and make up to 1,000mL.
This solution shall be stored in a glass vessel and kept away from any traces of acid or base; it may be kept longer by adding a crystal of thymol. Slight cloudiness in the solution indicates microbial contamination. The thymol is no longer effective and such a solution shall be discarded.
3.2 Hydrogen phosphate buffer solution
It contains approximately 0.025mol of potassium dihydrogen phosphate (KH2PO4) per litre and approximately 0.025mol of sodium hydrogen phosphate (Na2HPO4) per litre, pH=6.88 at 23℃.
1 Subject content and application scope
2 Principle
3 Reagents
4 Apparatus
5 Procedure
6 Expression of results
7 Test report
Annex A (Informative) Plastics - Solid phenolic resins - Determination of pH
