ISO 127:2012 pdf download.Rubber, natural latex concentrate -Determination of KOH number.
This International Standard specifies a method for the determination of the KOH number of natural rubber
latex concentrate which is preserved wholly or in part with ammonia. The method is applicable to latices -. containing boric acid. The method is not applicable to latices preserved with potassium hydroxide. It is not necessarily suitable for latices from natural sources other than Hevea brasiliensis, or for latices of synthetic rubber, compounded latex, vulcanized latex or artificial dispersions of rubber.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 123, Rubber latex — Sampling
ISO 124, Latex, rubber — Determination of total solids content
ISO 125, Natural rubber latex concentrate — Determination of alkalinity
ISO 976, Rubber and plastics — Polymer dispersions and rubber latices — Determination of pH
ISO 1802, Natural rubber latex concentrate — Determination of boric acid content
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
KOH number
number of grams of potassium hydroxide equivalent to the acid radicals combined with ammonia in latex containing 100 g of total solids
[ISO 1382:2008]
4 Reagents
During the analysis, use only reagents of recognized analytical grade and only distilled water free of dissolved carbon dioxide, or water of equivalent purity.
4.1 Potassium hydroxide, standard volumetric solution, c(KOH) = 0,1 mol/dm3, carbonate-free.
4.2 Potassium hydroxide, standard volumetric solution, c(KOH) = 0,5 mol/dm3, carbonate-free.
5 Apparatus
Standard laboratory glassware, plus the following:
5.1 pH-meter, conforming to ISO 976 but capable of being read to 0,01 units.
5.2 Glass electrode, of a type suitable for use in solutions of pH up to 12,0.
5.3 Mechanical stirrer, with earthed motor and glass paddle, or magnetic stirrer.
An automatic titrator may be used provided it has been checked as giving the same result as the standard method.
6 Sampling
Carry out the sampling in accordance with one of the methods specified in ISO 123.
7 Procedure
Calibrate the pH-meter by the method specified in ISO 976. If the total solids (“Ts) and alkalinity (A) of the latex are not known, determine them in accordance with ISO 124 and ISO 125, respectively. If the latex contains boric acid and the content is not known, determine it in accordance with ISO 1802.
Carry out the determination in duplicate.
Weigh, to the nearest 0,1 g, into a 400 cm3 beaker a test portion (mass in) of the test sample containing.ISO 127 pdf download.