Detail of GB/T 20405.1-2023

Introduction of GB/T 20405.1-2023

GB/T 20405.1-2023 Urine-absorbing aids for incontinence - Polyacrylate superabsorbent powders - Part 1: Test methods for determination of pH WARNING - This document does not claim to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this document to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. It is expected that the person performing this test has been fully trained in all aspects of this procedure. 1 Scope This document provides a test method for determining the pH of granular superabsorbent polyacrylates. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements 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 187 Paper, board and pulps - Standard atmosphere for conditioning and testing and procedure for monitoring the atmosphere and conditioning of samples Note: GB/T 10739-2002, Paper, board and pulps - Standard atmosphere for conditioning and testing (ISO 187:1990, EQV) ISO 3696 Water for analytical laboratory use - Specification and test methods Note: GB/T 6682-2008, Water for analytical laboratory use - Specification and test methods (ISO 3696:1987, MOD) ISO 10523 Water quality - Determination of PH Note: GB/T 22592-2008, Water treatment reagent - General rules for the determination of pH (ISO 10523:1994, NEQ) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 sample product or portion of a product taken from a production lot for testing purposes and identifiable and traceable back to its origin 4 Principle The pH of the saline solution to which polyacrylate superabsorbent powders are added is determined using a pH meter and a standardized glass pH‑responsive electrode. 5 Reagents and materials Use only reagents of recognized analytical grade, unless otherwise specified. 5.1 Water. Grade 3 water according to lS0 3696, with the exception that the conductivity can be as high as 30 μS/cm. 5.2 Sodium hydroxide solution. c(NaOH) = 0.1 mol/l. Obtained as ready-made analytical grade solution. 5.3 Hydrochloric acid solution. c(HCI)= 0.1 mol/l. Obtained as ready-made analytical grade solution. 5.4 Sodium chloride solution. 5.4.1 0.9 % mass fraction of sodium chloride solution in water. Weigh (9.00 ± 0.01) g of sodium chloride into a 1 l beaker and add (991.0 ± 0.1) g of deionized water (grade 3). Stir until dissolved. 5.4.2 The conductivity of the solution should be checked prior to each use using properly calibrated measuring equipment. The expected conductivity of a 0.9 % saline solution is of the order of 1600 S/m at 25 °C. Each testing lab shall determine the correct conductivity for the conditions obtaining in the lab. lt is also recommended that the temperature of the solution be maintained at (23 ± 2) °C for the duration of the test. As this matches the required laboratory temperature, it is not necessary to record the solution temperature. 5.4.3 Adjust the pH of the saline solution to (6.0 ± 0.05) using 0.1 mol/l sodium hydroxide or hydrochloric acid solution. 5.5 Standard buffer solutions. Prepare buffer solutions according to ISO 10523 with, for example, the following pH values: a) 4.0 ± 0.02; b) 7.0 ± 0.02. 6 Apparatus 6.1 Analytical balance Capable of weighing a mass of (0.500 ± 0.001) g of polymer powder in combination with the mass of the weighing vessel or laboratory paper employed. 6.2 Analytical balance Capable of weighing a mass of (9.00 ± 0.01) g of sodium chloride in combination with the mass of the weighing vessel or laboratory paper employed. 6.3 Analytical balance Capable of weighing a mass of (1000.00 ± 1.00) g of sodium chloride solutionin combination with the mass of the vessel employed. 6.4 pH meter Glass pH-responsive electrode (suitable for polymer solutions). 6.5 Magnetic stirrer and stirring bar Cylindrical stirring bars can be unstable when used on a multipoint magnetic stirring block. The mixture of magnetic fluxes can cause the bar to freeze periodically. Both cylindrical and star-shaped stirrers can tear the gel. lt is recommended to use a cross-centred circular bar (see Figure 1), which provides more stable stirring and minimum tearing of the gel. It is also important to make sure that the cross is properly centred in the circle. Cheaply made versions can be off‑centre and this increases variability in the test. 6.6 Graduated 250 ml beaker. Note: A tall form will give better separation of gel and saline. 6.7 Grade A 100 ml graduated measuring cylinder. 6.8 Grade A 1 l volumetric flask. 6.9 Weighing vessel or laboratory weighing paper. 6.10 Metal spatula To accommodate 0.5 g of superabsorbent powder. 7 Conditioning Samples shall be delivered in a closed container, to prevent absorption of atmospheric moisture. Allow the closed container to equilibrate to the laboratory conditions. The preferred test conditions are (23 ± 2) °C and (45 ± 15) % relative humidity. If these conditions are not available, test at ambient conditions and report the temperature and relative humidity. Measure these laboratory conditions in accordance with ISO 187. 8 Sampling WARNING - Powder Handling: The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) has provided a guideline value for long-term exposure to the respirable portion of superabsorbent polyacrylate dust of 0.05 mg/m3. The respirable portion is defined as those particles of less than 10 µm diameter. Commercial superabsorbent polymers typically contain less than 0.1 % of such particles. Precautions should be taken to avoid routine exposure to atmospheric respirable particles above this guideline value. 8.1 Before taking a test portion out of the container to run the test, rotate the container five to ten times in a three-dimensional figure of eight motion (see Figure 2), so as to obtain a homogeneous product. For that matter, sample bottles should not be filled more than 80 % of their nominal capacity.

Contents of GB/T 20405.1-2023