Textiles &Nbsp; Determination Of Ph Value Of Aqueous Extracts: Differences Between The Old And New Standards
China in recent years
Textile enterprises
More and more attention has been paid to the detection of pH value of textiles. The national mandatory standard GB 18401-2003 "national textile product basic safety technical specification" also takes pH value as an important safety performance index.
Standard GB/T 7573-2002, the determination of pH value of textile water extraction fluid has been unable to adapt to the development of textile detection after years of implementation. Therefore, the professional technical personnel of the textile Standardization Technical Committee Organization inspection organization has been revised and implemented in January 1, 2010.
The new standard has been modified and perfected on the basis of the old standard, and has become more reasonable and practical. It not only guarantees the advanced nature, scientificity and rationality of the technical content, but also facilitates the standardized operation of the testing organization and promotes the improvement of the product quality.
In order to better understand the new standard, this paper summarizes the modifications made by the new standard, and analyzes the differences between the two standards.
1 normative documents have been added and revised.
In the normative reference document of the new standard, "GB/T 6682" water specification and test method for analytical laboratories "has been added, and" GB/T6529 standard humidity for textile humidity control and test "has been cancelled.
Years of experience showed that the pH value of textiles did not need to be humidified. Conversely, the pretreatment of moisture could affect the detection results.
Therefore, the new standard has cancelled the operation process of "cutting the good samples in the first level standard atmosphere stipulated by GB/T6529".
2 reagents were added and modified.
The old standard stipulates that when the three grade water or ionic water is at (20 + 2) centigrade, the pH value ranges from 5 to 6.5, and the maximum conductivity is 2 x 10-6 s/cm.
Before use, boil 5 min to remove carbon dioxide and then seal down.
A large number of experiments have proved that the pH value and electrical conductivity of the three grade water or deionized water will be far beyond the original specified range before boiling.
Therefore, the new standard has been reamended, stipulates that distilled water or deionized water can satisfy at least GB/T 6682, three grade water requirements, that is, the pH value is between 5 and 7.5.
If the pH value is not within the prescribed limits, the glass instrument with stable chemical properties can be redistilled or other methods can be used to achieve the pH value of the water. It is not necessary to boil 5 min before use.
At the same time, the maximum electrical conductivity was eliminated.
New standard
An extraction medium of 0.1 mol/L potassium chloride solution and a buffer solution were added.
As the value of the pH value is larger than that of the test, the stability of the test results is poor. If the potassium chloride solution is added to the test solution, the stability of the indication can be effectively increased.
The new standard clearly stipulates this, so that the testing organization can add potassium chloride solution when testing textiles.
3 the extraction time and operation steps have been modified.
The old standard stipulates that the sample oscillates 1 h on the oscillating machine. The new standard stipulates that the 2H is oscillated on the mechanical oscillator, and the error is within 5 min.
The sample oscillating time is increased, so that the sample can be fully extracted.
The new standard combines the operation steps of the original Morton electrode system and the operation steps of the submerged electrode system, and eliminates the name of the Morton type electrode and the submerged electrode.
4 the calculation results indicate that the amendments have been made.
In the testing process, the old standard was required to record the pH value accurately to the nearest 0.1. The average value of the pH measured by second, third water extracts was the final result, and it was accurate to 0.05, which made the standards have contradictory problems in the accuracy of the results.
The new standard stipulates that if the difference between the two pH measurements is (accurate to 0.1) greater than 0.2, the other samples will be retested until the two effective measurements are obtained, and the average value is calculated, leaving a decimal result, which corresponds to the measured value of the standard mentioned above to 0.1 accurately.
5 addition and modification in other chapters
The new standard abolished the difference index section.
Old standards: as measured
PH value
If the difference is less than 3 or greater than 9, the difference index can be determined according to the standard method, and the difference index should not be greater than 1.
In the actual operation process, according to the old standard method to determine the difference index, the difference value is basically greater than 1.
Obviously, this provision is unreasonable. Therefore, the new standard has abolished the difference index, adding the precision section to make the standard more reasonable.
6 suggestions for new standards
After shredding the samples, especially the plush products, a lot of fine villi will be produced in the extractive fluid during the oscillation.
When testing, the fuzz in the extract will cause the indication to drift, which will affect the testing time and the authenticity of the test results.
Therefore, it is suggested that the filtration of the fuzz in the solution should be made to make the data more reliable.
Through the above analysis and comparison, it shows that the new standard can meet the needs of textile detection more accurately and reliably, so that textile enterprises can better control the quality of products and meet the requirements of consumers.
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