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    Home > Coatings News > Paints and Coatings Market > The testing standard of amine value and the determination of sprayed (pure) polysaccharides for beijing-Shanghai high-speed railway

    The testing standard of amine value and the determination of sprayed (pure) polysaccharides for beijing-Shanghai high-speed railway

    • Last Update: 2020-11-28
    • Source: Internet
    • Author: User
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    0 Introduction
    Since the emergence of polyurethane technology in China in 1997, the domestic debate on polycetamol and polyurethane (polyurethane) has not stopped, so far there is no clear conclusion, but also the emergence of (pure) polysaccharide and other concepts. According to the official website of the U.S. PDA organization, the resin components of pure polyurethane must be made up of end amino resins and/or end amino chaining agents, must not contain any hydroxyl components and catalysts, but may contain additives to facilitate pigment dispersion, and polyurethane (yuan) hybrids can be composed of a mixture of end amino resins and end hydroxyl resins.
    In 2006, the Beijing-Tianjin high-speed railway used polyurethane (also known as hybrid) for waterproof construction, because this kind of products are China's first large-scale use on the railway, manufacturers and construction units are not rich enough experience, so there are many problems, such as After spraying the coating membrane pores are very many, winter construction of the coating film in the coming year after the temperature rise, the coating film large area and substrate separation, after spraying the coating film surface uneven, exposed coating film serious color change, powdering and so on . Therefore, in the Beijing-Shanghai high-speed railway used in polysaccharina coating performance has been greatly improved, while paying great attention to the treatment of concrete substrates, closure and other processes, strengthen the protection of exposed coating film, etc., and in August 2009 published the "Beijing-Shanghai high-speed railway bridge concrete bridge spray The temporary technical conditions for applying polypropyl sulfonium waterproof layer clearly define the division of polycyclic and semi-polypyrohydrate, and refer to the products of group B that contain only amino parts as (pure) polysaccharides, and the products containing hydroxyl parts in group B as polyurethane (polyurethane). Because of the difference in performance and price of polypyre and semi-polypyre, it is of great significance to identify it. To this end, according to our company since 2000 the development experience of polyurethane technology, a variety of raw materials for amine value detection, by measuring the amine value of polyyu B part and A part of the NCO value, the two will be associated to determine whether the material is (pure) polycetamol, or polyurethane (twice).
    1 amine detection methods and standards
    At present, the method of amine value detection in China has not yet issued a special standard to regulate, foreign methods for amine value detection have 3 standards are widely used: First, the United States ASTM D 6979 "the standard test method of polyurethane raw materials: polyol alkalinity determination", expressed as a percentage of nitrogen; The second is assTM D 2074-07 in the United States, "the alternate indicator method to determine the total amine value, beamine value, midamine value and uncleamine value of the test method", and the third is Japan's JIS K 7237-1995 "epoxy resin amino hardener total amine value test method." A comparison of these three criteria can be found in Table 1. By comparison, we used the JIS K 7237-1995 method to detect amine values. The specific detection methods are as follows.
    1.1 Overview of the test method
    Dissolve the sample in a mixture of acetic acid and phthalates, add crystalline amethyst as an indicator, and titrate with a solution of 0.1 mol/L perchloric acid acetic acid. The total amine value is calculated by consuming the volume of the perchloric acid solution.
    1.2 Detection Principle
    This method is that perchloric acid and amino react with the same mass, calculate the mass of ammonia by calculating the mass of the object consuming perchloric acid, and finally calculate the total amine value. The reaction principle is as follows:
    RNH2-HClO4 → RNH3ClO4
    R2NH-HClO4→ R2NH2ClO4
    3N-HClO4 → R3NHClO4
    1.3 Testing Process
    Take samples of 2 to 3 mmol amino equivalents with a beech cup, accurate to 0.1 mg, add 100 mL of adjacent nitrobenzene, acetate mixture solution (the volume ratio of the two is 9:2), use a magnetic mixer to fully stir to dissolve the sample, add 2 to 3 drops of crystalline purple indicator (in 10 Add 0.1 g crystalline acetic acetic acid to the 0.1 g crystalline acetic acetic solution that has been labeled and titration until the color of the test solution changes from blue to light green. It is best to test the same sample twice or more, and a blank test is required at the same time as titration.
    1.4 calculation method
    A× (V1-V2)×N)/m
    , A-allamine value (mgKOH/g);
    V1 - Acetic acid consumption perchloric acid at titration end point Dissolved liquid product (mL);
    V2 - blank test consumes perchloric acid acetic liquid product (mL);
    N - perchloric acid acetic acid solution molar concentration (mol/L);
    m - sample mass (g).Table
    1 3 standard comparisons for amine value determination
    Amine value detection data for various polyceramic raw materials
    The choice of raw materials for the high-speed rail polypropyl is not very large, and the amino compounds used are mainly as follows: D-2000, T-5000, DETDA, DMTDA, MOCA, W6200. Through the amine value detection, the specific data can be found in Table 2.
    can be known from Table 2: the difference between the detection amine value and the theoretical amine value is small, indicating that the amine value detection method used is reliable and can meet the requirements of the amine value detection of existing polypropylamine products.
    3 Polycyclic B histamine value detection data
    select our company's polyurethane waterproof paint, polyurethane waterproof coating and other polyurethane manufacturers to provide polycyclic materials for total amine value, NCO value detection, its detection data can be found in Table 3.
    compared with Appendix 4 of the Beijing-Shanghai High-Speed Railway Bridge Concrete Bridge Spray polysaccharide waterproof layer, which provides a total amine value of 175 to 210 mgKOH/g (detected using ASTM D6979 method). The author believes that the total amine value range proposed by this technical indicator is not appropriate, and it is more reasonable to change the upper limit to 225 mgKOH/g.
    4 The determination method of high-speed rail polyphoresium, hybrid polyphoresium
    In accordance with the "Beijing-Shanghai high-speed railway bridge concrete bridge surface spray polysaccharide waterproof layer temporary technical conditions" requirements, the Beijing-Shanghai high-speed railway using (pure) polyurethane waterproof coating B components do not contain any hydroxyl components, all using amino polyether or amino chain agent; The NCO value of part A can be calculated to be associated with the amine value of part B to determine whether the product is (pure) polypluoride. The principle of calculating the relationship between the NCO value of the A-part and the amine value of the B-part is as follows: the polycarbonal spray curing is carried out as a volume ratio of 1:1, and the mass ratio of the A and B-parts is determined to be M when it is cured; Between 1.05 and 1.08, set NCO index is f, for (pure) polyp is:
    100M g A part of the lively NCO mass of 100M×NCO value / 4 20 0
    100 g B parts of the active amine mass of 100×amine value / 56100
    100M g A parts and 100 g B parts are equal volume, so 100M g A The lively NCO quality of the part divided by the design NCO index, then get 100 g B part of the lively amine quality, that is:
    through a number of companies polyphospheric products density determination, the curing quality ratio is 1.1, that is, M to 1.1. In order to ensure the construction stability of polypropyl coating, assuming that the NCO index of its design is between 1.05 and 1.08, the relationship between the NCO value of polypropylent and the amine value can be obtained (see Table 4).
    Comparing the NCO and amine value data of the 4 companies tested, both conform to the above-mentioned amine value calculation method when the hypothetical NCO index is 1.05 to 1.08, that is, the measured amine value is within the reasonable amine value range mentioned above, so our (pure) polyphamide value calculation method is reliable.
    5 Conclusion
    Based on the above analysis, we believe that the use of JIS K 7237 standard for amine value detection is reliable, to meet the total amine value detection requirements of the Pyrethr B part. For a polyphammeric product, we determine whether the polycycline product is (pure) polyamine by measuring the NCO value of its A-part, the total amine value of the B-part, calculating the theoretical total amine value according to the calculation of the amine value, and calculating whether the total amine value is within the range of the theoretical total amine value.
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