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2019/07/19

Technology | Tips for using some low molecular weight diols

Low molecular weight diols are multipurpose chemical raw materials. They can be used in polyester resin, polyurethane resin, unsaturated resin, polycarbonate and other synthetic materials, as well as in the synthesis of diacrylate, diglycidyl ether, plasticizer, lubricating oil, etc. The role of low molecular weight diols in polyurethane should not be underestimated. Although different low molecular weight diols have different properties, and after being made into polyester polyols, their properties in polyurethane products vary greatly. The mixed use of different low molecular weight diols will greatly help to improve the performance of polyester polyols. 1： Common low molecular weight diols include ethylene glycol (EG), 1,2-propanediol (1,2-PG), 1,3-butanediol, 1,4-butanediol (BDO, 1,6-hexanediol (HG), neopentyl glycol (NPG), diethylene glycol (DEG), methyl propylene glycol (MPO), dipropylene glycol (DPG), trimethylolpropane (TMP), etc. 2： Some low molecular weight diols mainly play a role in 1) The low molecular weight diols with symmetrical molecular structure include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, etc. The polyurethane products made from them have obvious crystallinity. 2) Low molecular diols with side chain in molecular structure include 1,2-propanediol, diethylene glycol (diethylene glycol), neopentyl glycol, methyl propylene glycol, 1,3-butanediol, 2,4-diethyl 1,5-pentanediol (diethylpentyl glycol DEPD for short), 2-butyl-2-ethyl-1,3-propanediol (BEPD, BEPG for short), octanediol (EHD), etc. Because of the existence of side groups, the polymer is not easy to crystallize and is relatively flexible; It has good hydrolysis resistance. 3： Some low molecular diols with side chain in molecular structure are characterized by the mixture of 1,2-propanediol and ethylene glycol, and the polyurethane resin obtained is amorphous; Diethylene glycol (diethylene glycol) can improve the flexibility of polyurethane adhesive. Dipropylene glycol can also improve the flexibility and corrosion resistance of polyurethane adhesive. Neopentyl glycol can improve the corrosion resistance of polyurethane adhesive, especially alkali resistance and hydrolysis resistance. The polyurethane resin synthesized from the above diols is too flexible, and is generally not used alone, but mixed with other corresponding diols. Methyl propylene glycol is the best substitute for neopentyl glycol, l, 6-hexanediol, etc., with a symmetrical molecular structure, but it is cheaper than neopentyl glycol and l, 6-hexanediol.

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2019/07/31

Type and Application of New Material Polyurethane Elastomer

PU elastomer, also known as polyurethane rubber, is a kind of elastomer polymer material containing more carbamate groups (- NHCOO -) in the molecular chain. It is usually prepared from oligomer polyol, polyisocyanate, chain extender/cross-linking agent and a small amount of additives. It is usually prepared from oligomer polyol, polyisocyanate, chain extender/cross-linking agent and a small amount of additives. Chain extender/crosslinking agent and a small amount of auxiliary agent are prepared.

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2019/08/13

Determination of isocyanate content

The quantitative determination methods of isocyanate include gravimetric method (dry method) and volumetric method (wet method). The principle of both methods is based on the reaction of primary amine or secondary amine with isocyanate to generate corresponding urea, and the reaction is carried out quantitatively under the condition of excessive amine.

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