Sodium hypophosphite (NaH2PO2) CAS: 10039-56-2 mainly acts as a chain transfer agent or reducing agent in the synthesis process of water reducer (especially polycarboxylate water reducer), and its functions are as follows:

1. The role in the synthesis of polycarboxylate superplasticizer

(1) Chain transfer agent

In the radical copolymerization reaction (such as the synthesis of polycarboxylic acid superplasticizer), sodium hypophosphite regulates the molecular structure in the following ways:

-Control molecular weight: by terminating the growth of free radicals, prevent polymer molecular weight from being too large, so as to optimize the dispersibility and fluidity of water reducer.

-Improve molecular structure: help to form a more uniform branched structure, enhance the effect of water reducer on cement particles adsorption and dispersion.

(2) Reducing agent

In the REDOX triggering system (such as ammonium persulfate-sodium hypophosphite system):

-Form an oxidation-reduction pair with oxidants (such as persulfate) to reduce the activation energy of the reaction and promote the efficient polymerization of monomers (such as acrylic acid and polyether monomer) at room temperature or low temperature, saving energy.

2. Influence on the performance of water reducer

-Improve water reduction rate: by optimizing the molecular weight distribution of polymer, enhance the dispersion ability of cement particles.

-Reduce slump loss: a more uniform molecular structure helps to delay the consumption of water reducer in the early stage of cement hydration.

-Stability: reduce side reactions and improve the storage stability of water reducer solution.

3. Other potential effects

-Flame retardancy: the decomposition products of sodium hypophosphite may give the water reducer certain flame retardant properties (secondary effect).

-Environmental protection: compared with traditional chain transfer agents (such as thiols), sodium hypophosphite residues are more environmentally friendly.

Attention

-The mixing capacity should be accurate: excess may lead to low molecular weight, which weakens the effect of water reduction.

-Matching with monomer: it needs to be optimized in coordination with other synthetic raw materials (such as polyether macromonomer and initiator).

Sum up

Sodium hypophosphite is not directly used as a functional component in the water reducer, but a key additive in the synthesis process to improve the molecular structure and performance of the water reducer by regulating the polymerization reaction. This technology is particularly important in the production of high-performance polycarboxylate super plasticizer.