Plasticizer refers to any substance added to the polymer system to increase the plasticity of the polymer system.
(1) According to the difference of compatibility
can be divided into main plasticizer and auxiliary plasticizer. The main plasticizer refers to a plasticizer that is fully compatible with the resin, or solvent-based plasticizer. Its molecules can not only enter the amorphous region of the resin molecular chain, but also enter the crystalline region of the molecular chain. Therefore, it will not ooze, bloom, etc., and can be used alone.
Auxiliary plasticizers are non-solvent plasticizers, generally cannot enter the crystallization area of the resin molecular chain, and can only be used in conjunction with the main plasticizer, so it is also called an extender.
75-80% of the total plasticizers are used in polyvinyl chloride plastics, mainly esters synthesized from fatty alcohols with carbon atoms of 6-11 and phthalic acids, the most important of which is phthalic acid Octyl ester (DOP) is a standard plasticizer. In addition, there are epoxy, phosphate and sebacate plasticizers and chlorinated paraffin extenders.
(2) According to the mode of action
can be divided into internal plasticizer and external plasticizer. Generally, the internal plasticizer is a second monomer added during the polymerization process to modify the polymer by copolymerization. For example, vinyl chloride-vinyl acetate copolymer is more flexible than vinyl chloride homopolymer. The advantage of internal plasticizer is excellent compatibility; the disadvantage is poor versatility and narrow temperature range.
External plasticizer, usually a liquid with a high boiling point or a low melting point solid, is added to the polymer that needs to be plasticized to increase the plasticity of the polymer. The external plasticizer does not chemically react with the polymer, and the interaction with the polymer is mainly the swelling effect at elevated temperature, forming a solid solution with the polymer. The advantages of internal plasticizers are comprehensive performance, easy production and use; disadvantages are poor compatibility.
(3) According to the chemical structure of the molecule
can be divided into monomer type and polymer type. Most plasticizers are monomeric, with fixed molecular weights, such as phthalate esters, fatty acid dibasic acid esters, etc., and monomeric plasticizers with variable molecular weights, such as epoxy soybean oil; Polyester (M is 1000-6000) obtained by polycondensation of dibasic acid and dibasic alcohol is a polymeric plasticizer.
Generally, the higher the water content of concrete, the better its fluidity and workability. But when concrete has enough moisture, the strength of concrete after solidification is inversely proportional to the moisture content. Therefore, if the concrete is to have high strength, the water content of the concrete should not be too much, and the T-addition property will become worse at this time.
The plasticizer can reduce the water content of the concrete without affecting the workability of the concrete (therefore it is called water reducing Agent), but also improve the strength of concrete. If Pozzolana pozzolan is added to the concrete, plasticizers will also be added to increase the strength. This method is often used to increase the strength when producing high-strength concrete or fiber reinforced concrete.