Mortar plasticizers have been used in China since the 1960s. However, due to the limitations of construction specifications, the research on mortar plasticizers is not deep and systematic, and there is no consensus on some issues, but also due to China. There is no uniform quality standard and application technical regulations for mortar plasticizers, and the application of such products in engineering has gradually decreased. With the development of material technology, the performance of mortar plasticizer has been greatly improved, and the addition of mortar plasticizer to masonry mortar is the development direction.
The mortar plasticizer is added to the masonry mortar to improve the workability of the mortar. Instead of the lime paste in the cement-lime mixed mortar, it has certain significance for saving lime paste, which can solve the pollution of lime to the environment. Incorporating mortar plasticizer can save cement. At the same time, the use of mortar plasticizer can improve the water retention, fluidity and cohesiveness of the mortar, and overcome the shortcomings such as easy ash, large shrinkage and low strength of cement mixed mortar. Thereby ensuring the quality of the masonry. Therefore, the use of mortar plasticizers has significant socioeconomic benefits. Any substance added to a polymer system that increases the plasticity of the polymer system can be called a plasticizer. The main role of the plasticizer is to weaken the sub-valence between the polymer molecules, that is, van der Waals force, thereby increasing the mobility of the polymer molecular chain, reducing the crystallinity of the polymer molecular chain, that is, increasing the plasticity of the polymer. It appears that the hardness, modulus, softening temperature and embrittlement temperature of the polymer decrease, while elongation, flexibility and polymer increase.
Plasticizers can be divided into two major types according to their mode of action, namely internal plasticizers and external plasticizers. The internal plasticizer is actually part of the polymer. Typical internal plasticizers are the second monomers introduced during the polymerization of the polymer. Since the second monomer copolymer is in the molecular structure of the polymer, the degree of regularity of the polymer molecular chain is lowered, that is, the crystallinity of the polymer molecular chain is lowered. For example, vinyl chloride-vinyl acetate is more flexible than vinyl chloride homopolymer. The internal plasticizer has a relatively narrow temperature range and must be added during the polymerization, so that the internal plasticizer is used less.
The external plasticizer is a low molecular weight compound or polymer which is added to the polymer to be plasticized to increase the plasticity of the polymer. The external plasticizer is generally a high boiling point, a less volatile liquid or a low melting point solid, and most of which are ester organic compounds. Usually they do not chemically react with the polymer, and the interaction with the polymer is mainly the swelling at elevated temperatures, forming a solid solution with the polymer. The external plasticizer has comprehensive performance, is convenient to produce and use, and has wide application. Plasticizers are now generally referred to as external plasticizers.
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