Redispersible polymer powder (short for RDP) is a polymer powder with redispersible property. It is made from synthetic resin emulsion by adding other substances and then dried by spray. So it mainly contains polymer resin, additives, protective colloid, anti – caking agent.
The manufacturing processes can be divided into two procedures-The first step is to produce polymer emulsion by emulsion polymerization. The second step is to spray dry the mixture prepared by polymer emulsion to obtain polymer powder. The polymers during emulsion are thermoplastic and only become solid only when they fall below a critical temperature which is called vitrification temperature (Tg).
Nowadays, the main RDP used in the market are: vinyl acetate and ethylene copolymer latex powder (VAc/E), vinyl and vinyl chloride and lauric acid vinegar ternary copolymer latex powder (E/VC/VL), vinyl acetate and ethylene and higher fatty acid vinyl enzyme ternary copolymer latex powder (VAc/E/VeoVa). These three kinds may account for over than 80% in global market, while vinyl acetate-ethylene (VAE) occupy a leading position and represent the technical characteristics of redispersible latex powder. This may because-
1) It is one of the most used polymers in the world;
2) There is most application experience in the construction field;
3) It can meet all the requirements of mortar rheological properties, or workability in construction;
4) It has low organic volatile matter (VOC) and no pungent smell;
5) It has excellent UV resistance and good heat resistance and long-term stability;
6) It has a high saponification resistance (due to the unsaponification of ethylene);
7) It has widest range of glass temperature (Tg);
8) It has relatively good adhesion, flexibility and mechanical properties;
9) It has the properties of most stable product quality and the best storage stability;
10). It is quite easy to combine with protective colloid with excellent performance.
While using with other adhesives, filler materials, aggregates and additives to make dry mix mortar, under the co-function of hydrophilic protective colloid and mechanical shear, RDP particles can disperse into water very quickly. It can increase the gas content of mortar, so as to play a role of mortar lubrication, and during the protective colloid dispersing, water affinity and consistency will increase, which will be helpful to improve the cohesion and mortar workability.