Solid-state polycondensation (SSP) as a method to obtain high molecular
weight polymers. Part I. Parameters influencing the SSP process (in English)
Polimery 2013, No 1, 3
The paper is a literature review concerning the solid-state polycondensation (SSP) method. SSP is a competitive method of polymer synthesis to conventional melt polycondensation. The molecular weight of polymers obtained according to this method is exceptionally high and the polymer properties are also improved. In most cases the starting materials for SSP are in the form of flakes or powder. The process involves heating of the starting materials at the temperature between the glass transition temperature (Tg) and melting temperature of partially crystalline prepolymer (Tm). The reaction leading to an increase of molecular weight occurs between the chains terminal groups in the amorphous phase of semicrystalline polymer. The reaction equilibrium is shifted in favor of the formation of polymer due to by-products removing from the reaction system by inert gas flow or under vacuum. Due to the use of lower temperature than that usually applied in melt polycondensation, side reactions and thermal degradation of the product are limited. In addition, the process does not require complicated equipment and is environmentally friendly because no organic solvents are used. However, when the polymer contains larger amounts of by-products or a small extent of crystalline phase, sticking of the polymer particles can take place. In this case, the reaction proceeds not in solid but in melt phase, the contribution of the reactions between the terminal functional groups and the reactive groups of the middle part of polymer chains is much higher, which leads to higher degree of dispersity, but not to an increase in the polymer molecular weight. This paper presents the fundamentals of the SSP process and its advantages in comparison with other polycondensation methods. The kind of polymers that can be obtained with this method is described. In addition, the factors influencing the process and the properties of final products are discussed.