Radiation crosslinking and liquid-liquid transitions in unsaturated polyestersReportar como inadecuado

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Polimeri : Plastics and Rubber Journal, Vol.30 No.4 April 2010. -

Ionizing radiation offers clean and easily regulated way of initiating polymerization and crosslinking reactions, independent of the reaction temperature but only very few methods can be used

for in-situ reaction monitoring. The advantages and limitations of electrical conductivity as a method for reaction monitoring are discussed on crosslinking of unsaturated polyester UP resin as an

example. The results are compared to non electrical methods like extraction analysis and differential scanning calorimetry DSC. The knowledge gathered over the years about the various aspects of

UP crosslinking by us and other authors is reviewed and reinterpreted according to newer approaches, taking into account not only the influence of microgel formation in various reaction conditions

but also reaction induced phase separation, its influence has been shown to depend on polyester composition. The importance of determining the extent of post-irradiation crosslinking that is

rarely studied is shown. The correct approach to interpretation of reaction conductivity data is presented and the need to avoid use of logarithms of original data if not based on a particular physical background is stressed. The application of electrical conductivity method to study of crosslinking of UP resins led to discovery of liquid-liquid transitions that were investigated in greater detail. In addition to viscometry and DSC, the structural background of those transition, the decrease of short-range or local order based on inter-and intramolecular hydrogen bonding was confirmed by spectroscopy, particularly near-infrared spectroscopy. The details on those transitions, mostly on less known upper liquid-liquid transition, that should be investigated in all polymers, especially those with lower glass transition temperature, are presented.

differential scanning calorimetry; electrical conductivity; extraction analysis; hydrogen bonding; liquid-liquid transitions microgels; near-infrared spectroscopy; post-irradiation crosslinking; radiation crosslinking; reaction-induced phase separation; unsaturated polyester resins

Autor: Irina PUCIĆ - orcid.org-0000-0002-5608-0658 ; Ruđer Bošković Institute, Zagreb

Fuente: http://hrcak.srce.hr/


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