DEVELOPMENT OF STYRENE-METHYL METACRYLATE COPOLYMER MICROCAPSULES CONTAINING PHASE CHANGE MATERIALS
Chemical Product Design and Engineering (CPD&E)
Chemical Product Design & Engineering - I (CPD&E - 1)
Keywords: methyl methacrylate, styrene, suspension polymerization, microencapsulation, paraffin wax
Phase change materials (PCMs) are a series of functional materials with storing and releasing energy properties. Many companies and researchers have started to study PCMs and put them to use in lots of new and not so new fields such as solar energy storing, smart housing, thermo-regulated fibbers and so on. The paraffin waxes were used as PCMs because of its low cost, high energy storage density and large scale availability. To avoid liquid overflowing when using the process, microencapsulation is often employed to encapsulate PCMs as core using plastic or cross-linking polymers as shell. Although the PCM is the responsible of the storage and absorption or release of thermal energy the encapsulation of them inside a mechanically and physical-chemically stable shell is the main technical and scientific problem.
Up to now some attempts to develop a cheap and technically easy process for the microencapsulation of paraffin have been done. The development of easy, cheap and robust methods for the encapsulation of PCMs in suitable sized particles is very important for textile applications. The microencapsulation method developed in this work is simpler than other methods referenced in literature. In this work, we used a copolymerization process with styrene (St) and methylmetacrylate (MMA) to form the microcapsule’s shell.
To produce the microcapsules a mixture of St monomer, MMA monomer and benzoyl peroxide initiator was added into a continuous phase containing poly(vinylpirrolidone) and water. Thermal properties, morphology and particle size distribution of the microcapsules obtained were determined by DSC, SEM and laser diffraction, respectively.
The influence of paraffin/polymer ratio and MMA/St ratio on the encapsulation process was studied. The paraffin/polymer ratio has a critical influence on the encapsulation process itself, on the particle size distribution (PSD) and also on the morphology of the microcapsules obtained. If the amount of copolymer decreases or increases above or below a certain value, paraffin is difficultly encapsulated or not encapsulated at all by the copolymer. In the first case, there is not enough amount of monomer mixture to cover entirely all the surface of the paraffin drops. When a large proportion of monomer is employed the polymer trends to polymerize outside the bead in a segregated way. The final result is that only polymer particles without paraffin inside together with microcapsules containing paraffin wax are obtained.
The mass ratio of methyl MMA/St affects to the kinetics of the process and the PSD. As the amount of MMA increases, the reaction time decreases. This fact is due to the high reactivity of methyl methacrylate. As higher the mass ratio between MMA/St is the mean particle size decreases.
See the full pdf manuscript of the abstract.
Presented Wednesday 19, 11:30 to 11:48, in session Chemical Product Design & Engineering - I (CPD&E - 1).
