Effects of boron compound on characteristics of poly(methyl methacrylate) and its nanocomposites

Göktaş, Müberra
In this work, composites of poly(methyl methacrylate) and benzene-1,4diboronic acid (BDBA) and their nanocomposites with organically modified montmorillonite OMMT prepared by solution and melt mixing, were characterized to study effects of boron content and the preparation method on the properties of PMMA. SEM images showed homogeneous dispersion of BDBA particles for the melt blended, whereas, agglomeration for the solution mixed PMMA/BDBA composites. XRD and TEM results of PMMA nanocomposites indicated that its nanocomposites prepared by both techniques were generally consisted of intercalated/exfoliated OMMT layers. Thermogravimetric analysis (TGA) and direct pyrolysis mass spectrometry (DPMS) indicated an increase in the thermal stability of the composites upon incorporation of boron and Cloisite 30B into PMMA matrix prepared by both techniques. This behavior was associated with generation of units by transesterification reactions between BDBA and PMMA. In addition, at high BDBA loadings, formation of a boron network structure was recorded for the composites prepared by solution casting technique. During the degradation of the PMMA nanocomposites with OMMT, the interactions between BDBA and ester groups of PMMA became more dominant than those among BDBA particles generating a boron network structure. Limiting oxygen index (LOI) and UL-94 vertical tests revealed no significant improvement in flammability characteristics for the composites. In addition, noticeable decrease in % elongation at break and tensile strength of PMMA was observed although stiffness of the polymer was slightly improved upon addition of BDBA and organoclay.