We prepared biodegradable composite films of poly(vinyl alcohol) (PVA) and fly ash (FA) spanning 5, 10, 15, 20, and 25 wt % concentrations by casting aqueous solutions. The tensile strengths of the composite films were increased proportionally via the addition of FA. The strength of the film was enhanced by 193% with 20% FA compared to the neat PVA control. Further addition of FA deviated from the linear trend. The moduli of the composites also increased proportionally with FA addition to 212% at 20 wt % FA addition compared to the control. The percentage strain at break exponentially decreased with the addition of FA. In the dynamic mechanical behavior, the storage and loss moduli both increased with FA content. The tan d peaks corresponding to the glass-transition temperature shifted 5-10 C higher above the control sample (73 C). This shift was attributed to a reduction in the mobility of PVA segments because they were anchored by the FA surface. The reductions in mobility manifested in strong interfacial interactions were indicative of hydrogen bonding. Broadening and reduction in the intensities of the stretching and bending peaks of AOH, ACH and AC¼ ¼O of PVA in the Fourier transform infrared spectra were observed. This suggested that hydrogen bonding was active between the functional groups in the FA and PVA chains.
A study on nonisothermal crystallization kinetics in fly ash (FA) filled isotactic-polypropylene (PP) composites has revealed some interesting phenomena. Composites made by injection moulding of PP with 0, 20, 45, and 60 wt % of FA were nonisothermally studied using differential scanning calorimetry at cooling rates 10 C, 15 C, and 20 C per min from a melt temperature of 200 C cooled to À30 C. Whilst neat PP showed a mono modal a crystalline phase-only structure, presence of FA led to bimodal thermographs revealing partial transcrystallisation of a into b, to maximum 14%. The onset and peak crystallization temperatures of all samples decreased by $ 3 C with each 5 C/min increase in cooling rate. Parameters such as crystal growth rate, dimensions, and activation energy were determined using a series of established models. The Avrami graphs showed that contrary to the published data, there are two sets of straight lines (a) with a lower slope at low cooling rate and (b) with a distinctly higher slope for high cooling rate. Activation energy of the materials reached a maximum at 45% FA.
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