Modification of Polyvinyl Alcohol to Increase Resistance to Moisture in MDF Composites

abstract

English

A Macro defect free (MDF) composites are materials consisting of inorganic cement and organic polymer. These materials have extreme mechanical properties that far outperform other cementitious materials and can compete with both ceramic and metal materials. Their mechanical properties are given by the minimization of pores and macro defects in the material and at the same time by mechanical-chemical interactions between cement and polymer. However, it is the presence of the polymer phase that reduce the moisture resistance of MDF composites. The water molecules travel along the structure of the polymer chain to the internal structure of the MDF composite, where the polymer swells and the cement hydrates additionally. This creates internal stresses, secondary defects and loss of mechanical properties. This work aims to increase the resistance of MDF composites to moisture. This can be achieved by increasing the density of the polymer phase by crosslinking the polymer. Maleic anhydride was selected as the crosslinking agent and grafted onto the polyvinyl alcohol polymer chain (GOHSENOL KH-17) in various batches. The amount of grafted maleic anhydride was determined by UV-VIS spectrometry. The measured values were further verified by FTIR spectroscopy and XPS analysis, which confirmed the increasing amount of maleic anhydride in the polymer chain. The resistance of the prepared samples to moisture was analysed using rheology. When the polymeric films were prepared and left under the action of water for 24 hours. Subsequently, the viscosity of the aqueous medium was measured. The highest resistance to moisture was observed in the sample with the highest degree of grafted maleic anhydride. To determine the mechanical properties, test specimens containing aluminous cement, modified polyvinyl alcohol, water and glycerol were prepared by twin-roll mixer. Flexural tensile strength was measured after 7 days. Samples were stored in a dry environment, at 100% humidity and under water. Here, as expected, the highest strength was found for samples stored in a dry environment. The highest strengths (65 MPa) were achieved by test specimens prepared from polyvinyl alcohol grafted with 20% maleic anhydride. When stored in 100% humidity, the strengths decreased by a quarter and when stored in water decreased by almost two third.

MDF composites, macro-defect free, modification of polyvinyl alcohol

KOTRLA, J.; MÁSILKO, J.; ŠOUKAL, F.

26. 11. 2021

Vysoké učení technické v Brně, Fakulta chemická

Brno

978-80-214-6002-7

Studentská odborná konference CHEMIE JE ŽIVOT 2021 Sborník abstraktů

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81

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https://www.fch.vut.cz/vav/konference/sok/vystupy/sbornik-konference-2021-abstrakty-a5-pdf-p213391