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The study aimed at the investigation of the effect of using three different vinyl-based polymers on
The mechanical properties of the formed composites.
The microstructure of the formed composites.
Preliminary bioactivity of the formed composites.
Aim of the work
Vinyl-based polymers PVA P(VA-co-VAc-co-It) P(VC-co-VAc-co-VA) [ CH 2 CH ] n OH CH 2 COOH [ CH 2 CH ] x [ CH 2 CH ] y [ CH 2 C ] z OH COOCH 3 COOH [ CH 2 CH ] x [ CH 2 CH ] y [ CH 2 CH ] z Cl COOCH 3 OH
1. Assessment of the starting materials (Plaster & polymers). 2. Formation of different polymer/plaster composites. 3. Measuring of the mechanical properties. 4. Correlation with the microstructure. 5. Studying of the bioactivity of gypsum and gypsum- polymer composites. Experimental Work
H 2 O and CO 2 were determined by weight loss at 240 and 1000 o C respectively.
XRF data of the tested plaster Physicomechanical properties of the tested plaster Trace 2.05 16.99 39.18 0.93 40.41 8.96 x10 3 0.43 Mol % Trace 1.54 5.28 53.55 0.64 38.53 0.02 0.44 Wt. % NaCl *CO 2 *H 2 O SO 3 MgO CaO R 2 O 3 SiO 2 Type 8.7±02 6.7±02 4.3±02 18.2±2 17.7±3 8.5±09 30’00” 26’30” 7 days 3 days one day 7 days 3 days one day Final Initial 46 Bending Strength (MPa) CompressiveStrength (MPa) Mechanical Properties Setting Time (min) Normal Consistency (%)
Neat plaster PVA/plaster 1.0 wt. % P(VA- co -VAc- co -It)/plaster 1.2 wt. % P(VC- co -VAc- co -VA)/plaster 4.0 wt. % 28.5 MPa (56 %) 23.2 MPa (27 %) 21.0 MPa (15 %) 18.2 MPa
Bioactivity of Gypsum and Gypsum-Polymer Composites Ca and P concentrations
Bioactivity of Gypsum and Gypsum-Polymer Composites Variations in the pH of SBF solutions
Bioactivity of Gypsum and Gypsum-Polymer Composites Neat plaster Gypsum after treatment in SBF followed by 1.5 SBF for a week (Low Magnification) Gypsum after treatment in SBF followed by 1.5 SBF for a week ( High Magnification ) Energy-dispersive x-ray analysis of the spot marked by X in micrograph (c).
The purity of the tested gypsum plaster sample was calculated to be around 96 % CaSO 4 .½H 2 O with small amount of siliceous materials and carbonates. The carbonates were calculated to be 1.34 % of MgCO 3 and 1.9 % of CaCO 3 .
The investigated gypsum plaster sample blended 46 % water and gave long setting time (30 min) with moderate mechanical properties, 8.7 and 18.2 MPa for bending and compressive strengths respectively.
PVA/plaster composites showed a 56% increase in the compressive strength achieving 28.5 MPa with the addition of only 1.0 % by weight of PVA.
The influence of addition of P(VA- co -VAc- co -It) to plaster at a slightly higher concentration; 1.2 wt. % showed a maximum compressive strength of 23.2 MPa, which is 27% higher than that of polymer-free gypsum.
P(VC- co -VAc- co -VA)/plaster composites achieved a compressive strength value of 21.0 MPa, which is 15% higher than that of polymer-free gypsum (when the polymer added in 4.0 wt. %).
Findings showed a correlation between the polymer solubility as well as its chemical structure with its effect on the mechanical properties of the produced composites.
Selected gypsum-polymer composites with the highest mechanical properties were further evaluated for their preliminary bioactivity. SEM micrographs of the SBF-treated composites revealed the formation of bone-like apatite deposits on the composite surfaces as well as inside the open pores. Water insoluble copolymer P(VC- co -VAc- co -VA) showed the greatest extent of apatite coating.
- Onderj Gedeon Doc.RNDr., Ph.D. - Ale š Helebrant Doc. Ing., CSc. - Jana Andertová Ing., CSc. - Jan Macháček Ing., Ph.D. - Dana Rohanová Dr. Ing. Acknowledgement