Macro-defect free (MDF) cement is a cement-polymer composite with superior flexural strength although produced by mixing cement with small amounts of polymer and water. Special production technique and the crosslinking occurred between cement and polymer are important factors for obtaining such high strengths. However, MDFs lose considerable strength when exposed to water. The objective of this study was to explore the effects of TiO 2 addition on flexural strength and water sensitivity of MDF. In this study, MDF cements were produced by adding up to 4 % TiO 2 by weight of cement. Biaxial flexural test as well as Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR) tests were conducted in order to investigate the effect of TiO 2 addition. TiO 2 addition improved the water resistance of MDF cements in some batches, especially with 2 % addition possibly due to the C PVA -O-Ti-O-C PVA bond and this cross-linking mechanism together with C PVA -O-Al-O-C PVA bonds cause a more stable polymer network.
The mechanical behavior of microcellular open-cell foams prepared by a thermally induced phase separation process are investigated. The foams studied were prepared from isotactic polystyrene, polyacrylonitrile, and poly(4-methyl-1-pentene) (rigid foams), and polyurethane and Lycra (elastomeric foams). Their densities were in the range 0.04–0.27 g/cm3. Conventional polystyrene foams were used for comparison. The moduli and collapse stresses of these foams were measured in compression and compared with the current constitutive laws which relate mechanical properties to densities. A reinforcement technique based on the in-situ precipitation of silica was used to improve the mechanical properties.
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