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Applications of Thermoplastic and Thermosetting Polymer Composites
Published in Sanjay Mavinkere Rangappa, Jyotishkumar Parameswaranpillai, Suchart Siengchin, Lothar Kroll, Lightweight Polymer Composite Structures, 2020
Sanjay Remanan, Sabyasachi Ghosh, Tushar Kanti Das, Narayan Chandra Das
Hence, material properties largely depend upon the chemical composition of the polymer chain. Highly rigid structures such as aromatic rings in the main chain decrease the flexibility but increase the high-temperature stability. Presence of -C ̶S- linkage increases the material flexibility but at the same time decreases the thermal stability. -Si ̶ O- bond in silicone polymer not only increases the high-temperature stability but also enhances the high material flexibility. Presence of polar groups can influence the dielectric and mechanical properties. Inter/intra-molecular crosslinking through the polar-polar interactions between the functional groups or hydrogen bonding can increase the material’s mechanical properties. The presence of pendant groups on both sides of the main chain increases the gas barrier properties and decreases the material crystallization. Increase in the pendant-group chain length can cause a more significant reduction in the degree of crystallization. This decrease in crystallization changes the polymer’s optical and gas barrier properties. Hence, tailoring of the chemical composition of the main chain and presence of pendant groups can significantly influence the final material properties.
Asphalt Chemistry: An NMR Investigation of the Benzylic Hydrogens and Oxidation
Published in Arthur M. Usmani, Asphalt Science and Technology, 1997
R. W. Jennings, Jacqueline Fonnesbeck, Jennifer Smith, J.A.S. Pribanic
Many commercial polymers contain polar groups that provide strong dipoledipole interactions between the chains. Ester groups, cyano groups, and halogens are common pendant groups. Linear nonpolar polymers, e.g., polyethylene, have only van der Waals attraction between the chains and hence must have relatively high molecular weight and must be closely packed to have useful mechanical properties.
Relationship between microstructure and performance of polypropylene fibre reinforced cement composites subjected to elevated temperature
Published in European Journal of Environmental and Civil Engineering, 2022
Soon Poh Yap, Yingxin Goh, Wan Xien Goh, Kim Hung Mo, Michael Yong Jing Liu, Hussein Adebayo Ibrahim
As observed from Figure 2, addition of PP fibres with any volume fraction produced insignificant effects on the wet densities of PP-reinforced mortars compared to the control mortar. This is due to its low specific gravity of 0.90 kg/m3 and low volume fraction were used. When higher volume fraction of 0.25% to 0.75% PP fibres were used, the wet density of fibre reinforced concrete can be reduced by 10–30% as presented by Yap et al. (2013). This is due the hydrophobic nature of PP fibre (Figure 3) which increased the permeable transition zone between fibre and cement paste which made it less dense compared to plain cement mortar. By observing the chemical structure of PP fibre, it has carbon-hydrogen bond, CH and CH2 groups along its backbone and a CH3 pendant group which made it a non-polar molecule from its chemical chain, [CnH2n]n. Thus, polar molecule (such as water molecule) tend to resist it due to its chemical inertness and a higher volume of PP fibres will result in density reduction.