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Sustainable Composites
Published in Jitendra Kumar Katiyar, Mohammed Abdul Samad, Tribology in Sustainable Composites, 2023
Jitendra Kumar Katiyar, Mohammed Abdul Samad
Natural fiber reinforced composites are developed by using polymer as a matrix. The polymer is categorized into four groups: linear polymer (chain molecules), thermosetting polymer (highly cross-linked molecules), thermoplastic polymer (molecules not interconnected) and elastomer (thermoplastic or lightly cross-linked thermosets having elastic deformation > 200%). The crosslinking of molecules in polymers occurs due to the polymerization process. The degree of polymerization is equal to the number of monomer units in the chain. Among all types of polymers, only thermosetting and thermoplastic polymers are widely used for the manufacturing of nanocomposites. The methods are summarized in Table 1.3.
Fibres
Published in Ashok R. Khare, Principles of Spinning, 2021
During the process of manufacture of regenerated cellulose, special efforts are made to reduce DP to about 350 to make it soluble and ease the extrusion. It also controls the viscosity of the solution, thus minimizing mechanical difficulties during processing. It was found that the length of the cellulose molecule (DP), especially with cotton, is an important factor in deciding the physical properties of a fibre. In general, increasing degree of polymerization correlates with higher melting temperature and higher mechanical strength.
Mechanisms of Heterophase Polymerization
Published in Hugo Hernandez, Klaus Tauer, Heterophase Polymerization, 2021
The conversion of the polymerization reaction is also closely related (but not equivalent) to the degree of polymerization (DP). The degree of polymerization indicates the average number of monomer units incorporated to each polymer chain in the system (total number of polymerized monomer units divided by the total number of polymer chains). Note that for a single chain, the degree of polymerization corresponds to its chain length. As the conversion of the polymerization reaction increases, the degree of polymerization is also expected to increase. However, the relation between conversion and the degree of polymerization is not linear because the total number of chains (including monomer units) decreases during polymerization. Please notice that considering monomer units as polymer chains of chain length 1 has a significant effect on the determination of the degree of polymerization. Therefore, it is important to specify whether or not the monomer units are considered polymer chains in the determination of the degree of polymerization, and other properties of the polymer chain distribution.
Insight into the partial replacement of cement by ferronickel slags from New Caledonia
Published in European Journal of Environmental and Civil Engineering, 2022
Manal Bouasria, Laidi Babouri, Fouzia Khadraoui, Daniel Chateigner, Stéphanie Gascoin, Valérie Pralong, Mohammed-Hichem Benzaama, Beate Orberger, Yassine El Mendili
The Raman spectrum of amorphous silica is composed of broad peaks corresponding to the vibration modes of the Q1, Q2 and Q3 species present at 880, 940 and 1010 cm−1, respectively. The broad band at 595 cm−1 is assigned to the vibration twisting and stretching modes of the Si-O-Si bonds (Galeener, 1982; Matson et al., 1983; McMillan, 1984). Other contributions are present in the spectrum, such as the vibration mode at 675 cm−1 attributed to a poorly crystalline calcium-magnesium silicate (Deng et al., 2002; Martinez-Ramirez et al., 2006). The band at 750 cm−1 is assigned to Si–O stretching vibration with a dominant Si motion (Matson et al., 1983). The relative proportion of Q3/Q2 is high, indicating enhancement in the number of Q3 silicon sites and a high degree of polymerisation. This finding is important for using this material as a cement additive. The above described structure implies a higher degree of stiffness, strength and density of the silicate over time. In general, a higher degree of polymerisation in amorphous structures leads to higher compressive strengths (Ma et al., 2019; Wu et al., 2017). In addition, it is known that a magnesium-rich binder can lead to early strength development and durability of cementitious materials (Zhang et al., 2014).
Synthesis of amphiphilic hyperbranched polyglycerol through “thiol-ene” chemistry and its application on the removal of industrial dyes
Published in Chemical Engineering Communications, 2018
Qingwang Liu, Zhenzhong Fan, Baojun Bai, Jigang Wang, Lifeng Zhang, Ningning Zhan
The molecular weights of HPG samples are determined by GPC, and the results are shown in Table 1. It is observed that the number-average molecular weight () values of HPG samples in this work are varied from 2500 to 60,000. Generally, the sizes of polymers increase with the increasing degree of polymerization. The results of dynamic light scattering show that the Z-average size of DSHPG can be as high as 16.30 nm.