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Characteristics of Polymers and Polymerization Processes
Published in Manas Chanda, Plastics Technology Handbook, 2017
Polyimides are synthesized [51] by the reactions of dianhydrides with diamines in a two-stage process (Figure 1.68). In the first stage, the two materials form an intermediate poly(amic acid). Processing is accomplished after this stage, since the polymer at this point is still soluble and fusible. The poly(amic acid) is formed into the desired physical form of the final polymer product (e.g., film, fiber, laminate, coating, etc.) and then the second stage of the reaction is carried out, in which the poly(amic acid) is cyclized in the solid state to the polyimide by heating at moderately high temperatures (above 150°C). The polymer after the second stage of the process is insoluble and infusible. Instead of m-phenylenediamine, shown in Figure 1.68, other diamines have also been used to synthesize polyimides—for example, p-phenylenediamine, p,p′-diaminodiphenyl ether, and p,p′-diaminodiphenyl sulfide.
Chemistry and Kinetics of Polyimide Formation
Published in Malay K. Ghosh, K. L. Mittal, Polyimides Fundamentals and Applications, 2018
James M. Sonnett, Thomas P. Gannett
Hodgkin [86] provided the first unambiguous evidence of electronic interaction between the nitrogen-containing moieties of a diamine during imide synthesis. When PPD was added to excess PMDA (the most reactive dianhydride) in DMF at 120°C, 76% of the PPD molecules reacted on only one end. In contrast, when the meta analog of PPD (m-phenylenediamine or MPD) was used, 85% of the diamine reacted at both ends. The trends reported by Hodgkin seem reasonable, but the reported degrees of imidization appear extraordinarily low.
Polymers
Published in Bryan Ellis, Ray Smith, Polymers, 2008
Synonyms: 2,2 -Bis(3,4-dicarboxyphenyl)hexafluoropropane dia- nhydride-co-m-phenylenediamine-co-p-phenylenediamine. Poly(5,5'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis-1,3- isobenzofurandione-co-m-phenylenediamine-co-p-phenylenediamine. Poly(4,4'-(hexafluoroisopropylidene)bis(phthalic anhydride)-co- m-phenylenediamine-co-p-phenylenediamine). Poly[(1,3-dihydro- 1,3-dioxo-2H-isoindole-2,5-diyl)[2,2,2-trifluoro-1-(trifluoromethy- l)ethylidene](1,3-dihydro-1,3-dioxo-2H-isoindole-5,2-diyl)pheny- lene]
Altering substrate properties of thin film nanocomposite membrane by Al2O3 nanoparticles for engineered osmosis process
Published in Environmental Technology, 2022
Zhen-Shen Liew, Yeek-Chia Ho, Woei Jye Lau, Nik Abdul Hadi Md Nordin, Soon-Onn Lai, Jun Ma
Polyethersulfone (PES) granules (Veradel® 3000P, Mw: 63,000 gmol−1) were purchased from Solvay Advanced Polymer, USA. N-methyl-2-pyrrolidone (NMP, > 99.5%) and hexane (>99.9%) were supplied by Merck, Germany. Polyethylene glycol 400 (PEG, Mw: 400 gmol−1) and calcium chloride (CaCl2, Mw: 110.98 gmol−1) were purchased from R&M Chemicals, UK. Aluminium oxide (Al2O3, particle size: < 50 nm), 1,3,5-benzene-tricarbonyl trichloride (TMC) and m-phenylenediamine (MPD) were obtained from Sigma Aldrich, USA. Sodium chloride (NaCl, Mw: 58.44 gmol−1) used in the preparation of feed and draw solution was purchased from R&M Chemicals. Deionised water (Milli-Q) with a resistivity of 18 MΩ was used throughout the experiments unless otherwise specified.
Effect of nano silver coating on thermal protective performance of firefighter protective clothing
Published in The Journal of The Textile Institute, 2019
Jawad Naeem, Adnan Mazari, Lukas Volesky, Funda Mazari
Nomex or conex is the trade name of meta-aramid. Aramid are the class of manufactured fiber, in which fiber forming substance is long chain synthetic polyamide, in which at least 85% of amide linkages are attached directly to two aromatic rings as mentioned by US Federal Trade Commission. In Nomex, the aromatic groups are all linked into backbone chain through 1 and 3 positions as shown in Figure 3. This is called meta-linkage. The density of meta-aramid is 1.35 g/cm3. It is heat resistant fiber having high proportion of meta-oriented phenyl rings. Moisture Regain is less than 5%. The decomposition temperature is around 425 °C. The reactants used for synthesis of meta-aramid are m-phenylenediamine and isophthalylol chloride. Limiting oxygen index lies between 28 and 31 (Anon, 2001).
Synthesis and characterization of Poly(p-phenylenediamine) and its derivatives using aluminium triflate as a co-catalyst
Published in Cogent Engineering, 2018
Unfortunately, the yields of P(dMe-pPD) and P(tMe-pPD) polymers were low compared to P(pPD) polymers obtained in this study and to poly(o-phenylenediamine), poly(m-phenylenediamine), poly(4,4ʹ-diaminodiphenylenemethane) and poly(benzidine) polymers obtained in our previous studies (Amer & Young, 2013; Amer et al., 2013, 2014). The low yield of P(dMe-pPD) and P(tMe-pPD) polymers probably resulted from steric hindrance of the methyl groups as explained above. Interestingly, however, P(pPD) polymer prepared using a mixture of Al(OTf)3 and ammonium persulfate as oxidant in water showed the highest yield (run 3 in Table 1). The fact that no monomer salts, which lower the polymerization yield, are formed by Al(OTf)3, as is the case with the application of protic acids, likely account for this finding (Amer & Young, 2013; Amer et al., 2013, 2014).