Networks reforming

On the other hand, water uptake is a continuous problem for polyimides and particularly for polynadimides [133]. Dynamic mechanical spectrometry (viscoelastic measurements) have been used to investigate the network degradations due to hydrolytic process [134]. It was shown on a special PMR resin (AFR 700 B) that network reformations are possible through post-curing. In addition, for fluorinated systems, 19F NMR can be used to follow the hydrolysis of the im-ide groups [135]. 

Gelatin, which is a convenient and pleasant term for the mixture of proteins and shorter peptides that are obtained from boiling byproducts of the meat and leather industries (mostly bones and pig skin), makes Jell-0 jiggly. The hydrogen bonds between peptide strands allows gelatin to form a network in the presence of water, which is what the physical structure of the gel is that you are familiar with. These hydrogen bonds can be disrupted with heat, which is why you boil Jell-0 before pouring it into a mold once it cools back down, the network reforms in whatever shape the liquid is in. 

Similar metallopolymers based on diphenylphosphine-terminated macromonomers in combination with Rh" or Ir ions resulted in the formation of gel-like networks when the building blocks were combined in a solvent such as dichloromethane or chloroform [91]. These gels could be liquehed upon ultrasonication (Fig. 27) as a result of ligand exchanges that preserved the coordination stoichiometry of the metal centers while reducing the number of cross-links. After sonication, the equilibrium network reformed almost immediately in the case of Rh" (gel phase after 1 h at -i-20°C), whereas the process was much slower in the case of the Ir -based gel (sol phase still present after 3 days at —20°C). 

If the silica network reforms quickly and is strong enough, tire adhesive or sealant will not sag during application and cure. The strengtii of the silica network is measured by its yield value, the force required to initiate flow in the adhesive or sealant. The higher the yield value, the greater the thickness of adhesive or sealant that can be applied before sagging occms. 

Thermoplastics are more suitable for recycling than elastomers or thermosetting polymers. Thermoplastics can be heated above their melting temperatures and then recast into new shapes. Elastomers and thermosets, on the other hand, have extensive cross-linking networks that must be destroyed and then reformed in the process of recycling. Processes that destroy cross-linking, however, generally break down the polymer beyond the point at which it can be easily reconstituted. 

The catalytic partial oxidation of methane for the production of synthesis gas is an interesting alternative to steam reforming which is currently practiced in industry [1]. Significant research efforts have been exerted worldwide in recent years to develop a viable process based on the partial oxidation route [2-9]. This process would offer many advantages over steam reforming, namely (a) the formation of a suitable H2/CO ratio for use in the Fischer-Tropsch synthesis network, (b) the requirement of less energy input due to its exothermic nature, (c) high activity and selectivity for synthesis gas formation. 

Regional networks of pyrolysis plants could be established to provide oil to a central steam reforming facility. The... 

Semi-gloss alkyd paint formulation, 18 6 It Semi-interpenetrating network (IPN) approaches, 10 436 Semi-IPN (interpenetrating polymer network) hydrogels, 13 733 Semikilled steels, 23 291 Semimoist pet foods, 10 849 Semipermanent cells, 14 228 Semiphorone, 14 583 Semiportable mri system, 23 860-861 Semiregenerative reforming operations, 25 166... 

The use of a p-vinylphenyl boronate as functional monomer to be covalently linked with a diol-template [2] is demonstrated in Fig. 2. Following polymerization in the presence of a cross-linker, the template has to be extracted from the polymer network. This requires breaking the covalent bond. During the application of covalently imprinted materials, the target molecules have to reform such bonds in order to be retained. Both making and breaking the bonds is at best a time-consuming process. 

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