Network physical

The next level is the protocol that governs how the data are transmitted over the wire. Many protocols are ia use. A typical iastaHatioa may have multiple protocols mnning simultaneously on the same physical network. Vendors of network hardware and software develop protocols that are optimized for the type of appHcation for which their product is targeted. Among the protocols commonly seen ia a prepress aetwork are Apple Computer s AppleTalk and EtherTalk, and TCP/IP used by many UNIX work station vendors. The appHcation software a user employs automatically uses whatever protocol is necessary to move information over the network. 

Antony P., Bandyopadhyay S., and De S.K., Thermoplastic elastomers based on ionomeric polyblends of zinc salts of maleated polypropylene and maleated EPDM rubber, Polym. Eng. Sci., 39, 963, 1999. Weiss R.A., Sen A., Pottick L.A., and Willis C.L. Block copolymer ionomers. Thermoplastic elastomers possessing two distinct physical networks, Polym. Commun., 31, 220, 1990. 

Beyond the notion of physical networks in which flexible strands are connected by junctions, we will use the term physical gelation in the widest possible sense for polymeric systems which undergo liquid-solid transition due to any... 

Microphase separated systems are also known to yield a physical network which results in the self-similar relaxation pattern at an intermediate state... 

Recently, it was shown that polydimethylcarbosiloxanes with a small content of side carbonyl groups (PDMS-C) exhibit increasing viscosity and formation of a physical network at elevated temperatures [88,89], This was attributed to a rearrangement of intramolecular hydrogen bonds, which formed between the carboxyls during the synthesis and isolation of the polymers, forming intermolecular hydrogen bonds. 

W. Burchard and S.B. Ross-Murphy (Eds.), Physical Networks Polymers and Gels, Elsevier, London, 1990. 

Bokobza, L. Clement, F. Monnerie, L. Lapersonne, P. In Chemical and Physical Networks, Formation and Control Properties Nijenhuis, K., Mijs, W. J., Eds. The Wiley Polymer Networks Group Review Series, Wiley New York, 1998 Vol. 1, 321. 

Note 3 The term physical network may be used if the permanent paths through the structure of a network are not all formed by covalent bonds but, at least in part, by physical interactions, such that removal of the interactions leaves individual macromolecules or a macromolecule that is not a network. 

Rogovina LZ, Vasilev VG, Papkov VS, ShchegoUkhina OI, Slonimskii GL, Zhdanov AA. The peculiarities of physical network formation in carboxyl-containing polyfdimethylcarbo-siloxane). Mactomol Symp 1995 93 135-142. 

First step (a) represents the initial system - solution of the poly(acrylic acid) (urea and formaldehyde are not shown). Then, growing macromolecules of urea-formaldehyde polymer recognize matrix molecules and associate with them forming polycomplex. This process leads to physical network formation and gelation of the system (step b). Further process is accompanied by polycomplex formation to the total saturation of the template molecules by the urea-formaldehyde polymer (step c). Chemical crosslinking makes the polycomplex insoluble and non-separable into the components. In the final step (c), fibrilar structure can be formed by further polycondensation of excess of urea and formaldehyde. 

Physical Networks. Polymers and Gels Burchard, W. Ross-Murphy, S.B., Eds. Elsevier London, 1990. 

Chemical cross- linking reaction by GA could alter some properties of the material, besides the physical network formation between the constituent macromolecules. 

These results clearly indicate that the multi-frequency dynamic analysis method allows us to estimate the contribution of different relaxation mechanisms during curing of elastomers, and the changes in chemical and physical networks densities can be studied separately. 

Thermoplastic tri-block copolymers are interesting since they possess novel properties different from those of the homo- or copolymers. The thermoplastic elastomers have many of the physical properties of rubbers, i.e., softness, resilience, and flexibility. The unique properties of this kind of copolymer are due to the microphase separation of the hard crystalline domains dispersed in a continuous amorphous matrix (Fig. 6). Such phase morphology provides a physical network of flexible chains cross-linked by crystalline microdomains. The advantages over natural vulcanized rubbers are that thermoplastic elastomers are readily soluble in an appropriate solvent and can be processed as thermoplastics [109],... 

The physical network chain density (nent) was estimated from the comparison of the NMR and swelling results. A linear relationship of the nent in the NR system as a function of carbon black content exists. This result suggests that the physical adsorption plays a major role in the polymer-filler interactions. 

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