Condensation polymers interpenetrating polymer network

With controllable strength of the self- and hetero-associated hydrogen, a molecular level penetrated semi-interpenetrating polymer networks (semi-IPNs) of ST-VPDMS with poly(N-vinylpyrrolidone) (PVPr) were prepared by condensation of the self-associated silanols.13... 

Model reactions showed that the co-condensation reaction of melamine with phenolic resin occurs only by the reaction of phenolic methylol groups and the unsubstituted amino group at slightly acidic conditions. In contrast, a strong acidic or alkaline environment leads only to the formation of phenol methanal homocondensation products. The phenol reactivity in the reaction with methanal is low in comparison to the melamine reactivity in neutral and mildly acidic environments. An alkaline environment reverses this relative reactivity [99,100]. CiDsslinking of the products obtained by the reaction of 4-methylphenol and melamine with methanal appears to produce an interpenetrating polymer network [101]. 

A new convenient polymer modification has been developed to synthesize a series of novel silanol-containing polymers by a selective oxidation of Si—containing precursor polymers with a dimethyldioxirane solution in acetone. The silanol hydrogen bonding interactions in polymer blends as well as the silanol self-condensation to form siloxane semi-interpenetrating polymer networks in miscible polymer blends and organic-inorganic polymeric hybrids are discussed. 

Grigoryeva O, Fainleib A, Sergeeva LM. Thermoplastic polyurethane elastomers in interpenetrating polymer networks, in Handbook of Condensation Thermoplastic Elastomers , editor S Fakirov, WILEY-VCH, Germany, 2005, Chapter 12, p. 325-354. Nair CPR, Mathew D, Ninan KN. Advantages in cyanate ester resins. Adv. Polym. Sci., 155, 1-99 (2000). 

This indicates a simultaneous interpenetrating network, where Cn was formed by one reaction (say, addition), C22 was formed independently by another reaction (say, condensation), and the two networks are simultaneously polymerized. Without brackets a sequential synthesis of an interpenetrating polymer network is indicated ... 

The same principles that used to form a crosslinking network can be applied to IPN systems. For instance, IPN can be prepared initiating polymerization of a monomer in an existing polymer network. The first hydrogel network was composed of crosslinked poly(oxyethylene). The secondary polymerization was taken place in a mixture of acrylic acid, crosslinker and initiator with the poly(oxyeth-ylene) soaked in it, resulting in interpenetrating pH-sensitive networks of poly(oxyethylene) and PA A [64]. IPN can also be formed simultaneously using two different polymerizations mechanisms such as condensation and free radical polymerizations [65]. If linear polymer penetrate on a molecular scale of cross-linked polymer network, a semi-lPN is formed [66]. 

For a particular withdrawal speed, 170, the evaporation rate establishes the position of the drying line with respect to the reservoir surface (Xo in Figure 17) and thus the time scale. For reactive sols, a reduction in the evaporation rate provides more time for condensation reactions to occur, leading to stiffer networks that resist collapse by capillary forces. For colloidally stable sols (e.g., electrostatically stabilized SFB particles or highly esterified polymers), a reduction in the evaporation rate provides more time for ordering or interpenetration, leading to denser structures. 

Several mechanisms are needed to explain the action of the many different phosphorus compoimds used as FRs. Some of these compounds decompose in the condensed phase to form phosphoric acid or polyphosphoric acid. They can promote charring. Char formation is further enhanced by cellulosics, polyurethanes, phenolics, epoxy resins and EVA copolymers, and there are catalysts that promote it. Phenol-formaldehyde polymers can be used as flame retardants themselves when combined with a more flammable thermosetting polymer to form an interpenetrating network. 

The effect of the physisorbed material on reinforcement is much more difficult to predict and will probably depend very mnch on the system. In some cases this material will dissolve in the matrix and play little role in the interphase. In other cases it may penetrate a little way only and during processing and cure may react with the chemisorbed silane (through silane condensation or its reactive functionality), with itself, and with the matrix polymer. Under favourable circumstances then it could lead to an extensive interphase of an interpenetrating network type, with bonding to both filler and matrix. More often, however, reaction may only occnr with the matrix and not with the chemisorbed layers. This will give poor results. In the few stndies where the physisorbed material has been removed before use, properties have indeed been improved [65, 66]. 

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