Interpenetrating polymer networks example

Over the years many blends of polyurethanes with other polymers have been prepared. One recent example is the blending of polyurethane intermediates with methyl methacrylate monomer and some unsaturated polyester resin. With a suitable balance of catalysts and initiators, addition and rearrangement reactions occur simultaneously but independently to give interpenetrating polymer networks. The use of the acrylic monomer lowers cost and viscosity whilst blends with 20% (MMA + polyester) have a superior impact strength. 

IPNs are found in many applications though this is not always recognised. For example conventional crosslinked polyester resins, where the polyester is unsaturated and crosslinks are formed by copolymerisation with styrene, is a material which falls within the definition of an interpenetrating polymer network. Experimental polymers for use as surface coatings have also been prepared from IPNs, such as epoxy-urethane-acrylic networks, and have been found to have promising properties. 

A substantial number of definitions in the terminology section are either of physical quantities or are expressed mathematically. In such cases, there are recommended symbols for the quantities and, when appropriate, corresponding SI units. Other terms have eommon abbreviations. The following format is used to indicate these essential eharaeteristics name of term (abbreviation), symbol, SI unit unit. Typical examples are tensile stress, interpenetrating polymer network (IPN). If there are any, alternative names or synonyms follow on the next line, and the definition on the sueeeeding lines. 

The examples summarized above are but indicative of the increasing body of evidence in support of the chemical bonding theory, and of the role of the silane organofunctional group in the formation of covalent bonds at the coupling agent/ matrix interphase by reaction or by co-polymerization with the formation of an interpenetrating polymer network. 

Simultaneous Mixing or Reacting. One of the advantages of the proposed nomenclature is the preservation of the time sequence of polymer reactions. Examples include grafting reactions and interpenetrating polymer networks. In some cases, like the blends or random copolymerization, the time sequence has no meaning. 

A random co-polymer or a blend of compatible polymers will have a single glass transition temperature intermediate between those of the two homopolymers. An example is shown in Figure 14 for nitrile-butadiene-rubber (22). The specific weight percents shown are those of commercial interest for NBR. In contrast, most polymer blends, graft and block copolymers, and interpenetrating polymer networks (IPN s) are phase separated (5) and exhibit two separate glass transitions from the two separate phases. Phase separated systems will not be considered here. 

One example utilizing conducting polymers showed that interpenetrating polymer networks (IPN) could be prepared using a hot pressing method to combine a polytetrahydrofuran network for mechanical resistance and a poly(ethylene oxide) (PEO) as a solid polymer electrolyte [46]. After interpenetration of two poly... 

When the process involves two competitive reactions, some people prrfer to call those modified polymers interpenetrated polymer networks (IPNs) [5]. The formation of a polyether-urethane network in a loosely crosslinked poly(methyl methacrylate) matrix to increase its toughness can serve as one of the examples. From a general point of view, the analysis of the reaction-induced phase separation is the same (perhaps more complex) for IPNs than for rubber-modified epoxies or for high-impact polystyrene. 

Within the thermodynamic framework proposed, only one reaction has been taken into account. But, generally, the modifier can also react with the matrix. Besides, the introduction of a second reaction quite different from the first one, for example chain and step reactions, is essential for modelling more complex systems like interpenetrating polymer networks. 

Interpenetrating polymer network varnishes are composed of the phenolic resin, an epoxy resin, flame retardants, for example brominated epoxies or acrylates, and triphenylphosphate, polymerization initiators for radical polymerization of the acrylates and curing accelerators to catalyze the reaction between epor groups and phenolic groups. 

Figure 3.4 gives another example of MTDSC output. In this case, data for an interpenetrating polymer network are reported. Obviously, it is very difficult to obtain the Tg values with any accuracy from the total heat flow signal, which is very complex. However, it is very easy, using the dCp/dT... 

L. H. Sperling, K. B. Ferguson, J. A. Manson, E. M. Corwin, and D. L. Siegfried, Isomeric Graft Copolymers and Interpenetrating Polymer Networks. Theory and Experiment, Macromolecules 9(5), 743 (1970). Application of ring theory concepts to IPN nomenclature. Decrosslinking of PS as example. 

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