Interpenetrating networks crosslinking

Covalently crosslinked Physically crosslinked Interpenetrating networks... 

So, the PVA/poly(sodium styrene sulphonate) [PSSNa] blend was obtained by casting aqueous solution of polymers mixture (PVA with Mw= 124,000-186,000 and HD=99% and PSSNa with Mw= 70,000). The resulted films were crosslinked with 1,2-dibromethane in gaseous phase. A semi-interpenetrating network (SIPN) in which polyelectrolyte (PSSNa) chains are trapped inside a based PVA network was obtained [44], A totally miscible blend with a very good film clarity and high mechanical resistance [44] resulted. 

The first type, termed sequential IPN s, involves the preparation of a crosslinked polymer I, a subsequent swelling of monomer II components and polymerization of the monomer II in situ. The second type of synthesis yields materials known as simultaneous interpenetrating networks (SIN s), involves the mixing of all components in an early stage, followed by the formation of both networks via independent reactions proceeding in the same container (10,11). One network can be formed by a chain growth mechanism and the other by a step growth mechanism. 

Simultaneous Interpenetrating Networks. An interpenetrating polymer network, IPN, can be defined as a combination of two polymers in network form, at least one of which was polymerized or synthesized in the presence of the other (23). These networks are synthesized sequentially in time. A simultaneous interpenetrating network, SIN, is an IPN in which both networks are synthesized simultaneously in time, or both monomers or prepolymers mixed prior to gelation. The two polymerizations are independent and non-interfering in an SIN, so that grafting or internetwork crosslinking is minimized (23-26). 

This is a theoretical study on the entanglement architecture and mechanical properties of an ideal two-component interpenetrating polymer network (IPN) composed of flexible chains (Fig. la). In this system molecular interaction between different polymer species is accomplished by the simultaneous or sequential polymerization of the polymeric precursors [1 ]. Chains which are thermodynamically incompatible are permanently interlocked in a composite network due to the presence of chemical crosslinks. The network structure is thus reinforced by chain entanglements trapped between permanent junctions [2,3]. It is evident that, entanglements between identical chains lie further apart in an IPN than in a one-component network (Fig. lb) and entanglements associating heterogeneous polymers are formed in between homopolymer junctions. In the present study the density of the various interchain associations in the composite network is evaluated as a function of the properties of the pure network components. This information is used to estimate the equilibrium rubber elasticity modulus of the IPN. 

Interpenetrating polymer networks are defined in their broadest sense as an intimate mixture of two or more pol)Mners in network form [1,2]. Ideally, they can be synthesized by either swelling the first crosslinked polymer with the second monomer and crosslinker, followed by in-situ polymerization of the second component (sequential IPN s) or by reacting a pair of monomers and crosslinkers at the same time through different, non-interfering reaction mechanisms, simultaneous interpenetrating networks, SIN s. In fact, many variations of these ideas exist in both the scientific and the patent literature. In any case, at least one of the two components must have a network structure, as an IPN prerequisite. ... 

Extensive research has been conducted and reviewed on interpenetrating polymer networks during the past decade (31-33). IPNs can be categorized into Semi-l-IPN and Semi-2-IPN. Semi-2-IPNs are those in which crosslinkable oligomers or materials are polymerized into the linear matrix. Semi-interpenetrating networks could have combined polymers that have same or different repeating units. 

Simultaneous interpenetrating networks (SIN s) are produced by running two essentially independent and noninterfering, crosslinking... 

IPN s and related materials) in fact) have a long history. For example) IPN s were first synthesized to produce smooth sheets of bulk polymerized homopolymers (11), IPN s were next used as solution polymerized ion exchange resins. (12) 13) Further development of IPN s included the syntheses oT interpenetrating elastomer networks (lEN s) and simultaneous interpenetrating networks (SIN s) (14). lEN s consist of a mixture of different emulsion polymerized elastomers which are both crosslinked after coagulation. SIN s are formed by the simultaneous polymerization of mixed monomers by two noninterfering reactions (3 ) 16). 

Sjmthesis of a linear polymer that is then trapped in a crosslinked network formed from a second component. Since only one polymer is crosslinked, this is a semi-interpenetrating network. This is also known as a tps iAo-interpenetrating network. 

In those years, Edison had switched from the cylinder-type phonograph records to the platter type. The latter ones were made of the new phenol-formaldehyde material, just invented by Leo Baekeland. The problem with the new material was that it was extremely biitfle, hence the new platters needed to be very thick. Aylsworth s solution to the problem was to mix in natural rubber and sulfur, which on heating forms a network. Since the phenol-formaldehyde compositions are all densely crosslinked, the overall composition was a simultaneous interpenetrating network. 

A commercial blend consisting of a thermoplastic polyamide (PA-6 or PA-66) and 5-25 wt% of a crosslinkable silicone, which forms a semi-interpenetrating network (semi-IPN) upon curing, has been offered under the trade name of Rim-... 

In order to use the stabilizing effect of a rather rigid crosslinked polymer in combination with a more flexible one we prepared interpenetrating networks (IPN) (see Table II). The best polymer in this row (P14) consisted of a mother polymer from 1 and glycol dimethacrylate with a relatively high inner pore volume. This unmodified polymer, after the removal of the template, showed a separation factor a = 2.68. This polymer was swollen with technical divinylbenzene and solvent and again polymerized. The second polymer was expected to... 

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