Interpenetrating polymer networks (IPN’s) are a unique type of polyblend, synthesized by swelling a crosslinked polymer (I) with a second monomer (II), together with crosslinking and activating agents, and polymerizing monomer II in situ (Sperling, 1974–1975 ; Sperling and Friedman, 1969). The term IPN was adopted because, in the limiting case of high compatibility between crosslinked polymers I and II, both networks could be visualized as being interpenetrating and continuous throughout the entire macroscopic sample.* As with other types of polyblends, if components I and II consist of chemically distinct polymers, incompatibility and some degree of phase separation usually result (Sperling, 1974–1975; Sperling and Friedman, 1969; Sperling et al., 1970a,b,c; 1971). Even under these conditions, the two components remain intimately mixed, the phase domain dimensions being on the order of hundreds of angstroms. If one polymer is elastomeric and one polymer is plastic at the use temperature, the combination tends to behave synergistically, and either reinforced rubber or impact-resistant plastics result, depending upon which phase predominates (Curtius et al., 1972; Sperling and Mihalakis, 1973; Sperling et al., 1971; Huelck et al., 1972). Among the other kinds of polymer blends discussed in this monograph, the graft-type copolymers are the ones most closely related to the IPN’s.

Interpenetrating Polymer Networks

Co-continuous structures can be regarded as the coexistence of at least two continuous structures within the same volume. Blends with co-continuous structures may combine the properties of both components in a favorable way, for example, mechanical moduli. This review article deals with the identification, characterization, and properties of co-continuous structures as well as with the development of co-continuous structures during the melt blending process. Co-continuous structures usually can be formed within a composition region about the phase inversion composition, which mainly depends on the viscosity ratio. On the other hand, co-continuous structures can be found independent of composition as intermediate stages during the initial state of morphology development and during phase inversion process in blends in which the component finally forming the dispersed phase forms the matrix in early mixing states. In addition, even at low volume fractions of one component, stable co-continuous morph...

Formation of Co-continuous Structures in Melt-Mixed Immiscible Polymer Blends

A semi-empirical expression for predicting phase continuity and inversion in polymer blends and simultaneous interpenetrating networks (SINs) was developed and examined experimentally. A rheological model based on the volume fraction, ϕ, and viscosity, η, led to the equation 






as the criteria for dual phase continuity for phases 1 and 2. This relation was evaluated for two systems: a castor oil polyester-urethane/polystyrene SIN, and a mechanical blend of polystyrene and polybutadiene. Literature data was also examined. A gradual phase inversion was found, with a region of dual phase continuity in between. While predictions of phase continuity were confirmed for the mechanical blends, they were not confirmed for the SIN system. This was probably due to rapid gelation at the point of phase inversion.

Phase continuity and inversion in polymer blends and simultaneous interpenetrating networks

On the mechanical properties of co-continuous polymer blends: experimental and modelling

Simultaneous interpenetrating polymer networks (IPNs) based on epoxy (diglycidyl ether of bisphenol A) and unsaturated polyester (UP) were prepared by using m-xylenediamine and benzoyl peroxide as curing agents. A single glass transition temperature for each IPN was observed with differential scanning calorimetry, which suggests good compatibility of epoxy and UP. This compatibility was further confirmed by the single damping peak of the rheometric dynamic spectroscopy. Curing behaviors were studied with dynamic differential scanning calorimetry, and the curing rates were measured with a Brookfield RTV viscometer. It was noted that an interlock between the two growing networks did exist and led to a retarded viscosity increase. However, the hydroxyl end groups in UP catalyzed the curing reaction of epoxy; in some IPNs where the hydroxyl concentration was high enough, such catalytic effect predominated the network interlock effect, leading to fast viscosity increases. In addition, the entanglement of the two interlocked networks played an important role in cracking energy absorption and reflected in a toughness improvement. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 585–592, 1999

https://ir.nctu.edu.tw:443/bitstream/11536/31391/1/000078961100015.pdf

Toughened interpenetrating polymer network materials based on unsaturated polyester and epoxy

The thermoplastic interpenetrating polymer networks (IPNs) are combinations of two physically crosslinked polymers. Thermoplastic IPNs were prepared by combining polymer I, an SEBS triblock elastomer with polymer II, an ionomer prepared from a random copolymer of styrene, methacrylic acid, and isoprene (90/10/1 by volume). Neutralization of the acid groups to form the ionomer was carried out on a Brabender Plasticorder. Two subclasses of the thermoplastic IPNs were identified. Chemically blended systems, prepared by a sequential polymerization method, were compared with compositionally equivalent mechanically blended systems prepared by melt blending the separately synthesized polymers. The chemically blended thermoplastic IPNs (CBT IPNs) exhibited lower melt viscosities than compositionally equivalent mechanically blended thermoplastic IPNs (MBT IPNs). Moreover, the melt viscosities of many of the CBT IPNs were even lower than that of either homopolymer component, leading to an explanation in terms of an unusually low value of the rubbery modulus front factor. Although both types of thermoplastic IPNs underwent a phase inversion during neutralization of polymer II, the phase inversions were often incomplete. Morphological studies revealed that more equal dual phase continuity existed in the MBT IPNs than in the CBT IPNs after ionomer formation.

Thermoplastic interpenetrating polymer networks of a triblock copolymer elastomer and an ionomeric plastic. I. Rheology and morphology

Thermoplastic interpenetrating polymer networks, IPN's, are defined as combinations of two physically crosslinked polymers. A styrene-b-ethylene-co-butylene-b-styrene (SEBS) triblock elastomer was combined with an ionomer prepared from a random copolymer of styrene, methacrylic acid, and isoprene (90/10/1 by volume), and subsequently neutralized. Two subclasses of the thermoplastic IPN's were identified. A sequential polymerization method yielded the chemically blended thermoplastic IPN's (CBT IPN's). Melt blending of the separately synthesized polymers produced the mechanically blended thermoplastic IPN's (MBT IPN's). Stress-strain and Rheovibron characterization revealed that the CBT IPN's exhibited greater tensile strength and higher elongation at break, but lower moduli than the MBT IPN materials of the same overall composition. Analysis of moduli data with the theories of Takayanagi, Davies, Budiansky, and Kerner disclosed more equal dual phase continuity for the MBT IPN's than the CBT IPN's at each composition. The low modulus of the more rubbery CBT IPN compositions was attributed to a decrease in the effective chain end-to-end distance between crosslinks in the elastomeric (EB) center block, brought about by the synthetic method.

Thermoplastic interpenetrating polymer networks of a triblock copolymer elastomer and an lonomeric plastic. II. Mechanical behavior

A Reexamination of Polystyrene/Polystyrene Homo Interpenetrating Polymer Networks: Aspects of Relative Network Continuity and Internetwork Coupling

A carboxylic elastomer based on butadiene, styrene, and methacrylic acid was polymerized and neutralized to form an ionomeric network I. Sequential IPNs were formed by synthesizing in situ polystyrene crosslinked with divinylbenzene as network II. Annealing studies were carried out, with and without reacidification, to ascertain the role played by ionic crosslinks in influencing morphology and mechanical behavior. Finally, the product is reneutralized, resulting in are arranged, relaxed structure. Ionic crosslinks in polymer I provide an in situ decrosslinking mechanism which permits molecular rearrangements to be induced. By annealing the material, a more cocontinuous phase morphology with concomitant modulus increases is attained. This investigation suggests an alternative method of inducing dual phase continuity in multipolymer combinations.

Interpenetrating polymer networks based on ionically crosslinked polymers: Reacidification and annealing as morphological variables

Sequential interpenetrating polymer networks, IPN’s, are synthesized by swelling a crosslinked polymer I with monomer II, plus crosslinking and activating agents, and polymerizing II in situ. The materials are called homo-IPN’s if polymers I and II are chemically identical.

Aspects of Relative Network Continuity and Physical Crosslinks Via an Analysis of Polystyrene/Polystyrene Homo-Interpenetrating Polymer Network Literature

D. L. Siegfried

Papers

Thermoplastic interpenetrating polymer networks of a triblock copolymer elastomer and an ionomeric plastic. I. Rheology and morphology

Thermoplastic interpenetrating polymer networks of a triblock copolymer elastomer and an lonomeric plastic. II. Mechanical behavior

A Reexamination of Polystyrene/Polystyrene Homo Interpenetrating Polymer Networks: Aspects of Relative Network Continuity and Internetwork Coupling

Interpenetrating polymer networks based on ionically crosslinked polymers: Reacidification and annealing as morphological variables

Aspects of Relative Network Continuity and Physical Crosslinks Via an Analysis of Polystyrene/Polystyrene Homo-Interpenetrating Polymer Network Literature