Simultaneous Interpenetrating Networks Research Articles

Synthesis and characterization of organic–inorganic hybrid composites from poly(acrylic acid)-[3-(trimethoxysilyl)propyl methacrylate]-Al2O3

Hybrid inorganic–organic materials are promising systems for a variety of applications due to their extraordinary properties from the combination of different building blocks. In this work, we present the synthesis and characterization of a hybrid material based on poly[acrylic acid] (PAA), 3-(trimethoxysilyl)propyl methacrylate (TMPM), and aluminum oxide (Al2O3). The synthesis was carried out using a two-step process: first, a polymerization via radical initiation, and subsequently, a sol–gel process. The hybrids were prepared by keeping constant the amount of acrylic acid and aluminum oxide precursor but changing the amount of TMPM. The physical and chemical properties of the hybrids were investigated using infrared spectroscopy (FT-IR), X-ray diffraction (XRD), N2 absorption (SBET), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results indicate that all of the materials were simultaneous interpenetrating networks (SIPNs) and that the morphologies and the properties depend on the amount of TMPM used. All materials showed good thermal stability, and the surface area of the composite decreased as more TMPM was incorporated in the network.

Approach to Ideal Simultaneous Interpenetrating Network Formation via Topological Cross-Links between Polyurethane and Polymethacrylate Network Polymer Precursors

The equimolar polyaddition cross-linking reaction of poly(methyl methacrylate-co-2-methacryloyloxyethyl isocyanate) with tri(oxytetramethylene) glycol leading to polyurethane (PU) networks was carried out in methyl benzoate at a 0.1 mol/L concentration of functional groups at 80 °C. Simultaneously, the free-radical cross-linking copolymerization of methyl methacrylate with tri(oxytetramethylene) dimethacrylate leading to polymethacrylate (PM) networks was progressed at a dilution of 1/10 in the presence of CBr4 as a chain transfer agent. The simultaneous interpenetrating networks (SINs) were formed via the topological cross-links between PU and PM network structures introduced by the respective intramolecular cross-linking reactions. Under the same polymerization conditions, no gelation was observed for respective cross-linking homopolymerizations leading to PU and PM homo-networks because respective intramolecular cross-linking reactions would be enhanced at a diluted solution. The topological cross-link...

Simultaneous interpenetrating networks consisting of polyurethane and graft vinyl ester resin: Effect of different radical initiators

AbstractA series of well‐defined graft vinyl ester resins (graft VER), composed of butanol side chain (BO) or poly(oxypropylene) side chains with different molecular weights (200 or 390), were synthesized and characterized. The simultaneous interpenetrating networks (SINs) of graft VER and polyurethane (PU) were prepared. The effect of initiators for graft VER on the morphologies and mechanical properties of PU/graft VER SINs was studied through DSC, SEM, and FTIR observations. For PU/graft VER SIN formed with AIBN as initiator, the morphology and structure of these SINs are mainly controlled by the PU network formed first, and the structure of graft VER has almost no influence on the long‐range order structure of hard segments in SIN. For PU/graft VER SIN prepared with BPO/DMA as initiator (redox system), the side‐chain structure of graft VER greatly affects the morphologies of these SINs, although the PU network and graft VER network formed almost simultaneously. The reinforcement effect of the graft VER network on the PU network is significantly different by using these two different initiators for graft VER, which could be related with the morphologies of SINs and the formation rate of the two networks. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1629–1636, 2002; DOI 10.1002/app.10502

Morphology and damping behavior of polyurethane/PMMA simultaneous interpenetrating networks

A series of polyurethane/PMMA simultaneous interpenetrating networks (SINs) with various hard segment contents (X) in the polyurethane phase (X = 15.5 to 36.5% in polyurethane) and wide range of polyurethane (PU) to polyacrylate (PA) ratio (PU/PA = 20:80 to 80:20) were prepared, and the damping and mechanical properties of these materials were studied. The damping of polyurethane soft phase was increased and shifted to lower temperature with increased content of PA vitreous phase. The mechanical properties were improved with increasing PA contents. The results show that PA and the polyurethane hard segment interaction play a special role in chain interpenetration density and its magnitude is revealed by the decreased dispersed domain size observed by scanning electron microscopy (SEM) and increased loss area as measured by dynamic mechanical thermal analysis (DMTA). When the weight ratio of PU/PA was 40:60, the resulting SIN materials possessed better damping properties, independent of X concentration.

Interpenetrating polymer networks of polyurethane and graft vinyl ester resin-polyurethane formed with diphenylmethane diisocyanate

For enhancing the compatibility and/or the interpenetration of the simultaneous interpenetrating networks (SINs) composed of polyurethane (PU) formed with uretonimine modified 4,4′-diphenylmethane diisocyanate and vinyl ester resin (VER), a series of graft VERs consisting of different lengths of side chains were synthesized and characterized. It was found that there exists some limited short-range order due to the strong hydrogen bonding in the graft VER network composed of butanol side chains (BO-g-VER). The graft VER network composed of poly(oxypropylene) (PPO) side chains (Mn: 200, 200-g-VER) showed compatible system, while the VER network consisting of longer PPO grafts (Mn: 390, 390-g-VER) exhibited microphase separated morphology. Based upon the DSC and FTIR measurements as well as the SEM and TEM observation, the lengths of side chains existing in graft VER network have great effect on the morphologies of PU/graft VER SINs. For PU/BO-g-VER SINs, there has been some interpenetration between the two networks because of the miscibility between the BO-g-VER network and the hard segments existing in the PU network. For PU/200-g-VER SINs, the good compatibility and/or the interpenetration between the two phases was observed, since the long-range ordered structure of hard segments in PU phase was greatly suppressed, resulting from the excellent miscibility between the urethane groups as well as the PPO side chains existing in the 200-g-VER network and those in the PU network, respectively. Thus, the strong reinforcement effect of these two graft networks on the PU network and the excellent mechanical properties of the SIN systems were observed. However, the PU/390-g-VER SINs showed the complicated morphologies because of existing microphase- separated morphology of 390-g-VER network in itself. In this case, the enhancement effect of such a graft VER network on the PU network is limited. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 136–144, 2000

Interpenetrating polymer networks of polyurethane and graft vinyl ester resin: polyurethane formed with toluene diisocyanate

For enhancing the compatibility and/or the interpenetration of the simultaneous interpenetrating networks (SINs) composed of polyurethane (PU) formed with toluene diisocyanates (TDI) and vinyl ester resin (VER) in which there were no chemical bonds between the two networks, a series of well-defined graft VERs consisting of different side chains were synthesized and characterized. The side chains existing in such graft VERs were formed from TDI and butanol (called BO-g-VER) or poly(oxypropylene) with different molecular weights ( M w: 200 and 390, called 200-g-VER and 390-g-VER, respectively). Differential scanning calorimetry measurements and the scanning electron microscopy observation indicated that the morphology of graft VERs had a great effect on the interpenetration and/or the compatibility between the two networks for PU/graft VER SIN systems. The SIN consisting of 200-g-VER exhibits excellent interpenetration between the two networks, as 200-g-VER network is a compatible system. For SIN composed of BO-g-VER, the compatibility between the two phases is greatly improved, since there are more content of urethane groups existing in grafts which should mix well with those in the PU network. Thus, the mechanical properties increase appreciably with the increase of graft VER content for these two SIN specimens. However, the reinforcement effect of 390-g-VER network on PU network is poor, as such a SIN shows a serious phase separation due to the micro-phase separated morphology of 390-g-VER network’s own self.

Graft interpenetrating polymer networks composed of epoxy resin and urethane acrylate resin

For enhancing the interpenetratoin and/or compatibility of the simultaneous interpenetrating networks (SINs) composed of epoxy resin (epoxy) and urethane acrylate resin (UAR), the graft epoxy consisting of different lengths of poly(oxypropylene) (PO) side chains were synthesized and characterized. It was found that the graft epoxy composed of short PO side chains [MW 480, epoxy-g-PO(480)] showed a compatible system while if consisting of longer PO grafts [MW 950, epoxy-g-PO(950)] exhibited a partial microphase separation morphology. DSC measurements as well as the SEM or TEM observation indicated that the interpenetration between the two phases for epoxy/UAR SINs including epoxy-g-PO(480) was improved appreciably due to the excellent miscibility between the PO grafts and PO segments existing in the graft epoxy and the UAR network, respectively. In this case, for SIN(80/20) containing 10 wt % of epoxy-g-PO(480) the tensile strength increases by a factor of 2.70 compared with that of pure epoxy network. However, the improvement of interpenetration and/or compatibility between the two networks as well as the mechanical properties for SINs composed of epoxy-g-PO(950) are limited resulting in the partial microphase separation of epoxy-g-PO(950) network's own self. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3568–3574, 1999

Synthesis and properties of simultaneous interpenetrating networks based on poly(urethane-epoxy)/allyl novolac resin

Poly (urethane-epoxy)/allyl novolac resin simultaneous interpenetrating networks (SINs) were prepared by crosslinking urethane-epoxy adduct with diamino diphenylmethane (DDM) and allyl novolac resin simultaneously. An urethane-epoxy adduct was synthesized by terminating the urethane prepolymer composed of 4,4′-diphenyl methane diisocyanate (MDI) and poly (tetramethylene oxide) (PTMO), whose molecular weight range falls in 600–700 (UT1), 900–1050 (UT2) and 1900–2100 (UT3) with glycidol (GL). The allyl novolac resin was derived from novolac type phenolic resin by substituting the hydroxy group on the aromatic ring with the allyl group. The thermal, mechanical and dynamical characteristics of these SINs were measured by differential scanning calorimetry (DSC), Instron tester and dynamical mechanical analysis (DMA), and correlated well enough with morphological observations from transmission electron microscopy (TEM). All these SINs exhibit a two-phase structure and a reasonable explanation is provided for the correspondence of the phase mixing and the specific mechanical properties.

Dynamic mechanical properties of interpenetrating polymer networks based on polyacrylates and epoxy

AbstractInterpenetrating polymer networks (IPNs) based on polyacrylate (poly(polyethylene glycol diacrylate), PEGDA) and epoxy(diglycidyl ether of bisphenol A, DGEBA) were prepared simultaneously. Dynamic mechanical properties of the SINs (simultaneous interpenetrating networks) with various compositions were studied. Enhanced mechanical properties were found in this case. From the point of view of pre‐swollen networks, all of the PEGDA/DGEBA IPNs were composed of the individual pre‐swollen networks. A micro‐phase segregation system was produced in the SIN. Glass transition temperatures shifted inward, which was attributed to molecular packing effects or mutual‐entanglements of molecular segments among the individual pre‐swollen networks. In accordance with the additivity of properties, namely the parallel model, the entanglement density between the two polymer networks reached its maximum at 50/50 PEGDA/DGEBA IPN.

Simultaneous interpenetrating networks of a polyurethane and poly([methyl methacrylate]-stat-[N,N-dimethylacrylamide

In a previous study, tetrahedron metastable phase diagrams were presented for a model simultaneous interpenetrating network (SIN) system of cross-polyurethane-inter-cross-poly(methyl methacrylate) (PU-PMMA). One triangular face of the overall tetrahedron diagram represented the ternary system MMA-PMMA-U, wherein U denotes the monomer/prepolymer mixture for the PU. In this article, a comonomer, N,N-dimethylacrylamide (DMA), is incorporated into the PMMA network. Thus, the above-mentioned ternary system is altered to A-PA-U, where A denotes the acrylic monomer mixture [MMA + DMA] and PA denotes the resulting copolymer. Glass transitions of fully cured samples were determined by dynamic mechanical spectroscopy (DMS). Phase separation was determined by the onset of turbidity, and gelation of the first gelling polymer was determined by the sudden resistance of the system to flow. The critical point, representing simultaneous phase separation and PA gelation, divides the overall composition for the reaction mixture (and the final SIN) into two parts. For one, gelation of the acrylic network precedes phase separation, and vice versa for the other part. In the absence of DMA in the PA network, the gelation-first region is very narrow, but with increasing amounts of copolymerized DMA, the critical point moves along the triangular face to increase the working area of the gelation-first region.

Mechanical and Dynamic Properties of Graft Polyurethane/Allyl Novolac Resin Simultaneous Interpenetrating Network

Two series of polyurethane (PU)/allyl novolac resin simultaneous interpenetrating networks (SINs) were synthesized. The PU components were prepared by reacting 4,4'-diphenyl methane diisocyanate with poly(tetramethylene oxide) (PTMO), whose molecular weight range was 600-700 (for convenience, this polymer was called UT1), 900-1050 (UT2) and 1900-2100 (UT3), respectively. The phenolic resin component was synthesized by substituting the hydroxy groups of the phenolic resin with the allyl group. To prove that the alkene group can be applied as a binding element between the networks to improve the network compatibility, trimethylol propane monoallyl ether (TMPME) with a double bond was chosen as the PU chain extender in one series of the PU/allyl novolac resin SINs (designated TUT1, TUT2 and TUT3 for different molecular weights of PTMO used as PU soft segments). After a detailed study of the thermal, mechanical, and dynamic properties and morphology, the extent of phase mixing of the graft PU/allyl novolac resin SINs (TUT series SINs) was significantly improved over that of UT series SINs. This result is consistent with the loss tangent shift in dynamic mechanical analysis measurements and with transmission electron microscope micrographs. The mechanical properties of the graft SINs (TUT series) were lower than those of the original SINs (UT series) because TMPME with bulky structure was used as the chain extender of PU.

Simultaneous interpenetrating networks of a polyurethane and poly(methyl methacrylate). II. Partitioning of MMA monomer in the last stages of polymerization

AbstractIn a model polyurethane/poly(methyl methacrylate) (PU/PMMA) system, the partitioning of unreacted methyl methacrylate monomer (MMA) is studied in the late stages of its polymerization, simulated by incorporating controlled amounts of MMA in otherwise fully cured simultaneous interpenetrating networks (SIN) samples. Glass transitions temperatures (Tg) were determined using dynamic mechanical spectroscopy and differential scanning calorimetry as a function of MMA content of the SINs. The lowering of Tg in each phase due to the plasticization effect of MMA is used to calculate a plasticization coefficient for each phase, finally allowing calculation of the partition coefficient of MMA between the two phases. It is found that the MMA monomer distributes itself almost uniformly across the two phases of the current SIN system, leading to speculation as to the locus of late SIN polymerization. © 1995 John Wiley & Sons, Inc.

Metastable phase diagrams for simultaneous interpenetrating networks of a polyurethane and poly(methyl methacrylate)

Phase separation and gelation in simultaneous interpenetrating networks (SINs) are studied for the model system polyurethane poly(methyl methacrylate) (PU-PMMA). A metastable phase diagram is developed as a tetrahedron in three dimensions in which the four vertices represent the four individual components: the two polymers, PMMA and PU, and the two monomer (or prepolymer) mixtures, MMA and ‘U’. The time order of three events, gelation of polymer I, gelation of polymer II and phase separation of polymer I from II, is explored. The tetrahedron constructed represents these three events as curved or planar surfaces going through its volume. The intersections of any two surfaces produce critical curves or lines representing, for example, simultaneous phase separation and PMMA gelation, or simultaneous gelation of PMMA and PU. These are critical conditions capable of playing key roles in the development of an SIN's morphology and hence properties. The metastable phase diagram allows visualization of the course of the three events during SIN synthesis, and provides direction for controlling them with respect to these critical conditions.

Organic-inorganic gels based on silica and multifunctional acrylates

Rigid, microporous silica rods, prepared previously by the sol-gel process, were infiltrated with three triacrylate monomers to give sequential interpenetrating networks (IPNs). The three commercially available triacrylate monomers are glycerol propoxy triacrylate (GPTA), trimethylolpropane triacrylate (TMPTA) and pentaerythritol triacrylate (PETA). Each solution containing a photoinitiator was allowed to infiltrate the silica rod, after which the sample was UV irradiated to polymerize the triacrylate monomer. Emphasis was placed on establishing the infiltration and polymerization conditions leading to optically transparent composites. For comparison, one of the triacrylates (GPTA) was introduced into a hydrolyzing sol-gel formulation containing TEOS, ethanol, water and acid catalyst, to effect a simultaneous IPN. The sequential IPN and the simultaneous IPN samples gave similar transmission curves, despite differences in skeletal density.

Fatigue behavior of acrylic interpenetrating polymer networks. II

AbstractEnergy‐absorbing simultaneous interpenetrating networks (SINs) based in polyether‐type polyurethanes (PUs) and poly(methyl methacrylate) (PMMA) networks were prepared by a prepolymer procedure. The products are translucent and appear to have single and broad glass transitions, suggesting some degree of phase separation. The percent energy absorption determined from dynamic properties and pendulum impact tests, the resistance to fatigue crack growth and fracture toughness (K1c) all increase with polyurethane content. The fracture behavior changes from brittle to ductile failure with increasing PU. The fatigue fracture surfaces of the SINs show extensive stress whitening associated with cavitation around the polyurethane domains, and localized shear deformation rather than crazing.

Reaction kinetics of polyurethane/polystyrene interpenetrating polymer networks by infra-red spectroscopy

The reaction kinetics of simultaneous interpenetrating networks (SIN) composed of polyurethane (PU) and polystyrene (PSt) were studied by infra-red spectroscopy. The effects of synthesis temperature, polyurethane/polystyrene composition, catalyst concentration, initiator concentration and amount of added divinylbenzene on the synthesis of the IPN were investigated. It was found that all of the components in the PU/PSt IPN system follow the Beer-Lambert law. The isocyanate, NCO, absorption band at 2280 cm −1 and the CC peak at 1645 cm −1 show a gradual decrease as the respective polymerizations proceed, and can be used to monitor the extent of reaction. The kinetic results obtained by spectroscopic analysis were in reasonable agreement with those obtained by chemical titration. It was found that the reactions of different components in the IPN followed their normal distinct reaction mechanisms and there was no interference between their reaction mechanisms. Increasing the PU/PSt proportion enhanced the rate of formation of PU and lessened the rate of formation of PSt. Changing the concentration of OcSn (AIBN) had an effect on the rate of formation of PU (PSt) and no effect on the rate of formation of PSt (PU). The rate of disappearance of double bonds in the IPN was increased by introducing a crosslinking agent for polystyrene, DVB. A theory for the cage effect of the PU network is proposed.

Correlation of mechanical property, crosslink density and thermogravimetric behavior of castor oil polyurethane–polystyrene divinyl benzene simultaneous IPN networks

AbstractSeveral simultaneous interpenetrating networks (IPN) of castor oil polyurethane (COPUN) and polystyrene divinyl benzene (PSN) were synthesized under conditions where the free radical polymerization of styrene and the crosslinking reaction of castor oil and toluene diisocyanate progress at comparable rates. Comparison of the mechanical properties and crosslink density of the COPUN and COPUN/PSN‐IPNs indicates a marginal increase in tensile strength and crosslink density from COPUN to 60COPUN/40 PSN IPN. IPN samples prepared with further increased PSN content show steady decrease in the above properties. This reversal of the expected trend was attributed to the possible greater molecular interpenetration achieved due to similar gelation times with resultant extension of chains and increase in free volume between crosslinks. This was further confirmed from thermogravimetric data on the initial stages of decomposition of the IPNs.

Phase continuity and inversion in polymer blends and simultaneous interpenetrating networks

AbstractA 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.

Reaction kinetics of polyurethane‐polyester interpenetrating polymer network in the bulk polymerization

AbstractKinetics of simultaneous interpenetrating networks (SIN) composed of a polyurethane resin (PU) and an unsaturated polyester resin was studied. A differential scanning calorimeter (DSC) was used to monitor the polymerization course. It was found that increasing the polyester content in a PU‐polyester SIN enhanced the polymerization of PU due to the “solvent effect” of polyester. On the other hand, increasing the PU content in the SIN retarded the polymerization of polyester due to the “cage effect” of PU. Polymerization sequence of the SIN could be controlled by employing different initiators for polyester reaction. The degree of crosslinking in each SIN component had a significant effect on the dynamics of the SIN formation and on the limiting conversion of the polyester reartion.

Dynamic mechanical properties of interpenetrating polymer networks formed by UV curing processes

Abstract Two-component interpenetrating polymer networks (IPN) were made by stepwise synthesis by UV-irradiated polymerization and heat curing. The mechanical properties of normal IPN, inverse IPN and SIN (simultaneous interpenetrating networks) prepared with acrylate and epoxy were studied. Unique mechanical properties were found in each case. All of these iPN systems were composed of the individual preswollen networks. A homogeneous system is produced in the inverse IPN and SIN, while a heterogeneous system is brought about in the normal IPN. Glass transition temperatures for the inverse IPN and the SIN are lower than the normal IPN, and are attributed to molecular packing effects.