Semi‐interpenetrating polymer networks based on polyurethane and polyvinylpyrrolidone. II. Dielectric relaxation and thermal behaviour

Semi‐interpenetrating polymer networks (semi‐IPNs) based on crosslinked polyurethane (PU) and linear polyvinylpyrrolidone (PVP) were synthezised, and their thermal and dynamic mechanical properties and dielectric relaxation behavior were studied to provide insight into their structure, especially according to their composition. The differential scanning calorimetry results showed the glass transitions of the pure components: one glass‐transition temperature (T_g) for PU and two transitions for PVP. Such glass transitions were also present in the semi‐IPNs, whatever their composition. The viscoelastic properties of the semi‐IPNs reflected their thermal behavior; it was shown that the semi‐IPNs presented three distinct dynamic mechanical relaxations related to these three T_g values. Although the temperature position of the PU maximum tan δ of the α‐relaxation was invariable, on the contrary the situation for the two maxima observed for PVP was more complex. Only the maximum of the highest temperature relaxation was shifted to lower temperatures with decreasing PVP content in the semi‐IPNs. In this study, we investigated the molecular mobility of the IPNs by means of dielectric relaxation spectroscopy; six relaxation processes were observed and indexed according the increase in the temperature range: the secondary β‐relaxations related to PU and PVP chains, an α‐relaxation due to the glass–rubber transition of the PU component, two α‐relaxations associated to the glass–rubber transitions of the PVP material, and an ionic conductivity relaxation due to the space charge polarization of PU. The temperature position of the α‐relaxation of PU was invariable in semi‐IPNs, as observed dynamic mechanical analysis measurements. However, the upper α‐relaxation process of PVP shifted to higher temperatures with increasing PVP content in the semi‐IPNs. We concluded that the investigated semi‐IPNs were two‐phase systems with incomplete phase separation and that the content of PVP in the IPNs governed the structure and corresponding properties of such systems through physical interactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1191–1201, 2003     

Main chain and segmental dynamics of semi interpenetrating polymer networks based on polyisoprene and poly(methyl methacrylate)

Main chain and segmental dynamics of polyisoprene (PI) and poly(methyl methacrylate) (PMMA) chains in semi IPNs were systematically studied over a wide range of temperatures (above and below T_g of both polymers) as a function of composition, crosslink density, and molecular weight. The immiscible polymers retained most of its characteristic molecular motion; however, the semi IPN synthesis resulted in dramatic changes in the motional behavior of both polymers due to the molecular level interpenetration between two polymer chains. ESR spin probe method was found to be sensitive to the concentration changes of PMMA in semi IPNs. Low temperature spectra showed the characteristics of rigid limit spectra, and in the range of 293-373 K, complex spectra were obtained with the slow component mostly arising out of the PMMA rich regions and fast component from the PI phase. We found that the rigid PMMA chains closely interpenetrated into the highly mobile PI network imparts motional restriction in nearby PI chains, and the highly mobile PI chains induce some degree of flexibility in highly rigid PMMA chains. Molecular level interchain mixing was found to be more efficient at a PMMA concentration of 35 wt.%. Moreover, the strong interphase formed in the above mentioned semi IPN contributed to the large slow component in the ESR spectra at higher temperature. The shape of the spectra along with the data obtained from the simulations of spectra was correlated to the morphology of the semi IPNs. The correlation time measurement detected the motional region associated with the glass transition of PI and PMMA, and these regions were found to follow the same pattern of shifts in α-relaxation of PI and PMMA observed in DMA analysis. Activation energies associated with the T_g regions were also calculated. T_50G was found to correlate with the T_g of PMMA, and the volume of polymer segments undergoing glass transitional motion was calculated to be 1.7 nm³. C-13 T_1ρ measurements of PMMA carbons indicate that the molecular level interactions were strong in semi IPN irrespective of the immiscible nature of polymers. The motional characteristics of H atoms attached to carbon atoms in both polymers were analyzed using 2D WISE NMR. Main relaxations of both components shifted inward, and both SEM and TEM analysis showed the development of a nanometer - sized morphology in the case of highly crosslinked semi IPN.     

Viscoelastic behaviour of epoxy resins modified with poly(methyl methacrylate)

The viscoelastic behaviour of a stoichiometric diglycidyl ether of bisphenol-A, (DGEBA), 4,4′-diaminodiphenylmethanes (DDM)s epoxy matrix modified with several amounts of poly(methyl methacrylate) (PMMA) has been studied by dynamic-mechanical analysis. Mixtures pre-cured at 80°C ranged from transparency to opacity as thermoplastic content changed from 5 to 15wt%. These changes have been attributed to variations in the ratio between polymerization rate and phase separation rate when PMMA content increased in the mixtures. When PMMA segregated from the epoxy matrix during curing, it had no influence on the crosslinking density of the epoxy phase. The clear decrease of temperature and activation energy of the β relaxation with respect to those values for the neat matrix, observed for the 5wt% PMMA-containing mixture but not for the 15wt% PMMA-containing one, are proposed to be a consequence of physical interactions between the PMMA chains and some epoxy oligomers. The dissimilar variation of the height of the ω relaxation with frequency when compared to that for the other relaxations studied, outlines the significance of physical factors influencing this relaxation. © 1998 Society of Chemical Industry     

Molecular demixing in poly[cross-(ethyl acrylete)]-inter-poly[cross-(methyl methacrylate)] interpenetrating polymer networks brought about by selective decrosslinking and annealing

The extent of molecular demixing of poly[cross-(ethyl acrylate)]-inter-poly[cross-(methyl methacrylate)] interpenetrating polymer networks (PEA/PMMA IPNs), of mid-range composition was investigated by decrosslinking and/or annealing using dynamic mechanical spectroscopy. A single broad transition characteristic of extensive but incomplete molecular mixing was observed for the PEA/PMMA IPN. The presence of crosslinking in both phases of an IPN enhances the mutual miscibility of the polymers. Through the use of a labile crosslinker, acrylic acid anhydride (AAA), polymer networks may be decross-linked, allowing the chains to separate and form two distinct phases. Annealing further sharpens the transitions, and phase separation becomes most pronounced when decrosslinking is followed by annealing.     

IPNs based on unsaturated polyester/epoxy: IV. Investigation on hydrogen bonding,compatability and interaction behavior

A series of interpenetrating polymer networks (IPNs) based on unsaturated polyester/epoxy have been developed. The compatibility and interaction behavior of these IPNs have been investigated by DMA, DSC, SEM, FTIR and solid‐state NMR spectroscopies. The glass transition temperatures of IPNs were decreased and their transitions became broader as the content of unsaturated polyester increased in IPNs, based on our DMA and DSC study. The results of FTIR indicate that hydrogen bonding is present between the unsaturated polyester and epoxy. Insufficient degree of hydrogen bonding brought about immiscibility between IPN components. The analysis of proton spin‐lattice relaxation time in the rotating frame of the IPNs was also utilized to investigate molecular interaction between unsaturated polyester and epoxy. From relaxation curves, phase separation was found for the IPN samples with unsaturated polyester content higher than 30 %. This corroborates the DMA and SEM study. Copyright © 2004 Society of Chemical Industry     

Semi‐ and full‐interpenetrating polymer networks based on polyurethane produced from canola oil and poly(methyl methacrylate)

Semi‐ and full‐interpenetrating polymer networks (IPNs) were prepared using polyurethane (PUR) produced from a canola oil‐based polyol with primary terminal functional groups and poly(methyl methacrylate) (PMMA). The properties of the material were studied and compared using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile measurements. The morphology of the IPNs was investigated using atomic force microscopy (AFM). Semi‐IPNs demonstrated different thermal mechanical properties, mechanical properties, phase behavior, and morphology from full IPNs. Both types of IPNs studied are two‐phase systems with incomplete phase separation. However, the extent of phase separation is significantly more advanced in the semi‐IPNs compared with the full IPNs. All the semi‐IPNs exhibited higher values of elongation at break for all proportions of acrylate to polyurethane compared with the corresponding full IPNs. These differences are mainly due to the fact that in the case of semi‐IPNs, one of the constituting polymers remains linear, so that it exhibits a loosely packed network and relatively high mobility, whereas in the case of full IPNs, there is a higher degree of crosslinking, which restricts the mobility of the chains. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Engineering properties of Novolac resin‐PMMA{poly(methyl methacrylate)} IPN system

Full and semi interpenetrating polymer networks (IPNs) based on phenol‐formaldehyde resin (Novolac) and poly(methyl methacrylate) have been made by in situ sequential technique of IPN formation. These systems of different compositions were characterized with respect to their mechanical properties, such as, ultimate tensile strength (UTS), percentage elongation at break, modulus, and toughness. Thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Extent of phase mixing of the two polymers was envisaged from the micrographs obtained by polarizing light microscopy (PLM). The effects of variation of the blend ratios on the above‐mentioned properties were examined. There was a decreasing trend of modulus and UTS with consequent increases in elongation at break and toughness for both types of IPNs with increase in proportions of PMMA. Lowering of glass transition temperatures (with respect to pure crosslinked Novolac resin) of the IPNs with increasing proportions of PMMA was observed, indicating a plasticizing influence of PMMA on the rigid and brittle matrix of phenolic resin. The TGA thermograms exhibit lowering in thermal stability of the IPNs with respect to pure phenolic resin in the regions of higher temperatures. With increase in proportion of PMMA the onset of degradation of the IPNs is shifted towards lower temperature zone. The surface morphology as revealed by PLM indicates distribution of discrete domains of PMMA in the phenolic resin matrix. The two phase interfaces are quite sharp at higher concentrations of PMMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2764–2774, 2004     

Thermomechanical properties and morphology of interpenetrating polymer networks of polyurethane–poly(methyl methacrylate)

Interpenetrating networks (IPNs) of polybutadiene‐based polyurethane (PU) and poly(methyl methacrylate) (PMMA) were synthesized. The effect of the incorporation of 2% glycidyl methacrylate (GMA) and 2‐hydroxyethyl methacrylate (2‐HEMA) on the thermal, mechanical, and morphological properties of IPNs was investigated. Both 2‐HEMA and GMA led to improvements in these properties. However, 2‐HEMA‐containing IPNs showed somewhat better tensile strength, elongation, and damping characteristics. The morphology of IPNs containing 2‐HEMA showed better mixing of the components. The improvement in the properties was observed for up to 40% PMMA in the IPNs. Differential scanning calorimetry thermograms showed the presence of three glass transitions. The third glass‐transition temperature was explained by possible grafting of methyl methacrylate onto PU. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1576–1585, 2002     

Synthesis and characterization of high performance,transparent interpenetrating polymer networks with polyurethane and poly(methyl methacrylate)

Transparent, interpenetrating polymer network (IPN) materials were synthesized using polyurethane (PU) and poly(methyl methacrylate) (PMMA). PMMA contributed to the transparency and rigidity necessary for use in impact‐resistant applications, whereas PU contributed to toughness. Several factors affecting the physical properties, such as the ratio of PU to PMMA, curing profile, inclusion of different isocyanates for the PU phase, and use of an inhibitor in the PMMA phase, were investigated. Full‐IPNs were synthesized so that the two polymer networks would remain entangled with one another, and domain sizes of each system were reduced, mitigating phase separation. Both simultaneous IPNs, polymerization of monomers occurring at the same time, and sequential IPNs, polymerization of monomers occurring at different temperatures, were synthesized for studying the reaction kinetics and final morphologies. The phase morphology and the final thermal and mechanical properties of the IPNs prepared were evaluated. Findings suggest that samples containing ～80 wt% PMMA, 1,6‐diisocyanatohexane 99+% (DCH), and an inhibitor with the MMA monomer created favorable results in the thermo‐mechanical and optical properties. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers     

Studies on engineering properties of PVC–PMMA semi‐interpenetrating polymer networks

Semi1 and semi2 interpenetrating polymer networks (IPNs) of PVC and in situ formed PMMA have been synthesized using diallyl phthalate and ethylene glycol dimethacrylate as the crosslinkers of PVC and PMMA, respectively. These two types of IPNs have been compared w.r.t their physical, mechanical, and thermal properties and an endeavor has been made to find a correlation of these properties with the morphology generated in these systems. The semi1 IPNs displayed a decrease in their mechanical parameters and the physical properties as well, while in contrast, the semi2 IPNs exhibited a marginal increase in the corresponding values after an initial drop upto about 15% of crosslinked PMMA incorporation when compared to the crosslinked PVC in the case of semi1 IPN and linear PVC in the case of semi2 IPN. The various samples of semi1 and semi2 IPNs showed a two‐stage degradation typical of PVC, while confirming the increased stability with the samples having higher percentages of PMMA. The influence of crosslinking of the major matrix in semi1 IPN was almost counterbalanced by the influence of crosslinking in the dispersed PMMA phase in the case of semi2 IPN. The softening characteristics as detected by the extent of penetration of the probe, as has been detected by thermomechanical analysis, are in conformity with their mechanicals. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1725–1735, 2005     

Rheological,mechanical, and morphological studies of epoxy/poly(methyl methacrylate) semi‐interpenetrating polymer networks

Semi‐interpenetrating polymer networks (semi‐IPNs) of epoxy resin and poly(methyl methacrylate) (PMMA) were synthesized. Methyl methacrylate (MMA) was polymerized by free radical mechanism with azo‐bis‐isobutyronitrile in the presence of oligomeric epoxy resin (DGEBA), and hexahydrophthalic anhydride as crosslinking agent. The gelation and vitrification transitions during cure/polymerization processes have been examined using parallel‐plates rheological technique. From differential scanning calorimetry and rheological techniques, it was suggested that both curing and polymerization processes occur simultaneously. However, the gelation time was longer for the semi‐IPN than those observed for the cure of pure DGEBA or polymerization of MMA. The gelation time increased significantly when 5% of MMA was employed, suggesting a diluent effect of the monomer. Higher amount of MMA resulted in a decrease of gel time, probably because of the simultaneous polymerization of MMA during the curing process. Structural examination of the semi‐IPNs, using scanning electron microscopy, revealed phase separation in nanoscale size for semi‐IPNs containing PMMA at concentrations up to 15%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Miscibility and thermal and dynamic mechanical behaviour of semi‐interpenetrating polymer networks based on polyurethane and poly(hydroxyethyl methacrylate)

The thermodynamic miscibility and thermal and dynamic mechanical behaviour of semi‐interpenetrating polymer networks (semi‐IPNs) of crosslinked polyurethane (PU) and linear poly(hydroxyethyl methacrylate) (PHEMA) have been investigated. The free energies of mixing of the semi‐IPN components have been determined by the vapour sorption method and it was established that the parameters are positive and depend on the amount of PHEMA in the semi‐IPN samples. Thermal analyses glass transition temperatures evidenced two in the semi‐IPNs in accordance with the investigation of the thermodynamic miscibility of these systems. Dynamic mechanical analysis revealed a pronounced change in the viscoelastic properties of the PU‐based semi‐IPNs with different amounts of PHEMA in the samples. The semi‐IPNs have two distinct tan δ maxima related to the relaxations of the two polymers in their glass temperature domains. The temperature position of PU relaxation maximum tan δ is invariable but its amplitude decreases in the semi‐IPNs with increasing amount of PHEMA in the systems. The tan δ maximum of PHEMA is shifted to a lower temperature and its amplitude decreases with increasing amount of PU in the semi‐IPNs. The segregation degree of components α was calculated using the viscoelastic properties of semi‐IPNs. It was concluded that the studied semi‐IPNs are two‐phase systems with incomplete phase separation. The different levels of immiscibility lead to the different degree of phase separation in the semi‐IPNs with compositions. Copyright © 2004 Society of Chemical Industry     

Studies on semi‐interpenetrating polymer network based on nitrile rubber and poly(methyl methacrylate)

Sequential interpenetrating polymer networks (IPNs) based on nitrile rubber and poly(methyl methacrylate) (PMMA) were synthesized. IPN compositions were varied by varying the swelling time. Two methods were adopted for making IPNs. The first method is “single‐step IPN” (SIPN) and the second method is “multistep IPN” (MIPN). The compositions were fixed around 90, 80, 70, 60 and 50% of NBR. In SIPN mode, swelling in monomer and subsequent curing was done once. In MIPN mode, swelling in monomer and curing was repeatedly done. Tensile strength of IPNs was found to increase with PMMA content, MIPN showing higher strength compared to SIPN. Dynamic modulus showed a similar trend. The tan δ value was found to decrease with PMMA content. At 62/38 nitrile rubber (NBR)/PMMA, MIPN composition isolated tan δ peaks appeared near glass transition temperatures of NBR and PMMA, respectively. Scanning electron micrograph showed phase‐separated morphology at the same MIPN composition. Solvent resistance increased with IPN formation maintaining higher resistance for MIPN compared to SIPN. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 354–360, 2004     

Behavior of polyoxyethylene‐containing interpenetrating polymer networks and their LiCLO4 complexes as phase transfer catalysts and ionic conductors

Simultaneous grafted interpenetrating polymer networks (IPNs) based on [castor oil–poly(ethylene glycol) (PEG)] polyurethane and poly(alkyl methacrylate) were synthesized by simultaneously coupling castor oil and PEG with 2,4‐toluene diisocyanate and by radical polymerization of alkyl methacrylate with castor oil. The gel content of the IPNs is ～96% in most cases. The IPNs were characterized by infrared spectroscopy. The effects of compositional variation of the IPNs on phase transfer catalytic efficiency and mechanical properties, and conductivity of the IPNs complexed with LiClO₄ were also studied. The results show that the IPNs have good phase transfer catalytic ability in the Williamson reaction and exhibit a maximum conversion of potassium phenolate at 55% polyoxyethylene (PEO). The phase transfer catalytic ability of the IPN increases with molecular weight of PEG used in the IPN synthesis and with the length of alkyl groups of the grafts, but decreases with increasing crosslinking degree. The complex of the IPNs with LiClO₄ exhibits good ionic conductivity at room temperature in the range 10^?5–3 × 10^?4 S/cm. This ionic conductivity decreases with increasing either the crosslinking degree or the molecular weight of PEG used, but increases with increasing PEO content. The more compatible are the grafts with PEO, the lower is the conductivity. Either butyl methacrylate or ethyl methacrylate is a good choice for the monomer in the synthesis of the IPNs for use as phase transfer catalysts and ion conducting materials. The IPNs showed high tensile strength in the range 10–20 MPa. The good mechanical properties of the IPNs favor their applications as a strong solid polymer electrolyte film and an easily recoverable phase transfer catalyst. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 830–836, 2003     

Irradiation effects on the relaxation behaviour of EPDM elastomers

γ‐irradiation of ethylene–propylene diene monomer (EPDM) elastomers under oxidant atmosphere was carried out in order to change their mechanical and dielectric behaviour. Three different formulations of EPDM (70 wt% ethylene, 28 wt% propylene; diene monomer: 2 wt% norbornene) were studied: a non‐crosslinked EPDM terpolymer, a crosslinked EPDM and a crosslinked EPDM stabilized with an antioxidant. Dielectric and mechanical relaxation show a β‐sub‐glass relaxation at about ?120 °C (1 Hz) and an α‐relaxation at ?15 °C (1 Hz) associated with the glass transition but influenced by the effects of irradiation. The local mobility associated with the β‐relaxation is only weakly influenced by γ‐irradiation up to 450 kGy. The α‐process is shifted to higher temperatures as a result of crosslinking and changes in the semicrystalline structure. The amplitude of the dielectric α‐process increases as a result of the formation of oxidized species during irradiation under oxygen. In contrast, the mechanical α‐relaxation amplitude decreases as a result of physical and chemical cross‐linking. It was shown that the main factors that determine the crosslinking/chain scission balance are (1) the presence of oxygen together with the irradiation dose, (2) the dose rate and (3) the initial crosslink density of the EPDM material. As a result, the individual contribution of crosslinking and crystallization, and therefore the understanding and prediction of the properties after γ‐irradiation can only be deduced after comparison of the polymer behaviour below and above its melting temperature. Copyright © 2004 Society of Chemical Industry     

Morphology and properties of polyurethane/poly(methyl methacrylate) interpenetrating polymer networks by Co60–γ ray

PU/PMMA IPNs were first synthesized using Co⁶⁰–γ radiation. The morphology, glass transition behavior, and mechanical properties of the formed IPNs have been studied by TEM, DSC, and electron tensile testing machine. The TEM micrographs and the results of DSC showed that Co⁶⁰–γ radiation was effective for obtaining small volume sizes of phase domains in IPNs. The structure with two continuous phases occurs in the content range of 40% to 70% PU. The ability of interpenetration enhanced with increasing the content of the crosslinking agents. The mechanical properties of IPNs reflected very good synergistic behavior.     

Semiinterpenetrating polymer networks based on polyurethane and polyvinylpyrrolidone. I. Thermodynamic state and dynamic mechanical analysis

Semiinterpenetrating polymer networks (semi‐IPNs) based on polyurethane (PU) and polyvinylpyrrolidone (PVP) have been synthesized, and their thermodynamic characteristics, thermal properties, and dynamical mechanical properties have been studied to have an insight in their structure as a function of their composition. First, the free energies of mixing of the two polymers in semi‐IPNs based on crosslinked PU and PVP have been determined by the vapor sorption method. It was established that these constituent polymers are not miscible in the semi‐IPNs. The differential scanning calorimetry results evidence the T_g of polyurethane and two T_g for PVP. The dynamic mechanical behavior of the semi‐IPNs has been investigated and is in accordance with their thermal behavior. It was shown that the semi‐IPNs present three distinct relaxations. If the temperature position of PU maximum tan δ is invariable, on the contrary, the situation for the two maxima observed for PVP is more complex. Only the maximum of the highest temperature relaxation is shifted to lower temperature with changing of the semi‐IPNs composition. It was concluded that investigated semi‐IPNs are two‐phase systems with incomplete phase separation. The phase composition was calculated using viscoelastic properties. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 852–862, 2001     

Effects of amorphous silica nanoparticles and polymer blend compositions on the structural,thermal and dielectric properties of PEO–PMMA blend based polymer nanocomposites

The polymer nanocomposite (PNC) films consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrices dispersed with nanoparticles of amorphous silica (SiO₂) have been prepared by solution-cast method followed by melt-press technique. Effects of SiO₂ concentration (x?=?0, 1, 3 and 5 wt%) and PEO–PMMA blend compositional ratios (PEO:PMMA?=?75:25, 50:50, and 25:75 wt%) on the surface morphology, crystalline phase, polymer-polymer and polymer-nanoparticle interactions, melting phase transition temperature, dielectric permittivity, electrical conductivity, electric modulus and the impedance properties of the PNC films have been investigated. The crystalline phase of the PNC films decreases with the increase of PMMA contents which also vary anomalously with the increase of SiO₂ concentration in the films. The melting phase transition temperature and polymer-nanoparticle interactions significantly change with the variation in the compositional ratio of the blend polymers in the PNC films. It is observed that the effect of SiO₂ on the dielectric and electrical properties of these PNCs vary greatly with change in the compositional ratio of PEO and PMMA in the blends. The dielectric relaxation process of these films confirm that the polymers cooperative chain segmental dynamics becomes significantly slow when merely 1 wt% SiO₂ nanoparticles are dispersed in the polymer blend matrix.     

Polyurethane–poly(methyl methacrylate) interpenetrating polymer networks. I. Synthesis,characterization, and preliminary blood compatibility studies

Simultaneous polyurethane–poly(methyl methacrylate) (PU–PMMA) interpenetrating polymer networks (IPNs) were synthesized with the PMMA polymerization initiated at room temperature. Transparent IPNs with better miscibility and synergism of mechanical properties were obtained. Dynamic mechanical analysis data indicated that up to 30% PMMA can be incorporated into PU networks without substantial phase separation. The PU–PMMA 90/10 IPNs elicit less than 2% hemolysis, suggesting that these materials could be used as blood contacting materials. © 1996 John Wiley & Sons, Inc.     

Dynamic mechanical properties and morphology of poly(benzyl methacrylate)/epoxy thermoset blends

Poly(benzyl methacrylate) (PBzMA)/epoxy thermoset blends of composition 5 to 25 wt% of PBzMA were prepared curing with 4,4′diaminodiphenylmethane (DDM), to study the influence of composition on the morphology and dynamic‐mechanical properties of the blends. The cured blends are phase separated in PBzMA‐rich phase and epoxy rich‐phase. As the PBzMA content increases, the morphology evolves from nodular, to combined and to totally inverted. The analysis of the α‐mechanical relaxations indicates that the glass transition temperatures (T_g) of PBzMA and of epoxy in the blends are different from the neat polymers, this is related to a noncomplete phase separation on curing. The profiles of the loss modulus‐temperature curves are correlated with the change in morphology that appears increasing the PBzMA content. The storage modulus‐temperature curves are highly dependent on the morphology of the samples. The storage modulus‐composition dependence is predicted using several models for two phase composites. POLYM. ENG. SCI., 50:1820–1830, 2010. © 2010 Society of Plastics Engineers