Interpenetrating polymer network from castor oil-based polyurethanes and poly(methyl methacrylate). XV

The polyurethanes have been prepared from 2.12 functional ? OH containing castor oil and diphenyl methane diisocyanate under identical experimental conditions with a varying NCO/OH ratio. These polyurethanes were swollen in methyl methacrylate and subsequently interpenetrated by free radical polymerization using benzoyl peroxide and crosslinker ethylene glycol dimethacrylate. A series of interpenetrating polymer network (IPN) PU/PMMA IPNs were obtained as films by a transfer moulding technique. These IPNs were characterized by their resistance to chemical reagents, thermal behavior, and mechanical properties. The morphology was shown by SEM and dielectric properties at different temperatures were measured.     

Interpenetrating polymer networks from polyurethanes and methacrylate polymers. II. Interpenetrating polymer networks with opposite charge groups

Interpenetrating polymer networks (IPNs) with opposite charge groups (tertiary amine and carboxyl groups) made from polyurethanes and methacrylate polymers have been synthesized and their properties and morphology, studied. With increasing carboxyl group concentration the mechanical properties and compatibility between the component networks were significantly improved, possibly because of the negative (or zero) free energy produced by the interaction contribution between the tertiary amine groups in the polyurethanes and the carboxyl groups in the methacrylate polymers determined by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The improved molecular mixing in these IPNs was thought to be due to the influence of the opposite charge groups in these systems.     

Interpenetrating polymer networks of poly(dimethyl siloxane–urethane) and poly(methyl methacrylate)

Simultaneous IPNs of poly(dimethyl siloxane-urethane) (PDMSU)/poly(methyl methacrylate) (PMMA) and related isomers have been prepared by using new oligomers of bis(β-hydroxyethoxymethyl)poly(dimethyl siloxane)s (PDMS diols) and new crosslinkers biuret triisocyanate (BTI) and tris(β-hydroxylethoxymethyl dimethylsiloxy) phenylsilane (Si-triol). Their phase morphology have been characterized by DSC and SEM. The SEM phase domain size is decreased by increasing crosslink density of the PDMSU network. A single phase IPN of PDMSU/PMMA can be made at an M_c = 1000 and 80 wt % of PDMSU. All of the pseudo- or semi-IPNs and blends of PDMSU and PMMA were phase separated with phase domain sizes ranging from 0.2 to several micrometers. The full IPNs of PDMSU/PMMA have better thermal resistance compared to the blends of linear PDMSU and linear PMMA. © 1993 John Wiley & Sons, Inc.     

Interpenetrating polymer networks of poly(carbonate-urethane) and polymethyl methacrylate

We report the synthesis and characterization of interpentrating polymer networks (IPN's), pseudo INPN's, and blends of urethane-containing aliphatic polycarbonates (PCU) and polymethyl methacrylate (PMMA). The simultaneous full IPN's of PCU's and PMMA over the whole composition range have only one T_g, as determined by DSC and DMA which, together with transmission electron microscopy observations, suggest a single phase morphology even though the linear chain blends are completely immiscible. The full IPN's exhibit a maximum tensile strength at a certain composition, and superior solvent and heat resistance as compared to the pseudo IPN's, linear blends, and the pure crosslinked PCU's and PMMA.     

Polyepichlorohydrin polyurethane/poly(methyl methacrylate) interpenetrating polymer networks

Polyurethane (PU) based on polyepichlorohydrin/poly(methyl methacrylate) (PECH/PMMA) interpenetrating polymer networks (IPNs) was synthesized by a simultaneous method. The effects of composition, hydroxyl group number of PECH, NCO/OH ratio and crosslinking agent content in IPNs were investigated in detail. Some other glycols, such as poly(ethylene glycol), poly(propylene glycol) and hydroxyl-terminated polybutadiene, were also used to obtain PU/PMMA IPNs. The interpenetrating and fracture behaviors of the IPNs are explained briefly.     

Interpenetrating polymer networks of poly(carbonate-urethane) and polystyrene

Simultaneous two-component interpenetrating polymer networks (IPN's), pseudo IPN's, and linear blends of urethane-containing aliphatic polycarbonate (PCU) and polystyrene (PS) have been synthesized and characterized. The simultaneous full IPN's of PCU and PS had one T_g only at compositions above 50 wt % PCU, as determined by DSC and DMA. The single phase morphology in the one T_g region was confirmed by transmission electron microscopy (TEM). However, the pseudo IPN's and linear blends of PCU and PS exhibited multiple (melting and glass) transitions by DSC measurements and phase separation was observed by TEM over the whole composition range. The full IPN's exhibited a maximum in ultimate mechanical properties at an intermediate composition. Superior solvent resistance as well as better thermal stability was shown by the IPN's as compared to the pseudo IPN's linear blends, and pure crosslinked components.     

Thermodynamic characterization of interpenetrating polymer networks of poly (carbonate-urethane) and poly (methyl methacrylate)

Crosslinked poly (methyl methacrylate) and poly (carbonate-urethane) as well as full interpenetrating network on their base (IPN) were characterized by precise heat capacity measurements in the temperature interval 1.2–150 K. As judged by the positive sign of the excess Gibbs free energy in the whole temperature interval above 30 K, the apparently single-phase state of IPN is thermodynamically unstable; however, its kinetic stability is ensured by permanent chamical crosslinks prohibiting the incipient phase separation. © 1994 John Wiley & Sons, Inc.     

Interpenetrating polymer networks of poly(2,6-dimethyl-1,4 phenylene oxide) and poly(urethane acrylate). I

Simultaneous full and pseudo- interpenetrating polymer networks of poly(2,6-dimethyl-1,4 phenylene oxide) (PPO) and a poly(urethane acrylate) (PUA) have been synthesized and characterized by differential scanning calorimetry, ultimate mechanical properties, and electron microscopy. No evidence of phase separation was detected in both the full and pseudo- PPO/PUA networks. The networks exhibited a single glass transition temperature at all the compositions studied. A maximum in tensile strength to break was observed at 25 PPO/75 PUA composition by weight percent.     

Interpenetrating polymer networks based on poly(chloroprene) and poly(carbonate-urethane)

Simultaneous interpenetrating polymer networks (SIN's) of poly(chloroprene) (CR) and poly(carbonate-urethane) (PCU) were prepared and characterized. The effect of composition on the phase morphology of full IPN's of CR/PCU has been studied by DSC and SEM. A single phase morphology of IPN's has achieved when the content of CR component is below 50 wt %. The microphase separation of the component networks in the IPN's occurred in samples whose weight percentage of the CR component was 50% and higher. © 1993 John Wiley & Sons, Inc.     

Interpenetrating polymer networks of poly(carbonate-urethane) and polyvinyl pyridine

Simultaneous interpenetrating polymer networks (IPN's), pseudo IPN's, and liner blends of aliphatic poly(carbonate-urethane) (PCU) and polyvinyl pyridine (PVP) have been prepared and characterized by DSC, DMA, and TEM. The full IPN's of PCU and PVP had a single phase morphology only above 50 wt % PCU, as determined by both DSC and DMA and confirmed by transmission electron microscopy (TEM). However, in both pseudo IPN's of PCU and PVP and in their linear blends there exist multiple glass transitions and melting points seen by DSC and DMA indicating phase incompatibility. The full IPN's exhibited superior ultimate mechanical properties and solvent resistance as compared to the pseudo IPN's, liner blends, and the pure crosslinked PCU and PVP networks.     

Characterization and degradation of poly(methylphenylsiloxane)–poly(methyl methacrylate) interpenetrating polymer networks

Poly(methylphenylsiloxane)–poly(methyl methacrylate) interpenetrating polymer networks (PMPS–PMMA IPNs) were prepared by in situ sequential condensation of poly(methylphenylsiloxane) with tetramethyl orthosilicate and polymerization of methyl methacrylate. PMPS–PMMA IPNs were characterized by infrared (IR), differential scanning calorimetry (DSC), and ²⁹Si and ¹³C nuclear magnetic resonance (NMR). The mobility of PMPS segments in IPNs, investigated by proton spin–spin relaxation T₂ measurements, is seriously restricted. The PMPS networks have influence on the average activation energy E_a,av of MMA segments in thermal degradation at initial conversion. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1717–1724, 1999     

Radical polymerization of methyl methacrylate in the presence of stereoregular poly(methyl methacrylate). V. Kinetics of initial template polymerization

The influence of stereoregular poly(methyl methacrylate) (PMMA) as a polymer matrix on the initial rate of radical polymerization of methyl methacrylate (MMA) has been measured between ?11 and +60°C using a dilatometric technique. Under proper conditions an increase in the relative initial rate of template polymerization with respect to a blank polymerization was observed. Viscometric studies showed that the observed effect could be related to the extent of complex formation between the polymer matrix and the growing chain radical. The initial rate was dependent on tacticity and molecular weight of the matrix polymer, solvent type and polymerization temperature. The accelerating effect was most pronounced (a fivefold increase in rate) at the lowest polymerization temperature with the highest molecular weight isotactic PMMA as a matrix in a solvent like dimethylformamide (DMF), which is known to be a good medium for complex formation between isotactic and syndiotactic PMMA. The acceleration of the polymerization below 25°C appeared to be accompanied by a large decrease in the overall energy and entropy of activation. It is suggested that the observed template effects are mainly due to the stereoselection in the propagation step (lower activation entropy Δ S_p^?) and the hindrance of segmental diffusion in the termination step (higher activation energy Δ E_t^?) of complexed growing chain radicals.     

Interpenetrating polymer networks based on polyurethane and poly(butyl methacrylate): Interrelation between reaction kinetics and microphase structure

The effect of the reaction kinetics on the formation of semi-IPNs based on crosslinked polyurethane and linear poly(butyl methacrylate) of various compositions has been studied. New data are presented concerning the interconnection between the reaction kinetics, gelation and rheokinetics of IPN formation, between kinetics and crosslinking density, microphase structure and degree of microphase separation. It was shown that kinetic factors determine the conditions of microphase separation and formation of microphase structure.     

Physico-mechanical, thermal and morphological behaviour of polyurethane/poly(methyl methacrylate) semi-interpenetrating polymer networks

Semi-interpenetrating polymer networks (SIPNs) of polyurethane (PU) and poly(methyl methacrylate) (PMMA) in different weight ratios viz., 90/10, 70/30, 60/40 and 50/50 were prepared. The SIPNs were characterized for physico-mechanical properties like density, tensile strength and elongation at break. Thermal stability of IPNs was measured using thermogravimetric analysis (TGA). From the TGA thermograms it was noticed that all IPNs are stable up to 325 °C and undergo three-step thermal degradation in the temperature ranges 251-400, 378-508 and 445-645 °C for first, second and third steps, respectively. Thermal degradation kinetic parameters like activation energy (E_a) were calculated using Broido, Coats-Redfern and Horowitz-Metzger models. The values obtained by Broido and Horowitz-Metzger methods showed concurrency, whereas Coats-Redfern method showed relatively lower values. Surface morphology measured using scanning electron microscope (SEM) showed two-phase morphology for all the IPNs.     

Three-component interpenetrating polymer networks (IPN's) from polyurethanes,epoxies, and poly(methacrylates)

Three-component IPN systems made from polyurethanes, epoxies, and poly(methacrylates) containing charge groups in the backbones of the constituent networks have been prepared. Specific attractive forces that occurred among the various networks helped to compatibilize them and aided in the formation of true homogeneous topologically interpenetrating polymer networks. These three-component polymer alloys, including full-IPN's, pseudo-IPN's, and graft-IPN's, were characterized by means of mechanical spectroscopy, electron microscopy, and stress–strain properties. In addition, some adhesion studies were carried out (lap shear strength and peel strength). A comparison of the different types of three-component polymer alloys showed that better properties were generally exhibited by the graft-IPN's and full-IPN's containing opposite charge groups.     

Vibration damping materials based on interpenetrating polymer networks of carboxylated nitrile rubber and poly(methyl methacrylate)

Interpenetrating polymer networks (IPNs) based on carboxylated nitrile rubber (XNBR) and poly(methyl methacrylate)s were synthesized. Crosslinked XNBR was swollen in methyl methacrylate containing benzoyl peroxide as initiator and tetraethylene glycol dimethacrylate as crosslinking agent. The compositions of the IPNs were varied by changing the swelling time of the rubber in the methacrylate monomer. The dynamic mechanical properties of the IPNs were studied. The dynamic mechanical properties in the range 1–10⁵ Hz were obtained by the time‐temperature superposition of the data under multifrequency mode, which indicated high tan δ with good storage modulus in the entire frequency range. This indicates the suitability of these IPNs as vibration and acoustic dampers. Copyright © 2002 John Wiley & Sons, Ltd.     

Poly(ethylene oxide)/poly(methyl methacrylate) (semi-)interpenetrating polymer networks: Synthesis and phase diagrams

Interpenetrating polymer networks (IPNs) of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) were prepared by simultaneous network formation. The PEO network was produced by acid-catlayzed self-condensation of α,ω-bis(triethoxysilane)-terminated PEO in the presence of small amounts of water. The PMMA network was formed by free radical polymerization of MAA in the presence of divinylbenzene as crosslinker. The reaction conditions were adjusted to obtain similar crosslinking kinetics for both reactions. An attempt was made to construct a phase diagram of the IPNs by measuring the composition of the IPNs at the moment of the appearance of the phase separation, as indicated by the onset of turbidity. This composition could be determined because the siloxane crosslinks of the PEO network could be hydrolyzed in aqueous NaOH with the formation of linear, soluble PEO chains. The phase diagram was compared with phase diagrams of blends of linear polymers and of semi-IPNs (crosslinked PMMA and linear PEO), obtained under similar conditions, i.e. polymerization of MMA in the presence of varying amounts of PEO. It was observed that the form of the phase diagrams of the linear polymers is similar to that of the IPNs, but is quite different from that of the semi-IPNs. Thus, homogeneous transparent materials containing up to 60% of PEO could be prepared in the blends and the IPNs, but in the semi-IPNs, phase separation occurred with PEO contents as low as 10%.     

The transparency of polyurethane-poly(methyl methacrylate) interpenetrating and semi-interpenetrating polymer networks

Various combinations of polyurethane (PUR) and poly(methyl methacrylate) (PMMA) were prepared as interpenetrating polymer networks (IPN) or semi-IPNs. In the latter, either the PUR or the PMMA component was crosslinked. The optical transmissions of these materials were measured as a function of the crosslink degrees of both phases. The role of the PUR chain extender, poly(oxypropylene) glycol, is discussed. It is concluded that any means which increases the degree of phase dispersion favours the transparency of PUR/PMMA based IPNs and semi-IPNs.     

Modeling of X-ray-induced refractive index changes in poly(methyl methacrylate).

The refractive index of bulk poly(methyl methacrylate) samples is modified by X-ray exposure. The intensity of the radiation is distributed over an energy range of 1 to 20 keV with a maximum at 3 keV. For an absorbed dose of about 1 kJ cm(-3), an increase of the refractive index of up to 3x10(-4) is observed. However, for much lower doses of about 10 J cm(-3) a decrease of 4x10(-4) appears. These refractive index changes, as well as the simultaneously arising radiation-induced thickness changes, are detected interferometrically. Based on these observations, on dose calculations, and on literature data, a model is proposed which describes quantitatively the observed refractive index changes. The refractive index increase is caused by a radiation-induced chemical alteration of the polymer composition, while the refractive index decrease is correlated with a decrease of mass density.