Semi- and fully interpenetrating polymer networks based on polyurethane–polyacrylate systems. VII. Polyurethane–poly(methyl acrylate) interpenetrating polymer networks

A series of polyurethane–poly(methyl acrylate) sequential interpenetrating polymer networks containing 40 wt % polyurethane were prepared. The triol/diol ratio used in the preparation of the first formed polyurethane network was changed so that the average molecular weight between crosslinks ranged from 9500 to 500 g/mol. In addition to decreasing this average molecular weight, changing the triol/diol ratio alters the hard segment content of the polyurethane. The extent of mixing of the components in these IPNs was investigated using electron microscopy, dynamic mechanical analysis, tensile testing, and sonic velocity measurements. The polyurethane networks were also characterized by swelling studies. It was concluded that, as the triol/diol ratio increased, the extent of mixing increased and there was evidence of phase separation of the hard segments of the polyurethane component at high triol/diol ratios.     

Semi- and fully interpenetrating polymer networks based on polyurethane–polyacrylate systems. II. Polyurethane–poly(methyl acrylate) semi-1-interpenetrating polymer networks

A series of semi-1-IPNs based on polyurethane networks and poly(methyl acrylate) were prepared, and their properties and morphologies investigated. All the materials showed substantial phase separation, but the phase sizes were orders of magnitude smaller than those observed for blends of the same linear polymers. The effects of the isocyanate/hydroxyl ratio used in the preparation of the polyurethane, of the molecular weight of the linear polymethyl acrylate component, of the overall composition, and of the molecular weight between crosslinks in the polyurethane networks were investigated. Stress-relaxation experiments were conducted over a range of temperatures and master curves were produced for both components of the semi-1-IPNs and for a semi-1-IPN containing 40 wt% polyurethane. It was found that both the components obeyed a WLF type of equation, but that the semi-1-IPN only showed this type of behavior over a limited temperature range. Several reinforcement theories were applied to experimental dynamic storage modulus data. The closest fit was given by the Davies equation and by the logarithmic rule of mixing. By changing the exponent in the Davies equation to 1/10, a close fit was found. Application of a modified Takayanagi model indicated that these semi-1-IPNs showed some dual phase continuity when the poly(methyl acrylate) composition was relatively high.     

Polyurethane—polystyrene interpenetrating polymer networks

Two component interpenetrating polymer networks (IPN) of the SIN type (simultaneous interpenetrating networks), composed of a polystyrene network (crosslinked with divinyl benzene) and a polyester-polyurethane network (crosslinked with trimethylolpropane), were made. Electron microscopy and glass-transition measurements showed that phase separation had resulted with some interpenetration, presumably occurring at the boundaries. At a composition of about 75 percent polyurethane, a phase inversion occurred, the continuous phase being polystyrene at polyurethane compositions of less than 75 percent. The stress-strain properties and hardness measurements agreed with these results. Enhanced tensile strength was observed in the IPN's in a concentration range where modulus reinforcement was not evident. A small enhancement in tear strength and thermal stability was also noted.     

Semi- and fully interpenetrating polymer networks based on polyurethane–polyacrylate systems. III. Polyurethane–poly(methyl acrylate) semi-2-interpenetrating polymer networks

Two series of semi-2-IPNs based on a polyurethane and a poly(methyl acrylate) crosslinked with divinyl benzene were prepared and investigated using dynamic mechanical analysis, sonic velocity measurements, and electron microscopy. In the one series, the level of crosslinking was varied to give ultratight networks. In the other, the composition was altered, but the amount of the crosslinking agent used was kept constant. For the first series, it was concluded that the degree of crosslinking had a significant influence on the morphology and properties by controlling the amount of enforced mixing. The dynamic mechanical data for the second series fitted the Davies modulus–composition equation, indicating that both phases are continuous.     

Semi- and fully interpenetrating polymer networks based on polyurethane–polyacrylate systems. VI. Polyurethane–poly(methyl acrylate-co-ethyl acrylate) semi-1-interpenetrating polymer networks

Dynamic mechanical and longitudinal sonic velocity measurements have been made on a series of semi-1-IPNs in which the network component is a polyurethane and the linear constituent a copolymer of methyl acrylate and ethyl acrylate. Dynamic mechanical analysis reveals phase separation. The shifting of the polyurethane glass transition in both the tan δ? and the E″–temperature plots indicates that some mixing occurs. The longitudinal sonic velocity results indicate that the polyurethane is present as a continuous phase in all the materials investigated.     

Stress–strain properties of polyurethane–polyacrylate interpenetrating polymer networks

Two-component interpenetrating polymer networks (IPN) of the SIN type (simultaneous interpenetrating networks) were prepared from two different polyurethanes (a polyester type and a polyether type) and a polyacrylate of two different crosslink densities. The linear polymers and prepolymers were combined in solution, together with crosslinking agents and catalysts, films cast, and subsequently chain extended and crosslinked in situ. In all cases, maxima in tensile strengths significantly higher than the tensile strengths of component networks occurred. This was explained by an increase in crosslink density due to interpenetration.     

Polyurethane–epoxy maleate of bisphenol a semi‐interpenetrating polymer networks

Semi‐interpenetrating polymer networks were synthesized starting from polyurethane (PU) and epoxy maleate of bisphenol A (EMBA). Differential scanning calorimetry and swelling measurements showed good miscibility and the presence of the strong intermolecular interactions within the synthesized networks. The physicomechanical properties increased against PU to a maximum value with the increasing of EMBA content up to 12 wt % and then decreased with further increasing EMBA content. Generally, with exception of the elongation at the limit of elasticity, the mechanical properties improved very much under action of the UV radiation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 138–144, 2002     

Semi- and fully interpenetrating polymer networks based on polyurethane–polyacrylate systems. I. The polyurethane networks

The polyurethane networks based on commerical prepolymer, Adiprene L-100, and trimethylol propane (system 1) and on toluene diisocyanate, polypropylene gylcol, and trimethylol propane (system 2) were prepared and characterized in a number of ways. The materials constitute the first formed networks in a series of interpenetrating polymer networks and semi-interpenetrating polymer networks to be reported in subsequent papers in this series. System 1 networks were characterized by swelling tests which showed the M _c values to be sensitive to the amount of polyurethane present in the polymerization solvent. Stress–strain, stress–relaxation, and dynamic mechanical analyses wer also conducted. For system 2, M _c was measured, by both the swelling and the Mooney–Rivlin techniques, for materials in which the diol-to-triol ratios had been altered. the latter showed C₁ increasing as M _c decreased while C₂ was small and changed onlyy slightly indicating approximately ideal behavior. These M _c values were about 13 % larger than predicted by swelling.     

Polyurethane–polystyrene interpenetrating polymer networks synthesized at low temperature: Effect of crosslinking level

Interpenetrating polymer networks (IPNs) of polyurethane (PU)–polystyrene (PS) containing 50 wt % PU were synthesized at low temperature with varying crosslink density of each component. PU was polymerized first, followed by the photopolymerization of PS at low temperature (0 and 40°C). The theoretical molecular weight between crosslink (M?_c) of PU ranged from 8200 to 2050, and the M?_c of PS varied from linear to 2000. The degree of mixing of the components in these IPNs was investigated using dynamic mechanical analysis, electron microscopy, and density measurement. The degree of mixing increased with decreasing M?_c and/or synthesis temperature. The crosslink density variation at low synthesis temperature is more effective in enhancing the miscibility of IPN than at high synthesis temperature, because both the temperature and crosslink density can affect the polymer chain mobility during the synthesis. The variation of PU network crosslink density shows the better effect in increasing the miscibility of IPN than that of the PS network. The morphology and the density behavior agree well with the dynamic mechanical result.     

丙烯酸酯系胶乳互穿聚合物网络的合成及阻尼性能

以种子乳液聚合法合成了聚苯乙烯／聚丙烯酸乙酯、聚甲基丙烯酸乙酯／聚丙烯酸丁酯的核-壳胶乳互穿聚合物网络(LIPN),分别测试了不同配比LIPN及其共混物的阻尼性能、物理机械性能和吸水性能。结果表明,LIPN共混物是具有阻尼温域宽、阻尼性能优、物理机械性能良好和吸水率较低的阻尼材料,其阻尼性能主要取决于共混组分的性能、配比和内耗能的贡献,并且与共混物的织态结构也密切相关。     

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.     

Semi- and fully interpenetrating polymer networks based on polyurethane–polyacrylate systems. V. An isomerically related semi-1-interpenetrating polymer network system

A series of polyurethane–poly(vinyl acetate) semi-1-IPNs were synthesized, and certain physical properties investigated. Electron microscopy showed all the materials to be substantially phase-separated, but evidence from dynamic mechanical analysis indicated that some mixing occurred, because the polyurethane glass transition was shifted in both the tan σ? and the E″–temperature curves. The variation of modulus with composition was found to be reasonably close to the predictions of the Davies equation. When the exponent in that relation was changed to ?, a good fit was obtained. Synergism with respect to tensile strength was observed for two of the semi-1-IPNs. Stress–relaxation measurements, over a fairly narrow temperature range, were made on the semi-1-IPN containing 40% by weight of the polyurethane network. A master curve was constructed. It was noted that the WLF equation was not obeyed by this semi-1-IPN at temperatures above about 50°C.     

Poly(vinyl acetate)/polyacrylate semi‐interpenetrating polymer networks. II. Thermal,mechanical, and morphological characterization

The thermal, dynamic mechanical, and mechanical properties and morphology of two series of semi‐interpenetrating polymer networks (s‐IPNs) based on linear poly(vinyl acetate) (PVAc) and a crosslinked n‐butyl acrylate/1,6‐hexanediol diacrylate copolymer were investigated. The s‐IPN composition was varied with different monoacrylate/diacrylate monomer ratios and PVAc concentrations. The crosslinking density deeply affected the thermal behavior. The results showed that a more densely crosslinked acrylate network promoted phase mixing and a more homogeneous structure. The variation in the linear polymer concentration influenced both the morphology and mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fatigue behavior of acrylic interpenetrating polymer networks. II

Energy-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 (K_1c) 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.     

Permeation of oxygen through polyurethane–polyepoxide interpenetrating polymer networks

Oxygen permeation studies on polyurethane (PU)/polyepoxide (EP) interpenetrating polymer networks show that the increased crosslinking density owing to additional permanent chain entanglement (resulting from interpenetration) can decrease the coefficients of permeation, diffusion, and oxygen solubility. At 20% PU, at which the crosslinking density is maximum, these coefficients retain minimum values, while the tensile strength retains a maximum value.     

Synthesis and characterization of polyurethane–chitosan interpenetrating polymer networks

A polyurethane–chitosan (PU–CH) coating was synthesized from castor-oil-based PU prepolymer and highly deacetylated and depolymerized chitosan. The films cast with the coating were used for the characterization. X-ray photoelectron spectroscopy, a surface-sensitive technique, indicated the chemical bonding between the chitosan and PU prepolymer as well as the enrichment of chitosan on the surface of the film PU–CH. Electron spin resonance (ESR) spectroscopy using the nitroxyl radical 4-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl (4-hydroxy-TEMPO) as a reporter group was used to study the chain mobility in the film PU–CH. It was observed that T_50G of the probe and the first glass transition temperature (T_g1) of the film PU–CH were 10 and 18°C higher than those in the PU film, respectively, and the activation energy (27.0 kJ mol⁻¹) of tumbling for the probe covalently bonded with PU–CH was 12.8 kJ mol⁻¹ higher than that of the probe with the film PU. It suggests that the molecular motion in the PU–CH was restricted by grafted and crosslinked interpenetrating polymer networks (IPNs). The results of the differential thermal analysis and thermogravimetric analysis proved that the thermostability of the film PU–CH was significantly higher than that of the film PU, and the T_g1 value is in good agreement with that calculated from ESR. It could be concluded that the IPNs resulted from the chitosan grafting and crosslinking with PU exist in the film PU–CH. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1321–1329, 1998     

Morphology development in polychloroprene–polystyrene latex interpenetrating polymer networks

Latex interpenetrating polymer networks (LIPNs) have been prepared using a crosslinked polychloroprene latex as the seed emulsion, followed by the in situ polymerization of styrene, typically with a 10% divinyl benzene crosslinker. Polychloroprene–crosslinked polystyrene (XPS) ratios ranging from 70/30 to 40/60 were used, with the second monomer being added as a single aliquot rather than by “starvation” routes. The majority of the work has been conducted using the water‐soluble persulfate initiator method, which entails lengthy (∼ 6 h) polymerizations. To follow the development of microstructure, polymerizations were also stopped at 0.5, 1, and thence hourly intervals up to 6 h, so that any effect of time on shell and domains could be seen by transmission electron microscopy (TEM). Parallel studies using azo‐bis(isobutyronitrile) (AIBN) as initiator at the same temperature were conducted. Products were also studied, after staining, by TEM. For the persulfate initiator, domain structures predominated for the 70/30 ratio, but polystyrene‐rich shells are found in all cases, with increasing thickness as the chloroprene/styrene ratio was reduced. The styrene‐rich products (i.e., 40/60 Neoprene/XPS ratio) appear to have larger unstained domains suggesting phase separation. For the AIBN‐initiated styrene polymerization, shells are less evident, and where they exist, are both thinner and less continuously developed. Domain sizes are somewhat larger. This relatively hydrophobic initiator has caused polymerization predominately in the interior of each latex particle. The particle size distribution of the seed neoprene latex is broad and bimodal. As the LIPNs form, the larger diameter component increases and little evidence for fresh nucleation, in the form of small diameter particles, is seen. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 629–638, 1999     

高抗冲PVC复合树脂加工性能研究

研究了聚丙烯酸酯原位聚合具有互穿网络结构的PVC复合树脂在管材加工方面的应用。研究结果表明,该复合树脂的流动性较好、易加工、热稳定性好、加工温度范围宽,尤其是冲击强度大幅提高、韧性强。     

Semi- and fully interpenetrating polymer networks based on polyurethane–polyacrylate systems. XI. The influence of polymerization temperature on morphology and properties

Polyurethane–poly(methyl acrylate) interpenetrating polymer networks (IPNs) of fixed composition (50/50) were prepared at 200 MPa and a range of temperatures. Decreased synthesis temperatures generally resulted in improved mixing of the two networks, although the sequence of formation of the two polymers was also important. No obvious improvements in physical properties resulted from the enhanced mixing. At high synthesis temperatures, the exothermic heat of polymerization of the methyl acrylate led to excessive temperatures, capable of degrading the already-formed polyurethane network. This resulted in a deterioration in tensile strength and a decrease in hardness of the IPN. © 1992 John Wiley & Sons, Inc.     

Reaction compatibilization in interpenetrating polymer networks II. Polyurethane-polystyrene-oligourethane dimethacrylate system

The effects of compatibilizing additive (oligo-urethane dimethacrylate) on the kinetics of IPN formation based on cross-linked polyurethane and linear polystyrene and its influence on the microphase separation, viscoelastic and thermophysical properties have been investigated. It was established, that 10, 20 mass% of OUDM introduced into the initial reaction system, prevent microphase separation of the system and lead to the formation of compatible IPNs, as follows from the data on light scattering. The viscoelastic and thermophysical properties of modified IPN (20 mass% OUDM) are changed in such a way that instead of two relaxation transitions characteristic for phase-separated system, only one relaxation transition is present. It is results of change the morphology of system. The position of this relaxation transition depends on the system composition and on the reaction conditions.