Sound attenuation of interpenetrating polymer network foams

Interpenetrating polymer networks (IPNs) composed of polyurethanes and epoxies were prepared by the simultaneous technique. Modifications of the polymer structures resulted in a series of IPNs exhibiting semimiscible behavior, as evidenced by broad glass transitions in the dynamic mechanical spectra. Since this indicates materials with potentially good sound attenuation properties as a function of temperature and frequency, foams were prepared from these IPN systems. Enhanced sound absorption occurred in these foams when measured using the impedance tube method.     

Acronal-polymethyl acrylate interpenetrating polymer networks

Four interpenetrating polymer networks were prepared by swelling crosslinked Acronal (a copolymer of styrene and butyl acrylate) with methyl acrylate plus crosslinking agent and then polymerizing the methyl acrylate in situ. Certain properties of the constituent network materials, plus the interpenetrating polymer networks which contained 70, 50, 35 and 25% by weight of polymethyl acrylate, were investigated. Electron microscopy showed the interpenetrating polymer networks to be two-phase materials with the polymethyl acrylate domain size increasing with increasing polymethyl acrylate content. Longitudinal sonic velocity measurements indicate that at around 50% by weight of polymethyl acrylate both phases become continuous while dynamic mechanical spectroscopy leads to the view that the constituent networks were not extensively mixed.     

Castor-oil-based interpenetrating polymer networks: Synthesis and characterization

Castor oil was polymerized and crosslinked with sulfur or diisocyanates to form the vulcanized and urethane derivatives, respectively. Both types were swollen with a plastic-forming monomer plus crosslinker, and a second polymerization was carried out in situ. Polyblends were also made by emulsion polymerization of styrene and methyl methacrylate employing hydrolyzed castor oil as the soap. In all three polymerizations, a wide range of compositions was obtained. The resulting interpenetrating polymer networks were characterized using electron microscopy, modulus–temperature measurements, and stress–strain analysis. The polystyrene phase size of the castor oil–urethane/polystyrene IPN was shown to decrease with increased crosslinking of the castor oil component and with increased polystyrene contents. The modulus–temperature study showed two distinct glass transitions in all cases, with evidence of significant mixing of the two components in many cases. The stress–strain results show that some of the IPN's behave as reinforced, highly extensible elastomers at low polystyrene levels, and a rubber-toughened plastics at high levels of polystyrene or crosslinking.     

A semiempirical derivation of phase domain size in interpenetrating polymer networks

In previous papers, interpenetrating polymer networks were shown to display a cellular structure. The phase domain size of polymer II was shown to depend inversely on the crosslink density of polymer I. The present paper presents a semiempirical derivation of equations which show quantitatively the dependence of the phase domain size of polymer II on the crosslinking density of polymer I, and also on the interfacial energy and the overall composition. If polymer II is linear, the dependence on the molecular weight of polymer II is also included. The values of the phase domain sizes so estimated are compared with experimental results. While theory and experiment yield good agreement, the semiempirical nature of the equations must be borne in mind.     

Elastomeric domain-type interpenetrating polymer networks

Elastomeric latex interpenetrating polymer networks (IPNs) can result from a two-stage emulsion polymerization procedure in which styrene is polymerized and cross-linked on a lightly cross-linked polyacrylate (PA) seed latex in a ratio of 75 : 25 PA-PS. The multiphase nature of these IPNs is indicated by two distinct T_gs and is confirmed by cold-stage transmission electron microscopy and by the unique mechanical and rheological properties that are intimately related to the material's structure. PS microdomains reinforce the elastomeric PA, yielding a significant modulus, and interparticle PS physical ties yield a significant ultimate tensile strength. The elastomeric latex IPN's dual thermoset-thermoplastic nature is revealed in a stick, slip, roll flow mechanism of the cross-linked submicrometer particles, which can be injection molded as a thermoplastic. The relationships among the polymerization procedure, the structure, and the physical properties are characterized by the examination of several different materials using a variety of analytic techniques.     

Lignin‐polystyrene composite foams through high internal phase emulsion polymerization

The composites made‐up from renewable fillers and polymer matrix have drawn great attention due to the renewable nature, improved thermal and mechanical properties, environmental issues and most importantly to reduce dependency on fossil fuel resources. In this work, kraft lignin in its modified form (butylated lignin) was used to make composites with polystyrene successfully through bulk polymerization and high internal phase emulsion (HIPE) polymerization. The kraft lignin was first modified to butyrated lignin by esterification using 1‐Methylimidazole as a catalyst in order to increase the compatibility as fillers with both monomer and polymer, which was further studied and verified through Hansen solubility parameter model. The thermal, mechanical, and structural properties of the lignin/polymer composites were systematically investigated. The incorporation of lignin in the composites could increase the modulus significantly and almost double (1,391 MPa) at 15 wt% of lignin loading as compared with bare composites. Excellent porous structure and mechanical properties are maintained with the lignin content as high as 10 wt% of the total foam mass. POLYM. ENG. SCI., 59:964–972, 2019. © 2018 Society of Plastics Engineers     

Thermodynamic characterization of interpenetrating polymer networks

Crosslinked poly(methyl methacrylate) (PMMA-c), poly(carbonate-urethane) (PCU-c), poly(vinyl pyridine) (PVP-c), and full, simultaneous interpenetrating polymer networks (IPNs) based on the above polymers were characterized by precise heat capacity (C_p) measurements in the temperature interval 4.2–450 K. The raw values of C_p scaled with temperature (T) as C_p ∼ T^d with d = 2 and 5/3, as expected for a fracton-like vibration regime, in the temperature intervals 8–10 and 10–30 K, respectively. A single glass transition temperature (T_g) and two T_g's were observed for apparently homogeneous and microphase-separated IPNs, respectively. Judged by the positive sign of the excess Gibbs free energy, the apparently single-phase state of homogeneous IPNs is thermodynamically unstable; however, its kinetic stability is ensured by permanent topological constraints (network junctions) prohibiting the incipient phase separation.     

Recent studies on interpenetrating polymer networks

Recent investigations on interpenetrating polymer networks (IPNs) have included two component IPNs from polyurethanes and poly(methacrylates) and two component IPNs from polyurethanes and epoxies. All the IPNs were prepared by the simultaneous polymerization technique (SIN-IPNs). Two types of IPNs, polyurethane-poly(methyl methacrylate) (PU/PMMA) and polyurethane-poly(methyl methacrylate-methacrylic acid) (PU/PMMA-MAA) were prepared. Improved phase miscibility and decreasing extent of phase separation was observed in both types of IPNs with increasing the NCO/OH ratio, decreasing molecular weight of the polyol in the PU and introduction of charge groups. A comparison was made between full-IPNs, pseudo-IPNs, graft copolymers and related homopolymers from polyurethanes and epoxies. Increased compatibility in full-IPNs and graft copolymers was observed by means of DSC, SEM and was also further substantiated by a shift toward single T_gs as determined by dynamic mechanical spectroscopy. The introduction of opposite charge groups in two-component IPNs from polyurethanes and epoxies led to improved compatibility (no phase separation) and enhanced mechanical properties.     

Recent advances in interpenetrating polymer networks

Interpenetrating polymer networks (IPN's) can be defined as a combination of two polymers in network form, at least one of which was synthesized and/or crosslinked in the immediate presence of the other. Historically, the science of IPN's began with the papers of J. R. Millar in 1960 on homo-IPN's made from polystyrene, but the first recorded publication is a patent by J. W. Aylsworth in 1914. This latter system was based on phenol-formaldehyde for one network, and sulfur cured natural rubber for the other network. Early academic laboratories interested in IPN's include the Frisch team at Detroit and SUNY, who soon added their former student, Danny Klempner, and Yuri Lipatov's team at the Ukranian SSR Academy of Sciences in the USSR, as well as the author's laboratory. More recent academic teams interested in IPN's include Douglas Hourston at the University of Lancaster, England; Robert Cohen at MIT; S. C. Kim at the Korea Advanced Institute of Science and Technology, Seoul, Korea; G. Meyer and J. M. Widmaier in Strasbourg, France; and many others. Numerous industrial laboratories are interested, noting that about 90 U.S. patients have been granted, most of them in the past ten years. Systems of special interest include the new thermoplastic IPN's, which are really hybrid materials between polymer blends and IPN's, and the IPN-based RIM (reaction injection molding) materials. Other materials include the sequential IPN's and the SIN's, which have both polymers simultaneously polymerized, and the latex IPN's, which often exhibit core-shell characteristics.     

Two and three component interpenetrating polymer networks

Two and three component interpenetrating polymer networks (IPNs) have been prepared from polyurethanes, epoxy resins, and acrylic copolymers using the simultaneous technique (SIN). These materials exhibited a variety of morphologies and properties dependent on the types of polymer, molecular weight of precursors, presence of charge groups, and presence of intentional grafts between the component polymer networks. In general, decreasing molecular weight of prepolymers, presence of intentional grafts, and presence of charge groups of opposite charge resulted in increased homogeneity (interpenetration). In addition, increased homogeneity resulted in enhanced mechanical properties.     

Recent advances in interpenetrating polymer networks

We review the synthesis, morphology, and physical and mechanical properties of IFNs as well as the related pseudo-IPNs, in which only one of the polymers is crossliriked. Recent studies have shown that the degree of phase separation achieved in these materials is strongly dependent on the compatibility of blends of the linear polymer constituents of the IPN components as well as the kinetics of chain extension and the presence of grafting between component polymers. We illustrate this by a series of IPNs consisting of a polyurethane and an acrylic copolymer. The acrylic is a typical automotive enamel. An enhancement in properties results, which is dependent on the amount of grafting and the kinetics of polymerization. Also discussed are IPNs of a polyurethane and an epoxy, which exhibit a synergism in adhesive properties, and IPNs of a RIM polyurethane with several epoxies and unsaturated polyesters. In addition, also reported are the preliminary studies on the first successful preparation of a three-component IPN, consisting of a polyurethane, an epoxy, and an acrylic.     

Polybutadiene/polystyrene interpenetrating polymer networks

Interpenetrating polymer networks (IPN's) of polybutadiene (PB) and polystyrene (PS) were prepared using both random (containing 36% cis, 55% trans, and 9% 1,2 vinyl) PB and high-cis PB. For both series, a wide range of PB/PS compositions were synthesized. Using samples stained with osmium tetroxide, electron microscope studies revealed an irregular cellular structure of a few hundred Ångstrom diameter with the first component, PB, making up the cell walls. The size of the cells was found to depend on the PB crosslink density for the random materials. Modulus-temperature data revealed two distinct glass transitions, confirming the microscopy finding of two phases. However, the transition temperature and transition slope varied with composition, and with the microstructure of the polybutadiene, giving evidence of significant molecular mixing. Stress-strain data on the IPN's showed that materials rich in PB behave like self-reinforced elastomers. Charpy impact resistance experiments on materials rich in PS indicated values of 5 ft-lb/in. of notch, which compares well with graft-type polyblends of similar PB/PS composition. The results were interpreted in the light of the recent theoretical work of Bragaw, who considered the importance of the distances between domain boundaries with respect to crack acceleration mechanics. Although the IPN's considered herein exhibited somewhat less than the predicted optimum phase dimensions, the arrangement of the domains is different from ordinary impact resistant plastics.     

Capillary extrusion of elastomeric emulsion crosslinked interpenetrating networks

The rheological properties of an elastomeric emulsion thermosetting (EMSET) interpenetrating network (IPN) of poly(ethyl acrylate) (70 percent) and polystyrene (30 percent) were studied using a capillary rheometer to test if the submicron thermoset particles, persumably the flow units, could flow as a thermoplastic matrix. The IPN exhibited power law behavior over a wide range of shear rates (0.05 to 500 s^?1), with a power law exponent of approximately 0.18 over a large range of temperatures (80 to 200°C), without a yield stress or a Newtonian plateau evident. The flow activation energies were found to be comparable with most processable thermoplastic materials at 4 kcal/mole for constant shear rates, and 20 kcal/ mole for constant shear stresses. The effect of a roll mill shear modification step prior to extrusion indicated stability of the flow units. The pervasive rippling melt fracture and the significant slip velocity at the wall emphasized the importance of slip in the flow mechanism of this elastomeric EMSET IPN.     

Tailoring mechanical properties of highly porous polymer foams: Silica particle reinforced polymer foams via emulsion templating

The aim of this work was to synthesise highly open porous low-density polymer foams with superior mechanical properties by the polymerisation of the organic phase of concentrated emulsions. The continuous organic phase of the concentrated emulsion template occupying up to 40 vol% was polymerised leading to polymer foams with much improved mechanical properties. The Young's modulus as well as the crush strength of the foams was further increased dramatically by reinforcing the polymer phase with nanosized silica particles. To ensure that the silica particles were covalently incorporated into the polymer network, methacryloxypropyltrimethoxysilane (MPS) was added to the formulation, which reacts with the silica via hydrolysis reactions. The Young's modulus of silica reinforced foams increased by 280% and the crush strength by 218% in comparison to foams without reinforcement.     

Castor oil based interpenetrating polymer networks. II. Synthesis and properties of emulsion polymerized products

Polystyrene Latexes were synthesized using sodium ricinoleate (the ehief saponification product of castor oil) as the surfactant. Later sulfur, more sodium ricinoleate, and sometimes castor oil were added, and the emulsion heated to a temperature where the sulfur vulcanized the castor oil products, making a semi-interpenetrating polymer network. Stress-strain studies showed the presence of a well developed yield point and high elongation for some samples, indicating considerable toughening for slow rates of strain. Electron microscopy revealed a complex two-phased morphology. Usually polystyrene was the continuous phase. The rubbery phase domain size depended upon the amount of castor oil products added lzod impact strengths showed only modest improvements; probably because of the high glass transition temperature of the castor oil vulcanizate.     

Properties and structure of elastomeric two-stage emulsion interpenetrating networks

Interpenetrating polymer networks (IPNs) consist of two crosslinked polymers which form a network within a network. Bulk-prepared IPNs are thermosetting and cannot be processed due to the formation of a macroscopic network. Emulsion IPNs, although thermosetting, can be processed as thermoplastic materials. This is due to a special particle-slippage flow mechanism which is practically insensitive to molecular weight. The morphology of the reported latex particles is unique in the sense that very small polystyrene domains are formed by phase-separation of polymerizing styrene added to a seeded flexible polyacrylate latex. Compression or injection moulded specimens of these crosslinked elastomeric materials show significant mechanical properties. Some properties and structural observations using a special electron microscopy technique are described in this article. This method is based on the differential radiation damage to various polymers embedded in ice and can be used as an analytical tool to determine the microstructure of certain multiphase systems.     

Homogeneous epoxy-acrylic interpenetrating polymer networks: preparation and thermal properties

Summary The simultaneous interpenetration of two networks, one based on diglycidyl ether of bisphenol A crosslinked by an aliphatic diamine and the other one based on diglycidyl ether of bisphenol A dimethacrylate, leads to systems transparent to visible light. The measurement of glass transition temperature of these IPNs as a function of the composition and of the crosslinks density, gives relatively low and single values. This behavior is interpreted by the homogeneous structure of these systems.Presented at the 7th Discussion Conference IUPAC Polymer Networks, Karlovy Vary, CSSR, September 15–19, 1980     

互穿聚合物网络的研究与应用进展

简要介绍了互穿聚合物网络(IPN)的基本结构、制备以及在树脂改性、胶粘剂、阻尼材料、多孔材料和医药等领域中的应用情况。由于IPN可以兼具多种聚合物的优点,并且其制备简单、设备要求较低,故其应用范围越来越广泛,应用前景也越来越好。     

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.     

Glass transitions of topologically interpenetrating polymer networks

Two component topologically-interpenetrating polymer networks were made of the SIN type (simultaneous interpenetrating network) composed of two polyurethanes (a polyether-based and a polyester-based) in combination with an epoxy resin, a polyacrylate and two unsaturated polyesters. The linear polymers and/or prepolymers were combined in solution and in bulk together with the necessary crosslinking agents and catalysts. Films were cast and chains extended and crosslinked in situ. All of the IPN's exhibited one glass transition (T_g) intermediate in temperature to the T_g's of the component networks, and as sharp as the T_g's of the components. This suggests that phase separation may not occur and thus some chain entanglement (interpenetration) of the two networks is involved. The observed T_g's are always several degrees lower than the arithmetic means of the component T_g's. A theory based on interpenetration is developed to account for this.