Increasing Epoxy Content Research Articles

Structure, mechanical properties, and gas permeability of elastomers based on polybutadiene and epoxy resin

AbstractIn this study, the structure, gas permeability, and mechanical properties of new elastomers based on liquid polybutadiene and epoxy resin were investigated by dynamic mechanical thermal analysis, thermogravimetric analysis, stress–strain analysis, and water‐resistance and gas permeability tests. The results reveal that there was complete phase separation between the epoxy resin and polybutadiene. With increasing epoxy resin content, the glass‐transition temperature of the soft segment varied little. These elastomers had tensile strengths of 6–10 MPa and ultimate elongations of 500–100% according to the different epoxy resin contents. Thermogravimetric analysis revealed that these elastomers had better thermal stability, with a 5% weight loss at a temperature of around 350°C. The gas permeabilities of these elastomers were measured to be 13.2–15.3 barrers for oxygen, 4.8–5.3 barrers for nitrogen, and 28–35 barrers for carbon dioxide at 23°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Hydrogen bonding interactions, crystallization, and surface hydrophobicity in nanostructured epoxy/block copolymer blends

AbstractHydrogen bonding interactions, phase behavior, crystallization, and surface hydrophobicity in nanostructured blend of bisphenol A‐type epoxy resin (ER), for example, diglycidyl ether of bisphenol A (DGEBA) and poly(ε‐caprolactone)‐block‐poly(dimethyl siloxane)‐block‐poly(ε‐caprolactone) (PCL–PDMS–PCL) triblock copolymer were investigated by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, transmission electron microscopy, small‐angle X‐ray scattering, and contact angle measurements. The PCL–PDMS–PCL triblock copolymer consisted of two epoxy‐miscible PCL blocks and an epoxy‐immiscible PDMS block. The cured ER/PCL–PDMS–PCL blends showed composition‐dependent nanostructures from spherical and worm‐like microdomains to lamellar morphology. FTIR study revealed the existence of hydrogen bonding interactions between the PCL blocks and the cured epoxy, which was responsible for their miscibility. The overall crystallization rate of the PCL blocks in the blend decreased remarkably with increasing ER content, whereas the melting point was slightly depressed in the blends. The surface hydrophobicity of the cured ER increased upon addition of the block copolymer, whereas the surface free energy (γs) values decreased with increasing block copolymer concentration. The hydrophilicity of the epoxy could be reduced through blending with the PCL–PDMS–PCL block copolymer that contained a hydrophobic PDMS block. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 790–800, 2010

Epoxidation of high trans‐1,4‐polyisoprene and its properties

AbstractA new organic‐solvent‐free water‐phase suspension method was used to synthesize partially epoxidized high trans‐1,4‐polyisoprene (TPI) to improve its properties, including oil resistance and wet‐skid resistance. The epoxidation was conducted in an aqueous peracetic acid solution and on the TPI granules prepared by a bulk precipitation method with supported titanium catalyst. The effects of the synthesis conditions, including reaction temperature, reaction time, and pH value, on the epoxy content were investigated. Epoxidized trans‐1,4‐polyisoprene (ETPI) with epoxy contents between 10 and 80% were obtained within 4 h. Both the amorphous and crystalline regions of TPI were epoxidized. The crystallization properties decreased with increasing epoxy content. ETPIs possessed lower mechanical properties than TPI but could be enhanced by vulcanization. The oil resistance and wet‐skid resistance were significantly improved after epoxidation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The effect of epoxy‐polyester hybrid resin on mechanical properties, rheological behavior, and water absorption of polypropylene wood flour composites

AbstractThe effect of epoxy resin on mechanical and Rheological properties, and moisture absorption of wood flour polypropylene composites (WPCs) were investigated. The reactive mixing of epoxy resin with 30, and 40 wt% wood flour and polypropylene (PP) was carried out in twin screw extruder with a special screw elements arrangement. PP grafted maleic anhydrides (MPP) were used as coupling agent to improve the interfacial interactions of wood flour, epoxy resin, and PP. The tensile strength of composites decreased, and elastic modulus and moisture absorption increased with increasing epoxy resin content. The complex viscosity η* increased with increasing epoxy resin content of composites, and a synergistic effect in increasing the η* was observed at 3 wt% resin. The epoxy resin modified wood‐PP composites that chemically coupled by MPP showed minimum water absorption with highest elastic modulus. The experimental oscillation rheologyical data were used to drive a model to predict the flow behavior of WPCs, in a wide range of frequencies. POLYM. ENG. SCI., 47:2041–2048, 2007. © 2007 Society of Plastics Engineers

Carbon black‐filled immiscible polypropylene/epoxy blends

AbstractCarbon black‐ (CB) filled immiscible thermoplastic/thermosetting polymer blends consisting of polypropylene (PP) and epoxy resin were reported in this paper. The PP/epoxy/CB blends with varied compositions and different processing sequences were prepared by melt‐mixing method. The CB distribution and the relationship between morphology and electrical properties of the PP/epoxy/CB blends were investigated. Scanning electron microscopy (SEM), optical microscopy, and extraction experimental results showed that in PP/epoxy blends CB particles preferentially localized in the epoxy phase, indicating that CB has a good affinity with epoxy resin. The incorporation of CB changed the spherical particles of the dispersed epoxy phase into elongated structure. With increasing epoxy content, the elongation deformation of epoxy phase became more obvious and eventually the blends developed into cocontinuous structure. When CB was initially blended with PP and followed by the addition of epoxy resin, the partial migration of CB from PP to the epoxy phase was observed. When the PP/epoxy ratio was 40/60, the percolation threshold was reduced to about 4 phr CB, which is half of the percolation threshold of the PP/CB composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 461–471, 2006

Structural-mechanical relationship of epoxy compatibilized polyamide 6/polycarbonate blends

Polyamide 6 (PA6)/polycarbonate (PC) blends compatibilized with solid epoxy resin (bisphenol type-A) were prepared by extrusion followed by injection molding. The effects of epoxy resin on the microstructure, tensile, impact and compatibility of the PA6/PC blends were investigated. The results showed that both the tensile modulus and elongation at break of PA6/PC blends were inferior as compared to their parent polymers. This resulted from incompatibility between the PA6 and PC phases. SEM observation revealed that the introduction of 0.5 part per hundred (phr) epoxy resin into the PA6/PC75/25 blend yields a finer dispersion of PC phase in PA6 matrix. The boundaries between the PC domains and PA6 matrix became obscure with the incorporation of 1 phr epoxy resin. Such an improvement in compatibility was suggested to be resulted from the formation of in situ epoxy bridged PA6-PC block copolymer in the blend during compounding. Consequently, the tensile modulus, yield strength and impact strength of the PA6/PC 75/25 blend improved considerably with increasing epoxy content.

Dynamically cured polypropylene/epoxy blends

AbstractThe dynamic vulcanization process, usually used for the preparation of thermoplastic elastomers, was used to prepare polypropylene (PP)/epoxy blends. The blends had crosslinked epoxy resin particles finely dispersed in the PP matrix, and they were called dynamically cured PP/epoxy blends. Maleic anhydride grafted polypropylene (MAH‐g‐PP) was used as a compatibilizer. The effects of the reactive compatibilization and dynamic cure were studied with rheometry, capillary rheometry, and scanning electron microscopy (SEM). The crystallization behavior and mechanical properties of PP/epoxy, PP/MAH‐g‐PP/epoxy, and dynamically cured PP/epoxy blends were also investigated. The increase in the torque at equilibrium for the PP/MAH‐g‐PP/epoxy blends indicated the reaction between maleic anhydride groups of MAH‐g‐PP and the epoxy resin. The torque at equilibrium of the dynamically cured PP/epoxy blends increased with increasing epoxy resin content. Capillary rheological measurements also showed that the addition of MAH‐g‐PP or an increasing epoxy resin content increased the viscosity of PP/epoxy blends. SEM micrographs indicated that the PP/epoxy blends compatibilized with PP/MAH‐g‐PP had finer domains and more obscure boundaries than the PP/epoxy blends. A shift of the crystallization peak to a higher temperature for all the PP/epoxy blends indicated that uncured and cured epoxy resin particles in the blends could act as effective nucleating agents. The spherulites of pure PP were larger than those of PP in the PP/epoxy, PP/MAH‐g‐PP/epoxy, and dynamically cured PP/epoxy blends, as measured by polarized optical microscopy. The dynamically cured PP/epoxy blends had better mechanical properties than the PP/epoxy and PP/MAH‐g‐PP/epoxy blends. With increasing epoxy resin content, the flexural modulus of all the blends increased significantly, and the impact strength and tensile strength increased slightly, whereas the elongation at break decreased dramatically. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1437–1448, 2004

Crystallization behavior of dynamically cured polypropylene/epoxy blends

AbstractDynamically cured polypropylene (PP)/epoxy blends compatibilized with maleic anhydride grafted PP were prepared by the curing of an epoxy resin during melt mixing with molten PP. The morphology and crystallization behavior of dynamically cured PP/epoxy blends were studied with scanning electron microscopy, differential scanning calorimetry, and polarized optical microscopy. Dynamically cured PP/epoxy blends, with the structure of epoxy particles finely dispersed in the PP matrix, were obtained, and the average diameter of the particles slightly increased with increasing epoxy resin content. In a study of the nonisothermal crystallization of PP and PP/epoxy blends, crystallization parameter analysis showed that epoxy particles could act as effective nucleating agents, accelerating the crystallization of the PP component in the PP/epoxy blends. The isothermal crystallization kinetics of PP and dynamically cured PP/epoxy blends were described by the Avrami equation. The results showed that the Avrami exponent of PP in the blends was higher than that of PP, and the crystallization rate was faster than that of PP. However, the crystallization rate decreased when the epoxy resin content was greater than 20 wt %. The crystallization thermodynamics of PP and dynamically cured PP/epoxy blends were studied according to the Hoffman theory. The chain folding energy for PP crystallization in dynamically cured PP/epoxy blends decreased with increasing epoxy resin content, and the minimum of the chain folding energy was observed at a 20 wt % epoxy resin content. The size of the PP spherulites in the blends was obviously smaller than that of PP. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1181–1191, 2004

Dynamically Cured PP/Epoxy Blends Compatibilised with MAH-g-PP

The dynamic vulcanization process usually used to prepare thermoplastic elastomers was used to prepare polypropylene (PP)/epoxy blends compatibilised with maleic anhydride-grafted PP. The influence of dynamic cure, MAH-g-PP content, curing agents and epoxy equivalent weight on the mechanical properties of the PP/MAH-g-PP/epoxy blends was investigated. The torque at equilibrium of the blends increased with increasing epoxy resin content. The blends had better mechanical properties than either uncured PP/epoxy or dynamically cured PP/epoxy blends. The flexural modulus and impact strength increased rapidly with increasing MAH-g-PP content and reached a maximum of 2030 MPa and 36 J/m, respectively, at an MAH-g-PP content of 10 wt%. Those blends made using 2-ethylene-4-methane-imidazole as the curing agent had higher impact strength and flexural modulus than the ones made using dicyandiamide. The dynamically cured PP/MAH-g-PP/epoxy blends exhibited better mechanical properties at an epoxy equivalent of 2000 g/mol. The flexural modulus increased significantly with increasing epoxy resin content, while the elongation at break dramatically decreased, and the impact strength was only slightly affected by the presence of the epoxy resin. The PP/epoxy blends compatibilised with MAH-g-PP had finer domains than those of PP/epoxy blends. The FTIR spectra show that the functional groups of MAH-g-PP reacted with the epoxy resin. Dynamic mechanical thermal analysis (DMTA) results indicate that the compatibility between the PP and epoxy resin was improved by the addition of MAH-g-PP, and the storage modulus ( E') increased with increasing epoxy resin content. Thermogravimetric analysis (TGA) results show that the incorporation of epoxy resin into PP could improve the thermal stability of PP, and the dynamically cured PP/MAH-g-PP/epoxy blends had better thermal stability than the PP/epoxy and PP/MAH-g-PP/epoxy blends.

Study of dynamically cured PP/MAH-g-EPDM/epoxy blends

In this paper, a novel method concerning the simultaneous reinforcing and toughening of polypropylene (PP) is reported. An epoxy resin was dynamically cured in a PP/maleic anhydride-grafted ethylene-propylene diene elastomer (MAH-g-EPDM) matrix to prepare dynamically cured PP/MAH-g-EPDM/epoxy blends. The small size of epoxy particles in the PP/MAH-g-EPDM/epoxy blends indicates the compatibilizing effect of MAH-g-EPDM. The structure of the dynamically cured PP/MAH-g-EPDM/epoxy blends is such that the epoxy particles are embedded in MAH-g-EPDM. The stiffness and toughness of the blends are in a good balance. The cured epoxy particles increase the stiffness of the blends, and the improvement in the toughness can be attributed to the embedded structure in the blends. The tensile strength and flexural modulus of the blends increase with increasing epoxy resin content, and the impact strength reaches a maximum of 360 J/m at an epoxy resin content of 20 wt%. A shift of crystallization peaks to higher temperatures suggests that dispersed particles in the blends can act as effective nucleating agents, accelerating the crystallization of PP components in the blends. Thermal gravimetric analysis results show that the presence of MAH-g-EPDM in the blends could reduce the thermal stability of PP, but the presence of epoxy resin could improve the thermal stability of PP. The dynamically cured PP/MAH-g-EPDM/epoxy blends have better thermal stability compared to PP.

Epoxy resin/poly(ϵ‐caprolactone) blends cured with 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane. II. Studies by Fourier transform infrared and carbon‐13 cross‐polarization/magic‐angle spinning nuclear magnetic resonance spectroscopy

AbstractCrystalline thermosetting blends composed of 2,2′‐bis[4‐(4‐aminophenoxy)phenyl]propane‐crosslinked epoxy resin (ER) and poly(ϵ‐caprolactone) (PCL) were investigated by means of Fourier transform infrared (FTIR) spectroscopy and high‐resolution solid‐state NMR spectroscopy. FTIR investigations indicated that there were specific intermolecular interactions between ER and PCL and that the intermolecular hydrogen‐bonding interactions were weaker than the self‐association in pure epoxy. The intermolecular hydrogen bonding was considered to be the driving force for the miscibility of the thermosetting blends. For the examination of the miscibility of the thermosetting blends at the molecular level, high‐resolution solid‐state 13C cross‐polarity/magic‐angle spinning (CP‐MAS) NMR spectroscopy was employed. The line width of 13C CP‐MAS spectra decreased with increasing PCL contents, and the chemical shift of the carbonyl carbon resonance of PCL shifted to a low field with an increasing epoxy content in the blends. The proton spin–lattice relaxation experiments in the laboratory frame showed that all the blends possessed identical, composition‐dependent relaxation times (i.e., the proton spin–lattice relaxation times in the laboratory frame), suggesting that the thermosetting blends were homogeneous on the scale of 20–30 nm in terms of the spin‐diffusion mechanism, and this was in a good agreement with the results of differential scanning calorimetry and dynamic mechanical analysis. For the examination of the miscibility of the blends at the molecular level, the behavior of the proton lattice relaxation in the rotating frame was investigated. The homogeneity of the thermosetting blends at the molecular level was quite dependent on the blend composition. The PCL‐lean ER/PCL blends (e.g., 70/30) displayed a single homogeneous amorphous phase, and the molecular chains were intimately mixed on the segmental scale. The PCL‐rich blends displayed biexponential decay in experiments concerning the proton spin–lattice relaxation times in the rotating frame, which was ascribed to amorphous and crystalline phases. In the amorphous region, the molecular chains of epoxy and PCL were intimately mixed at the molecular level. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1099–1111, 2003

Blends of poly(ethylene terephthalate) and epoxy as matrix material for continuous fibre reinforced composites

The morphology and mechanical properties of poly(ethylene terephthalate) (PET)–epoxy blends and the application of these blends in continuous glass fibre reinforced composites have been investigated. Epoxy resin was applied as a reactive solvent for PET to obtain homogeneous solutions with a substantially decreased melt viscosity. The epoxy resin in these solutions was cured using an amine hardener according to two different schedules. In the first, high temperature curing at 260°C preceded low temperature crystallisation of the PET at 180°C. In the second, the PET was allowed to crystallise prior to low temperature curing at 180°C. After cure, all blends revealed a phase separated morphology of dispersed epoxy in a continuous PET matrix. The flexural strength and failure strain of all cured blends showed an increase with increasing epoxy content, whereas the high temperature cured blends exhibited overall lower flexural properties than those cured at the lower temperature. Microstructural analysis and flexural properties of continuous glass fibre reinforced PET–epoxy laminates showed that the composites obtained had a low void content. These PET–epoxy laminates had increased inplane shear strength in comparison with unmodified PET based laminates, indicating considerably increased fibre–matrix adhesion.

Miscibility, crystallization kinetics and real-time small-angle X-ray scattering investigation of the semicrystalline morphology in thermosetting polymer blends of epoxy resin and poly(ethylene oxide)

Thermosetting polymer blends of poly(ethylene oxide) (PEO) and bisphenol-A-type epoxy resin (ER) were prepared using 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) as curing agent. The miscibility and crystallization behavior of MCDEA-cured ER/PEO blends were investigated by differential scanning calorimetry (DSC). The existence of a single composition-dependent glass transition temperature ( T g) indicates that PEO is completely miscible with MCDEA-cured ER in the melt and in the amorphous state over the entire composition range. Fourier-transform infrared (FTIR) investigations indicated hydrogen-bonding interaction between the hydroxyl groups of MCDEA-cured ER and the ether oxygens of PEO in the blends, which is an important driving force for the miscibility of the blends. The average strength of the hydrogen bond in the cured ER/PEO blends is higher than in the pure MCDEA-cured ER. Crystallization kinetics of PEO from the melt is strongly influenced by the blend composition and the crystallization temperature. At high conversion, the time dependence of the relative degree of crystallinity deviated from the Avrami equation. The addition of a non-crystallizable ER component into PEO causes a depression of both the overall crystallization rate and the melting temperature. The surface free energy of folding σ e displays a minimum with variation of composition. The spherulitic morphology of PEO in the ER/PEO blends exhibits typical characteristics of miscible crystalline/amorphous blends, and the PEO spherulites in the blends are always completely volume-filling. Real-time small-angle X-ray scattering (SAXS) experiments reveal that the long period L increases drastically with increasing ER content at the same temperatures. The amorphous cured ER component segregates interlamellarly during the crystallization process of PEO because of the low chain mobility of the cured ER. A model describing the semicrystalline morphology of MCDEA-cured ER/PEO blends is proposed based on the SAXS results. The semicrystalline morphology is a stack of crystalline lamellae; the amorphous fraction of PEO, the branched ER chains and imperfect ER network are located between PEO lamellae.

SORPTION, DIFFUSION, AND PERMEATION OF CHLORINATED HYDROCARBON VAPORS THROUGH NATURAL RUBBER, EPOXIDIZED NATURAL RUBBER, AND THEIR BLENDS

The study investigates the transport process of various chlorinated hydrocarbons through natural rubber (NR), epoxidized natural rubber (ENR), and their blends. The effect of structure and morphology of the membranes on the transport parameters has been investigated. Sorption coefficient is found to increase and the permeability coefficient shows the reverse trend with increasing epoxy content. As the mol% epoxidation increases, the polymeric network structure becomes more compact, which leads to a decrease in the diffusion coefficient, which ultimately results in a low permeation coefficient. The morphology of NR/ENR blends has been investigated by combining scanning electron microscopy with permeability measurements. The permeation coefficient is found to be minimum for the NR/ENR 70/30 composition; a 50/50 composition shows the maximum. The heterogeneous morphology of 70/30 NR/ENR blend results in the low permeability coefficient, whereas the co-continuous nature of the 50/50 composition accounts for the maximum permeability. Permeability measurements provide the most useful information about the way morphology is changing with composition of the blends and about the composition corresponding to the maximum level of co-continuity of the two phases.

Organic–inorganic membranes prepared from polyether diamine and epoxy silane

Organic–inorganic polymer membranes were prepared by reacting 3-glycidoxypropyl trimethoxysilane with diamines containing polyether segments, followed by hydrolysis and condensation with acid catalysis. The films were characterized by nuclear magnetic resonance and by dynamic mechanical analysis. The rigidity of the films increased with increasing epoxy content and also with addition of tetraethoxy silane (TEOS) to the reacting medium. Water absorption experiments showed that the diffusivity is decreased with increasing TEOS content. Membranes were evaluated for nanofiltration giving cut offs down to 860 g/mol (with a water flux of 2.5 l/h m 2 bar). For gas separation, CO 2/N 2 selectivity values up to 89 were obtained with CO 2 permeability of 125 Barrer.

Bulk crystallization of solution epoxidized trans-1,4-polyisoprene

Copolymers of trans-1,4-polyisoprene containing 2,2 mol-%, 5,0 mol-% and 9,8 mol-% epoxidized units were crystallized from the melt at temperatures (Tc) of 25 to 36°C. The progress of the crystallization was monitored, and final crystallinities at Tc and after cooling to 25°C were measured using Fourier-transform infrared spectroscopy. The morphology of samples, treated with OsO4 at 25°C after crystallization was complete, was observed using scanning electron microscopy. The crystallinity decreases linearly with increasing epoxy content at Tc = 25°C and 30°C and shows marked deviations from linearity at Tc = 36°C. Differences in morphology with epoxy content and Tc were observed. The differences in crystallinity between solution and melt crystallized samples are discussed.

Polymer compatibility: Nylon‐epoxy resin blends

AbstractDynamic mechanical and differential scanning calorimetric studies of cured blends of alcohol soluble nylon with up to 40 percent epoxy resin indicate that the blends contain three phases: crystalline nylon phase, crosslinked nylon‐epoxy resin phase, and crosslinked epoxy resin phase. There are unreacted nylon chains distributed in the former two phases. The crystalline nylon phase is composed of partially reacted nylon chains and a small amount of unreacted nylon chains. Degree of ordering in this phase, both unreacted and partially reacted nylon chains, decreases with increasing epoxy resin content. Stress‐strain studies show that stress‐induced crystallization in partially reacted nylon chains in the crystalline nylon phase does occur during elongation resulting in the occurrence of a maximum tensile strength (at 5 percent epoxy resin content) as in the case of crosslinked rubber. Lap shear studies using the blend as an adhesive indicate a maximum strength at 30 percent epoxy resin content, implying that adhesion and crosslinking effects due to incorporation of epoxy resin play a major role in the adhesion performance.

Polybutadiene modified by epoxidation. 1. Effect of polybutadiene microstructure on the reactivity of double bonds

The reactivity of low-molecular weight sodium polybutadiene (1,2-PB) and n-butyllithium polybutadiene (1,4-PB) has been studied during epoxidation with peracetic acid. The effect of the epoxy groups formed on the polymer solution viscosity has also been investigated. It was found that the rate constant of 1,4-PB epoxidation is ∼1.9 times greater than that for 1,2-PB of a similar molecular weight. The reactivity of various structural polymer unit forms was studied by spectroscopic methods (i.r. and 1H n.m.r.); it was found that reactivity depends on chain microstructure in the following way: for 1,2- PB: trans-1,4 > cis-1,4 ⩾ 1,2 for 1,4- PB: cis-1,4 > trans-1,4 ⪢ 1,2 An increase in the limiting viscosity number was observed with increasing epoxy content in the 1,2-PB chain, but the opposite effect was observed for 1,4-PB. The solubility parameter, δ, for both kinds of epoxy polybutadiene was found to be similar ( 19.8 × 10 3 J 1 2 · m −3 2 ).