Reactive blends of epoxy resin (DGEBA) crosslinked by anionically polymerized polycaprolactam. II. Mechanical and electrical properties

Various reactive blends of diglycidyl ether of bisphenol A (DGEBA)/polycaprolactam were synthesized by anionic polymerization at 140°C, conducted by sodium hydride catalyst, a strong base, along with N‐acetyl caprolactam as a cocatalyst. The experiments were performed to study the effect of composition on the mechanical and electrical properties of the reactive blends, such as tensile properties, flexural properties, Izod impact strength, Rockwell hardness, and volume resistivity. It was observed that the DGEBA was crosslinked by the polycaprolactam through the rapid reaction of the oxirane group with amide nitrogen. The heat of reaction and heat‐deflection temperature of the reactive blends increased with increasing DGEBA content from 50 to 80 wt %, and increased dramatically above 70 wt % DGEBA content. The mechanical and electrical properties of the reactive blends increased with increasing DGEBA content from 50 to 80 wt %. Substantial increases in these properties were observed above 70 wt % DGEBA content in the reactive blends. SEM studies revealed that the reactive blends show a multiphase system with an increase in the DGEBA content from 50 to 80 wt % as the mixing of the two phases increased. The reactive blend Ep₈₀Ca₂₀, with 80 wt % DGEBA content, resembles a single‐phase system because of better mixing of the two phases; as a result, this reactive blend showed the highest mechanical and electrical properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 537–549, 2005     

Reactive Blends of Epoxy Resin (DGEBA) Cross-Linked by Anionically Polymerized Polycaprolactam: Adhesive Property and Chemical Resistance

Different ratios of epoxy resin (i.e., diglycidyl ether of bisphenol-A [DGEBA] and caprolactam) have been used to synthesize DGEBA/polycaprolactam reactive blends by carrying out anionic polymerization of caprolactam at 140°C. Anionic polymerization conducted by a strong base such as sodium hydride was used as a catalyst along with a cocatalyst such as N-acetyl caprolactam. The experiments were carried out to study the effect of composition on the adhesive property (i.e., lap shear strength and chemical resistance of the reactive blends). It was observed that the lap shear strength of the reactive blends increased with increasing DGEBA content from 50 to 70 wt% and increased drastically above 70 wt% DGEBA content with all metals (i.e., copper, aluminum, stainless steel, and mild steel). The lap shear strengths of all these reactive blends were observed to be maximum on mild steel. The study of chemical resistance indicates that the films of reactive blends Ep₇₅Ca₂₅ and Ep₈₀Ca₂₀ with 75 and 80 wt% DGEBA content showed better resistance to acids, alkalies, and solvents than the reactive blends Ep₅₀Ca₅₀ and Ep₇₀Ca₃₀ with 50 and 70 wt% DGEBA content. Among the solvents, methyl ethyl ketone, toluene, and methanol were found to be more attacking as compared to acetone, xylene, and ethanol.     

Study on the polymerization of ϵ‐caprolactam in the interlamellar spaces of [TEACOOH]–montmorillonite intercalations complex and its characterization

The polymerization of ?‐caprolactam between the interlamellar spaces of the [TEACOOH]–montmorillonite intercalations complex was attempted using Na–montmorillonite and 10‐carboxy‐n‐decyltriethylammonium bromide to achieve [TEACOOH]–polycaprolactam–montmorillonite, in which montmorillonite (inorganic polymer) is chemically bonded with the polycaprolactam (organic polymer). The results of X‐ray and IR analysis for the samples obtained after polymerization showed that the polymerization reaction has been successfully accomplished. For the purpose of studying the polymeric reaction product more precisely, we have isolated the polymerized product from the silicate layers and analyzed it with X‐ray diffractometer and IR spectrometer. Comparison of the results of X‐ray and IR analysis between the isolated polymer and the polymer that was synthesized by the reaction of ?‐caprolactam only with the organic cation without montmorillonite showed that both obtained polymers are the same compounds. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1904–1910, 2003     

Reactive blends of epoxy resin (DGEBA) crosslinked by anionically polymerized polycaprolactam: Process of epoxy cure and kinetics of decomposition

The curing reactions, kinetics, morphology, and thermal stability of the reactive blends of diglycidyl ether of bisphenol‐A (DGEBA) and polycaprolactam were studied by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis. DSC studies showed that the heat of reaction (ΔH) increased when the DGEBA content was increased from 50 to 80 wt % and increased drastically above 70 wt % DGEBA content because of an increase in the extent of crosslinking. The activation energy and pre‐exponential factor of cure reactions increased drastically with an increase in the DGEBA content above 70 wt % because of a drastic increase in crosslink density. The extent of curing reaction of polycaprolactam with DGEBA is dependent on the blend composition. The nucleophilic attack on oxirane ring by amide nitrogen of polycaprolactam is a dominant curing reaction in low DGEBA compositions, and another type of curing reaction with relatively large activation energy and pre‐exponential factor also occurred, which becomes dominant when the DGEBA content reaches above 70 wt %. FTIR studies also revealed that two types of reactions do exist during the curing of polycaprolactam with DGEBA. It was observed during SEM studies that the reactive blends show multiphase system and on increasing the DGEBA content from 50 to 80 wt %, the mixing of the two phases increased. The reactive blend Ep₈₀Ca₂₀ with 80 wt % DGEBA content exhibits a single‐phase system because of better mixing of the two phases. The results of thermogravimetric analysis also indicate that the initial degradation temperature (T_i), activation energy (E), and pre‐exponential factor (Z) increased with increasing DGEBA content from 50 to 80 wt % in the reactive blends and increased drastically above 70 wt % DGEBA content due to the higher crosslink density. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 687–697, 2004     

Polyamide 6/ethylene‐butylene elastomer blends generated via anionic polymerization of ε‐caprolactam: Phase morphology and dynamic mechanical behavior

This paper reports about the polymerization of ε‐caprolactam monomer in the presence of low molecular weight hydroxyl or isocyanate end‐capped ethylene‐butylene elastomer (EB) elastomers as a new concept for the development of a submicron phase morphology in polyamide 6 (PA6)/EB blends. The phase morphology, viscoelastic behavior, and impact strength of the polymerization‐designed blends are compared to those of similar blends prepared via melt‐extrusion of PA6 homopolymer and EB elastomer. Polyamide 6 and EB elastomer were compatibilized using a premade triblock copolymer PA6‐b‐EB‐b‐PA6 or a pure EB‐b‐PA6 diblock reactively generated during melt‐blending (extrusion‐prepared blends) or built‐up via anionic polymerization of ε‐caprolactam on initiating ? NCO groups attached to EB chain ends (polymerization‐prepared blends). Two compatibilization approaches were considered for the polymerization‐prepared blends: (i) the addition of a premade PA6‐b‐EB‐b‐PA6 triblock copolymer to the ε‐caprolactam monomer containing nonreactive EB? OH elastomer and (ii) generation in situ of a PA6‐b‐EB diblock using EB? NCO precursor on which polyamide 6 blocks are built‐up via anionic polymerization of ε‐caprolactam. The noncompatibilized blends exhibit a coarse phase morphology, either in the extruded or the polymerization prepared blends. Addition of premade triblock copolymer (PA6‐b‐EB‐b‐PA6) to a EB? OH /ε‐caprolactam dispersion led to a fine EB phase (0.14 μm) in the PA6 matrix after ε‐caprolactam polymerization. The average particle size of the in situ reactively compatibilized polymerization‐prepared blend is about 1 μm. The notched Izod impact strength of the blend compatibilized with premade triblock copolymer was much higher than that of the neat PA6, the noncompatibilized, and the in situ reactively compatibilized polymerization blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2538–2544, 2004     

Epoxy resin containing the poly(sily ether): Preparation,morphology, and mechanical properties

The poly(sily ether) with pendant chloromethyl groups (PSE) was synthesized by the polyaddition of dichloromethylsilane (DCM) and diglycidylether of bisphenol A (DGEBA) with tetrabutylammonium chloride (TBAC) as a catalyst. This polymer was miscible with diglycidyl ether of bisphenol A (DGEBA), the precursor of epoxy resin. The miscibility is considered to be due mainly to entropy contribution because the molecular weight of DGEBA is quite low. The blends of epoxy resin with PSE were prepared through in situ curing reaction of diglycidyl ether of bisphenol A (DGEBA) and 4,4′‐diaminodiphenylmethane (DDM) in the presence of PSE. The DDM‐cured epoxy resin/PSE blends with PSE content up to 40 wt % were obtained. The reaction started from the initial homogeneous ternary mixture of DGEBA/DDM/PSE. With curing proceeding, phase separation induced by polymerization occurred. PSE was immiscible with the 4,4′‐diaminodiphenylmethane‐cured epoxy resin (ER) because the blends exhibited two separate glass transition temperatures (T_gs) as revealed by the means of differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). SEM showed that all the ER/PSE blends are heterogeneous. Depending on blend composition, the blends can display PSE‐ or epoxy‐dispersed morphologies, respectively. The mechanical test showed that the DDM‐cured ER/PSE blend containing 25 wt % PSE displayed a substantial improvement in Izod impact strength, i.e., epoxy resin was significantly toughened. The improvement in impact toughness corresponded to the formation of PSE‐dispersed phase structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 505–512, 2003     

Kinetics of the in situ polymerization and in situ compatibilization of poly(propylene) and polyamide 6 blends

In previous articles, we reported on a novel reactive extrusion process to obtain a compatibilized blend of polymer A and polymer B. It consisted in polymerizing the monomer of polymer A in the presence of polymer B. A fraction of the latter contained initiating sites from which the polymerization of monomer A took place. As such, both polymer A and a graft copolymer of polymer A and polymer B were formed in the process. That process was called in situ polymerization and in situ compatibilization of polymer blends. Its feasibility was illustrated for in situ polymerized and in situ compatibilized poly(propylene) and polyamide 6 (PP/PA6) blends. The latter were prepared by activated anionic polymerization of ?‐caprolactam (CL) in the presence of PP in a batch mixer and a twin‐screw extruder, respectively. A fraction of the PP contained isocyanate groups from which PA6 grafts were formed. Sodium caprolactam (NaCL) was used as the catalyst and a diisocyanate compound was used as the activator. In this study, we report on the effects of various parameters on the kinetics of the anionic polymerization of CL in the presence of PP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1498–1504, 2004     

Tough polyamide 6/core–shell blends prepared via in situ anionic polymerization of ε‐caprolactam by reactive extrusion

In this study, the molten ε‐caprolactam (CL) solution of maleated styrene‐ethylene/butylene‐styrene block copolymer (SEBS‐g‐MA) and polystyrene (PS) containing catalyst and activator were introduced into a twin screw extruder, and polyamide 6 (PA6)/SEBS/PS blends were successfully prepared via anionic polymerization of CL by reactive extrusion. The mechanical properties measurements indicated that both the elongation at break and notched Izod impact strength of PA6/SEBS/PS (85/10/5) blends were improved distinctly with slight loss of tensile and flexural strength as compared to that of pure PA6. The images of transmission electron microscopy showed that a core–shell structure with PS core and poly (ethene‐co‐1‐butene) (PEB) shell was formed within the PA6 matrix. Fourier transform infrared was used to investigate the formation mechanisms of the core–shell structure. POLYM. ENG. SCI., 53:2705–2710, 2013. © 2013 Society of Plastics Engineers     

Morphology and thermal behavior of MCPA6/SAN blends prepared by anionic ring‐opening polymerization of ϵ‐caprolactam

In this article, a series of blends of monomer casting polyamide 6 and styrene‐co‐acrylonitrile (MCPA6/SAN) were prepared by in situ anionic ring‐opening polymerization of ?‐caprolactam. Their morphology and thermal behaviors were investigated by means of scanning electron microscope, differential scanning calorimeter, and wide‐angle X‐ray diffraction (WAXD), respectively. The SAN phase had much finer domain in MCPA6/SAN than that in the PA6/SAN blends prepared by melt blending of PA6 and SAN. All the melting and crystallization parameters of MCPA6/SAN blends decreased gradually with the increase of SAN content, while the melting temperature was almost unchanged. These results were due to the hydrolysis reaction of SAN that occurred during the anionic polymerization of ?‐caprolactam. In addition, WAXD results showed that only α crystal forms existed in the MCPA6/SAN blends. In addition, the mechanical property of MCPA6 was improved obviously by incorporating a certain amount of SAN. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1357–1363, 2006     

Preparation and characterization of polyimide‐g‐nylon 6 copolymers from nonfunctionalized polyimides

In this research, the anionic polymerization of ?‐caprolactam was carried out in the presence of small amounts of several different polyimides to generate polyimide‐g‐nylon 6 copolymers. The polyimides, which were prepared from 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and commercially available diamines with a one‐step method, were first dissolved in molten ?‐caprolactam. Phenylmagnesium bromide was then added at 120°C. Under these conditions, caprolactam anions were formed that attacked the five‐membered imide rings to form N‐acyllactam moieties, which activated the anionic polymerization of caprolactam. In essence, nylon 6 chains grew from the polyimide backbones. Probably because of a high activation energy, the process was relatively slow, requiring 1 h at 120°C. The introduction of 5 wt % polyimide into the graft copolymers produced significant increases in the tensile modulus and tensile strength in comparison with those of low‐ and high‐molecular‐weight nylon 6. The elongation to break, however, was reduced. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 292–299, 2006     

Blends of epoxy resins and polyphenylene oxide as processing aids and toughening agents 2: Curing kinetics,rheology, structure and properties

The curing behaviour, chemorheology, morphology and dynamic mechanical properties of epoxy ? polyphenylene oxide (PPO) blends were investigated over a wide range of compositions. Two bisphenol A based di‐epoxides ? pure and oligomeric DGEBA ? were used and their cure with primary, tertiary and quaternary amines was studied. 4,4′‐methylenebis(3‐chloro‐2,6‐diethylaniline) (MCDEA) showed high levels of cure and gave the highest exotherm peak temperature, and so was chosen for blending studies. Similarly pure DGEBA was selected for blending due to its slower reaction rate because of the absence of accelerating hydroxyl groups. For the PPO:DGEBA340/MCDEA system, the reaction rate was reduced with increasing PPO content due to a dilution effect but the heat of reaction were not significantly affected. The rheological behaviour during cure indicated that phase separation occurred prior to gelation, followed by vitrification. The times for phase separation, gelation and vitrification increased with higher PPO levels due to a reduction in the rate of polymerization. Dynamic mechanical thermal analysis of PPO:DGEBA340/MCDEA clearly showed two glass transitions due to the presence of phase separated regions where the lower T_g corresponded to an epoxy‐rich phase and the higher T_g represented the PPO‐rich phase. SEM observations of the cured PPO:DGEBA340/MCDEA blends revealed PPO particles in an epoxy matrix for blends with 10 wt% PPO, co‐continuous morphology for the blend with 30 wt% PPO and epoxy‐rich particles dispersed in a PPO‐rich matrix for 40wt% and more PPO. © 2014 Society of Chemical Industry     

Preparation and characterization of thermoplastic polyurethane elastomer and polyamide 6 blends by in situ anionic ring‐opening polymerization of ϵ‐caprolactam

The blends of thermoplastic polyether‐based urethane elastomer (TPEU) and monomer casting polyamide 6 (MCPA6) were prepared using ε‐caprolactam (CL) as a reactive solvent, and CL sodium as a catalyst at various TPEU contents (2.5–15 phr by weight). In situ anionic ring‐opening polymerization and in situ compatibilization of TPEU/MCPA6 blends were realized in one step. The dissociated TPEU chains acted as macroactivator to initiate MCPA6 chain growth from the TPEU chains. The formed block copolymers (TPEU‐co‐MCPA6), which have been confirmed by Fourier transform infrared spectroscopy and ¹H‐NMR analysis, improved the compatibility between TPEU and MCPA6. In addition, both differential scanning calorimetry and dynamic mechanical analysis studies revealed that the crystallinity temperature, melting temperature, the degree of crystallization, and the glass‐transition temperature of MCPA6 component remarkably shifted to a low temperature with increasing TPEU content. Mechanical properties demonstrated that the impact strength and the elongation‐at‐break of the blends significantly increased with the content of TPEU, whereas a progressive decrease occurred in tensile strength, flexural strength, and flexural modulus. WAXD spectra showed that only α‐form crystal of PA6 component existed in the TPEU/MCPA6 blends. Furthermore, scanning electron microscopes (SEM) of the cryo‐fractured surfaces confirmed a substantially improved compatibility, and reflected a seemly single‐phase morphology. POLYM. ENG. SCI., 46: 1196–1203, 2006. © 2006 Society of Plastics Engineers     

Natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) blends

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber using potassium persulfate as an initiator was carried out by emulsion polymerization. The rubber macroradicals reacted with MMA to form graft copolymers. The morphology of grafted natural rubber (GNR) was determined by transmission electron microscopy and it was confirmed that the graft copolymerization was a surface‐controlled process. The effects of the initiator concentration, reaction temperature, monomer concentration, and reaction time on the monomer conversion and grafting efficiency were investigated. The grafting efficiency of the GNR was determined by a solvent‐extraction technique. The natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) (NR‐g‐MMA/PMMA) blends were prepared by a melt‐mixing system. The mechanical properties and the fracture behavior of GNR/PMMA blends were evaluated as a function of the graft copolymer composition and the blend ratio. The tensile strength, tear strength, and hardness increased with an increase in PMMA content. The tensile fracture surface examined by scanning electron microscopy disclosed that the graft copolymer acted as an interfacial agent and gave a good adhesion between the two phases of the compatibilized blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 428–439, 2001     

Effect of dynamic vulcanization on properties and morphology of nylon/SAN/NBR blends: A new compatibilization method of nylon/ABS blends

Dynamically vulcanized blends of nylon, styrene–acrylonitrile copolymer (SAN), and nitrile–butadiene rubber (NBR) were examined for mechanical properties, Shore D hardness, Vicat softening temperature, impact process, and phase morphology. The effect of a curing system such as phenolic formaldehyde resins (PF), dicumylperoxide (DCP), and a sulfur system on the mechanical properties of the nylon/SAN/NBR blends was studied, and dynamic vulcanization with a PF system was found to lead to outstanding toughness of the blends. The effect of PF content on the mechanical properties, Shore D hardness, and heat resistance of the nylon/SAN/NBR blends was also investigated. With increasing PF content the notched‐impact strength and Vicat softening temperature (VST) of the nylon/SAN/NBR (50/25/25) blends evidently improved, but tensile strength and Shore D hardness of the blends changed slightly. It can be concluded that the nylon/SAN/NBR (50/25/25) blends dynamically vulcanized by high‐content PF can attain excellent comprehensive mechanical properties, especially supertoughness, at room temperature. SEM was used to investigate the effect of dynamic vulcanization on disperse‐phase particle size, particle size distribution, and phase morphology. It was obvious that disperse‐phase particle size decreased with an increasing PF content. Thermal behavior and miscibility of dynamically vulcanized nylon/SAN/NBR with PF were investigated by DMTA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2057–2062, 2003     

Epoxy toughening using low viscosity liquid diglycidyl ether of ethoxylated bisphenol‐A

Two new epoxy resins, diglycidyl ether of ethoxylated bisphenol‐A (BPA) with two and six oxyethylene units (DGEBAEO‐2 and DGEBAEO‐6) were synthesized and characterized. DGEBAEO‐6 was used to toughen the conventional epoxy resin diglycidyl ether of BPA (DGEBA). The blends of DGEBA with different amounts of DGEBAEO‐6 were cured by 4,4′‐diamino diphenylmethane (DDM), and their thermal and mechanical properties were examined. The DSC and DMA results presented that DGEBA/DGEBAEO‐6 blends exhibited a homogenous phase, and the glass transition temperature of the blends was inversely proportional to the content of DGEBAEO‐6. The impact strength of the cured blends was directly proportional to the content of DGEBAEO‐6, and reached five times higher than that of the neat DGEBA when 50 wt % DGEBAEO‐6 was used; the same impact strength was achieved for DDM‐cured DGEBAEO‐2. The viscosities of the blends decreased with increasing the DGEBAEO‐6 content, whereas the tensile and flexural strength and the thermal stabilities were not obviously affected. Scanning electron microscopic results confirmed that the plastic deformation inducing by the incorporated flexible oxyethylene units was responsible for the toughness improvement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characteristics of polymerization-filled polycaprolactams

A polymerization filling of a base in character monomer (ϵ-caprolactam) was carried out using fillers with solid acid character and catalytic action such as γ-alumina and calcium phosphate. The properties and structure of the polymerization-filled polycaprolactam obtained were studied. The following characteristics were determined: melting temperature, glass transition temperature, crystallization temperature, tensile strength, and dynamic elastic modulus. The advantages of the polymerization filling method are shown as compared to conventional methods for homogeneous production of polycaprolactam. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1255–1258, 1997     

Preparation and properties of polydimethylsiloxane/polyacrylate composite latex initiated by 60Co γ‐ray irradiation

In this study, polydimethylsiloxane (PDMS)/polyacrylate composite polymer latex was synthesized via polymerization of the acrylate monomer in the presence of vinyl‐containing PDMS seeded latex. The polymerization was initiated by ⁶⁰Co γ‐ray irradiation. The morphology of the PDMS/polyacrylate composite polymer latex was a core–shell structure with PDMS as the core and polyacrylate as the shell. There was an interpenetration layer between the PDMS core and the polyacrylate shell. The composition of the vinyl‐containing PDMS and the PDMS/polyacrylate composite latex were investigated with NMR and Fourier transform infrared spectroscopy, respectively. The effect of irradiation dose on the seeded emulsion polymerization conversion is discussed. Finally, the mechanical properties of latex film, such as water‐absorption ratio, tensile strength, pendulum hardness, and heat‐decomposed temperature, were tested. The results showed that the mechanical properties of the PDMS/polyacrylate film were remarkably improved when compared to the polyacrylate film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2732–2736, 2003     

Poly(phenylene ether)/epoxy thermoset blends based on anionic polymerization of epoxy monomer

Low molar mass poly (phenylene ether) (LMW‐PPE) with phenol‐reactive chain ends was used as modifier of epoxy thermoset. The epoxy monomer was diglycidylether of bisphenol A (DGEBA), and several imidazoles were used as initiators of anionic polymerization. The curing and phase separation processes were investigated by different techniques: Differential Scanning Calorimetry, Size Exclusion Chromatography, and Light Transmission measurements. The final morphology of blends was observed by Environmental Scanning Electron Microscopy and Transmission Electron Microscopy. The epoxy network is obtained by imidazole initiated DGEBA homopolymerization. Initial LMW‐PPE/DGEBA mixtures show an UCST behavior with cloud point temperatures between 40 and 90°C. PPE phenol end‐groups can react with epoxy, leading to a better interaction between phases. The curing mechanism and phase separation process are not influenced by the chemical structure of initiators, except when reactive amine groups are present. The phase inversion is observed at 30 wt % of PPE. The mixtures with amine‐substituted imidazole present important differences in the initial miscibility and curing process interpreted in terms of fast room temperature amine‐epoxy reaction during blending. Final domain size is affected by this prereaction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2678–2687, 2004     

Improved mechanical properties of NR/EPDM blends by controlling the migration of curative and filler via reactive processing technique

Simple blending of natural rubber/ethylene–propylene–diene rubber (NR/EPDM) generally results in inferior mechanical properties because of curative migration and their differences for filler affinity. In this work, the 70/30 and 50/50 NR/EPDM blends prepared by reactive processing techniques were investigated and compared with the simple, nonreactive blends. The reactive blend compounds were prepared by preheating EPDM, containing all curatives to a predetermined time related to their scorch time prior to blending with NR. For the 70/30 gum blends, four types of accelerators were studied: 2,2‐mercaptobenzothiazole (MBT), 2,2‐dithiobis‐ (benzothiazole) (MBTS), N‐cyclohexyl‐2‐benzothiazolesulfenamide (CBS), and N‐tert‐butyl‐2‐benzothiazolesulfenamide (TBBS). When compared with the simple blends, the reactive blends cured with CBS and MBTS showed a clearly improved tensile strength whereas the increase of tensile strength in the blends cured with TBBS and MBT was marginal. However, a dramatic improvement of ultimate tensile properties in the reactive 50/50 NR/EPDM blends cured with TBBS was observed when compared with the simple blend. For the N‐550‐filled blends at the blend ratios of 70/30 and 50/50, the reactive‐filled blends prepared under the optimized preheating times demonstrated superior tensile strength and elongation at break over the simple blends. The improved crosslink and/or filler distribution between the two rubber phases in the reactive blends accounts for such improvement in their mechanical properties. This is shown in the scanning electron micrographs of the tensile fractured surfaces of the reactive blends, which indicate a more homogeneous blend. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

PVC/TPU/NBR三元共混物的制备及性能研究

对PVC／热塑性聚氨酯（TPU）／SR三元共混物的性能进行研究，重点讨论NBR品种、TPU／NBR并用比、PVC聚合度、增塑剂DOP和硫化剂DCP用量对PVC／TPU／NBR三元共混物性能的影响。结果表明。PVC／TPU／NBR-3604三元共混物的物理性能较优；PVC／TPU／NBR-3604三元共混物的拉断伸长率和拉断永久变形均随着PVC聚合度的增大基本呈上升趋势；随着增塑剂DOP用量的增大，共混物的邵尔A型硬度、拉伸强度、撕裂强度和拉断永久变形均基本呈下降趋势，拉断伸长率增大；随着硫化剂DCP用量的增大。共混物的拉伸强度和拉断伸长率变化不大，撕裂强度基本呈逐渐减小的趋势。不同PVC／TPU／SR三元共混物的扫描电子显微镜照片表明，NBR与PVC和TPU的相容性较好。