Thermal and mechanical properties of sorbitol‐based epoxy resin cured with quercetin and the biocomposites with wood flour

After a bio‐based epoxy resin, sorbitol polyglycidyl ether (SPE) was mixed with a flavonoid, quercetin (QC) in tetrahydrofuran at an optimized epoxy/hydroxy ratio 1/1.2, the obtained SPE/QC solution was mixed with wood flour (WF), prepolymerized at 150°C, and subsequently compressed at 170°C for 3 h to give SPE‐QC/WF biocomposites (WF content:0, 20, 30, 40 wt %). The tan δ peak temperature of SPE‐QC without WF (85.5°C) was higher than that of SPE cured with conventional phenol novolac (81.0°C). In addition, diglycidyl ether of bisphenol A cured with QC had a higher tan δ peak temperature (145.1°C) than that cured with PN (90.8°C). The tan δ peak temperatures (106–113°C) of SPE‐QC/WF biocomposites were significantly higher than that of SPE‐QC. The tensile modulus of SPE‐QC/WF biocomposites increased with increasing WF content. A lower wavenumber shift of carbonyl stretching absorption peak in the FTIR spectrum of SPE‐QC/WF as compared with that of SPE‐QC suggested that hydroxy group of woody component forms hydrogen bonding with carbonyl group of quercetin moiety. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Wood‐derived phenol novolaks and their wood/epoxy biocomposites

Guaiacol novolak (GCN) and wood‐tar creosote novolak (WCN) were synthesized by the reactions of wood‐derived guaiacol and creosote with formalin, respectively, and used as hardeners of sorbitol polyglycidyl ether (SPE). Thermal and mechanical properties of the cured resins (SPE‐GCN and SPE‐WCN) and their biocomposites with wood flour (WF) were compared with those of the materials prepared by using a petroleum‐based phenol novolak (PN). Although tan δ peak temperatures of SPE‐GCN and SPE‐WCN were lower than that of SPE‐PN, that (58.5–70.8°C) of SPE‐GCN/WF(40–50 wt %) was higher than that (56.6–57.0°C) of SPE‐PN/WF(40–50 wt %). Tensile moduli of all the biocomposites increased by the addition of WF, while tensile strengths were rather reduced. When the biocomposites with the same WF content were compared, tensile modulus of SPE‐GCN/WF was higher than that of SPE‐PN/WF. The 5% weight loss temperatures (346–291°C) of SPE‐GCN and SPE‐GCN/WF were comparable to those (338–284°C) of SPE‐PN and SPE‐PN/WF. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41347.     

Preparation and properties of biocomposites composed of glycerol‐based epoxy resins,tannic acid,and wood flour

After polyglycerol polyglycidyl ether (PGPE) and glycerol polyglycidyl ether (GPE) were mixed with tannic acid (TA) in ethanol and without solvent at epoxy/hydroxyl ratio 1/1, the obtained GPE‐TA and PGPE‐TA solutions were mixed with wood flour (WF), prepolymerized at 50°C, and subsequently compressed at 160°C for 3 h to give GPE‐TA/WF and PGPE‐TA/WF biocomposites with WF content 50–70 wt %, respectively. The storage moduli of the biocomposites in the rubbery state at more than 80°C were much higher than that of the control cured resins. The PGPE‐TA/WF composites had higher tensile modulus and rather lower tensile strength than PGPE‐TA. On the other hand, both the tensile modulus and strength of GPE‐TA/WF were much higher than those of GPE‐TA (2.4 GPa and 37 MPa). Those values of GPE‐TA/WF increased with WF content, became maximal values (5.1 GPa and 51 MPa) at WF content 60 wt %, and were lowered at 70 wt %. FE‐SEM analysis of the fractured surface of the biocomposites revealed that WF is tightly incorporated into the crosslinked epoxy resins. As a result of optimization of the epoxy/hydroxyl molar ratio for GPE‐TA/WF composite with WF content 60 wt %, the composite prepared at the ratio of 1.0/0.8 showed the highest tensile modulus and strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of biocomposites composed of epoxidized soybean oil,tannic acid,and microfibrillated cellulose

As a new biobased epoxy resin system, epoxidized soybean oil (ESO) was cured with tannic acid (TA) under various conditions. When the curing conditions were optimized for the improvement of the thermal and mechanical properties, the most balanced properties were obtained when the system was cured at 210°C for 2 h at an epoxy/hydroxyl ratio of 1.0/1.4. The tensile strength and modulus and tan δ peak temperature measured by dynamic mechanical analysis for the ESO–TA cured under the optimized condition were 15.1 MPa, 458 MPa, and 58°C, respectively. Next, we prepared biocomposites of ESO, TA, and microfibrillated cellulose (MFC) with MFC contents from 5 to 11 wt % by mixing an ethanol solution of ESO and TA with MFC and subsequently drying and curing the composites under the optimized conditions. The ESO–TA–MFC composites showed the highest tan δ peak temperature (61°C) and tensile strength (26.3 MPa) at an MFC content of 9 wt %. The tensile modulus of the composites increased with increasing MFC content and reached 1.33 GPa at an MFC content of 11 wt %. Scanning electron microscopy observation revealed that MFC was homogeneously distributed in the matrix for the composite with an MFC content of 9 wt %, whereas some aggregated MFC was observed in the composite with 11 wt % MFC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

All‐wood biocomposites by partial dissolution of wood flour in 1‐butyl‐3‐methylimidazolium chloride

After cedar‐derived wood flour (WF) and bark flour (BF) were mixed with 1‐butyl‐3‐methylimidazolium chloride (BMIC) at 100°C, the obtained compounds with BMIC content 40 wt % were compression‐molded at 210°C to give WF/BMIC and BF/BMIC composites, respectively. The BMIC contained in the composites was twice extracted with ethanol at 60°C to afford WF/BMIC‐E and BF/BMIC‐E biocomposites, which were subsequently annealed at 200°C for 24 h to produce WF/BMIC‐A and BF/BMIC‐A biocomposites. The Fourier transform infrared spectroscopic analysis revealed that WF has a higher content of cellulose and a lower content of lignin than BF does, and that the BMIC content diminished by the extraction process. The scanning electron microscopy analysis showed that woody particles joined together by the compression molding of WF/BMIC and BF/BMIC compounds, and that the extraction of BMIC roughened the surface and the annealing again smoothed the surface due to the fusion of the residual BMIC and woody particles. The XRD measurements indicated that the annealing enhanced the crystallinity of cellulose component. The tensile properties and 5% weight loss temperature of the biocomposites were considerably improved by the extraction of BMIC and further by the annealing. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Phenolic‐epoxy matrix curable by click chemistry—synthesis,curing, and syntactic foam composite properties

Alkyne functional phenolic resin was cured by azide functional epoxy resins making use of alkyne‐azide click reaction. For this, propargylated novolac (PN) was reacted with bisphenol A bisazide (BABA) and azido hydroxy propyloxy novolac (AHPN) leading to triazole‐linked phenolic‐epoxy networks. The click cure reaction was initiated at 40–65°C in presence of Cu₂I₂. Glass transition temperature (Tg) of the cured networks varied from 70°C to 75°C in the case of BABA‐PN and 75°C to 80°C in the case of AHPN‐PN. DSC and rheological studies revealed a single stage curing pattern for both the systems. The cured BABA‐PN and AHPN‐PN blends showed mass loss above 300°C because of decomposition of the triazole rings and the novolac backbone. Silica fiber‐reinforced syntactic foam composites derived from these resins possessed comparable mechanical properties and superior impact resistance vis‐a‐vis their phenolic resin analogues. The mechanical properties could be tuned by regulating the reactant stoichiometry. These low temperature addition curable resins are suited for light weight polymer composite for related applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41254.     

Effect of liquid isoprene rubber on dynamic mechanical properties of emulsionpolymerized styrene/butadiene rubber vulcanizates

The effect of liquid isoprene rubber (LIR) on the dynamic mechanical properties of emulsion‐polymerized styrene/butadiene rubber (ESBR) vulcanizates was investigated by temperature sweep using dynamic mechanical analysis. The introduction of LIR led to ESBR vulcanizates having higher loss factor (tan δ) in the temperature range ? 30 to 0 °C, and lower tan δ in the range 60 to 80 °C. A small amount of LIR‐403 (LIR with carboxyl groups) led to a significant change in tan δ: the addition of LIR‐403 (3 phr) led to a 7.5% increase in tan δ from ? 30 to 0 °C, and a 24.9% decrease in tan δ from 60 to 80 °C. It was found that the introduction of LIR increased the bound rubber content in the ESBR compound. Equilibrium swelling experiments showed that the crosslink density of the vulcanizates increased after the introduction of LIR‐403 or LIR‐50 (general purpose LIR). The change in tan δ from 60 to 80 °C was related to polymer–filler interactions. The characteristic constant of filler–ESBR matrix interaction (m) was calculated. At a given filler volume fraction, the increase in m in the presence of LIR could be well related to the decrease in tan δ from 60 to 80 °C. The influence of LIR on filler network in the ESBR compound was also investigated by strain and temperature sweeps using a rubber processing analyzer. Copyright © 2011 Society of Chemical Industry     

Thermal and mechanical properties of bio-based polymer networks by thiol-ene photopolymerizations of gallic acid and pyrogallol derivatives

Allylated pyrogallol (A3PG) and acrylated pyrogallol (Ac3PG) as bio-based trienes, and allylated gallic acid (A4GA) and acrylated allyl gallate (Ac3A1GA) as bio-based tetraenes were synthesized from pyrogallol and gallic acid, respectively. Thiol-ene photopolymerizations of the bio-based polyenes and a pentaerythritol-based primary tetrathiol (pS4P) at the allyl/SH ratio of 1/1 produced photo-cured resins (A3PG-pS4P, Ac3PG-pS4P, A4GA-pS4P and Ac3A1GA-pS4P). The FT-IR spectral analysis revealed that thiol-ene reactions of thiol/allyl and thiol/acryloyl groups smoothly proceeded. Gel fractions of acryl-based cured resins were a little higher than those of allyl-based cured resins. The swelling test and dynamic mechanical analysis revealed that GA- and acryl-based cured resins exhibited higher crosslinking densities than PG- and allyl-based cured resins, respectively. A higher order of tan δ peak temperature was Ac3PG-pS4P (48.3 ° C) > Ac3A1GA-pS4P (24.1 ° C) > A4GA-pS4P (22.1 ° C) > A3PG-pS4P (?7.8 ° C). Ac3PG-pS4P displayed the highest 5 % weight loss temperature, tensile strength and tensile modulus among all of the cured resins.     

Mechanical and dynamic mechanical properties of natural rubber blended with waste rubber powder modified by both microwave and sol–gel method

Waste rubber powder (WRP) was modified by microwave, sol–gel method, and both microwave and sol–gel method, respectively. The mechanical and dynamic mechanical properties of natural rubber (NR)/modified WRP composite were investigated. The influence of bis‐(3‐(triethoxysilyl)‐propyl)‐tetrasulfide (TESPT) content on curing characteristics and mechanical properties of vulcanizate was also studied. The results showed that NR/WRP modified by both microwave and sol–gel method composite owned the best mechanical properties. Rubber processing analyzer was used to characterize the interaction between silica and rubber chains and the dispersion of silica. With increase of TESPT content, the Payne effect decreased. Scanning electron microscopy indicated the coherency and homogeneity of in situ generated silica filled vulcanizate. Dynamic mechanical analyzer showed that NR/WRP modified by both microwave and sol–gel method composite with 5 phr TESPT exhibited the lower tan δ at temperature range of 50–80°C, compared with composite without TESPT and the higher tan δ at temperature of 0°C, compared with the conventional modification of WRP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Benzoxazine–epoxy copolymers: effect of molecular weight and crosslinking on thermal and viscoelastic properties

Bisphenol‐A‐based benzoxazine was copolymerized with epoxy and chain‐extended epoxies in order to study the effect of molecular weight on cured resin properties. Cure behaviour of the copolymers was studied using differential scanning calorimetry, which indicated a single exothermic curing peak at 248 °C. Dynamic mechanical thermal analysis was used to study the viscoelastic properties of the cured resins. A decrease in tan δ peak position and an increase in storage modulus and tan δ peak height were observed due to chain extension. Higher char yield was observed for the copolymer chain extended with tetrabromobisphenol‐A. Copyright © 2005 Society of Chemical Industry     

Rice husk‐derived porous carbon/silica particles as green filler for electronic package application

Bio‐based porous carbon/silica particles (denoted as RH‐carbon/silica) were successfully prepared from agricultural waste rice husk by using acid‐hydrothermal treatment and pyrolysis under nitrogen condition. As green filler, the cure behavior, thermal‐mechanical properties, and thermal conductivity of the epoxy‐carbon/silica biocomposites at different filler contents (5, 9, 17, 29 wt %) were characterized. Because of superior surface properties (surface area, porosity, and silica segment) and high content of carbon component in the RH‐carbon/silica, the characteristics of the biocomposites were significantly improved with the increase of the filler content. At 29 wt % of filler content, the epoxy biocomposites exhibit lower curing temperature (148 °C), lower CTE (42 ppm/°C), higher T_g (123 °C), higher storage modulus (4059 MPa), and higher effective thermal conductivity (0.29 W/mK). In brief, the RH‐carbon/silica particles that can serve not only as reinforcing agent but also as thermal transport medium used in epoxy composite, is a green and high‐performance filler for this purpose. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44699.     

Cross‐linking of ethylene‐octene copolymer (EOC) by dicumyl peroxide (DCP)

Ethylene‐octene copolymer (EOC) was crosslinked by dicumyl peroxide (DCP) at various temperatures (150–200°C). Six concentrations of DCP in range 0.2–0.7 wt % were investigated. cross‐linking was studied by rubber process analyzer (RPA) and by differential scanning calorimetry (DSC). From RPA data analysis real part modulus s', tan δ, and reaction rate were investigated as a function of peroxide content and temperature. The highest s'_max and the lowest tan δ were found for 0.7% of DCP at 150°C. Chain scission was analyzed by slope analysis of conversion ratio, X in times after reaching the maximum. Less susceptible to chain scission are temperatures in range 150–170°C and peroxide levels 0.2–0.5%. Heat of reaction was analyzed by DSC at various heating rates (5–40°C min⁻¹). It was found to be exothermic. By projection to zero heating rate, the reaction was found to start at 128°C with the maximum at 168°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characterization of modulus and glass transition phenomena in poly(L‐lactide)/hydroxyapatite composites

In order to study the dynamic‐mechanical properties of Poly(L‐lactide)/Hydroxyapatite (PLLA/HA) composites, two different molecular weight (inherent viscosity (η_inh): 4.0 (dL/g), and 7.8 (dL/g)) poly(L‐lactide) (PLLA) were synthesized by bulk polymerization and filled with 10%, 30%, and 50% (w/w) with medical grade HA (size range: 25–45 μm and Ca/P = 1.69). The plain PLLA polymers and PLLA/HA composites were compression molded and machined to yield 50 × 3 × 2 mm³ specimens. The composites were investigated by dynamic mechanical thermal analyzer (DMTA) of imposed bending load on rectangular specimens over a temperature range from 30 to 120°C using multiple frequencies (0.3–50 Hz). The results showed that the bending storage modulus (E′) of the composites increased linearly with the percentage of the filler, reaching at 37°C and 0.1 Hz about 2.5, 3.7 and 5.0 GPa with 10, 30 and 50% of HA respectively. The glass transition temperature, evaluated at the tan δ peaks, were in the range 70–80°C and 50–70°C for PLLA matrix and PLLA composites respectively. The activation energies at the glass transition temperature were calculated from the Arrhenius plot in the range of 102–111 Kcal/mol for the composites, whereas 132 and 148 Kcal/mol were found for low and high molecular weight of PLLA respectively. The content of amorphous phase was evaluated from the intensity of tan δ peak. Results showed that HA causes an amorphous phase with a greater mobility with respect to the pure PLLA.     

Thermal and viscoelastic properties of sequentially polymerized networks composed of benzoxazine,epoxy, and phenalkamine curing agents

By using different ratios of phenalkamine/epoxy (EP) and benzoxazine/epoxy (EB), copolymer networks have been prepared sequentially by partially curing at low temperature followed by a final cure at high temperature. A single exothermic peak was observed in the differential scanning calorimetry (DSC) for the high‐temperature curing. Dynamic mechanical thermal analysis showed a single tan δ peak, indicating no phase separation. The copolymer networks showed T_g values lower than the parent EB polymer network. Incorporation of EP in small percentage in the copolymer networks has improved the storage modulus and crosslink densities and the maximum value was observed for a sample containing 80% EB with respect to EP content. The thermal stability of the copolymer networks is better than that of the individual networks. The char yield value at 600°C increased with increasing EB percentage in the networks. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3956–3965, 2006     

Dynamic mechanical properties of styrene‐butadiene rubber vulcanizate filled with electron beam modified surface‐treated dual‐phase filler

The influence of the electron beam modification of a dual‐phase filler on the dynamic mechanical properties of styrene‐butadiene rubber (SBR) is investigated in the presence and absence of trimethylol propane triacrylate or triethoxysilylpropyltetrasulfide. Electron beam modification of the filler results in reduction of the tan δ at 70°C, a parameter for rolling resistance, and an increase in the tan δ at 0°C, a parameter for wet skid resistance of SBR vulcanizates. These modified fillers give significantly better overall performance in comparison with the control dual‐phase filler. This variation in properties is explained in terms of filler parameters such as the filler structure that leads to rubber occlusion and filler networking. These results are further corroborated using the master curves obtained by the time–temperature superposition principle. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2992–3004, 2003     

Imidazolium and deep eutectic ionic liquids as epoxy resin crosslinkers and graphite nanoplatelets dispersants

Two types of ionic liquids (IL), i.e., molecular ionic 1‐butyl‐3‐methylimidazolium thiocyanate ([BMIM]SCN) and deep eutectic solvent (DES) based on choline chloride and tris(hydroxymethyl)propane, as well as their mixture have been used as epoxy resin curing agents. [BMIM]SCN showed the highest catalytic activity toward epoxy resin polymerization as compared to up today used ILs. Curing process of epoxy resin was investigated at ambient temperature (storage time up to more than 60 days) and elevated temperatures (80–200°C) using rheometry and DSC techniques. Thermomechanical analysis allowed to determine an influence of IL type and content on composites crosslinking density, glass transition temperature, and tan δ values. Graphite nanoplatelets (GNP) was dispersed in DES and then in DES/IL/epoxy resin composition prepared, cast, and cured to obtain nanocomposite material. Electrical volume resistivity of the nanocomposites with 0.25–1 wt % GNP increased with nanofiller content up to the highest value of 2.8 × 10⁶ Ω · cm. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40401.     

Low dielectric thermoset. I. Synthesis and properties of novel 2,6‐dimethyl phenol‐dicyclopentadiene epoxy

A 2,6‐dimethyl phenol‐dicyclopentadiene novolac was synthesized from dicyclopentadiene and 2,6‐dimethyl phenol, and the resultant 2,6‐dimethyl phenol‐dicyclopentadiene novolac was epoxidized to 2,6‐dimethyl phenol‐dicyclopentadiene epoxy. The structures of novolac and epoxy were confirmed by Fourier transform infrared spectroscopy (FTIR), elemental analysis, mass spectroscopy (MS), nuclear magnetic resonance spectroscopy (NMR), and epoxy equivalent weight titration. The synthesized 2,6‐dimethyl phenol‐dicyclopentadiene epoxy was then cured with 4,4‐diaminodiphenyl methane (DDM), phenol novolac (PN), 4,4‐diaminodiphenyl sulfone (DDS), and 4,4‐diaminodiphenyl ether (DDE). Thermal properties of cured epoxy resins were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric analysis (DEA), and thermal gravimetric analysis (TGA). These data were compared with those of the commercial bisphenol A epoxy system. Compared with the bisphenol A epoxy system, the cured 2,6‐dimethyl phenol‐ dicyclopentadiene epoxy resins exhibited lower dielectric constants (～3.0 at 1 MHz and 2.8 at 1 GHz), dissipation factors (～0.007 at 1 MHz and 0.004 at 1 GHz), glass transition temperatures (140–188°C), thermal stability (5% degradation temperature at 382–404°C), thermal expansion coefficients [50–60 ppm/°C before glass‐transition temperature (T_g)], and moisture absorption (0.9–1.1%), but higher modulus (～2 Gpa at 60°C). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2607–2613, 2003     

Morphologies and properties of cured epoxy/brominated‐phenoxy blends

Morphologies of cured epoxy/brominated‐phenoxy blends were observed by scanning transmission electron microscopy (STEM) and energy dispersive X‐ray fluorescence spectroscopy (EDX). When brominated‐phenoxy content was 30 wt %, cocontinuous phase structures between cured epoxy and brominated‐phenoxy were found. Since every loss tangent (tan δ) curve as a function of temperature on dynamic mechanical analysis (DMA) showed 2 peaks at 128°C and 155°C respectively, cured epoxy phases and brominated‐phenoxy phases were incompatible together and T_gs of cured epoxy phases were not decreased. Tensile strength and tensile elongation of the cured blends were increased together. T‐peel adhesion strength and the lap‐shear adhesion strength were also increased together. These phenomena could be due to the cocontinuous structures consisted by the rigid cured epoxy phases of thermosets and ductile the brominated‐phenoxy phases of thermoplastics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1702–1713, 2007     

The influence of in situ modification of silica on filler network and dynamic mechanical properties of silica‐filled solution styrene–butadiene rubber

The influence of in situ modification of silica with bis‐(3‐(triethoxysilyl)‐propyl)‐tetrasulfide (TESPT) on filler network in silica filled solution SBR compound was investigated. In situ modification greatly increased the bound rubber content. TEM observation of silica gel showed that bridging and interlocking of absorbed chains on the surface of silica particles formed the filler network. Rubber processing analyzer (RPA) was used to characterize the filler network and interaction between silica and rubber by strain and temperature sweeps. In situ modification improved the dispersion of silica, and in the meantime, the chemical bonds were formed between silica and rubber, which conferred the stability of silica dispersion during the processing. Compared to the compound without in situ modification, the compound with in situ modification of silica exhibited higher tan δ at low strains and lower tan δ at high strains, which can be explained in terms of filler network in the compounds. After in situ modification, DMTA results showed silica‐filled SSBR vulcanizate exhibited higher tan δ in the temperature range of ?30 to 10°C, and RPA results showed that it had lower tan δ at 60°C when the strain was more than 3%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of crosslink structures on dynamic mechanical properties of natural rubber vulcanizates under different aging conditions

The effects of crosslink structures on the dynamic mechanical properties (DMPs) of unfilled and carbon black N330‐filled natural rubber (NR) vulcanizates cured with conventional (CV), semiefficient (SEV), and efficient (EV) cure systems and having about the same total crosslink densities were investigated before and after aerobic and anaerobic aging at 100°C. The three unfilled NR vulcanizates cured with the CV, SEV, and EV systems had about the same mechanical loss factor (tan δ) values at about 0°C but showed some apparent differences in the tan δ values in the order EV > SEV > CV at relatively high temperatures of 40–80°C before aging. However, N330‐filled NR vulcanizates gave higher tan δ values than the unfilled vulcanizates and showed little effect of the crosslink types on the tan δ at different temperatures over the glass‐transition temperature (T_g) before aging. Aerobic heat aging increased the T_g and tan δ values of the vulcanizates over a wide range of temperatures from ?80 to 90°C that was mainly due to the changes in the total density and types of crosslinks. The unfilled vulcanizates cured with the CV system showed the greatest change in DMP because of their poor resistance to heat aging. Aerobic heat aging of NR vulcanizates caused a more significant change in the DMP than anaerobic heat aging because of the dominant effect of the oxidative degradation during aerobic heat aging on the main‐chain structure, crosslink structures, and DMPs of the vulcanizates. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 710–718, 2001