Thermal properties of compatibilized and filled natural rubber/acrylonitrile butadiene rubber blends

The thermal behaviour of natural rubber/acrylonitrile butadiene rubber (NR/NBR) was studied using thermogravimetry (TG) and differential scanning calorimetry (DSC) in terms of blend ratio, crosslinking systems, fillers and compatibilizer (neoprene) were analyzed. The presence of NBR markedly increases the thermal stability of their blends and it lies in between NR and NBR. DSC studies revealed the thermodynamic immiscibility of the NR/NBR blends by the presence of two distinct glass transition temperatures and the immiscibility was prominent even in the presence of a compatibilizer.     

Effect of sol–gel derived in situ silica on the morphology and mechanical behavior of natural rubber and acrylonitrile butadiene rubber blends

Silica particles were generated and grown in situ by sol–gel method into rubber blends comprised of natural rubber (NR) and acrylonitrile butadiene rubber (NBR) at various blend ratios. Silica formed into rubber matrix was amorphous in nature. Amount of in situ silica increased with increase in natural rubber proportion in the blends during the sol–gel process. Morphology studies showed that the generated in situ silica were nanoparticles of different shapes and sizes mostly grown into the NR phase of the blends. In situ silica filled NR/NBR blend composites showed improvement in the mechanical and dynamic mechanical behaviors in comparison to those of the unfilled and externally filled NR/NBR blend composites. For the NR/NBR blend at 40/60 composition, in particular, the improvement was appreciable where size and dispersion of the silica particles into the rubber matrix were found to be more uniform. Dynamic mechanical analysis revealed a strong rubber–in situ silica interaction as indicated by a positive shift of the glass transition temperature of both the rubber phases in the blends.     

Studies on phase morphology and thermo-physical properties of nitrile rubber blends

The study deals with the morphological and thermal analysis of binary rubber blends of acrylonitrile-co-butadiene rubber (NBR) with another polymer. Either ethylene propylene diene terpolymer (EPDM), ethylene vinyl acetate (EVA), chlorosulphonated polyethylene (CSM), or polyvinyl chloride (PVC) has been selected for the second phase. Depending on the relative polarity and interaction parameter of the components, the binary blends showed development of a bi-phasic morphology through scanning electron microscopy (SEM). Use of different types of thermal analysis techniques revealed that these blends are generally incompatible excepting one of NBR and PVC. Derivative differential scanning calorimetry (DDSC), in place of conventional DSC, has been used to characterize the compatibility behavior of the blends. NBR–PVC shows appearance of only one glass transition temperature (T _g) averaging the individual T _g’s of the blend components. The partially missible blend of NBR and CSM shows a broadening of T _g interval between the phase components, while the immiscible blends of either NBR–EPDM or NBR–EVA do not show any change in T _g values corresponding to the individual rubbers of their blend. The experimental T _g values were also compared with those calculated theoretically by Fox equation and observed to match closely with each other. Studies have also been made to evaluate the thermal stability of these blends by thermo-gravimetric analysis (TG) and evaluation of activation energy of respective decomposition processes by Flynn and Wall method. Thermo-mechanical analysis (TMA) was found to be effective for comparison of creep recovery and dimensional stability of the blends both at sub-ambient as well as at elevated temperatures.     

Dynamic mechanical behavior of acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) blends

The dynamic mechanical behavior of uncrosslinked (thermoplastic) and crosslinked (thermosetting) acrylonitrile butadiene rubber/poly(ethylene‐co‐vinyl acetate) (NBR/EVA) blends was studied with reference to the effect of blend ratio, crosslinking systems, frequency, and temperature. Different crosslinked systems were prepared using peroxide (DCP), sulfur, and mixed crosslink systems. The glass‐transition behavior of the blends was affected by the blend ratio, the nature of crosslinking, and frequency. sThe damping properties of the blends increased with NBR content. The variations in tan δ_max were in accordance with morphology changes in the blends. From tan δ values of peroxide‐cured NBR, EVA, and blends the crosslinking effect of DCP was more predominant in NBR. The morphology of the uncrosslinked blends was examined using scanning electron and optical microscopes. Cocontinuous morphology was observed between 40 and 60 wt % of NBR. The particle size distribution curve of the blends was also drawn. The Arrhenius relationship was used to calculate the activation energy for the glass transition of the blends, and it decreased with an increase in the NBR content. Various theoretical models were used to predict the modulus of the blends. From wide‐angle X‐ray scattering studies, the degree of crystallinity of the blends decreased with an increasing NBR content. The thermal behavior of the uncrosslinked and crosslinked systems of NBR/EVA blends was analyzed using a differential scanning calorimeter. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1556–1570, 2002     

Impact modification of PA-6 and PBT by epoxy-functionalized rubbers

Glycidylmethacrylate (GMA) grafted apolar (ethylene/propylene/diene - EPDM) and polar (acrylonitrile/butadiene - NBR) rubbers were melt blended with polyamide-6 (PA-6) and polybutylene terephthalate (PBT). The toughness of the blends containing 5, 10 and 50 wt.% epoxy functionalized rubbers was assessed by various methods (notched Charpy, perforation impact) as a function of temperature (T=23 and −40°C). The notched Charpy tests served to deduce the fracture toughness (K_c) and energy (G_c) data. It was established that EPDM-g-GMA is a slightly better impact modifier than is NBR-g-GMA albeit the latter polar rubber is more compatible with both matrices than the less polar EPDM-g-GMA. This finding was traced to the difference in the glass transition temperature (T_g of NBR is higher than that of EPDM) and to the dispersion of the epoxy functionalized rubbers.     

The influence of nano silica particles on gamma-irradiation ageing of elastomers based on chlorosulphonated polyethylene and acrylonitrile butadiene rubber

The goal of this work was to study gamma irradiation ageing of rubber blends based on acrylonitrile butadiene rubber (NBR) and chlorosulphonated polyethylene rubber (CSM) reinforced by silica nano particles. The NBR/CSM compounds (50: 50, w/w) filled with different content of filler (0–100 phr) were crosslinked by sulfur. The vulcanization characteristics were assessed using the rheometer with an oscillating disk. The vulcanizates were prepared in a hydraulic press. The obtained materials were exposed to the different irradiation doses (100, 200, 300 and 400 kGy). The mechanical properties (hardness, modulus at 100% elongation, tensile strength and elongation at break) and swelling numbers were assessed before and after gamma irradiation ageing.     

Evaluation of the properties of some nitrile–butadiene rubber/polychloroprene mixes and vulcanizates

Nitrile–butadiene rubber (NBR) has been blended with polychloroprene (CR) in a weight ratio of 1:1. The vulcanizing systems in the blend formulations were varied to obtain non crosslinked CR embedded in vulcanized NBR and non crosslinked NBR embedded in vulcanized CR. The effects of these two different phases on the rheological and mechanical characteristics were evaluated. In addition, the dynamic compliance of the blends was measured over wide ranges of frequency and temperature. It has been found that the mechanical and rheological properties of the vulcanized blends depend on the type of vulcanizing system, its concentration and the presence of reinforcing filler. The mechanical properties of the blend containing N‐cyclohexyl‐2‐benzthiazyl sulphenamide/S as vulcanizing system suitable for NBR are higher than those of the blend containing non‐sulfur vulcanizing system (Zno/Mgo and ethylene thiourea) suitable for CR. Both types of rubber (CR and NBR) in the blend are incompatible as two glass transition temperatures have been observed. Copyright © 2000 John Wiley & Sons, Ltd.     

Studies on the nature of multiple glass transitions in low acrylonitrile,butadiene–acrylonitrile rubbers

A study of the occurrence of multiple glass transitions in acrylonitrile–butadiene rubbers (NBR) has been made. Copolymerization theory was used to predict the change in comonomer composition with conversion for comonomer ratios both above and below the calculated azeotropic composition of 64% butadiene/36% acrylonitrile by weight. The results of these calculations suggested that multiple glass transitions, which occur only in NBR of less than 36% acrylonitrile, were due to an incompatibility of copolymer species of divergent comonomer compositions. This was shown by differential thermal analysis to be the case for various experimental polymers of known comonomer composition. A series of NBR's was prepared by incremental addition of acrylonitrile monomer during polymerization, and the resultant glass transition temperatures were evaluated. Results obtained showed that experimental samples which had single glass transitions also had a much narrower spread of comonomer species than the corresponding rubber polymerized with the use of full initial charge of both monomers. The data indicate that NBR's having a single glass transition, regardless of acrylonitrile content, may be prepared by incremental addition of acrylonitrile monomer during polymerization. Existing copolymerization theory appears to be adequate for predicting incremental monomer addition schedules suitable for the polymerization of NBR's having a single glass transition.     

Thermal stability of CR/CSM rubber blends filled with nano- and micro-silica particles

The properties of filled polymers depend on the properties of the matrix and the filler, the concentration of the components and their interactions. In this research we investigated the rheological and mechanical properties and thermal stability of polychloroprene/chlorosulfonated polyethylene (CR/CSM) rubber blends filled with nano- and micro-silica particles. The density of the nano-silica filled CR/CSM rubber blends was lower than that of the micro-silica filled samples but the tensile strength and elongation at break were much higher. The nano-silica filled CR/CSM rubber blend has higher V _r0/V _rf values than micro-silica composites and show better polymer–filler interaction according to Kraus equation. The nano-silica filled CR/CSM rubber blends were transparent at all filler concentration, and have higher glass transition values than micro-silica filled compounds. The higher values of the glass transition temperatures for the nano- than the micro-filled cross-linked systems are indicated by DMA analysis. The nano-filled cross-linked systems have a larger number of SiO–C links than micro-filled cross-linked systems and hence increased stability.     

Miscibility and Mechanical Behavior of SAN/NBR Blends

Summary: Aiming the development of high toughness polymer materials, blends of poly(styrene-co-acrylonitrile) (SAN) and poly(butadiene-co-acrylonitrile) (NBR) rubbers, with contents of acrylonitrile (AN) varying from 21 to 45%, were prepared by casting, coprecipitation and monoscrew extrusion followed by injection molding. SAN/NBR blends, prepared in the compositions (w/w) 90/10, 80/20, 70/30, 60/40, and 50/50, were characterized by differential scanning calorimetry (DSC) and Izod impact tests. DSC analyses showed that blends with 33% AN NBR prepared by casting, and with 39% AN NBR prepared by coprecipitation, are partially miscible at 60/40, 70/30 and 80/20 (SAN/NBR) compositions and immiscible for 50/50 compositions. On the other hand, 90/10 SAN/NBR systems were totally miscible. The blends with 45% AN NBR prepared by coprecipitation showed partial miscibility to 50/50, 60/40, 70/30 and 90/10 compositions and total miscibility to 80/20 composition. The NBR addition results in a significant increase in the impact resistance, strongly dependent on the blend composition and the NBR AN content. The best result of impact resistance — 75.2 ± 8.6 (kJ · m⁻²) — was obtained for SAN/NBR 50/50, using 45% AN NBR. This value is 15.7 times bigger than that for pure SAN -4.8 ± 0.7 (kJ · m⁻²).     

Transition from miscibility to immiscibility in blends of poly(methyl methacrylate) and styrene-acrylonitrile copolymers with varying copolymer composition: a DSC study

The glass transition and the structural relaxation processes have been studied in blends of poly(methyl methacrylate) (PMMA) and styrene-acrylonitrile (SAN) copolymers with different acrylonitrile (AN) contents. The 50/50 wt.% blend of PMMA with the SAN copolymer containing 30 wt.% of AN is immiscible, while blends with copolymers containing between 13 and 26 wt.% of AN are miscible. Thus the upper limit of miscibility is between 26 and 30 wt.% of AN. The temperature dependence of the relaxation times of the conformational rearrangements of polymer chains around the glass transition have been determined in the blends and pure components by modelling DSC thermograms obtained after different thermal histories in each sample. The slope in the Arrhenius diagram logτ vs 1/T around the glass transition temperature is significantly smaller in the blend which is closer to the upper limit of miscibility than in the other miscible blends in which SAN copolymer contains less AN. The change of slope can be ascribed to a distribution in the glass transition temperatures of the different rearranging regions, reflecting the appearance of a microheterogeneity in the blend that cannot be detected as a double glass transition in the blend.     

Effect of electron beam irradiation on mechanical and thermal properties of waste polyamide copolymer blended with nitrile‐butadiene rubber

In the present study, the effect of electron beam irradiation on the morphological, thermal, and mechanical properties of waste polyamide copolymer (WPA‐66/6) blended with different contents of acrylonitrile butadiene rubber (NBR) were studied. The prepared blends were subjected to irradiation doses up to 150 kGy and the structural modifications were discussed; non‐irradiated blends were used as control. Mechanical properties, namely, tensile strength (TS), yield strength, elongation at break, and hardness, were followed up as functions of irradiation dose and degree of loading with rubber content. On the other hand, the influence of irradiation dose on the thermal parameters, melting temperature, heat of fusion, ΔH_m of the recycled PA copolymer, and its blend with NBR were also investigated. Copyright © 2009 John Wiley & Sons, Ltd.     

STUDIES ON SELF-VULCANIZING FLUOROELASTOMER/PHENOL HYDROXY SILICONE RUBBER BLENDS

Self-vulcanizing blends of phenol hydroxy silicone rubber(PHSR)and fluoroelastomer(FPM)were prepared. Vulcanized rubbers with lower glass transition temperature(T_g)were successfully obtained.The results of dynamic mechanical analysis(DMA)show that the vulcanized FPM/PHSR(10 phr)blend has only one T_g temperature,demonstrating the well compatibility between FPM and PHSR.The thermogravimetric analysis(TGA)demonstrates that the PHSR do little damage to the thermal stability of FPM.The vulcanization charact...     

Thermogravimetric Analysis and Thermal Ageing of Crosslinked Nitrile Rubber/Poly(ethylene-co-vinyl Acetate) Blends

The thermal behaviour of nitrile rubber (NBR)/poly(ethylene-co-vinyl acetate) (EVA) blends was studied by thermogravimetry. The effects of blend ratio, different crosslinking systems (sulphur, peroxide and mixed), various fillers (silica, clay and carbon black) and filler loading on the thermal properties were evaluated. It was found that the initial decomposition temperature increased with the addition of NBR to EVA. Among the various crosslinking systems studied, the peroxide cured system showed the highest initial decomposition temperature. This is associated with the high bond dissociation energy of C–C linkages. The addition of fillers improved the thermal stability of the blend. The mass loss at different temperatures and activation energy of degradation were also studied. The thermal ageing of these blends was carried out at 50 and 100°C for 72 h. It was seen that the properties are not affected by the mild ageing condition. Also, the peroxide cured system was found to exhibit better retention in properties, than other crosslinking systems. This revised version was published online in August 2006 with corrections to the Cover Date.     

Raman spectroscopy and thermal analysis of gum and silica-filled NR/SBR blends prepared from latex system

Natural rubber/styrene-butadiene rubber (NR/SBR) blends, with and without silica, were prepared by co-coagulating the mixture of rubber latices and various amounts of well-dispersed silica suspension. An attempt to predict blend compositions was made using Raman spectroscopy in association with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). It was found that the intensity of each Raman characteristic peak was strongly dependent on the blend composition, but there was no significant evolution with the presence of silica. Also, TGA results revealed an improvement in thermal stability of NR/SBR blends with increasing both SBR and silica contents due to the dilution effect. Two distinct glass transition temperatures (T_g) were observed in DSC thermograms of all blends, and their T_g values were independent on both blend composition and silica content. This indicated a physical blend formation, which agreed well with no shifts in Raman peaks of the blends in comparison with those of the individual rubbers. Linear regression with R² quality factor close to 0.99 was achieved when plotting intensity ratio at 1371/1302 cm^?1 versus blend ratios. On the other hand, the peak height ratio and heat capacity ratio from TGA and DSC analysis, respectively, yielded quadratic equations as a function of blend ratios.     

Preparation of high damping elastomer with broad temperature and frequency ranges based on ternary rubber blends

Based on the blends of chlorinated butyl rubber (CIIR), nitrile butadiene rubber (NBR) and chloroprene rubber (CR), a kind of high damping elastomer with broad temperature and frequency ranges is prepared. CIIR/NBR binary blend is prepared to take advantage of the immiscibility and the large difference in cross‐link density of the different phases caused by the curatives and accelerators migration. The dynamic mechanical analysis reveals that the binary blend was immiscible and its loss factor (tanδ) versus temperature curves show two separated and expanded loss peaks when compared with those of pure cured CIIR and NBR. In order to improve its damping properties at room temperature, the third component CR with the polarity between CIIR and NBR was blended into the binary blend. The resulted CIIR/NBR/CR ternary blend has gained effective damping properties (tanδ > 0.3) in the temperature range of ?86.4 to 74.6°C and the frequency range of 10^?2 to more than 10⁹ Hz. Other effects on the damping properties of the ternary rubber were also studied. Copyright © 2013 John Wiley & Sons, Ltd.     

Reinforcement of compatibilized NR/NBR blends by fly ash particles and precipitated silica

Effects of precipitated silica (PSi) and silica from fly ash (FA) particles (FASi) on the cure and mechanical properties before and after thermal and oil aging of natural rubber (NR) and acrylonitrile–butadiene rubber (NBR) blends with and without chloroprene rubber (CR) or epoxidized NR (ENR) as a compatibilizer have been reported in this paper. The experimental results suggested that the scorch and cure times decreased with the addition of silica and the compound viscosity increased on increasing the silica content. The mechanical properties for PSi filled NR/NBR vulcanizates were greater than those for FASi filled NR/NBR vulcanizates in all cases. The PSi could be used for reinforcing the NR/NBR vulcanizates while the silica from FA was regarded as a semi‐reinforcing and/or extending filler. The incorporation of CR or ENR enhanced the mechanical properties of the NR/NBR vulcanizates, the ENR being more effective and compatible with the blend. The mechanical properties of the NR/NBR vulcanizates were improved by post‐curing effect from thermal aging but deteriorated by the oil aging. Copyright © 2008 John Wiley & Sons, Ltd.     

Thermal characterization of nitrile butadiene rubber (NBR)/PVC blends

Summary Nitrile butadiene rubber (NBR) and NBR/PVC blends were produced using 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) or not as antioxidant. Controlled ozone degradation was performed in several samples. Thermal, compositional and morphological analysis was performed by means of differential scanning calorimetry, thermogravimetry, chemical analysis and scanning electron microscopy. Thermogravimetry analysis shows four mass loss processes related to plastizicer, complex rubber degradation and metallic oxides and other additives. In NBR (NBR/PVC blends) the onset temperature of the first degradation process varies between 227-231°C (259-262°C) and the apparent activation energy between 26 and 36 kJ mol^-1 (36-57 kJ mol^-1), the NBR/PVC samples non degraded presents the higher thermal stability.     

界面粘结对聚氯乙烯/丁腈橡胶共混物脆韧转变的影响

应用丙烯腈（ＡＮ）含量不同的丁腈橡胶（ＮＢＲ）与聚氯乙烯（ＰＶＣ）共混，研究了界面粘结对ＰＶＣ／ＮＢＲ共混物脆韧转变的影响．结果表明：当基体层度Ｔ相等时，过强的界面粘结，使ＰＶＣ／ＮＢＲ共混物的冲击强度降低，并且其产生脆韧转变的临界基体层厚度Ｔｃ减小．界面粘结对于聚合物共混物的增韧行为具有直接的影响．损伤区分析给出：随着界面粘结强度增大，空洞化过程受阻，减弱能量的耗散，并且不利于诱导剪切屈服损伤的产生，因而不利于增韧；但是界面粘强度过小，意味着共混物的相容性太差，致使分散相粒径过大，也不利于增韧．所以对增韧来讲，共混物的界面粘结强度存在一个最佳范围．     

Influence of chlorosulfonated polyethylene network structure on poly(acrylonitrile-styrene-acrylate)/poly(α-methylstyrene-acrylonitrile) blends: Mechanical properties,morphologies, glass transition behavior and heat resistance

Acrylonitrile-styrene-acrylate terpolymer and poly(α-methylstyrene-acrylonitrile) (ASA/α-MSAN, 25/75) with different loadings of chlorosulfonated polyethylene (CSM) were prepared via melt blending, with goals of toughening modification of ASA/α-MSAN blends and maintaining the heat resistance simultaneously. The results revealed CSM had excellent toughening effect at room temperature. At 0 °C, impact strength increased linearly with CSM content. However, toughening effect of CSM was undesirable at −30 °C. The temperature-dependent toughening efficiency of CSM was significantly related to its glass transition behavior. Scanning electron microscope analysis on cryo-fractured surfaces revealed the toughening mechanism was the formation of CSM toughening network in matrix, which was further confirmed by selective extraction tests. The formation of CSM network could lead to increased glass transition temperature of the blends at the low temperature region according to dynamic mechanical thermal analysis. Different from other toughening agents, CSM network uncompromised the heat resistance of ASA/α-MSAN blends.