Increase In Acrylonitrile Content Research Articles

Shape memory properties of dynamically vulcanized poly(lactic acid)/nitrile butadiene rubber (PLA/NBR) thermoplastic vulcanizates: The effect of ACN content in NBR

Morphology structure and interfacial interaction are crucial factors for shape memory thermoplastic vulcanizates. In this study, shape memory thermoplastic vulcanizates based on poly(lactic acid) (PLA) and nitrile butadiene rubber (NBR) were prepared through dynamic vulcanization. The influence of acrylonitrile (ACN) content on the morphology, compatibility, shape memory property, and mechanical property was investigated. A co‐continuous structure was observed. The interfacial compatibilization between PLA and NBR phases occurred, resulting in a significantly improved interface adhesion and interfacial interaction, which was confirmed by Fourier transform infrared spectroscopy. With such a novel structure, the PLA/NBR TPVs owned an excellent shape memory property and further improved with increasing ACN content of NBR, which could be explained that the cross‐linked continuous NBR phase provided a stronger recovery driving force. In the meantime, tensile strength and elongation at break of TPVs increased with increase in ACN content. It is concluded that the preparation of dynamically vulcanized thermoplastic vulcanizate with co‐continuous structure and strong interfacial adhesion is beneficial to obtain outstanding shape memory effect.

Manipulation of the properties of PLA nanocomposites by controlling the distribution of nanoclay via varying the acrylonitrile content in NBR rubber

Nanocomposites based on blends of polylactide (PLA), acrylonitrile butadiene rubber (NBR) and 4 wt% organically modified nanoclay (Cloisite 10A) were prepared via melt compounding. To investigate the influence of NBR acrylonitrile (ACN) content on the dispersion state and localization of nanoclay and micromorphology of the blends, three different NBRs with low (19%), medium (33%) and high (51%) ACN content were employed. Nanocomposites with low ACN NBR exhibited higher dispersion of clay nanolayers within the PLA matrix, whereas increase in ACN content gave rise to the localization of silicate platelets within the interface of two phases which was consistent well with the enhanced interfacial interaction between PLA and NBR phases that was evidenced by surface tension and melt rheology analysis. The size of dispersed NBR droplets decreased by the incorporation of organoclay into the composition of all PLA/NBR blends irrespective of the ACN content. However, the reduction in NBR droplet size by the nanoclay layers showed to be more pronounced for the nanocomposites based on high ACN rubber phase as a result of higher localization of nanoclay platelets within the interface of the PLA and NBR. All nanocomposites exhibited significant increase in elongation at break than simple blend counterparts, implying intensification of PLA and NBR interface by nanoclay incorporation.

The Swelling Properties of Nitrile Rubber with Different Acrylonitrile Contents in Cyclohexane Medium Research

By the research of swelling and mechanical properties of nitrile rubber with different acrylonitrile contents in cyclohexane medium, the influences of physical and mechanical properties with diffrent acrylonitrile contents is analyzed. The results indicated that: the quality of all the nitrile-butadiene rubbers with different acrylonitrile contents is increasing with the increase of soaking time. It increases rapidly in the first 24 hours then gently. With the increase of the acrylonitrile content, the increasing proportions of swilling quality is reduceing. But N40 cyclohexane performance is better relatively. After drying the three kinds of rubber in 110 degrees Celsius, all the qualities is lower than the original value. It means that in swelling process, the material in rubber is pulled out and the distance between the rubber molecules decreases. After swilling the three kinds of rubber, their hardness decreases and the decline proportion is reducing by the increase of acrylonitrile content. With different acrylonitrile contents and swilling times the nitrile rubber shows different mechanical properties. After soaking three kinds of rubber their tensile strengthes are on the decline by swilling time and their rates of permanent deformation are on the rise. It shows that as the swelling time extended, the mechanical properties descends and the corresponding indicators after soaked and dried is lower than the quantitative values after soaked. The study has a certain reference of design of ESPCP stator under certain operating conditions.

Effect of Copolymer Composition on the Dynamic Mechanical and Thermal Behaviour of Butyl Acrylate‐Acrylonitrile Copolymers

AbstractThis article reports data on the dynamic mechanical and thermal behaviour of butyl acrylate‐acrylonitrile copolymers and their variation with copolymer composition. The copolymers were prepared by emulsion polymerisation techniques, using potassium peroxodisulfate initiator at 80 ± 2 °C. Films were prepared from the latex by casting and analysed by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). For copolymer with 0.7 weight fraction of butyl acrylate the dynamic mechanical behaviour was identical to the synthetic rubber NBR (acrylonitrile‐butadiene rubber), such that the storage modulus shows a rapid decay with increasing temperature. The damping characteristics, as indicated by the tan δ value, increased as the weight fraction of butyl acrylate in the copolymer increased. The dynamic mechanical data has been analysed with the WLF‐Equation to study the time‐temperature relationship. The dynamic mechanical properties and glass transition data point to the formation of a copolymer, whose properties vary with acrylonitrile content. Thermogravimetric analysis revealed that weight loss occurring at a particular temperature decreases, along with the decomposition rate, with increase in acrylonitrile content. The activation energy (Ea) for the decomposition was calculated using the Coats & Redfern equation. When temperatures for 10% copolymer decomposition are compared from TGA data, the acrylonitrile rich copolymer starts decomposing at a lower temperature, but the rate of decomposition is slower and yields higher char yields.Effect of copolymer composition on the variation of tan δ (max) at a measuring frequency of 1 Hz.magnified imageEffect of copolymer composition on the variation of tan δ (max) at a measuring frequency of 1 Hz.

The effect of Freon vapour on fracture behaviour of styrene-acrylonitrile copolymer — I. Craze initiation behaviour

Environmental stress cracking behaviour of polystyrene and styrene-acrylonitrile copolymer (SAN) has been studied in Freon vapour in view of molecular weight and acrylonitrile content. The critical stress for craze or crack initiation was measured using three-point bending test and the surface damage was examined by scanning electron microscopy. The critical stress increased with an increase of acrylonitrile content in SAN copolymer, which suggests that the craze initiation stress has a good correlation with the solubility parameter difference between the polymer and crazing agent. However, molecular weight did not have any significant effects on the critical stress for craze initiation. For homopolystyrene, relatively large-sized craze was developed in Freon vapour due to the increase of softened layer thickness in the developed craze wall. As acrylonitrile content increases the development of craze is suppressed.

Effect of acrylonitrile content of styrene‐co‐acrylonitrile (SAN) on morphology and electrooptical properties of polymer/liquid crystal composite films

AbstractEffects of copolymer composition on morphology and electrooptical properties of polymer/liquid crystal (LC) (40/60 w/w) composite films were studied with styrene‐co‐acrylonitrile (SAN) of varying acrylonitrile (AN) content (6.3–35 wt %) and a cyanobiphenyl‐type liquid crystal (E8). The dimension of the LC domain in the composite film decreased with increase of AN content of SAN up to 30 and increased at 35 wt %. The contact angle of the film with an LC drop showed a similar trend; however, its minimum was obtained at 24% AN. Threshold voltage (Vth) and rise time (τR) increased, and decay time (τD) decreased with AN content up to 30%, and the tendency is reversed at 35%. The results were interpreted in terms of, possibly, a solubility parameter matching between SAN and LC. © 1993 John Wiley & Sons, Inc.

Studies on the thermodynamic compatibility of blends of poly(vinyl chloride) and nitrile rubber

Inverse gas chromatography has been used to investigate the thermodynamic compatibility of blends of poly(vinyl chloride) (PVC) and nitrile rubber (NBR) as a function of blend composition and acrylonitrile (AN) content of NBR. The values of the polymer-polymer thermodynamic interaction parameters ( X′ 23 and B 23) and the solubility parameter (δ) of the polymers and their blends were determined with the help of the measured retention data for various polar and non-polar probes in the pure and mixed stationary phases of these polymers. Out of all the probes studied only dioxane and cyclohexanone have similar δ values to those of the blends. The B 23 values for the PVC/NBR blends were ∼ −0.1 and −1.1 cal ml -1 depending on the AN content of NBR. Thus, the two polymers are fairly compatible and show increased compatibility with increase in AN content of NBR.

HPLC of synthetic polymers

Statistical copolymers of styrene and acrylonitrile have been separated by high performance precipitation chromatography according to the increase in acrylonitrile content. The separation mechanism was strongly depending on the combination of stationary phase and eluent composition. By applying a typical normal phase gradient from n-heptane (precipitation) to dichloromethane the polymers were adsorbed, after dissolution of the polar groups of the stationary phases. The elution curves became broader with increasing acrylonitrile content of the polymer. By the addition of 20% methanol to the dichloromethane the adsorption could be minimized and copolymer elution was dependent solely on solubility and independent of stationary phase polarity. Separation according to chemical composition was also possible without precipitation with a large pore silica and a normal phase gradient from dichloromethane to the same eluent containing 2.75% methanol.

NBR Vulcanizates Resistant to High Temperature and “Sour” Gasoline

Abstract NBR compounded in a conventional fuel hose tube formulation is markedly degraded by “sour” gasoline or “sour” ASTM Fuel C within 7 days at 40°C. Furthermore, the conventional NBR compound is not resistant to aging at 125°C. Use of an NBR designed for heat resistant compounding and an appropriate choice of compound greatly improve resistance to fuel which contains hydroperoxides. The preferred system for “sour” gasoline resistance and resistance to long term aging at 125°C is a cadmium oxide activated low sulfur-sulfur donor compound with silica as the principal filler. This vulcanizate is not much more affected after 7 days at 40°C by gasoline of peroxide number 50 than by clean gasoline, and is less affected by gasoline of peroxide number 200 than are other NBR vulcanizates. The balance of high and low temperature properties can be optimized by appropriate choice of plasticizer and acrylonitrile level. Aging resistance is somewhat improved by increase in acrylonitrile content, and fuel permeability is markedly decreased. Permeability to gasoline with 30 aromatic content can be changed appreciably by compounding, but the resistance to Fuel C with 50% aromatic content does not appear to respond to compounding changes. The stability of NBR vulcanizates in “sour” gasoline is reduced by copper salts and, to a lesser extent, by metallic copper. Bound antioxidant NBR does not appear to offer an advantage in “sour” gasoline resistance over heat resistant NBR compounded in a comparable formulation.