NBR/phenolic interpenetrating networks (IPNs) offer a wide variety of mechanical and physical properties at moderately high temperature. This temperature stability along with oil and fuel resistance property has made IPNs appropriate candidates for various applications. In the present work, NBR compounds containing 5, 7 and 12 phr of Novolac, as a curable phenolic resin was formulated using a two-roll mill. Low and high acrylonitrile NBR; KNB 35L and Europrene N4560 were selected in the compound and the same condition of mixing was applied in the blend preparation stage. Curing test, followed by a cooling period and the stress relaxation test were carried out consecutively and automatically in a rubber process analyzer. The samples presented various relaxation times. The relaxation curves were well estimated by Maxwell model and the Prony coefficients were determined. Furthermore, compression test was performed on the samples, so that the set or permanent deformation of each sample was measured. The results of both tests have indicated that by adding phenolic resin into the NBR matrices, the viscoelastic behavior of the compounds become more elastic, to the detriment of the viscous component. This phenomenon would be due to IPN formation in the compounds. In addition, by increasing the phenolic resin content in the compounds, the difference between maximum and minimum torque (M H-M L) value became greater, which is an indicator of higher cross-link density and IPN formation. Swelling test results confirmed more extensive cross-links in the compounds by addition of more resin into the compound.

Compatibilizer is used for improvement of interfacial interaction, mechanical properties and processability of polymer blends. In this study, the effect of phthalic anhydride (PAH), succinic anhydride (SAH) and maleic anhydride (MAH) in vulcanizable compositions of the melt mixed acrylonitrile butadiene rubber/poly(vinyl chloride) (NBR/PVC) in different proportions were investigated. PAH, SAH and MAH were used to improve compatibility of NBR/PVC blends. These additives increased the interfacial interaction between NBR and PVC phases confirmed by the scanning electron microscopy (SEM) study of fracture surfaces. The results were compared to those for control type (no compatibilizer added) NBR/PVC formulation. The developed compositions were studied by rheometric and mechanical properties. Also, in this work, we investigate the effects of mixing procedure (Brabender Plasticorder and Haake rheometer) and NBR form (powder and bale) on the final properties of NBR/PVC blends. It is argued that NBR/PVC blends with NBR powder prepared in the Haake rheometer have higher stabilization torque and tensile properties than NBR/PVC blends with NBR bale and have lower properties than the blends which were prepared in Brabender Plasticorder with NBR powder. It is observed that the increasing effect of NBR powder in mechanical properties is owing to fine particle size and high surface area that are well interacted with PVC.

Thermoplastic elastomeric materials have become important because they have many properties of vulcanized rubbers and can be rapidly fabricated as thermoplastics. in this work, selected grade of polypropylene (PP) was modified with dimethylol-phenolic resin and then it was melt-mixed with acrylonitrile-butadiene rubber (NBR) for several weight ratios. After sufficient mixing time additional phenolic resin was added to mixing chamber and the blends were dynamically vulcanized. In order to study the effects of the compositions and dynamic vulcanization on the physical and mechanical properties, simple blends of unmodified polypropylene and NBR were also prepared. The results show that dynamically vulcanized blends have higher tensile strength, elongation at break, solvent and oil resistance.  

Quantifying fire hazards in natural areas and their spatial patterns are essential for developing appropriate fire management strategies, especially in countries with limited historical data on past fires. In this study, a fire hazard map for the Andika region of Iran was constructed by examining the correlation of past fires with the criteria of topography, meteorology, land cover, and human factors. The locations of eight-year fire points from 2013 to 2020 of Nova satellite sensor VIIRS were received and the fire map of each was constructed using the NBR (Normalized Burn Ratio). The wildfire events distribution maps were randomly divided into 70 and 30 percent ratios for training (modeling) and testing (validation) data, respectively. Using the frequency ratio, a fire hazard map of the region was created. Four fire hazard areas ranging from very high to low were identified. The results of past fires and frequency ratio model showed that in the study area, land cover (2. 982), elevation (2. 778), and annual precipitation (2. 419) have the greatest prediction rate and influence on fire occurrence. The results also showed that a large proportion of past fires (71. 37%) were located in high and very high-risk areas. The evaluation results of the area under the curve method showed an accuracy of 71. 1% using evaluation data and 74. 4% using training data, which can be considered desirable. The small differences between the validation results using test and training data indicate an unbiased fire hazard map.

In this study, polyamide 6 (PA6)/ nitrile butadiene rubber (NBR) based hybrid-nanocomposites reinforced with calcium carbonate and organo-clay as nanofillers in various content of 1, 3 and 5 phr were prepared and characterized. The nanocomposite samples were prepared through the melt processing method in an internal mixer. The effect of rubber phase (NBR) content (10, 30, and 50 wt. %), calcium carbonate content (1, 3, and 5 phr), and organo-clay content (1, 3, and 5) was investigated on morphology and mechanical properties of the nanocomposites. The mechanical properties were evaluated by tensile, flexural, and Charpy impact tests. The results showed that adding the NBR reduces the tensile strength, tensile modulus, flexural strength, and flexural modulus, and increases the impact strength. Introducing the nano-clay and calcium carbonate improves the tensile and flexural strength, tensile and flexural modulus, and decreases the impact strength. The nano-clay content from 1 to 3 phr improved the impact strength.

The effect of organo-montmorillonite (OMMT) on the properties of acrylonitrile butadiene rubber/polyvinyl chloride/OMMT (NBR/PVC/OMMT) nanocomposites is studied. Four different types of organo-modified OMMT were examined in NBR/PVC blend systems and an optimum type of OMMT (FMR11) was found by characterizing the mechanical properties of NBR/PVC/OMMT hybrids. Then, NBR/PVC/OMMT nanocomposites with various amounts of FMR11 were prepared by direct mechanical blending. The dispersion of OMMT layers and morphology of the nanocomposites were determined by X-ray diffraction (XRD) and transmission electron microscope (TEM). Mechanical properties, solvent resistance and thermal stability of nanocomposites were also investigated. TEM revealed that OMMT layers disperse uniformly in NBR/PVC matrix in nano-scale. XRD patterns revealed the intercalation of polymer chains inside the OMMT layer gallery. The tensile strength and tear strength of nanocomposites based on 6.0 phr OMMT improved by 50.0% and 36.9%, respectively compared to gum NBR/PVC hybrids. Solvent resistance properties of nanocomposites showed improvement with higher OMMT contents, which contribute to the excellent barrier effect of OMMT layers.