Effect Of Vulcanization Research Articles

Polypropylene/ethylene propylene diene monomer/cellulose nanocrystal ternary blend nanocomposites: Effects of different parameters on mechanical, rheological, and thermal properties

AbstractIn the present study, the effect of dynamic vulcanization, mixing sequence, and cellulose nanocrystal (CNC) content on mechanical, rheological, and thermal properties of the polypropylene/ethylene propylene diene monomer (PP/EPDM/CNC) ternary blend‐nanocomposites was investigated. Significant reduction in tensile and yield strengths occurred for the un‐vulcanized PP/EPDM blend compared to PP. Vulcanization and adding CNC have compensated for the decrease in tensile and yield strengths of the un‐vulcanized blend. The tensile and yield strengths of the vulcanized samples had almost a slight uptrend by adding CNC. Elongation at break for both nanocomposites types had slight changes compared to that of PP/EPDM‐thermoplastic vulcanizates and all of them were approximately in the range of 600%–700%. Adding CNC before or after vulcanization had the same effect on the trend of Young's modulus and the higher the amount of CNC, the greater the increase in Young's modulus. Incorporating and increasing the amount of CNC improved the impact strength of all samples, especially when added after vulcanization. Rheological measurements showed that vulcanization of PP/EPDM resulted in frequency independence of storage modulus and a more sharp increment in Complex viscosity. Also, the more CNC content, the more dramatic changes occurred in complex viscosity, especially in DV‐CNC nanocomposites. Differential scanning calorimeter analysis showed that all samples had higher crystallinity which was more significant for Dynamic vulcanization (DV)‐CNC nanocomposites. Scanning electron microscope images also indicated that the addition of CNC increased fracture surface roughness for all samples ignoring their preparation sequence.

A relative study of the effect of static and dynamic vulcanization upon shape memory nature of thermally actuated peroxide crosslinked polyolefinic blends

AbstractThermally actuated peroxide crosslinked shape memory polyolefinic blends of EOC and EPDM has been developed. Effect of static and dynamic vulcanization process on the shape memory character has been pursued in detail. Shape memory properties study at 60°C reveals that statically vulcanized blend and dynamically vulcanized blend are superior in terms of shape fixity character and shape recovery behavior, respectively. Breakage of lower percentage of crystalline structure gives higher percentage of shape fixity for the statically vulcanized blend. In a parallel way, statically vulcanized blend shows better stress–strain properties also. On the other hand, higher degree of crosslinked network structure results higher shape recovery percentage for the dynamically vulcanized blend. Similar to shape recovery characteristics, dynamically vulcanized blend shows better thermal stability and higher percentage of gel content.

Effect of Dynamic Vulcanization on Properties of Linear Low Density Polyethylene/Natural Rubber Filled with Calcium Carbonate

The effect of dynamic vulcanization with different loading of calcium carbonate (CaCO3) on linear low density polyethylene/natural rubber using N,N’-m-phenylene bismaleimide (HVA-2) vulcanized and dicumyl peroxide (DCP) vulcanized as a cross-linker were investigated. Optimum ratio of LLDPE/NR blends was chosen is 70/30 in this study. Calcium carbonate loading was varied at 0wt%, 5wt%, 10wt% and 20wt% as filler in LLDPE/NR blends. The study showed that the tensile properties of the un-vulcanized LLDPE/NR blends were deteriorated with increasing in CaCO3 content. The dynamic vulcanization approach by using the HVA-2 and DCP dynamic vulcanization agents was applied on the LLDPE/NR blends in order to compensate the deterioration properties caused by the incorporation of CaCO3. According to the results, the addition of HVA-2 and DCP showed the composites were better in water resistance and tensile properties as compared to the standardized counterpart. The morphological analysis by using the scanning electron microscopy (SEM) found out that the interfacial adhesion and dispersion of CaCO3 was improved in both vulcanization systems.

Dynamic Vulcanization of Polypropylene / Natural Rubber Blends Filled with Cyperus Odoratus

A new thermoplastic blend was developed using polypropylene (PP) with natural rubber (NR) as the base material. The natural filler is added to enhance the properties of PP/NR blend. The first series was to compare the properties of PP/NR blend with different filler loading. Second series was to investigate the effect of dynamic vulcanization on the properties of PP/NR blend filled with Cyperus Odoratus with the intention of improving the blend properties. Process development, tensile properties, thermal analysis, FTIR analysis and morphological characterization of blends were investigated with the variation of the conditions of the blend. The increasing filler loading decrease the tensile properties of the PP/NR blend and it shows in the morphology study of the blend. Dynamic vulcanization of the blend resulted in improved tensile and thermal properties compared to unvulcanized counterpart. This result is confirmed by the SEM study that showed better dispersion of NR in the PP matrix and improved adhesion between the two phases.

Vital effect of sufficient vulcanization on the properties of Ni-Co-S/graphene composites for supercapacitor

Ni-Co-S/graphene-based composites have a broad prospect in the application of supercapacitors. Whether the vulcanization process is sufficiently performed seriously affect the performance of the composites. Here, a series of transition metal sulfide/graphene composites is synthesized through a two-step hydrothermal method by introducing different sulfur sources selected from organic (thiourea and thioacetamide) to inorganic (sodium sulfide and sodium thiosulfate). Both thioacetamide and sodium sulfide can vulcanize Ni-Co hydroxy-carbonate precursor to form the Ni-Co sulfide, but the other two cannot. And the Ni-Co-S/graphene composites synthesized by using sodium sulfide as sulfur source possess the best performance in asymmetric supercapacitor with an initial specific capacitance of 178.1 F g−1, and a capacitance retention of 89.47% after 10,000 cycles at 10 A g−1. The excellent stability is related to the ideal hollow structure with rich electrochemical active sites, and dispersed constituents of the Ni-Co-S on the surface of rGO.

Термомеханические свойства нанокомпозитов на основе клиноптилолита и сополимера этилена с гексеном

The effect of the concentration of clinoptilolite on the thermomechanical properties of nanocomposites based on a copolymer of ethylene with hexene is studied. The concentration of clinoptilolite is varied from 0.5 to 20 wt %. It is found that an increase in the softening temperature of the nanocomposite from 113 to 126°C is observed with the increase in the concentration of the filler. The separate effect of crosslinking vulcanizing agents, dicumyl peroxide and sulfur, on the main physical and mechanical properties of the nanocomposites is shown. It is found that compounds containing 5 wt % clinoptilolite and 0.5 wt % dicumyl peroxide possess the highest values of ultimate tensile stress. The effect of sulfur vulcanization on the properties of the nanocomposites is investigated. In contrast to peroxide vulcanization, sulfur vulcanization promotes a certain increase in the heat resistance of the samples while maintaining the ultimate tensile stress, elongation at break, and melt flow at a quite good level. The thermomechanical properties of the nanocomposites vulcanized by the peroxide and sulfur are investigated.

Dual effect of dynamic vulcanization of biobased unsaturated polyester: Simultaneously enhance the toughness and fire safety of Poly(lactic acid)

To overcome the inherent flammability and brittleness of biobased and biodegradable poly(lactic acid) (PLA) so as to broaden its applications, a new strategy, introducing a dynamic vulcanization of biobased unsaturated polyester (BUP) in PLA substrates, has been employed to improve the fire safety and toughness of PLA simultaneously for the first time. For toughened PLA by BUP (TPLA), only 20 wt% ammonium polyphosphate (APP) needs to be added for achieving UL 94 V-0 rating and a limiting oxygen index (LOI) value of 27%. In contrast, for PLA without BUP, 20 wt% of APP (PLA/APP20) cannot endow it with a fire safety, and only UL 94 V-2 rating and a LOI value of 24% are obtained. Interestingly, the elongation at break and the notched Izod impact strength of TPLA/APP20 are 107.1% and 15.9 kJ/m2, respectively, being 13.7 and 8.8 times than that of neat PLA; the complex viscosities of TPLA/APP are much higher than that of PLA/APP even near the burning temperature, which can reduce the fluidity and avoid further diffusion of flame with the flow of melt. Further, an open cone calorimeter test, XPS, FT-IR and SEM have been used to find out how the toughening treatment affect the fire safety of PLA/APP. All the results demonstrate that for PLA with low melt viscosity and heavy dripping during burning, the toughening treatment via dynamic vulcanization can quickly promote continuous dense char formation benefiting improving the flame retardant efficiency of APP.

Evaluation of Vulcanization Depth of Thick Rubber Products by Terahertz Radiation

An evaluation of the vulcanization depth of thick rubber products was performed using terahertz (THz) time-domain spectroscopy. The sample herein was a styrene -butadiene rubber (SBR)-based cylindrical products with a 35 mm diameter and 20 mm thickness, vulcanized under 10 MPa of pressure and a temperature of 150 °C. To clarify the vulcanization effect, no carbon black (CB) was included in the sample, because its apparent THz absorbance is extremely large compared with that of polymers and other additives. To perform the THz absorbance imaging, the thick sample was sliced parallel to the upper and lower heating plates of the cure mold into six thin specimens a few millimeters thick. Herein, the samples cured for two different cure times (T90 and T100) were investigated and compared. It was found that the coefficient of variation (CV) of the THz absorbance in the sliced specimens was suitable for evaluating the cure condition in the thick sample. The THz imaging results were used to compare the crosslinking densities of the sliced specimens using the Flory-Rehner equation.

The effect of PPA on performances and structures of high-viscosity modified asphalt

Polyphosphoric acid (PPA) was used to improve the physical and rheological properties of high-viscosity modified (HVM) asphalt and decrease the styrene–butadiene–styrene (SBS) content. The sample preparation technique was optimized further by blending furfural extract oil and asphalt in advance. With the optimized preparation process, the major physical and rheological properties of HVM asphalt were improved further by adding the same amount of PPA comparing with other preparation processes; however, the motive viscosity, toughness and tenacity of HVM asphalt still depended on the SBS content. Various rheological tests were adopted to investigate the effect of PPA on the rheological behaviours of HVM asphalt before and after ageing. The suitable gelation accused by PPA not only improved the high-temperature rheological performances of HVM asphalt, but increased the low-temperature rheological performances. Morphology observation by using optical microscope showed the effect of vulcanization and ageing on the outline and distribution of SBS in HVM asphalt. Fourier transform infrared analysis indicated the difference of SBS content under different modifications. Thermal analysis displayed the effect of PPA on the thermodynamic behaviours of HVM asphalt and demonstrated the declined ageing susceptibility of HVM asphalt after PPA modification.

The effect of dynamic vulcanization on the morphological and mechanical properties of the toughened poly (lactic acid)/epoxidized natural rubber

Poly (lactic acid)/epoxidized natural rubber (PLA/ENR) was prepared by using counter-rotating twin-screw extruder. For dynamic vulcanization process, ENR was compounded with 3 phr of N, N’-m-phenylenebismaleimide (HVA-2) as a crosslinking agent. The aim of this study is to determine the effect of unvulcanized and dynamically vulcanized of ENR on the properties of PLA/ENR blend. The blending of PLA with ENR was prepared with the various composition of ENR (0 wt% to 30 wt%). The morphology and mechanical properties of the blends were investigated by using scanning electron microscope (SEM), tensile test, and impact test. The unvulcanized blend produced a co-continuous morphology of PLA and ENR and the dynamically vulcanized blend shows the dispersed ENR rubber particles in PLA continuous matrix. For both systems, the tensile strength value was dropped with the increasing amount of ENR content. The impact strength of both systems shows the maximum value at 20 wt% of ENR content. However, dynamically vulcanized PLA/ENR blend shows a better tensile strength and impact strength value as compared with unvulcanized blend.

Synergetic effect of epoxy resin and carboxylated nitrile rubber on tribological and mechanical properties of soft paper-based friction materials

Abstract In order to improve tribological and mechanical properties of rubber-based wet friction materials, five kinds of paper-based friction materials were prepared using the mixture of different ratios of epoxy resin (EP) and carboxylated nitrile butadiene rubber (XNBR) as a dual matrix. When the proportion of XNBR exceeds 40% in binder, the wear rate of paper-based friction materials begins to reduce, while the tensile strength, toughness and dynamic friction coefficient remain unchanged. In the end, the wear rate of the material for 80% XNBR in binder is reduced by 29% compared with material for 40%. This is attributed to ionic crosslinking network involved with divalent substances in fillers combining with the vulcanization effect of EP on XNBR.

Fabrication and mechanical properties of γ-ray radiation vulcanized hnbr with high recovery after compression

This article focused on the effect of radiation vulcanization on the mechanical properties and the aging resistance performance in hot oil of the hydrogenated nitrile butadiene rubber (HNBR). The effect of absorbed dose on micromorphology, mechanical properties and thermal stability of radiation vulcanized HNBR (RV-HNBR) was investigated. The fractured surface of the HNBR systems was inspected in scanning electron microscope (SEM). SEM investigation showed that the cross-linked structure was more complete by the γ-ray radiation than heat vulcanization. A study of the compression permanent set property and tensile property of γ-ray radiation vulcanized HNBR was presented. Compared with heat vulcanized HNBR (HV-HNBR), RV-HNBR exhibited outstanding compression recovery performance after immersed in IRM 903 oil at 150 °C for 24 h. The compression-resilience property and the dimensional stability were improved with the absorbed dose increasing. When the absorbed dose was 250 kGy, the compression permanent was 40.1%. The good resistance to hot oil bring radiation vulcanized HNBR to meet many of the most stringent sealing application requirements.

Effects of polymerized sulfur on rheological properties, morphology and stability of SBS modified asphalt

The objective of this study was to investigate effects of polymerized sulfur on viscosity functions, morphology and storage stability of SBS modified asphalt, as compared to elemental sulfur. Viscosity functions including complex viscosity, steady flow viscosity and dynamic viscosity were measured by dynamic shear rheometer (DSR) and Brookfield viscosity rheometer. The morphology and microstructure of modified asphalt were observed using fluorescence microscopy and Fourier Transform Infrared spectroscopy (FTIR). The results revealed that the increment in viscosity of modified asphalt containing polymerized sulfur was slower than that of elemental sulfur. Vulcanization rate decreases with the increase of polymerized sulfur, i.e. delayed vulcanization effect. In morphology, large polymer domains progressively transform to the fine dispersed SBS phase with smaller dimensions as the elongation of mixing time; whereas a fine polymer phase was found for elemental sulfur at the initial stage of mixing, which is significant evidence of delayed vulcanization. Moreover, the FTIR results verify the decrease of unsaturation of poly-butadiene block and the formation of CS bond. Viscosities of asphalt with polymerized sulfur were always lower than those of elemental sulfur and decreased with the increase of polymerized sulfur content. SBS phase domain vulcanized by polymerized sulfur is larger than that of elemental sulfur and tends to become larger with the increase of polymerized sulfur content. Lastly, SBS modified asphalt with higher level of polymerized sulfur shows the improved storage stability.

Fracture toughness and deformation mechanism of un-vulcanized and dynamically vulcanized polypropylene/ethylene propylene diene monomer/graphene nanocomposites

Polypropylene (PP)/Ethylene propylene diene monomer (EPDM)/graphene nanocomposites were prepared by melt mixing process via an internal mixer (Brabender plasti-corder). The effect of multi-layer graphene (MLG), few-layer graphene (FLG) and dynamic vulcanization on microstructure and fracture toughness of the multicomponent system were investigated. The morphology of the samples were characterized by wide X-ray diffraction (WAX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which revealed that graphene mostly was dispersed into the PP phase and the size of the dispersed phase (EPDM) was decreased with incorporation of graphene, more specifically FLG, in both un-vulcanized and vulcanized systems. The concept of essential work of fracture (EWF) was used to analyze the fracture toughening behavior and deformation mechanism of PP/EPDM/graphene nanocomposites. In the case of un-vulcanized polymer, the total work of fracture improvements (+23.5%) was noted for PP/EPDM/FLG in which FLG platelets with higher aspect ratio were used, showed the better dispersion and higher ductility fracture behavior compared with MLG. The fracture mechanism of un-vulcanized samples occurs due to debonding and/or cavitation of the dispersed phase (EPDM), while for vulcanized samples the fracture mechanism proceeds through creation of nanovoids and cavitation in the dispersed phase which lead to the shear yielding of PP matrix. The graphene platelets acted as crack initiation sites as well as obstacles against crack propagation. The results of microstructure properties along with the fracture analysis data showed that the aggregated MLG platelets act as stress concentration and facilitate the initiate cracks while the FLG platelets hindered the crack path. Improvement in toughness behavior and matrix resistance were attributed to higher voiding stresses and finer dispersion of graphene.

Retraction Note to: Effect of dynamic cross-linking on melt rheological properties of isotactic polypropylene (iPP)/ethylene–propylene diene rubber (EPDM)/nitrile rubber (NBR) elastomeric blends

An attempt has been made to study the melt rheological properties of uncross-linked and dynamically cross-linked isotactic polypropylene (iPP)/ethylene-propylene-diene rubber (EPDM)/Nitrile rubber (NBR) elastomeric blends, at blending ratios 10–40 wt.%, EPDM/NBR are reported. Blends were prepared by melt blending in an internal mixture at 190 °C and various rheological parameters have been evaluated at 220 °C by single screw capillary rheometer. Cross-linking was performed with resole type dimethylol phenolic resin. The effects of (i) blends composition (ii) shear stress/shear rate on melt viscosity (iii) flow characteristics and shear sensitivity at processing (iv) melt elasticity of the extrudate and (v) dynamic vulcanization effect on the processing characteristics were studied. It was found that the melt viscosity increases with the increasing EPDM/NBR concentration and decrease with increasing intensity of the shear mixing of all the blend compositions. As compared to the uncross-linked blends, dynamically cross-linked blends displayed high pseudoplastic behavior and provides unique processing characteristics that enable to perform well in both injection molding and extrusion process. The high viscosity at low shear rate provides the integrity of the extrudate during extrusion, and the low viscosity at high shear rate enabling low injection pressure and less injection time. Also the low die-swell characteristics of cross-linked blends also gave high precision for dimensional control during processing (extrusion).

Impact behavior of CNT-filled PP/EPDM blends: effect of dynamic vulcanization and PP-g-MA compatibilizer

The impact strength and crystallite structure of un-vulcanized and dynamically vulcanized polypropylene/ethylene-propylene terpolymer (PP/EPDM) blends and polypropylene/ethylene-propylene terpolymer/carbon nanotube (PP/EPDM/CNT) blend nanocomposites with and without maleic anhydride-grafted polypropylene (PP-g-MA) were studied. The results showed that incorporation of EPDM increased the impact toughness of PP matrix by promoting debonding and cavitation of rubber particles. Dynamic vulcanization increased the interfacial adhesion leading to superior impact strength. Incorporation of CNT into PP/EPDM blends changed the crystallization behavior of the PP matrix and further increased the impact resistance. Morphological observations on impact-fractured surfaces indicated that dominant failure modes of CNTs in blend nanocomposites with and without PP-g-MA are pulling out and breakage of nanotubes, respectively. While the PP-g-MA had a negative effect on the impact strength of PP, the results demonstrated that its presence enhanced the impact strength of the blends and blend nanocomposites mostly via enhancing the adhesion between the PP and EPDM particles and improving the dispersion of CNTs in the matrix, respectively. The former decreases the rubber particle size and the latter decreases the size of CNT aggregates and crystallites.

Nanomechanics and Origin of Rubber Elasticity of Novel Nanostructured Thermoplastic Elastomeric Blends Using Atomic Force Microscopy

PeakForce quantitative nanomechanical mapping is an advanced atomic force microscopy (AFM) technique for measuring the mechanics of a sample surface by probing at the nanoscale. This nanomechanical mapping is performed in novel nanostructured thermoplastic elastomer (TPE) and thermoplastic vulcanizate (TPV) consisting of nanolevel dispersion of fluoroelastomer phase (60–80 nm) in the continuous polyamide matrix. Both in the case of TPE and TPV, elastic modulus and adhesion force (between the tip and sample surface) from the continuous matrix phase to the dispersed rubber particle through the nanometric interface (4–5 nm) are analyzed. The effect of dynamic vulcanization on the nanomechanical properties of the interface and the dispersed rubber phase of the blends is discussed. The origin of rubber elasticity in thermoplastic elastomeric blends in spite of the plastic as the continuous phase is proposed. It was shown for the first time that the interconnected dispersed rubber phase through the thin rubber ligament of 4–12 nm width in the thermoplastic matrix significantly contribute to the rubber elasticity in TPE and TPV. image

In situ dispersion and compatibilization of lignin/epoxidized natural rubber composites: reactivity, morphology and property

ABSTRACTLignin, a naturally occurring polymer, was viewed as a potential substitute of carbon black for reinforcing rubber materials. However, it shows no reinforcing effect if directly mixed with rubber. In this study, lignin was in situ dispersed at submicrometer size and highly compatible with epoxidized natural rubber (ENR) by using a high‐temperature dynamic heat treatment (HTDHT). Rheology analysis indicated that the ring opening reaction between lignin and ENR occurred at 160°C or above, which was further confirmed by infrared spectroscopy. Due to the consumption of acidic groups of lignin by ENR, the retardant vulcanization effect of lignin was weakened. Morphology observation and dynamic mechanical analysis demonstrated the perfect lignin dispersion and the strong interactions between lignin and ENR. The mechanical properties of the lignin/ENR composites were significantly improved by using HTDHT. Compared to the directly mixed rubber composites, the tensile strength and tear strength of the heat treated rubber composites filled with 40 phr lignin were increased by 114% and 23%, respectively. Especially, the 300% modulus of the heat treated rubber composite was increased by ca. 400%. X‐ray diffraction results indicated that the reinforcement of the composites originated from the presence of lignin rather than the strain‐induced crystallization of ENR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42044.

Effects of dynamic vulcanization on the kinetics of isothermal crystallization in a miscible polymeric blend

Is it possible to determine the state of phase separation using the free energy of folding parameter?

Mechanical Properties, Swelling Behavior and Morphology Properties of Dynamic Vulcanized Low Density Polyethylene/Natural Rubber/Water Hyacinth Fibers Composites

The effect of dynamic vulcanization and fiber loading on properties of low density polyethylene (LDPE)/natural rubber (NR)/water hyacinth fibers (WHF) were investigated. In this study, the vulcanized thermoplastics were obtained by in situ dynamic curing of LDPE/NR/WHF composites. The LDPE/NR/WHF composites with different fiber loading were prepared by using Brabender mixer at 180 °C with the rotor speed of 50 rpm. The results showed that dynamic vulcanized LDPE/NR/WHF composites gave a higher tensile strength, Young’s modulus, elongation at break but lower molar sorption than unvulcanized LDPE/NR/WHF composites. The SEM micrographs also displayed better fibers dispersion and the crosslink formation in dynamic vulcanized LDPE/NR/WHF composites indicated better interfacial bonding among fibers and matrix compared to unvulcanized LDPE/NR/WHF composites.