Effect Of Vulcanization Research Articles

Effect of Compound Curing System on Properties of NBR/CM Blends

Abstract The effects of conventional vulcanization (CV), semi-efficient vulcanization (SEV), efficient vulcanization (EV), and equilibrium cure (EC) on the properties of nitrile rubber (NBR)/ chlorinated polyethylene (CM) blends were studied. The results showed that the SEV system had a faster vulcanization rate, larger torque, and larger vulcanization temperature coefficient, and the EC system had reversion resistance and a longer vulcanizing period. The modulus of the SEV system, the tensile strength of the CV system, and the elongation at the break of the EC system were high. The SEV system had good seawater and oil resistance; SEV > EV > CV >EC appeared in G’ and G”. The tanδ of the SEV system was larger than that of the EC system, but the tanδ of CV and EV system was close.

A Study on the Preparation of a Vulcanizing Mixture and Its Application in Natural Rubber Latex.

The traditional preparation process of natural rubber latex requires tedious treatment of a variety of rubber additives. In this paper, a new process of wet mixed grinding was used to prepare a reinforced vulcanization mixture and a rapid vulcanization effect. The effect of different amounts of vulcanization mixtures on the mechanical properties of natural latex film was studied, and the pre-vulcanization process of latex and the vulcanization process of film were optimized. The results showed that with the increase in the amount of vulcanization mixture, the tensile strength increased from 5.96 MPa to 29.28 MPa, and the tear strength increased from 7.59 kN/m to 52.81 kN/m. When the vulcanization temperature of the latex film is heated from 80 °C to 100 °C, the vulcanization time is shortened by 5~6 times. The new vulcanization mixture prepared in this work has the characteristics of simple production and fast vulcanization speed, which provides a new solution for the development of the latex product industry.

Insight into the stabilization/solidification of Cd, Pb and Zn in MSWI FA by three stages: Vulcanization, precipitation and bio-oxidation

Bio-oxidation has been perceived as a promising treatment for the solidification/stabilization (S/S) of heavy metals (HMs) in mining soils. Nonetheless, no research exists on the integration of the iron-sulfur oxidizing bacterium Acidithiobacillus ferrooxidans as a microbial agent into the treatment of municipal solid waste incineration-fly ash (MSWI-FA). The effect of vulcanization (Stage I), precipitation (Stage II) and bio-oxidation (Stage III) on the stabilization of HMs in MSWI-FA was unexplored. This study investigated the stabilization effects of Stage I and Stage II by utilizing Na2S and FeSO4 to adjust the Fe/S ratio. The findings contributed to identifying suitable methods to enhance the stabilization effect of the microbial agent on MSWI-FA (Stage III). The results indicated that the vulcanization (Stage I) increased the compressive strength of MSWI-FA to 1.87 MPa when the concentration of Na2S reached 0.03 mM. The leaching toxicity of Cd, Pb, and Zn at 28 days after Stage II was 0.12 mg/L, 0.99 mg/L, and 356 mg/L, respectively, which improved by 96.3%, 94.8%, and 26.9% compared to the untreated samples. The compressive strength of the samples peaked at 1.97 MPa when the Fe/S ratio was 0.25 (precipitation (Stage II)). Despite the inhibitory effect of MSWI-FA on microbial activity, the leaching toxicity of Cd, Pb, and Zn in the presence of Acidithiobacillus ferrooxidans decreased to 0.07 mg/L, 0.17 mg/L and 97.3 mg/L at 28 days after Stage III, with no significant further increase in compressive strength. This study suggested that bio-oxidation utilizing iron sources may change the formation of iron oxides, thereby impacting the mechanical and chemical properties of MSWI-FA-based materials. The treatment sequence of vulcanization, precipitation and bio-oxidation proved effective in immobilizing HMs, particularly Pb, Cd, and Zn in MSWI FA. This research highlighted the potential of employing this technique to treat MSWI FA, yet it is essential to identify suitable reaction systems with appropriate additives to further enhance the long-term effectiveness and mechanical properties of MSWI-FA-based materials.

The effect of physical compatibilization and dynamic vulcanization on the properties of thermoplastic vulcanizates derived from polypropylene and natural rubber blends

This interesting study investigated the effect of Maleic Anhydride-grafted-Polypropylene/Epoxidized Natural Rubber (PP-g-MA/ENR) as a compatibilizing agent (CA) on the properties of a 30/70 Polypropylene/Natural Rubber PP/NR blends. The effect of dynamic vulcanization with sulfur-donors (i.e.: Tetramethyl thiuram disulfide (TMTD) and 4,4 Dithiodimorpholine (DTDM)) which were used as vulcanizing agents was also reported. Several formulations of TPVs with different concentrations of CA (from 5 to 15 phr) were prepared by mixing in the molten state using a Haake Rheocord 90. The structural analysis of dual compatibilizer was examined by FTIR spectroscopy. The rheological behavior was examined using Haake Rheocord 90. The mechanical properties were determined by the tensile measurements. The dynamic mechanical thermal properties were investigated by DMA. A morphological examination was conducted using SEM Microscopy, respectively. FTIR analysis confirmed reactions between the MA group in PP-g-MA and the epoxy groups in ENR, resulting in ENR-grafted PP with an ester and acid-based linkage. The Haake plastograms revealed a proportional increase in the final mixing torque value with the increasing content of CA. The mechanical results exhibited higher values in terms of tensile strength and Young’s modulus for the TPVs containing CA compared to un-compatibilized ones. The compatibilized TPV blends exhibited a noteworthy increase in storage modulus and a notable decrease in loss tangent values with the CA concentration increased. Furthermore, the TPVs show two distinct-phase morphologies. That is, the TPV with CA showed the presence of smaller vulcanized rubber particles dispersed within the PP matrix, a phenomenon that becomes more pronounced with higher CA contents.

Construction of a rough surface in EPDM/CB composite through peroxide curing: A mechanism for optimizing physico‐mechanical properties in automotive paint‐compatible applications

AbstractThis study investigates the profound impact of vulcanization methods on ethylene–propylene–diene monomer (EPDM) composites, with a particular focus on elucidating significant findings and achievements. Exploring eight composites, including sulfur and peroxide‐cured variations, we conducted an in‐depth evaluation of the crucial physico‐mechanical properties of the composites. The study extends to encompass the effects of vulcanization on heat aging parameters, providing a comprehensive understanding of the materials' resilience. Utilizing thermogravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy, our research delves into the processes, revealing critical insights into the thermal behavior and composition of the composites. Paint compatibility, a pivotal aspect in automotive applications, was rigorously examined through four different test methods. Surface morphology, investigated through scanning electron microscopy and atomic force microscopy, yielded valuable findings on the role of vulcanization in shaping surface roughness and enhancing paint compatibility. Additionally, the quantitative measurement of surface energy using the sessile drop method provided a deeper understanding of the adhesion properties. The findings distinctly underscore the superiority of peroxide‐cured composites, marking a significant stride toward their potential to revolutionize automotive applications. This research not only contributes to the knowledge base but also sets a foundation for advancements in EPDM composite materials, positioning them as key players in driving innovation within the automotive industry.Highlights Developed a peroxide‐cured EPDM rubber composite with a rough surface. A rough surface is more paint‐compatible than a smooth surface. The roughness of peroxide‐cured EPDM is greater than that of sulfur‐cured one. Peroxide curing introduces more polar functional groups and cross‐links. Peroxide‐cured EPDM has higher thermal stability than sulfur‐cured EPDM.

Strain-induced crystallization behavior and tensile properties of natural rubber with different vulcanization bond types

The crosslinking network structure is a crucial factor influencing the properties of natural rubber. Therefore, investigating the impact of different vulcanization bond types on the strain-induced crystallization behavior and properties of natural rubber can provide a theoretical foundation for producing high-performance natural rubber. In this study, diverse curing systems were employed to produce vulcanized natural rubbers with varying crosslink types. The crosslinking network structures of the vulcanized rubbers were analyzed using the tube model theory. Additionally, the effects of vulcanization bonds on strain-induced crystallization behavior and tensile properties were examined through in-situ X-ray diffraction and a tensile testing machine. The results revealed that the vulcanizate with monosulfidic bonds, formed under the effective vulcanization (EV) system, primarily comprised chemical crosslinking networks, resulting in a high tensile modulus, low elongation at break, and low tensile strength. Conversely, the vulcanizate under the conventional vulcanization (CV) system exhibited a distinct entanglement network impact compared to the chemical crosslinking network, resulting in a smaller tensile modulus but the highest elongation at break and the largest tensile strength. These differences stemmed from the distinct roles of vulcanization bonds within the crosslinking network. Specifically, the relatively short monosulfidic bond quickly reached the critical degree of orientation for crystallization during stretching, leading to higher crystallinity under the same strain. However, its shorter length caused earlier fracture during stretching, resulting in network heterogeneity, reduced elongation at break, and lower tensile strength. On the other hand, the longer polysulfidic bond underwent fracture recombination during stretching, with slower orientation and delayed crystallization. Nonetheless, this recombination improved network uniformity and integrity due to stress dissipation from the initial fracture, enhancing crystallinity, elongation at break, and tensile strength. This study elucidated the influence of vulcanization crosslinking on the tensile properties of vulcanizates.

Inductive and magnetorheological properties of soft and hard magnetic fillers in elastomers

Magnetorheological elastomers are smart materials, that have great potential for many technical applications like intelligent semi-active dampers or energy harvesting applications. We investigate soft- and hard-magnetic filler types in typical technical elastomers under cyclic deformation regarding their influence on the electromagnetic induction and magnetic switching-ability of the compounds. The effect of vulcanization in an external magnetic field is considered leading to anisotropic samples with aligned filler particles. It is found that the soft magnetic fillers show a higher switching-ability compared to hard magnetic fillers in anisotropic samples, which is related to hysteretic and slow magnetization behaviour of hard magnetic fillers. This also leads to a negative switching effect or softening of the samples if the direction of the magnetic field is opposite to that during vulcanization, suggesting rotational motion of the particles in dependence of the outer field. The stress values and mechanical hysteresis are generally higher for the anisotropic samples, both for soft and hard magnetic fillers. This is found for quasistatic and dynamic excitations at different frequencies and can clearly be related to the alignment of particles. Nevertheless, the energy harvesting ability seems to be widely independent of this since no significant different inductive properties are found for isotropic and anisotropic samples. The possibility of a combined magnetorheological and energy harvesting application is discussed.

The effect of dynamic vulcanization on the morphology and biodegradability of super toughened poly(lactic acid)/unsaturated poly(ether-ester) blends

Preparing a super-tough polylactic acid (PLA) material while maintaining its biodegradability is a significant challenge. This study synthesized a biodegradable unsaturated poly(butylene succinate-co-fumarate)-poly(ethylene glycol) multiblock copolymer (PBSFG) and dynamically vulcanized it with PLA to obtain super-tough blends. The PBSFG self-vulcanized and formed a crosslinked “hard-soft” core-shell rubber phase in the blending process, where the PBSF segment acted as the core and PEG as the shell. As a result, the elongation at break and notched Izod impact strength of PLA increased significantly from 3 % to 66 % and from 3.2 to 58.0 kJ/m2, respectively. Furthermore, adding a small amount of dicumyl peroxide (DCP) promoted dynamic vulcanization and improved the compatibility between PLA and PBSFG. With the addition of 0.03 % DCP, the elongation at break and notched Izod impact strength of PLA/PBSFG were further increased to 218 % and 88.9 kJ/m2, respectively. Meanwhile, the crystallization rate of PLA was enhanced by the addition of PBSFG and DCP. The PLA/PBSFG blends also degraded in a proteinase K Tris-HCl buffered buffer solution. Finally, fully biodegradable and super-tough PLA blends were achieved.

Physical and mechanical properties of vulcanized and filled rubber at high strain rate

The purpose of this study is to investigate -at nanoscale- cis-Polyisoprene(cis-PI), the main component of natural rubber. This system is vulcanized by adding elemental sulfur to cis-PI and vulcanizing at high temperature to obtain vulcanized rubber. The study is extended to cis-PI including different amounts of fullerenes to the vulcanized rubber at high temperature in order to obtain carbon black filled vulcanized rubber. The physical and thermodynamic properties of vulcanized rubber as well as carbon black-filled vulcanized rubber were studied to shed light on the effects of vulcanization and nanofiller on natural rubber. The interaction between fullerenes and cis-PI atoms and the aggregation configuration of cis-PI atoms around fullerenes were analyzed in details by introducing local number density and potential mean force (PMF) through radial distribution function (RDF). Besides, various mechanical quantities were obtained at different temperatures with and without nanofiller.

Fabrication of EPDM/LDPE shape memory composites: the effect of vulcanization and crystals

Fabrication of EPDM/LDPE shape memory composites: the effect of vulcanization and crystals

Effect of dynamic vulcanization on the performance of high content rubber modified asphalt

AbstractHigh content rubber modified asphalt (HCRA) is usually prepared with devulcanized rubber (DR) in asphalt with good workability. However, the high‐temperature properties of HCRA deteriorate simultaneously. In this study, dynamic vulcanization approach was adopted to improve the high‐temperature properties of HCRA without mitigating the workability and low‐temperature performance of modified binder blends. The dynamic vulcanization process and mechanism were investigated based on the gel content, related chemical reactions, morphology, rheological behavior, and tensile properties of HCRA. The occurrence of dynamic vulcanization was confirmed by the increase in gel content. Fourier transform infrared spectroscopy reflected that CC bonds in trans‐olefins participated in dynamic vulcanization, followed by the reaction of those in conjugated olefins. Optical microscopy tests showed that dynamic vulcanization also improved the compatibility between the DR and asphalt. It was found that dynamic vulcanization of HCRA is the gradual stabilization process to form local cross‐linked networks in asphalt. With the addition of sulfur, degradation, aging, and dynamic vulcanization took place simultaneously in HCRA. Dynamic vulcanization increased the high‐temperature properties, fracture toughness, as well as storage stability of HCRA. Furthermore, dynamic vulcanization restricted rubber degradation and improved the aging behavior of HCRA.

The mechanical and thermal properties of natural rubber/zinc methacrylate composites by latex compounding techniques

AbstractZinc methacrylate (ZDMA) is a typical ionic compound that readily reacts with rubber molecules. In this work, a new approach was developed to prepare natural rubber (NR)/ZDMA composites with a lower loading of ZDMA. ZDMA was prepared by the reaction of methacrylic acid (MAA) and ZnO in an aqueous solution. Then the NR/ZDMA masterbatches were obtained by latex compounding techniques; followed by vulcanization either with dicumyl peroxide (DCP) or together with a sulfur‐based vulcanization system (SVS). The results of mechanical property tests showed that the increment of ZDMA will decrease the cure rate index and increase crosslink density. When the content of ZDMA was more than 8.7 phr, not only the 300% and 500% modulus, tensile, and tear strength of NR/ZDMA composites were improved remarkably, but also the aging resistance and thermal stability were improved. When the amount of ZDMA is less than 8.7 phr, SVS shows a certain synergistic vulcanization effect with DCP. When 20 phr ZDMA was added, the tensile and tear strength increased by 86.5% and 60.1%, respectively, when contrasted to NR cured with traditional SVS. The structural characterization results revealed that ZDMA and Poly‐ZDMA have been formed and act as a reactive filler in the NR matrix.

Effect of Vulcanization on the Electro-Mechanical Sensing Characteristics of Multi-Walled Carbon Nanotube/Silicone Rubber Composites.

In order to realize effective monitoring for the working performance of seismic isolation structures, a multi-walled carbon nanotube (MWCNT)/methyl vinyl silicone rubber (VMQ) composite was prepared via mechanical blending using dicumyl peroxide (DCP) and 2,5-dimethyl-2,5-di(tert-butyl peroxy)hexane (DBPMH) as vulcanizing agents. The effects of the different vulcanizing agents on the dispersion of the MWCNT, electrical conductivity, mechanical properties, and resistance-strain response of the composites were investigated. The experimental results showed that the percolation threshold of the composites prepared with the two vulcanizing agents was low, while the DCP-vulcanized composites showed high mechanical properties and a better resistance-strain response sensitivity and stability, especially after 15,000 loading cycles. According to the analysis using scanning electron microscopy and Fourier infrared spectroscopy, it was found that the DCP contributed higher vulcanization activity, a denser cross-linking network, better and uniform dispersion, and a more stable damage-reconstruction mechanism for the MWCNT network during the deformation load. Thus, the DCP-vulcanized composites showed better mechanical performance and electrical response abilities. When employing an analytical model based on the tunnel effect theory, the mechanism of the resistance-strain response was explained, and the potential of this composite for real-time strain monitoring for large deformation structures was confirmed.

Semiconductor-metal transition in vulcanized NiCo2O4 film

The effects of vulcanization on the electrical transport properties and magnetic structure of NiCo2O4 were studied in this work. NiCo2O4 films were epitaxially grown on Al2O3 substrate, and then vulcanized. The NiCo2O4 structures with O replaced by S atoms were calculated based on the density functional theory. As O were replaced by S atoms, the orbital overlap between S and cations increases, the localized electrons around cations are transformed into collective electrons, and the conductive behavior of the film changes from semiconductor to metal. The formation of covalent bonds caused by S substitution leads to the weakening of the interaction between tetrahedral Co and octahedral Ni ions. Meanwhile, the d-orbital energy level of cations shifts. The spin direction of Ni ions and half tetrahedral Co ions is flipped in the vulcanized NiCo2O4 structure, and the electrons at Ni3+eg level enter the conduction band, which makes the carrier type of the vulcanized NiCo2O4 film change from p to n-type. These results indicate that S atoms play an active role in improving the conductivity of NiCo2O4.

Effect of vulcanization on deformation behavior of rubber seals: Thermal–mechanical–chemical coupling model, numerical studies, and experimental validation

Vulcanization molding has a significant impact on dimensional changes of rubber seals. Numerical analysis of this process can improve dimensional accuracy of molded sealing products. In this study, a stress–strain relationship model that considers thermal expansion, cold contraction, and shrinkage caused by a crosslinking reaction under the constraint of a mold boundary was established, a transient analysis method for thermal–mechanical–chemical coupling of the process from rubber seal vulcanization to mold opening was developed, and dimensional changes of the rubber seal in the mold and after cooling were predicted. Results calculated by the model were verified by the production of typical seals. The influences of vulcanization process parameters on changes in molded seal size were numerically analyzed. The numerical results showed that the dimensional shrinkage ratio increased nonlinearly from 3.2 % to 3.8 % when the vulcanization temperature increased from 165 to 185 °C, i.e., an increase of 0.206 % for every 1 % increase in shrinkage caused by the vulcanization reaction. These research results can be utilized in the design of vulcanization molds for high-precision rubber seals.

Ultra-high impact PPR composites at low-temperature through enhanced preferential loading of nanoparticles at polymeric interface induced by properly vulcanized rubber dispersed phase

A variety of low-temperature toughened, rigid-tough balanced polypropylene random copolymer/ethylene propylene rubber/silica (PPR/EPM/SiO2) nanocomposites were prepared by properly crosslinked rubber phase. The impact test results showed that the slightly vulcanized PPR/EPM/SiO2 composites presented lower ductile-to-brittle transition temperature (Tbd) and more excellent low-temperature toughness than unvulcanized or highly vulcanized composites, and there was hardly rigidity loss induced by slight vulcanization. SiO2 distribution, the size of EPM dispersed phase and EPM relaxation were investigated by TEM, SEM, rheology and DMA, respectively. It was found that the remarkable decrease of Tbd for slightly vulcanized PPR/EPM/SiO2 composites was due to the synergistic effect of SiO2 nanoparticles and vulcanization of rubber phase. Furthermore, the origin of excellent low-temperature toughness for vulcanized PPR/EPM/SiO2 composites was ascribed to the enhanced interfacial distribution of SiO2 nanoparticles induced by moderate vulcanization of rubber phase, which increased damping loss of rubber phase, increased interfacial area and decreased the matrix ligament thickness.

Effect of vulcanization and reaction temperature of the carbide supported on activated carbon on glycerol trioleate deoxygenation

Cobalt molybdenum carbide supported on activated carbon was synthesized and the effect of sulfiding on the catalytic activity of the glycerol trioleate deoxygenation process (DOX) was evaluated. Prior to the glycerol trioleate deoxygenation reactions, the catalyst was reduced and sulfided with CS2/H2. The CoMo/CA carbide was characterized by specific area (B.E.T), X-ray diffraction (XRD), elemental analysis (CHON-S), potentiometric titration with n-butylamine and X-ray photoelectron spectroscopy (XPS). The specific area of the CoMo/CA carbide and the support were 246 m2/g and 881 m2/g, respectively. XRD analysis proved the presence of Co6Mo6C2 and metallic cobalt. XPS showed the presence on the surface of signals assignable to Moδ+, Mo4+, Mo6+, Co2+, S2– and SO42–. Sulfided CoMo/CA carbide showed higher activad to glycerol trioleate esoxygenation than unsulfided CoMo/CA carbide. The highest yield was obtained at 310 °C, 900 psi H2 and 2 h of reaction (100% conversion) and a higher selectivity towards heptadecane (55%) and octadecane (45%) favoring decarboxylation (HDCX) and decarbonylation (HDCn) than hydrodeoxygenation (HDO).

Polyamide 6‐based thermoplastic vulcanizate for thermostability: An experimental and theoretical investigation

AbstractIn engineering cases, nonuniform temperature and pressure loads will cause greater thermal stress and deformation of the structure. The creep of materials will also accelerate with the increase of temperature, which greatly reduces the service life of parts. This study improves the vulcanization effect and two‐phase compatibility of polyamide 6‐based thermoplastic vulcanizates (TPV), and the elastic modulus of the material was increased to resist deformation and creep. The compatibility and mechanical properties of the materials were analyzed by dynamic thermodynamic analysis. The temperature and stress of charge air pipe are numerically calculated by fluid‐thermal‐solid coupling. The results show that at 120°C, the strain of TPV is less than 3%, and no plastic deformation occurs. Based on the principle of time–temperature superposition, the long‐term creep behavior at reference temperature is predicted by stepped isothermal method through short‐term temperature rise creep experiment. The creep strain after 105 h at 60°C of TPV grafted by maleic anhydride (TPV‐g‐MAH) is only 2.8%, indicating that it has good durability in the application of charge air pipes.

Effect of Vulcanization and CO2 Plasticization on Cell Morphology of Silicone Rubber in Temperature Rise Foaming Process.

Both vulcanization reaction and CO2 plasticization play key roles in the temperature rise foaming process of silicone rubber. The chosen methyl-vinyl silicone rubber system with a pre-vulcanization degree of 36% had proper crosslinked networks, which not only could ensure enough polymer matrix strength to avoid bubble rupture but also had enough dissolved CO2 content in silicone rubber for induced bubble nucleation. The CO2 diffusion and further vulcanization reaction occur simultaneously in the CO2 plasticized polymer during bubble nucleation and growth. The dissolved CO2 in the pre-vulcanized silicone rubber caused a temperature delay to start while accelerating further vulcanization reactions, but the lower viscoelasticity caused by either CO2 plasticization or fewer crosslinking networks was still the dominating factor for larger cell formation. There was a sudden increase in elastic modulus and complex viscosity for pre-vulcanized silicone rubbers at higher temperature because of the occurrence of further vulcanization, but CO2 plasticization reduced the scope of change of rheological properties, and the loss factor was close to 1 around 170 °C, which is corresponding to the optimum foaming temperature. The foamed silicone rubber had a higher cell density and smaller cell size at a higher temperature rising rate, which is due to higher CO2 supersaturation and faster vulcanization reaction. These results provide some insight into the coupling mode and effect of CO2 plasticization and vulcanization for regulating cell structure in foaming silicone rubber process.

Effect of vulcanization on the tribological behavior and sealing performance of EPDM seals: Experimentation and simulation

Vulcanization has an important influence on the performance of rubber seals. Modeling is an effective means of determining the optimal vulcanization process parameters. In the present study, the tribological and mechanical properties of ethylene-propylene-diene monomer (EPDM) samples with various degrees of vulcanization were analyzed, and a mathematical relationship between the degree of vulcanization and the properties was established. On the basis of the transient thermo-chemical coupling model of the vulcanization process, a finite element model was developed to solve the problems associated with the process parameters and product properties of rubber seals. The model can be used to evaluate the variation in sealing capacity and service life of seals produced under various vulcanization conditions to determine the optimal vulcanization parameters.