Rubber Formulations Research Articles

Role of geopolymer as a cure activator in sulfur vulcanization of epoxidized natural rubber

ABSTRACTGeopolymer (GP) was synthesized and used as activators in sulfur vulcanization of epoxidized natural rubber (ENR). Influences of GP on cure characteristics, crosslink density, mechanical, thermal, and morphological properties were investigated and compared to the conventional rubber formulation with ZnO activator. The ZnO is a hazardous chemical for the environment and has proclaimed that its application in rubber technology should be reduced and controlled. It was found that the GP‐activated ENR compounds showed significantly higher vulcanization rate than cases with the conventional ZnO compound. This was indicated by the GP activated compounds having shorter scorch time, cure times, and lower activation energy but higher cure rate index (CRI). Also, the GP activated ENR compounded with stearic acid exhibited the highest conversion. This matches well the highest torque difference and crosslink density, observed by temperature scanning stress relaxation (TSSR) and swelling measurements. Furthermore, the GP‐activated vulcanizate had better thermal stability than the ZnO‐activated ENR material. In addition, the GP‐activated ENR vulcanizate with stearic acid exhibited high 100% moduli, tensile strength, and hardness. This proves that GP has a high potential for use as activators in sulfur vulcanization of rubber compounds, as an alternative to the conventional ZnO. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48624.

Numerical and experimental studies on wrinkling control methods of sheet metal part with high curvature and large flange in rubber forming

Wrinkling is one of the main failure modes in sheet metal forming process and may lead to assembly problems of the parts. Control of wrinkling is difficult due to the complex deformation behavior of the sheet metal. A finite element model for side blankholder method to control wrinkling was established and used for the simulation. Trials and simulations were conducted to analyze the parameters of wrinkling characteristics. Results show that with the increase in the angle of the side blankholder, the resistance force of the side blankholder decreases. The blank length on the side blankholder should be small enough. The fillet radius of the side blankholder should be large enough to reduce the deformation. The bottom gap between the die and the side blankholder cannot be too large because the support of the blank will decrease in the forming process. In order to verify the simulation results, three blank lengths (20, 15, and 5 mm) over the side blankholder were used in the experiment. The results of the comparison tests testify the reliability of the simulation. The optimal parameter of the blank length is 5 mm. A new clamp method was designed for wrinkling control to overcome the shortcomings of the side blankholder method. The precision of the part met the requirement using soft rubber and two layers of rubber plates.

Monte Carlo Study of Rubber Elasticity on the Basis of Finsler Geometry Modeling

Configurations of the polymer state in rubbers, such as so-called isotropic (random) and anisotropic (almost aligned) states, are symmetric/asymmetric under space rotations. In this paper, we present numerical data obtained by Monte Carlo simulations of a model for rubber formulations to compare these predictions with the reported experimental stress–strain curves. The model is defined by extending the two-dimensional surface model of Helfrich–Polyakov based on the Finsler geometry description. In the Finsler geometry model, the directional degree of freedom σ → of the polymers and the polymer position r are assumed to be the dynamical variables, and these two variables play an important role in the modeling of rubber elasticity. We find that the simulated stresses τ sim are in good agreement with the reported experimental stresses τ exp for large strains of up to 1200 % . It should be emphasized that the stress–strain curves are directly calculated from the Finsler geometry model Hamiltonian and its partition function, and this technique is in sharp contrast to the standard technique in which affine deformation is assumed. It is also shown that the obtained results are qualitatively consistent with the experimental data as influenced by strain-induced crystallization and the presence of fillers, though the real strain-induced crystallization is a time-dependent phenomenon in general.

A thermo-mechanical finite element material model for the rubber forming and vulcanization process: From unvulcanized to vulcanized rubber

In this contribution, the transition in the thermo-mechanical properties of unvulcanized rubber during the vulcanization (curing) process is modeled by a material model for unvulcanized and vulcanized rubber (two-phase material) in the context of finite strain thermo-mechanics within the finite element method (FEM). For the vulcanization rate, a constitutive approach with few parameters is proposed representing the monotonic increase of the degree of vulcanization as a function of current temperature and the curing history. The material model taking into account the two phases of rubber uses different constitutive approaches for the isochoric part and the volumetric part for which a multiplicative split of the deformation gradient is considered. The isochoric part of the model consists of a hyperelastic spring and a dashpot device in series forming a Maxwell element with properties depending on the degree of vulcanization and temperature. Inelastic isochoric deformations during the forming and vulcanization process of rubber parts can be captured. The volumetric part consists of a hyperelastic spring and takes into account volume changes due to mechanical loads and temperature variations (thermal expansion). The proposed material model is formulated based on the displacement field, the temperature field, the degree of vulcanization and its kinetics. It is implemented into the thermo-mechanically coupled framework of the FEM in 3D for finite strains.

Off-line TLC-IR (UATR) characterization of additives in EPDM rubber

Abstract Sulfur donor accelerators and vulcanization agents, such as peroxides, due to their chemical characteristics and good thermal stability properties in rubber formulations, are essential to provide solutions in different sectors, such as aerospace and automotive, since they reduce the polymer degradation process (reversal), which can influence the performance of the elastomeric material. In this way, the use of methodologies for the components knowledge of a formulation is imperative for the structure proper establishment/property relationship of the elastomeric artifacts. The development of methodology that can separate and characterize the rubber formulation components is a constant challenge, still allows gaps, and is usually done by conventional but not coupled instrumental techniques. In this scenario, this paper aimed to contribute to the use of the off-line coupling of thin-layer or thin-layer chromatography (TLC)/infrared spectroscopy (FT-IR), by universal attenuated total reflection (UATR) for N-cyclohexyl-2-benzothiazolesulfenamide (CBS), tetramethyl thiuram disulphide (TMTD) and dicumyl peroxide (DCP), in formulations of ethylene and propylene diene monomer (EPDM) rubber containing the plasticizer naphthenic oil. This plasticizer was characterized in formulations that presented higher content of this compound, but the eluting systems were not effective in separating DCP. However, better separation of CBS and TMTD was observed.

Quantifying the Vial-Capping Process: Reexamination Using Micro-Computed Tomography.

A vial-capping process for lyophilization stopper configurations was previously quantified using residual seal force (RSF). A correlation between RSF and container closure integrity (CCI) was established, and component positional offsets were identified to be the primary source of variability in RSF measurements.To gain insight into the effects of stopper geometry on CCI, serum stoppers with the same rubber formulation were investigated in this study. Unlike lyophilization stoppers that passed CCI (per helium leak testing) even with RSF of 0 N owing to their excellent valve seal, serum stoppers consistently failed CCI when RSF was <15.8 N. When the plug was removed, both types of stoppers exhibited a comparable critical lower RSF limit (19-20 N), below which CCI could not be maintained. When CCI was retested at later time points (up to 6 mo), some previously failed vials passed CCI, suggesting that CCI improvement might be related to rubber relaxation (viscous flow), which can fill minor imperfections on the vial finish.To confirm component positional offsets are the primary sources of RSF variability, a novel quantification tool-micro-computed tomography (micro-CT)-was used in this study. Micro-CT provided images for quantification of positional offsets of the cap and stopper that directly correlated with RSF fluctuations. Serum stoppers and lyophilization stoppers are comparable in RSF variations, although lyophilization stoppers are more robust in CCI. The use of micro-CT provides a nondestructive and innovative tool in quantitatively analyzing component features of capped vials that would otherwise be difficult to investigate.

Influence of nanofibers prepared from rice husk on the properties of natural rubber

ABSTRACT Different concentrations of rice husk fibres have been mixed with natural rubber to study the effect on the properties of rubber mixtures and vulcanisates. Cellulose nanofibers were added in different concentrations up to 100 phr. The aim was to improve the mechanical properties of the composite, swelling resistance, and rheological properties. The research studied microstructure of prepared composites and properties of rubber mixes and vulcanisates, using transmission electron microscopy (TEM) and X-ray diffraction. Rice husk fibres derived from treating the husk with sodium hydroxide followed by careful drying and grinding in ball mill were used as filler in natural rubber formulations. These treated fibres improved the tensile strength up to an optimum concentration (20 phr) and then started to decrease in effect. A marked improvement in the modulus of elasticity and hardness of rubber mixtures also occurs.

Multipurpose tube from waste to instructional media for physics education

Waste is a substance that is not liked by the community. However, if managed and processed professionally can be useful. The most heavily processed waste is solid waste. This research is a recycle process of industrial solid waste and household in the form of wood, rubber, and glass. The recycle process has been carried out on garbage and produces physics learning media, named “Multipurpose Tubes”. The application of scientific method in making the set of instructional media, proved able to hone the skills of science process of high school students through physics education.

Enhancement of Hot Mix Asphalt (HMA) Properties Using Waste Polymers

This research presents a comparative analysis of properties and performance of hot mix asphalt (HMA) modified by various polymer-based waste materials which included low-density polyethylene (LDPE) in the form of polyethylene bags (shopping bags), high-density polyethylene (HDPE) in the form of waste plastic beverage bottles and crumb rubber (CR) from waste tires. Polymer was added to coat the aggregate (dry method) and as a modifier in bitumen (wet process). Marshall method was used for the analysis of control and modified asphalt mixes. Dry method yielded better asphalt mix properties. Optimum polymer content was determined as percentage of optimum bitumen content. Polymer-modified bitumen exhibited improved stiffness and reduced susceptibility to high-temperature effects. Polymer-modified asphalt mix is found have increased stability, rutting resistance and load bearing capacity in comparison with unmodified asphalt mix. In overall comparison, HDPE-modified mix was found to be the most effective. Road construction with CR-modified HMA was found to be the most cost-effective with Rs. 0.166 million saving per lane km, compared to conventional, LDPE- and HDPE-modified HMA.

Identification of natural rubber samples for high-voltage insulation applications

Latex presents high variability due to inherent differences among varieties from different countries, producers or crop seasonality. Natural rubber formulations from natural latex, to be used in insulating materials intended for high-voltage applications, require a wide variety of compounding and multitude of industrial processes. These aspects make it very difficult ensuring the same dielectric properties of the final product. At manufacturing level, it is very important to apply strict control processes to ensure that the final product fulfills all quality specifications. In this paper, a promising approach was applied to automatically identify natural rubber samples with suitable dielectric behavior from those with unsuitable dielectric behavior. This approach is based on the study of FTIR spectral data by applying suitable multivariable methods, such as principal component analysis, canonical variate analysis and k-nearest neighbors. The accurate and fast results reported in this work prove the suitability and potential of the proposed approach.

Synthesis graphene based sensor for strain data and its characterization

Graphene material with fine structure is used to fabricate for the different types of sensors. Graphene are mostly 2D structure bounded by sp2 carbon atoms in a honeycomb lattice parameter prented. Strain sensors are immense interest over the past years, which is used to deduct the change in the human bodies. It applicable in various field such as chemical, mechanical, electrical and electronic sensor. Graphene based strain sensors fabricated in a form of stretchable rubber by the way of stamping technique. Under this process mechanical properties of the synthesized graphene materials was systamatically discussed and also investigated the X-ray diffraction, surface manufacturing studies, raman spectroscopy and I-V characteristics studies. Finally, strain sensor for human body was measured by connecting with the with glove and the strain was measured corresponding with resistance values. After stretching glove, the strain value become the original position. The strain change based on the resistivity during the exercise the period.

An Intelligent Method to Design Die Profile for Rubber Forming of Complex Curved Flange Part

Rubber forming is an important forming process for the manufacture of aircraft sheet metal parts. The springback is one of the main defects in rubber forming. Classical springback compensation by displacement adjustment method using finite simulation is not satisfactory. In this research, the algorithms of compensating the arc and flange surface of complex curved flange with correction formula are proposed by experiment. The correction formula was developed based on the CATIA V5 R19 using Component Application Architecture. Compensate profile is presented including surface pick up, line pick up, division, compensation, extending, and trimming. The die profile of part with complex curved flanges in aircraft could be designed rapidly. It was found that the forming pressure has a little effect on the springback. This is within the tolerance limits of the part. The results reveal the method can achieve the industrial part precisely. The method is demonstrated on an aircraft wing rib part.

A Review of Natural Rubber Nanocomposites Based on Carbon Nanotubes

The original form of Natural Rubber (NR) has limited usage despite its excellent elasticity and reversible deformability. Further improvement of its undesired properties, i.e. low hardness, durability and tear resistance will allow for application of NR on a broader scale. Traditional reinforcing materials such as carbon black have indicated improvement in NR-based composites. However, the increasing range of newly emerging applications comprising polymeric composites motivates researchers to focus on developing NR-based composites with better physical properties. Many nanoscale fillers have been widely researched to attain extraordinary properties in NR based products. Among the different nanostructures, carbon nanotubes (CNTs) have been widely examined for NR modification.Addition of a tiny amount of well-dispersed CNTs to NR allows for significant improvements in physical properties of NR. Preparing nanocomposites comprising CNTs and other types of fillers also demonstrates enhancement of NR properties. Besides improvements in mechanical properties, the presence of CNTs considerably improves other properties of NR, such as thermal stability as well as electrical and thermal conductivity. However, owing to interactions between individual CNTs as well as CNTs and other components (NR or other fillers), property improvement varies depending on the type of fillers and their ratio in NR. This review summarises the reported processing conditions and property improvements in NR reinforced with CNTs as a solefiller or with other additive fillers. This paper will help to better understand the status of research on developing an NR/CNT nanocomposite and discover challenges and obstacles that need to be resolved.

Ambient curable latex films and adhesives based on natural rubber bearing Acetoacetoxy functionality

The study described in this paper first demonstrates that a newly modified form of natural rubber, namely graft copolymers of natural rubber with poly (acetoacetoxyethyl methacrylate), NR‐g‐PAAEM, is able to undergo a cross‐linking reaction at room temperature by reaction with a water dispersible polyisocyanate based on hexamethylene diisocyanate (poly‐HDI). Attenuated total reflectance Fourier transform infrared (ATR‐FTIR) analysis indicated that amide groups were formed by the reaction of the acetoacetyl groups (AcAc) present in the grafted poly (acetoacetoxyethyl methacrylate) (PAAEM) chains with the poly‐HDI. This observation was accompanied by a noticeable increase in the tensile strength of the NR‐g‐PAAEM latex films when adding poly‐HDI to the latex prior to film formation. DMTA analyses also revealed a shift in the tan δ peaks, corresponding to the transitions of both NR‐g‐PAAEM and free PAAEM phases, to higher temperatures. These results provide firm evidence of cross‐linking between NR‐g‐PAAEM chains by reaction with poly‐HDI during film formation under ambient conditions. Adhesives for bonding wood to wood based on the NR‐g‐PAAEM latex were then prepared, using poly‐HDI as the cross‐linker. The lap shear strength of the resulting adhesives exhibited a maximum value of 2657 KPa when a poly‐HDI:AAEM molar ratio of 3:1 was employed. It was also observed that the adhesive attained about approximately 89% of the highest lap shear strength after it was allowed to set at 30°C for 24 hours. Hence, the use of poly‐HDI in cross‐linking NR particles bearing grafted PAAEM offers great potential for developing latex adhesives and coatings capable of curing under ambient conditions.

A review on devulcanization of waste tire rubber

Rubber has become an indispensable material for the technological development of civilization, including simple balloon and complex rocket propellant. Rubber Industry worldwide is using on an average 50% of raw materials. These materials were mostly petroleum-based, except natural rubber (NR), steel cord and bead wire. Using of these petroleum-based raw materials not only depletes natural resources, but also produces more extreme environmental hazards. The waste tire rubber problem is of great magnitude and has far reaching environmental and economic implications. There are some ways for recycling of rubber, such as reclaiming technology, surface treatment, grinding and pulverization technology, devulcanization technology. Methods of devulcanizing rubber (or elastomers) have been researched almost since the time of the discovery of the rubber/sulfur vulcanization process. By devulcanization process the cross-links in the structure of rubber are broken and devulcanized rubber can be revulcanized into a raw material for rubber industry, which is a highly valued form of waste rubber. This study provides a review of the recent advances in understanding of methods of recycling rubber and claims that the capacity of thermomechanical and mechanochemical devulcanization methods of recycling waste tire rubber can be improved in future studies.

Shin-Etsu to spend up to $1 billion on silicones

Shin-Etsu Chemical will invest about $990 million to expand its silicones business worldwide over the next two and half years. The Japanese firm plans to spend about $450 million to expand its silicone monomer plants in Japan and Thailand, $450 million on facilities for downstream products in six countries, and $90 million on shipping facilities and other business infrastructure. Between 2013 and 2017, Shin-Etsu’s silicone sales increased by 32%, while margins swelled by 63%. The largest silicone producer in Japan, Shin-Etsu sells the materials worldwide in powder, liquid, and rubber form. They are used in applications including cosmetics, contact lenses, and solar panels. Shin-Etsu’s bold bet on its silicone business comes shortly after it made a comparably large commitment to its polyvinyl chloride business. In July, Shin-Etsu announced that its U.S. subsidiary Shintech will spend $1.5 billion in Louisiana to expand a polyvinyl chloride plant and build facilities for the

COMPARISON BETWEEN RICE HUSK SILICA-FILLED EPOXIDIZED NR CROSS-LINKED WITH FUMARIC ACID AND VULCANIZED WITH SULFUR

ABSTRACT A wide variety of fillers are used in the rubber industry to modify the properties of rubber compounds and reduce the cost of products in different applications. Silica produced from rice husk could be an alternative filler to commercial precipitated silica widely used in sulfur-vulcanized rubber formulations. High purity amorphous silica (&amp;gt;99% SiO2) was produced after pretreatment of rice husk with dilute sulfuric acid before combustion at 600 °C. Epoxidized NR (ENR) with 50 mol% epoxide groups (ENR50) containing various silica loadings was cured with fumaric acid via reactions of the epoxide group with –COOH, whereas sulfur vulcanization used the carbon–carbon double bonds, as confirmed by Fourier transform infrared spectroscopy (FTIR) analysis. Increasing silica loading in both of types of samples led to an increase in rheometer torque and a decrease in percentage of solvent swelling due to the stiffening effect of silica, with no change in glass-transition temperature, which presumably was due to no chemical reaction between silica and ENR. The tensile strength of fumaric acid–cured ENR50 slightly increased with increasing silica loading and remained unchanged upon aging. The sulfur-vulcanized ENR50 containing 30 phr silica exhibited higher tensile strength, but further increase of silica weakened these properties. After aging, the tensile strength reduced by 5–7 MPa. Fumaric acid–cured rubbers have shown superior aging properties.

INTERPRETATION OF THE TANδ PEAK HEIGHT FOR PARTICLE-FILLED RUBBER AND POLYMER NANOCOMPOSITES WITH RELEVANCE TO TIRE TREAD PERFORMANCE BALANCE

ABSTRACT The aim of this research is to clarify the meaning of the peak height for the viscoelastic loss tangent (tanδ) in the glass transition region of particle-filled rubber, polymer nanocomposites, and polymer systems in general. Filler, oil, and curative loadings were systematically varied in a model styrene-butadiene rubber formulation with carbon black as the reinforcing filler. The dynamic mechanical responses of these compounds enabled a detailed study of the glass-to-rubber softening transition, which is known to play an important role with respect to the balance of traction, handling, and rolling resistance characteristics of tire treads. From the temperature-dependent viscoelastic results that were acquired at fixed frequency and small dynamic strain, it was demonstrated that a higher peak value for tanδ was correlated with a lower dynamic modulus in the rubbery state. Adjusting filler volume fraction was found to be an effective way of changing the rubbery modulus and hence the tanδ peak height. It was furthermore verified that such a correlation is a universal material-independent viscoelastic effect by mathematically producing a similar trend by varying the rubbery modulus parameter in the Havriliak–Negami viscoelastic model. This investigation also showed why glass transition temperature should be determined from the position of the loss modulus peak and not the tanδ peak. Cure behavior, tensile stress–strain properties, and extent of filler networking (Payne effect) for these rubber compounds will additionally be discussed.

Investigation of dimensional accuracy in forming of metallic bipolar plates with serpentine flow field

In this study, the dimensional accuracy of metallic bipolar plates with stainless steel 316 was investigated in diagonal, longitudinal, and transverse direction (directional dimensional accuracy). The results showed that directional dimensional accuracy (uniformity of channel depth) would increase by raising the applied force. In addition, increasing the rubber hardness and rubber thickness leads to higher directional dimensional accuracy. After that, the dimensional accuracy in constant direction (total dimensional accuracy) was investigated. According to the result, central channels have lower channel’s depth than lateral channels. Difference between central and lateral channel’s depth was decreased when the applied force was increased. Also, total dimensional accuracy increased by increasing hardness and thickness of rubber. Most accurate bipolar plate is fabricated by 450 kN applied force and rubbers with hardness of Shore A 90 and 30 mm thickness. However, dimensional accuracy in conventional rubber forming process was not satisfying. Thus, a new method was used in order to improve the dimensional accuracy of fabricated bipolar plates named semi-stamp rubber forming. The results indicated that using semi-stamp rubber forming instead of conventional rubber forming would lead to 8.35, 3.72, and 3.3% improvement in directional dimensional accuracy and also 1.075% improvement in total dimensional accuracy.

VULCANIZATION SYSTEMS FOR RUBBER COMPOUNDS BASED ON IIR AND HALOGENATED IIR: AN OVERVIEW

ABSTRACT The properties of IIR and halogenated IIRs, such as excellent steam and gas impermeability, heat aging stability, and oxygen and ozone resistance and increased chemical resistance, meet the demands of various industrial applications. However, due to the low level of unsaturation of IIR, the vulcanization rate is rather low and the degree of cross-linking is usually insufficient, causing IIR to be minimally co-vulcanized with unsaturated general-purpose rubbers. The low reactivity of IIR requires the consideration of a special composition of curing systems to provide the best possible rate and state of vulcanization. The type of curing system selected must also be a function of the composition of rubber formulations in which the IIR is used, and with respect to the final product's performance requirements. Therefore, the curing systems for IIR differ and can include standard sulfur systems, phenol-formaldehyde resins, or quinones. The incorporation of halogen (chlorine or bromine) atoms into the structure of IIR significantly increases the chemical reactivity, which can be subsequently reflected in a higher curing rate and the possibility to use some additional vulcanization systems such as metal oxides, diamines, or peroxide with co-agent. This study reviews the types and selection of applicable curing systems for IIR and its halogenated derivates.