Carboxylated Nitrile Butadiene Rubber Research Articles

Liquid carboxylated nitrile butadiene rubber via metathetic degradation with acrylic acid as chain transfer agent

Liquid carboxylated nitrile butadiene rubber (LXNBR) shows promising application in various fields. Facing the challenges in its preparation via radical emulsion copolymerization, such as gelation, molecular weight and carboxyl group content, novel approach has been developed for the controlled preparation of LXNBR via the metathetic degradation of nitrile butadiene rubber (NBR) with acrylic acid (AA) as chain transfer agent (CTA). Based on the molecular weight and carboxyl group content of the resultant products, the reaction pathway was proposed. Such understanding is expected to prepare LXNBR with designed Mn and carboxyl group content for various applications, by facile adjusting the reaction condition, mainly the feeding mode of AA, NBR concentration and reaction time.

Rebound characteristics of flexible and stiff jute rubber/epoxy hybrid composite under low-velocity impact

This present work aims to assess the low-velocity impact response of novel configuration based on jute/rubber/epoxy flexible and stiff composites having varying layup sequences using an experimental study. The Charpy and drop weight impact tests are done according to the standards. Drop weight low-velocity impact test at an energy level of 15J was performed using a conical shape impactor. Carboxylated Nitrile Butadiene Rubber (XNBR) containing carbon fillers ( N330 and N550) consisting 35 phr concentration each is used in the stacking sequence of the composite due to its high toughness and energy dissipation property. During drop weight tests conducted at a 15J energy level, the flexible RJRJR composite exhibited a peak force of 486 N, whereas the stiffer RJEJR composite demonstrated a peak force of 1075 N. The flexible composite shows no damage for the energy level tested. However, the stiff composite made using epoxy in between jute layers fails due to the matrix cracking in the composite. The peak force and specific energy absorption is dependent on stacking configuration and increases with the addition of rubber interface in the stiff composite. The energy absorption of stiff composite is higher as compared to flexible composite as indicated by the peak force.

Revealing the unique characteristics and strength of polycarbodiimide as an accelerator‐free crosslinker for low‐temperature processing of carboxylated nitrile butadiene rubber gloves for hand protection

Revealing the unique characteristics and strength of polycarbodiimide as an accelerator‐free crosslinker for low‐temperature processing of carboxylated nitrile butadiene rubber gloves for hand protection

PEDOT:PSS/XNBR films for low-temperature stretchable electromagnetic interference shielding

Electromagnetic interference shielding materials being sufficiently stretchable at low temperatures have a wider range of applications. Herein, stretchable electromagnetic shielding films for low temperatures applications with segregated conductive networks were produced by a simple method of evaporating carboxylated nitrile butadiene rubber (XNBR) latex containing lithium bis(pentafluoroethylsulfonyl)imide (Li–PFSI) doped poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS). It is proved that the mechanical and electrical properties can be improved by changing the crystallization of PEDOT by doping. For the composite film with 4 wt% PEDOT:PSS and 1.4 mm thickness, electromagnetic interference shielding efficiency can maintain at about 60 dB at 100 % strain and 48 dB at 150 % strain, being the highest among stretchable EMI shields reported. At −10 °C and 100 % strain, shielding efficiency of the composite film with 8 wt% PEDOT:PSS is about 32 dB, indicating that the stretchable film is promising in applications in wearable devices, flexible devices, etc. for EMI shielding at low temperatures.

Polyurethane dispersion/carboxylated nitrile butadiene rubber blends produced by a greener dual crosslinking approach

A latex blend comprising polyurethane dispersion (PUD) and carboxylated nitrile butadiene rubber (XNBR) in an 80:20 ratio was prepared in the presence of epoxide and organo-modified siloxane crosslinkers. The aim of the study was to enhance the tensile, thermal, and chemical properties of the PUD/XNBR latex blend without the incorporation of sulphur and accelerator. Studies revealed that the combined action of epoxide and organo-modified siloxane crosslinker demonstrated adequate intermolecular hydrogen bonding, thereby resulting in superior tensile strength. Differential scanning calorimetry (DSC) analysis showed alterations in chain orientation and melting enthalpy due to the introduction of two crosslinkers that impart ordered hydrogen bonding to a certain degree. The compactness of the structure of the cure molecule may be closely related to the heating enthalpy, as in the following sequence, PUD80/XNBR20/E1 will have a loosely packed structure, followed by PUD80/XNBR20/E0.5S0.5 and PUD80/XNBR20/S1. Chemical swelling studies revealed the impact of crosslinker combinations on hydrogen bonding (both ordered and disordered), affirming the consequential enhancement in chemical resistance. This study confirms that the attained intermolecular hydrogen bonding results in desirable mechanical and chemical resistance performance, making the latex blend suitable for glove applications.

A Facile Scalable Strategy for Constructing Novel Robust Self‐Healing Glove Utilizing Nanoreinforced Thermoreversible Carboxylated Nitrile Butadiene Rubber

AbstractRecent decades have seen an increase in using self‐healing technology in fabricating multifunctional rubber materials, which incorporate intrinsic mechanisms. However, achieving commendable self‐healing efficiency while maintaining strength in thin rubber films remains challenging. Herewith, the preparation of self‐healing carboxylated nitrile butadiene rubber thin films is presented with 0.40 ± 0.05 mm thickness, reinforced with sustainable TEMPO‐oxidized cellulose nanofibers. The thin films are fabricated using wet mixing and casting methods and translated to prototype fabrication via dipping. The study involves the effect of varying zinc stearate and filler concentrations on healing efficiency via ionic mechanisms alongside other characterization techniques, such as chemical composition, surface morphology, cross‐link density, and thermal stability. The fabricated thin films exhibited a tensile strength of 5.38 MPa and an elongation‐at‐break of 518%. After undergoing a temperature‐induced healing process at 100 °C for 1 h, the healing efficiency for both properties reached 72% and 90%, respectively. Moreover, these films demonstrates the ability to heal repeatedly at the same fracture site over multiple cycles, maintaining a healing efficiency of over 45% after the third cycle. A glove prototype is fabricated and tested using water and air leakage tests to prove the self‐healing technology's successful transfer.

A low-temperature stretchable XNBR film containing Li-TFSI doped PEDOT:PSS for electromagnetic interference shielding

Stretchable electromagnetic shields have garnered significant attention in the burgeoning field of flexible devices, while traditional strategies developed to maintain adequate electromagnetic shielding performance under large strains are more challenging at low temperatures. Herein, elastic electromagnetic shielding films with segregated conductive network were produced by an extremely simple method of evaporating carboxylated nitrile butadiene rubber latex containing lithium bis(trifloromethanesulfonyl)imide doped poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate). The films of 0.2 mm in thickness are highly stretchable at −20 °C and exhibit an electromagnetic interference shielding efficiency of more than 30 dB at 100 % strain and −10 °C. These properties underscore the potential of the films as effective stretchable EMI shields in low-temperature conditions. Experiments demonstrating the films' ability to block Bluetooth signals from ESP32 chip microcontrollers and electromagnetic waves from Tesla coils further confirm their usefulness, highlighting the practicality of protecting flexible devices in cold environments.

Processing-structure-property relationships in practical thin solid-electrolyte separators for all-solid-state batteries

Scalable processing of thin and robust solid-electrolyte (SE) separators is key for the commercialization of high-energy all-solid-state batteries (ASSBs). Herein, we report the preparation of Li6PS5Cl-based thin SE separators incorporating suitable binders for potential use in ASSBs by two scalable wet processing techniques: tape-casting with nitrile-butadiene rubber (NBR) and calendering with carboxylated nitrile butadiene rubber (XNBR). By means of tensile testing and electrochemical impedance spectroscopy, the influence of processing on the mechanical as well as the electrochemical properties of the resulting thin SE separators is investigated. A trade-off between the mechanical and electrochemical properties is observed, which is due to the inextricably linked microstructures (particle size, binder content and distribution, and porosity) induced by the two different processes. Thin SE separators prepared using the tape-casting method with the more well-distributed binder network demonstrate superior tensile mechanical properties compared to the ones prepared by the calendering method. The results provide insights into the processing-structure-property relationships of the thin SE separators, which will contribute to advancing the application of practical thin solid electrolytes in ASSBs.

Dual cross‐linking of XNBR latex with epoxy‐functional calcium silicate particles for the production of accelerator‐free medical gloves

AbstractIn this work, an innovative dual cross‐linking strategy for carboxylated nitrile butadiene rubber (XNBR) latex using epoxy‐modified calcium silicate particles is presented. In their role as dual cross‐linker, the particles are able to form covalent bonds (nucleophilic ring opening of epoxy moieties) as well as ionic cross‐links (calcium ions of the inorganic core) across the carboxylic acid groups of the rubber. To characterize the curing efficiency, thin elastomer films are prepared by using a conventional coagulant dipping process and their cross‐link densities, curing kinetics, and tensile properties are investigated as a function of the concentration of the cross‐linker and curing time. The results show that latex films containing 5 phr of epoxy‐functional particles give the highest tensile strength, which is further improved by pre‐vulcanizing the liquid latex compound at 60°C for 30 min. The latex formulations are stable over 3 days and the pre‐cured films exhibit a high resistance against gamma sterilization and subsequent accelerated aging. Moreover, sterile films do not cause any skin irritation or skin sensitization reactions, showing the high potential of epoxy‐functional particles in the production of accelerator‐free hypoallergenic gloves.

Morphology evaluation and mechanical properties of oil-resistant thermoplastic vulcanizates comprising carboxylated nitrile butadiene rubber and thermoplastic polyurethane and their comparison with commercial grades

The morphology, the mechanical properties, and the oil-resistance of thermoplastic vulcanizates (TPVs) of carboxylated nitrile butadiene rubber (XNBR) and thermoplastic polyurethane (TPU) were studied & compared with the commercial ethylene-propylene-diene monomer (EPDM)/polypropylene (PP) TPVs from two suppliers. The rubber phase in these new generations of TPVs was cured with an addition-type curative, and no oil & compatibilizer were required to make these TPVs processable. Three XNBR/TPU TPVs were made with different rubber/plastic ratios (15/85, 30/70, and 45/55). The AFM analysis showed that the morphology shifted from a continuous plastic phase to a co-continuous phase with increased rubber content. The rubber domains in these TPVs were not as discrete as reported in the literature for the EPDM/PP TPVs. Still, because of using an addition-type curative, unlike peroxide and resole phenolic resin curatives for the latter, the former TPVs had a significantly better balance of rubber and plastic properties. The oil resistance of these TPVs was 3.5–5 times better than the commercial EPDM/PP TPVs. These promising results show advancement in the TPV world and make these TPVs appealing for hydraulic oil applications.

Preparation and Characterization of Activated Palm Kernel Shell/Carboxylated Nitrile Butadiene Rubber (APKS/XNBR) Vulcanizate

Malaysia is one of the most important palm oil producers and exporters in the whole wide world. There has been a rapid development of new palm oil plantations and palm oil mills in this country. The palm oil industry plays a vital role in the economic growth of Malaysia. However, as the palm oil industry grows bigger and wider, a huge amount of palm oil waste is produced which is an alarming issue considering it can cause pollution and have a negative effect on the environment. Raw Palm Kernel Shell (PKS) derived from palm oil waste can be converted into Activated Palm Kernel Shell (APKS) which has the potential to be a value-added biofiller in rubber vulcanizates. Thus, in this study, APKS is prepared through a carbonization process at a temperature of 900 °C and an activation process via steam treatment and used as filler in Carboxylated Nitrile Butadiene Rubber (XNBR). The aim of this study is to evaluate the influence of different loading ratios of APKS on theswelling index measurement, bound rubber content (BRC), abrasion resistance, compression set, and hardness of XNBR vulcanizates. APKS is incorporated in XNBR at different loading ratios, ranging from 0 to 50 phr and these APKS-filled XNBR vulcanizates are prepared with a two-roll mill. The overall physico-mechanical properties of APKS-filled XNBR vulcanizates showed increment in terms of BRC, compression set, and hardness as the loading ratio of APKS increased. XNBR vulcanizates with a higher loading ratio of APKS also showed a decrease in swelling index measurement and volume loss which would indicate high abrasion resistance. These results could be attributed to the porosity of APKS as shown in the morphological analysis which provided a high surface area of contact for crosslinking and mechanical interlocking. This proves APKS could potentially be a semi-reinforcing filler for rubber vulcanizates, especially for XNBR vulcanizates as XNBR vulcanizates were able to achieve high abrasion resistance and high hardness with the incorporation of APKS. With this, the conversion of PKS into APKS could help to reduce palm oil waste and provide an environmentally friendly, sustainable biofiller option to rubber researchers and manufacturers who are looking for an alternative to petroleum-based fillers. This would be very beneficial for both the palm oil industry and the rubber industry.

Preliminary Investigation on the Mechanical Properties of Carboxylated Nitrile Butadiene Rubber (XNBR) Blended with Different Loadings of Butyl Reclaimed Rubber (BRR)

Reclaimed rubber (RR) from butyl tubes was evaluated as a partial and full replacement of a virgin rubber which is carboxylated nitrile butadiene (XNBR). This study involves the blending of carboxylated nitrile butadiene rubber with butyl reclaimed rubber (XNBR/BRR) in various loadings andcured with sulfur by using a two-roll mill. The objective is to investigate the effect of RR loading on crosslink density and mechanical properties of XNBR/BRR blends. The mechanical properties such as hardness, rebound resilience, tear strength, tensile strength, elongation at break, and modulus were evaluated. In this study, the amount of reclaimed rubber varied from 0 phr to 161 phr. The results showed that the rebound resilience, tear strength, and tensile strength had a reduction of 43%, 27%, and 67%, respectively. Also, the hardness and modulus increased by 17% and 60% each. As for the elongation at break, it had a decrease of 69% and then an increment of about 77%. These results appeared due to the low molecular 1 weight of the BRR800 and the presence of processing oil and carbon black in the reclaimed rubber itself. This study could prove that reclaimed rubber can be fully utilized by putting it to good use in producing good quality rubber-based products.

Possible Application of Activated Palm Kernel Shell (APKS) from Palm Oil Industry as Potential Filler in Carboxylated Nitrile Butadiene Rubber (XNBR)

In this study, different APKS loadings from 0 phr to 50 phr were incorporated into the carboxylated butadiene rubber (XNBR). The average filler particle size was identified as between 1.217 to 31.944μm based on particle size analysis. The curing, crosslink density, tensile properties, and morphology values of the APKS-filled XNBR were studied. The incorporated APKS has increased the crosslink density, delta torque, cure time (t90), and decreased the swelling degree of the XNBR. The overall mechanical properties were enhanced due to the mechanical interlocking of rubber-filler phases until the optimum APKS loading which was 40 phr.

Utilization of engineered silicate dispersion as a cost-effective cheapener and engineered carbonate dispersion as novel reinforcing additives for nitrile latex glove application

Utilization of silicate minerals fillers in latex offer dual function as a compatible filler and cheapener that economical way to reduce latex consumption. This research explores the effect of using Engineered Silicate Composite Dispersion (ESD 086) as fillers for nitrile latex-supported gloves, seeking to explore their properties while ensuring cost-effectiveness. The reinforcement effect of novel Engineered Carbonate Dispersion (ECD 011) for ESD 086 filled Carboxylated Nitrile Butadiene Rubber (XNBR/ESD 086) latex films has also been explored. XNBR latex films were compounded with three variants of ESD 086 at different loadings (in phr). From three variants of ESD 086 fillers, variant ESD 086A at 10 phr shows the highest tensile strength. As the ESD 086A filler loading increased up to 15 phr, the tensile strength decreased, indicating the ineffectiveness to be used at higher loading. The work was continued by exploring the use of novel ECD 011 to minimize the decrement effect. The 15 phr ESD 086 filled XNBR latex films (XNBR/ESD 086A-15) were subjected to a hybrid loading from 0 to 1.2 phr with 0.2 phr staggered increment together with the reduction of ECD 011:ZnO ratio in the XNBR latex compounds. Results show that at 0.6:0.6 phr of ECD 011:ZnO, the tensile strength of XNBR/ESD 086A-15 latex films increased and the elongation at break also improved. Using ESD 086A can reduce the usage of XNBR latex. Still, it can only be used up to 10 phr (optimum loading) and ECD 011 can maintain the physical properties and offer maximum cost-saving options for XNBR latex glove formulation at higher loading of ESD fillers. Overall, both engineered dispersions offer potential commercial benefits for the Nitrile gloves industry.

Sustainable and greener coatings produced from accelerator‐ and sulfur‐free polyurethane dispersion/carboxylated nitrile butadiene latex blends

AbstractThis study is aimed at producing polyurethane dispersion (PUD)/carboxylated nitrile butadiene rubber (XNBR) blends without using accelerators and sulfur. The PUD/XNBR (at blending ratios of 90:10, 80:20, 70:30, and 60:40) was prepared using coagulation and latex dipping technology. The result demonstrated that increasing XNBR in the PUD/XNBR blends increased the zeta potential of the blends up to −71.8 mV. Fourier transform infrared (FTIR) studies show hydrogen interaction bonding exists between XNBR and PUD, which significantly impacts the degree of phase mixing, degree of phase separation and relative change of hard segment separation of the PUD. The surface energy of the PUD blend is reduced from 34.68 ± 0.23 to 22.28 ± 0.63 mJ−2 with increasing XNBR loading. The presence of XNBR had increased the polar component of the surface energy, but a further increase of the XNBR amount to more than 20% had reduced the tensile strength. Overall, loading 20% of XNBR (PUD80) showed the best performance by having an improvement in tensile strength compared to pristine PUD.

Crosslinking ofXNBRlatex with multifunctional epoxides: An energy‐efficient curing strategy for the fabrication of accelerator‐free rubber gloves

AbstractHerein, we pursue an efficient curing strategy using multifunctional epoxides, which undergo a nucleophilic ring opening reaction across the free COOH groups of a carboxylated nitrile butadiene rubber (XNBR). Following a prevulcanization protocol, we cure the rubber in the latex phase at 60°C. Thin films are then prepared by using a conventional coagulant dipping process, in which the final cure degree of the elastomer is reached during drying (postvulcanization). In a comprehensive approach, cure kinetics, tensile properties, and crosslink density of the thin elastomer films are studied as a function of the functionality and concentration of the applied crosslinker. The results clearly show that films with high tensile strength (39 MPa) are obtained without prevulcanization. Stability tests reveal that the shelf life of the latex formulations is limited to less than 1 day due to hydrolysis reactions of the epoxy groups of the water‐soluble crosslinker. However, the storage stability can be extended to several days if nonwater‐soluble epoxy crosslinkers are applied. The decent shelf life together with the fast cure rates and excellent mechanical properties make epoxy crosslinking a promising curing strategy for preparing dipped rubber gloves without hyperallergenic accelerators used in classical sulfur vulcanization.

Nanokaolin reinforced carboxylated nitrile butadiene rubber/polyurethane blend-based latex with enhanced tensile properties and chemical resistance

The demand for gloves (e.g., disposable gloves, medical gloves) is increasing due to the Coronavirus disease 2019 (COVID-19) pandemic. Stability in the supply chain in the glove industry is important, and thus strategies are used to solve the problem of the shortage of nitrile gloves. The blending of nitrile butadiene rubber (NBR) with polyurethane (PU) and the use of the nanocomposite concept is among the feasible approaches. The present study aims to investigate the effects of nanokaolin (NK) on the tensile and chemical properties of carboxylated nitrile butadiene rubber (NBR)/polyurethane (PU) latex blends. Three different loadings of NK (10, 20, and 30 parts per hundred rubber) were added to the NBR/PU (at a blending ratio of 85/15). The zeta potential showed that all the NBR compounds exhibit good colloidal stability. The incorporation of NK increased the crosslink density and tensile strength of the NBR/PU latex blends. The highest tensile strength was achieved when the NK loading was 20 phr. All the NBR blends and nanocomposites (NBR/PU-based) possess tensile properties that fulfill the requirements for glove application. The chemical resistance of NBR compounds was increased by the incorporation of NK due to the higher crosslink density and barrier properties contributed by the NK.

Synergistic Effect of Partial Replacement of Carbon Black by Palm Kernel Shell Biochar in Carboxylated Nitrile Butadiene Rubber Composites.

With the rapid development of the palm oil-related industry, this has resulted in the high production of palm oil waste. The increasing amount of palm oil waste has become an alarming issue in which researchers have carried out studies that this palm oil waste has the potential to be used as a biomass source. Carbon black (CB) is the most preferred reinforcing filler in the rubber industry but it has a disadvantage where CB is carcinogenic and a petroleum-based product. Hence CB is less sustainable. Palm kernel shell (PKS) derived from palm oil waste can be turned into palm kernel shell biochar (PKSBc) which can potentially be a value-added, sustainable biofiller as reinforcement in rubber composites. In this study, PKSBc is hybridized with CB (N660) at different loading ratios to be filled in carboxylated nitrile butadiene rubber (XNBR). This study aims to elucidate the effect of the varying ratios of hybrid CB/PKSBc on the rheological properties, abrasion resistance, and hardness of XNBR composites. In this study, both CB and PKSBc are incorporated into XNBR and were then cured with sulphur. The composites were prepared by using a two-roll mill. Different compositions of hybrid CB/PKSBc were incorporated. The rheological properties and physicomechanical properties, such as abrasion resistance and hardness of the vulcanizates, were investigated. Based on the results, as the loading ratio of PKSBc in hybrid CB/PKSBc increases, the cure time decreases, and the cure rate index increases. The abrasion resistance and hardness values of vulcanizates were maintained by the high loading of PKSBc which was due to the porous structure of PKSBc as shown in the morphological analysis of PKSBc. The pores of PKSBc provided mechanical interlocking to reduce volume loss and maintain the hardness of vulcanizates when subjected to force. With this, PKSBc is proven to be a semi-reinforcing filler that could not only act as a co-filler to existing commercialized CB, but PKSBc could also fully substitute CB as reinforcement in rubber, specifically XNBR as it is able to provide high abrasion resistance and hardness to the rubber composites. This would mean the performance of PKSBc is comparable with CB (N660) when it comes to maintaining the physicomechanical properties of XNBR composites in terms of abrasion resistance and hardness. Therefore, this approach of using eco-friendly filler derived from palm oil agricultural waste (PKSBc) can reduce the abundance of palm oil waste, be a sustainable alternative to act as a co-filler in hybrid CB/PKSBc to decrease the usage of CB, and helps to enhance the quality of existing rubber-based products.

Thin Solid Electrolyte Separators for Solid-State Lithium–Sulfur Batteries

The lithium-sulfur battery is one of the most promising "beyond Li-ion" battery chemistries owing to its superior gravimetric energy density and low cost. Nonetheless, its commercialization has been hindered by its low cycle life due to the polysulfide shuttle and nonuniform Li-metal plating and stripping. Thin and dense solid electrolyte separators could address these issues without compromising on energy density. Here, we introduce a novel argyrodite (Li6PS5Cl)-carboxylated nitrile butadiene rubber (XNBR) composite thin solid electrolyte separator (TSE) (<50 μm) processed by a scalable calendering technique and compatible with Li-metal. When integrated in a full cell with a commercial tape-cast sulfur cathode (3.54 mgS cm-2) in the presence of an in situ polymerized lithium bis(fluorosulfonyl)imide-polydioxolane catholyte and a 100 μm Li-metal foil anode, we demonstrate stable cycling for 50 cycles under realistic operating conditions (stack pressure of <1 MPa and 30 °C).

Lithiated carboxylated nitrile butadiene rubber with strong polysulfide immobilization ability as a binder for improving lithium-sulfur battery performance

We report the first use of lithiated carboxylated nitrile butadiene rubber (XNBR-Li) as a functional binder for the sulfur cathode of lithium sulfur batteries (LSBs). XNBR-Li has strong adhesion to sulfur and carbon black particles, forming a uniformly dispersed and robust sulfur cathode structure. Furthermore, due to the presence of the -COOLi groups, XNBR-Li has shown a strong ability to trap lithium polysulfides (LPS), which greatly helps to suppress the shuttle effect of LPS in LSBs. The cyclic voltammetry and electrochemical impedance spectroscopy data indicate that the use of XNBR-Li as the binder can accelerate Li+ diffusion kinetics in the sulfur cathode. As a result, the XNBR-Li-based cathode delivers a high capacity of 1140 mAh g −1 at 0.2 C, high rate performance with a capacity of 729 mAh g−1 at a high rate of 2 C, and excellent long-term cycling stability with a slow capacity decay rate of 0.04% per cycle at 0.5 C over 500 cycles.