Nitrile Butadiene Rubber Matrix Research Articles

Versatile fabrication of palygorskite/diene-based rubber nanocomposites via autogenous-modification and sulfur co-vulcanization strategy

The dispersion and stability of nanofillers in polymer matrices are the main challenges in polymer nanocomposites, especially the rubber nanocomposites. Here, autogenous-modification of nanofillers was proposed for a good dispersion, and therefore a good stability could be achieved via sulfur co-vulcanization with rubber matrix. With the palygorskite (Pal)/nitrile-butadiene rubber (NBR) nanocomposite as an example, NBR chains could be introduced onto the Pal nanorods via surface cross-metathesis reaction, and then the resultant NBR grafted Pal nanorods (NBR-Pal) could be co-vulcanized with NBR matrix. The incorporation of the Pal nanorods in the crosslinked network was revealed by the X-ray photoelectron spectroscopy (XPS) analysis after de-vulcanization. The proposed strategy is expected to impel the mass production and practical application of high-performance diene-based rubber nanocomposites.

A novel and sustainable rubber composite prepared from electric arc furnace slag as carbon black replacement

Carbon black (CB) is the most widely used reinforcing filler for rubber. Nowadays there are several concerns regarding this traditional petroleum-based filler: on one side its environmental footprint is enormous and its production process is no more sustainable and on the other side its price increases annually. For these reasons, sustainable alternative fillers are being studied. In the present research the main waste of the steel industry, namely the steel slag from electric arc furnace (EAF), is investigated as non-conventional filler for a nitrile butadiene rubber matrix (NBR). The slag has been characterized to ensure its safe reuse as filler according to the heavy metals leaching. The slag filled compounds have been characterized and compared to CB filled compounds, in terms of processability by rheometric parameters, mechanical properties, Payne effect, and physicochemical properties to investigate the filler-matrix interaction. From the obtained results, it was shown that EAF slag-filled NBRs are comparable to CB filled NBRs in terms of crosslink kinetics and, when compared at the same hardness level, are comparable in terms of viscosity, stiffness, and elongation at break, while when compared at the same filler volume fraction are similar in terms of compression set and stress relaxation.

A feasible way to modify microcrystalline cellulose powder and its reinforcing effect for NBR composites

AbstractIt has attracted tremendous attention for replacing petroleum‐based carbon black or mineral fillers with renewable, biology‐based and low‐cost cellulose. However, the reinforcing effect of cellulose, especially at the microscale, is still a great challenge in the polymer industry. In this work, a feasible surface modification method for microcrystalline cellulose powder (MCC) in all solid states is proposed by using rubber accelerators N‐cyclohexyl benzothiazole‐2‐sulphenamidee (CBS) and 2,2′‐dibenzothiazoledisulfide (DM). These accelerators not only accelerate the sulfur crosslink of nitrile butadiene rubber (NBR), but also graft to rubber molecular chains and form hydrogen bonds with MCC, resulting in good interfacial interaction and good dispersion of MCC in the NBR matrix. As a consequence, the tensile strength and elongation at break of NBR/10MCC reach up to 20.12 MPa and 511%, respectively, which are the highest values of NBR/MCC or cellulose nanocrystals (CNCs) composites we can find in the world and are comparable to those of carbon black or mineral fillers. This provides a more effective and environmentally friendly way of using MCC or CNCs in the polymer industry.Highlights Microcrystalline cellulose powder can reinforce NBR. Hydrogen bonds have been established between accelerators and MCC. The tensile strength of NBR/10MCC composite reaches 20 MPa. The reinforcing mechanism is ascribed to the immobilized rubber layer.

Polydopamine in‐situ polymerized on graphene oxide for nitrile butadiene rubber with high strength, elasticity and aging resistance

AbstractThe elasticity and aging resistance of nitrile butadiene rubber (NBR) will be reduced by reinforced filler. Herein, we report that polydopamine (PDA) polymerized in situ on graphene oxide (GO) to obtain polydopamine‐graphene oxide (PDA‐GO) nanofiller for simultaneously improving strength, elasticity and thermal oxidative aging‐resistant performance of NBR. The structure, composition and morphology of PDA‐GO and NBR composites were characterized. The effect of PDA‐GO on the performance of NBR was investigated. Results show that PDA microspheres improved the dispersion of GO in matrix. With incorporation 3 phr of PDA‐GO, the tensile strength of NBR raised from 3.8 to 9.2 MPa. It is satisfactory that the elasticity is also improved significantly. PDA‐GO/NBR composite equips better thermal oxidative stability and aging resistance. The tensile strength of 3 phr‐PDA‐GO/NBR after aging is even 3.4 MPa higher than that of unfilled NBR before aging. Our work proposes an insight for the manufacture of rubber composites with high strength, elasticity and aging resistance.Highlights GO modified by PDA is prepared via an in‐situ polymerization process. In situ polymerized PDA microspheres greatly promotes the dispersion of GO in NBR matrix. NBR filled with PDA‐GO shows a superior strength and elasticity simultaneously. PDA‐GO endows NBR with prominent performance in aging resistance.

An experimental investigation on the matrix dependent rheological properties of MRE

The rheological properties of magnetorheological elastomers are influenced by magnetically sensitive fillers and the elastomer matrix. The ability to respond to an external magnetic field is imparted by the fillers, while the load-bearing capability is determined by the matrix type. In this paper, the effect of matrix material on the properties of magnetorhological elastomer is explored experimentally. Carbonyl iron particle content is varied by 0%, 15% and 25% by volume to produce magnetorheological elastomer samples using natural rubber, silicone rubber and nitrile butadiene rubber matrices. Forced transmissibility test approach was employed to evaluate the field induced variations in the dynamic stiffness and loss factor of magnetorheological elastomers. The dynamic stiffness of nitrile butadiene rubber is the highest, while that of silicone rubber is the lowest. Addition of carbonyl iron particles significantly improves stiffness, although these gains depend on the properties of unfilled matrix. The addition of 25% by volume of carbonyl iron particle increased the dynamic stiffness of a silicone rubber matrix based magnetorheological elastomer by 67.78%, while the similar change in magnetorheological elastomer with nitrile butadiene rubber matrix was 38.58%. The field dependent response of magnetorheological elastomers is governed by the matrix and ferromagnetic filler concentration. These qualities are higher in magnetorheological elastomer with a low initial dynamic stiffness matrix and lower in magnetorheological elastomers with a stiffer matrix.

Phase-Separated Structure of NBR/PVC Blends with Different Acrylonitrile Contents Investigated Using STEM-EDS Mapping Analysis.

We investigated the phase-separated structure of nitrile butadiene rubber (NBR)/polyvinyl chloride (PVC) blends with different acrylonitrile (AN) contents in the NBR, using dynamic mechanical analysis measurements and scanning-transmission-electron-microscopy (STEM)-energy-dispersive-X-ray-spectroscopy (EDS) elemental analysis. Two separate sharp tan δ peaks were observed in the blend at the lower AN content of 18.0%, whereas a broad peak was observed in the blends with the higher AN contents of 29.0 and 33.5%, due to the increase in miscibility, as expected from the decrease in the solubility parameter difference with the increasing AN content. The STEM-EDS elemental analysis for the concentration distribution showed that the NBR was mixed in the large PVC domains with a diameter of several micrometers, and the excluded PVC existed around the interface of the domain-matrix phases in the blend with the lower AN content, whereas small domains with a diameter of several tens of nanometers were dispersed in the blend with the higher AN content. The concentration difference in PVC between the PVC domain and the NBR matrix became smaller with increasing miscibility as the AN content increased although the blends contained the same PVC content of 40 wt%.

Effect of triethylene glycol bis(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionate on structure and mechanical properties of nitrile butadiene rubber/clay nanocomposites

AbstractClay modification by organic ammonium salts has been widely introduced in rubber/clay nanocomposites, but it is inapplicable in the polar rubbers to achieve high performance due to bad dispersion and poor compatibility. In this work, gel‐compounding method was utilized to prepare nitrile butadiene rubber (NBR)/clay nanocomposite, and then a hindered phenol antioxidant, triethylene glycol bis(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionate (AO‐245) with various contents, was mechanically blended to enhance the interactions in the nanocomposites. The elongation at break increases while the Shore A hardness, permanent set and stress at 100% or 300% strain decrease by adding AO‐245 into the nanocomposites. By adding only 5 phr AO‐245 in the nanocomposite, the tensile strength and elongation at break increased from 18.3 MPa and 521% to 20.5 MPa and 646%, respectively, which resulted from the repeated destruction/construction of the hydrogen bonds between AO‐245 and NBR. At high AO‐245 content, both clay networks and AO‐245 aggregate networks coexist in the nanocomposite, and the excess AO‐245 in the NBR matrix can form a separated phase leading to a new internal friction peak.

Aminosilane modified graphene oxide for reinforcing nitrile butadiene rubber: Experiments and molecular dynamic simulations

Graphene oxide (GO) was chemically modified by 3-aminopropyl)triethoxysilane. The modified GO (denoted as MGO) was used to reinforce nitrile butadiene rubber (NBR). The occurrence of the chemical modification was confirmed by various characterization techniques. NBR/GO (or MGO) composites were prepared by a mechanical blending process. Their mechanical and tribological properties of NBR-GO/MGO nanocomposites were investigated. The NBR/MGO composites exhibited superior performances compared to their NBR/GO counterparts over the GO (or MGO) range of 1–5 wt%. The tensile strength of the NBR/MGO (1phr) was increased by 43.7% and 30.3%, and the abrasion loss was decreased by 59.3% and 58.9% with regard to the NBR and NBR/GO composite, respectively. The morphologies of the fractured and worn surfaces of the composites were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy to reveal the reinforcement mechanisms of MGO. The pull-out behavior of the GO or MGO from the NBR matrix and the interlayer peel-off behavior of the GO or MGO were described by molecular dynamic simulations. The stress required to pull the MGO off the NBR matrix was 121.2% that for the GO, while that of the interlayer peel-off for the MGO was 36.7% that for the GO. This explains the fact that the MGO was able to be better dispersed in the NBR than the GO and consequently better reinforce the mechanical and tribological properties of the latter.

Preparation and properties of the aramid pulp/nitrile butadiene rubber composites with compatibilization of ionic liquids

AbstractTo improve the uniformity and the mechanical/wear performances of the aramid pulp (AP)/nitrile butadiene rubber (NBR) composites, two types of ionic liquids (ILs), that is, 1‐carboxymethyl‐3‐methylimidazolium chloride ([CmMIM]Cl) and 1‐allyl‐3‐vinylimidazolium chloride ([AVIM]Cl) were applied on the AP surface, respectively. The ILs partially disrupted the hydrogen‐bonds between the aramid chains to mitigate the fiber entanglement, and connected the AP to the rubber matrix by hydrogen‐bond interaction or the crosslinking reaction during the vulcanization. The test results showed that, the IL treatments effectively improved the tensile and tear strengths without obviously affecting the physical characteristics of the composites. The wear properties of the AP/NBR composites also improved due to the enhancements of the tear strength and the connection between the AP and NBR matrix. Compared to the [CmMIM]Cl, the [AVIM]Cl was more efficient to improve the properties attributed to its better compatibilization for the AP/NBR system. For example, the specific wear rate under 20‐N load of the composite with 15‐phr [AVIM]Cl‐AP was 1.1 × 10−7 mm3 N−1 mm−1, which was approximately 25% and 35% lower than that of the composites reinforced with 15‐phr [CmMIM]Cl‐AP and untreated AP, respectively.

Effects of Eucommia ulmoides gum content and processing conditions on damping properties of E. ulmoides gum/nitrile-butadiene rubber nanocomposites

Abstract In order to improve the effective damping of nitrile-butadiene rubber (NBR) in a wider temperature range, Eucommia ulmoides gum (EUG) was incorporated into NBR to prepare nanocomposites. Atomic force microscopy (AFM) showed that EUG was dispersed in NBR matrix in the form of nanocrystals. Compared with pure NBR, the mechanical properties of NBR/EUG (80/20) composites are significantly improved. Dynamic thermo-mechanical analysis (DMA) showed that there are two dynamic mechanical loss peaks in two composites. With the increase of EUG component, the peak value of loss factor (tanδ) decreases gradually at −10 °C, and the temperature corresponding to the peak value tends to move towards high temperature, while the peak area increases gradually at −50 °C. Parking and repeated mixing make both loss peaks move towards high temperature. The differential scanning calorimetry analyzer (DSC) results expressed that the melting temperature and peak area of EUG after vulcanization decreased significantly compared with that before vulcanization. Hence, the damping effect of NBR can be improved and its damping temperature range can be widened by adding EUG and changing processing conditions.

Effects of graphene and CNTs reinforcement on the friction mechanism of nitrile butadiene rubber under water lubrication conditions

Nitrile butadiene rubber (NBR) is a water-lubricated bearing material that demonstrates excellent vibrational absorption and impact resistance; however, rapid wear under abnormal conditions is still a serious problem. Graphene (Gra) and carbon nanotubes (CNTs) are two types of carbon nanomaterials with different dimensions and excellent mechanical and friction properties. In this work, Gra and CNTs were used to fill the NBR, and a multifunctional friction and wear testing machine was used to study their impacts on the friction between NBR and ZCuSn10Zn2 under water lubrication conditions. The results indicate that both Gra and CNTs can effectively reduce the adhesion and the friction coefficient of NBR during the friction process. The two-dimensional lamellar structure of Gra is more likely to precipitate from the NBR matrix to generate a surface lubrication film, which can effectively reduce the friction coefficient. Both Gra and CNTs can prevent crack initiation and propagation in NBR during the wear process, thereby effectively reducing the wear of NBR. Compared with the two-dimensional structure of Gra, the one-dimensional linear structure of carbon nanotubes can “trap” the NBR molecular chains more effectively during the friction process, thus reducing the initiation and propagation of wear cracks and further improving the wear performance of NBR.

Mechanical Properties of Amide Functionalized CNT/NBR at Different Temperatures: A Molecular Dynamics Study.

A comprehensive study on the mechanical properties of a pure carbon nanotube (PCNT)/nitrile butadiene rubber (NBR) composite and an amide-functionalized carbon nanotube (CONH2–CNT)/nitrile butadiene rubber (NBR) composite was carried out using molecular dynamics (MDs) simulations at different temperatures. The effects of temperature on the mechanical properties, fractional free volume (FFV), MSD, dipole autocorrelation function, number of hydrogen bonds of PCNT composites, and functionalized CNT composites were analyzed and compared, and the pull-out behavior of the composites under different condition temperatures was simulated. The enhancement mechanism of the interface interaction between the functionalized carbon nanotubes and the NBR matrix was explained from an atomic point of view. The results show that, due to the existence of hydrogen bonds, higher interfacial binding energies were formed between PCNT and NBR, and FFVs and MSDs were restricted at each temperature, with the mechanical properties of the composites being improved by 5.02–25.93%.

Graphene Nanoplatelets as a Replacement for Carbon Black in Rubber Compounds.

In this work, we evaluated the processing and reinforcement characteristics of both carbon black (CB) and graphene nanoplatelets (GNPs) within a nitrile butadiene rubber (NBR) matrix. The aspect ratio of the GNPs was measured using atomic force microscopy (AFM) and related to the dispersion and agglomeration within the NBR matrix, as observed by scanning electron microscopy (SEM). The relationship between GNP aspect ratio and mechanical properties was studied by micromechanical modelling. The tensile and tear properties of NBR after compounding with GNPs were enhanced to a greater extent compared to carbon black, while curing times were smaller and scorch times longer, indicating some of the advantages of using GNPs. Overall, the inherent properties of GNPs along with their geometry led to the production of better-performing rubber compounds that can replace their CB-filled counterparts in applications where flexibility, tear strength and compliance are important. The influence of processing on dispersion, orientation and agglomeration of flakes was also highlighted with respect to the Young’s modulus of the NBR compounds.

Investigation of the Compatibility and Damping Performance of Graphene Oxide Grafted Antioxidant/Nitrile-Butadiene Rubber Composite: Insights from Experiment and Molecular Simulation.

Rubber damping materials are widely used in electronics, electrical and other fields because of their unique viscoelasticity. How to prepare high-damping materials and prevent small molecule migration has attracted much attention. Antioxidant 4010NA was successfully grafted onto graphene oxide (GO) to prepare an anti-migration antioxidant (GO-4010NA). A combined molecular dynamics (MD) simulation and experimental study is presented to investigate the effects of small molecules 4010NA, GO, and GO-4010NA on the compatibility and damping properties of nitrile-butadiene rubber (NBR) composites. Differential scanning calorimetry (DSC) results showed that both 4010NA and GO-4010NA had good compatibility with the NBR matrix, and the Tg of GO-4010NA/NBR composite was improved. Dynamic mechanical analysis (DMA) data showed that the addition of GO-4010NA increased the damping performance of NBR than that of the addition of 4010NA. Molecular dynamics (MD) simulation results show GO-4010NA/NBR composites have the smallest free volume fraction (FFV) and the largest binding energy. GO-4010NA has a strong interaction with NBR due to the forming of hydrogen bonds (H-bonds). Grafting 4010NA onto GO not only inhibits the migration of 4010NA but also improves the damping property of NBR matrixes. This study provides new insights into GO grafted small molecules and the design of high-damping composites.

Mercaptopropyl-doped ultra-small silica modified GO nanosheets to enhance mechanical properties of nitrile butadiene rubber

Graphene oxide (GO) nanosheets reinforced rubbers had been extensively researched. However, it is very difficult to make GO nanosheets uniformly dispersed in the polar nitrile butadiene rubber (NBR) matrix and non-polar carbon black (CB) simultaneously. The ultra-small mercaptopropyl doped silica (HS@SiO2) anchored on the GO nanosheet (HS@SiO2-GO) has been synthesized through the condensation of the tetraethoxysilane (TEOS) and (3-Mercaptopropyl)trimethoxysilane (MPTS) monomer. The as-prepared mercaptopropyl doped silica modified graphene oxide has strong interfacial interaction with both the polar NBR matrix and non-polar carbon black nanoparticles. Excitingly, with only 1 phr of GO modified by HS@SiO2 has greatly improved the tensile strength of CB/NBR composites from 8.9 MPa to 16.1 MPa.

Utility of copper (lignin/silica/fatty acids) complex derived from rice straw as antioxidant/hardening and fluid resistant agent in nitrile-butadiene rubber composites (PART IV)

PurposeIn continuation to the previous work on copper (lignin/silica/fatty acids) (Cu-LSF) complex as a natural antioxidant/electrical conductivity agent for nitrile-butadiene rubber (NBR), this study aims to perform further investigations for NBR vulcanizates loaded with different concentrations of Cu-LSF complex, including swelling behavior and hardness properties, as well as evaluating their thermal stability via thermogravimetric analysis.Design/methodology/approachThe behavior of Cu-LSF complex in NBR matrix was compared with that of the standard commercial antioxidants (2,2,4-trimethyl-1,2-dihydroquinoline/N-isopropyl-N′-phenyl-p-phenylenediamine [TMQ/IPPD]).FindingsResults revealed that Cu-LSF complex can act as an effective reinforcing and hardening agent, with exhibiting fluid resistance, even when compared with the commercial antioxidants. In comparison with the previous studies on its Zn and Ca analogues and their behavior in different rubber matrixes, Cu-LSF complex showed higher values of hardness and less susceptibility for swelling, respectively. Moreover, Cu-LSF antioxidant activity becomes in accordance with the previous work.Originality/valueThe new Cu-LSF complex could be used as a green alternative to the commercial antioxidants (TMQ/IPPD) with introducing further advantages to the rubber matrix, such as hardening, fluid resistance and thermal stability.

Constructing of strawberry-like core-shell structured Al2O3 nanoparticles for improving thermal conductivity of nitrile butadiene rubber composites

In this paper, we have designed strawberry-like core-shell structured aluminum oxide/tannic acid-ferric ion/silver (Al2O3/TA-Fe3+/Ag) nanoparticles (NPs) and incorporated them into nitrile butadiene rubber (NBR) matrix to obtain thermally conductive composites. The tannic acid (TA) provided a strong binding affinity to the surface of Al2O3 NPs and formed a stable octahedral complex with Fe3+. Moreover, the TA layer enhanced interfacial interactions and compatibility between thermally conductive filler and NBR matrix, leading to reduced phonon scattering and decreased interfacial resistance of NBR composites. As a result, the incorporation of Ag NPs on the surface of Al2O3/TA-Fe3+ enhanced the thermal conductivity (λ) of NBR composites. The results revealed that the λ of 50 vol% Al2O3/TA-Fe3+/Ag/NBR composite was 0.90 W/mK, which was 600% of pure NBR (0.15 W/mK). Meanwhile, the dielectric constant (ϵr) of 50 vol% Al2O3/TA-Fe3+/Ag/NBR composite reached up to 12.91 at 102 Hz. However, the volume resistance of all Al2O3/TA-Fe3+/Ag/NBR composites was larger than 1.97 × 1011 Ω mm. Overall, the proposed low-cost and green surface modification method provides novel insights into the design of advanced polymeric composites with high λ for large-scale production.

S4-Containing hyperbranched polymer modified graphene oxide as strong linker for both rubber and carbon black to enhance the crosslinking and mechanical properties of nitrile butadiene rubber

• S 4 -containing hyperbranched polymer modified graphene oxide was synthesized. • It shows strong interaction with both nitrile butadiene rubber and carbon black. • The tensile strength of new composites increased from 8.9 MPa to 17.0 MPa. Graphene oxide (GO) nanosheets reinforced rubbers had been well studied. However, it is very difficult to make GO nanosheets uniformly dispersed in the polar nitrile butadiene rubber (NBR) matrix and non-polar carbon black simultaneously. The hyperbranched polymer of bis(triethoxysilylpropyl) tetrasulfide (BTESPT) grafted on the GO nanosheet (HSi-GO) has been synthesized through the catalytic condensation of the BTESPT monomer. The as-prepared S4-Containing hyperbranched polymer modified graphene oxide has strong interfacial interaction with both the polar NBR matrix and non-polar carbon black nanoparticles. Excitingly, HSi-GO has greatly improved the tensile strength of NBR/CB composites from 8.9 MPa to 17.0 MPa.

Direct transformation of fatty acid-derived monomers from dimer acid manufacturing into valuable bio-plasticizers with high plasticization and compatibilization

Abstract Direct transformation of monomer fatty acids derived from the dimer acid manufacturing into high value-added green plasticizers represents a sustainable approach for reutilizing industrial wastes. However, this process is challenging due to the few double bonds and long-chain alkyl in monomer fatty acid-based derivatives, resulting in poor compatibility with polymer matrix and inferior plasticization. Herein, we develop a sustainable and low-cost strategy via direct esterification between monomer fatty acids and polyethylene glycol methyl ether to produce plasticizers featured by high plasticization and compatibilization. The performances of monomer acid-based ethoxylated esters as resulting plasticizers for nitrile butadiene rubber were highly structure-dependent. Extensive experiments demonstrated that oxethyl unit played critical roles in both improving the compatibility between monomer acid-based ethoxylated esters and nitrile butadiene rubber and in promoting the dispersion of carbon black in nitrile butadiene rubber matrix. Specially, the processing, freezing resistance, oil resistance, thermal and mechanical stabilities of nitrile butadiene rubber plasticized by monomer acid-based ethoxylated esters with three or four oxethyl units were comparable or better than those of nitrile butadiene rubber blended with dioctyl phthalate. This study opens a simple, general and industrialized strategy to produce valuable and sustainable plasticizers as alternatives of toxic dioctyl phthalate.

Biocompatible, Flexible Strain Sensor Fabricated with Polydopamine-Coated Nanocomposites of Nitrile Rubber and Carbon Black.

A flexible, biocompatible, nitrile butadiene rubber (NBR)-based strain sensor with high stretchability, good sensitivity, and excellent repeatability is presented for the first time. Carbon black (CB) particles were embedded into an NBR matrix via a dissolving-coating technique, and the obtained NBR/CB composite was coated with polydopamine (PDA) to preserve the CB layer. The mechanical properties of the NBR films were found to be significantly improved with the addition of CB and PDA, and the produced composite films were noncytotoxic and highly biocompatible. Strain-sensing tests showed that the uncoated CB/NBR films possess a high sensing range (strain of ∼550%) and good sensitivity (gauge factor of 52.2), whereas the PDA/NBR/CB films show a somewhat reduced sensing range (strain of ∼180%) but significantly improved sensitivity (gauge factor of 346). The hysteresis curves obtained from cyclic strain-sensing tests demonstrate the prominent robustness of the sensor material. Three novel equations were developed to accurately describe the uniaxial and cyclic strain-sensing behavior observed for the investigated strain sensors. Gloves and knee/elbow covers were produced from the films, revealing that the signals generated by different finger, elbow, and knee movements are easily distinguishable, thus confirming that the PDA/NBR/CB composite films can be used in a wide range of wearable strain sensor applications.