Natural Rubber Films Research Articles

Influence of Different Grafted Natural Rubbers on Electrical and Mechanical Properties of Natural Rubber/Carbon Nanotubes Composites

This study investigates the augmentation of electrical and mechanical characteristics of natural rubber (NR) film with different forms by integrating carbon nanotubes (CNTs). NR with different forms (i.e., natural rubber grafted with polystyrene (NR–g–PS) and polybutyl methacrylate (NR–g–PBMA)) were successfully synthesized. The success of these grafting was confirmed through Proton Nuclear Magnetic Resonance (1H–NMR) and Attenuated Total Reflectance–Fourier Transform Infrared (ATR–FTIR) analyses, which showed that the grafting efficiency exceeded 90%. The properties of ungrafted NR and grafted NRs with CNTs were compared and analyzed. It was found that the NR/CNTs composites with grafting displayed significantly improved electrical properties and mechanical strength when compared to the NR/CNTs composites without grafting. It was found that the NR–g–PBMA exhibited an 860% increase in electrical conductivity at 100 kHz compared to ungrafted NR. This might be attributed to the synergistic of the high specific surface of CNTs and the high polarization of functional groups, which gave a higher value for the CNTs filled grafted NR than the ungrafted NR. Moreover, the mechanical properties of NR–g–PS composites showed a 114% increase in 100% modulus, 127% in tensile strength, and 37% in hardness, while the NR–g–PBMA composites exhibited a 159% increase in 100% modulus, 95% in tensile strength, and 34% in hardness compared to ungrafted NR. This enhancement can be attributed to the formation of chemical linkages between the grafted NR matrix and CNTs through functional groups from both. Consequently, it can be concluded that introducing functional groups on grafted NR assists in establishing a crosslinking network, enhancing both the mechanical and electrical properties. Additionally, this research emphasizes the benefits of producing flexible conductive materials with high modulus and enhanced electrical properties. Keywords: Natural rubber latex, Graft copolymerization, Glutaraldehyde, Natural rubber composites, Electrical properties

Structural features of polylactide and natural rubber films produced by solution casting

Composite film samples of polylactide-natural rubber with a rubber content of 5, 10 and 15 wt. % were obtained by the solution method. The study of morphology showed the presence of rubber inclusions in the form of drops in the polylactide matrix. Thermophysical characteristics were determined by differential scanning calorimetry. It was determined that when rubber was added, the peak of cold crystallization of polylactide disappears on melting thermograms, the melting temperature decreases by 1–4°C compared to 100% polylactide. The structure of the obtained compositions was studied by nuclear magnetic resonance, electron paramagnetic resonance, and X-ray diffraction. The diffraction patterns of the samples contain reflections characteristic of the crystalline α-form of polylactide.

Natural Rubber Films Reinforced with Cellulose and Chitosan Prepared by Latex Aqueous Microdispersion.

In this paper, green composite films comprising natural rubber (NR), cellulose (CE), and chitosan (CS) were successfully fabricated through a simple, facile, cost-effective method in order to improve mechanical, chemical, and antimicrobial properties of NR composite films. Chitosan with a low molecular weight of 30,000-50,000 g/mol (CS-L) and a medium molecular weight of 300,000-500,000 g/mol (CS-M) was used for the fabrication. The composite films were prepared via a latex aqueous microdispersion method with different weight ratios of NR:CE:CS-L/CS-M. Fourier transform infrared spectroscopy (FTIR) results demonstrated strong interactions of hydrogen bonds between CE and CS-L/CS-M in the composite films. The tensile strength and the modulus of the composite films in dried form were found to significantly increase with the reinforcement of CE and CS-L/CS-M. The maximum tensile strength (13.8 MPa) and Young's modulus (12.7 MPa) were obtained from the composite films reinforced with CE at 10 wt.% and CS-L at 10 wt.%. The high elongation of 500-526% was obtained from the composite films reinforced with CE at 10 wt.% and CS (CS-L or CS-M) at 5.0 wt.%. The modification could also significantly promote antimicrobial activities and chemical resistance against non-polar solvents in the composite films. The NR composite films have potential uses as flexible films for sustainable green packaging.

Grafting photochromic spiropyran polymer brushes on natural rubber surface via surface-initiated ring-opening metathesis polymerization

The modification of stereoregulated functionalized polymers on the surface of natural rubber (NR) is a challenging task. This work provided a practicable grafting method to design photochromic polymer brushes on the NR surfaces using surface-initiated ring-opening metathesis polymerization (SI-ROMP). The designed photochromic polymer brushes were based on norbornenes with spiropyrin (SP) pendents, and grew from the surface of NR films in the presence of Grubbs 2nd catalyst. The results showed that the grafting rate of polymer brushes with photoisomerization structure reached up to 44.91 %. The modified natural rubber (NR-SP) films exhibited rapid coloring/decolorization property under UV irradiation and visible light. This photochromic property initiated by the light-induced isomerisation of the spiropyran structure and the increased surface energy under light stimuli. NR-SP films exhibited stable photochromic characteristics and outstanding anti-fatigue properties after exposing to over six cycles of consecutive UV/Vis irradiation. A simple and practical strategy for the preparation of highly sensitive photochromic natural rubber materials is proposed and provides a potential application in the fields of information storage and anti-counterfeiting.

ZnO Deposited on Natural Rubber Films by Different Coating Methods

ZnO Deposited on Natural Rubber Films by Different Coating Methods

Conductive NR/PMMA-RAFT-CNT-rGO composites and their morphological, mechanical, and electrical properties

This study reports the synthesis of poly(methyl methacrylate) (PMMA)-carbon nanotube (CNT)-reduced graphene oxide (rGO) emulsions via reversible addition-fragmentation chain-transfer (RAFT)-mediated surfactant-free emulsion polymerization using a hydrophilic chain transfer agent. The rGO was prepared by the modified Hummers method and reduced with L-ascorbic acid. The effects of the CNT:rGO ratios and CNT and rGO contents on the conversion and stability of emulsion were investigated. Increasing the CNT and rGO contents from 1 to 4 wt% decreased the monomer conversion, while all the samples remained as colloidal dispersions. The morphology of PMMA-CNT-rGO composites showed the incorporated arrangement of a linear CNT portion connected with the rGO sheet dependent on the CNT:rGO ratio. Various PMMA-CNT-rGO filled natural rubber (NR) cast films were prepared. The NR/PMMA-CNT-rGO composite film with a 1 wt% filler loading at a CNT:rGO ratio of 1:1 presented a quite high modulus value (3.08 MPa) and sufficient intrinsic electrical conductivity (1.36 S/m) due to its strong filler-matrix interaction. Thus, the PMMA-RAFT-CNT-rGO composites at a very low filler content can be used as an effective reinforcement to enhance the mechanical and electrical properties of NR films with a high compatibility between the fillers and NR matrix.

Effect of proteins as constituents of island-nanomatrix structure on vulcanization of natural rubber

Effect of proteins, constituents of the island-nanomatrix structure, on dispersion of zinc to natural rubber was investigated by transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX) and focused ion beam-scanning electron microscopy-energy dispersive X-ray spectroscopy (FIB-SEM-EDX). Films of natural rubber and deproteinized natural rubber (DPNR) prepared with urea were embedded in a mixture of ZnO, vulcanization accelerator and sulfur, and they were heated at 150 °C for 5 h. Migration of Zn from surface to inside of the films was observed by FIB-SEM-EDX. The Zn migrated from the surface to 14 μm for natural rubber, but not for DPNR. The optimum vulcanization time for natural rubber was short, i.e., about 4 min, whereas it was long for DPNR, i.e., about 15 min. To confirm the effect of the proteins, a latex-mixed rubber compound was prepared by mixing the latex with sulfur, ZnO and vulcanization accelerator followed by drying with a hotplate at 150 °C for 45 s since the proteins are segregated on the surface of natural rubber particles in the latex stage. Vulcanization was accelerated for the latex-mixed natural rubber compared with mechanically mixed natural rubber compound that was prepared by mixing natural rubber with ZnO, vulcanization accelerator and sulfur with a two-roll mill. The resulting latex-mixed natural rubber vulcanizate was superior in mechanical properties to the mechanically mixed natural rubber vulcanizate. It was found by rubber-state NMR spectroscopy that the difference in mechanical properties was attributed to the difference in the cis-1,4-average sequence length of the vulcanizates, which came from the difference in the dispersion of Zn.

Structural Features of Polylactide and Natural Rubber Films Produced by Solution Casting

Structural Features of Polylactide and Natural Rubber Films Produced by Solution Casting

Electrically Conductive Natural Rubber Composite Films Reinforced with Graphite Platelets.

Green natural rubber (NR) composites reinforced with synthetic graphite platelets, using alginate as a thickening and dispersing agent, were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The fabrication was performed using a latex aqueous microdispersion process. The research demonstrated the effective incorporation of graphite platelets into the NR matrix up to 60 parts per hundred rubbers (phr) without causing agglomeration or phase separation. Graphite incorporation significantly improved the mechanical strength of the composite films. NR with 60 phr of graphite exhibited the highest Young's modulus of 12.3 MPa, roughly 100 times that of the neat NR film. The reinforcement also strongly improved the hydrophilicity of the composite films, resulting in a higher initial water absorption rate compared to the neat NR film. Moreover, the incorporation of graphite significantly improved the chemical resistance of the composite films against nonpolar solvents, such as toluene. The composite films exhibited biodegradability at about 21% to 30% after 90 days in soil. The electrical conductivity of the composite films was considerably enhanced up to 2.18 × 10-4 S/cm at a graphite loading of 60 phr. According to the improved properties, the developed composites have potential applications in electronic substrates.

The mechanical and heat aging properties of natural rubber latex modified by carbon nanodots

AbstractDue to their unique structure and tuneable physical, optical, and electronic properties, carbon nanodots (CDs) become one of the perfect nano‐materials in many fields such as biomarkers, optical sensing, and catalysis. The application of CDs in modifying polymers has also attracted much interest. In this work, a simple process was employed for introducing CDs to modify natural rubber (NR) latex. Glucose was applied as the precursor to prepare CDs by hydrothermal method, subsequently, the crude CDs were directly added to NR latex at a very lower concentration to prepare NR/CDs films. The results of mechanical properties demonstrate that the 500% modulus, tensile and tear strength of NR composites are significantly improved by the introduction of CDs. When the theoretical loading of CDs is 2 phr, the tensile strength and tear strength of NR/CDs film reach to 33.1 MPa and 56.4 N/mm, and improve 17.8% and 29.4% than NR without CDs respectively. It is particularly noteworthy that when the amount of CDs is higher than 1.5 phr, the heat‐aging resistance of NR has been enhanced. It has been confirmed by crosslink density, dynamic mechanical analysis, and Fourier Transform Infrared Spectrometer analysis that CDs have a certain confinement effect on the mobility of rubber molecular segments through physical adsorption and chemical crosslinking. The Tube model theory was employed to calculate parameters of the network structure of NR/CDs films (based on the stress–strain curves), the results indicate that CDs give NR film more chemical crosslinking points and less entanglement network.Highlights The crude carbon nanodots are used to modify NR latex at a lower concentration The mechanical properties of NR films are obliviously improved The heat‐aging resistance of NR has been enhanced by adding carbon nanodots higher than 1.5 phr The Tube model theory are employed to analysis the crosslink network CDs give NR film more chemical crosslinking points and less entanglement network

Reversible thermochromic properties of bisphenol A aromatic phenolic resin's composite natural rubber film

Based on open system and solution copolycondensation method, 2,6-monosubstituted bisphenol A aromatic phenolic resin with M‾n of 1.133 × 103 g·mol−1 and PDI of 1.005, was prepared by microwave, using bisphenol A (BPA), terephthalaldehyde (TPD) and isophthalaldehyde (IPD) as monomers. The number of BPA and phthalaldehyde (TPD or IPD) monomers participating in alternating copolymerization were 3 and 3, respectively. TPD and IPD had similar and low activities, therefore their competitive polymerization reactivity ratio was consistent with raw materials' practical molar ratio. The resin's structure was confirmed by 1H NMR, 13C NMR and FTIR. Reversible thermochromic composite natural rubber film was prepared by resin as chromogenic agent. When mass ratio of crystal violet lactone, resin, mixed alcohols (cetyl alcohol and octadecanol) and natural rubber is 1:3.0:30:20, i.e. 0.0075:0.023:0.23 (0.14:0.09):0.15 (g), the composite film was obtained by salivation method. The composite film's total color difference (ΔE) is about 85, and its absorption-scattering color depth difference (ΔKS) values are averagely 15 and 40 at visible light zone of 480–600 nm and 600–660 nm at 20–35 °C respectively. Composite film has good thermal stability and recyclability stability.

Influence of different protein contents from several clonal varieties of Hevea brasiliensis latex on the properties of cured natural rubber film using glutaraldehyde (GA) as a curing agent

Natural rubber films were prepared from four different Hevea brasiliensis clones, namely RRIM600, RRIT251, PB235, and BPM24, using the creamed concentrated latex method. The creamed latexes were characterized by their protein content and particle sizes. The rubber particle surface characteristics were monitored using transmission electron microscopy (TEM). It was observed that the particle sizes of all clones varied in the range of 1.0–2.5 µm. Moreover, the RRIT251 clone exhibited higher protein content than the other clones. The influence of protein content on the properties of cured natural rubber (NR) was investigated using glutaraldehyde as a cross-linking agent. Mechanical properties, crosslink density, relaxation behavior, and heat resistance indicated by T90 (temperature scanning stress relaxation, TSSR) were considered. The crosslink density of cured NR increased with higher protein content. This phenomenon can be attributed to the strong formation of rubber chains with GA cross-links through the amino groups of proteins present in rubber molecules. Consequently, Hevea brasiliensis clones with higher protein content facilitate improved crosslink formation within the GA system, resulting in enhanced mechanical and thermo-oxidative degradation properties (T90 from TSSR test).

Extraction of Cellulose Nanocrystals and Nanofibers from Rubber Leaves and Their Impacts on Natural Rubber Properties

This study aimed to chemically isolate two distinct types of nanocellulose derived from rubber leaves and investigate their use in natural rubber (NR). The cellulose nanocrystals (CNCs) were obtained through acid hydrolysis, while oxidation with 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) was used to produce cellulose nanofibers (CNFs). The CNCs exhibited rigid and rod-like structures due to the removal of amorphous regions through acid hydrolysis, whereas the CNFs retained flexible, fiber-like morphologies and high aspect ratios. Incorporating CNCs or CNFs into NR improved its tensile properties, with the rigid CNCs enhancing the mechanical properties more than the flexible CNFs. CNC addition resulted in a 40% increase in tensile strength and a 38% increase in Young's modulus of NR. However, elongation at break decreased with filler content. On the other hand, CNF addition improved the elongation at the break without compromising the tensile properties. NR with CNF addition exhibited a 25% increase in tensile strength, a 30% increase in Young's modulus, and a 20% increase in elongation at break. Additionally, the biodegradability of NR nanocomposite films containing CNCs or CNFs surpassed that of unfilled NR film. Notably, a 6-month soil burial test revealed weight losses of 35% and 40% for NR nanocomposite films with CNCs and CNFs respectively, compared to a weight loss of 25% for the unfilled NR film.

THE APPLICATION OF RICE STRAW-BASED PLA/NR BIOCOMPOSITE AS GREEN PLANTING BAGS

This study’s primary objective was to observe the growth of marigold seedling in biodegradable planting bags made from polylactic acid (PLA), natural rubber (NR), and rice straw (RS) film, as well as the biodegradation of the bags during planting. The flexible PLA/NR/RS film was produced using a PLA/NR blend ratio of 70:30 percent by weight (wt%) as a matrix and filled with RS at 3, 5, and 10 wt%. All PLA/NR/RS biocomposite films were produced via an extrusion casting method. To examine the growth efficiency of marigold seedlings in biodegradable planting bags, marigold seedlings were transferred into PLA/NR/RS biocomposite bags. After being planted for 90-days, the stalk diameter and dry mass of the marigold seedlings grown in the PLA/NR/RS biocomposite bags tended to increase with increasing RS content. The biodegradability of all PLA/NR/RS biocomposite bags was measured by how much weight each bag lost after marigold seedlings were planted in it. The amount of rice straw in PLA/NR/RS biocomposite bags was found to affect how much weight they lost. Maximum weight loss was observed when the film contained 10 wt% RS fiber, which corresponded to the lowest PLA molecular weight assessed by gel permeation chromatography (GPC).

Porous Deproteinized Natural Rubber Film Loaded with Silver Nanoparticles for Topical Drug Delivery.

The work demonstrated the use of natural rubber for topical drug delivery. The first objective was to fabricate a porous deproteinized natural rubber film loaded with silver nanoparticles. Characterizing and assessing its formulation was the second objective. Surface pH, mechanical properties, swelling ratio, erosion, moisture vapor transmission rate, scanning electron microscopy/energy dispersive X-ray analysis, and X-ray diffraction were evaluated. In vitro studies and antibacterial activity were assessed. It was discovered that silver nanoparticles could enter the film and that their concentrations ranged between 7.25 and 21.03 µg/cm2. The pH of the film's surface was 7.00. The mechanical properties of the film with silver nanoparticle loading differed from the blank film. After adding silver nanoparticles, the film eroded faster than before, but the swelling ratio was not affected significantly. Increased time utilization had an impact on the moisture vapor transmission rate of the film. Silver nanoparticles released easily from the film while there was less permeability. The dead pig-ear skin had significant silver nanoparticle accumulation. Potent antibacterial activity was seen in the film containing silver nanoparticles. The silver nanoparticle-loaded film may be used as a wound dressing for a topical film that promotes wound healing while also protecting the area from infection.

Effect of graphene nanoplatelet-infused natural rubber film composite on morphology, spectral, and electrochemical properties

Effect of graphene nanoplatelet-infused natural rubber film composite on morphology, spectral, and electrochemical properties

Deproteinization of Natural Rubber Latex and Its Pale-Colored Thin Films

The non-rubber components present in natural rubber latex can contribute to the dark color of dried films and may cause allergic reactions. This project aimed to develop light-color rubber films with minimal protein contamination. Various additives were incorporated, and a leaching procedure was implemented to address this issue. The evaluation focused on protein content, color changes, and swelling properties of thin natural rubber films. Texapon N70 proved effective as both a latex stabilizer and leaching agent, while Uniphen P-23 served as a preservative. The combined use of these additives facilitated the removal of soluble serum through appropriate incubation, leaching, and centrifugation processes. The introduction of additional centrifugation cycles improved deproteinization and color reduction; however, it led to a loss of rubber mass and an increase in manufacturing costs. Increasing the amount of Texapon N70 and introducing alkali potassium hydroxide (KOH) further enhanced the efficiency of deproteinization and color reduction. The optimal conditions determined in this investigation were as follows: 0.5% w/w Texapon N70, 0.5% w/w KOH, 1% w/w Uniphen P-23, a 60-min incubation period, and a single leaching cycle with distilled water. These conditions resulted in a 90.57 ± 1.20% decrease in protein contamination and a color change (ΔE) of 433.69 ± 20.23. This successful condition can be replicated and scaled up for further applications.

Transparent flexible fluorescent films based on natural rubber composited with quantum dots for traffic equipment

Quantum dots are one of the nanotechnology materials applied in various ways like flexible electronic devices and others. In this work, we study and synthesize semiconductor quantum dots (SQDs) to produce fluorescent natural rubber films by the technique called directed blending. We illustrate the appropriate ratio of mixtures employed in our method such as quantum dot colloidal solutions and natural latex as well as moles between each substance. During the process, the liquid composite and rubber adhesive is applied to the surface for creating flexible fluorescent films that can be dried at room temperature. In addition, these flexible fluorescent films can be covered with diverse curved surfaces applied probably as a traffic device like luminous traffic cones or traffic signs that glow at night. Based on the unique properties of our products, our research provides an application developed from quantum dot nanotechnology.

CuO/Ag hybrid nanomaterial coated hydrophilic natural rubber film with minimal bacterial adhesion and contact killing efficiency

The formation of biofilms and bacterial infections associated with biomedical equipment continues to be a severe clinical problem. To provide a high-efficiency bactericidal coating, CuO/Ag hybrid nanomaterial was introduced onto the surface of natural rubber polymer by a simple immersion strategy. The hybrid nanomaterial was synthesised using Carboxymethyl chitosan as the stabilising agent. The effective conjugation of CuO/Ag on rubber film was assured by inductively coupled plasma mass spectrometry (ICP-MS) and hydrophilicity of the coated and uncoated rubber films were tested by water contact angle measurements. The antimicrobial drop test results authenticate the eradication of the attached bacterial strains. The live/dead bacterial assay further confirmed the destruction of 83% of E. coli and 92% of S. aureus on the rubber film with minimal bacterial adhesion. In fact, clinical infections caused by biofilms are more challenging in the healthcare sector rather than those caused by planktonic cells. The colorimetric (crystal violet) assay depicts that there is biofilm reduction of 53.82% E. coli, 54.87% S. aureus and 49.71% P. aeruginosa on rubber film by modification with CuO/Ag. The results of qualitative and quantitative antibacterial assessments show good bacterial resistance for the coated rubber film. The modified hydrophilic surface can be selectively used in rubber-based medical devices, especially to avoid nosocomial infections.

A novel preparation of natural rubber films with a conducting nanocarbon network for antistatic applications

A novel preparation of natural rubber films with a conducting nanocarbon network for antistatic applications