Diene Rubber Research Articles

High temperature vulcanized ethylene propylene diene rubber nanocomposites as high voltage insulators: Dielectric breakdown measurements and evaluation

The use of porcelain and thermoplastic based materials as High voltage insulators has always been dominant in the industry. Several elastomers were also investigated, mainly Ethylene Propylene Rubber and Silicone rubbers were used as replacement of the traditional Porcelain high Voltage insulators. In this study we experiment with new elastomer, Ethylene propylene diene rubber (EPDM), that is capable of withstanding high voltage as well as being resistant to severe weathering conditions. In addition to having excellent mechanical properties that we discussed elsewhere. Detailed dielectric breakdown measurements were carried out for room temperature vulcanized and high temperature vulcanized samples. The effects of exposure to UV radiation on the dielectric breakdown strength was also studied. Different fillers were used to improve the dielectric breakdown strength of different polymer matrices. Both carbon black based fillers and inorganic fillers were experimented in order to reach optimum mix properties that provide the best dielectric breakdown strength. Resistance to thermal aging and UV radiation was also carried out on EPDM samples.

Mechanical properties of rubber vulcanizates containing Ethylene Propylene Diene Rubber waste at different types of vulcanization system

Ethylene Propylene Diene Rubber (EPDM) waste filled Natural Rubber (NR) that cured by using conventional vulcanization (CV), semi-efficient vulcanization (semi-EV) and efficient vulcanization (EV) system was successfully compounded by an internal mixer. The ratio of sulphur and accelerator is different for each vulcanization system, that finally affect the vulcanizate properties due to the different structural features of an accelerated sulphur vulcanizate of NR. 60 phr of pulverized EPDM waste was incorporated into 40 phr of NR in each vulcanization system. Studies about the usage of abundantly available EPDM waste as a potential filler is essential towards green environment and minimize landfill area in future. It is found that the cured rubber with CV system has the best properties due to high degree of crosslinking of polysulphidic crosslink. Tensile properties and abrasion resistance of the rubber compound indicated its mechanical properties were investigated. Density and hardness test were also done to study its physical properties. For tensile strength, CV system has 14% increment from EV system because of a stress-relieving mechanism that exhibited in this vulcanization system. As for tensile modulus, M500 for CV system shown 29% increment than EV system. As a result of the decreased chain flexibility caused by the increased crosslinking density in the CV system, the elongation at break of the vulcanizate is the lowest (174 mm) when compared to the EV system (336 mm). CV system shown highest Abrasion resistance index (ARI) i.e. 1820%. This indicate that very small amount of mass loss obtained for the CV cured rubber during the testing. CV system gives highest density and hardness values i.e. 1.0747 g/cm3 and 52.5 Shore A, respectively. Thus, the results indicated that NR containing EPDM waste cured by CV system is able to be utilized in the development of rubber compound with a compromise property.

Enzymatic and Chemical Approaches for Post‐Polymerization Modifications of Diene Rubbers: Current state and Perspectives

Front Cover: Diene rubbers are elastomeric polymers which possesses double bonds in the molecular backbone. Among the post-polymerization modifications, enzymatic biodegradation and click-chemistry functionalization represent important tools in the development of new materials and were summarized in this review. This is reported by Franciela Arenhart Soares and Alexander Steinbüchel in article number 2100261.

Polybutadiene Vitrimers with Tunable Epoxy Ratios: Preparation and Properties.

Traditional crosslinked diene rubber has excellent thermal–mechanical properties and solvent resistance, yet it is incapable of being recycled via universal molding or injecting. Vitrimers, a new class of covalently crosslinked polymer networks, can be topologically rearranged with the associative exchange mechanism, endowing them with thermoplasticity. Introducing the concept of vitrimers into crosslinked networks for the recycling of rubbers is currently an attractive research topic. However, designing tailored rubber vitrimers still remains a challenge. Herein, polybutadiene (PB) vitrimers with different structures were prepared via partial epoxidation of double bonds and ring-opening esterification reactions. Their mechanical and relaxation properties were investigated. It was found that the increasing crosslinking density can increase tensile strength and activation energy for altering the network topology. The influence of side-group effects on their relaxation properties shows that an increase in the number of epoxy groups on the polybutadiene chain can increase the chance of an effective exchange of disulfide units. This work provides a simple network design which can tune vitrimer properties via altering the crosslinking density and side-group effects.

Poultry Feather Waste as Bio-Based Cross-Linking Additive for Ethylene Propylene Diene Rubber.

Most rubbers used today rely on sulphur as a cross-linking agent and carbon black from fossil resources to modify the mechanical properties. A very promising substitute can be found in natural keratins such as feathers. These are not only tough, but also contain a relevant amount of sulphur in the form of disulphide bridges. The present study shows that these can be activated under vulcanisation conditions and then bind covalently to EPDM rubber to form a cross-linked network. Feathers were cut into lengths of 0.08, 0.2, and 1 mm and incorporated at 38, 69, or 100 phr into EPDM mixtures containing either no carbon black or no carbon black nor sulphur. The presence of feather cuttings increases the tensile and compressive strength as well as the hardness, and reduces the rebound resilience. Due to their high (approximately 17%) nitrogen content, the feathers also improve the thermal stability of the composite, as the main degradation step is shifted from 400 °C to 470 °C and the decomposition is significantly slowed down. Since elastomers are a large market and feathers in particular are a high-volume waste, the combination of these two offers enormous ecological and economic prospects.

Occurrence and concentration of 20–100 μm sized microplastic in highway runoff and its removal in a gross pollutant trap – Bioretention and sand filter stormwater treatment train

Microplastic pollution of stormwater can be a serious threat to the environment. Gross pollutant trap (GPT) - bioretention treatment trains have been shown previously to treat (inter alia) particulate stormwater pollutants including microplastic particles larger than 100 μm. This study was carried out to investigate whether such stormwater treatment trains also remove smaller 20 to 100 μm sized microplastic particles from highway runoff. Further, it investigates occurrence and concentration of 20 to 100 μm sized microplastic particles in highway runoff and which polymer types they can be assigned to. Volume proportional samples from nine rain events were taken from the incoming highway stormwater, from the gross pollutant trap effluent and the outflow from a bioretention system as well as a non-vegetated sand filter. The microplastic analyses were carried out using μFTIR and FTIR-ATR, which made it possible to detect particles where carbon black was present. It was found that 20 to 100 μm sized microplastic particles are abundant in highway runoff and that their concentrations are highly variable, with a median of 230 particles/L, a minimum of 42 particles/L and a maximum of 8577 particles/L. The dominant polymer types in highway stormwater were Polypropylene (PP), Ethylene Propylene Diene (EPDM) rubber and Ethylene-vinyl acetate (EVA). The treatment train with the bioretention system treated 20 to 200 μm sized microplastic particles significantly better than the treatment train with a non-vegetated sand filter, with median effluent concentrations of 26.5 particles/L and 121 particles/L, respectively. The GPT had no significant impact on the treatment of 20 to 100 μm sized microplastic particles.

Catalyst-free curing and closed-loop recycling of carboxylated functionalized rubber by a green crosslinking strategy

Current adopted rubber curing methods undergo large amounts of environmental issues, such as the release of toxic volatile organic compounds (VOCs) during curing process and difficulties in recycling of end-of-life rubbers. Many new curing reactions and cross-linking structures have been developed to solve these problems. A green curing strategy based on epoxy-acid reactions and ester linkages could be a potential alternative to the current curing ones. However, the curing reactions between epoxy and carboxyl groups generally require a catalysis to improve curing rate, and the recycling process requires toxic organic solution or high temperature. It is of great desired to develop a real environmentally friendly crosslinking strategy for rubber materials. In this paper, we report a facile and high-efficiency green crosslinking strategy for the carboxyl-functionalized rubber. N,N,N′,N'-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) was selected as a multifunctional amine-type high-efficiency crosslinker for carboxylated nitrile rubber (XNBR). TGDDM-cured XNBR exhibit extremely fast crosslinking rate and high crosslinking efficiency due to the four epoxy terminated units and tertiary amine structure acting as an internal catalyst. Besides, the mechanical properties and crosslinking density of TGDDM-cured XNBR can be regulated by TGDDM content. Furthermore, the ester linkage formed by curing reaction could be selectively and efficiently cleaved in a mixed solution of ethanol and water under mild condition. The closed-loop recovered XNBR maintains chemical structure and molecular weight and exhibit good mechanical performance. This strategy offers a promising way for high-efficient crosslinking of diene rubber as well as a real cost-effective and environmentally friendly recovery of end-of-life rubber materials.

Enzymatic and Chemical Approaches for Post-Polymerization Modifications of Diene Rubbers: Current state and Perspectives.

Diene rubbers are polymeric materials which present elastic properties and have double bonds in the macromolecular backbone after the polymerization process. Post-polymerization modifications of rubbers can be conducted by enzymatic or chemical methods. Enzymes are environmentally friendly catalysts and with the increasing demand for rubber waste management, biodegradation and biomodifications have become hot topics of research. Some rubbers are renewable materials and are a source of organic molecules, and biodegradation can be conducted to obtain either oligomers or monomers. On the other hand, chemical modifications of rubbers by click-chemistry are important strategies for the creation and combination of new materials. In a way to expand the scope of uses to other non-traditional applications, several and effective modifications can be conducted with diene rubbers. Two groups of efficient tools, enzymatic, and chemical modifications in diene rubbers, are summarized in this review. By analyzing stereochemical and reactivity aspects, the authors also point to some applications perspectives for biodegradation products and to rational modifications of diene rubbers by combining both methodologies.

Synthesis of bromine‐functionalized polyolefins by scandium‐catalyzed copolymerization of 10‐bromo‐1‐decene with ethylene, propylene, and dienes

By use of a THF‐containing trimethylsilylmethyl scandium catalyst system (C5Me4SiMe3)Sc(CH2SiMe3)2(THF)/[Ph3C][B(C6F5)4], the multi‐component copolymerization of 10‐bromo‐1‐decene (BrDC) with ethylene, propylene, and dienes has been achieved to afford a new family of bromine‐functionalized polyolefins with controllable composition and high molecular weight. The copolymerization of BrDC with ethylene afforded the well‐defined BrDC–ethylene copolymers with high BrDC incorporation (up to 12 mol%) and high molecular weight (Mw > 100 kg mol−1). The terpolymerization of propylene, ethylene with BrDC afforded random ethylene–propylene–BrDC terpolymers with controllable bromine content (2 ~ 11 mol%), high molecular weight (Mw > 100 kg mol−1) and low glass transition temperature (Tg = −51 °C ~ −67 °C). Moreover, the tetrapolymerization of ethylene, propylene, BrDC, and ethylidene norbornene or conjugated dienes such as isoprene and myrcene has been achieved for the first time to afford selectively the bromine‐functionalized ethylene–propylene–diene rubbers containing various types of double bonds.

Hydrostatic compression tests, capillary rheometry tests, and extrusion tests performed on unvulcanized rubber confirm importance of compressibility for die swell — Arguments from dimensional analysis

This paper aims at elucidating which factors are effective in terms of influencing the die swell of unvulcanized rubber upon extrusion. To that end, compression, viscosity, and extrusion tests were performed on two types of ethylene–propylene–diene rubbers, while additional compression tests were performed on natural rubber. First, all three testing modalities were assessed separately, revealing that for the tested materials the compressibility is pressure-dependent; the viscosity is velocity-dependent; and the die swell is influenced by several, partly intertwined factors. In order to better understand the collected experimental data, we have employed the theoretical tool of dimensional analysis, showing that the compressibility of unvulcanized rubber is of great importance for the die swell. Surprisingly, the temperature dependence of the die swell turns out to be much less prominent than standardly assumed. Further key factors influencing the die swell concern the geometries of the die and of the canal.

Recyclable crosslinked elastomer based on dynamic dithioacetals

Recent progress in introducing elegant dynamic covalent bonds into covalently crosslinked networks enabled the trade-offs between chemical crosslinking and recycling. Thus far, continuous efforts are made to exploit new dynamic chemistries to address the constrains of intricate preparation procedures and need of catalyst additives in creating dynamic covalent networks. In this work, we report an industrially feasible process to prepare catalyst-free malleable elastomers by engineering dithioacetals as the dynamic motifs into a commercial diene rubber. Specifically, a dithioacetal-containing diacid (BTA) is synthesized and used as a novel crosslinker for epoxidized natural rubber (ENR), by which dynamic dithioacetals are introduced into the elastomeric networks. Small molecule model study shows that dithioacetal exchange can be conducted at elevated temperature without catalyst. In the BTA crosslinked ENR, the thermoactivated dithioacetal exchange reactions can alter its network topologies in an associative pathway and confer it with remarkable reprocessability. The mechanical properties and relaxation rate of the networks can be readily manipulated by varying the dithioacetal concentration.

Investigation of the structure, magnetic, rheological and mechanical properties of EPDM rubber/Cu-Al-Zn alloy composites

The current research presentsthe development of EPDM rubber including shape memory alloy. The Cu-Al-Zn alloy was modified with the coupling agent3-(Trimethoxysilyl) propyl methacrylate (TMSPM)and then incorporated into Ethylene propylene diene rubber (EPDM) by a 2-roll mill technique.The Cu-alloy behaved as superelasticity capability which can be used in various engineering approaches to smart materials. Microstructure, mechanical, rheological and magnetic properties of Cu-Al-Zn/EPDM composites was studied. The rheometericresults indicated that the incorporation of Cu-Al-Zn as a fillerenhance the curing process. Howeverthecuring time ofCu-Al-Zn/EPDMcomposites was reduced compared to the control sample without Cu-alloy. For the mechanical properties, increasing Cu-alloy loading inthe EPDMcomposites resulted inan increment of elongation at break.The addition of Cu based alloy as fillers improved the magnetization of composites with coupling agent when compared toEPDM rubber and Cu-Al-Zn/EPDMcomposites without coupling agent.

Generic Method to Create Segregated Structures toward Robust, Flexible, Highly Conductive Elastomer Composites.

Electrically and thermally conductive polymer composites are extensively used in our daily life. It is of great significance to fulfill the conductivity requirement while maintaining desirable mechanical performance. An efficient solution to achieve this goal is to construct segregated structures in polymer composites by confining fillers into the interstitial areas among polymer domains. Thus far, it still remains a challenge to create segregated structures in cross-linked polymeric networks. Herein, we report a facile methodology to construct segregated structures in sulfur-cured rubbers using an industrially accessible process toward robust, flexible, highly conductive elastomer composites. Specifically, natural rubber granules (NR-RGs) with reactive di- and polysulfides on the surface are fabricated and then mixed with NR gum, carbon nanotubes (CNTs), and curing additives, followed by compression molding to yield two-phase separate composites. In the composites, CNTs are selectively dispersed in the continuous NR phase due to the volume exclusion effect caused by the separate NR-RG phase, leading to overwhelming electrical conductivity compared to the counterparts with randomly dispersed CNTs. In addition, NR-RGs can serve as novel reinforcement for NR, imparting the composites with remarkably improved modulus and retained stretchability. The simultaneously improved electrical conductivity and mechanical properties are due to the strong interfacial adhesion between the NR matrix and NR-RGs, as the di- and polysulfides on the surface of NR-RGs can participate in the cross-linking reactions of NR gum and enable the establishment of covalent bonding across the interfaces. The universality of this approach in preparing segregated composites with a combination of high conductivities and robust mechanical properties is demonstrated using other diene rubbers as the matrix and boron nitride as the filler.

Effect of reactionary capable siloxane compatibilizer on the properties of blends of ethylene propylene diene and siloxane rubbers

Effect of reactionary capable siloxane compatibilizer on the properties of blends of ethylene propylene diene and siloxane rubbers

Curing of an Epoxy Composition in the Presence of Functionalized Diene Rubber

Curing of an Epoxy Composition in the Presence of Functionalized Diene Rubber

The effect of UV radiation ageing on the structure, mechanical and gas permeability performances of ethylene–propylene–diene rubber

This work focused on the influence of UV radiation on the structures and performances of ethylene-propylene-diene rubber (EPDM). The exposure of EPDM to UV radiation was performed for various times (0, 7, 14, 21 and 28 days). The surface chemical structure and free volume of EPDM before and after UV ageing were determined by infrared spectroscopy (IR) and positron annihilation lifetime spectroscopy (PALS), respectively. The surface morphology, crosslink density, mechanical and gas permeability properties of EPDM were also analyzed. Under UV radiation, oxidation reactions occur on the EPDM surface and oxygenated species are formed. With prolonging ageing time, the oxidative degree increases, leading to more and denser microcracks on the surface. The plausible ageing mechanism of EPDM is suggested. At the initial 14 days of UV irradiation, the crosslink density of EPDM reduces due to the chain scission reaction, causing the increase of free volumes and thereby the enhancements of gases permeabilities. When the ageing time is longer than 14 days, crosslinking dominates and the free volumes decrease, bringing about the reductions of gases permeabilities. With prolonging ageing time, the tensile strength, glass transition temperature (Tg) and storage modulus of EPDM initially decrease and then enhance, in agreement with the change trends of crosslinking density.

Development of Novel Magnetic Responsive Intelligent Fluid, Hybrid Fluid (HF), for Production of Soft and Tactile Rubber

For the purpose of the replacement of Magnetic Fluid (MF) which is effective in the production of an artificial soft and tactile skin for the robot, etc. by utilizing a rubber solidification method with electrolytic polymerization, we proposed a novel magnetic responsive intelligent fluid, Hybrid Fluid (HF). HF is structured with water, kerosene, silicon oil having Polydimethylsiloxane (PDMS) and Polyvinyl Alcohol (PVA) as well as magnetic particles and surfactant. The state of HF changes as jelly or fluid by their rates of the constituents and motion style. In the present paper, we presented the characteristics of HF: the viscosity and the magnetization are respectively equivalent to those of other magnetic responsive fluids, MF and their solvents. For the structure, HF is soluble simultaneously with both diene and non-diene rubbers. The diene rubber such as Natural Rubber (NR) or Chloroprene (CR) has a role in the feasibility of electrolytic polymerization and the non-diene rubber such as silicon oil rubber (Q) has a role in defense against deterioration. Therefore, the electrolytically polymerized HF rubber by mixing NR, CR as well as Q is effective for the artificial soft and tactile skin. It is responsive to pressure and has optimal property on piezoelectricity in the case of the mixture of Ni particles as filler. HF is effective in the production of the artificial soft and tactile skin made of rubber.

КОНФИГУРАЦИОННО-ИЗОМЕРНЫЙ СОСТАВ КАУЧУКОВ: ОПРЕДЕЛЕНИЕ МЕТОДОМ СПЕКТРОСКОПИИ ЯМР 1H И 13C

Nuclear magnetic resonance (NMR) spectroscopy is a convenient method for studying the structure and isomeric composition of diene rubbers. A simple and reproducible method is proposed for determining the content of both rubber and impurity compounds, which does not require additional sample preparation. Formulas for calculating the composition of industrial products and determining the initial substances are given, the applicability of the analysis method is confirmed. In the process of work, rubbers of various brands were analyzed, their configuration-isomeric composition was established. It was found that the integration ranges given in the literature earlier and the methods for processing 1H NMR spectra differ, the signals of the groups often overlap in the spectrum, which increases the calculation error. It is shown that the structure of the industrial products under study is established most accurately by carbon proton resonance spectroscopy, and the calculation based on the PMR spectra allows confirming the data obtained with sufficient accuracy.

Preservation of geochemical markers during co-combustion of hard coal and various domestic waste materials

Combustion of domestic waste for heating purposes in non-adapted furnaces is a common environmental problem all over the world since it leads to significant emission of harmful substances to the atmosphere. In this project fly and bottom ash from hard coal and domestic waste co-combustion were investigated on the occurrence and distribution of geochemical markers, polycyclic aromatic hydrocarbons (PAHs), and their alkyl derivatives. Hard coal with a domestic waste admixture (paper, ethylene propylene diene rubber, tire rubber, polyethylene, polyvinyl chloride) was combusted in a certified domestic central heating furnace equipped with a control and measurement system. Fly ash was collected on glass microfiber filters inside the flue gas chimney. Raw fuels, fly and bottom ash extracts were analyzed with gas chromatography–mass spectrometry (GC–MS). Geochemical markers survived the coal/domestic waste combustion and can be identified despite the presence of other organic compounds derived from domestic waste thermal decay. The highest changes in distribution and values of geochemical ratios concern light-weight compounds, i.e. lighter n-alkanes and acyclic isoprenoids (pristane and phytane), with distinct differences between fly and bottom ash. n-Alkanes expulsion significantly decreased values of Pr/n-C17 and Ph/n-C18 ratios. Due to their high molecular weight pentacyclic triterpanes mostly retained their original distributions; however, some shifts in values of their thermal maturity ratios occurred due to artificial maturation of organic matter under the heat of combustion. PAHs diagnostic ratios showed variable utility in the indication of domestic waste admixture to hard coal combusted. The highest sensitivity was found for BaP/BghiP, MPI-1, and MPI-3 whereas Fl/(Fl + Py) rather pointed out at hard coal dominating in the fuel mixture. The addition of EPDM and tires significantly worsened the quality of combustion, which is reflected in high extract yields and the retained hard coal geochemical features such as the Pr/Ph value closest to the raw coal value.

Ablation and thermal properties of ethylene propylene diene rubber/carbon fiber composites cured by ionizing radiation for heat shielding applications

In this study, new composites were prepared from ethylene propylene diene rubber (EPDM) that loaded with various concentrations of short carbon fibers (SCFs) ranged from 5 up to 20 part per hundred part of rubber (phr). Aluminum trihydroxide (ATH) was added by two concentrations, namely 10 and 30 phr to EPDM/SCFs composites to enhance its heat shielding. Foaming agent, azodicarbonamide (ADC) was added to increase ablation resistance. Composites were prepared on open rubber roll mills, and then the rubber composites were gamma ray irradiated at different doses of 25, 50, 75, 100 and 150 kGy. Fiber incorporation into rubber matrix has been proven as a key factor in enhancing tensile strength and flame retardant properties of fabricated composites. The prepared composites were characterized by using various analytical methods counting physico-mechanical properties, thermal gravimetric analysis (TGA), Ablation test (oxy acetylene test) and propagation flame test. The utmost mechanical performance was reported for the incorporated 5 phr of carbon fiber into EPDM at 100 kGy. Also, the flame retardancy and ablation properties for composites were enhanced by increasing addition of carbon fibers and ATH in presence of ADC.