Sulfur Vulcanization System Research Articles

Influences of the grafting percentage of natural rubber‐graft‐poly(2‐hydroxyethyl acrylate) on properties of its vulcanizates

AbstractThe graft copolymerization of 2‐hydroxyethyl acrylate (HEA) monomer onto natural rubber (NR) latex was successful using cumene hydroperoxide and tetraethylene pentamine as redox initiators. The grafting of poly(2‐hydroxyethyl acrylate) (PHEA) on the NR particles was confirmed by Fourier transform infrared spectroscopy, 1H NMR spectroscopy and TEM. The NR‐g‐PHEA with various grafting percentages (0%, 8.7%, 14.3% and 18.7%) was compounded on a two‐roll mill with a sulfur vulcanization system. The effects of grafting percentage on the cure characteristics, dielectric properties, thermal properties and physical properties of NR‐g‐PHEA vulcanizates were investigated. It was found that increased grafting caused NR‐g‐PHEA vulcanizates to have reduced water contact angle, scorch time and cure time, while the dielectric constant and dissipation factor increased. The NR‐g‐PHEA vulcanizate with 8.7% grafting exhibited the highest delta torque (MH − ML), crosslink density, tensile strength, moduli at 100%, 200% and 300% strains, and hardness, with insignificant loss of elongation at break in comparison to the other cases. © 2018 Society of Chemical Industry

Determination of vulcanization rate constant, crosslink density, and free sulfur content on carbon black flled EPDM

Different ethylene propylene diene monomer (EPDM) composite with the carbon black (CB) variation of 50, 60, and 70 phr (per hundred rubbers) is compounded by using an efcient (EV), semi-efcient (SEV), and conventional (CV) sulfur vulcanization systems. This research aims to investigate the effect of vulcanization systems and carbon black content on the vulcanization rate constant, the crosslink density, and the free sulfur content. This research shows the EV system resulting in the fastest vulcanization rate constant (0.0191/second), the lowest overall crosslink density (0.0022 mol.cm -3 ), and the highest percentage of free sulfur content in the EPDM vulcanization (0.40 %). The CV system provides the slowest vulcanization rate constant (0.0061/second) and the highest overall crosslink density (0.0034 mol/cm -3 ). The percentage of free sulfur content in the EPDM vulcanization of CV system is between EV and SEV systems. The SEV system provides the vulcanization with the characteristic of vulcanization rate constant and overall crosslink density between EV and CV systems as well as provides the lowest percentage of free sulfur content (0.29 %). The higher carbon black loading in each vulcanization systems means the lower rate constant of vulcanization and the higher overall crosslink density.

FROST-RESISTANT RUBBER ON BASE OF COMBINATION OF BUTADIENE-NITRILE AND HYDRIN RUBBERS

The influence of hydrin rubbers on the plastic-elastic, rheometric, physical-mechanical properties and frost resistance of oil-and-petrol resistant rubber mixture of B-14 type was studied. The study was carried out with the purpose of selecting the composition of the rubber mixture, which is resistant to low temperatures and has increased operational properties. The composition of the test rubber mixture with a sulfur vulcanization system consisted of butadiene-nitrile rubber BNKS-18AMN (copolymer of butadiene and acrylonitrile) and hydrin rubbers T-3000 and T-6000 (copolymers of epichlorohydrin, ethylene oxide, propylene oxide and allyl glycidyl ether), diphenylguanidine, zinc oxide, Agidol-2, technical carbon P 803, dibutyl sebacate and other ingredients. Rubber mixture was prepared by mixing caoutchoucs with ingredients on lab rolls LB 320 150/150. For the rubber mixture variants, the elastomeric properties on the viscosimeter MV 3000 and the vulcanization characteristics on the rheometer MDR 3000 of firm «Mon Tech» were investigated. The rubber mixture was vulcanized in a two-storey hydraulic electrically heated press VP-400-2E at a temperature of 150 °C for 40 min. Studies of the elastic-strength properties of rubber were carried out in accordance with the standards existing for the rubber industry. The frost resistance of rubber was investigated by determining the temperature limit of brittleness and by of method differential scanning calorimetry. The study of thermo-aggression resistance of vulcanizates was carried out by determining the change in their elastic-strength properties after prolonged thermal exposure to air and standard liquid SZHR-1, as well as changes in volume and mass after aging in technical oil AMG-10. As a result of the research it was established that the rubber mixture based on the combination of BNKS-18AMN and T-6000 rubbers can be used for the manufacture of frost-resistant rubber products and sealing elements for oil and gas industries that can work at elevated temperatures with improved elastic-strength and operational properties.Forcitation:Ushmarin N.F., Egorov E.N., Koltsov N.I. Frost-resistant rubber on base of combination of butadiene-nitrile and hydrin rubbers. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 8. P. 60-64.

Thermal analysis of the sulfur vulcanization

It is known that rubber mixes containing vegetable oils and vulcanized vegetable oils give better flow properties, plasticizing action, low temperature flexibility and ozone resistance. Now, in this investigation, the aim was to provide additional information about the effect of two vegetable oils (linseed oil and peanut oil) upon accelerated sulfur vulcanization system using thermal analysis—differential scanning calorimetry (DSC) and thermogravimetry. Several combinations of curatives (ZnO, sulfur and 2-t-butylbenzothiazole sulfenamide or TBBS) with stearic acid or vegetable oils were investigated, and DSC curves showed that vulcanization systems where linseed oil or peanut oil replaced stearic acid as activator proceeded an outline of basic steps similar to conventional mixture. However, the formation of the complex between Zn2+, sulfur and products of TBBS decomposition, main step in the vulcanization reaction, required much more energy. Exothermic ΔH values of 45.4 and 20.3 J g−1 were found for ZnO/S/TBBS/linseed oil and ZnO/S/TBBS/peanut oil, respectively, against only 5.8 J g−1 in the case of ZnO/S/TBBS/stearic acid mixture.

Physical and Mechanical Properties of ENR Compatibilized NR/NBR Blends Reinforced Nanoclay and Nanosilica

SummaryProperties of the unfilled rubber blends (Natural rubber, NR and Nitrile Butadiene Rubber, NBR) were poor due to the absence of reinforcing agent. However, the strength of compound had been improved with the addition of nanofiller. There were two (2) types of nanofillers that had been introduced which are nanoclay (NC) and nanosilica (NS). NR/NBR composites were prepared by open milling process where different amount of nanofiller was added ranging from 1 until 7 phr. There are a few possibilities might occur when using small particles size of fillers especially in term of interaction between rubber‐filler and filler‐filler interaction. Apart from that, different polarity and composition of both rubbers were influenced the interaction between filler and rubber phases. The interaction between non‐polar and polar rubber was enhanced using epoxidized natural rubber (ENR). The rubber compound was cured via a conventional sulphur vulcanization system. The cure characteristic result shows that the incorporation of nanofiller does not affect much on the t90. The physical and mechanical properties of epoxidized natural rubber (ENR) compatibilized NSi‐NR/NBR blends were determined by conducting the density measurements, hardness and tensile tests. The NC filler gave the highest tensile strength compared to NS. On top of that, reduction trend on the tensile strength observed at 3 phr of NS loading due to the formation of NS aggregates. The values of moduli, hardness and densities of vulcanizates increased as the nanofiller loading increased. It occurs due to better filler dispersion in the rubber matrix and strong interaction between filler‐rubber phases. The result shows that NC has more pronounce effect on the physical and mechanical proportion of the rubber vulcanizates.

Reusable Modified Natural Rubber Foam for Petroleum‐Based Liquid Removal

SummaryA new kind of natural rubber‐based oil sorbent material was prepared by sulfur vulcanization system. Natural rubber (NR) foam was modified with poly(butyl methacrylate) (PBMA) and poly(butyl acrylate) (PBA) which were prepared by emulsion polymerization. The functionality of pure polyacrylate and modified NR foam were characterized by Fourier transform infrared (FTIR) spectroscopy. Morphology of the modified NR foam was observed by scanning electron microscope (SEM). The oil/water sorption capacity and reusability of modified NR foam were investigated. Sorption test of modified NR foam showed that the modified NR foam were efficiently removed petroleum‐based liquid (viscosities of 0.49–37 cSt) such as gasohol, diesel, engine oil, xylene and toluene. The oil sorption capacity of modified NR foam was in the range of 5–16 g g−1 and maintained oil sorption capacity over the range of 3–15 g g−1 after 20 cycles of absorption. About 95% of foam can be recovered by squeezing or evaporating the oil or organic solvent within the modified NR foam. The results showed that the modified NR foams are promised as reusable oil sorbent.

Vulcanization kinetics of nano-silica filled styrene butadiene rubber

It was shown that the physical filler-polymer and filler–filler interactions, apart from the filler surface chemistry, has a substantial role in controlling the vulcanization kinetics of styrene butadiene rubber filled with nano-silica in a sulfur vulcanization system. Kinetic studies by the oscillating disc rheometer, differential scanning calorimeter, and swelling tests revealed that the vulcanization rate goes through a maximum as loading of silica increases, but conversion in crosslinking continuously decreases as the amount of silica increases. The effect of silica loadings on the vulcanization reactions was linked to the immobilization of rubber chains around particles as well as in a polymer-mediated filler network, which were differentiated by the nonlinear viscoelastic behavior of rubber vulcanizates. By surface modification of nano-silica, the accelerating/decelerating effects of nano-silica on the vulcanization reactions were altered corresponding to the non-linear viscoelastic behavior of the vulcanizates. Therefore, a mechanism was proposed which correlates vulcanization kinetics of rubber to the dynamics of chains influenced by the reinforcing fillers.

Antagonism of Natural Anti- and Pro-Oxidants in Synthetic Polyisoprene Rubber Vulcanizates

This research was to elucidate the antagonism of natural anti-and pro-oxidants in synthetic polyisoprene rubber (IR) grade 2200 as a model system. Alanine and linoleic acid was chosen as natural anti-and pro-oxidants, respectively. These two amino acids were directly added into the rubber by mixing in two-roll mill. Peroxide vulcanization and three types of the sulfur curing system, i.e., conventional vulcanization (C.V.), efficient vulcanization (E.V.) and semi-E.V. have been studied. Cure properties of the rubber compounds were characterized with moving die rheometer (MDR) at 150 and 170°C for sulfur and peroxide vulcanizing systems, respectively. The compounded rubbers were divided into two parts. The former was pressed on a hydraulic hot press machine and cut to a dumbbell specimen according to ASTM D412 type C. Then, the rubber specimens were subjecting to accelerate the thermal oxidative degradation at 100°C under air-circulating oven with various times. The deterioration of the aged rubber specimens was determined by tensile test. The latter was shaped and characterized by ozone resistance in accordance with ISO 1431/1. For tensile test, the results showed that only the C.V. system of the sulfur cure, the tensile stress at 200% strain of IR comprised alanine and linoleic acid with the ratio of 1:1 was higher predominantly than that of the cured IR control. In addition, the peroxide cured IR mixed with alanine and linoleic acid cannot be passed the heat aging for 96 h. For the ozone resistance, the results exhibited that all specimens appeared uncountable number of crack but only the IR cured by peroxide presented the length of crack less than 1 mm (C-3). It might be concluded from the experiment that anti-oxidative activity of the alanine plays a vital role in the rubber vulcanizate only for C.V. system. However, the existing of both alanine and linoleic acid in the sulfur cured IR was not outstandingly changed for the ozone resistance but not that for the peroxide cured IR.

Properties of Thermoplastic Natural Rubber (TPNR): Influence of Polypropylene Grades on TPNR Properties

Thermoplastic vulcanizate (TPV) based on natural rubber (NR) and polypropylene (PP) blends were successfully prepared through a dynamic vulcanization process using Brabender Plastograph EC Plus with a rotor speed of 60 rpm at 180°C. Sulfur vulcanization system was used to cure rubber phase in the TPVs. Three grades of PP (i.e., PP700J, HP553R and HP544T) were used to blend with NR at a fixed blend ratio of NR/PP = 60/40. The mechanical properties, crosslink density, complex viscosity and morphological properties of the blends were examined. The results revealed that the dynamically cured NR/PP700J samples showed the best mechanical properties because of higher crosslink density and smaller rubber particle size when compared with those of the blends combined with HP553R and HP544T. Furthermore, the complex viscosity of the TPVs was highest for the blends with PP700J.

Comparison of Thermal Stability of Sulfur, Peroxide and EB Irradiation Cured NR Compounds Containing Ground EPDM Waste

This article described concerning to the effect of sulfur, peroxide and electron beam irradiation cured on the thermal stability of natural rubber compounds containing ground EPDM waste. Semi-efficient vulcanization (semi-EV), dicumyl peroxide (DCP) and the EB irradiation at 200 kGy were used and applied in the compounds. Thermal analysis namely thermogravimettric analysis (TGA) and its kinetics of degradation process were investigated. Results indicated that the EB irradiation revealed superior thermal stability by shifting the decomposition temperature at various weight loss and maximum derivatives followed by peroxide and sulfur vulcanizing systems. The activation energies of degradation of the vulcanizates were determined by applying the Coats-Redferns method. It can be verified that the activation energies observed in the vulcanizates were in good agreement with the thermogram results. The highest thermal stability obtained from EB irradiation might be due irradiation-induced-crosslinking resulting to more thermal energy is supplied to overcome the apparent activation energy of the vulcanizates.

Comparison of Mechanical Properties and Curing Characteristics of Natural Rubber Composites with Different Coupling Agents

Nanosilica (NS) was recently used as a filler to improve mechanical properties, morphology behaviors of natural rubber (NR) composites and also for light colored product. NS is hard to disperse in NR composite compare to carbon black due to large number of Silanol (Si-OH) group leads to strong filler-filler interaction. Silane coupling agent was extensively used to improve reinforce efficiency of NS and also for good filler-matrix interaction by reducing Si-OH group. In this study, Bis[3-(triethoxysilyl)propyl] tetrasulfide (Si-69) and (3-aminopropy)triethoxysilane (APTES) were used as a coupling agents with various loading 1.5, 3, 4.5 phr in conventional sulphur vulcanization system. Both Si69 and APTES gave a significance of the NR compound processing. However, hardness was gradually decreased up to 4.5 phr due to plasticizing effect. Si-69 can increase crosslink density because of 4 molecular of sulphur (S) and its structure retarded the curing where APTES accelerated the cured because APTES has lower molecular weight and viscosity than Si-69.

Properties of natural rubber/recycled ethylene–propylene–diene rubber blends prepared using various vulcanizing systems

The role of various vulcanizing systems on the curing characteristics, mechanical properties, morphology and dynamic mechanical analysis of natural rubber and recycled ethylene–propylene–diene rubber blends was investigated. Accelerated sulfur-vulcanizing systems (semi-EV and EV), peroxide, and mixed sulfur/peroxide-vulcanizing systems (semi-EV/peroxide and EV/peroxide) were observed and compared. The blends were processed on a two-roll mill, and a fixed amount of carbon black was also incorporated. Amongst the blends, accelerated sulfur-vulcanizing systems exhibited higher torques, state of cure, tensile strength and elongation-at-break, in comparison with the peroxide-vulcanizing system, whereas the tensile modulus, hardness and cross-link density showed lower trend. In the mixed sulfur/peroxide-vulcanizing systems, it showed intermediate behavior to the individual sulfur- or peroxide-vulcanizing systems. This was associated to the interference of peroxide during the cross-linking formation. SEM micrographs of semi-EV-vulcanizing system exhibited more roughness and cracking path indicating that higher energy was required towards the fractured surface. The high cross-link density observed from the swelling study could be verified from the storage modulus (E′) where peroxide vulcanized blends provided a predominant degree of cross-linking followed by semi-EV, semi-EV/peroxide, EV and EV/peroxide-vulcanizing systems, respectively. The glass transition temperature (Tg) depicted at maximum peak of mechanical loss factor (tanδmax), indicating that semi-EV-vulcanizing system showed highest Tg value. The Tg values can be ordered as semi-EV > peroxide > semi-EV/peroxide > EV > EV/peroxide-vulcanizing systems. The Tg of rubber vulcanizates can be increased due to the restriction of molecular movement such as cross-link density.

Effects of electron-beam and sulfur crosslinking of epoxidized natural rubber on the friction performance of semimetallic friction materials

Semimetallic friction composites (SMFCs) consisting of epoxidized natural rubber (50mol% epoxidation, ENR 50), alumina nanoparticles, steel wool, graphite, and benzoxazine were prepared via melt mixing using a Haake internal mixer at 90°C and 60rpm rotor speed. The composites were vulcanized using sulfur and electron-beam (EB) crosslinking systems. The SMFC samples were then subjected to friction, hardness, porosity, and density tests to determine their friction and wear properties. The morphological changes in the samples were also observed under a scanning electron microscope. The friction and wear properties of SMFCs crosslinked via the EB irradiation and sulfur vulcanization systems were compared. The friction coefficients in normal and hot conditions, as well as the hardness and density of the irradiated SMFC, were higher than those of the sulfur-vulcanized samples at all applied doses. The porosity of the irradiated SMFC at 50, 100, and 150kGy was higher than that of the sulfur-vulcanized samples; however, the irradiated SMFC exhibited a descending trend at 200kGy. On the other hand, the specific wear rates of the irradiated samples were lower than those of the sulfur-vulcanized samples at all applied doses. The sample crosslinked via EB irradiation at 150kGy exhibited the greater tribological property compared with the sulfur-vulcanized SMFC, as indicated by the higher friction coefficient (approximately 0.461) and lower wear rate achieved at 150kGy irradiation.

Effects of Different Types of Crosslinking of Epoxidized Natural Rubber in Semi-Metallic Friction Materials on Friction Performance

Semi-metallic friction composites (SMFC) consist of epoxidised natural rubber with 50 mol % epoxidation (ENR50), alumina nanoparticle, steel wool, graphite and benzoxazine were prepared by melt mixing using Haake internal mixer at 90°C and 60 rpm rotor speed. The composites were vulcanized using different crosslinking systems, namely, sulfur and electron beam (EB) crosslinking. The samples were subjected for friction test in order to determine friction and wear properties of SMFC. The friction–wear properties of the SMFC crosslinked by electron beam irradiation and sulfur vulcanization system were compared. The friction coefficient in normal and hot condition of irradiated SMFC were higher than those of sulphur vulcanized samples at all applied doses. On the other hand the specific wear rates of irradiated samples were lower than the sulfur vulcanized samples at all applied doses. The sample crosslinked by EB irradiation at 150 kGy dose found to exhibit the best tribological property, as evident from the higher friction coefficient (about 0.461) and lower wear achieved at 150 kGy irradiation as compared to sulphur vulcanization of the SMFC.

Mechanical Properties and Biodegradability of Cuttlebone/NR Composites

Cuttlebone/natural rubber (NR) composites were successfully prepared via three sulfur vulcanization systems, conventional, semi-efficient and efficient vulcanizations. The clarification of the organic component from cuttlebone particles was performed by acid-based demineralization and protease treatment. The incorporation of the cuttlebone particles did not prevent the sulfur cross-linking reaction of NR in three sulfur curing systems. The mechanical properties, in terms of the modulus of composite materials, were improved by using cuttlebone particles as the reinforcing filler due to the presence of the organic components. The interaction between cuttlebone particles with the NR matrix was greater than that between commercial CaCO3 and NR matrix, as confirmed by scanning electron microscopy. The mechanism of the reinforcement effect of cuttlebone on NR vulcanizates is proposed. The degradation of the NR vulcanizates in both landfill and liquid bacterial culture assays revealed that cuttlebone/NR green composite materials could be degradable within 3 months and 8 weeks, respectively.

Comparison of the Different Vulcanization Techniques of Styrene Modified Natural Rubber (SNR) as an Impact Modifier of Natural Rubber-Based High Impact Polystyrene (NRHIPS)

Styrene modified natural rubber (SNR) is a modified rubber that can work as an impact modifier and compatibilizer for polystyrene (PS) matrix. The effect of different vulcanization techniques based on the sulfur vulcanization system has been investigated to produce SNR vulcanizates for natural rubber-based (NR) impact modifier for polystyrene. SNR is produced through emulsion polymerization of styrene monomer and deproteinized natural rubber (DPNR) latex. The styrene to DPNR ratio is 25:75 (wt/wt). SNR is vulcanized using sulfur vulcanization system with 1.5 phr sulfur loading for each blend. Each PS/SNR blend contains 20% rubber. Three different vulcanization techniques are proposed to produce SNR vulcanizates: mixed system ( in situ mixing together with physical mixing using two roll mills), in situ vulcanization, and physical mixing using two roll mills. PS/SNR blends show the in situ vulcanization process produce SNR vulcanizate, which gives the blends with better tensile properties and impact strength compared with the mixed system and physical mixing. The morphology in PS/SNR blends of PS/R1, PS/R2 and PS/R3 have further prove that SNR has better interaction with PS matrix compared with PS/*DPNR. PS/R3, which because they have in situ vulcanization SNR vulcanizate prepared by latex-based formulation, successfully produce SNR vulcanizates that can contribute as a natural rubber-based impact modifier.

Effect of grafted maleic anhydride content and recyclability of dynamically cured maleated natural rubber/polypropylene blends

AbstractMaleated natural rubbers (MNRs) were prepared using various levels of maleic anhydride (MA) at 4, 6, 8, 10, and 12 phr. Dynamically cured 60/40 MNR/PP blends with phenolic‐modified polypropylene (Ph‐PP) compatibilizer at a loading level of 5 wt % of PP were prepared by melt mixing process using sulfur vulcanization system. The influence of the level of MA on properties of the thermoplastic vulcanizates (TPVs) was studied. It was found that the mixing torque, apparent shear stress, shear viscosity, tensile strength, and hardness properties increased with increasing levels of the MA or grafted succinic anhydride groups in the MNR molecules. This is attributed to an increase in chemical interaction and reaction between methylol groups in the Ph‐PP molecules and polar functional groups in the MNR molecules upon increasing levels of the grafted succinic anhydride groups. As a consequence, compatibilizing block copolymers of MNR and PP blocks were formed. The block copolymers were capable of compatibilizing with MNR and PP blend components via the respective blocks. Recyclability of the MNR/PP TPVs was also studied. It was found that, after processing through a number of cycles by injection molding and extrusion processing, the TPV exhibited marginal decreases in mechanical properties. This corresponded to slightly increasing size of the dispersed vulcanized rubber domains. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Improving the Mechanical Properties of ENR/NBR Blends via Masterbatches with Initial Accelerator Concentration Gradients

Abstract Epoxidized natural rubber with 30 mol.% of epoxide (ENR-30) was blended with medium nitrile rubber (NBR) at the blend weight ratios of 30/70 and 70/30. Blend compounds were prepared via simple mixing and masterbatch techniques using TBBS as an accelerator. The masterbatches of ENR-30 initially consisted of higher accelerator concentrations compared with those of NBR, in order to compensate an effect of accelerator partition towards NBR phase. The initial accelerator concentration ratios in ENR-30 and NBR masterbatches before blending were at 50/50, 60/40, 70/30 and 80/20, respectively. The blend vulcanizates prepared by masterbatch mixing showed a significant improvement in tensile properties in comparison with those prepared by simple blend, and the initial accelerator concentration ratio in ENR-30/NBR masterbatches at 70/30 gave the highest ultimate tensile properties. The improvement in tensile properties was clearly observed for all the blends vulcanized with conventional, semi-EV and EV sulfur-vulcanization systems. The increase of tensile properties does suggest a better curative distribution, and hence a better crosslink distribution.

Epoxidized natural rubber‐bonded para rubber wood particleboard

AbstractPara rubber wood particleboard (PB) was prepared using NR based adhesives and hot pressing processes. Two types of NR based adhesives were used; epoxidized natural rubber (ENR) and unmodified NR. The ENR latex was prepared using in situ performic epoxidation. Molecular weight of the ENR molecules was then reduced by incorporating of a reducing agent; sodium nitrite solution. A chain scission reaction and epoxidation simultaneous occurred via a chain‐scission parallel epoxidation mechanism. Sulphur and multifunctional amine (i.e., hexamethoxymethylmelamine) curing systems were used to cure the adhesives. It was found that the hexamethoxymethylmelamine gave the PB with higher tensile strength than that of the sulphur vulcanization system. Furthermore, the tensile strength increased with increasing concentration of citric acid in the compounding formulation. Adhesion of the ENR adhesive with Parawood sawdust was observed to imporve by reducing molecular weight of the ENR molecules. That is, the highest tensile strength of the PB was observed for the ENR adhesive with the lowest $ {\overline {M}_{n}} $ (i.e., 1.10 × 105). This may be attributed to the adhesive with lower molecular weight exhibited greater ability to wet or cover the wood particle surfaces. As a consequence, greater chemical interaction between the adhesive and the wood particles was observed. POLYM. ENG. SCI., 47:421–428, 2007. © 2007 Society of Plastics Engineers.

Rheological properties and foam processibility of precured EPDM

AbstractEPDM foam was prepared by dynamically vulcanizing EPDM compound in a HAAKE rheometer firstly, then mixing the partially precured EPDM compound with a blowing agent and a sulfur vulcanizing system on a two roll mill. The compound was extruded through a cold feed extruder, and the extrudate was foamed in a circulating hot air oven. EPDM compound was vulcanized partly in the HAAKE rheometer, the final torque increases with increasing sulfur content. Rheological measurement shows the dynamic storage modulus, the loss modulus, and the complex viscosity of precured EPDM compound increase with increasing sulfur content. Then the partially precured EPDM compound was compounded with a blowing agent and a sulfur vulcanizing systems, Rheometric measurement shows that the rate of vulcanization of partially precured EPDM compound is not affected by the precure. The blowing results show that the foam processibility could be improved and the expansion ratio increases in the same processing condition for optimum partially precured EPDM compound, which indicates the optimum crosslink density for EPDM could enhance the efficiency of blowing agent AC. SEM shows that the foam articles have a closed‐cell structure with few open cells, and the large cells inlay among the small cells. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3387–3394, 2006