Mechanical,acoustical and flammability properties of SBR and SBR-PU foam layered structure

In this work a layer structure from styrene butadiene rubber (SBR) composites and PU foam with improved flame retardancy property and high sound absorption coefficient at frequency range (200–500 Hz). Different types of flame retardants; iron (acrylic-co-acrylamide) as metal chelate (MC), magnesium hydroxide (MOH) and sodium tripolyphosphate (STP) were blended with SBR. The type and loading level of flame retardant had a great effect on filler dispersion and consequently on mechanical properties of SBR. MOH exhibited the best dispersion as indicated from scanning electron microscope (SEM), and SBR/MOH samples had almost the highest crosslink density (16.04*10⁻⁵ g⁻¹ mol) and the best mechanical properties where the tensile strength was improved by 32.7% at 40 phr MOH. Horizontal burning rate of SBR composites indicated that MC and MOH reduced the rate of burning of SBR at all loading levels. TGA data presented that the addition of flame retardants to SBR increased the maximum decomposition temperature in all composites. A double and triple layer structures of SBR composite and PU foam was designed. The effect of 2.5 cm air cavity on the sound absorption coefficient of SBR-PU foam layered structure was studied. The presence of air cavity behind the layered structure improved the sound absorption in the range of (200–500 Hz) better than the existence of it between the layers. The triple-layer structure gave higher sound absorption coefficient at lower frequencies than that obtained with the double-layer structure where it reached to ≥0.98 at 315 Hz.     

Electron beam crosslinked gels—Preparation,characterization and their effect on the mechanical,dynamic mechanical and rheological properties of rubbers

Electron beam (EB) crosslinked natural rubber (NR) gels were prepared by curing NR latex with EB irradiation over a range of doses from 2.5 to 20 kGy using butyl acrylate as sensitizer. The NR gels were systematically characterized by solvent swelling, dynamic light scattering, mechanical and dynamic mechanical properties. These gels were introduced in virgin NR and styrene butadiene rubber (SBR) matrices at 2, 4, 8 and 16 phr concentration. Addition of the gels improved the mechanical and dynamic mechanical properties of NR and SBR considerably. For example, 16 phr of 20 kGy EB-irradiated gel-filled NR showed a tensile strength of 3.53 MPa compared to 1.85 MPa of virgin NR. Introduction of gels in NR shifted the glass transition temperature to a higher temperature. A similar effect was observed in the case of NR gel-filled SBR systems. Morphology of the gel-filled systems was studied with atomic force microscopy. The NR gels also improved the processability of the virgin rubbers greatly. Both the shear viscosity and the die swell values of EB-irradiated gel-filled NR and SBR were lower than their virgin counterparts as investigated by capillary rheometer.     

Effect of high temperature on reduction-controlling reaction rate of agricultural waste chars and coke with steelmaking slag

In the present research, mechanical and thermal properties of high-density polyethylene/wood flour were improved by incorporating nanoclay (Cloisite 30B) and antioxidant (Irganox B225) in the compound. Design of experiments was carried out to optimize composition among nine compounds and to investigate the effect of nanoclay and antioxidant (0–5 phr) and (0–0.4 phr), respectively. The results of mechanical tests showed approximately 24% increase in the tensile strength of compounds containing 2.5 and 5.0 part per hundred (phr) of the nanoclay in the composite compared with the same samples without nanoclay. The tensile modulus of composites increased 7.3% by increasing the level of nanoclay from 0 to 2.5 phr. However, a further increase in the nanoclay content led to a 4.3% decrease in tensile modulus. Evaluation of the thermal oxidation stability of samples confirmed that the thermal oxidation of composites decreased with increasing nanoclay from 0 to 5.0 phr and increased significantly with the addition of the antioxidant.

     

The effect of alkanolamide loading on properties of carbon black-filled natural rubber (SMR-L), epoxidised natural rubber (ENR), and styrene-butadiene rubber (SBR) compounds

The effect of Alkanolamide (ALK) loading on properties on three different types of carbon black (CB)-filled rubbers (SMR-L, ENR-25, and SBR) was investigated. The ALK loadings were 1.0, 3.0, 5.0 and 7.0 phr. It was found that ALK gave cure enhancement, better filler dispersion and greater rubber–filler interaction. ALK also enhanced modulus, hardness, resilience and tensile strength, especially up to 5.0 phr of loading in SMR-L and SBR compounds, and at 1.0 phr in ENR-25 compound. Scanning electron microscopy (SEM) proved that each optimum ALK loading exhibited the greatest matrix tearing line and surface roughness due to better rubber - filler interaction.     

Alkanolamide as an accelerator,filler-dispersant and a plasticizer in silica-filled natural rubber compounds

A feasibility study was carried out on the utilization of Alkanolamide (ALK) on silica reinforcement of natural rubber (NR) by using a semi-efficient cure system. The ALK was incorporated into the NR compound at 1.0, 3.0, 5.0, 7.0 and 9.0 phr. An investigation was carried out to examine the effect of ALK on the cure characteristics and properties of NR compounds. It was found that ALK gave shorter scorch and cure times for silica-filled NR compounds. ALK also exhibited higher torque differences, tensile modulus, tensile strength, hardness and crosslink density of up to 5.0 phr of ALK loading, and then decreased with further increases of ALK loading. The resilience increased with increased ALK loading. Scanning electron microscopy (SEM) micrographs proved that 5.0 phr of ALK in the silica-filled NR compound exhibited the greatest matrix tearing line and surface roughness due to higher reinforcement level of the silica, as well as better dispersion and cure enhancement.     

Colouring Agents for SBR Vulcanizates and Their Effects on Ageing and UV Radiation Resistance

Summary: Metal free and some metal-perylene polymers as well as some metal phthalocyanine polymers were incorporated into styrene butadiene rubber (SBR) compounds as colouring agents. The ageing and UV resistance of the vulcanizates obtained were studied in terms of their mechanical properties. The results obtained revealed that cobalt perylene and cobalt phthalocyanine polymers showed superior performance in SBR vulcanizates against thermal ageing and UV radiation. The optimum concentration of cobalt phthalocyanine polymer was found to be 1 phr (parts per hundred parts of rubber).     

The Effect of 3-aminopropyltrimethyoxysilane (AMEO) as a Coupling Agent on Curing and Mechanical Properties of Natural Rubber/Palm Kernel Shell Powder Composites

This research is conducted using palm kernel shell powder (PKS) as filler in natural rubber The effect of 3-aminopropyltrimethoxysilane as coupling agent on composites were studied at different palm kernel shell loading i.e, 0 5, 10, 15 and 20 phr The palm kernel shell was crushed and sieved to an average particle size of 5.53 μm The palm kernel shell filled natural rubber composites were prepared using laboratory size two roll mill The curing characteristics such as scorch time, cure time and maximum torque were obtained from rheometer The palm kernel shell powder filled natural rubber composites were cured at 150^oC using hot press according to their cure time Curing characteristics, tensile properties, rubber-filler interaction and morphological properties of palm kernel shell powder filled natural rubber were studied Scorch time and cure time show reduction but tensile strength, elongation at break, modulus at 100% (M100) and modulus at 300% (M300) increased with the presence of 3-aminopropyltrimethyloxysilane Rubber-filler interaction studies showed that rubber filler interaction in natural rubber filled with palm kernel shell powder improved with incorporation of 3-aminopropyltrimethyoxysilane.     

Comparative study on the effect of partial replacement of silica or calcium carbonate by bentonite on the properties of EPDM composites

The effects of the partial replacement of silica or calcium carbonate (CaCO₃) by bentonite (Bt) on the curing behaviour, tensile and dynamic mechanical properties and morphological characteristics of ethylene propylene diene monomer (EPDM) composites were studied. EPDM/silica/Bt and EPDM/CaCO₃/Bt composites containing five different EPDM/filler/Bt loadings (i.e., 100/30/0, 100/25/5, 100/15/15, 100/5/25 and 100/0/30 parts per hundred rubber (phr)) were prepared using a laboratory scale two-roll mill. Results show that the optimum cure (t₉₀) and scorch (t_S2) time decreased, while the cure rate index (CRI) increased for both composites with increasing Bt loading. The tensile properties of EPDM/CaCO₃/Bt composites increased with the replacement of CaCO₃ by Bt from 0 to 30 phr of Bt. For EPDM/silica/Bt composites, the maximum tensile strength and E_b were obtained at a Bt loading of 15 phr, with enhanced tensile modulus on further increase of Bt loading. The dynamic mechanical studies revealed a strong rubber-filler interaction with increasing Bt loading in both composites, which is manifested by the lowering of tan δ at the glass transition temperature (Tg) for EPDM/CaCO₃/Bt composites and tan δ at 40 °C for EPDM/silica/Bt composites. Scanning electron microscopy (SEM) micrographs proved that incorporation of 15 phr Bt improves the dispersion of silica and enhances the interaction between silica and the EPDM matrix.     

Graphene and MnO2 decorated graphene filled composites for electromagnetic shielding applications having excellent dielectric properties

Graphene nanoplatelets (GnP) and α-MnO₂ decorated GnP were integrated into an ethylene vinyl acetate (EVA) matrix using the dual mixing method (solution followed by melt mixing). GnP was added in 1, 3, 5, 8, 10 and 15 phr loadings into an EVA matrix to obtain composites and evaluate their various properties suitable for mechanical and electrical applications. The graphene nanoplatelets were further decorated with α-MnO₂ which was subsequently integrated into EVA at an 8 phr loading to form composites. It was observed in the GnP-EVA composites, that with an increasing GnP content, a substantial increase in the tensile strength (188%) over the neat polymer was observed at a 10 phr loading but reduced thereafter at a 15 phr loading. Dielectric permittivity of the composites were observed to increase with an increasing filler loading, the addition of α-MnO₂ also having a beneficial effect. Conductivity as well as the electromagnetic interference shielding performance were improved with increasing GnP concentrations. A maximum 28 dB of shielding was observed in the 15 phr loaded GnP-EVA composite whereas the α-MnO₂ decorated GnP-EVA composite showed a shielding efficiency of 22 dB at a concentration of 8 phr for a thickness of 2 mm with excellent thermal and mechanical properties. Overall, the composite material will find its application as a flexible EMI shielding material.     

The comparison of alkanolamide and silane coupling agent on the properties of silica-filled natural rubber (SMR-L) compounds

Alkanolamide (ALK) and Aminopropyltriethoxy Silane (APTES) were incorporated separately into silica-filled SMR-L compounds at 1.0, 3.0, 5.0 and 7.0 phr. It was found that compounds with both ALK and APTES exhibited cure enhancement, better filler dispersion and greater rubber-filler interaction. Both additives also produced modulus and tensile enhancements in the silica-filled SMR-L compounds, especially up to a 5.0 phr loading. At a similar loading, ALK exhibited higher reinforcing efficiency of silica than APTES.     

Compounding,mechanical and morphological properties of carbon-black-filled natural rubber/recycled ethylene-propylene-diene-monomer (NR/R-EPDM) blends

Blends of natural rubber/virgin ethylene-propylene-diene-monomer (NR/EPDM) and natural rubber/recycled ethylene-propylene-diene-monomer (NR/R-EPDM) were prepared. A fixed amount of carbon black (30 phr) was also incorporated. The effect of the blend ratio (90/10, 80/20, 70/30, 60/40 and 50/50 (phr/phr)) on the compounding, mechanical and morphological properties of carbon-black-filled NR/EPDM and NR/R-EPDM blends was studied. The results indicated that both the carbon-black-filled NR/EPDM and NR/R-EPDM blends exhibited a decrease in tensile strength and elongation at break for increasing weight ratio of EPDM or R-EPDM. The maximum torque (S′M_H), minimum torque (S′M_L), torque difference (S′M_H?M_L), scorch time (ts₂) and cure time (tc₉₀) of carbon-black-filled NR/EPDM or NR/R-EPDM blends increased with increasing weight ratio of virgin EPDM or R-EPDM in the blend. SEM micrographs proved that, for low weight ratios of virgin EPDM or R-EPDM, the blends exhibited high surface roughness and matrix tearing lines. The blends also showed a reduction in crack path with increasing virgin EPDM or R-EPDM content over 30 phr. This reduction in crack path could lead to less resistance to crack propagation and, therefore, low tensile strength.     

Use of wollastonite in a thermoplastic elastomer composition

Thermoplastic elastomer compositions (TPEs) based on wollastonite-filled SEBS/PP/oil blends were prepared and characterized. The development of new TPEs with improved mechanical strength may broaden their applications, especially for soft goods. Wollastonite is a natural filler that combines high thermal stability with low health hazard in comparison to other fibrous inorganic fillers. Morphological, thermal and mechanical properties of the composite materials were studied by transmission electron microscopy (TEM), thermogravimetry (TGA), tensile tests and dynamic mechanical analysis (DMA). The results indicate that the filler was mainly distributed as nanoparticles in the PS domains, improving the mechanical resistance of the materials even at low concentration (2 phr).     

Anisotropic studies of multi-wall carbon nanotube (MWCNT)-filled natural rubber (NR) and nitrile rubber (NBR) blends

50/50 NR/NBR blends with various MWCNT loadings were prepared by mixing with MWCNT/NR masterbatches on a two-roll mill and sheeted off at the smallest nip gap. Then, the effect of milling direction, machine direction (MD) and transverse direction (TD), on the mechanical and electrical properties of the blends was elucidated. Dichroic ratio and SEM results confirmed that most of the MWCNTs were aligned along MD when MWCNT was less than 4 phr, and the number of agglomerates increased when MWCNT was more than 4 phr. Additionally, anisotropic properties were clearly observed when 4 phr MWCNT was loaded. At 4 phr MWCNT, 100% modulus and tensile strength in the MD were about 1.5 and 1.3 times higher than those in the TD, respectively. Moreover, electrical conductivity in the MD was superior to that in the TD by about 3 orders of magnitude. Results from dynamic mechanical tests also showed that the maximum tan δ in the MD sample was lower than that in the corresponding TD sample. In addition, the storage modulus at 30 °C for the MD sample containing 4 phr MWCNT was 1.15 higher than that of the corresponding TD sample. This stronger reinforcement efficiency resulted from the combination of the greater alignment and dispersion of most MWCNTs in the MD sample.     

Rheological properties of styrene–butadiene rubber filled with electron beam modified surface treated dual phase fillers

The rheological properties of styrene–butadiene rubber (SBR) loaded with dual phase filler were measured using Monsanto Processability Tester (MPT) at three different temperatures (100°C, 110°C and 130°C) and four different shear rates (61.3, 306.3, 613, and 1004.5 s⁻¹). The effect of electron beam modification of dual phase filler in absence and presence of trimethylol propane triacrylate (TMPTA) or triethoxysilylpropyltetrasulphide (Si-69) on melt flow properties of SBR was also studied. The viscosity of all the systems decreases with shear rate indicating their pseudoplastic or shear thinning nature. The higher shear viscosity for the SBR loaded with the electron beam modified filler is explained in terms of variation in structure of the filler upon electron beam irradiation. Die swell of the modified filler loaded SBR is slightly higher than that of the unmodified filler loaded rubber, which is explained by calculating normal stress difference for the systems. Activation energy of the modified filler loaded SBR systems is also slightly higher than that of the control filler loaded SBR system.     

Vanillin‐derived phosphorus‐containing compounds and ammonium polyphosphate as green fire‐resistant systems for epoxy resins with balanced properties

Flame retardants from vanillin when utilized together with ammonium polyphosphate (APP) yield excellent synergistic flame retardancy toward epoxy resins. Bisphenol A epoxy resins have been widely used due to their excellent mechanical properties, chemical resistance, electrical properties, adhesion, etc., while they are flammable. Environment‐friendly and bio‐based flame retardants have captured increasing attention due to their ecological necessity. In this paper, 3 bio‐based flame retardants were synthesized from abundant and more importantly renewable vanillin, and their chemical structures were determined by ¹H NMR and ¹³C NMR. They were used together with APP (an environment‐friendly commercial flame retardant) to improve the fire resistance of bisphenol A epoxy resin. With the addition APP content of 15 phr, the modified bisphenol A epoxy resin could reach UL‐94V0 rating during vertical burning test and limit oxygen index values of above 35%, but reducing APP content to 10 phr, the flame retardancy became very poor. With the total addition content of 10 phr, the epoxy resins modified by 7 to 9 phr APP and 1 to 3 phr bio‐based flame retardants with epoxy groups or more benzene rings showed excellent flame retardancy with UL‐94V0 rating and limit oxygen index values of around 29%. The T_gs of the epoxy resins could be remained or even increased after introducing bio‐based flame retardants, as the control; those of APP alone‐modified epoxy resins compromised a lot. The green synergistic flame‐retardant systems have a great potential to be used in high‐performance materials.     

Compatibilizing effects for improving mechanical properties of biodegradable poly (lactic acid) and polycarbonate blends

Mechanical, morphological and rheological properties of polycarbonate (PC) and poly (lactic acid) (PLA) blends with compatibilizers have been investigated. Three types of compatibilizers were used: poly(styrene-g-acrylonitrile)-maleic anhydride (SAN-g-MAH), poly(ethylene-co-octene) rubber-maleic anhydride (EOR-MAH) and poly(ethylene-co-glycidyl methacrylate) (EGMA). The maximum value of the mechanical properties such as impact and tensile strengths of the PC/PLA (70/30, wt%) blend before or after hydrolysis was observed when the SAN-g-MAH was used as a compatibilizer at the amount of 5 phr. From the interfacial tension between PC and PLA which was determined from the weighted relaxation spectra using Palierne emulsion model, minimum value of interfacial tension (0.08 mN/m) was observed when the SAN-g-MAH (5 phr) was used. From the morphological studies of the PC/PLA (70/30) blends, the PLA droplet size showed minimum (0.19 μm) at the 5.0 phr SAN-g-MAH. From the results of mechanical, morphological and rheological properties of the PC/PLA (70/30) blend, it is suggested that the SAN-g-MAH is the most effective compatibilizer to improve the mechanical strength of the PC/PLA (70/30) blends among the compatibilizers used in this study, especially at the amount of 5 phr.     

Effect of polyvinylchloride on the properties of rubber vulcanizates

Natural rubber (NR) and styrene-butadiene rubber (SBR) were compounded with polyvinylchloride (PVC). Some physico-mechanical and dielectric properties of resulting rubber vulcanizates were measured. It was found that the addition of PVC to both NR and SBR results in slight decreases in tensile strength and elongation at break but a marked increase in oil-resistance of the vulcanizates. Moreover, the addition of PVC to NR slightly increases both dielectric constant and dielectric losses while the addition of PVC to SBR loaded with 50 phr carbon black (HAF) lowers these parameters. Both rubber blends, especially NR, show a reasonable stability with ageing.     

SBR composites reinforced with <Emphasis Type="Italic">N</Emphasis>-isopropyl-<Emphasis Type="Italic">N</Emphasis>′-phenyl-<Emphasis Type="Italic">P</Emphasis>-phenylenediamine-modified clay

SBR compounds including the N-isopropyl-N’-phenyl-p-phenylenediamine-modified clay(organoclay) were prepared.Effects of modified clay and antioxidant(IPPD) contents on mechanical and rheological properties of SBR composites were studied.FTIR results confirmed that the clay was chemically modified by IPPD and changed into an organoclay.X-ray diffraction(XRD) results confirmed the increase in interlayer distance of the clay due to the insertion of IPPD.Rheological and cure characteristics of SBR compounds were determined using RPA(Rubber Process Analyzer) and rheometer.Scorch time and cure time of SBR compounds decreased with introduction of the organoclay.Mechanical properties and heat aging resistance of the SBR composites were improved significantly by incorporation of the organoclay.     

Styrenated phenol modified nanosilica for improved thermo-oxidative and mechanical properties of natural rubber

The present work aims to prepare thermal and oxidation resistant Natural Rubber (NR) composites using antioxidant-modified nanosilica (MNS). The thermo-oxidative aging performance of the composites was evaluated by the variations in mechanical properties after aging at 100 °C for 24 h. The performance was further monitored through Scanning Electron Microscopy, Fourier Transform Infrared spectroscopy, Thermogravimetric Analysis, and Dynamic Mechanical Analysis. NR nanocomposite with 1–7.5 phr nanosilica (NS) and 3 phr MNS were prepared and its rheological properties were studied. A comparative study of the theoretical models yielded that modified Guth-Gold equation predicted Young's modulus better than other models. Thermal stability of natural rubber MNS composite was improved by 10 °C with pre-eminent mechanical properties like tensile strength and heat build-up. A linear relationship of compression set with modulus of all composites were also established. Equilibrium swelling test revealed improved crosslink density in NR MNS composite. The strong interaction between antioxidant and nanosilica enabled low migration of antioxidant in NR MNS composite. Hence its protective function after aging showed more effective than NR NS composites. These versatile functional properties of NR MNS composite suggest its potential application in electrical, electronic and high performance rubber products.     

Theoretical study of one- and two-photon absorption properties of pyrene derivatives

The geometrical structure, electronic structure, one-photon absorption (OPA) properties of pyrene and its derivatives have been theoretically studied by using density functional theory (DFT) method and Zerner’s intermediate neglect of differential overlap (ZINDO) methods, and their two-photon absorption (TPA) properties are calculated by the ZINDO/sum-over-states method. The results show that introducing donor groups to pyrene molecule, increasing the number of donor groups, extending the conjugated length, or forming circular conjugated dimer can increase the oscillator strength (f) in the TPA process and ultimately result in extremely large TPA cross-sections and strong OPA around 400 nm of pyrene derivatives. All these results give us some basic principles to design pyrene derivatives with large TPA cross-sections. This shed light into the significance of the pyrene derivatives as promising fluorescent probes in biochemistry when they were linked to some special recognizing groups.