Effect of modification with rubber on properties and process of curing of epoxy–rubber adhesive compositions

The effect of SKN-30KTRA low molecular weight rubber on the elastic and strength properties of adhesive compositions made with epoxy-rubber composition, is shown. The data on the effect of rubber on curing of adhesive compositions are presented.     

Elastic and thermoelastic properties of “inorganic rubber”

Polymerization of cyclic phosphonitrilic chloride trimer was carried out at sufficiently high temperatures and for sufficiently long periods to cause gelation of the poly(dichlorophosphazene) formed. The resulting crosslinked material, called “inorganic rubber”, was found to be stable enough in the absence of moisture to permit reliable stress-strain and stress-temperature (thermoelastic) measurements in elongation. The stress-strain isotherms at low and moderate values of the elongation, α, showed that the networks had relatively low degrees of crosslinking; at high α and low temperature, they underwent strain-induced crystallization. The thermoelastic data confirmed the occurrence of crystallization at high α and low T. Thermoelastic values of the fraction f_e/f of the force that is of energetic origin were negative and generally large, with a magnitude that increased with increase in α, presumably because of the crystallization. In any case, the experimental values of f_e/f are in at least qualitative agreement with rotational isomeric state theory, which predicts this ratio to be large and negative.     

Thermal stability and flammability of butadiene–styrene rubber nanocomposites

Heterobimetallic oxalato complex precursors, manganese(II)tetraaquatris(oxalato)lanthanate(III)hexahydrate (MnOLa), cobalt(II)pentaaquatris(oxalato)lanthanate(III)trihydrate (CoOLa), nickel(II)pentaaquatris(oxalato)lanthanate(III)hexahydrate (NiOLa) and copper(II)diaaquatris(oxalato)lanthanate(III)monohydrate (CuOLa) of the type, M₃[La(C₂O₄)₃(H₂O) _m ]₂·nH₂O have been synthesized in aqueous medium. The precursors were characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction studies. The good crystalline nature with monoclinic structures predominates in MnOLa and NiOLa whereas triclinic structures were found in CoOLa and CuOLa. The solid-state thermal behaviour of the precursors was explored using TG, DTG and DTA in air. The MnOLa generated a mixture species consisting mainly of MnO₂, Mn₃O₄, Mn₅O₈, La₂O₃ and LaMn₇O₁₂ at 1000 °C through the formation of several intermediate species at 380 and 570 °C. The studies revealed that CoOLa led mainly to LaCoO₃ and La₂CoO₄ along with some oxides of both the cobalt and lanthanum at 1000 °C. In case of nickel analogue the mixture species identified at 1000 °C are mainly of La₂NiO₄, La₂O₃, Ni₂O₃ and NiO_2. In case of CuOLa the product at 1000 °C consisted of La₂CuO₄, La₂Cu₂O₅ and oxides of copper and lanthanum. The nature of decomposition of the precursors in nitrogen were seen from DSC study and the kinetic parameters i.e., E ^* , lnk ₀, ΔH ^# , ΔS ^# and order of reaction of all the steps were evaluated and discussed.     

Effect of nature and extent of crosslinking on swelling and mechanical behavior of styrene–butadiene rubber membranes

The influence of crosslink type and crosslink density on the swelling and mechanical behavior of styrene–butadiene rubber (SBR) membranes were studied in four aliphatic hydrocarbons. To vary the crosslink type and crosslink density, SBR was vulcanized by four different vulcanizing systems viz conventional, efficient, peroxide and a mixture of sulfur and peroxide. SBR vulcanizates having mono or disulfidic crosslinks (efficient system) exhibited the highest solvent uptake whereas those with C–C bonds (peroxide system) showed the lowest. SBR crosslinked by the mixed system showed superior mechanical properties in the unswollen, swollen and deswollen conditions. Arrhenius and thermodynamic parameters were evaluated from the diffusion data. Finally, a comparison between theoretical and experimental diffusion results was carried out.     

The effect of chlorosulphonated polyethylene on thermal properties and combustibility of butadiene–styrene rubber

This article describes the test results of thermal properties and flammability of the unconventionally cross-linked blends of chlorosulfonated polyethylene (CSM) and butadiene–styrene rubber (SBR) by means of zinc oxide or nano-zinc oxide. The thermal curves have been interpreted from the point of view of the chemical transitions of elastomers and their blends. It has been found that the content of combined chlorine in CSM exerts a significant influence on the cross-linking kinetics of CSM/SBR blends, their thermal properties and flammability.     

Mechanical properties,surface morphology and failure mode of γ-ray irradiated blends of polypropylene and ethylene-vinyl acetate rubber

The effect of ⁶⁰Co γ-radiation on the mechanical properties, surface morphology and failure characteristics of blends of polypropylene [PP] and ethylene-vinyl acetate rubber [EVA] has been studied with specific reference to the effect of blend ratio, dynamic crosslinking of the rubber phase and absorbed radiation doses. Samples were subjected to radiation in the dose range of 1 to 100 Mrad in air at room temperature at the rate of 0·321 Mrad/h. Both chain scission and crosslinking occur simultaneously in the blend samples. PP and blends containing higher proportions of PP (≥50%) undergo predominant chain scission at lower doses (≤50 Mrad), which causes a drastic drop in tensile strength, followed by a levelling out at higher doses of 100 Mrad. EVA undergoes crosslinking at lower doses resulting in an increase in tensile strength in the dose range 1 to 10 Mrad followed by a decrease in the range 10–25 Mrad. Further increase in radiation dose has little effect on tensile strength. The effect of radiation on stress-strain behaviour, elongation at break, energy at rupture and hardness was also studied. The morphology of the irradiated surfaces after an absorbed dose of 100 Mrad has been examined by scanning electron microscopy (SEM). In order to understand the effect of γ-radiation on the failure mechanism, tensile failure surfaces of both unirradiated and irradiated samples have also been examined by SEM.     

Quantitative characterization of toughening mechanisms of rubber modified polymers

The volume changes of rubber modified polymers under creep at room temperature were successfully used to characterize the toughening mechanisms of blends with brittle polymer matrices such as high impact polystyrene.This approach cannot be applied to pseudo-ductile polymers such as polypropylene and polyamide,because they are ductile when stretched at low speed at room temperature.Based on the time-temperature equivalence princi ple,the volume change at low temperature is proposed to characterize quantitatively the toughening mechanisms of polymer blends with ductile matrices,which is illustrated by applying this approach to rubber modified polypropylene     

Thermal stability and flammability of styrene–butadiene rubber (SBR) composites

The article presents the effect of attapulgite (ATT) and its synergic action with carbon or silica on the thermal properties and flammability of cross-linked styrene–butadiene rubber. It has been shown that ATT is active filler improving the thermal and mechanical properties of composites containing this aluminosilicate. The decreased flammability of vulcanizates containing ATT compared to that of unfilled vulcanizates results from good insulating properties of the ATT used. The considerable reduction in the flammability of composites containing ATT and carbon nanofiber or silica is connected, first of all, with the formation of a homogeneous boundary layer.     

In situ silica reinforcement of natural rubber by sol–gel process via rubber solution

The in situ silica filling of natural rubber (NR) was carried out via the sol–gel reaction using tetraethoxysilane. The effect of the in situ silica content on the curing, mechanical, dynamic mechanical and thermal properties of the composite vulcanizate materials was investigated in comparison to that with a commercial silica preparation. The Mooney viscosity of the in situ silica filled NR vulcanizates showed a lower value compared with that of the commercial filled ones. The mechanical properties of the in situ silica composite materials, i.e., the moduli and compression set, were improved compared with the commercial silica filler NR vulcanizates. The reinforcement effect of in situ silica did not accord with the Smallwood equation but in contrast was in good agreement with the Guth and Gold equation using a shape factor (f) which itself was in close agreement with estimates derived from independent TEM analysis. The pseudo-network structure of the in situ silica was low, which resulted in a lower storage modulus at 25 °C. By filling NR with in situ silica, the thermal properties of the composite vulcanized material were also improved, and well dispersed in situ silica particles within the NR matrix were also observed.     

Relation between stress relaxation and aging resistance of rubber vulcanizates—some preliminary investigations

In this paper some details are given for the construction of a simple balance for the measurement of stress relaxation at constant elongation. A simple means of obtaining equal strain in the two parts of the strained specimen is provided. By means of four typical stocks covering the widest possible range of aging resistance it is shown that the stress relaxations give approximately the same estimate of stability as does the normal Geer test using 2 mm. dumbbell specimens. As a measure for stress relaxation the time is used that is required to obtain 50% of the value of the interpolated modulus at 200% elongation 6 seconds after the straining zero time at 110°C. The parameter for the aging test is the time in days at 70°C. for the 50% value of tensile strengths. The range for the stress relaxation parameter may be estimated to 8–1200 min. and the aging parameter from 10–600 days. Finally the concordance of temperature coefficient for relaxation and oxidation rates is shown.     

Effect of π–π interaction between carbon nanotubes and phenyl groups on the thermal stability of silicone rubber

Journal of Thermal Analysis and Calorimetry - To investigate the effect and mechanism of π–π interaction between carbon nanotubes (CNTs) and phenyl groups on the thermal stability...     

Chemical modification of chlorinated rubbers—III. Quantitative study of the grafting of chlorinated rubber by aminoesters and versamids

A quantitative study of the grafting of chlorinated rubber by ethyl 11-aminoundecanoate is carried out. A self-condensation of the aminoester takes place during the grafting; its extent is determined. The grafting of CR by versamid 100 (acetylated or not) is studied quantitatively by several analytical methods (i.r., ¹H- and ¹³C-NMR) and they are compared with respect to accuracy. Non-crosslinked versamid-grafted-chlorinated rubber is obtained.     

Effect of ZnO nanoparticles on kinetics of thermal degradation and final properties of ethylene–propylene–diene rubber systems

The morphology, thermal degradation behavior in addition to static and dynamic mechanical properties of various ethylene?Cpropylene?Cdiene (EPDM) rubber compounds containing nano-zinc oxide (NZnO) were investigated compared to those of EPDM with ordinary-sized ZnO (OSZnO). The field-emission scanning electron microscopy studies showed that unlike the conventional system, the formation of large size ZnO agglomerates was discouraged for NZnO filled systems. Thermogravimetric analysis (TG) revealed that the thermal degradation of EPDM system was delayed upon the inclusion of NZnO instead of OSZnO in the compound. The kinetic analysis of TG data based on Friedman and Kissinger methods showed that the nanocomposite samples exhibited higher activation energy (E _a ) and lower order of reaction (n) over the conventional system, suggesting the enhancement of thermal stability upon decreasing ZnO particle size. The results obtained from dynamic mechanical analysis and static mechanical characterizations in terms of hardness, resilience, and abrasion tests interestingly indicated that NZnO not merely could act as a thermal insulator, but also could perform as a nano-filler to improve the final performance of EPDM elastomers.     

Dielectric properties of perbunan rubber: γ-irradiation effects

A systematic dielectric study over a frequency range extending from 200 Hz to 100 kHz and temperature ranging from 20° to 60°C has been carried out on perbunan rubber. The acrylonitrile content of the rubber samples was 28% and 38%. The effect of 15 MR γ-irradiation on the dielectric properties of both samples was studied and the results are interpreted. The study revealed that NBR-38 is better than NBR-28 for insulating purposes.     

A critical analysis of the effect of crosslinking on the linear viscoelastic behavior of styrene–butadiene rubber and other elastomers

The linear viscoelastic behavior in dynamic shear and tensile creep at temperatures from −30 to 70 °C is measured for an styrene–butadiene rubber (SBR) elastomer cured with dicumyl peroxide to crosslinking densities between 0 and 23.5 × 10⁻⁵ mol/cm³. The G′, G″, and tan δ isotherms are analyzed by time–temperature superposition (TTS), where the tan δ master curves are consistent with those of Mancke and Ferry. However, to achieve the TTS in the lightly crosslinked SBR systems, an anomalous vertical shift is required in the narrow temperature region from 10 to 30 °C. The vertical shift factor in this temperature region is not the standard from rubber elasticity. No anomalous behavior is detected in the equilibrium modulus, which is a linear function of temperature in accordance with the classical theory of rubber elasticity. In contrast to SBR, standard vertical shifts are required to effect TTS for uncrosslinked polybutadiene and an ethylene propylene diene monomer elastomer. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Application of multi-capillary column – ion mobility spectrometry (MCC-IMS) in rubber chemistry and technology

In this paper the possibility for authentication and differentiation of various styrene butadiene rubbers (SBRs) was investigated. Seven types of SBR were analyzed by multi-capillary column (MCC) ion mobility spectrometer (IMS) and their spectra compared. The analysis of volatile organic compounds (VOCs) releasing from the rubbers revealed the presence of characteristics signals, which can be assigned only to a specific material. Such “markers”, when defined for other polymer materials, can be used for their authentication. In the second part of the paper, the blend of epoxidized natural rubber and poly-3-hydroxybutyrate-co-4-hydroxybutyrate (ENR/P(3,4)HB) was subjected to different types of aging. MCC-IMS spectra of not aged, thermal, climatic and UV aged samples were collected and differences between the signals discussed. The study showed possibility of authentication of polymeric materials and processes. The paper is a some kind of introduction to the use of analytical properties and advantages of MCC-IMS technique in chemistry, technology and exploitation of polymer materials.     

Effect of epoxidation of natural rubber on the pervaporation separation of acetone–chlorinated hydrocarbon mixtures

The pervaporation separation and the swelling behavior of chlorinated hydrocarbon/acetone mixtures were investigated using natural rubber (NR) and epoxidized natural rubber (ENR) membrane with 25 and 50 mol% epoxidation, respectively. The swelling degree increases with increase in the epoxidation level. The flux and separation factor of the membranes were determined both as a function of mole percent epoxidation and of the feed mixture composition. The membranes were found to be permselective to chlorinated hydrocarbons from acetone–chlorinated hydrocarbon mixtures. The flux decreases with increase in epoxidation level, whereas the separation factor increases. The permeation decreases and separation factor increases with increase in the acetone feed concentration. The availability of raw materials, low cost of implementation and easy processability of the system makes this method of separation highly applicable and recommendable.     

Stabilization effect of potential antioxidants on the thermooxidative stability of styrene–butadiene rubber

Effects of several heterocyclic compounds containing nitrogen, trisubstituted amines and diamines and molecules based on N,N,N′,N′,N′′,N′′-substituted-[1,3,5]triazine-2,4,6-triamine in preventing thermooxidative degradation of styrene–butadiene rubber (SBR) have been studied using non-isothermal DSC measurements. The aim of this study was to determine and compare the stabilizing effect of individual compounds and to select the structures with the best antioxidative properties. In order to compare the stabilizing effect of the compounds, induction periods and protection factors have been calculated. The treatment of the experimental data was carried out using a method based on a non-Arrhenian temperature function. The results show that better antioxidative properties can be assigned to heterocyclic compounds. On the other hand, molecules containing triazine structures exhibited only negligible stabilizing effect on SBR at lower temperatures and even destabilizing effect at higher temperatures.     

Permeation of hydrocortisone and hydrocortisone 21-alkyl esters through silicone rubber membranes — relationship to regular solution solubility behavior

Rates of permeation of 75 μm thick silicone rubber membranes by hydrocortisone and six homologous hydrocortisone 21-alkyl esters, all applied to the membranes in aqueous media, were assessed in small glass diffusion cells. Solubilities of these agents in water and hexane were also determined. The permeability coefficient of hydrocortisone was 7.4 x 10⁻⁵ cm/hr. Permeability coefficients for the esters ranged from 2.3 x 10⁻³ cm/hr (acetate) to 6.4 x 10⁻¹ cm/hr (heptanoate). A direct correlation was found between permeability coefficients and lipophilicity but it appears that the heptanoate eater's mass transfer coefficient is substantially boundary layer controlled. Assessment of fluxes of the steroid solutes from their respective saturated aqueous solutions was made. The flux for hydrocortisone through silicone rubber was greater than the flux for the acetate ester. Thereafter, fluxes of the esters from saturated solutions systematically increased to the point where fluxes for the 21-hexanoate and 21-heptanoate esters were 20 times greater than found for hydrocortisone. This suggests that far more steroid can be delivered through a lipid membrane when the steroid is appropriately derivatized. The overall permeability pattern fits behavior expected of a barrier having a lipid membrane bounded by hydrodynamic layers. The pattern of permeability from saturated solutions was predictable using regular solution theory.