Showing papers in "Rubber Chemistry and Technology in 1990"
TL;DR: In this article, a cubic equation in the invariant (I1−3) was proposed for the characterization of the elastic properties of carbon-black-filled rubber vulcanizates.
Abstract: A novel strain-energy function which is a simple cubic equation in the invariant (I1−3) is proposed for the characterization of the elastic properties of carbon-black-filled rubber vulcanizates. Conceptually, the proposed function is a material model with a shear modulus which varies with deformation. This contrasts with the neo-Hookean and Mooney-Rivlin models which have a constant shear modulus. The variation of shear modulus with deformation is commonly observed with filled rubbers. Initially, the modulus falls with increasing deformation, leading to a flattening of the shear stress/strain curve. At large deformations, the modulus rises again due to finite extensibility of the network, accentuated by the strain amplication effect of the filler. This characteristic behavior of filled rubbers may be described approximately by the proposed strain-energy function by requiring the coefficient C20 to be negative, while the coefficients C10 and C30 are positive. The use of the proposed strain-energy ...
540 citations
TL;DR: In this paper, a brief history of cavitation in rubber-like solids is described. But the condition for internal cracking appeared to be particularly simple. Whenever a stress was se...
Abstract: What can we conclude from this brief history of cavitation in rubber-like solids? At first, the condition for internal cracking appeared to be particularly simple. Whenever a stress was se...
159 citations
TL;DR: A comprehensive review of rolling loss research can be found in this paper, where the main concern was to understand the mechanism of tire rolling loss so that it could be effectively reduced, and accurate laboratory testing procedures were developed to identi...
Abstract: Up to and including World War II, not more than a dozen papers had been written on the subject of tire rolling loss. The number quickly increased after the oil embargo in 1976 and reached a peak around 1980 with more than thirty papers published per year. Several symposia were held in these years on the subject, and a comprehensive review of rolling-loss research was written by one of the authors of this article. Other, briefer reviews were published at that time by Barson, who discussed various techniques of measuring tire rolling loss; Moore, who pointed out ways of reducing rolling loss and hence fuel consumption; Clark, who touched upon some physical phenomena of tire rolling loss; and Chang and Shackleton, as well as Levine, who reviewed the effects of tire construction and materials on rolling loss. The main concern at that time was to understand the mechanism of tire rolling loss so that it could be effectively reduced. Hence, accurate laboratory testing procedures were developed to identi...
69 citations
TL;DR: In this article, the effect of active fillers on the stress-strain curves of vulcanizates is investigated. But the effect is not independent of crosslinking density, but is dependent on deformation, temperature, and surface activity of the filler.
Abstract: 1. Up to now, the application of the Einstein-Guth-Gold equation seemed to be limited to inactive fillers. 2. However, in the form of Equation (6), it describes with high accuracy the moduli of vulcanizates containing active fillers as a function of the filler volume fraction at least up to ϕ=0.22 at uniaxial elongations and for any given value of λ. 3. The effectiveness factor ƒ is independent of crosslinking density, but is dependent on deformation, temperature, and the surface activity of the filler. 4. If ƒ as a function of elongation is known, the respective stress-strain curves of filled networks can be calculated in advance for any given crosslinking density. 5. The interpretation of the effectiveness factor will require further investigations, especially with regard to the influence of the structure and surface activity of the filler.
56 citations
TL;DR: In this article, three types of aging were found to exist, and the factors determining the types were the temperature and the air-supply conditions irrespective of where the rubber was aged, in the tires or in the laboratory.
Abstract: Three types of aging were found to exist. The factors determining the types were the temperature and the air-supply conditions irrespective of where the rubber was aged, in the tires or in the laboratory. This means that the aging characteristics of a tire part in the field can be properly predicted if these factors in a tire are taken into account in the laboratory evaluation. In the first type, Type I, the aging yields increased M100 and reduced λb closely following the reference relation, Equation (3), which holds for the rubbers crosslinked with increasing the amount of curatives. This type of aging was found at temperatures below about 80°C, under either oxidative or anaerobic conditions. The extents of the changes in λb and M100 were large under the former conditions and small under the latter. As for the aging in the heavy-duty tires, the sidewall and the belt showed this type, with the changes to considerable extents suggesting an oxidative aging. The oxidative condition for the sidewall ...
55 citations
TL;DR: In this article, chemical antiozonants can be considered to function by scavenging ozone and, in the process, forming a protective barrier to prevent further ozone attack; however, more work is needed to define exactly what characteristics are required for the ozonized products to serve as an effective barrier.
Abstract: Currently, chemical antiozonants can be considered to function by scavenging ozone and, in the process, forming a protective barrier to prevent further ozone attack. Therefore, antiozonants must do two things: 1. react more rapidly with ozone than the rubber and 2. in the process, form products on the surface which prevent ozone from reaching both the underlying antiozonant and the rubber. Presently, more work is needed to define exactly what characteristics are required for the ozonized products to serve as an effective barrier. However, indications are that they must have a higher molecular weight than the antiozonant.
49 citations
TL;DR: In this article, the relation between the structure of the Solution SBR and the dynamic properties of carbon-black-filled SBR vulcanizates have been studied and the results obtained were as follows: 1. The hysteresis of the solution SBR was reduced markedly by the introduction of tin-carbon bonds at the polymer chain end.
Abstract: The relation between the structure of the Solution SBR and the dynamic properties of carbon-black-filled SBR vulcanizates have been studied. The results obtained were as follows: 1. The hysteresis of the Solution-SBR vulcanizates was reduced markedly by the introduction of tin—carbon bonds at the polymer chain end. 2. Among the structures of tin—carbon bonds, tin-butadienyl bonds were much more effective for the reduction of hysteresis than were tin—styryl bonds. 3. Solution SBR coupled with tin compounds with molecular weight of less than 105 was not so effective for the reduction of hysteresis. Furthermore, the mechanism of the improvement of dynamic properties was investigated. It was found that polymer—carbon-black bonds were formed through the reaction of tin—carbon bonds with the functional groups of carbon black. From model reactions, it is suggested that quinone groups on carbon black are involved.
43 citations
TL;DR: Finite-element analyses of rubber products such as seals and bearings have been published widely, often along with experimental validation, however, note that the implementation of the hyperelastic element in major codes has occurred recently.
Abstract: The application of finite-element analysis in rubber technology has been discussed. The intent has been to combine features of a tutorial, an exposition, and a survey. Attention has been limited to homogeneous cured rubber products. The finite-element method is a prime constituent of computer-aided engineering, and, as such, it is a powerful resource for the design and analysis of rubber components. Owing to rapid progress and greater availability of computer hardware and software and, in particular, computer-aided design systems, finite-element analysis is eminently practical. Difficulties such as incompressibility and large deformation, the subjects of a substantial literature, appear to have been successfully addressed. Finite-element analyses of rubber products such as seals and bearings have been published widely, often along with experimental validation. However, note that the implementation of the hyperelastic element in major codes has occurred recently. And, at the time of this review, i...
40 citations
IBM1
TL;DR: For three series of bimodal networks, the stress-relaxation rates and the tearing energies were shown to exhibit maxima at about the same concentrations of short chains as those at which t...
Abstract: For three series of bimodal networks, the stress-relaxation rates and the tearing energies were shown to exhibit maxima at about the same concentrations of short chains as those at which t...
38 citations
TL;DR: In this paper, the structure of both terminal units and alignment of the isoprene units give conclusive evidence for the initiation and termination mechanisms of rubber formation in fungi, and it is remarkable that the hydroxyl terminal group corresponding to the saponification product from the esterified terminal group was observed in the rubber samples by extraction from sporophores of L. volemus.
Abstract: The structure of both terminal units and alignment of the isoprene units give conclusive evidence for the initiation and termination mechanisms of rubber formation in fungi. As shown in Figure 4, the polymerization is estimated to start from trans, trans-farnesyl pyrophosphate and proceeds by successive condensation of IPP to form isoprene units in the cis configuration. The termination is presumed to occur by direct esterification of polyisoprenyl pyrophosphate (PIP-PP) or dephosphorylation of PIP-PP followed by esterification with fatty acids. It is remarkable that the hydroxyl terminal group corresponding to the saponification product from the esterified terminal group was observed in the rubber samples by extraction from sporophores of L. volemus after storage for 2–3 days in a refrigerator without the addition of salt. In these samples, unidentified 13C-NMR signals were also detected. These findings suggest that the direct esterification of PIP-PP is more likely as a termination reaction. It...
38 citations
TL;DR: In this paper, a new experimental procedure has been proposed for estimating the level of surface interaction activity of silica fillers in silicone rubber vulcanizates based on a simultaneous effect of the constant tensile strain and ammonia.
Abstract: A new experimental procedure has been proposed for estimating the level of surface interaction activity of silica fillers in silicone rubber vulcanizates. The method is based on a simultaneous effect of the constant tensile strain and ammonia. The sample of silica-filled silicone rubber vulcanizate is deformed in an ammonia atmosphere for 72 h. The ammonia cleaves the specific silica—PDMS hydrogen attachments. The bonds are formed in new positions in the deformed polysiloxane network between silica surface free silanols and PDMS after evaporation of ammonia. The resulting permanent deformation (tensile set) provides a measure of silica surface reactivity (interaction activity) with respect to a given silicone elastomer. It has been proven that the ammonia-induced tensile set is governed by the same mechanism as the increase of toluene swelling under an ammonia atmosphere. The results indicated that water plays an important catalytic role in the ammonia-induced cleavage of silica-PDMS attachments....
TL;DR: In this paper, a series of filled elastomers using a novel optoelectronic system was used to measure the Poisson's ratio of a set of fill elastomer materials.
Abstract: Poisson's ratio has been measured in a series of filled elastomers using a novel optoelectronic system. Relative precision of this measurement was found to be approximately 0.7% at 1% strain for this family of materials. The largest contributing error source was determined to be the tolerances that could be obtained in machining the surfaces of the test specimens. As a result of these errors, only three significant figures for Poisson's ratio can be achieved using this measurement approach. Material property tests conducted included constant strain rate and stress relaxation. Constant strain-rate results were used for general characterization, while the stress—relaxation data were employed to investigate time-dependent aspects of Poisson's ratio.
TL;DR: In this paper, a series of carbon blacks of widely varying morphology and microstructure were analyzed for surface compositional properties employing SIMS, XPS/ESCA, and GC-MS.
Abstract: A series of carbon blacks of widely varying morphology and microstructure were analyzed for surface compositional properties employing SIMS, XPS/ESCA, and GC-MS. These studies were supported by bulk analyses for hydrogen and oxygen content. Surface reactivity was assessed by means of inverse gas chromatography, moisture adsorption, and oxidation in an oxygen plasma. To directly assess carbon-black-polymer interaction, the carbon blacks were evaluated in SBR and IIR compounds for stress-strain and dynamic properties as well as bound rubber. The major findings of these studies are: 1. The combined results of hydrogen content, SIMS, and pyrolysis-GC-MS suggest a complex hydrogen functionality at the carbon-black surface, which governs the level of interaction with elastomers. 2. SIMS analyses have shown that the hydrogen functionality at the carbon-black surface is preserved after an 1173 K heat treatment in an inert atmosphere. 3. Gas-solid chromatography results indicate that this technique may be...
TL;DR: In the absence of a totally independent and universally accepted standard procedure, this crosscheck between two separate and absolute measurements for the degree of hydrogenation is the best possible support for their precision as discussed by the authors.
Abstract: A number of analytical techniques are available for the measurement of the residual unsaturation in HNBR polymers. However, to insure that high-quality HNBR products are produced, it is necessary to use a standard procedure throughout the industry which is quick, accurate, and precise. The two infrared methods discussed in this paper show good agreement with one another, as shown by the respective mean values in Table V. Thus, in the absence of a totally independent and universally accepted standard procedure, this crosscheck between two separate and absolute measurements for the degree of hydrogenation is the best possible support for their precision (1H-NMR spectroscopy for IR method #1 and IR spectroscopy for IR method #2). The two iodometric methods each exhibit significantly poorer precision ( 10 to 100 times) than either of the infrared methods. This is not surprising, since these wet chemical techniques are not discriminatory to any type of unsaturation present in the HNBR nor are they inh...
TL;DR: In this article, the aging characteristics of the rubber part in a tire can be satisfactorily predicted by using the Arrhenius equations with the same activation energy for the aging of a rubber in the laboratory and in the tires by introducing a factor to the tire equation.
Abstract: The belt-skim rubber of a passenger-car tire has changes in its tensile properties, M100 and λb, during service in the field. The changes are larger in higher temperature fields with an equivalent duration. It can be interpreted that the changes are caused simply by oxidative crosslinking similar to that which takes place on aging rubber sheets in an air oven at relatively low temperatures, below 100°C. The belt-skim compound showing better aging resistance in the laboratory also shows better aging resistance when used in a tire. Therefore, the aging characteristics of the rubber part in a tire can be satisfactorily predicted. The Arrhenius equations with the same activation energy can be used for the aging of a rubber in the laboratory and in the tires by introducing a factor to the tire equation. The factor is added to the atmospheric temperature to correct for a difference; however, it was found to be slight in the present case.
TL;DR: It is shown that fatigue testing based on fracture mechanics principles has major advantages over traditional methods or those which attempt to simulate the geometry of the composite tire in the laboratory.
Abstract: It is important to develop laboratory fatigue methods which are predictive of tire performance to minimize development time and costs. A basic premise of this paper is that fatigue testing based on fracture mechanics principles has major advantages over traditional methods or those which attempt to simulate the geometry of the composite tire in the laboratory. Basic fracture-mechanics theory will be reviewed, followed by summaries of previously published studies. Three new studies will illustrate the wide applicability of the methodology.
TL;DR: In this article, the utilization of network structure to impart stable orientation to a rubbery material has been largely unexploited to date, and it is demonstrated that the presence of a double network will...
Abstract: The utilization of network structure to impart stable orientation to a rubbery material has been largely unexploited to date. It is demonstrated that the presence of a double network will ...
TL;DR: In this paper, the authors show that the autohesion strength of elastomers increases linearly with the rate of detachment over the range 200 to 1000 mm/s, and that elastomer adhesion increases by a factor of only 2× to 3× when the contact pressure is increased by 3 orders of magnitude, from 2 kPa to 2 MPa.
Abstract: The following conclusions are obtained: 1. The autohesion strength of elastomers increases linearly with the rate of detachment over the range 200 to 1000 mm/s. 2. The autohesion strength increases by a factor of only 2× to 3× when the contact pressure is increased by 3 orders of magnitude, from 2 kPa to 2 MPa. 3. Autohesion strength develops rapidly in the early stages of contact for SBR, BR, and EPR, increasing from about 20 J/m2 to about 500–1000 J/m2 as the contact time increased from 1 to 100 ms. It increased more slowly thereafter, to about 10 kJ/m2 after a contact time of 1000 s. 4. The development of autohesion was exactly the same at 3°C as at 25°C. This feature is attributed to simultaneous changes in developing true contact, and in resisting separation after contact, that exactly cancel. 5. Adhesion between SBR and EPR is lower than the autohesion strength of the individual polymers over the whole range of contact time. On the other hand, the three strengths for SBR and BR are almost t...
TL;DR: In this paper, the small deformation-viscoelastic response of elastomers containing nonreinforcing filler has been investigated and the degree of this dependence was quantified using a power-law representation as a single nonlinear parameter.
Abstract: 1. The small-deformation-viscoelastic response of elastomers containing nonreinforcing filler has been investigated. Nonlinear viscoelastic behavior was observed as a pronounced strain-amplitude dependence. The degree of this dependence was quantified using a power-law representation as a single nonlinear parameter, m. 2. The magnitude of m was a function of formulation variables. It was found that m increased with the volume fraction and particle size of filler material, as well as the volume fraction of plasticizer. Reduced values of m were observed in the presence of bonding agent and with greater degrees of apparent crosslinking. The latter was controlled in this study through imbalanced urethane cures. 3. Nonlinear behavior of elastomers containing nonreinforcing filler has been compared and contrasted with the data base for carbon-black-reinforced elastomers. The major difference is in the effect of the surface area of filler particles. Nonlinear response in black-filled rubbers increases w...
TL;DR: The level of resistivity depends upon the number of contacts or near contacts between conductive particles in the rubber matrix as discussed by the authors, which is a major determinant in addition to physicochemical characteristics of the black.
Abstract: Uses are growing for rubbers with varying levels of resistivity. High electrical resistivity is very much essential in wire and cable insulation applications. Low levels of resistivity are needed for electrostatic discharge in phonograph records and many medical, industrial, and military products and for semiconductive cable compounds. The level of resistivity depends upon the number of contacts or near contacts between conductive particles in the rubber matrix. Loading level is obviously a major determinant in addition to physicochemical characteristics of the black. In the latter regard, the highly conductive grades are characterized by small particle size, high structure, high surface porosity, and low volatile content. One would, therefore, seek the reverse of those factors for high-resistivity rubbers. One of the goals of materials research now is to create new materials with physicomechanical properties tailored to a particular application and to understand the physical processes which dete...
TL;DR: In this paper, the cis : trans ratio of polybutadiene with 62% 1,2 units was found to be 1 : 4, which is larger than GNο=730 kPa for a 56% 1.2-poly butadiene and GNο = 550kPa for the 78% 1 2 polybutadienes.
Abstract: In the course of work on linear and ring polybutadienes with 62% 1,2 units, a number of discrepancies were noted with data on polybutadienes of various microstructure available in the literature. For example, GNο=870 kPa for our 62% 1,2-polybutadiene. This is larger than GNο=730 kPa for a 56% 1,2-polybutadiene and GNο=550 kPa for a 78% 1,2-polybutadiene sample. The cis : trans ratio of our 62% 1,2-polybutadiene, prepared with potassium counterion, is 1 : 4, On the other hand, the cis : trans ratio of 62% 1,2-polybutadiene prepared with a modified Li catalyst is estimated to be 1 : 2. It is conceivable that the different cis : trans ratio leads to different properties at constant 1,2 content. Nevertheless, the low levels of both the cis and the trans units are not expected to cause more than minor differences in the properties of the polybutadienes. Correct values for GNο of model polymers are important for the study of the influence of the chemical structure on the melt characteristics of a polym...
TL;DR: In this article, a study of blends of polyisoprene with polyisobutylene, 1H-NMR provides an excellent method for determining isoprene unsaturation in butyl rubber.
Abstract: The 1H-NMR results show that the majority of the isoprene units of butyl rubber are incorporated in 1,4 addition. Approximately 6% of the isoprene units undergo 1,2 enchainment. Based on our study of blends of polyisoprene with polyisobutylene, 1H-NMR provides an excellent method for determining isoprene unsaturation in butyl rubber. Furthermore, based on 1H-NMR measurement, FTIR procedures have been developed to quantify the isoprene content of butyl polymers and the concentrations of the three major bromobutyl isomers.
TL;DR: In this article, measurements of uniaxial extension and compression were made on model poly(dimethylsiloxane) (PDMS) [−Si(CH3)2−O−]x networks to examine the molecular theories of rubber elasticity.
Abstract: Measurements of uniaxial extension and compression were made on model poly(dimethylsiloxane) (PDMS) [−Si(CH3)2−O−]x networks to examine the molecular theories of rubber elasticity. The stress-strain isotherms showed that the Flory-Erman theory of rubber elasticity is in good agreement with experimental data from extension to compression (α−1: 0.3–13), while the Mooney-Rivlin relation is useful only in a specific region of extension ratio (α−1: 0.3–0.8). The experimental results strongly support the theory of Flory-Erman, rather than those of phantom and affine networks. It is thus evident that the Flory-Erman theory of rubber elasticity is the more nearly correct.
TL;DR: In contrast to expectations from rheometer studies of vulcanization behavior, the NMR technique has demonstrated that blends of NR and NBR vulcanized with sulfur/TMTM show a marked distribution of crosslinks in favor of the NR phase as mentioned in this paper.
Abstract: In contrast to expectations from rheometer studies of vulcanization behavior, the NMR technique has demonstrated that blends of NR and NBR vulcanized with sulfur/TMTM show a marked distribution of crosslinks in favor of the NR phase. The presence of even a minor proportion of NBR is sufficient to reduce the degree of vulcanization of the NR phase below levels deemed to be technologically necessary. Replacing the sulfur with a bis-alkylphenol disulfide reduces the degree of preferential distribution of crosslinks substantially. Interpretation of differential-swelling data for the blends on the basis of the swelling expected from a single polymer vulcanized with the same level of curatives as added to the blend gives the impression that the blends are lacking in interfacial adhesion. The interpretation enabled by the NMR estimates of degrees of crosslinking for the phases within the blends demonstrates that there is no lack of interfacial adhesion in blends of NR and NBR having a low acrylonitrile ...
TL;DR: In this paper, the frictional properties of rubber surfaces modified by various treatments have been investigated in order to understand the factors which reduce the friction and give the surface appropriate qualities for practical use.
Abstract: The frictional properties of rubber surfaces modified by various treatments have been investigated in order to understand the factors which reduce the friction and give the surface appropriate qualities for practical use. The study was in two stages. Initial measurements were made on thin sheets of hot-vulcanized natural rubber; then followed tests on latex glove material to see how the initial results and understanding related to the application. Measurements of friction coefficient were made against a wavy glass plate, giving reproducible results, and against finger skin. Supplementary measurements were made of surface roughness and hardness, liquid contact angle, and water absorption. Factors of importance in the reduction of dry friction were found to be an increased surface roughness and hardness. In practice, difficulties may be experienced under slightly wet or damp conditions, which can increase the friction above the dry value. Here it was found to help if the surface treatment could abs...
TL;DR: The versatility of solid state NMR for the characterization of elastomers and elastomer composites has been demonstrated as mentioned in this paper, and the use of solid-state H-l NMR should increase as instrumentation progresses, complementing the heteronuclear work.
Abstract: The versatility of solid state NMR for the characterization of elastomers and elastomer composites has been demonstrated. NMR can be used as an analytical tool for identifying the elastomer(s) present (including the sequence distribution and tacticity), measuring crosslink levels, and monitoring chemical modifications. In addition, with relaxation measurements, NMR provides direct physical insight into the dynamics, and hence the spatial interactions of elastomeric systems. The interfacial regions of heterogeneous systems such as IPNs, filled elastomers, and block copolymers can be probed. A variety of NMR parameters can be correlated with physical properties. Future studies will extend the use of variable temperature and high magnetic field strength measurements, as well as utilize the growing number of two-dimensional experiments. The use of solid state H-l NMR should increase as instrumentation progresses, complementing the heteronuclear work. Solid H-l NMR offers significant sensitivity incre...
TL;DR: A novel fluorocarbon elastomer of vinylidene fluoride, tetrafluoroethylene, and propylene has shown excellent aging behavior in the laboratory toward many aggressive engine oils at elevated temperature as discussed by the authors.
Abstract: The tendency in the automotive industry to use smaller engines has resulted in a situation where lubricating oils are exposed to higher operating temperatures. This is especially the case in countries where there is no restriction on highway speed. Amine-based additives present in the oils (e.g., as dispersants and corrosion inhibitors) tend to slowly attack the conventional fluorocarbon elastomer seals under these conditions. As a result of that attack, the seal becomes brittle and eventually fails. A novel fluorocarbon elastomer of vinylidene fluoride, tetrafluoroethylene, and propylene has shown excellent aging behavior in the laboratory toward many aggressive engine oils at elevated temperature. Its improved resistance as compared to conventional fluorocarbon elastomers is attributed to the replacement of hexafluoropropylene with propylene.
TL;DR: In this paper, it was found that norbornene does not participate in the reaction and that it even prevents the grafting of ethyl acrylate, which was a part of extensive experimental work which was done with the intention to chemically modify the rubber granulate for the purpose of enlarging the quantity of waste rubber to be possibly reused in the rubber industry.
Abstract: By the redox method and by gamma irradiation, it was possible to graft ethyl acrylate on to granulate of waste rubber. The quantity of grafted monomer was larger when gamma irradiation was used. When combining ethyl acrylate with 5-methylene-2-norbornene in the redox system with the intention to introduce more double bonds in the grafted granulate, it was found that norbornene does not participate in the reaction and that it even prevents the grafting of ethyl acrylate. This is just a part of extensive experimental work which was done with the intention to chemically modify the rubber granulate for the purpose of enlarging the quantity of waste rubber to be possibly reused in the rubber industry.
TL;DR: In this article, the equivalence of small-strain dynamic-mechanical testing and acoustic measurements has been demonstrated for carbon-black-filled rubber with a high concentration of 1,2-BR.
Abstract: Measurements of the dynamic properties of carbon-black-filled rubber can be carried out on most instrumentation at strains within the limits of linear behavior; thus, assessments of acoustic performance can readily be made. The equivalence of small-strain dynamic-mechanical testing and acoustic measurements has been demonstrated herein. Blends of NR with a high concentration of 1,2-BR are attractive candidates for damping applications because of the extended frequency range of the glass to rubber transition. One approach to improving the magnitude of the damping is to incorporate high levels of carbon black into the material. Significant interaggregate interaction, promoted for example by a low degree of carbon-black dispersion, will amplify the energy dissipation. The strain dependence of the dynamic properties implicit in such an approach can result in a damping performance sensitive to deformation. The loss tangent rises significantly after such a deformation, while the loss modulus experience...
TL;DR: In this paper, phase inversion occurred with the progress of vulcanization followed by fracture of the crosslinked phase into small particles, and an interesting trend appeared in the change in tensile strength and elongation at break of the statically vulcanized samples.
Abstract: Morphological studies with TEM and SEM showed that, in unvulcanized NR/LDPE blends, phase inversion occurred between NR/LDPE = 40/60 to 60/40; for dynamically vulcanized blends, LDPE remained as a continuous phase even at NR/LDPE = 70/30. Change in morphology of dynamically vulcanized blends of specified composition (NR/LDPE = 70/30) with vulcanization time as observed by SEM indicated that phase inversion occurred with the progress of vulcanization followed by fracture of the crosslinked phase into small particles. A model was proposed. For unvulcanized samples, the tensile strength steadily increased with increasing LDPE content, while their elongation at break first decreased and thereafter increased. Tensile strength and elongation at break of the statically vulcanized samples decreased to a minimum and thereafter increased with increasing LDPE content. However, an interesting trend appeared in the change in tensile strength and elongation at. break of the dynamically vulcanized system with i...