Dynamic Mechanical Properties of Carbon Black Filled Ethylene Vinyl Acetate Rubber

Abstract

The dynamic mechanical properties of ethylene vinyl acetate (EVA) rubber filled with different loadings of carbon black and at different degrees of crosslinking were studied over a wide range of temperatures (-150° to +200°C). The loss tangent (tan δ) versus temperature plots indicated presence of different transitions. The α-transition (or the glass-rubber transition) corresponding to the maximum in tan δ value, occurred at ?17°C, which is the principal glass-transition temperature (abbreviated as T _g) of EVA rubber. The γ-transition occurred in the temperature region of ?125° to ?135°C, while the β-transition appeared as a shoulder in the temperature region of ?65° to ?75°C. Besides, there was also a high tempeature transition around +62°C which is known as liquid to liquid transition (T _1.1). Incorporation of carbon black filler did not cause any shift of T _g, while the tan δ peak values at T _g decreased sequentially with increase in filler loading. The γ- and β-relaxations were found to be insensitive to filler loading. The T _1.1 transition, however, was found to be suppressed by incorporation of carbon black filler particularly at high loading. Extent of crosslinking did not influence the T _g But, the T _1.1 transition, which was prominent with the lightly crosslinked system was found to be suppressed at high level of crosslinking. Strain dependent dynamic mechanical properties under isothermal conditions showed that the secondary structure breakdown of carbon black filler under the effect of strain amplitude is influenced by the degree of crosslinking of EVA rubber.     

Temperature and microstructure dependence of the Rheo-optical properties of polybutadienes

The present investigation covers the isothermal stress–strain–birefringence behavior of various polybutadienes between ?30°C and 110°C. Birefringence measurements were also made under constant stress as a function of temperature in the low temperature region between ?30°C and ?120°C. The polybutadienes studied were two high cis-1,4 (prepared by different catalysts), a linear medium cis, and an emulsion polybutadiene. At temperatures at which the photoelasticity theory could be applied, the segmental polarizability anisotropy, its temperature dependence, and other parameters associated with an elastic polymeric network were determined. The influence of the degree of crosslinking was examined. At the low temperatures, microstructure was shown to have a pronounced effect on the photoelastic properties, the crystallization phenomena, and the glass–rubber transitions.     

Asymmetric addition of thiol to diene polymer in the presence of optically active amines as catalyst

The asymmetric addition reaction of thiolacetic acid or benzylmercaptan to diene polymer (natural rubber, cis- and trans-1,4-polyisoprene, _cis-1,4-polybutadiene, various styrenebutadiene copolymers and alternating acrylonitrile-butadiene copolymer) by optically active catalysts such as d-bornylamine ([α]d?45.2°), l-aspartic diethyl ester (?11.2°), l-aspartic dibutyl ester (?5.3°) were carried out in benzene at room temperature to 90°C. The optically active polymers were obtained from natural rubber and cis-1,4- and trans-1,4-polyisoprene, but were not obtained from cis-1,4-polybutadiene, styrene-butadiene copolymers, and butadiene-acrylonitrile copolymer. The [α]²⁵_D value of optically active derivatives was ?0.1° ～ ?1.0° (in benzene), and the optical rotatory dispersion curves were found to fit the simple Drude equation.     

Reaction of thiol to diene polymer in the presence of various catalysts

The addition reaction of benzylmercaptan to diene polymer (natural rubber, and cis-1,4-polyisoprene) by various optically active catalysts such as d-camphorsulphonic acid, d-percamphoric acid, and active-amylalcoholate (sodium and barium) were carried out in benzene or anisole at room temperature to 100°C. The optically active adduct polymer was only obtained from the reaction of benzylmercaptan to natural rubber and cis-1,4-polyisoprene by active-amylalcoholate (barium), but was not obtained by the other catalysts. The [α]²⁵ value of optically active adduct polymer was ?0·1°C～?0·6°C (in benzene), and the optical rotatory dispersion curves were found to fit the simple Drude equation. The reaction of benzylmercaptan to cis-1,4-polybutadiene, various styrene-butadiene copolymers, and alternating butadiene-acrylonitrile copolymer were carried out, but the optically active adduct polymers were not obtained by these catalysts.     

Physical properties of ethylene vinyl acetate copolymer (EVA)/natural rubber (NR) blend based foam

In this study an attempt was made to improve the rebound resilience and to decrease the density of ethylene‐vinyl acetate copolymer (EVA) foam. For this purpose, EVA was blended with natural rubber (NR), and EVA/NR blends were foamed at 155°C, 160°C, and 165°C. To investigate the correlation between crosslinking behavior and physical properties of foams, crosslinking behavior of EVA/NR blends was monitored. The physical properties of the foams were then measured as a function of foaming temperatures and blend compositions: 165°C was found to be the optimal temperature for a crosslinking of EVA/NR foam. As a result, the density of EVA/NR blend foamed at 165°C was found to be the lowest. EVA/NR (90/10) blend, foamed at 165°C, showed lower density, better rebound resilience, and greater tear strength than EVA foam. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2212–2216, 2004     

Study on the damping of EVM based blends

The mechanical and damping properties of blends of ethylene‐vinyl acetate rubber(VA content >40 wt %) (EVM)/nitrile butadiene rubber (NBR) and EVM/ethylene‐propylene‐diene copolymer (EPDM), both with 1.4 phr BIPB (bis (tert‐butyl peroxy isopropyl) benzene) as curing agent, were investigated by DMA. The effect of polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and dicumyl peroxide (DCP) on the damping and mechanical properties of both rubber blends were studied. The results showed that in EVM/EPDM/PVC blends, EPDM was immiscible with EVM and could not expand the damping range of EVM at low temperature. PVC was miscible with EVM and dramatically improved the damping property of EVM at high temperature while keeping good mechanical performance. In EVM/NBR/PVC blends, PVC was partially miscible with EVM/NBR blends and remarkably widened the effective damping temperature range from 41.1°C for EVM/NBR to 62.4°C, while CPVC mixed EVM/NBR blends had an expanded effective damping temperature range of 63.5°C with only one damping peak. Curing agents BIPB and DCP had a similar influence on EVM/EPDM blends. DCP, however, dramatically raised the height of tan δ peak of EVM/NBR = 80/20 and expanded its effective damping temperature range to 64.9°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal crosslinking of cis-1,4-polybutadiene at ultrahigh pressures

cis-1,4-Polybutadiene (BR) samples, in the absence of crosslinking agents, were simultaneously compressed by ultrahigh pressures (>4.0 GPa) and annealed between 25 and 180°C. The BR samples were crosslinked when the annealing temperatures were above 100°C. The Vickers microhardness of the treated BR increased and the extent of swelling decreased rapidly as the annealing temperature increased, indicating that the crosslinking density increased. Solid-state carbon-13 nuclear magnetic resonance and Fourier transform infrared spectroscopy results showed that some C=C bonds in the BR were opened to form the crosslinking network structures with C—C linkages and that a partial cis–trans isomerization took place during the treatments. Differential scanning calorimetry studies revealed that the glass transition temperature increased and the crystallinity decreased as the annealing temperature increased. When the annealing temperature exceeded 140°C, the treated BR samples lost their rubbery elastic characteristics completely and became brittle materials. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2131–2140, 1998     

High damping epoxized natural rubber/diallyl adiallyl phthalate prepolymer (ENR/DAP‐A) blends engineered by interphase crosslinking

While a great diversity of rubber/plastic damping blends have been reported, the damping trough resulted from phase incompatibility, which usually exists between the glass transition temperatures (T_g) of each component, remains an unsolved problem by separating the effective temperature range of damping blends. Herein, we reported a new and facile way of preparing rubber/plastic binary blends with high damping property by eliminating the inherent damping trough. Specifically, we envisaged that peroxides can trigger free radical reactions both within and between epoxidized natural rubber/diallyl phthalate prepolymer moieties, which serve as the co‐vulcanizer to generate interphase reactions thus enhancing phase compatibility. Accordingly, apart from the resulting high damping epoxidized natural rubber40/diallyl phthalate prepolymer binary blends with an effective (tan δ_min > 0.35) temperature range of 178 °C from −33 to 145 °C, the proposal has also been demonstrated via the support of broadband dielectric spectrometer testing, dynamic mechanical analysis, and differential scanning calorimetry. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46300.     

Solid-state 13C-NMR studies of changes in crosslinked carbon structure of natural rubber during heating under air and nitrogen environments

The chemical changes that occur in thermal degradation of sulfur-cured natural rubber were investigated using ¹³C-NMR analysis. The crosslinked carbons formed during the vulcanization process appear in the NMR spectra as peaks representing the various structures formed. Samples of vulcanized rubber were heat-aged at 100 and 150°C under both air (oxidative) and nitrogen (inert) environments to assess both temperature and oxidative effects. Changes were observed by measuring peak areas under the crosslinked carbon peaks. A- and B-type cis monolinkages were found to decompose much faster by oxidative factors at both 100 and 150°C than under nitrogen at either temperature. The polylinkages, however, showed the opposite result of thermal degradation predominating over oxidative factors. Cis–trans isomerization of the main chain carbons was observed at the higher temperature while absent at 100°C. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1371–1383, 1998     

Effect of viscoelasticity on the spherical and flat adhesion characteristics of photopolymerizable acrylate polymer networks

This research is the first of its kind to study the comparison between spherical and flat probe adhesion behavior as a function of viscoelasticity. Viscoelastic properties were tailored through the use of acrylate networks synthesized from tert-butyl acrylate and poly(ethylene glycol) dimethacrylate (PEGDMA) solutions. The molecular weight and the weight fraction of PEGDMA crosslinker was altered to maintain a constant glass transition temperature of approximately 57 °C, but systematically vary the viscoelastic properties and the rubbery moduli (1–62 MPa). Dynamic mechanical analysis was performed to characterize the low-strain thermo-mechanical behavior of the materials. Viscoelastic behavior of the materials was characterized by creep testing and was observed to inversely correlate with crosslinking density. The samples tested with the spherical probe exhibited low pull-off forces at temperatures well above and well below the glass transition temperature of the material. A maximum in pull-off force was observed in the vicinity of the glass transition temperature owing to the viscoelastic energy dissipative processes. The peak in pull-off force was observed to decrease with an increase in crosslinking density and modulus. Adhesion measurements using the flat probe demonstrated a strong dependence of pull-off force on the modulus of the material above the glass transition temperature. It is concluded that viscoelasticity is a dominating factor in increasing the pull-off force values in the vicinity of the glass transition, while it plays a little or no role for temperatures +/−20 °C away from transition region , opening the possibility of thermally switchable adhesives.     

Dynamic mechanical properties of semi‐interpenetrating polymer network‐based on nitrile rubber and poly(methyl methacrylate‐co‐butyl acrylate)

In this article, semi‐interpenetrating polymer network (Semi‐IPNs) based on nitrile rubber (NBR) and poly(methyl methacrylate‐co‐butyl acrylate) (P(MMA‐BA)) were synthesized. The structure and damping properties of the prepared Semi‐IPNs blends were characterized and by fourier transform infrared spectrum (FTIR), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), thermogravimetric analysis (TGA/DTG), and tensile mechanical properties. The results showed that interpenetrating network based on P(MMA‐BA) and NBR was successfully obtained, which showed the improved thermal stability compared to NBR/P(MMA‐BA)‐based two‐roll mill blends. Furthermore, Semi‐IPNs showed significantly better the dynamic mechanical properties than that of the two‐roll mill system. With the increasing feed ratio of BA and MMA during the preparation of Semi‐IPNs, the loss peak position for P(MMA‐BA) in NBR/PMMA IPNs shifted to a lower temperature from 20°C to ?17°C, and when NBR in Semi‐IPNs was accounted for 40 wt %, the dynamic mechanical thermal analysis showed that much more advanced damping material with wider temperature range (?30°C < T < 80°C) as tan δ > 0.45 can be achieved. Therefore, it was expected as a promising way to obtain the excellent damping materials with good oil‐resisted properties according the Semi‐IPNs system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40217.     

DMA analysis of the damping of ethylene–vinyl acetate/acrylonitrile butadiene rubber blends

The mechanical and damping properties of blends of ethylene–vinyl acetate rubber (VA content > 40% wt) (EVM)/acrylonitrile butadiene rubber (NBR), with 1.4 phr BIPB [bis (tert‐butyl peroxy isopropyl) benzene] as curing agent, were investigated by DMA and DSC. The effect of chlorinated polyvinyl chloride (CPVC), silica, carbon black, and phenolic resin (PF) as a substitute curing agent, on the damping and mechanical properties of EVM/NBR blends were studied. The results showed that 10 phr CPVC did not contribute to the damping of EVM700/NBR blends; Silica could dramatically improve the damping of EVM700/NBR blends because of the formation of bound rubber between EVM700/NBR and silica, which appeared as a shoulder tan δ peak between 20 and 70°C proved by DMA and DSC. This shoulder tan δ peak increased as the increase of the content of EVM in EVM/NBR blends. The tensile strength, modulus at 100% and tear strength of the blend with SiO₂ increased while the elongation at break and hardness decreased comparing with the blend with CB. PF, partly replacing BIPB as the curing agent, could significantly improve the damping of EVM700/NBR to have an effective damping temperature range of over 100°C and reasonable mechanical properties. Among EVM600, EVM700, and EVM800/NBR/silica blend system, EVM800/NBR/silica blend had the best damping properties. The EVM700/NBR = 80/10 blend had a better damping property than EVM700/NBR = 70/20. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Study on the high-temperature damping properties of silicone rubber modified by boron-terminated polysiloxane

Rubber damping materials have important applications in modern industrial systems. However, their damping temperature range is low, which is not suitable for the damping demand under high temperature conditions. At present, there is very little research on the damping performance of rubber under high temperature conditions. Silicone rubber has excellent high temperature resistance but poor damping in its application temperature range. In this study, a boron-terminated polysiloxane (PBS) was prepared by modifying hydroxy-terminated polydimethylsiloxane (PDMS-OH) with boric acid (BA). The molecular structure of PBS was confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) analysis. Rheology measurements revealed that PBS was a “shear hardening” material. Then, the silicone rubber was modified with PBS. With the introduction of boron atoms, boron and oxygen dative bonds with dynamic properties could be formed inside the silicone rubber, which played an energy dissipation role in the process of association/dissociation. Dynamic mechanical analysis (DMA) showed that the loss factor (tan δ) of modified silicone rubber was greater than 0.3 in the temperature range of 81.5°C–250°C, which was higher than the loss temperature range of conventional damping rubber. The cyclic stress–strain test also showed that the modified silicone rubber still had high dissipation coefficient (DE) at high temperature. Therefore, the PBS-modified silicone rubber prepared by this method achieved excellent damping performance under high temperature conditions.     

Transition magnitudes and impact improvement in rubber-modified plastics

Impact strength at room temperature and dynamic mechanical properties over a temperature range have been studied for a number of rubber reinforced glassy state plastics. The rubber phases in every case were butadiene copolymers of known composition and particle size and selected for their good dispersion after blending into the various matrices. This dispersion was checked by electron microscopy and the in situ particle size evaluated. The matrices were based on homo- and co-polymers of styrene, methyl methacrylate and acrylonitrile. A vibrating reed apparatus was employed to measure the storage component of Young's modulus (E′) and loss factor (tan δ) at essentially constant frequency (～300 Hz) through the rubber relaxation region. The Izod impact strength was measured in accordance with the standard method ASTM D-256. A gross parallel was found between impact strength and transition magnitude as measured by the change in modulus between ?100°C and 20°C (ΔE′) or the tan δ peak area with, for example, increasing volume fraction of rubber phase. However, when the same rubber was dispersed in different matrices a more subtle effect was an inverse proportionality of tan δ area with E′ measured at the peak temperature. Conversely ΔE′ after correction for matrix modulus change was shown both theoretically and experimentally to be directly proportional to E′ of the matrix at room temperature. The impact strength actually increases with ΔE′ and not with tan δ area in these cases. However, a more important requirement for good impact is compatibility between the rubber and matrix, but neither ΔE′ nor tan δ reflect this. After correction of tan δ areas to constant matrix modulus there remains an increase of area with particle size. Impact strength also increases strongly with particle size for compatible systems. The applicability of Hashin's central equation and Mackenzie's equation in describing the systems is discussed.     

Preparation of melting‐free poly(lactic acid) by amorphous and crystal crosslinking under UV irradiation

The poly(lactic acid) (PLA) with 3.6% mol of benzophenone (BP) per repeat unit of PLA can be crosslinked to a gel fraction of 98.5% at UV energy of 160 J/cm². From NMR analysis, the photocrosslinking of PLA was attributed to the recombination of primary and tertiary carbon radicals in the repeating units which were generated by the hydrogen abstraction of BP. With increasing crosslinking, melting peak disappeared and glass transition temperature elevated with loss of crystallinity, indicating that the crosslinking occurred in the crystalline region as well as in the amorphous region. The thermal stability of the crosslinked PLA also improved as shown by higher onset temperature as much as 56°C and higher maximum decomposition temperature compared with the pristine PLA. The higher toughness of the crosslinked PLA film was obtained together with the improvement in tensile strength and modulus with increasing crosslinking density. In addition to photocrosslinking of amorphous region, the crosslinking of crystalline region can have significant influence in the improvement of thermal and mechanical properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of nuclear radiations on structure and molecular motions in some crystalline stereoregular polymers

Young's modulus and the mechanical damping factor have been determined between ?180 and +280°C. (at a frequency of several kilocycles), in samples of isotactic polypropylene, isotactic polystyrene, and trans-1,4-polybutadiene, subjected to pile irradiation (γ-rays and neutrons) at γ-doses from 90 to 4000 Mrad. In isotactic polypropylene no important structural changes are produced by the irradiation, except for a partial destruction of crystallinity. The samples receiving high radiation doses exhibit a low temperature loss region, which is attributed to the formation of a certain number of branches. Isotactic polystyrene shows very slight modifications of the dynamic mechanical properties at room temperature. At low temperature an increase of intensity of the δ relaxation phenomenon (probably due to oscillations of phenyl rings) with increasing radiation dose is observed. Important structural modifications produced by the radiation, destruction of crystallinity accompanied by crosslinking, which transform the material into a crosslinked rubber, are observed in trans-1,4-polybutadiene. Unlike conventional (sulfur) vulcanization, crosslinking by radiation does not cause a marked shift of the glass transition point. A secondary low-temperature relaxation effect, not existing in the unirradiated material, appears in the mechanical loss curves of the irradiated samples; it is attributed to the formation of ? CH₂? sequences in the main chains through saturation of C?C bonds. The mechanical spectrum of irradiated polybutadiene is very similar to those shown by crosslinked ethylene–butadiene copolymers.     

Crosslinking characterization of a polyimide: AFR700B

Crosslinking in AFR700B polyimide was studied using several techniques. Crosslinking could not be detected using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Swelling in n-methyl pyrrolidone (NMP) showed network formation occurs at cure temperatures ≥325°C (617°F), but the reaction kinetics could not be determined from the data. Dynamic mechanical analysis (DMA) studies have shown that the storage modulus (G′) increased with increasing cure temperature up to 350°C (662°F), and was constant above 350°C (662°F), indicating that crosslinking via the reverse Diels-Alder reaction was occurring. A broad secondary transition was seen in the loss modulus (G″) curves, centered between 150 and 180°C (302 and 356°F). This secondary transition appeared at a cure temperature of 300°C (572°F) and became more dominant with increasing temperature and time. This secondary transition was not seen for cures <300°C (572°F) when the chains have not crosslinked. Therefore, this is likely due to a crosslink bond rather than one in the backbone. At 1 atm, crosslinking followed second-order kinetics based on the increase in glass transition temperature (T_g). The Arrhenius plot of the rate constant showed a break in the slope, possibly indicating a change in reaction mechanism. At 1.38 MPa (200 psi), the T_g data was too scattered to determine the kinetics.     

Thermal properties of polynorbornene (cis- and trans-) and hydrogenated polynorbornene

Summary The thermal properties of trans-polynorbornene, cis-polynorbornene and hydrogenated polynorbornene were examined and its reversibility tested. Trans-polynorbornene samples, formed in various solvents, exhibit a softening range, from ambient temperature until 375 °C. However, syndiotactic cis-polynorbornene samples show a narrower melting range (between 150 and 375 °C). The fusion enthalpies of cis-polynorbornene samples are around 300-400 J/g. The temperature of decomposition is ca. 456 °C (minimum peak DSC) for trans-polynorbornene and ca. 466 °C, 10 °C higher, for cis-polynorbornene. The solvent used for the polymerization of norbornene has a negligible influence in the melting temperature range or in the decomposition temperature. The treatment with 2,6-di-tert-butyl-4-methyl-phenol during the isolation of polynorbornene leads to materials with different thermal properties. Trans-polynorbornene isolated without 2,6-di-tert-butyl-4-methyl-phenol exhibited an exothermic peak accompanied by an slight increase in weight (1-2%), while samples treated with 2,6-di-tert-butyl-4-methyl-phenol do not show these features.     

Structure and damping properties of polydimethylsiloxane and polymethacrylate sequential interpenetrating polymer networks

By using the technology of the sequential interpenetrating polymer network, a series of novel damping materials based on a polydimethylsiloxane (PDMS)/polyacrylate (PAC) matrix with polymethacrylate (PMAC) were synthesized. They have a controllable broad transition peak spanning the temperature range of 150–220°C and the medial value of loss factor with maximum of 0.35–0.60. Dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and atomic force microscopy (AFM) were applied to analyze and characterize the transition behavior and the microphase structure of the materials. It was found that the size and height of a transition peak at both the low‐ and the high‐temperature zones change as a function not only of the concentration of PMAC and PDMS but also of the kind of PMAC; simultaneously, the low‐ temperature behavior was also governed by the crystallization of PDMS. The content of the crosslinking agent exerts a significant influence on the configuration of the curves of the transition peaks. AFM shows a characteristic phase morphology of double‐phase continuity containing a transition layer and domain less than 1 μm, indicating that the interwoven multilayer networks are the key to incorporation of the immiscible components and form a broad damping functional region. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 545–551, 2002     

Studies of polymeric systems for damping of vibrations in the sonic range

Closed-cell foams based on rigid polyurethanes blended with more viscoelastic polymers possess good vibration-damping properties. The damping characteristics of the various polymers differ, indicating that the chemical nature has an influence on the acoustical performance of the blend. Damping is also temperature dependent. By selection of polymers, foam effective for damping at various service temperatures and over various frequency ranges can be made. The damping characteristics of polymers can be changed by adding fillers. Such methods may be employed to achieve a broader damping peak at the desired service temperature. The damping of vibration of an aluminum strip could be increased by one to two orders of magnitude between 20°C to 60°C when the strip was coated with the experimental materials in comparison with commercial open-cell, elastic foams of comparable density. A dynamic resilience of only 9% was achieved.