EPDM/PP热塑性动态硫化胶的进展

阐述了EPDM／PP共混型热塑性动态硫化胶的发展历史,制备工艺,微观相态结构,性能,加工技术和应用领域。     

低硬度EPDM/PP热塑性动态硫化胶

通过配方调试和工艺条件探索,采用国产双螺杆挤出机对低硬度ＥＰＤＭ／ＰＰ共混型热塑性动态硫化胶的制备工艺进行了研究。在此基础上,阐明了动态硫化速率（促进剂用量）对挤出物橡胶相粒径和交联密度的影响。     

Relaxation behavior of conductive carbon black reinforced EPDM microcellular vulcanizates

Dynamic mechanical analysis and dielectric relaxation spectra of conductive carbon black reinforced microcellular EPDM vulcanizates were used to study the relaxation behavior as a function of temperature (−90 to +100°C) and frequency (0.01–10⁵ Hz). The effect of filler and blowing agent loadings on dynamic mechanical and dielectric relaxation characteristics has been investigated. The effect of filler and blowing agent loadings on glass transition temperature was marginal for all the composites (T_g value was in the range of −39 to −35°C), which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. Strain-dependent dynamical parameters were evaluated at dynamic strain amplitudes of 0.07–5%. The nonlinearity in storage modulus has been explained based on the concept of filler–polymer interaction and interaggregate attraction (filler networking) of carbon black. The variation in real and complex part of impedance with frequency has been studied as a function of filler and blowing agent loading. Additionally, the effect of crosslinking on the dielectric relaxation has also been reported. POLYM. ENG. SCI., 47:984–995, 2007. © 2007 Society of Plastics Engineers     

Separability behavior in viscoelastic properties of EPDM gum vulcanizate

Dynamic mechanical properties of EPDM gum vulcanizates were studied using the dynamic viscoelastometer, Rheovibron. A small sinusoidal strain was superimposed on a static strain and its effect on dynamic mechanical properties were analyzed. The results are discussed in terms of total strain which takes the static strain into account. Separability of time and strain effects for loss modulus and the nonseparability for storage modulus are discussed. A critical strain was identified after which the stress dissipation mechanism changes. © 1994 John Wiley & Sons, Inc.     

Fracture properties of silica/carbon black-filled natural rubber vulcanizates

Crack growth property of natural rubber (NR) vulcanizate with varying silica/carbon black content was examined. Tensile specimen with edge cut was used for estimating fracture properties. All filled NR specimens showed critical cut-size (C _cr ), which is related to abrupt decrease in tensile strength. Carbon black-filled NR, S0 (Si/N330=0/50) has higher tensile strength than equivalently loaded silica-filled NR vulcanizates, S5 (Si/N330=50/0). When the precut size of specimen was less than critical cut-size, tensile strength of S1 (Si/N330=10/40) composition was the highest and that of S5 was the lowest. The critical cut-size passes through a maximum for S2 (Si/N330=20/30) and then decreases gradually with silica loading. An interesting result was that silica and carbon black-blended compounds gave higher critical cut size than the all-carbon black compounds, S0. The inherent flaw size decreased from 246 μm for S0 to 80 μm for S5 as the silica content increased.     

EPDM的压缩永久变形性能研究

研究了硫化体系、填充体系、增塑体系和硫化时间对EPDM高温下压缩永久变形的影响。实验结果表明：在硫黄、过氧化物、酚醛树脂3种硫化体系中,过氧化物配合助交联剂（TAIC）硫化的EP—DM压缩永久变形最小,硫磺硫化体系硫化胶则最大;胶料的压缩永久变形随着炭黑类填料用量的增加而降低,却随着无机类填料用量的增加而增加;填充具有高结构、适当粒径的炭黑（如N550）并适当延长硫化时间能有效降低EPDM的压缩永久变形。     

Comparative study of silica-, nanoclay- and carbon black-filled EPDM rubbers

Silica-, nanoclay-, and carbon black (CB)-filled ethylene–propylene–diene terpolymer (EPDM) mixtures were prepared and subsequently vulcanized. Rheological properties and cure characteristics of the mixtures and mechanical properties of vulcanizates were measured. Rheological property measurements indicated the storage modulus, loss modulus, and complex dynamic viscosity of silica-filled EPDM mixtures were much higher than those of CB-filled EPDM mixtures while tan δ values were lower. The optimum cure time of silica- and nanoclay-filled EPDM mixtures increased with filler loading, whereas the values for CB-filled mixtures slightly decreased with loading. The hardness, modulus, elongation at break, and tensile strength of all the vulcanizates increased with increasing filler loading. The elongation at break of CB-filled EPDM vulcanizates increased insignificantly with CB loading. Among the three fillers, the increase of the tensile strength and elongation at break was most significant for silica-filled EPDM vulcanizates. Remarkably, for 30 phr silica-filled EPDM vulcanizates, a tensile strength and elongation at break of 23.5 MPa and 1045% was achieved, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Characterization of the deformation behavior of dynamic vulcanizates by FTIR spectroscopy

To clarify the deformation mechanisms and to improve the mechanical properties of dynamic vulcanizates, we studied their deformation behavior by Fourier‐transform infrared (FTIR) spectroscopy. It was found that the orientation in the dispersed phase (EPDM phase) is higher than in the matrix (PP phase) upon loading. The orientation of the rubber phase increases continuously. In the thermoplastic phase, a change of the deformation mechanism takes place. With respect to the total strain of the material, the orientation in the thermoplastic phase of the dynamic vulcanizates is lower, and in the elastic phase, it is higher than the corresponding orientation of the pure components. During stress relaxation, there is an increase of the orientation in the crystalline PP phase. Simultaneously, a decrease of the orientation in the EPDM phase is observed. Upon unloading, the orientation recovery in the EPDM phase is always complete, while the orientation recovery in the PP phase is reversible only at low strains. The critical point, where the elastic deformation gets lost, corresponds to the minimum in the orientation function curve. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 148–158, 2001     

Aspects of the thermal and dynamic mechanical behavior of EPDM rubbers

The influence of both ethylene content and the degree of crystallinity on the thermal and dynamic mechanical properties of certain commercial EPDM rubbers were investigated using the TMA, DSC, and Rheovibron techniques. The six materials chosen for this study were Nordel 1560, Intolan 260, Royalene 1812, Vistolan 3708, Intolan 255, and Keltan 778.     

Effects of blend composition and dynamic vulcanization on the morphology and dynamic viscoelastic properties of PP/EPDM blends

The morphology and dynamic viscoelastic properties of isotactic polypropylene (PP) blended with oil-free/oil-extended ethylene–propylene–diene (EPDM) rubbers were studied. Unvulcanized and dynamically vulcanized blends with the compositions PP/EPDM = 50/50 and = 30/70 were investigated. The morphology was observed by phase contrasted atomic force microscopy. The dynamic viscoelastic properties were determined with a rheometer of plate–plate configuration. It was shown that the rheological behavior was strongly affected by both the composition and the morphology of the blends. Significant improvement in the flowability of the dynamically vulcanized blends was observed when oil-extended EPDM was used instead of the oil-free version. It was demonstrated that the rheological properties are mostly controlled by the elastomer phase at low frequencies, while in the high-frequency range the influence of PP becomes dominant. The peculiarities in the rheological behavior of the thermoplastic elastomers (uncured blends, TPE) and thermoplastic dynamic vulcanizates (TPV, dynamically cured blends) containing oil-extended EPDMs were traced to a limited compatibility between the PP and EPDM components in the melt. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of hot‐air aging and dynamic fatigue on the structure and dynamic viscoelastic properties of unfilled natural rubber vulcanizates

The effects of hot‐air aging and dynamic tensile fatigue on the network structure and dynamic viscoelastic properties of unfilled natural rubber (NR) vulcanizates were investigated with magnetic resonance crosslink density spectrometry, Fourier transform infrared spectroscopy/attenuated total reflection (FTIR–ATR), and dynamic mechanical analysis. The results showed that there was a carbonyl weak absorption peak at 1723 cm^?1 in the FTIR–ATR spectra of unfilled NR vulcanizates after hot‐air aging; The crosslink density decreased continuously as the aging time increased. The dynamic modulus of an aged specimen declined considerably, and the value of tan δ after 72 h of aging greatly increased. There was a large difference in the FTIR–ATR spectra of unfilled NR vulcanizates before and after tensile fatigue. The peaks at 1597, 1415, and 1015 cm^?1 increased concurrently with the tensile fatigue time. Initial analysis suggested that structures such as conjugated dienes appeared in the network structure. The modulus declined sharply, whereas the value of tan δ increased noticeably, after tensile fatigue. The effects of hot‐air aging and tensile fatigue on the crosslink density and FTIR–ATR spectra of unfilled NR vulcanizates were different, but both affected the viscoelastic properties dramatically. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

AC conductivity and positive temperature coefficient effect in microcellular EPDM vulcanizates

Dielectric relaxation spectra of conductive carbon black reinforced microcellular EPDM vulcanizates were used to study their relaxation behavior in the frequency range of 0.01–10⁵ Hz over a wide range of temperature from 30 to 120°C. The effect of variation in filler loading and blowing agent loading (density) on dielectric characteristics such as impedance, dielectric constant, and conductivity has been studied. The experimental results show that the relative dielectric permittivity of the composites depends strongly on the extent of carbon black and blowing agent concentrations. The frequency dependence of AC conductivity has been investigated by using Percolation theory. The permittivity and conductivity of the microcellular composites have been analyzed based on scaling theory at increasing temperatures. The applicability of Lichtenecker‐Rother's “rule of mixture” to describe the complex permittivity of the composite has also been investigated. Irrespective of the blowing agent loading and temperature, the percolation threshold as studied by DC conductivity was found to be at 40 phr loading of the filler. Scanning electron microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

PP/EPDM共混物结晶及动态流变行为研究

以聚丙烯、EPDM为原料,采用熔融共混法制备了PP/EPDM复合材料。通过XRD、偏光显微镜和旋转流变仪等检测手段,研究EPDM含量对PP/EPDM共混物结晶及动态流变行为的影响。结果表明,EPDM显著提高了共混物的冲击强度,但拉伸强度与弯曲强度明显降低。其中,当EPDM质量分数为10%时,共混物的冲击强度为58.156kJ/m2,较PP提高了约20倍;随着EPDM含量的增加,共混物的球晶结构受到不同程度破坏,当EPDM质量分数为25%时,球晶结构破坏严重。同时,随着EPDM含量的增加,共混物的结晶温度降低。PP/EPDM熔体的复数黏度均随着角频率的增加而下降,表现为剪切变稀现象,材料为假塑性流体,EPDM的加入使得共混物的弹性模量和黏性模量增大。     

Preparation and properties of carbon black filled EPDM/POE thermaplastic vulcanizates

TPVs filled with different amounts (0–50 phr) of carbon black were prepared via melt mixing by dynamic vulcanization in Haake plasticorder at 150°C and 40rpm and then the properties of them were studied. Torque-time curves showed that the curing degree reached a biggest value at 10 phr and then decreased with the increase of filling content while the curing rate was always rising. Mechanical properties such as tensile strength, tear strength, modulus as well as hardness increased with the increment of carbon black content while the tension set at break was reduced dramatically. Two phase morphology was observed by SEM photographs and the effect of carbon black on curing extent was testified. To illuminate the effect of carbon black, curometer curves and carbon black dispersion pictures were also analyzed. Rubber processing analyzer (RPA) experiments proved that there was a progressive nonlinear behavior, which was more and more clearly expressed with the increment of carbon black content and could be explained via the Payne effect. But the TPVs containing highest carbon black exhibited the fastest drop of G′ with increasing strain amplitude as obtained from the value of G₀′ − G_∞′. The order of tanδ at different carbon black content was tanδ (10 phr) < tanδ (0 phr) < tanδ (30 phr) < tanδ (50 phr) at lower strain amplitude. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Dielectric relaxation of Ensaco®350G reinforced microcellular EPDM vulcanizates

The dielectric relaxation characteristics of microcellular EPDM vulcanizates has been studied as a function of variation in filler and blowing agent loadings in the frequency range of 100–10⁶ Hz. The dielectric constant ε′ increases with increasing filler loadings at all frequencies. This has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium. The effect of variation in filler and blowing agent loadings on the complex and real parts of impedance was distinctly visible. Which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. The phenomenon of percolation in the composites has been discussed based on the measured changes in electric conductivity and morphology of composites at different concentrations of the filler. The percolation threshold as studied by DC conductivity occurred near 40 phr of filler loading. SEM microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. POLYM. COMPOS., 28: 657–666, 2007. © 2007 Society of Plastics Engineers     

Recycling of ethylene propylene diene monomer (EPDM) waste. III. Processability of EPDM rubber compound containing ground EPDM vulcanizates

The rheological behavior of ethylene propylene diene monomer (EPDM) compounds containing ground EPDM waste (W‐EPDM) of known composition was studied by using a Monsanto processability tester in a temperature range of 90–110°C and a shear rate range of 306.7–1533.24 s^?1. It is found that the shear viscosity decreases slightly with increasing W‐EPDM loading because of wall slip that results from the migration of lubricants from the W‐EPDM. The addition of W‐EPDM to raw EPDM results in a decreased die swell at all temperatures and shear rates. SEM photomicrographs of the EPDM extrudate surface show improved surface smoothness and reduced extrudate distortion when EPDM is blended with W‐EPDM. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2204–2215, 2003     

Preparation and characterization of PPRC/EPDM thermoplastic vulcanizates: A comparative study

Thermoplastic vulcanizates (TPVs) of polypropylene random copolymer (PPRC) with ethylene–propylene diene monomer rubber (EPDM) were prepared through in situ and ex situ compatibilization techniques. Silanized silica as nanofiller was incorporated in the ex situ compatibilized TPVs. Mechanical properties were measured for different formulated TPVs with increasing loading of EPDM from 10 to 30 phr. A comparative data is generated to discuss the effect of two compatibilization techniques and addition of silica filler in the TPVs. The degradation studies were also carried out to check the stability of the blends under harsh ultraviolet environment. The in situ compatibilized TPVs provided better overall mechanical properties. Moreover, it is worth mentioning that the properties of ex situ compatiblized TPVs were enhanced by incorporation of silanized silica filler. Silanized silica filler helped in reducing the die swell significantly. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46726.     

Morphology and viscoelastic behavior of silicone rubber/EPDM/Cloisite 15A nanocomposites based on Maxwell model

Blends of silicone rubber (SR) and ethylene propylene diene monomer (EPDM) are immiscible due to different polarity and poor interfacial surface tension between their rubber chains. In this study, compatibilizing effect of a nanoclay addition in SR/EPDM blends was investigated. Viscoelasticity and morphology of nanocomposites based on SR and EPDM, containing 10, 20 and 30 wt% of EPDM and 3, 6 and 9 phr of nanoclay (Cloisite 15A), were studied. The curing behavior of the samples showed that the vulcanization rate and cross-link density of the blends increased with increases in SR content. Morphological study was conducted by XRD, SEM and EDX analyses and they indicated that the nanoparticles tended to disperse in the EPDM phase and consequently caused hardness and the elasticity of this phase in nanocomposites increased. Tensile properties of the samples showed a good fitting between that of experiments and the Maxwell model at initial time of testing (1.5 s) for all the blends. Sample parameters including modulus (E), viscosity (η) and relaxation time (τ) calculated by the Maxwell model revealed that those samples with higher content of nanoparticles exhibit higher modulus and lower relaxation time. The good match in tensile properties based on Maxwell model and those of the experimental data was attributed to good dispersion of nanoclay in the blends.     

Adhesion strength and fracture behavior between carbon black-filled rubber sheets

Adhesion behavior at the interface between a partially-crosslinked and a fully-crosslinked sheet of carbon black-filled rubber compound was investigated over a temperature range from 30 to 120°C. The values of adhesion fracture energy G_a were compared with those of cohesive tear energy G_c. A considerable chemical, as well as physical, interfacial bonding is formed when the uncrosslinked or partially-crosslinked sheet is crosslinked in contact with even a fully-crosslinked sheet. However, there is only a small possibility of chemical bonding when the two fully-crosslinked rubber layers are again crosslinked in contact with each other. An interesting failure mode, termed 'interfacial knotty tearing' was found for a strain-induced crystallizable natural rubber.     

Effect of fillers and vulcanizing systems on the physicomechanical and electrical properties of EPDM vulcanizates

The physicomechanical and dielectric properties were investigated for ethylene propylene diene terpolymer (EPDM) rubber loaded with different white fillers, namely, kaolin, quartz, polyvinylchloride PVC, and talc. The white fillers were added at a fixed level of 20 phr. Two vulcanizing systems were used, tetramethyl thiuram disulfide (TMTD) and sulfur/N-cyclohexyl-2-benzothiazyl sulfenamide (S/CBS). It was found that the curing systems affect the dielectric properties more than the filler type. The effect of the curing system and type of filler on the physicomechanical properties before and after thermal aging were also investigated, and the data obtained were interpreted.