Blends Of Ethylene-propylene Rubber Research Articles

Melt rheology and morphology of uncompatibilized and in situ compatibilized nylon‐6/ethylene propylene rubber blends

AbstractMelt rheology and morphology of nylon‐6/ethylene propylene rubber (EPR) blends were studied as a function of composition, temperature, and compatibilizer loading. Uncompatibilized blends with higher nylon‐6 content (N90 and N95) and rubber content (N5 and N10) had viscosities approximately intermediate between those of the component polymers. A very clear negative deviation was observed in the viscosity–composition curve over the entire shear rate range studied for blends having composition N30, N50, and N70. This was associated with the interlayer slip resulting from the high‐level incompatibility between the component polymers. The lack of compatibility was confirmed by fracture surface morphology, given that the dispersed domains showed no sign of adhesion to the matrix. The phase morphology studies indicated that EPR was dispersed as spherical inclusions in the nylon matrix up to 30 wt % of its concentration. A cocontinuous morphology was observed between 30 and 50 wt % nylon and a phase inversion beyond 70 wt % nylon. Various models based on viscosity ratios were used to predict the region of phase inversion. Experiments were also carried out on in situ compatibilization using maleic anhydride–modified EPR (EPR‐g‐MA). In this reactive compatibilization strategy, the maleic anhydride groups of modified EPR reacted with the amino end groups of nylon. This reaction produced a graft copolymer at the blend interface, which in fact acted as the compatibilizer. The viscosity of the blend was found to increase when a few percent of modified EPR was added; at higher concentrations the viscosity leveled off, indicating a high level of interaction at the interface. Morphological investigations indicated that the size of the dispersed phase initially decreased when a few percent of the graft copolymer was added followed by a clear leveling off at higher concentration. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 252–264, 2004

Interphase layer formation in isotactic polypropylene/ethylene–propylene rubber blends

AbstractThe influence of the interphase layer, formed by the introduction of an oil in ethylene–propylene rubber (EPR), on the structure and properties of isotactic polypropylene (iPP)/EPR blends was studied. The dispersity of the rubber phase in the iPP matrix did not depend on presence of oil. The melting temperature of iPP decreased with increasing content of oil‐extended EPR, and it did not change if the oil was absent. The compatibility parameter was determined from the dependency of the iPP melting point on the rubber content with the Nishi–Wang equation. A negative value of the parameter indicated a limited compatibility of iPP with oil‐extended EPR. The latter also reduced the temperature and heat of crystallization of iPP. The mechanical properties of iPP/EPR blends were investigated as functions of temperature and elongation rate. It appeared that elastic modulus and yield stress of the blends linearly depended on the logarithm of the elongation rate. Activation volumes, calculated with the Eyring equation, increased with increasing content of elastomer; moreover, this increase was more pronounced for the oil‐extended elastomer. It is suggested that the oil influenced the structure of the interphase layer and, accordingly, the characteristics of the iPP/EPR blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 249–257, 2003

SELF REINFORCING COMPOSITE BASED ON EPR/LCP BLEND

Blends of ethylene propylene rubber (EPR) and thermotropic liquid crystalline polymer (TLCP) have been prepared by melt-mixing technique. Processing studies indicated the decrease in the viscosity of the blends with the addition of LCP. The mechanical properties like tensile strength and modulus increased up to 10% of LCP and then decreased. The crystallinity increased with an increase in the LCP content. At higher levels of LCP, crystal growth is favored. Thermal studies indicated the endothermic signals that were more prominent at all the peak temperatures. The surface degradation increases with an increase in elastomer (EPR) content in the blend. The relaxation phenomena, as observed from Dynamic Mechanical Thermal Analysis (DMTA) analysis, are changing depending on the blend ratio. The dynamic modulus and stiffness increased with the addition of LCP in the blend. Under dynamic application, at higher levels of LCP, it was observed from scanning electron microscope that there were no cracks at the interface between the EPR and the glass fibers suggesting the better wetting of the fibers by the EPR.

Hybrid PP–EPR–GF composites. Part 1 – Deformation mechanisms

The modification of polypropylene (PP) with a combination of ethylene/propylene rubber (EPR) and glass fibres (GF) is a well known route to improving its mechanical properties. This is because the reductions in stiffness and strength due to the presence of rubber particles are more than compensated by the addition of short glass fibres. This study has focused on the combined effects of glass fibres and rubber particles on the mechanical properties and mechanisms of deformation in PP–EPR–GF hybrid composites. Several composites with different amounts of rubber and short glass fibres were examined. To study possible synergistic effects, the total combined weight fraction of rubber and fibres was kept constant at 20%. The results of tensile tests show that the addition of glass fibres to PP–EPR blends promotes yield strength and modulus while reducing elongation at break. Optical microscopy shows that, in the damage zones of all specimens, deformation bands, which appear similar to crazes, are visible after stretching. Scanning electron microscopy shows crazelike features including some voids, which tend to deviate from in plane propagation near the ends of glass fibres. The dominant mechanism of deformation in PP–EPR–GF observed in this work appears to be a crazelike type of damage, which is believed to be highly localised dilatational shear banding, propagating via repeated cavitation.

Molecular transport of aromatic hydrocarbons through nylon-6/ethylene propylene rubber blends: Relationship between phase morphology and transport characteristics

Molecular transport of aromatic hydrocarbons through nylon/ethylene propylene rubber (EPR) blend has been investigated in the temperature range of 25 to 65 °C. The effect of blend ratio on the transport behavior was studied in detail. Nylon/EPR-50/50 blend shows the lowest uptake among all the systems studied. This behavior is related to blend morphology, density, and crystallinity of the blend composition. The transport property was correlated with the extent of interfacial adhesion in the blends. The effects of temperature and penetrant size on the sorption behavior were examined. Thermodynamic and Arrhenius parameters were evaluated from the diffusion data. Theoretical and experimental diffusion results were compared.

Nylon 6/ethylene propylene rubber (EPM) blends: Phase morphology development during processing and comparison with literature data

The morphology of immiscible blends of nylon 6 and ethylene propylene rubber blends (EPM) was studied. The blends were prepared by melt blending in a twin-screw miniextruder and a Haake Rheocord mixer. The influence of the blend ratio, time of mixing, rotation speed of the rotors, mixing temperature, and quenching of the extruded melt at low temperature on the phase morphology of the blends was quantitatively analyzed. The morphology was examined by scanning electron microscopy (SEM) after preferential extraction of the minor phase. The SEM micrographs were quantitatively analyzed for domain-size measurements. The morphology of the blends indicated that the EPM phase was preferentially dispersed as domains in the continuous nylon matrix up to 40 wt % of its concentration. A cocontinuous morphology was observed at 50 and 60 wt % EPM content followed by a phase inversion beyond 60 wt % of EPM where the nylon phase was dispersed as domains in the continuous EPM phase. The size, shape, and distribution of the domains were evaluated by image analysis as a function of the blend composition. The effect of the time of mixing on the phase morphology was studied up to 20 min for the 30/70 EPM/nylon blend. The most significant domain breakup was observed within the first 3 min of mixing followed by a leveling off up to 15 min. This may be associated with the equilibrium between the domain breakup and coalescence. The influence of rotor speed on the morphology was insignificant at a high rotor speed although a significant effect was observed by changing the rotor speed from 9 to 20 rpm. The influence of high-temperature annealing, repeated cycles of extrusion, the molecular weight of the nylon matrix, and the nature of the mixer type (twin-screw miniextruder versus Haake Rheocord mixer) on the morphology was also investigated in detail. The experimental results were compared with literature data. Finally, the extent of interface adhesion in these blends was analyzed by examination of the fracture-surface morphology. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1405–1429, 1999

Relationships between Morphology and Brittle Temperatures of Polypropylene / Ethylene-Propylene Rubber Blends.

Morphology and brittle temperatures of seven Polypropylene(PP)/Ethylene-Propylene rubber (EPR) blends were investigated. Sizes and interparticle distances for dispersed EPR particles were measured. EPR concentrations in PP matrix phases were also evaluated. Based on these results and brittle temperatures for the blends, molecular mechanism of brittleductile transition for PP/EPR blend was discussed.

ナノ・オーダーで高次構造が制御されたスーパー・オレフィンポリマーに関する研究 第１報 ポリプロピレン／エチレンプロピレンゴム系ポリマーブレンドの力学的特性とモルフォロジーの関係

従来, 自動車用バンパーなどには, 耐衝撃性ポリプロピレンにエチレンプロピレンゴム (EPR) が20～30wt%添加された材料が広く使用されている. この種の材料においては, その量比からポリプロピレン (PP) の海にEPRが島として存在するとする考え方が定説であった. しかし, そのような考え方では物性の解釈が困難な場合があり, 今回, 高分解能電子顕微鏡観察, 粘弾性解析, パルスNMRなどにより詳細な構造解析を実施した. その結果, EPRの一部とPP非晶部とが相互溶解して一体となりエラストマ-化するとともに, 三次元的に連結しているEPR相が存在することがわかった. 結論として, この種の材料の構造は従来の定説であるPPマトリックスにEPRが分散する構造ではなく, PP非晶相とエラストマーから成るマトリックス中にPP結晶ラメラが分散する構造であること, および, その構造モデルによって, 従来は説明困難であった物性の解釈が可能となることが判明した.

Polyolefin Thermoplastic Elastomer Blends

Abstract Thermoplastic elastomers based on blends of polyolefins are an important family of engineering materials. Their importance arises from a combination of rubbery properties along with their thermoplastic nature in contrast to thermoset elastomers. The development of polyolefin thermoplastic elastomer blends follows somewhat that of thermoplastic elastomers based on block copolymers such as styrene-butadiene-styrene triblock copolymer and multisegmented polyurethane thermoplastic elastomers which were instrumental in showing the utility of thermoplastic processing methods. Polyoleflns are based on coordination catalysts that do not easily lend themselves to block or multisegmented copolymer synthesis. However, since polyolefins have many important attributes favorable to useful elastomeric systems, there was considerable incentive to produce thermoplastic elastomers based on simple α-olefins by some means. Low density, chemical stability, weather resistance, and ability to accept compounding ingredients without compromising physical properties are highly desirable. These considerations led to the development of polyolefin thermoplastic elastomer blends, and two types are now widely used: blends of ethylene-propylene rubber (EPM) with polypropylene (PP) and blends of EPDM and PP in which the rubber phase is highly crosslinked. This article reviews the nature of these blends. Both physical and Theological properties are very dependent on the morphology and crosslink density of the blend system. Moreover, the usefulness of practical systems depends extensively on compounding technology based on added plasticizers and fillers.

New Power Cable Insulations Based on Covulcanized Blends of Ethylene Propylene Rubber and Polyethylene

New power cable insulations based on covulcanized blends of ethylene propylene rubber (EPR) and polyethylene (PE) have been developed. These heat-, water-, ozone-, and highly corona-resistant insulations combine many of the desirable properties of both ethylene propylene rubber and polyethylene. Specific constructions of low-voltage, heat and moisture resistant power cables, aerial spacer cables, and portable power cables are reviewed and compared with existing constructions. It is felt that, compared to rubber insulated cables, the use of these new insulations can result in smaller diameter cables which exhibit many improved properties over thermoplastic or cross-linked polyethylene cables.