Tensile properties and morphology of the dynamically cured EPDM and PP/HDPE ternary blends

The tensile properties and morphology of the polyolefin ternary blends of ethylenepropylene–diene terpolymer (EPDM), polypropylene and high density polyethylene were studied. Blends were prepared in a laboratory internal mixer where EPDM was cured in the presence of PP and HDPE under shear with dicumyl peroxide (DCP). For comparison, blends were also prepared from EPDM which was dynamically cured alone and blended with PP and HDPE later (cure–blend). The effect of DCP concentration, intensity of the shear mixing, and rubber/plastics composition was studied. The tensile strength and modulus increased with increasing DCP concentration in the blends of EPDM-rich compositions but decreased with increasing DCP concentration in blends of PP-rich compositions. In the morphological analysis by scanning electron microscopy (SEM), the small amount of EPDM acted as a compatibilizer to HDPE and PP. It was also revealed that the dynamic curing process could reduce the domain size of the crosslinked EPDM phase. When the EPDM forms the matrix, the phase separation effect becomes dominant between the EPDM matrix and PP or HDPE domain due to the crosslinking in the matrix.     

Rheological properties and crystalline structure of the dynamically cured EPDM and PP/HDPE ternary blends

The rheological properties and crystalline structure of the polyolefin ternary blends of EPDM/polypropylene/high density polyethylene were studied. Blends were prepared in a laboratory internal mixer by two different methods. In blend–cure process, blending and curing were performed simultaneously and EPDM was cured by dicumyl peroxide (DCP) in the presence of PP/HDPE under shear. The cure–blend was to cure EPDM alone first under shear (dynamic curing) and then mix the cured EPDM with PP and HDPE. The effect of DCP concentration, intensity of the shear mixing, and the rubber/plastic composition were studied using capillary rheometer and X-ray diffractometer. The PP-rich ternary blends showed the effect of the mechanooxidative degradation of PP by shear and peroxide. The melt viscosity increased with increasing DCP concentration in blends of EPDM-rich compositions. X-ray diffraction studies revealed that the inclusion of 25 wt % of linear EPDM in the PP/HDPE mixture for the PP-rich ternary blends changed the crystal structure of polypropylene component in the ternary blends. However, the dynamic curing did not alter the crystal structure of PP or HDPE in the blends.     

Morphology and properties of PP/EPDM binary blends and PP/EPDM/nano‐CaCO3 ternary blends

In this article, the morphology, crystallization, and rheological behaviors of polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) binary blend and PP/EPDM/calcium carbonate nanoparticles (nano‐CaCO₃) ternary blend were investigated. Two processing methods, i.e., direct extrusion and two‐step extrusion, were employed to prepare the PP/EPDM/CaCO₃ blend. The influence of EPDM and nano‐CaCO₃ respectively on phase morphology and properties of PP/EPDM blend and PP/EPDM/CaCO₃ blend were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and dynamic rheometer. The crystallinity and crystallization temperature of PP/EPDM blend were improved in comparison to pure PP due to addition of EPDM, but kept invariable with the increased EPDM loading. As the EPDM content was increased, the mobility of PP molecular chains was weakened. Compared with direct extruded blend, less and finer nano‐CaCO₃ was dispersed in matrix of two‐step extruded blend. Accordingly, the increased nano‐CaCO₃ in matrix gave rise to a weaker increment in crystallinity and crystallization temperature of two‐step extruded blend, and a later platform of tanδ curve. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Tensile properties and morphology of PP/EPDM/glass bead ternary composites

The tensile properties of three types of injection molded glass bead (GB) filled polypropylene (PP)/ethylene-propylene-diene monomer (EPDM) ternary composites have been determined at room temperature by using an Instron materials testing machine. The effects of the filler surface treatment, the glass bead (GBI) pretreated with a silane coupling agent and the EPDM (EPDM-MA) modified with a maleic anhydride, and the filler content on the tensile mechanical properties of the ternary PP composites have been investigated. The Young's modulus (E_c) increases while the yield stress (σ_yc) and tensile fracture strength (σ_bc) of the composites decrease with increasing the volume fraction of glass beads (ϕ_g) when the volume fraction of EPDM is constant (ϕ_e = 10%). The (E_c) values of PP/EPDM/GBI and ϵ_bc for PP/EPDM-MA/GB2 (no surface pretreated) systems are the highest at the same ϕ_g. The tensile fracture energy (E_bc) and tensile fracture strain (ϵ_bc) of PP/EPDM/GBI and PP/EPDM/GB2 systems appear to peak at ϕ_g = 25%. However, the E_bc and ϵ_bc of PP/EPDM-MA/GB2 system show little changes with increasing ϕ_g. The fracture surfaces of ternary composites have been examined in a scanning electron microscope. The correlation between the tensile properties and morphologies of these materials have been discussed.     

Rheological properties and compatibility of NR/EPDM and NR/brominated EPDM blends

Ethylene–propylene–diene terpolymer (EPDM) was modified by bromination reaction. Blending the resulting brominated EPDM with natural rubber (STR5L) and blending the unmodified EPDM with STR5L at various compositions were carried out. The rheological properties of the blends were investigated using a capillary extrusion. Shear flow curves of the pure rubbers and their blends illustrated the pseudoplastic property as shear thinning behavior with a power law index n < 1. True shear viscosity of all blends showed the negative deviation in relation to their additive values. Rheological behavior and two T_g's found from the DSC thermograms at all blend compositions indicated blend incompatibility for both sets of blends. The incompatibility of the vulcanized blends was also found by measuring the spin–spin relaxation time T₂ by pulsed NMR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 837–847, 2003     

Structure and properties of dynamically cured EPDM/PP blends

The structure and properties of polyolefin blends of ethylene–propylene–diene terpolymer (EPDM) and polypropylene were studied. Blends were prepared in a laboratory internal mixer where EPDM was cured with PP under shear with dicumyl peroxide (DCP) at different shear conditions (blend–cure). Blends were also prepared for comparison from EPDM which were dynamically cured in the absence of PP and blended later (cure–blend). The effect of DCP concentration, intensity of the shear mixing, and rubber/plastic composition were studied. In blend–cure, the melt viscosity increased with increasing DCP concentration in blends of 75% EPDM and 25% PP, but it decreased with increasing DCP concentration in blends of 75% PP and 25% EPDM. In cure–blend, however, the melt viscosity increased with increasing DCP concentration for all compositions. The melt viscosity decreased with increasing intensity of the shear mixing presumably due to the formation of the smaller segregated microdomain of the crosslinked EPDM gels in both blend–cure and cure–blend materials. The crystallization rate was higher in EPDM/PP blends than in PP homopolymer. The crystallization rates for various blending conditions were also compared.     

动态硫化PP/EPDM共混物的结构与性能

研究了动态硫化和直接共混对聚丙烯／三元乙丙橡胶共混物的力学性能、流动性能和形态结构的影响。结果表明：过氧化二异丙苯（DCP）的加入,使动态硫化和直接共混2种方法制备的共混物的熔体流动速率（MFR）增大,但直接共混的共混物的MFR较动态硫化共混物高。动态硫化共混物的粒径尺寸较直接共混物小,且分布均匀。动态硫化后的共混物中两组分的玻璃化转变温峰接近。DCP的加入使动态硫化共混物的缺口冲击强度明显高于直接共混的共混物。     

Processability and mechanical properties of ternary composites PP/EPDM/GF

The enhancement of the mechanical properties of neat PP is achieved by the addition of glass fibers and EPDM rubber. The Young's modulus and notched Charpy impact strength of the composites obtained are improved with respect to the original polymer, leading to a new composite material with a very good balance of toughness and rigidity properties. The tensile behavior of these multiphase systems is successfully compared with theoretical predictions using the Halpin‐Tsai/Nielsen theory for uniaxially short fiber composites, which considers the matrix as a blend with spherical particles and can predict the tensile modulus considering an average fiber orientation angle. An accurate morphological study performed by scanning electron microscopy (SEM) shows a very good dispersion of the rubbery phase into the neat matrix. No special affinity between the rubber and the fibers is reported. The good dispersion and the small particle diameter indicate the good processability of the ternary systems studied.     

反应性聚丙烯/三元乙丙橡胶共混物的流变性能研究

采用高压毛细管流变仪 ,研究了EPDM含量、交联剂、交联助剂等因素对反应性PP/EPDM共混物性能的影响。结果表明 ,EPDM分散相浓度为 2 0～ 2 5phr,反应共混工艺对体系的消缠降粘效果显著 ;交联剂A的含量越高 ,体系表观粘度越小 ,但粘度对剪切的响应不敏感 ;交联剂B和并用交联剂S可抑制PP降解 ,进一步优化材料力学性能 ,并仍保持体系加工流动性高于简单共混PP/EPDM。     

Radiation processing of EPDM/PP blends

The effect of ionizing radiation on thermal oxidation of ethylene-propylene copolymer/polypropylene (EPDM/PP) was evaluated over the range of total gamma doses up to 250 kGy. The influence of irradiation dose on oxidation induction periods was investigated by oxygen uptake and thermal analysis on polymer samples containing various concentrations of components (100/0, 80/20, 40/60, 60/40, 20/80 and 100/0 w/w ). Drastic decrease in oxidation induction time was observed for low doses. The competition between crosslinking and scission has been examined on the basis of radical recombination on post-irradiation time. The influence of specimen formulations on oxidation induction time is discussed regarding to the contribution of antagonistic processes: crosslinking and oxidative degradation.     

交联剂对动态硫化PP／EPDM中PP晶体及EPDM形态结构的影响

针对ＰＰ／ＥＰＤＭ动态硫化中有机过氧化物交联剂Ａ用量对试样拉伸,弯曲和冲击等性能所产生的较大的影响,采用偏光显微镜研究了不同交联剂Ａ用量下动态硫化ＰＰ／ＥＰＤＭ中连续相ＰＰ的晶体结构和分散相ＥＰＤＭ的形态结构特征。     

Mechanical properties and structural characteristics of dynamically photocrosslinked PP/EPDM blends

The mechanical properties and crystal morphological structures of dynamically photocrosslinked polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) blends have been studied by mechanical tests, wide‐angle X‐ray diffraction (WAXD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Dynamically photocrosslinking of PP/EPDM blends can improve the mechanical propertiess considerably, especially the notched Izod impact strength at low temperature. Data obtained from mechanical tests show that the notched Izod impact strength of a dynamically photocrosslinked sample with 30% EPDM at ?20°C is about six times that of an uncrosslinked sample with the same EPDM component. The results from the WAXD, SEM, and DSC measurements reveal the enhanced mechanism of impact strength for the dynamically photocrosslinked PP/EPDM blends as follows: (i) the β‐type crystal structure of PP is formed and the interplanar distance of β‐type crystal increases slightly with an increase in the EPDM component; (ii) the droplet size of the EPDM phase in the photocrosslinked PP/EPDM blends is obviously reduced and the droplet number is increased with an increase in the EPDM component during the dynamical photocrosslinking process; (iii) the graft copolymer of PP‐g‐EPDM is formed at the interface between PP and EPDM components. All the above changes from the crystal morphological structures are favorable for increasing the compatibility and enhancing the toughness of PP/EPDM blends at low temperatures.     

Effect of reactive compatibilisation on the phase morphology and tensile properties of PA12/PP blends

Both uncompatibilized and compatibilized blends based on polyamide 12 (PA12) and isotactic polypropylene (PP) were prepared in a Brabender Plastograph®. The compatibiliser used was maleic anhydride functionalized polypropylene (PP‐g‐MA). Phase morphology of the blends was inspected in scanning electron microscope (SEM) on cryogenically fractured etched surfaces of the specimens. PA12/PP blends possessed a nonuniform and unstable morphology owing to the incompatibility between their constituents. Addition of compatibiliser improved the interfacial characteristics of the blends by retarding the rate of coalescence. So, the phase morphology became more fine, uniform, and stable. Tensile properties of both uncompatibilized and compatibilized blends were measured as a function of blend composition and compatibiliser concentration. Uncompatibilized blends displayed inferior mechanical properties to compatibilized ones; especially for those containing 40–60 wt % of PP. Reactive compatibilisation of blends was found to be efficient and improved the tensile strength of the blends considerably. Addition of PP‐g‐MA improved the interfacial adhesion, decreased the interfacial tension, and thereby, enhanced the tensile strength by 85%. Finally, various models were adopted to describe the tensile strength of the blends. The experimental data exhibited a reasonably good fit with Nielsen's first power law model. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Dynamic rheological properties of binary PP/PA and ternary PP/PA/GF blends

The dynamic rheological behavior was investigated for binary polypropylene (PP) - polyamide-6 (PA-6) and ternary PP-PA-6-glass fiber (GF) blends. The observed trends are related to the blend morphology and the partitioning of the GF within the three component blends. The dynamic and shear viscosity results show a good overlap for the PP homopolymer, within the shear rates studied. The addition of PA-6 and/or glass fibers to the PP causes significant deviations between the two rheological behaviors. This reflects the fibrillation of PA-6 and the orientation of glass fibers during shear rheometry, which reduce the blends' shear viscosity. The effect of PA-6 content on dynamic viscosity is less significant than for shear viscosity, owing to the absence of morphological structuring. The addition of PA-6 to PP increased the principal relaxation time of the binary blends. The addition of GF to these binary blends gave a further increase in the principal relaxation time.     

Crystallization of PP in PP/SEBS blends and its correlation with tensile properties

Crystallization of polypropylene (PP) in the blends of PP with styrene–ethylene butylene–styrene triblock copolymer (SEBS) is studied through differential thermal analysis (DTA) and X-ray diffraction measurements. Analysis of crystallization exotherm peaks in terms of crystallization nucleation and growth rates, crystallite size distribution, and crystallinity revealed differences in the morphology of PP component in the blend in the different regions of blend composition. Crystallinity determined by X-ray diffraction and DTA showed identical variations with blend composition. Variations in tensile properties of these blends with blend composition are also reported. Correlations of the various tensile properties with the crystallization parameters, viz., the crystallinity and crystallite size distribution, are presented, which confirm the influence of crystallization of PP component on the tensile properties of these blends.     

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     

Mechanical properties,morphological structure,and thermal behavior of dynamically photocrosslinked PP/EPDM blends

A dynamically photocrosslinked polypropylene (PP)/ethylene–propylene–diene (EPDM) rubber thermoplastic elastomer was prepared by simultaneously exposing the elastomer to UV light while melt‐mixing in the presence of a photoinitiator as well as a crosslinking agent. The effects of dynamic photocrosslinking and blend composition on the mechanical properties, morphological structure, and thermal behavior of PP/EPDM blends were investigated. The results showed that after photocrosslinking, tensile strength, modulus of elasticity, and elongation at break were improved greatly. Moreover, the notched Izod impact strength was obviously enhanced compared with corresponding uncrosslinked blend. Scanning electron microscopy (SEM) morphological analysis showed that for uncrosslinked PP/EPDM blends, the cavitation of EPDM particles was the main toughening mechanism; whereas for dynamically photocrosslinked blends, shear yielding of matrix became the main energy absorption mechanism. The DSC curves showed that for each dynamically photocrosslinked PP/EPDM blend, there was a new smaller melting peak at about 152°C together with a main melting peak at about 166°C. Dynamic mechanical thermal analysis (DMTA) indicated that the compatibility between EPDM and PP was improved by dynamic photocrosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3371–3380, 2004     

动态硫化EPDM/PP共混物力学性能的研究

考察了硫黄用量和聚合物共混比对动态硫化ＥＰＤＭ／ＰＰ热塑性弹性体性能的影响。结果表明,随着硫黄用量增大,ＥＰＤＭ／Ｐ共混物的拉伸强度、１００％定伸应力和扯断伸长率先增大后减小、硬度有所增大,随着ＰＰ用量的增大,ＥＰＤＭ／ＰＰ共混物的拉伸强度、１００％定伸应力和硬度均有所增大,扯断伸长率也先大后减小。ＰＰ用量的变化对这些性能的影响更显。     

Effect of processing parameters on morphology and tensile properties of PP/EPDM/organoclay nanocomposites fabricated by friction stir processing

Nanocomposites-based on polypropylene (PP), ethylene-propylene diene monomer (EPDM) and Cloisite 15A have wide applications in automotive and aerospace industries and medical apparatus due to their excellent mechanical, thermal and chemical properties. In this study, a nanocomposite of PP/EPDM/nanoclay containing PP (77 wt%), EPDM (20 wt%) and nanoclay (3 wt%) was fabricated by friction stir processing (FSP) method. X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and tensile testing were performed to determine the morphology and tensile properties of this nanocomposite. The Box-Behnken design was applied to investigate the effect of the process parameters such as tool rotational speed, traverse speed and shoulder temperature on the tensile properties of the nanocomposite. The results showed that the tensile strength increased from 15.8 to 18.2 MPa with increasing the tool rotational speed and shoulder temperature while the elongation-at-break dropped from 46 to 22 %. A maximum tensile strength of 17.6 MPa and a minimum elongation-at-break of 26 % were obtained at the traverse speed of 40 mm/min when the rotational speed and shoulder temperature were at the central levels themselves. The prediction models showed that when the tool rotational speed, traverse speed and shoulder temperature were set, in the given order, as 1200 rpm, 45.65 mm/min and 113.65 °C, a simultaneous maximization of tensile strength of 16.03 MPa and elongation-at-break of 46.41 % was obtained.