Ethylene-propylene-diene Terpolymer Phase Research Articles

Polylactic acid/UV-crosslinked in-situ ethylene-propylene-diene terpolymer nanofibril composites with outstanding mechanical and foaming performance

Polylactic acid (PLA) is a promising biomass and biodegradable polymer but suffers from its brittle feature and poor foaming ability. Thus, many ductile polymers have been used to modify PLA through compounding. Although some of them can improve the toughness, the strength and rigidness of PLA are seriously scarified due to the large dosage, poor dispersion, and see-island structures. Herein, UV-crosslinking-assisted in-situ fibrillation was developed to fabricate ethylene-propylene-diene terpolymer (EPDM) nanofibril-reinforced PLA composites. Twin-screw compounding followed by melt blowing was used to stretch EPDM phase into nanofibrils, while UV-crosslinking was proposed to stabilize the EPDM nanofibrils in the final PLA/EPDM composites. Thanks to UV-crosslinking, EPDM nanofibrils with an average diameter of 94.3 nm were achieved in PLA. Due to the heterogeneous nucleating effect of UV-crosslinked EPDM nanofibrils, the crystallization rate of PLA was significantly enhanced, and refined crystal morphology with fibrous structures was obtained. Surprisingly, merely 3 wt% of UV-crosslinked EPDM nanofibrils remarkably enhanced the mechanical properties of PLA. The tensile toughness and impact strength were increased by 620% and 440%, respectively, without sacrificing strength and rigidness. Moreover, the UV-crosslinked EPDM nanofibrils also significantly improved the foaming ability of PLA. The PLA/UV-crosslinked EPDM foam with an expansion ratio of up to 28-fold was achieved for the first time by mold-opening microcellular injection molding. With the presence of UV-crosslinked EPDM nanofibrils, the expansion ratio and cell population density of the foams can be increased by 470% and 5 orders of magnitude, respectively. Owing to the super-high expansion ratio and unique micro/nanoscale structures on cell walls, the 28-fold expanded PLA/EPDM foam exhibited outstanding thermally insulating performance with a thermal conductivity of as low as 26.3 mW/m∙K.

Influence of process parameters on property of PP/EPDM blends prepared by a novel vane extruder

Abstract In this study, thermoplastic elastomers based on polypropylene (PP) and ethylene-propylene-diene terpolymer (EPDM) were prepared via direct melt blending in a novel vane extruder. The influence of processing temperature and rotor speed on the degree of cross-linking of the EPDM phase, the tensile properties, the melting behavior and the crystallization morphology of PP/EPDM blends was investigated. It was observed that the volume fraction (Vr) of the vulcanizate arriving swelling equilibrium reached the maximum value when the processing temperature was 190°C. The tensile properties showed better performance at 195°C, at which the PP/EPDM blend obtained good dispersive mixing performance. Moreover, the Vr of the vulcanizate arriving swelling equilibrium reached the maximum value when the rotor speed was 60 rpm, at which the dispersive mixing performance and tensile properties of the PP/EPDM blend were better.

Assessment of Mixing Efficiency of Intermeshing Rotor Mixers on Morphological and Mechanical Properties and Crosslink Density of Dynamically Vulcanized EPDM/PP Blends

The mixing efficiency of intermeshing rotor internal batch mixers for the preparation of rubber-rich thermoplastic vulcanizates (TPV) based on ethylene propylene diene terpolymer (EPDM) and polypropylene (PP) blends was investigated. Two laboratory scale mixers, namely intensive batch mixer (INS) and kneader batch mixer (KND), were used. The mixer choice at controlled mixing conditions was investigated to determine its effects on morphological and mechanical properties and crosslink density of the prepared EPDM/PP TPVs. Such effects were found on the degradation of the polymer, on the distribution of the EPDM phase in the blend morphology, particularly the size of EPDM inclusion, and on the crosslink density of the EPDM phase. In summary, the different mixing efficiencies of INS and KND type mixers affect the EPDM/PP TPVs and their properties. Also, the INS mixer has higher mixing efficiency than the KND mixer.

The morphology and mechanical properties of PP/EPDM/nano-CaCO3 composites: effect of initial mixing state

Polypropylene (PP) was blended with ethylene–propylene–diene terpolymer (EPDM) and calcium carbonate nanoparticles (nano-CaCO3), where all the components were in different initial mixing states, i.e., all in solid (solid blending composite), nano-CaCO3 and EPDM first forming solid master batch, then being mixed with solid PP (master batch blend composite) and all in melt (melt blending composite). The phase morphology, especially the distribution of nano-CaCO3, and mechanical properties of the resultant composites and their dependence on the initial mixing states of the components were studied systematically. Morphological observation revealed that essentially different from the respectively dispersed morphology of nano-CaCO3 particles and EPDM phase in the PP matrix in the solid blending composite, abundant well-dispersed nano-CaCO3 particles concentrating around EPDM phase in the melt blending composite. Due to the cavitation initiated by the debonding and the fibrillation present at interface as a result of well-dispersed nano-CaCO3 particles, its impact strength was pronouncedly enhanced, increasing 280 % compared to PP/EPDM composite. Our work paves the way to obtain high-performance PP composites.

The Effects of Different Processing Methods on the Morphology and Properties of PP/EPDM/Nano-CaCO3 Ternary Blend

The effects of different processing methods (direct extrusion, two-step extrusion or lateral injection extrusion) on the morphology of polypropylene (PP)/ethylene-propylene-diene terpolymer (EPDM)/calcium carbonate nanoparticles (nano-CaCO3) ternary blend were investigated, including the morphology of the EPDM phase and the distribution of nano-CaCO3 particles, by means of scanning electron microscopy (SEM). The results showed that the processing methods had a significant influence on the morphology of the EPDM phase and the distribution of nano-CaCO3 particles. In the lateral injection extruded blends, it was amazingly observed that the EPDM particles encapsulated the PP phase tightly, and the dimension of EPDM particles was remarkably decreased. It was also found that the content of nano-CaCO3 particles in the matrix of the lateral injection extruded blends was less than that of the two-step extruded blend, and that of the direct extruded blend was most. The properties of the ternary blend, including dynamic mechanical properties, rheological properties, and crystallization, were characterized in order to confirm the variety of morphologies caused by the different processing methods. The differences in the crystallization temperature, elastic modulus, and glass transition temperature of the blends prepared by different methods well agreed with the variation of their morphology.

Effect of carbon black addition and its phase selective distribution on the stress relaxation behavior of filled thermoplastic vulcanizates

AbstractThe long term mechanical behavior of thermoplastic vulcanizates (TPV) based on polypropylene (PP) and ethylene propylene diene terpolymer (EPDM) and different types and concentrations of carbon black (CB) has been characterized by means of stress relaxation experiments. Evaluation of the relaxation curves was carried out using the two‐component model allowing a division of the initial stress into different stress components which are caused by different networks available in TPV. The discussion focussed on the background of the stress components, which are originated by the CB addition, the non‐relaxing stress components σ, and σ, as well as the relaxing stress components ΔσCB(polymer‐layer) and ΔσCB(network). It was found that the concentration and type of CB as well as the phase specific CB distribution strongly affect the non‐relaxing and relaxing stress components. Up to a CB concentration of 9% in the EPDM phase the composite behaves as a thermo‐rheologically simple material because the impact of CB addition on the α‐relaxation of the crystalline PP phase is still negligible. A master curve was created by the horizontal shift of the relaxing stress curves ΔσComp(t) to a reference curve. At higher local CB loadings the additional relaxation processes induced by CB addition overlap with the α‐relaxation, thus, no master curve could be made in that case. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Dynamic rheology–morphology relationship of PP/EPDM blends prepared by melt mixing under Sc-CO2

It was demonstrated that the high mixing efficiency of twin screw extruder (TSE) helped to disperse the ethylene–propylene–diene terpolymer (EPDM) domains in polypropylene (PP) matrix, but could not lead to the uniform distribution of EPDM phase with small sizes because of the thermodynamical immiscibility between PP and EPDM. So supercritical carbon dioxide (Sc-CO2) was environmentally and economically introduced to the twin screw extrusion to assist the melt mixing of PP and EPDM. The scanning electron microscopy photographs showed that co-continuous phase morphology was formed to some extent for the PP/EPDM 60/40 blend prepared with Sc-CO2, especially with 2.5 wt% Sc-CO2. This was the one important reason for that the complex viscosity and storage modulus of PP/EPDM 60/40 blend increased with the increase of Sc-CO2 concentration.

Morphology development in thermoplastic vulcanizates (TPV): Dispersion mechanisms of a pre-crosslinked EPDM phase

The fragmentation and dispersion in molten polypropylene (PP) of several pre-crosslinked and plasticized ethylene–propylene–diene terpolymer (EPDM) networks was studied. Thus, the morphologies and mechanical properties of PP/EPDM blends having similar compositions but made from either un-crosslinked, pre-crosslinked or dynamic-crosslinked EPDMs were compared. The results first highlight the importance of the gel fraction of the pre-crosslinked EPDMs, as well as the impact of the thermoplastic matrix proportion on the quality of the dispersion of such networks. As a result, pre-crosslinked EPDM having a gel fraction below g EPDM = 0.7 can be finely and homogeneously fragmented and dispersed in presence of PP. It can be then admitted a collision–coalescence–separation type erosion mechanism of the EPDM domains. Nevertheless, contrarily to some theoretical model expectations, a partial fragmentation of the chemical networks was always observed even at very high crosslink density ( g EPDM > 0.7). Finally, the blends crosslinked under shearing (dynamic-crosslinked) showed a clear mechanical property synergy due to their fine and homogeneous morphology coupled with the full crosslinking of the elastomer. In the end, these results brought significant information on TPV morphology stabilization and their related mechanical properties.

EPDM/St‐An graft copolymerization reaction behavior by phase inversion emulsion and the toughness effect of EPDM‐g‐SAN on SAN resin

AbstractStyrene‐EPDM‐acrylonitrile tripolymer (EPDM‐g‐SAN) was synthesized by the graft copolymerization of styrene (St) and acrylonitrile (An) onto ethylene‐propylene‐diene terpolymer (EPDM) with “phase inversion” emulsification technique. The high impact strength engineering plastics AES was the blend of SAN resin and EPDM‐g‐SAN, which occupied good weathering and yellow discoloration resistivity. The effects of An percentage in comonomer and the weight proportion of EPDM to St‐An on graft copolymerization behavior and AES notched impact strength were studied. The results showed that monomer conversion ratio (CR) exhibited a peak when the An percentage changed, and the maximum value was 97.5%. Grafting ratio (GR) and grafting efficiency (GE) enhance as well. The notched impact strength of AES presented a peak with the maximum value of 53.0 KJ/m2, when An percentage was at the range of 35–40%. The spectra of FTIR showed that St and An were graft onto the EPDM. DSC analysis illuminated that Tg of EPDM phase in the blends was lower than that of the pure EPDM. TEM and SEM micrographs indicated that the polarity of g‐SAN of EPDM‐g‐SAN was the main factor effect the particle morphology, in terms of size, distribution and isotropy. When weight ratio of St to An was 65/35, the polarity of g‐SAN chains was appropriate, and the EPDM‐g‐SAN particles dispersed well in the SAN matrix. The super impact toughness is interpreted in terms of EPDM phase cavitation and enhanced plastic shear yielding. The highest toughness occurs at an optimum EPDM‐g‐SAN phase particle size which is about 0.2 μm in SAN resin matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Effect of dynamic vulcanization on co‐continuous morphology

AbstractThis study examines the effect of dynamic vulcanization on the co‐continuous morphology in ethylene‐propylene‐diene terpolymer (EPDM)/polypropylene (PP) blends using a technique of morphology investigation involving focused ion beam (FIB) etching of the sample surface, followed by topological investigation of the sample surface using tapping mode atomic force microscopy (TMAFM). The FIB ion etching rates of EPDM and PP are distinctly different, and these differences create a significant topological contrast between the phases when subsequently analyzed by atomic force microscopy. This approach allows for the high‐resolution observation of dispersed EPDM, and phases as small as 100 nm, are clearly identified. Since it is shown that the etching rates of noncrosslinked and crosslinked EPDM are similar, it was necessary to selectively remove the noncrosslinked EPDM phase by solvent dissolution. This combination of techniques then allows for the clear distinction of polypropylene, as well as noncrosslinked and crosslinked EPDM phases in the blend. The high‐resolution micrographs together with the continuity data, surprisingly, indicate that a noncrosslinked co‐continuous EPDM phase (α‐network) transits to a finer network of crosslinked EPDM (β‐network) after dynamic crosslinking. It is suggested that this β‐network is produced as a result of the viscosity mismatch between the noncrosslinked and crosslinked EPDM melt occurring at the outer envelope of the α‐network during dynamic crosslinking. As the crosslinked material pulls away from the noncrosslinked material under dynamic melt mixing conditions, it creates a smearing effect. It is shown that the initial α‐network maintains its continuity and demonstrates a diminished pore diameter as crosslinking proceeds. Furthermore, when the noncrosslinked material is extracted almost no crosslinked phase (<1%) is found to be present in the extract. These results strongly indicate that the crosslinking proceeds initially at the outer envelope of the EPDM phase, and works its way toward the center. © 2006 American Institute of Chemical Engineers AIChE J, 2006

Phase morphology evolution and compatibility improvement of PP/EPDM by ultrasound irradiation

The effects of ultrasonic irradiation on morphology and compatibility of polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM) blends were examined. Results show that ultrasound irradiation lead to stable morphology with reduced disperse phase size. Dynamic rheological analysis indicates the more homogeneous internal structure of PP/EPDM blend is obtained with ultrasonic irradiation. Increase the residence time of the blends in the ultrasound irradiating zone, the structure of the blends get even more homogeneous. The interfacial tension between PP and EPDM melts obtained from the Palierne emulsion model decreases with applying of ultrasound irradiation and increasing of residence time. The glass transition temperatures of PP and EPDM phase become closer to each other with ultrasonic irradiation. FTIR analysis indicates in situ copolymers formation between PP and EPDM happens with ultrasound irradiation and the copolymer consequently acts as compatiblizers for the blend.

Toughening of Polystyrene with Ethylene‐Propylene‐Diene Terpolymer (EPDM) Compatibilized by Styrene‐Butadiene‐Styrene Block Copolymer (SBS)

AbstractSummary: Polystyrene (PS) was toughened with ethylene‐propylene‐diene terpolymer (EPDM) in the presence of styrene‐butadiene‐styrene block copolymer (SBS). Incorporation of SBS into the PS/EPDM blends clearly improved the impact properties. For PS/EPDM/SBS (mass ratio: 69/21/10) blends, the notched Charpy impact strength reached a maximum value of 26.3 kJ/m2. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that SBS was distributed on the interface between PS and EPDM. Butanone extraction and FTIR analysis found that there was a grafting reaction between PS and EPDM phase during melt compounding. Shearing and processing rheological behaviors of blends were evaluated with a Haake capillary rheometer and a torque rheometer, respectively. magnified image

Effect of ultrasound on extrusion of PP/EPDM blends: Structure and mechanical properties

AbstractThe effects of ultrasonic irradiation on the mechanical properties, morphology, and crystal structure of polypropylene (PP)/ethylene‐propylene‐diene terpolymer (EPDM) blends were examined. Results show that appropriate irradiation intensity can noticeably increase the toughness of the PP/EPDM blends without reducing rigidity. Scanning electron microscopic (SEM) observation shows that with ultrasonic irradiation, the morphology of a well‐dispersed EPDM phase is formed in the PP/EPDM blend. The glass transition temperatures of PP and EPDM phase approach each other as a result of ultrasonic irradiation. Differential Scanning Calorimetric (DSC) analysis indicates that the crystallinities of the PP and EPDM phases increase with ultrasonic irradiation, and β crystals of PP form in the PP/EPDM blend with ultrasonic irradiation, which is proven by wide angle X‐ray diffraction (WAXD) analysis. Polym. Eng. Sci. 44:1509–1513, 2004. © 2004 Society of Plastics Engineers.

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

AbstractThe 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 ultrasound on extrusion of polypropylene/ethylene–propylene–diene terpolymer blend: Processing and mechanical properties

AbstractThe effects of ultrasonic irradiation on extrusion processing and mechanical properties of polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM) blends are examined. Results show that appropriate irradiation intensity can prominently decrease die pressure and apparent viscosity of the melt, increase output, as well as increase toughness of PP/EPDM blends without harming rigidity. In case the blends are extruded with ultrasonic irradiation twice, the impact strength of the blend rises sharply at 50–100 W ultrasonic intensity, and amounts to more than 900 J/m, 1.5 times as high as that of blend without ultrasonic irradiation. Scanning electron microscopy observation shows that with ultrasonic irradiation, morphology of uniform dispersed EPDM phase and good adhesion between EPDM and PP matrix was formed in PP/EPDM blend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3519–3525, 2003

Mechanical properties and morphological structures of short glass fiber reinforced PP/EPDM composite

The mechanical properties and crystal morphological structures of short glass fiber (SGF) reinforced dynamically photo-irradiated polypropylene (PP)/ethylene–propylene–diene terpolymer (EPDM) composites were studied by mechanical tests, wide-angle X-ray diffraction (WAXD), optical microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). The mechanical properties of PP/EPDM composites, especially the tensile strength were greatly strengthened by dynamically photo-irradiation and the incorporation of SGF. The results from the WAXD, SEM, DSC, and TGA measurements reveal: (i) the formation of β-type crystal of PP in the PP/EPDM/SGF composite; (ii) the fiber length in dynamically photo-irradiated PP/EPDM/SGF composites are general longer than that in corresponding unirradiated samples. The size of EPDM phase in the photo-irradiated composites reduces obviously whereas the droplet number increases; (iii) photo-irradiation improves the interface adhesion between SGF and polymer matrix; (iv) the melting and crystallization temperatures of the photo-irradiated composites are not affected greatly by increasing the SGF content; (v) the thermal analysis results show that the incorporation of SGF into PP/EPDM plays an important role for increasing its thermal stability.

Miscibility of blends of ethylene‐propylene‐diene terpolymer and polypropylene

AbstractThe miscibility of polymers is not only an important basis for selecting a proper blending method, but it is also one of the key factors in determining the morphology and properties of the blends. The miscibility between ethylene‐propylene‐diene terpolymer (EPDM) and polypropylene (PP) was explored by means of dynamic mechanical thermal analysis, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC). The results showed that a decrease in the PP content and an increase of the crosslinking density of EPDM in the EPDM/PP blends caused the glass‐transition temperature peaks of EPDM to shift from a lower temperature to higher one, yet there was almost no variance in the glass‐transition temperature peaks of PP and the degree of crystallinity of PP decreased. It was observed that the blends prepared with different mixing equipment, such as a single‐screw extruder and an open mill, had different mechanical properties and blends prepared with the former had better mechanical properties than those prepared with the latter. The TEM micrographs revealed that the blends were composed of two phases: a bright, light PP phase and a dark EPDM phase. As the crosslinking degree of EPDM increased, the interface between the phases of EPDM and PP was less defined and the EPDM gradually dispersed in the PP phase became a continuous phase. The results indicated that EPDM and PP were both partially miscible. The mechanical properties of the blends had a lot to do with the blend morphology and the miscibility between the blend components. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 315–322, 2002

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

AbstractThe 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.

Acrylonitrile–styrene copolymer grafted onto ethylene–propylene–diene terpolymer

The two-phase structure of the acrylonitrile–styrene copolymer grafted onto ethylene–propylene–diene terpolymer (EPDM) was investigated using an electron microscope. It was found that the microstructure depends on the solvent system for graft copolymerization, separation of the graft copolymer, and the processing procedure. The graft EPDM phase forms the discontinuous phase in chlorobenzene and in the toluene–ethyl acetate mixed solvent, whereas it is the continuous phase in the hexane–ethyl acetate mixed solvent. The phase inversion of the rubber phase in the case of the latter is carried out partially in the separation procedure and completely in the processing procedure.