Synergetic toughness and morphology of poly(propylene)/nylon 11/maleated ethylene‐propylene diene copolymer blends

Polypropylene (PP)/nylon 11/maleated ethylene‐propylene‐diene rubber (EPDM‐g‐MAH) ternary polymer blends were prepared via melt blending in a corotating twin‐screw extruder. The effect of nylon 11 and EPDM‐g‐MAH on the phase morphology and mechanical properties was investigated. Scanning electron microscopy observation revealed that there was apparent phase separation for PP/EPDM‐g‐MAH binary blends at the level of 10 wt % maleated elastomer. For the PP/nylon 11/EPDM‐g‐MAH ternary blends, the dispersed phase morphology of the maleated elastomer was hardly affected by the addition of nylon 11, whereas the reduced dispersed phase domains of nylon 11 were observed with the increasing maleated elastomer loading. Furthermore, a core‐shell structure, in which nylon 11 as a rigid core was surrounded by a soft EPDM‐g‐MAH shell, was formed in the case of 10 wt % nylon 11 and higher EPDM‐g‐MAH concentration. In general, the results of mechanical property measurement showed that the ternary blends exhibited inferior tensile strength in comparison with the PP matrix, but superior toughness. Especially low‐temperature impact strength was obtained. The toughening mechanism was discussed with reference to the phase morphology. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Crystallization behavior and mechanical properties of polypropylene random copolymer/poly(ethylene‐octene) blends

New polymer blends of polypropylene random copolymer (PP‐R) and poly(ethylene‐octene) (POE) were prepared by melt‐blending process using a corotating twin‐screw extruder. The POE content was varied up to 35%. The toughening efficiency of POE for PP‐R was evaluated by the mechanical properties of the resulted PP‐R/POE blends. The crystallization behavior and morphology of the blends were also studied. Results show that POE acts as nucleation agent to induce the crystallization of PP‐R matrix at higher crystallization temperature. Super‐toughened PP‐R/POE blends (Izod impact strength more than 500 J/m) can be readily achieved with only 10 wt % of POE. The high toughness of PP‐R/POE is attributed to cavitation and shear yielding of matrix PP‐R, as revealed by the morphology studies. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Short‐time fabrication of well‐mixed high‐density polyethylene/ultrahigh‐molecular‐weight polyethylene blends under elongational flow: morphology,mechanical properties and mechanism

As linear polyethylenes, ultrahigh‐molecular‐weight polyethylene (UHMWPE) and high‐density polyethylene (HDPE) have the same molecular structure, but the large difference in viscosity between them makes it difficult to obtain well‐mixed blends. An innovative eccentric rotor extruder (ERE) generating an elongational flow was used to prepare HDPE/UHMWPE blends within short processing times. Compared with the obvious two‐phase morphology of a sample from a twin‐screw extruder observed with a scanning electron microscope, few small UHMWPE particles were observed in the HDPE matrix for a sample from the ERE, indicating the good mixing on a molecular level of HDPE/UHMWPE blends achieved by the ERE during short processing times. The morphological changes of blends prepared using the ERE evidenced the good integration of HDPE and UHMWPE even though the UHMWPE content is up to 50 wt% in the blends. Moreover, all blends retained most of the intrinsic molecular weight. The good mixing was further confirmed from the thermal, crystallization and rheological behaviors determined using differential scanning calorimetry and dynamic rheological measurements. Importantly, the 50/50 blend presented improved mechanical properties, especially super‐impact strength of 151.9 kJ m^?2 with incomplete‐break fracture state. The strengthening and great toughening effects of UHMWPE on the blends were attributed to the addition of unwrapped UHMWPE long molecular chains. The effective disentanglement mechanism of UHMWPE chains under elongational flow was explained schematically by a non‐parallel three‐plate model. © 2019 Society of Chemical Industry     

Morphology development of EPDM/PP uncross‐linked/dynamically cross‐linked blends

Ethylene‐propylene‐diene‐terpolymer (EPDM) and polypropylene (PP)‐based uncross‐linked and dynamically cross‐linked blends were prepared both in an internal mixer and in a corotating twin‐screw extruder. The effects of composition, plasticization and mixing equipment on the morphology development and the final viscoelastic properties were studied. In the uncross‐linked blends, the plasticization resulted in a coarser morphology. Furthermore, it was shown that the majority of the plasticizer resided in the EPDM phase, enabling its deformation in the flow direction. In addition, the intensive mixing conditions inside the twin‐screw extruder resulted in a finer morphology. In the dynamically cross‐linked blends, the twin‐screw extrusion process resulted in a higher level of gel content with larger EPDM domains. The plasticization showed again a coarsening effect, resulting in interconnected cross‐linked EPDM domains. An interesting interfacial phenomenon was observed especially in the plasticized vulcanized blends where nanometer size occluded PP domains were stripped off and eroded into the EPDM phase. With the exception of the nonplasticized uncross‐linked blends, the viscoelastic properties of all other blending systems were found to be directly affected by the morphology, gel content (in the case of cross‐linked blends), and the presence of the plasticizer. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

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     

Toughening of polypropylene with styrene/ethylene‐butylene/styrene tri‐block copolymer: Effects of reactive and nonreactive compatibilization

The effects of compatibilization on the toughening of polypropylene (PP) by melt blending with styrene/ethylene‐butylene/styrene tri‐block copolymer (SEBS) in a twin‐screw extruder were investigated. The compatibilizers used were SEBS functionalized with maleic anhydride (SEBS‐g‐MA), PP functionalized with acrylic acid (PP‐g‐AA), and bifunctional compound p‐phenylenediamine (PPD). The effects of the compatibilization were evaluated through the mechanical properties as well as through the determination of the phase morphology of the blends by scanning electron microscopy. Reactive compatibilized blends show up to a 30‐fold increase in impact strength compared with neat PP; likely the result of the reaction of the bifunctional compound (PPD) with the acid acrylic and maleic anhydride groups, this increase in strength rendered both morphological and mechanical stability to these blends. The addition of PPD to the blends significantly changed their phase morphologies, leading to larger average diameters of the dispersed particles, probably as a result of the morphological stabilization at the initial processing steps during extrusion, with the occurrence of chemical reactions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3466–3479, 2002     

In situ reactive compatibilization and reinforcement of peroxide dynamically vulcanized polypropylene/ethylene‐propylene‐diene monomer tpv by zinc dimethacrylate

This work demonstrates an approach of in situ reactive compatibilization between polypropylene (PP) and ethylene‐propylene‐diene monomer (EPDM) by using ZDMA as a compatibilizer and, simultaneously, as a very strong reinforcing agent. With 7phr ZDMA in the PP/EPDM (30/70, w/w) thermoplastic vulcanizate (TPV), the tensile strength and elongation at break were increased from 5.3 MPa and 222% up to 11.2 MPa and 396%, respectively. Increasing the PP concentration further improved mechanical properties of the TPVs with ZDMA. This tremendous reinforcing as well as the compatibilization effect of the ZDMA was understood by polymerization of ZDMA and ZDMA reacting with EPDM and PP during peroxide induced dynamic vulcanization. A peculiar nano‐composite structure that the crosslinked rubber particles were “bonded” by a transition zone which containing numerous of nano‐particles with dimensions of about 20–30 nm was observed from transmission electron microscopy (TEM). Scanning electron microscopy (SEM) results showed that increase of PP/EPDM ratio reduced the size of crosslinked EPDM particles. Moreover, we found that the ZDMA reinforced EPDM particles resulted in a higher tan δ peak temperature for EPDM phase and built “filler‐filler”‐like networking in the PP melt. POLYM. COMPOS. 34:1357–1366, 2013. © 2013 Society of Plastics Engineers     

粉状聚丙烯增韧增强研究

采用机械共混方法对粉状聚丙烯（PP）进行了增韧增强研究，探讨了增韧剂、增强剂和有少量自制的固相甲基丙烯酸（MAA）接枝粉状聚丙烯（PP-g-MAA)作增容剂存在下对粉状PP共混体系力学性能的影响，用热重分析法考察了改性粉状PP的热性能。结果表明，（乙烯／丙烯／二烯）共聚物（EPDM）／高密度聚乙烯（HDPE）为复合增韧剂，具有协同作用，可显著提高共混物的冲击强度：PP-g-MAA能明显改善PP／玻纤两相的界面结合力；PP／EPDM／HDPE玻璃纤维共混体系可以获得理想的增韧增强效果。     

Effect of blending sequence on the morphology and properties of polyamide 6/EPDM‐g‐MA/epoxy blends

The ternary blends of polyamide 6/maleated ethylene‐propylene‐diene rubber/epoxy (PA6/EPDM‐g‐MA/EP) were prepared by a twin‐screw extruder with four different blending sequences. With the variation of blending sequence, the ternary blends presented distinct morphology and mechanical properties because of different interactions induced by various reactive orders. The addition of epoxy could increase the viscosity of the PA6 matrix, but a considerably larger size of the dispersed rubber phase was observed while first preblending PA6 with epoxy followed by blending a premix of PA6/EP with EDPM‐g‐MA, which was attested by rheological behaviors and SEM observations. It was probably ascribed to the fact that the great increase of the interfacial tension between the matrix and rubber phase aroused a great coalescence of rubber particles. The presence of epoxy in the rubber phase reduced the rubber's ability to cavitate so that the toughening efficiency of the EPDM‐g‐MA was decreased. The results of mechanical testing revealed that the optimum blending sequence to achieve balanced mechanical properties is blending PA6, EPDM‐g‐MA, and epoxy simultaneously in which the detrimental reactions might be effectively suppressed. In addition, thermal properties were investigated by TG and DSC, and the results showed that there was no distinct difference. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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

The 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     

Mechanical Properties and Morphology of Ternary PP/EPDM/PE Blends

The ternary blends of high‐density polyethylene (PE), EPDM terpolymer and polypropylene (PP) have been used as a model low interfacial tension system to study encapsulation dynamics in ternary blends and their relation to the blends' mechanical properties. It was found that the modulus, tensile strength and impact resistance can be improved by PE addition if the PE is localized within the EPDM phase. A range of blend morphology was found depending on the PE viscosity and polymer incorporation sequence in the twin‐screw extruder. In the most favorable sequence, PE and EPDM were mixed together prior to their dispersion in the PP matrix. This practice resulted in a 50% increase in impact resistance when compared to mixing the three components in a single‐step.     

Morphologies of polyethylene–ethylene/propylene/diene monomer particles in polypropylene‐rich polyolefin blends: Flake structure

Morphologies of polyethylene–ethylene/propylene/diene monomer (PE/EPDM) particles in 93/7 polypropylene (PP)/PE blends were investigated. SEM micrographs of KMnO₄‐etched cut surfaces and fracture surfaces of the blends revealed the existence of the “flake” structure. In the particles, crystalline PE formations with flake shape, which remain after etching, are called flakes. In addition to the PE‐crystalline flakes, amorphous PE, located between PE crystalline lamellae and EPDM rubber, complement the flake structure. The flakes are usually linked with the PP matrix, as seen in the heptane‐treated cut surfaces. These links, although observed with compatibilized samples, originate from the crystalline nature of PE particles, if no compatibilizer is added. Separately, the morphology of Royalene (consisting of high‐density PE and EPDM rubber, used as a PP/PE compatibilizer) was investigated by low‐voltage scanning TEM. The interaction of the components in the PE/EPDM blends can explain the formation of the flakes and toughening of the PP/PE blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3087–3092, 2003     

Study on processing of ultrahigh molecular weight polyethylene/polypropylene blends

The processing of ultrahigh molecular weight polyethylene (UHMWPE) by the addition of polypropylene (PP) and high‐density polyethylene (HDPE) was investigated. The results show that the addition of PP improves the processability of UHMWPE more effectively than does the addition of HDPE. UHMWPE/PP blends can be effectively processed with a twin‐roller and general single‐screw extruder. In the extrusion of UHMWPE/PP blends, PP is enriched at the surface of the blend adjacent to the barrel wall, thus increasing the frictional force on the wall; the conveyance of the solid down to the channel can then be carried out. The melt pool against the active flight flank exerts a considerable pressure on the UHMWPE powder in the passive flight flank, which overcomes the hard compaction of UHMWPE. The PP penetrates into the gaps between the particles, acting as a heat‐transfer agent and adhesive, thus enhancing the heat‐transfer ability in the material. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 977–985, 2004     

Preparation and characterization of injection‐homo‐polypropylene filled with nano‐CaCO3

Nano‐CaCO₃/homo‐PP composites were prepared by melt‐blending using twin‐screw extruder. The results show that not only the impact property but also the bending modulus of the system have been evidently increased by adding nano‐CaCO₃. The nano‐CaCO₃ particles have been dispersed in the matrix in the nanometer scale which was investigated by means of transmission electron microscopy (TEM). The toughening mechanism of nano‐CaCO₃, investigated by means of dynamical mechanical thermal analysis (DMTA) and scanning electron microscopy (SEM), lies on that the nano‐CaCO₃ particles take an action of initiating and terminating crazing (silver streak), which can absorb more impact energy than the neat PP. At the same time, the nano‐CaCO₃ particles, as the nuclear, decrease the crystal size of PP, the results of which were investigated by means of polarized optical microscope (POM). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morphology and mechanical properties of blends of linear low density polyethylene and poly(ethene‐propene‐1‐butene)

Blends of linear low density polyethylene (LLDPE) and ethene‐propene‐1‐butene copolymer (t‐PP) were obtained through mechanical mixing using a single‐screw extruder with different compositions: 20, 40, 50, 60, and 80 wt % of t‐PP. For this, two types of polyethylene were used: 1‐hexene comonomer and 1‐octene comonomer based. The same blends were prepared in a batch mixer and the torque and temperature were analyzed. The torque showed a decrease with increasing t‐PP content, indicating better processability of the mixture in comparison with LLDPE. The morphology of the blends was analyzed by SEM and showed a composition dependence. The mechanical properties of the blends were evaluated by tensile tests. The results revealed that the best properties were obtained in a 20% t‐PP blend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1255–1261, 2006     

Effects of compounding procedure on morphology development,melt rheology,and mechanical properties of nanoclay reinforced dynamically vulcanized EPDM/polypropylene thermoplastic vulcanizates

New nanocomposite thermoplastic vulcanizates (TPVs) comprising dynamically cross‐linked nanoscale EPDM rubber particles dispersed throughout the polypropylene (PP) matrix have been prepared by both batch and continuous melt blending of PP with EPDM in the presence of vulcanizing ingredients, nanoclay and maleated EPDM (EPDM‐g‐MA) as compatibilizer. X‐ray diffraction, linear melt viscoelastic measurement, and tensile mechanical behavior results revealed that the developed microstructure is strongly affected by the type of the melt compounding process as well as the route of material feeding. When EPDM phase was precompounded with a vulcanizing agent, nanoclay, and EPDM‐g‐MA prior to the melt blending with PP, not only nanosize cross‐linked rubber particles appeared uniformly throughout the PP continuous phase, but also the melt blending leads to the significant enhancement of the mechanical properties compared with counterpart samples prepared by one‐step melt mixing process. Also better dispersion of nano layers in the rubber compound before melt blending with PP results in higher mechanical properties of the resulted TPV. POLYM. ENG. SCI., 56:914–921, 2016. © 2016 Society of Plastics Engineers     

Morphology and mechanical properties of melt drawn chopped UHMWPE fiber/HDPE blends

Blends of ultrahigh molecular weight polyethylene (UHMWPE) chopped fibers with high density polyethylene (HDPE) were prepared by melt mixing extrusion, followed by melt drawing. The combined effect of composition and flow on the morphology was investigated by microbeam synchrotron X‐ray diffraction and high resolution scanning electron microscopy. Apparently in the drawn blends, the presence of fibers resulted in a higher degree of orientated morphology and—as revealed by differential scanning calorimetry—higher degrees of crystallinity and melting points. Significant improvement of mechanical properties was observed with increase of the fiber volume fraction. These results indicate that the oriented arrays of immiscible UHMWPE domains aligned in the flow direction, joined by fiber‐induced crystallization of the surrounding HDPE matrix, and provide strong reinforcing effect. POLYM. ENG. SCI., 46:807–811, 2006. © 2006 Society of Plastics Engineers     

Blending of immiscible polymers in a mixing zone of a twin screw extruder—effects of compatibilization

The dependence of the morphology development of physical as well as of reactive compatibilized polypropylene/polyamide 6 (PP/PA6) blends in a mixing zone of a co‐rotating twin screw extruder on blend composition and screw rotational speed was investigated. A special process analytical set‐up based on a co‐rotating twin screw extruder was used, which allowed melt sampling from different positions along the operating extruder in time periods less than 10 seconds. It has been shown that the disperse particle sizes in physical blends depend crucially on the blend composition because of the increasing influence of coalescence with an increasing concentration of the disperse phase. Furthermore, the morphology of physical PP/PA6 blends depends strongly on their rheological properties. In contrast, the influence of the screw rotational speed on the morphology is minor. The resulting particle size in a mixing zone is achieved already after a short screw length. The particle size of compatibilized blends is significantly smaller than in physical blends because of the better conditions for drop break‐up and the suppression of coalescence effects. Due to this, compatibilization has a stronger influence on the blend morphology than a variation of process or rheological conditions with physical blends. Furthermore, the compatibilization leads to a concurrent crystallization of the PA6 phase with the PP phase.     

Toughening of polypropylene with styrene/ethylene‐butylene/styrene tri‐block copolymer: Effects of mixing condition and elastomer content

The effect of processing conditions and elastomer content on the toughening of Polypropylene (PP) by melt blending with styrene/ethylene‐butylene/styrene tri‐block copolymer (SEBS) in a twin‐screw extruder has been investigated. The parameters analyzed were: temperature profile, screw speed, and feed rate of the blend components. Their effect was evaluated through the mechanical properties (tensile strength and Izod impact resistance at room temperature) as well as the morphology of the dispersed phase by means of scanning electron microscopy (SEM). The results showed that the impact resistance increases with increasing rotor speed and feed rate and decreases when the temperature profile is increased. The parameter with the greatest effect on the mechanical properties was the variation in rotor speed. Despite the fact that impact resistance as high as 25 times that of neat PP has been achieved with blends containing 20 wt % SEBS, no significant modification in phase morphology has been observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2185–2193, 2001     

Toughening of polypropylene with styrene/ethylene‐butylene/styrene triblock copolymer: Effects of reactive and nonreactive compatibilization

The effects of the compatibilization on the toughening of polypropylene (PP) by melt blending with styrene/ethylene‐butylene/styrene triblock copolymer (SEBS) in a twin‐screw extruder were investigated. The compatibilizers used were an SEBS functionalized with maleic anhydride, a PP functionalized with acrylic acid, and a bifunctional compound, p‐phenylenediamine (PPD). The effects of the compatibilization were evaluated through the mechanical properties and by the determination of the phase morphology of the blends by scanning electron microscopy. Reactive compatibilized blends show up to a 30‐fold increase in impact strength compared to neat PP, which was likely to have been due to the reaction of the bifunctional compound (PPD) with the acid acrylic and maleic anhydride groups, which rendered both morphological and mechanical stability to these blends. The addition of the PPD to the blends significantly changed their phase morphologies, leading to larger dispersed particles' average diameters, probably due to the morphological stabilization at the initial processing steps during extrusion, with the occurrence of the chemical reactions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1081–1094, 2003