Structure and property relationship
Buncha Suksut; Pathamanat Poonkasem; Sirirat Prasittinawa; Patcharapon Somdee
Abstract
Composites of polypropylene (PP) and calcium lactate (CL) with a constant weight percentage of 60% and 40%, respectively, were compounded with 3, 5 and 7 phr of epoxidized soybean oil (ESO) plasticizer using an internal mixer. The testing samples were prepared using an injection molding technique. The ...
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Composites of polypropylene (PP) and calcium lactate (CL) with a constant weight percentage of 60% and 40%, respectively, were compounded with 3, 5 and 7 phr of epoxidized soybean oil (ESO) plasticizer using an internal mixer. The testing samples were prepared using an injection molding technique. The effects of the mold temperature and annealing treatment on the morphological and mechanical properties of PP-based composites using polarized optical microscopy (POM), differential scanning calorimetry (DSC), universal testing machines (UTM), and impact tester were performed. The results showed a remarkable increase in the elongation-at-break and impact strength, but a noticeable decrease in tensile strength and stiffness with increasing ESO contents. The experimental results also indicated that the higher mold temperature significantly improved the tensile strength and stiffness of samples due to an increase in spherulite size for neat PP, PP/CL composite and PP/CL composite with 3 phr of ESO. Additionally, annealing treatment enhanced the tensile and impact strengths of both neat PP and PP/CL composite, which was attributed to the increase in the crystal perfection and degree of crystallinity. These findings suggested that mechanical improvements using high mold temperature and annealing treatment were confined to the incorporation of an ESO plasticizer. The resulting performance of the plasticized PP composites after thermal treatment was described by two possibilities: the loss in the adhesion between the components and the migration of plasticizer.
Structure and property relationship
Zhijie Zhao; Ping Hai; Minjuan Zhang; Yongbiao Zheng; Yuerong Chen; Cunling Long; Hongtao Zhang; Xinyi Zhang
Abstract
The presence of ultrahigh molecular weight species in polymer melt facilitates the formation of highly-oriented crystalline structures and favors the improvement of mechanical properties. However, due to the random copolymer chain architecture, it is difficult to obtain high orientation of crystals for ...
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The presence of ultrahigh molecular weight species in polymer melt facilitates the formation of highly-oriented crystalline structures and favors the improvement of mechanical properties. However, due to the random copolymer chain architecture, it is difficult to obtain high orientation of crystals for polypropylene random copolymers (PPR). In this work, two binary blends including polypropylene (PP)/ultrahigh molecular weight polyethylene (UHMWPE) and polypropylene random copolymer (PPR)/UHMWPE were fabricated via solution blending and subsequent melt shear through mini-injection molding. It was found that a highly-oriented crystalline structure forms under shear flow in both blend series. The tensile strength of PP blends increased from 38.3MPa to 43.8MPa while the PPR blends showed a more significant property enhancement and increased from 32.5MPa to 38.1MPa. Importantly, PPR showed an increased miscibility with UHMWPE in comparison with PP due to the existence of ethylene segments. The tensile toughness of PPR samples was greatly maintained especially for blends with small addition of UHMWPE, which may be ascribed to the crack-suppression effect originated from well[1]dispersed UHMWPE domains (particle size < 0.50 μm) locked by the cocrystal structures between PPR segments and molecularly mixed PE chains.
Structure and property relationship
Leila Latreche; Samira Maou; Lokmane-Taha Abdi; Tahir Habila; Yazid Meftah
Abstract
Polypropylene (PP) is a strong, tough, crystalline thermoplastic material with high performance. Because of its diverse thermo-physical and mechanical properties, it is utilized in a wide variety of disciplines. In this study, the impact of free quenching on the thermo-physical characteristics of PP/calcium ...
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Polypropylene (PP) is a strong, tough, crystalline thermoplastic material with high performance. Because of its diverse thermo-physical and mechanical properties, it is utilized in a wide variety of disciplines. In this study, the impact of free quenching on the thermo-physical characteristics of PP/calcium carbonate (CaCO3) composites was examined. Three distinct heating procedures were used. First, composites were cooled from their melting phase temperature to ambient temperature. Second, composites were cooled from 130°C to a pre-determined and controlled temperature (T: 0°, 20°, 30°, 40°, 50°, 60°, 70°, 80°C). Third, composites were temperature-tested using annealing. The findings suggest that the elongation-at-break and impact strength may be improved following an initial quenching process from the melting phase to ambient temperature. On the other hand, a second quenching process at 0°C produces superior results, and a correlation between mechanical and thermal characteristics is noted; however, while these qualities are increased, others, such as flexibility, density, Vicat softening temperature (VST), and heat distortion temperature (HDT) are negatively impacted.
Structure and property relationship
Shokoufeh Hakim; Mehdi Nekoomanesh; Ali Shahrokhinia
Abstract
Three polypropylene samples (1-3) were synthesized with a 4th generation Ziegler-Natta catalyst in the presence of cyclohexyldimethoxymethylsilane (donor c), dicyclopenthyldimethoxysilane (donor d) and diisopropyldimethoxysilane (donor p), respectively, as external electron donors. The physical properties ...
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Three polypropylene samples (1-3) were synthesized with a 4th generation Ziegler-Natta catalyst in the presence of cyclohexyldimethoxymethylsilane (donor c), dicyclopenthyldimethoxysilane (donor d) and diisopropyldimethoxysilane (donor p), respectively, as external electron donors. The physical properties of the synthesized polypropylenes were determined. For samples 1 to 3, Successive self-nucleation and annealing (SSA) and Fourier transform infrared spectroscopy (FT-IR) analyses indicated that the relative content of the fraction with high isotacticity and regularity in conformational structure decreased in contrast with the fraction of low isotacticity and low uniformity in stereo-defect distribution from sample 1 to 3. The results demonstrated that the longer the isotactic sequence length and the less uniform the stereo-defect distribution, the greater the conformational order. Deconvolution of the molecular weight distribution curves indicated that the stability of the active centers increased from samples 1 to 3, but the participation of stereo-specefic active centers in the polymerization decreased. DMA tests showed that samples 3 and 1 had the highest damping ability and storage modulus, respectively.
Structure and property relationship
Majid Habibollahi; Morteza Ehsani; Jalil Morshedian
Abstract
In this study, poly carbonate (PC) and poly (ethylene terephthalate) (PET) were reactive melt-blended under two different conditions to produce PC/PET copolymers. For each condition, samples were taken at specified mixing times representative a specific structure of copolymers and each one employed to ...
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In this study, poly carbonate (PC) and poly (ethylene terephthalate) (PET) were reactive melt-blended under two different conditions to produce PC/PET copolymers. For each condition, samples were taken at specified mixing times representative a specific structure of copolymers and each one employed to physically compatibilize a PC/PET blend with a fixed composition. Reactive blending and copolymer structure are described by solubility analysis results. Continues declining and going through a minimum are two trends of solubility versus mixing time depending on reactive blending condition. Decreasing and increasing patterns of solubility curves were attributed to the formation of copolymers with longer and shorter block lengths, respectively, and the level of solubility was related to the amount of produced copolymers. Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) techniques were employed to investigate blend compatibility. The content and structure of copolymers showed favorable correlation of Tg differences of blend components and PET crystallinity. As expected, Tg of blend components approached to each other by the addition of copolymers, and the copolymers with longer block length caused less Tg differences. The melting point and crystallinity of PET were affected by introducing the copolymers too. In addition to the main melting endotherm, melting endotherm peaks of compatibilized blends had a shoulder that its corresponding melting point and crystallinity are related to the copolymer structure so that the longer length of block copolymer or higher its amount leads to the higher melting points. The SEM micrographs showed that, after the addition of the copolymer, smaller PET particles formed and uniformly dispersed in the PC matrix. A strong correlation between the blend morphology and the level of blend compatibility was demonstrated. The more compatibilized PC/PET blend, the better dispersion of PET particles in the PC matrix was obtained. The results of this study could be a basis for designing and production of compatibilizers suitable to achieve a desired level of compatibility in PC and polyester blends, specially in PC/PET blend.
Structure and property relationship
Qian Li; Yongjie Zhang; Huayi Li; Zhongchuan Peng; Yu Zhang; Youliang Hu
Abstract
PP-g-PS copolymer is a typical compatilizer used in polypropylene and polystyrene immiscible blends. PP-g-PS copolymers with different side chain lengths were synthesized, and their thermal and mechanical properties were characterized by differential scanning calorimetry (DSC), polarizing optical microscopy ...
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PP-g-PS copolymer is a typical compatilizer used in polypropylene and polystyrene immiscible blends. PP-g-PS copolymers with different side chain lengths were synthesized, and their thermal and mechanical properties were characterized by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and dynamic mechanical analysis (DMA), respectively. The DSC and POM results show that the introduction of PS side chain dramatically accelerates the crystallization rate of the PP main chain due to the covalent bond in the PP and PS copolymer. Furthermore, the copolymers become more rigid as the PS component content increases. Blend of PP with PP-g-PS copolymer was prepared to investigate the compatibility between PP and PS. The properties of five PP/PP-g-PS binary blends were characterized by DSC, DMA, scanning electron microscopy (SEM) and mechanical testing. Well dispersion of PS and small PS particle size are detected in the binary blends. The formation of covalent bond between PP and PS also increases the compatibility and interfacial adhesion between these two phases.
Structure and property relationship
Somaye Akbari; Niloofar Eslahi; Mohammad Haghighat Kish
Abstract
The present study investigates the hydrophilic properties of acrylonitrile/acrylic acid P(AN/AA) copolymer films with various acrylic acid (AA) contents dendrigrafted with citric acid from zero to fourth generation numbers. It was found that the hydrophilicity of the dendrigrafted films was a complicated ...
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The present study investigates the hydrophilic properties of acrylonitrile/acrylic acid P(AN/AA) copolymer films with various acrylic acid (AA) contents dendrigrafted with citric acid from zero to fourth generation numbers. It was found that the hydrophilicity of the dendrigrafted films was a complicated phenomenon. Various parameters such as intermolecular hydrogen bonding, roughness and active functional groups affected the wettability of the film samples measured via static contact angle. The results revealed that the hydrophilicity decreased with increasing the generation number owing to the steric hindrance of terminal groups. However, active functional group increased by rising generation numbers which was confirmed using zeta potential measurement. Furthermore, the percentage conversion of the reactions showed a reduction with increasing generation number and AA content which was in agreement with the reduction in wettability corresponding to the higher contact angle. On the other hand, zeta potential as well as roughness of the films increased with successive generations.
Structure and property relationship
Igor Chmutin; Ludmila Novokshonova; Petr Brevnov; Guzel Yukhayeva; Natalia Ryvkina
Abstract
There are described nanocomposites based on ultra high molecular weight polyethylene and graphite nanoplates prepared by in-situ polymerization method. It is carried out a comprehensive study of electric properties of these composites, including direct current (dc) and alternating current (ac) properties. ...
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There are described nanocomposites based on ultra high molecular weight polyethylene and graphite nanoplates prepared by in-situ polymerization method. It is carried out a comprehensive study of electric properties of these composites, including direct current (dc) and alternating current (ac) properties. There is explored dependence of the conductivity and dielectric permeability on filler concentration, temperature, deformation and frequency of electric field. These relationships are compared with those for composites based on other carbon fillers including both nanoscale (carbon nanotubes, carbon black) and micron-sized (graphite, schungite) fillers. More specific electrical properties of investigated materials such as lower percolation threshold and higher dielectric permittivity compared to those for composites based on other carbon fillers are attributed to the plate-like shape of graphite nanoplates. These materials are distinguished also by their high electrical stability against temperature and deformation. Therefore, it makes graphite nanoplates the most preferable conductive filler for some practical applications. Some possible application areas for UHMWPE/graphite nanoplates nanocomposites will be also discussed.
Structure and property relationship
Alireza Nikfarjam; Roham Rafiee; Mostafa Taheri
Abstract
Isolated carbon nanotubes (CNTs), CNT films and CNT-polymer nanocomposites are a new generation of materials with outstanding mechanical, thermal, electrical and electromagnetic properties. The main objective of this article is to provide a comprehensive review on the investigations performed in the ...
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Isolated carbon nanotubes (CNTs), CNT films and CNT-polymer nanocomposites are a new generation of materials with outstanding mechanical, thermal, electrical and electromagnetic properties. The main objective of this article is to provide a comprehensive review on the investigations performed in the field of characterizing electrical and electromagnetic properties of isolated CNTs and CNT-reinforced polymers either theoretically or experimentally. The results reported in literature are reviewed and evaluated based on employed and/or developed methods by focusing on the electrical conductivity, permittivity and permeability properties. Available analytical and numerical simulations for predicting electrical properties of CNT-based composites are also reviewed. Besides, equivalent circuit modeling of nanocomposites containing CNTs is presented. The influence of effective parameters on overall electrical and electromagnetic characteristics of CNT-reinforced polymers is discussed based on published data. Therefore, highlighting the recent trends and challenges engaged in new investigations, those aspects which are required to be more deeply explored are introduced.
Structure and property relationship
Fateme Khademeh Molavi; Sedigheh Soltani; Ghasem Naderi; Rohollah Bagheri
Abstract
A novel mixing approach for achieving a good dispersion of multi-walled carbon nanotubes (MWCNTs) in ethylene- propylene diene monomer (EPDM) matrix has been investigated. In this approach EPDM was modified with vinyltrimethoxysilane (VTMS) during melt mixing. In addition the effect of MWCNT concentration ...
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A novel mixing approach for achieving a good dispersion of multi-walled carbon nanotubes (MWCNTs) in ethylene- propylene diene monomer (EPDM) matrix has been investigated. In this approach EPDM was modified with vinyltrimethoxysilane (VTMS) during melt mixing. In addition the effect of MWCNT concentration on mechanical and rheological properties of modified EPDM has been studied. The formulated composites by this method exhibited significantly enhanced physical properties even at very low nanotube concentration. The grafting reaction was confirmed by Fourier transform infrared spectroscopy (FT-IR) peak at 1070 and 1250 cm-1according to Si-O and Si-C vibration. The state of dispersion of the fillers in the polymer matrix was evaluated through transmission electron microscopy (TEM) and scanning electron microscopy (SEM), In addition surface topology was studied with atomic force microscopy (AFM). The results showed that VTMS-grafted on the EPDM surface improved the dispersion of MWCNTs in the matrix. The rheological characteristics have been studied by rubber process analyzer (RPA). Some properties such as storage modulus (Ǵ) and complex viscosity (η^*) increased with increasing MWCNT content. It was found that at concentration of 2 wt.% MWCNT, the nanocomposites exhibited notably enhanced mechanical properties such as modulus and tensile strength.
Structure and property relationship
Ali Yadegari; Jalil Morshedian; Hossein-Ali Khonakdar; Udo Wagenknecht
Abstract
High density polyethylene (HDPE) films were produced using cast film extrusion process with different draw ratios, ranging from 16.9 to 148.8. Morphology, crystallinty and orientation state of crystalline and amorphous phases of the cast films were investigated using scanning electron microscopy (SEM), ...
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High density polyethylene (HDPE) films were produced using cast film extrusion process with different draw ratios, ranging from 16.9 to 148.8. Morphology, crystallinty and orientation state of crystalline and amorphous phases of the cast films were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and polarized Fourier transform infrared spectroscopy (FTIR) analyses, respectively. The anisotropic crystalline structures of row-nucleated lamellar morphology were observed for the films produced with high draw ratios. The crystalline phase axes orientation functions were found to be significantly dependent on the applied draw ratios. As expected, annealing increased the crystallinity and melting point temperature (Tm) of the cast films and on the other hand, it also enhanced the crystalline phase orientation. However, the results revealed that annealing also promoted non-twisted lamellar structures, since it increased fc values (c-axis orientation function) and decreased fa values (a-axis orientation function) simultaneously. Additionally, it was found that the annealing induced enhancement in c-axis orientation function was more significant for the cast films with lower draw ratios, therefore, it was dependent on the draw ratio.
Structure and property relationship
Jalil Morshedian; Yousef Jahani; Farshad Sharbafian; Foroogh Sadat Zarei
Abstract
HDPE monofilaments were obtained using different extruders and drawn by post-extruder equipments. After solidification, drawn and undrawn monofilaments (draw ratio 7:1) were irradiated with 10 MeV electron beams in air at room temperature at 25, 50, 75, 100 and 125 kGy dose ranges to induce a network ...
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HDPE monofilaments were obtained using different extruders and drawn by post-extruder equipments. After solidification, drawn and undrawn monofilaments (draw ratio 7:1) were irradiated with 10 MeV electron beams in air at room temperature at 25, 50, 75, 100 and 125 kGy dose ranges to induce a network structure. HDPE crosslinking was studied on the basis of gel content measurements. The fibers were examined by differential scanning calorimetry (DSC) and measurements of mechanical properties.It was noted that gel fraction increased with irradiation dose up to 75 kGy and showed a significant increase with draw ratio, but at higher doses remained without considerable change. Melting temperature of drawn fiber increased with raising irradiation dose but decreased in undrawn sample. Also a bimodal endotherm peak was observed for drawn polyethylene irradiated in air.The changes in melting temperature and appearance of bimodal endotherm were related to the radiation chemistry of polyethylene in the presence of oxygen and interlamellar interactions. Heat of fusion and degree of crystallinity slightly increased for undrawn and drawn samples but, heat of crystallization was reduced by increasing irradiation dose due to increase the degree of crosslinking. Results of mechanical properties reveal that no significant changes seen in Young’s modulus by increasing irradiation dose. As a result of oxidative degradation happened by presence the oxygen molecules during the irradiation process, tensile properties of irradiated fibers decreased but elongation at yield for undrawn and elongation at break for drawn fibers boosted by increasing irradiation dose up to 125 kGy.
Polyolefin degradation
Abbas Kebritchi; Mehdi Nekoomanesh; Fereidoon Mohammadi; Hossein Ali Khonakdar
Abstract
In this work, the role of comonomer content of 1-hexene-medium density polyethylene (MDPE) copolymer, synthesized using Phillips catalyst, on thermal behavior parameters such as: crystallization, melting temperature and thermal degradation was investigated in detail. The copolymer was fractionated to ...
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In this work, the role of comonomer content of 1-hexene-medium density polyethylene (MDPE) copolymer, synthesized using Phillips catalyst, on thermal behavior parameters such as: crystallization, melting temperature and thermal degradation was investigated in detail. The copolymer was fractionated to homogenous short-chain branching (SCB) fractions by "preparative temperature rising elution fractionation" (P-TREF) method and then it was subjected to thermal analyses. A broad chemical composition distribution (CCD) in terms of SCB content and molecular weight (Mw) was observed by P-TREF and gel permeation chromatography (GPC), respectively. Based on P-TREF results, a parabolic relationship between methylene sequence length (MSL) and elution temperature (ET) was presented. Differential scanning calorimetry (DSC) showed distinct, well-defined melting peaks over a 22 °C temperature range for SCB contents of about 3-12 (br/1000 C). The variations in physical characteristics such as melting temperature (Tm), crystallinity (Xc), crystallization temperature (Tc) and lamellae thickness (Lc) against SCB content were correlated. Thermogravimetric analysis (TGA) suggested linear relationships between the temperature at maximum degradation rate (Tmax) as well as the degradation initiation temperature (T5%) versus SCB content. Moreover, the TGA curves exhibited distinct differences at both initiation and propagation stages of thermal degradation at dissimilar comonomer contents.
Catalysis
Laura Boggioni; Incoronata Tritto
Abstract
Highly active metallocenes and other single site catalysts have opened up the possibility of polymerizing cycloolefins such as norbornene (N) or of copolymerizing them with ethene (E) or propene (P). The polymers obtained show exciting structures and properties. E-N copolymers are industrially produced ...
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Highly active metallocenes and other single site catalysts have opened up the possibility of polymerizing cycloolefins such as norbornene (N) or of copolymerizing them with ethene (E) or propene (P). The polymers obtained show exciting structures and properties. E-N copolymers are industrially produced materials, with variable and high glass transitions depending on the wide range of their microstructures. By realizing the possibility in great variety of stereoregularity of propene and norbornene units and the difference in comonomer distribution, P-N copolymers were expected to have fine tuned microstructures and properties. Moreover, P-N copolymers should be characterized by higher Tg-values than E-N copolymers with the same norbornene content and molar mass. A review of the state of the art of P-N copolymerization by ansa-metallocenes of C2 symmetry, namely rac-Et(Ind)2ZrCl2 (I-I) and rac-Me2Si(Ind)2ZrCl2 (I-II), and rac-Me2Si(2-Me-Ind)2ZrCl2 (I-III), and of catalysts of Cssymmetry, namely (tBuNSiMe2Flu)TiMe2 (IV-I) and derivatives, is given here. Special emphasis is given to microstructural studies of P-N copolymers, including stereo- and regioregularity of propene units as well as of comonomer distribution, stereoregularity of norbornene units, and the structure of chain end-groups. This information allows us to find a rationale for the catalytic activities and the copolymer properties.
