Structure and properties of blends of isotactic polypropylene with ethylene-propylene oil

The structure of blends of isotactic polypropylene with ethylene-propylene oil was studied by light and atomic force microscopy, X-ray diffraction, and DSC. It was shown that the blends are heterogeneous systems which contain semicrystalline PP and oil crystallizing at low temperatures. An increase in the oil content leads to a change in the spherulite size; a decrease in the lamella size; and, accordingly, to a drop in the melting temperature of PP. The PP-oil blends are thermodynamically compatible in melt. The mechanism of PP deformation gradually varies from the ductile to the quasi-brittle mode with a significant deterioration of mechanical characteristics of the material with an increase in the oil content. The experimental results are described satisfactorily by a model of deformation of the polymer matrix alone.     

Microporous membranes obtained from polypropylene blends with superior permeability properties

A blend of two polypropylene resins, different in molecular structure, one with linear chains and the other with long chain branches, was investigated to develop microporous membranes through melt extrusion (cast film process) followed by film stretching. The branched component significantly affected the row‐nucleated lamellar crystalline structure in the precursor films. The arrangement and orientation of the crystalline and amorphous phases were examined by wide angle X‐ray diffraction and Fourier transform infrared spectroscopy methods. It was found that blending of a small amount of a long chain branched polypropylene improved the orientation of the both crystalline and amorphous phases in the precursor films. Annealing, followed by cold and hot stretching were consequently employed to generate and enlarge pores in the films as a result of lamellae separation. SEM micrographs of the surface of the membranes obtained from the blend revealed elongated thin fibrils and a large number of lamellae. The lamellae thickness for the blend was much shorter in comparison to that of the linear PP precursor film. The permeability of the samples to water vapor and N₂ was significantly enhanced (more than twice) for the blend system. The porosity of the blend membrane showed a significant improvement with a value of 53% compared to 41% for the linear PP membrane. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 148–157, 2008     

Morphology and electrical breakdown properties of LDPE‐polypropylene copolymer blends

In this study, the specimens of low‐density polyethylene (LDPE) and blend polymers of LDPE and a random copolymer of ethylene and propylene were prepared by the blowing process and T‐die method. The differences in electrical breakdown properties and morphology between the specimens made by the two different methods were studied. It was found that the specimen made by the T‐die method had a higher electrical breakdown strength than the specimen made by the blowing process, except for the DC breakdown strength in some cases at 30 °C. The morphology of the specimens was investigated by means of the measurements of thermal shrinkage, infrared dichroism, and X‐ray diffraction. The specimen made by the T‐die method has a stronger orientation in both the crystalline and amorphous phases than the specimen made by the blowing process. The difference in morphology is supposed to be correlated with the difference in electrical breakdown properties between the specimens made by the two different methods. It was concluded that the electrical breakdown properties are strongly affected by the orientation of chains in the specimen. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1741–1748, 2001     

Effect of biopolymer blends on physical and Acoustical properties of biocomposite foams

Bio‐based foams are the solution to environmental concerns raised by petrochemical‐based open cell foams used in various industries for sound absorption. While conventional petrochemical‐based polymers take centuries to degrade or may not degrade at all, bio‐based polymers decompose to biomass, water, and carbon dioxide in a matter of months when exposed to proper environment. To increase the potential of replacing current petrochemical foams, mechanical as well as acoustic characteristics of bio‐based foams need to be improved. This article studies the effect of blending two bio‐based polymers and physics of the blends on acoustic and mechanical properties of resulting polymer composite foams. Different blends of polylactide with three grades of polyhydroxyalkanoates were foamed and characterized based on acoustic and mechanical performance. Rheological properties of pure polymers as well as their blends were studied and effect of polymer blends on acoustic absorption of the resulting foams was investigated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1002–1013     

Influence of chitosan and epoxy cross-linking on physical properties of binary blends

In this study, blends of chitosan (Cs) and bisphenol-F-diglycidyl ether (3.80 × 10^?3 to 3.80 × 10^?2 mol) were cast by the solution route. FT-IR results suggested that chitosan was cross-linked at terminal amino groups through diepoxide linkage. The chitosan films became less flexible and stiffer upon reaction with epoxy. Blending improved percentage elongation (31%) and toughness (10 MPa), whereas Young’s modulus (145 MPa) and tensile strength (45 MPa) were decreased. Extent of weight loss in Cs/BPFDGE was lower (15%) than that of original precursors (chitosan 33%). Moreover, blending of chitosan with BPFDGE increased water absorption properties due to generation of hydrophilic ?OH groups.     

Plasma modification of polypropylene surfaces and grafting copolymerization of styrene onto polypropylene

The surface of polypropylene(iPP) is modified with glow discharge plasma of Ar,so that the modified surfaces of iPP films are obtained.The studies of scanning electron microscopy(SEM) show the surface etching pattern of iPP films. The chemical structures of iPP films are confirmed by X-ray photoelectron spectroscopy(XPS) and Fourier transform infrared(FTIR) spectroscopy.The wetting properties of modified surfaces of iPP films are characterized by contact angle, and the free energy of surfaces is calculated.The free radical of modification surfaces of iPP is measured by chemical method.The surfaces of iPP are achieved with Ar plasma treatment followed by grafting copolymerization with styrene(St) in St.The grafting polymer of St onto iPP is characterized by FTIR.The grafting rate is dependent on plasma exposure time and discharge voltage.The studies show that homopolymerization of St is undergone at the same time during the grafting-copolymerization of St onto iPP.     

Investigations on structure and properties of blends of polypropylene with polyamide 1010 by Rayleigh scattering

The phase structure and morphology of polypropylene （iPP） blends with poly（decamethylene sebacamide （polyamide 1010, PA 1010） and the part-compatible alloys （iPP/PA 1010/iPP-g-MAH） are investigated by Rayleigh scattering, i.e. small angle light scattering （SALS）. The structure parameters of SALS, i.e. correlation distance, ac and average chord lengths, /, are calculated. Their variation with the composition of the blends and alloys is discussed. The morphology and structure of fracture surfaces in the blends and alloys are studied by SEM images. The average diameter of dispersed phase in the blends and alloys is calculated by graph processing. The variation of average diameter is similar as that of average chord lengths of dispersed phases. The mechanical properties of the blends and alloys are analyzed and the relation of modulus and yield stress with the composition is studied. It is confirmed that the correlation between the modulus and the structure parameters is non-linear, while the correlation between the yield stress and the composition or structure parameters is linear.     

Specifics of the structure and mechanical properties of blends of isotactic polypropylene with ethylene-propylene-diene elastomer

The structure of unvulcanized and dynamically vulcanized blends of isotactic PP with ethylene-propylene-diene terpolymer (EPDM) having an EPDM content of 5–85 wt % was studied by means of atomic force microscopy. The systems based on the virgin elastomer and the elastomer plasticized with 50% oligomer were examined. During thermal treatment (molding), the structure of the unvulcanized materials undergoes substantial changes. The morphology of dynamically vulcanized blends containing up to 75 wt % rubber is characterized by a homogeneous distribution of crosslinked rubber particles with a particle size of less than 2 μm in the continuous thermoplastic matrix. During PP blending with the plasticized elastomer, the oligomer diffuses into the thermoplastic phase, with the oligomer being distributed evenly between the blend components. As a result, the stress-strain characteristics of the plasticized systems decline relative to those of the oligomer-free materials. A comparative analysis of the dependence of the elastic modulus on the composition of the blends with the theoretical values obtained in terms of the Kerner, Uemura-Takayanagi, Davies, and Coran-Patel models was performed.     

Electrical properties and conductive mechanisms of immiscible polypropylene/Novolac blends filled with carbon black

Carbon black (CB)-filled immisicible thermoplastic/thermosetting polymer blends consisting of polypropylene (PP) and Novolac resin were reported in this paper. The PP/Novolac/CB blends with varied compositions and different processing sequences were prepared by melt-mixing method. The CB distribution, conductive mechanism and the relationship between morphology and electrical properties of the PP/Novolac/CB blends were investigated. Scanning electron microscopy (SEM), optical microscopy and extraction experiment results showed that in PP/Novolac blends CB particles preferentially localized in the Novolac phase, indicating CB has a good affinity with Novolac resin. The incorporation of CB changed the spherical particles of the dispersed Novolac phase into elongated structure. With increasing Novolac content, the elongation deformation of Novolac phase became more obvious and eventually the blends developed into co-continuous structure, which form double percolation and decrease the percolation threshold. When CB was initially blended with PP and followed by the addition of Novolac resin, the partial migration of CB from PP to the Novolac phase was possibly occurred. The addition of Novolac to PP evidently increases the storage modulus G′, loss modulus G″ and complex viscosity η^∗. The addition of CB to PP/Novolac blends further increase η^∗, and it increases with increasing CB loading, which was related to the change of composite morphology.     

Main-chain side-chain liquid crystal polymer blends for improved physical properties

Previous work has demonstrated that compatible blends of main-chain liquid crystal polymers (LCP) with side-chain LCP's can be prepared. The present work was carried out to extend the scope and application of this finding to liquid crystal polyesters, similar to commercially available LCP's and to demonstrate the effect of the blend composition upon the physical and mechanical properties. A series of melt-processable main-chain polyesters was prepared as well as a series of acrylic polymers and copolymers which possess a side-chain mesogenic unit, similar to that of the main-chain LCP's. While the results of the blending studies of these high molecular weight materials were somewhat ambiguous as to compatibility, there are strong indications that the presence of the side-chain mesogen containing polymers does result in an improvement in the overall mechanical properties of the main-chain LCP.     

Structure and mechanical properties of talc‐filled blends of polypropylene and styrenic block copolymers

The structure–property relationships of isotactic polypropylene (iPP)/styrenic block copolymer blends filled with talc were examined by optical and scanning electron microscopy, wide‐angle X‐ray diffraction, and tensile‐ and impact strength measurements. The composites were analyzed as a function of the poly(styrene‐b‐ethylene‐co‐propylene) diblock copolymer (SEP) and the poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (SBS) content in the range from 0 to 20 vol % as elastomeric components and with 12 vol % of aminosilane surface‐treated talc as a filler. Talc crystals incorporated in the iPP matrix accommodated mostly plane‐parallel to the surface of the samples and strongly affected the crystallization process of the iPP matrix. The SBS block copolymer disoriented plane‐parallel talc crystals more significantly than the SEP block copolymer. The mechanical properties depended on the final phase morphology of the investigated iPP blends and composites and supermolecular structure of the iPP matrix because of the interactivity between their components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1255–1264, 2004     

Morphology of nylon 6/polypropylene blends compatibilized with maleated polypropylene

Transmission electron microscopy (TEM) was used to examine the morphology of blends of nylon 6 and polypropylene (PP) containing various maleated polypropylenes (PP-g-MA). The size of the dispersed polypropylene particles decreases as the content of maleic anhydride in the PP-g-MA increases for binary blends of nylon 6 and the maleated polypropylenes. Ternary blends of nylon 6, PP, and PP-g-MA show morphologies that depend on the content of maleic anhydride of the PP-g-MA and on the miscibility of PP and PP-g-MA. Blends where PP and PP-g-MA are immiscible show a bimodal distribution of particle sizes. Miscibility of the PP and PP-g-MA was determined by TEM using a special staining technique. Experimental observations of miscibility were further corroborated by thermodynamic calculations. The morphology of the ternary blends was also found to be dependent on the ratio of PP/PP-g-MA. By changing this ratio it was possible to induce drastic changes of morphology, going from a continuous nylon 6 phase to a continuous PP phase at a fixed composition. The mechanical properties of these blends were found to be dependent on their morphology. ©1995 John Wiley & Sons, Inc.     

Characterization of the dynamic properties of binary polypropylene blends via the hysteresis measurement method

Due to the poor impact behavior of polypropylene (PP) at low temperatures, blending PP with an elastomeric phase is a common way to improve some of the characteristic quantities. The property profile of thermoplastic elastomers strongly depends on the content of the elastomeric component. For applications under dynamic loading conditions, the corresponding material behavior is of importance. In order to reduce long testing times with constant amplitude loading, the hysteresis measurement method, which evaluates the hysteresis loop and makes use of a stepwise load increase procedure (SLIP), was developed. Binary blends based on PP were compounded with either ethylene-propylene-dien-rubber (EPDM), metallocene polymerized polyethylene (mPE), or styrene-ethylene-butylene-styrene block copolymer (SEBS) as the elastomeric phase. Static and dynamic tests under tensile and pressure conditions were performed in order to evaluate the influence of the type of elastomeric phase on the properties of these blends. It is shown how the hysteresis measurement method can be used to determine dynamic load limits for the application of these blends and of other polymers. Some properties improved slightly when using mPE.     

Crystallization behavior of polypropylene/polycarbonate blends

Crystallization behavior and morphology of polypropylene (PP)/polycarbonate (PC) blends have been studied by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). In the study of non-isothermal crystallization of the blends, the phenomenon of multiple crystallization peaks of PP/PC blends was related to the blend morphology in which PP was the dispersed phase as small droplets in the PC matrix. The phenomenon of a single crystallization peak of the PP/PC blends was related to the blend morphology in which PP was a continuous phase; in that case the crystallization peak temperatures of the blends were higher than that of the PP. The isothermal crystallization kinetics of the PP and PP/PC (80/20) blend were described by the Avrami equation. The results showed that the Avrami exponent of the PP/PC (80/20) blend was higher than that of the PP, and the crystallization rate of the PP/PC (80/20) blend was faster than that of the PP. The crystallization rate of the PP and PP/PC (80/20) blend were calculated according to the Hoffmann theory. Both the PP and PP/PC (80/20) blend had maximum crystallization rates. The temperature at the maximum crystallization rate for the PP/PC (80/20) blend was higher than that of the PP.     

Photoinitiated grafting of maleic anhydride onto polypropylene

The photoinitiated grafting of maleic anhydride (MAH) onto polypropylene with the use of benzophenone (BP) as the initiator has been investigated. In comparison with the process of thermally initiated grafting with peroxide as the initiator, photoinitiated grafting affords a higher grafting efficiency. The efficient photografting sensitized by BP can be explained by two possible mechanistic processes: the sensitization of the formation of the excited triplet state of MAH by BP and electron transfer followed by proton transfer between MAH and the benzopinacol radical, which may operate together. In the former case, the generated MAH excited triplet state abstracts a hydrogen from the polymer substrate to initiate grafting. A rate constant of 3.6 × 10⁹ M ^?1 s ^?1 has been determined by laser flash photolysis for the process of quenching the excited triplet state of BP with ground‐state MAH. In comparison, the rate constant for the quenching of the excited triplet state of BP by hydrogen abstraction has been determined to be 4.1 × 10⁵ M ^?1 s ^?1. In a study of photografting using a model compound, 2,4‐dimethylpentane, as a small‐molecule analogue of polypropylene, the loss of BP was significantly reduced upon the addition of MAH, and this is consistent with the proposed mechanistic processes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1953–1962, 2004     

Phase morphology, crystallisation behaviour and mechanical properties of isotactic polypropylene/high density polyethylene blends

The phase morphology, crystallisation behaviour and mechanical properties of isotactic polypropylene (iPP)/high density polyethylene (HDPE) blends were investigated. It was found that the properties are intimately related to each other. The morphology of the blends showed a two phase structure in which the minor phase was dispersed as domains in the major continuous matrix phase. The domain size of the dispersed phase increased with increasing concentration of that phase due to coalescence. It was also found that the domain size of the dispersed phase depends on the viscosity difference between the two phases. For a given HDPE/iPP blend, where HDPE is the matrix and iPP is the dispersed phase, the iPP domains were smaller than HDPE domains of the corresponding iPP/HDPE blend where iPP is the matrix and HDPE is the dispersed phase. A co-continuous morphology was observed at 50/50 PP/HDPE composition. Crystallinity studies revealed that blending has not much effect on the crystalline melting point of polypropylene and high density polyethylene. The crystallisation enthalpy and heat of fusion values of HDPE and PP in the blend were decreased as the amount of the other component increased. The variation in percent crystallinity of HDPE and PP in the blend was found to depend on the morphology of the blend. All the mechanical properties except Young's modulus and hardness showed negative deviation from the additivity line. This is due to the incompatibility of these blends.     

The rheological,thermal, and mechanical properties for polypropylene and amorphous poly alpha olefin blends

Rheological, thermal, and mechanical properties of polypropylene homo polymer (PPH)/amorphous poly alpha olefin (APAO) blends as a function of molecular weight, comonomer type and content, and blend composition have been investigated. Homo APAO grade showed better compatibility than copolymerized ones in terms of rheological and thermal properties. The mechanical strength showed strong dependence on APAO content and type, and the impact strength and melt index rapidly increased for certain types of APAO at and above 30 wt%. On comparison with commercially used PPH/ethylene–propylene rubber (EPR) blend system, it is supposed that PPH/APAO blend can be successfully used in thermoplastic polyolefin applications. Copyright © 2007 John Wiley & Sons, Ltd.     

Crystallization kinetics of compatibilized blends of polypropylene and polyethylenimine

Journal of Thermal Analysis and Calorimetry - In this paper, isothermal and non-isothermal crystallization behaviour of neat polypropylene (PP), blends of PP/maleic anhydride grafted polypropylene...     

Mechanical properties and characterization of slowly cooled isotactic polypropylene/high‐density polyethylene blends

In previous studies, we found that Young's moduli of quenched isotactic polypropylene/high‐density polyethylene (iPP/HDPE) exceeded the upper bound, calculated from the Voigt model, with the moduli of the quenched homopolymers as those of the two components. We suggested that this might be due to crystallization, as the components crystallized at higher temperatures in the blend than on their own. We repeated the same set of measurements, this time on iPP/HDPE blends that were cooled slowly. We also examined crystallization at various rates of cooling with differential scanning calorimetry. At slow cooling rates, the HDPE and iPP components in the blends crystallize at lower temperatures than in the pure homopolymers, suggesting that the presence of one component inhibits rather than promotes the crystallization of the other. Electron microscopy of slowly cooled blends revealed very different interfacial morphologies depending on whether the HDPE or the iPP crystallizes first. Young's moduli of most of the blends lie on the upper bound; however, some blends with co‐continuous morphologies fall well below the lower bound. The mechanical properties are discussed in terms of the interfacial morphology, the crystallization behavior, and the large‐scale phase separation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1384–1392, 2003     

Effects of grafting level and nano-clay loading on the properties of cured NR/PVA blends

Abstract

The primary objective of this study is to improve the properties of NR/PVA blend which is cured using glutaraldehyde at low temperature. PMMA grafted on to NR with different grafting levels has been prepared and confirmed the grafting reaction by TEM, FT-IR and ¹H-NMR. The effect of PMMA contents on NR with 1 phr of nano-clay on the mechanical properties and thermal stability has also been investigated. Significant enhancement in mechanical and thermal stability of the blends with higher grafting level on NR is observed. Activation energy of degradation has been determined from TGA curves by using the Horowitz-Metzger equation. The nature of dispersion and surface morphology has been studied using SEM-EDX technique. The experimental results reveal that the properties can be improved by adding functional group (i.e. PMMA) onto NR molecule.