Toughness Of Blends Research Articles

Preparation and Properties Research of PA6/PLA Blends Toughening Modified by TPU

Polyamide 6/Poly(lactic acid) (PA6/PLA) blends introduce the degradability of PLA to high performance PA6, but the bad toughness of both PA6 and PLA limits the application of blends. Aiming at this deficiency, thermoplastic polyurethane (TPU) was used as an additive for modifying the toughness of PA6/PLA blends. PA6/PLA/TPU blends at various compositions were prepared by melt blending, the effects of blend compositions on the morphology, thermal and mechanical properties of blends were investigated. The results showed that the addition of TPU improves the compatibilization between PA6 and PLA and makes the blends show more obvious plastic fracture behavior than PA6/PLA.When the content of PLA in PA6/PLA increases, the impact and tensile strength of blends decrease slightly with the intense decrease of the elongation at break, adding TPU into PA6/PLA blends strengthens the toughness of blends, but the tensile strength of blends decreases. Moreover, the crystallinity of PA6 /PLA blend is hampered by TPU.

Morphology and Mechanical Properties of PA6/ABS Blends

The toughness of blends composed of PA6 and acrylonitrile-butadiene-styrene (ABS) compatibilized by using styrene-maleic anhydride (SMA) as a compatibilizer was measured over a wide temperature region. The addition of SMA results in a significant increase of the PA6 phase viscosity due to the in situ formation of graft polymers during the melt processing, and the significant change in viscosity ratio between the PA6 and ABS due to the formation of SMA-g-PA6 graft polymer may be prevent the coalescence of the dispersed phase. All results in this paper were consistent, and showed the good interaction between PA6 and ABS, which were proved by the morphology and mechanical properties of the blends.

Improvement of compatibility of poly(ethylene terephthalate) and poly(ethylene octene) blends by γ‐irradiation

AbstractBlends of poly(ethylene terephthalate) (PET) and poly(ethylene octene) (POE) were prepared by melt blending with various amounts of trimethylolpropane triacylate (TMPTA). The mechanical properties, phase morphologies, and gel fractions at various absorbed doses of γ‐irradiation have been investigated. It was found that the toughness of blends was enhanced effectively after irradiation as well as the tensile properties. The elongation at break for all studied PET/POE blends (POE being up to 15 wt %) with 2 wt % TMPTA reached 250–400% at most absorbed doses of γ‐irradiation, approximately 50–80 times of those of untreated PET/POE blends. The impact strength of PET/POE (85/15 wt/wt) blends with 2 wt % TMPTA irradiated with as little as 30 kGy absorbed dose exceeded 17 kJ/m2, being approximately 3.4 times of those of untreated blends. The improvement of the mechanical properties was supported by the morphology changes. Scanning electron microscope images of fracture surfaces showed a smaller dispersed phase and more indistinct inter‐phase boundaries in the irradiated blends. This indicates increased compatibility of PET and POE in the PET/POE blends. The changes of the morphologies and the enhancement of the mechanical properties were ascribed to the enhanced inter‐phase boundaries by the formation of complex graft structures confirmed by the results of the gelation extraction and Fourier Transform Infrared analyses. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Effect of EVOH on the morphology, mechanical and barrier properties of PA6/POE-g-MAH/EVOH ternary blends

Polyamide 6 (PA6)/maleated poly(ethylene-1-octene) (POE-g-MAH) blends with various ethylene–vinyl alcohol (EVOH) concentrations were prepared via melt-blending. The morphology, mechanical and barrier properties of the blends were investigated in terms of scanning electron microscope (SEM), impact/tensile testing, dynamic mechanical analysis (DMA) and oil absorption rate. The SEM images indicated that the compatibility between PA6 and POE-g-MAH was improved significantly after the incorporation of EVOH. The toughness of blends was correlated with the morphology of the POE-g-MAH and EVOH dispersion phase. It has also demonstrated that the incorporation of EVOH increased evidently the tensile strength, storage modulus and barrier properties, which were contributed to the strong interactions formed through the reaction among PA 6, POE-g-MAH and EVOH.

Compatibilization of recycled poly(ethylene terephthalate) and polypropylene blends: Effect of compatibilization on blend toughness, dispersion of minor phase, and thermal stability

AbstractBlending of recycled polyethylene terephthalate (RPET) from waste bottles with polypropylene (PP) was performed in an attempt to enhance the processability of RPET. The idea of blending RPET with PP sprouted from the intention of recycling PET bottles together with their PP‐based caps. Therefore, preliminary blending of RPET with neat PP (RPET/PP) was performed at various PP and compatibilizer contents. Morphological analyses on the extruded pellets of uncompatibilized blends indicate that the PP particle size and state of dispersion at skin and core regions were vastly different. The particles at the skin were at least 10 times smaller than that at the core although the size distribution was very wide. With the incorporation of just 5 phr of compatibilizer, the particles at the core region became significantly smaller and appeared to emulate that of the skin region. Furthermore, the overall homogeneity of the blends was vastly improved irrespective of PP content in the blend. The reduction in particle size and improved homogeneity inherently reduced stress concentration points and enhanced the mechanical performance of the blends. More importantly, the incorporation of PP into RPET significantly increased the degradation temperature of the blends, provided the dispersion of PP phase in RPET was excellent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Tough Blends of Polylactide and Castor Oil

Poly(l-lactide) (PLLA) is a renewable resource polymer derived from plant sugars with several commercial applications. Broader implementation of the material is limited due to its inherent brittleness. We show that the addition of 5 wt % castor oil to PLLA significantly enhances the overall tensile toughness with minimal reductions in the modulus and no plasticization of the PLLA matrix. In addition, we used poly(ricinoleic acid)-PLLA diblock copolymers, synthesized entirely from renewable resources, as compatibilizers for the PLLA/castor oil blends. Ricinoleic acid, the majority fatty acid comprising castor oil, was polymerized through a lipase-catalyzed condensation reaction. The resulting polymers contained a hydroxyl end-group that was subsequently used to initiate the ring-opening polymerization of l-lactide. The binary PLLA/castor oil blend exhibited a tensile toughness seven times greater than neat PLLA. The addition of block copolymer allowed for control over the morphology of the blends, and even further improvement in the tensile toughness was realized-an order of magnitude larger than that of neat PLLA.

Determination of Size Distribution of Dispersed Nanophases and Spaces among them in PVC/MBS Blends by TEM Image Analysis

The size of dispersed nanophases and spaces among them are important factors effeted on toughness of plastic-rubber blends. In order to determine the size distribution of dispersed nanophases and spaces among them, a quantitative method was established by image analysis and transmission electron microscopy of ultra-thin PVC/MBS slices stained by OsO4. Two PVC/MBS blends samples were determined.

Particle Interaction Effects on Interfacial Stress in Extension of Rubber-Toughened Polypropylene

Polypropylene (PP) toughened with rubber particles is extensively used in polymer industry. Strength or toughness of polymer blends and polymer composites depends, to a great extent, upon their interfacial stress state. A finite element analysis of interfacial stress and its distribution during extension of PP/rubber blends was made by means ANSYS software, to investigate the effects of interaction between neighboring rubber particles on the interfacial stress and its distribution during extension of toughening PP. The simulation results showed that there was obvious stress concentration between rubber particles, especially around the equator zone of the rubber particles. Large shear stress presented at about 45 degrees between the surface and the equator of the rubber particles, and it was symmetry. The pressed and pulled effect subjected by the pole zone of the rubber particles was maximal. Furthermore, the variation extent of the interfacial stress between the particle and the matrix increased with an increase of the particle number.

The effect of montmorillonite and compatibilizer quantities on stiffness and toughness of polyamide nanoblends

AbstractAlthough polymer blend nanocomposites are widely studied, the balance between stiffness and toughness has not yet been investigated in detail. Some materials producers as well as some sectors in the automotive industry try to improve the toughness of materials without an important loss in stiffness. With this in mind, the aim of the study reported here was to obtain a good balance between toughness and stiffness of polymer blends with different amounts of clay and compatibilizer. In this context, the microstructure of polyamide 6/ethylene–propylene–diene metallocene terpolymer/(ethylene–propylene–diene copolymer)‐graft‐(maleic anhydride) blends with various amounts of clay (2, 3, 4 and 5 wt%) and compatibilizer (10 and 20 wt%) was studied to analyse the achieved morphology to understand the macroscopic properties. The morphology of the rubber phase and the dispersion of the montmorillonite (MMT) are the main factors that influence the mechanical properties. In this sense, the highest Young's modulus is achieved for nanoblends with 5 wt% of MMT, although this nanoblend has the lowest value of notched Izod impact strength. The results obtained suggest that there is a clear trade‐off between stiffness, toughness and temperature behaviour when the ratio of (ethylene–propylene–diene copolymer)‐graft‐(maleic anhydride) to MMT is 5:1. Copyright © 2009 Society of Chemical Industry

The Structure and Thermomechanical Properties of Blends of Trans-polyisoprene with Cis-polyisoprene

The present work reports the structural and thermomechanical properties of cis- and trans-polyisoprene blends. These blends have been prepared using the solution casting method. The effect of blending on thermomechanical properties such as glass transition temperature, damping and storage modulus and mechanical properties such as toughness, elastic modulus, tensile strength and elongation of present blends has been studied. Besides these, the effect of blending on structure has also been studied. It was observed that elastic moduli, tensile strength and toughness of the TPI/CPI blends decreases with increased CPI percentage. The study also presents a relation between Tg and crystallinity.

Comparison of olefin copolymers as compatibilizers for polypropylene and high‐density polyethylene

AbstractSome polyolefin elastomers were compared as compatibilizers for blends of polypropylene (PP) with 30 wt % high‐density polyethylene (HDPE). The compatibilizers included a multiblock ethylene–octene copolymer (OBC), two statistical ethylene–octene copolymers (EO), two propylene–ethylene copolymers (P/E), and a styrenic block copolymer (SBC). Examination of the blend morphology by AFM showed that the compatibilizer was preferentially located at the interface between the PP matrix and the dispersed HDPE particles. The brittle‐to‐ductile (BD) transition was determined from the temperature dependence of the blend toughness, which was taken as the area under the stress–strain curve. All the compatibilized blends had lower BD temperature than PP. However, the blend compatibilized with OBC had the best combination of low BD temperature and high toughness. Examination of the deformed blends by scanning electron microscopy revealed that in the best blends, the compatibilizer provided sufficient interfacial adhesion so that the HDPE domains were able to yield and draw along with the PP matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of EVM/EVA‐g‐MAH ratio on the structure and properties of nylon 1010 blends

AbstractThe nylon 1010/ethylene‐vinyl acetate rubber (EVM)/maleated ethylene‐vinyl acetate copolymers (EVA‐g‐MAH) ternary blends were prepared. The effect of EVM/EVA‐g‐MAH ratio on the toughness of blends was examined. A super tough nylon 1010 blends were obtained by the incorporation of both EVM and EVA‐g‐MAH. Impact essential work of fracture (EWF) model was used to characterize the fracture behavior of the blends. The nylon/EVM/EVA‐g‐MAH (80/15/5) blend had the highest total fracture energy at a given ligament length (5 mm) and the highest dissipative energy density among all the studied blends. Scanning electron microscopy images showed the EVM and EVA‐g‐MAH existed as spherical particles in nylon 1010 matrix and their size decreased gradually with increasing EVA‐g‐MAH content. Large plastic deformation was observed on the impact fracture surface of the nylon/EVM/EVA‐g‐MAH (80/15/5) blend and related to its high impact strength. Then with increasing EVA‐g‐MAH proportion, the matrix shear yielding of nylon/EVM/EVA‐g‐MAH blends became less obvious. EVM and EVA‐g‐MAH greatly increased the apparent viscosity of nylon 1010, especially at low shear rates. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 877–887, 2009

EFFECTS OF INTERPARTICLE DISTANCE, TEMPERATURE AND INTERFACIAL ADHESION ON BRITTLE-DUCTILE TRANSITION FOR NYLON 6/ABS BLENDS

The toughness of blends composed of nylon 6 and acrylonitrile-butadiene-styrene (ABS) compatibilized by using styrene-maleic anhydride (SMA) as a compatibilizer was measured over a wide temperature region. Results reveal that the combining effects of particle size and volume fraction of ABS on the toughness of nylon 6/ABS/SMA blends can be described through plotting brittle-ductile transition of the impact strength versus the interparticle distance (ID) on the assumption that ABS domains relieve the triaxial tension via internal cavitation or interfacial debonding. Moreover, the effect of interfacial adhesion on fracture behavior of nylon 6/ABS/SMA blends strongly depends upon the testing temperature. The difference of relation amomg temperature, fracture behavior and interfacial adhesion can be understood in terms of the deformation mechanisms, i.e. in the case of poor interfacial adhesion, the toughness lies on whether debonding existing at the interface relieves triaxial tension or not. It is believed ...

Nucleating agent induced impact fracture behavior change in PP/POE blend

This work was focused on the impact fracture behavior of polypropylene/ethylene-octene copolymer (PP/POE) blends with and without nucleating agent (NA). The crystallization morphologies of injection-molded-bar were analyzed by polarization optical microscope and the impact-fractured surface morphologies were characterized carefully through scanning electronic microscope. Our results show that the addition of 0.2 wt% α/or β-NA induces the great decrease of spherulites diameters companioned with the dramatically enhancement of PP/POE blend toughness. Virgin PP shows the typical brittle-fractured characteristic during the whole fracture process. PP/POE shows the less-ductile fracture feature with multiple-craze formation. The addition of NA into PP/POE blend changes the fractured surface feature from predominantly multiple-craze to predominantly shear yielding or shear yielding involving materials cavitations and second-crack re-initiation, respectively, indicating the change from brittle-like fracture mode to ductile fracture mode. The transformation of β → α during the impact process for β-NA nucleated samples has been observed; however, such transformation is suppressed by the presence of POE.

Influence of impact load‐temperature conformity on toughening of poly(vinyl chloride) by core‐shell rubber particles

AbstractThe work focused on the elucidation of several key parameters in toughening poly(vinyl chloride) (PVC) by the methyl methacrylate–butadiene–styrene (MBS) core‐shell particles. Accordingly, blends containing various weight percent of the MBS particles were prepared and characterized by dilute solution viscometry, dynamic light scattering, dynamic mechanical thermal analysis, transmission electron microscopy, and temperature variable impact test. The results showed PVC/MBS solution miscibility in almost all compositions with their maximum thermodynamic affinities at about 17 and 67 wt % of MBS in tetrahydrofurane (THF). In addition, MBS weight percent increase in its blend with the PVC above 10 led to severe impact energy raise with eventual leveling at about 17 wt %. Furthermore, blend toughness and its components miscibility in solution increased in parallel up to 20 wt % of MBS particles. On the other hand, blend toughness declined with test temperature decrease toward impact modifier core Tg at about −30°C even for the sample with 20 wt % of the MBS particles. Finally, the brittle‐ductile transition of the blend containing 20 wt % of the MBS particles comparison with its matrix tan δ‐temperature correlation implied 2500 J/m impact energy equivalence with 90°C sample temperature rise in secondary relaxation activation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Preparation and characterization of chitosan/poly(vinyl alcohol) chemically crosslinked blends for biomedical applications

In this study the development and characterization of novel polymer blends based on chitosan and poly(vinyl alcohol) and chemically crosslinked by glutaraldehyde for possible use in a variety of biomedical applications is reported. Mechanical properties of hybrids were evaluated by stress–strain tensile tests. Also, the microstructure, morphology and crystallinity of the blended hydrogels were characterized through X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy analysis. Moreover, biocompatibility, cytotoxicity and cell viability were also performed by swelling test in simulated body fluid, MTT assay with cell culture. The relative crystallinity of pure chitosan film was reduced from approximately 23% to 18% when the polymeric network was reticulated by glutaraldehyde. A similar trend was also observed for PVA films. It was found that by increasing the chitosan content relative to PVA the swelling index of the blend has decreased from about 200% (pure PVA) to approximately 80% (50/50 chitosan/PVA), reflecting the reduction in the mobility of the polymer network and the hydrophilic behavior of the blend. The mechanical properties of the polymers were also significantly altered by changing blend composition and chemical crosslinking. Chitosan films have shown values of 50 MPa and 45% for maximum tensile strength and tensile elongation, respectively. It was verified that the average blend toughness has decreased about 40% by increasing the chitosan concentration from 25% (14.8 MJ/m 3) to 50% (8.9 MJ/m 3) related to a brittle characteristic of chitosan. In addition, the obtained results of elastic moduli were 0.1 GPa for PVA and 0.8 GPa for chitosan. The tested hydrogels clearly show adequate cell viability, non-toxicity and suitable mechanical properties which can be tailored to for potential use in skin engineering applications.

Polymer toughening using residue of recycled windshields: PVB film as impact modifier

In this work, poly(vinyl butyral) (PVB) film originated from the mechanical separation of windshields was tested as an impact modifier of Polyamide-6 (PA-6). The changes undergone by PVB film during the recycling process and the blend manufacturing were evaluated by thermal analyses, infrared spectroscopy and loss on ignition. Blends of PA-6/original PVB film and PA-6/recovered PVB film were obtained in concentrations ranging from 90/10 to 60/40. The mechanical properties of the blends were investigated and explained in light of the blends morphologies, which in turns were correlated to the changes undergone by the PVB film during the recycling process. The original film presented a plasticizer content of 33wt.%, which decreased to as low as 20wt.% after the recycling and blend preparation processes. The PA-6/PVB film blends presented lower values of tensile strength and Young’s modulus than Polyamide-6, but all blends presented a dramatic increase in their toughness, with a special feature for the 40wt.% blend, which resulted in a super toughened material (impact strength exceeding 500J/m). Similar results were obtained with recovered PVB film and super tough blends were also obtained. The use of recovered PVB resulted in a smaller improvement of the impact strength due to the loss of plasticizer undergone during the recycling process. The morphological observations showed that if the interparticle distance is smaller than around 0.2μm (critical value), the notched Izod impact strength values increase considerably and the fracture surface of blends exhibit characteristics of tough failure.

Fully biodegradable poly(3-hydroxybutyrate-co-hydroxyvalerate)/poly(ethylene succinate) blends: Phase behavior, crystallization and mechanical properties

Poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(ethylene succinate) (PES) are both biodegradable semicrystalline polyesters. Phase behavior, crystal structure, crystallization kinetics, and mechanical properties of fully biodegradable PHBV/PES blends were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), wide angle X-ray diffraction (WAXD), and tensile tests in detail. PHBV is immiscible with PES as evidenced by the two composition independent glass transition temperatures corresponding to those of neat components. Moreover, the biphasic melt further confirms the immiscibility between PHBV and PES. Nonisothermal and isothermal crystallization of PHBV/PES blends were studied by DSC. In the case of isothermal crystallization the crystallization rates of PHBV and PES decrease with increasing the content of the other component for both PHBV-rich and PES-rich blends; however, the crystallization mechanisms do not change. The mechanical properties of PHBV/PES blends were examined by tensile testing. It is found that the tensile strength, elongation at break, Young’s modulus, and toughness of PHBV blends can be adjusted by changing blend composition. For PHBV-rich blends, blending some amount of PES can improve the elongation at break significantly while still keeping considerably high tensile strength and Young’s modulus.

Effects of olefin‐based compatibilizers on the morphology, thermal and mechanical properties of ABS/polyamide‐6 blends

AbstractIn this study, commercially available epoxidized and maleated olefinic copolymers, EMA‐GMA (ethylene‐methyl acrylate‐glycidyl methacrylate) and EnBACO‐MAH (ethylene‐n butyl acrylate‐carbon monoxide‐maleic anhydride), were used at 0, 5, and 10% by weight to compatibilize the blend composed of ABS (acrylonitrile‐butadiene‐styrene) terpolymer and PA6 (polyamide 6). Compatibilizing performance of these two olefinic polymers was investigated from blend morphologies, thermal and mechanical properties as a function of blend composition, and compatibilizer loading level. Scanning electron microscopy (SEM) studies showed that incorporation of compatibilizer resulted in a fine morphology with reduced dispersed particle diameter at the presence of 5% compatibilizer. The crystallization behavior of PA6 phase in the blends was explored for selected blend compositions by differential scanning calorimetry (DSC). At high compatibilizer level a decrease in the degree of crystallization was observed. In 10% compatibilizer containing blends, formation of γ‐crystals was observed contrary to other compatibilizer compositions. The behavior of the compatibilized blend system in tensile testing showed the negative effect of using excess compatibilizer. Different trends in yield strengths and strain at break values were observed depending on compatibilizer type, loading level, and blend composition. With 5% EnBACO‐MAH, the blend toughness was observed to be the highest at room temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 926–935, 2007

Determination and comparison of the essentialwork of fracture (EWF) of two polyester blends

The fracture toughness of blends of polypropylene terephthalate (PPT) with polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) were investigated. Binary blends were prepared comprising 10:90, 30:70, 50:50, 70:30 and 90:10 mass/mass%. The fracture toughness was determined for each blend using the essential work of fracture (EWF) method and thin film double edge notched tension (DENT) specimens. The specific essential work of fracture, we, values obtained for blends of PET/PPT ranged from 27.33 to 37.38 kJ m–2 whilst PBT/PPT blends yielded values ranging from 41.78 to 64.23 kJ m–2. Differential scanning calorimetry (DSC) was employed to assess whether or not crystallinity levels influence the mechanical properties evaluated. The fracture toughness of PPT deteriorated with PET incorporation. However, high we values exceeding that of pure PPT were obtained for PBT/PPT blends across the composition range studied.