Effect Of Blend Composition Research Articles

Effect of Blend Composition on Scratch Behavior of Polystyrene/Poly(2,6‐dimethyl‐1,4‐phenyleneoxide) Blends

AbstractThe relationship between the scratch behavior and molecular aggregation states of polystyrene (PS), poly(2,6‐dimethyl‐1,4‐phenyleneoxide) (PPO), and their blends, is investigated based on differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), polarized optical microscopy (POM), and indentation and scratch tests. DSC reveals that all the PS/PPO blends show the single glass transition temperature (Tg) and the Tg monotonically increase and Tg breadth exhibits a maximum, with an increase in PPO content. Furthermore, density and intermolecular chain distance obtained by WAXD exhibits maximum and minimum values at near 50 wt% of PPO, respectively. It is evident that densification occurs by blending PS and PPO. The scratch coefficient of friction (SCOF) value of PS is the largest and PS exhibits a fish‐scale pattern after scratch testing, while the SCOF value of PPO is much smaller than PS and PPO exhibits smooth groove formation. The PS50/PPO50 and PS20/PPO80 blends exhibit superior scratch and indentation resistance than PS and PPO. Damage morphology observation by POM and indentation tests reveals that molecular orientation is more restricted, and resistance against indentation increases for blends. This is due mainly to densification of the blend system.

Structure–property relationship and controlled drug release from multiphasic electrospun carvacrol-embedded polylactic acid/polyethylene glycol and polylactic acid/polyethylene oxide nanofiber mats

Electrospinning technologies gained considerable interest over the last decade. In this study, it is proposed a systematic study of polylactic acid/polyethylene glycol (PLA/PEG) and polylactic acid/polyethylene oxide (PLA/PEO) electrospun blends at different concentrations. The effect of blend composition and PEG molecular weight on the morphological and mechanical properties of the mats was evaluated. Furthermore, the kinetic release of carvacrol as model drug in phosphate buffer saline at 37℃ was studied and the data were then fitted using an exponential model. The scanning electron microscopy revealed that the morphology of the mats was strongly dependent on the relative ratio PLA:PEG, PLA:PEO and in the presence of carvacrol. Furthermore, the mechanical properties of the mats as well as their carvacrol release rate were successfully tuned by changing the relative ratio of the blend components.

Structure-property relationships of microporous membranes produced by biaxial orientation of compatibilized PP/Nylon 6 blends

Microporous membranes were produced from biaxial orientation of polymer blends comprising polypropylene (PP), polyamide 6 (Nylon 6), and polypropylene grafted maleic anhydride (PPgMA). During biaxial orientation, the continuous PP domains cavitated while the dispersed Nylon 6 domains remained rigid and spherical. The effect of blend composition on cavitation was analyzed and a ternary diagram generated to identify the composition range for through-pore formation. The effects of draw ratio and initial film thickness on membrane properties were also studied. The membranes were found to have adjustable porosity up to 62% with nanoscale size pores. The filtration performance was evaluated on such membranes with varied thickness. The membranes showed very high filtration efficiency on separating 50 nm Latex microbeads from water suspensions.

Studies on Thermal Behaviour of Cotton and Eri/Cotton Blended Fabrics Using Response Surface Methodology

Eri silk fibre, the lone domesticated non-mulberry variety of silk is reported to possess excellent thermal insulation property and the fabrics made of eri silk yarn is popularly used as warmth giving apparels by the people of north-eastern states of India in particular. On the other side, cotton fibre which is comparatively cheaper than eri silk has wide application in making apparel fabrics. This paper deals with the manufacturing of plain woven fabrics made of eri/cotton blended yarn as weft over cotton warp yarn and to conduct an in-depth study on the effect of blend composition and yarn parameters like count (Ne) and amount of twist on its thermal behaviour. The Box and Behnken model of Design of Experiment for three variables and three levels, a popular statistical tool, has been used to study the influence of chosen factors. The fitted regression equation has been found to be linear in nature confirming the presence of independent effect of yarn fineness, twist and eri content in the blended yarn over thermal insulation value of the fabric with strong degree of association. The effects of yarn count, twist and proportion of eri in blends have been well explained using response surface methodology.

Core-Shell Fibers Electrospun from Phase-Separated Blend Solutions: Fiber Formation Mechanism and Unique Energy Dissipation for Synergistic Fiber Toughness.

Through single-tube electrospinning, the biodegradable core-shell fibers of poly(3-hydroxybutyrate) (PHB) and poly(d,l-lactic acid) (PDLLA) were obtained from blend solutions with different compositions at a total polymer concentration of 7 wt %. Regardless whether PHB is the major or minor component (PHB/PDLLA = 90/10, 75/25, 50/50, and 25/75 wt. ratio), these phase-separated solutions all yielded core-shell fibers with PHB as core and PDLLA as shell. A new scenario of core-shell fiber formation was proposed on the basis of the relative magnitude of the intrinsic relaxation rate of fluids and external extension rate during electrospinning. The effects of blend compositions on the morphologies of the Taylor cone, whipping jet, and as-spun fibers were investigated. The diameters of core-shell fibers can be tailored by simply varying the PHB/PDLLA ratios. Two scaling laws describing the apparent viscosity (ηo) dependence of the outer fiber diameter (dfo) and core fiber diameter (dfc) were derived. That is, dfo ∼ ηo0.38 and dfc ∼ ηo0.86. The microstructures of the as-spun fibers were determined by differential scanning calorimetry, Fourier transform infrared spectroscopy, and synchrotron wide-angle and small-angle X-ray scatterings. Results showed that the PDLLA component was in the amorphous state, and the crystallizability of PHB component remained unchanged, except the amorphous 10/90 fibers electrospun from a miscible solution state. The synergistic mechanical properties of the core-shell fibers were obtained, along with the ductile PDLLA shell enclosing the brittle PHB core. The enhanced toughness was attributed to the fragmentation of the brittle PHB core and necking fracture of the ductile PDLLA shell, which served as an effective route for energy dissipation. Compared with the neat PHB fiber, the 90/10 and 75/25 core-shell fibers possessed larger elastic moduli, which was attributed to the high PHB crystal orientation in their core sections despite the reduced PHB crystallinity. By contrast, the crystal c-axis of PHB in the 25/75 core-shell fibers was preferentially perpendicular to the fiber axis, suggesting the significant stretching of developing PHB crystals during electrospinning.

Effect of Blend Composition on Bulk Heterojunction Organic Solar Cells: A Review

Significant research and development in the field of organic photovoltaics (OPVs) has been undertaken in recent years. Impressive results relating to both device performance and fabrication techniques suggest it will be a promising renewable energy technology for future low‐cost electricity generation. The necessity of the heterojunction in OPV cells, due to the large exciton binding energy, places constraints on the design of the photoactive layer. The blend composition, meaning the concentration of the donor and acceptor material in the film, is crucial in determining many aspects of the bulk heterojunction (BHJ) active layer film. In this article, the influence of the blend composition on the film morphology and device performance is reviewed. The mechanisms determining this relationship is explored for three different active layer designs, binary polymer: fullerene blends, ternary blends, and organic–inorganic blend films. Finally, the perovskite solar cell is discussed, with an emphasis on the different perovskite ion compositions which have thus far been explored.

Blend Hydrogel Microspheres of Carboxymethyl Chitosan and Gelatin for the Controlled Release of 5-Fluorouracil.

Carboxymethyl chitosan (CMCS) was synthesized and blended with gelatin (GE) to prepare hydrogel microspheres by w/o emulsion cross-linking in the presence of glutaraldehyde (GA), which acted as a cross-linker. 5-Fluorouracil (5-FU) was encapsulated to investigate its controlled release (CR) characteristics in acidic (pH 1.2) and alkaline (pH 7.4) buffer media. The microspheres which formed were spherical in nature, with smooth surfaces, as judged by the scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) confirmed the carboxymethylation of CS and the chemical stability of 5-FU in the formulations. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) confirmed the physical state and molecular level dispersion of 5-FU. Equilibrium swelling of microspheres was performed in water, in order to understand the water uptake properties. The in vitro release of 5-FU was extended up to 12 h in pH 7.4 phosphate buffer, revealing an encapsulation efficiency of 72%. The effects of blend composition, the extent of cross-linking, and initial drug loading on the in vitro release properties, were investigated. When analyzed through empirical equations, the release data suggested a non-Fickian transport mechanism.

Demixing by a Nematic Mean Field: Coarse-Grained Simulations of Liquid Crystalline Polymers.

Liquid crystalline polymers exhibit a particular richness of behaviors that stems from their rigidity and their macromolecular nature. On the one hand, the orientational interaction between liquid-crystalline motifs promotes their alignment, thereby leading to the emergence of nematic phases. On the other hand, the large number of configurations associated with polymer chains favors formation of isotropic phases, with chain stiffness becoming the factor that tips the balance. In this work, a soft coarse-grained model is introduced to explore the interplay of chain stiffness, molecular weight and orientational coupling, and their role on the isotropic-nematic transition in homopolymer melts. We also study the structure of polymer mixtures composed of stiff and flexible polymeric molecules. We consider the effects of blend composition, persistence length, molecular weight and orientational coupling strength on the melt structure at the nano- and mesoscopic levels. Conditions are found where the systems separate into two phases, one isotropic and the other nematic. We confirm the existence of non-equilibrium states that exhibit sought-after percolating nematic domains, which are of interest for applications in organic photovoltaic and electronic devices.

Fabrication and properties of poly(tetrafluoroethylene) nanofibres via sea-island spinning

Polytetrafluoroethylene (PTFE) has some unique properties such as high hydrophobicity and high resistance to elevated temperatures, chemicals and solvents which make it of interest for fibres and textiles. However, PTFE normally decomposes before melting, meaning that it cannot be readily melt-spun into fibres. In addition, PTFE is insoluble in all common organic solvents, prohibiting its use in common solution spinning methods such as dry, wet or electrospinning. Here we aim to develop an easy and environmentally friendly alternative for the production of PTFE nanofibres, using a modified island-in-the-sea solution spinning process. For this, first a dispersion of a PTFE homopolymer, PVA and water are compounded to create a blend of PTFE particles in a PVA solution. After the solid-state drawing of this blend and removal of the PVA, we are able to collect PTFE nanofibres with finest diameters of around 50 nm and lengths up to 15 μm. The effects of blend composition, morphology and drawing on PTFE fibre formation and properties are studied and discussed.

Hydrophilicity and antifouling property of membrane materials from cellulose acetate/polyethersulfone in DMAc

In this study, cellulose acetate (CA) was blended with polyethersulfone (PES) to endow the ultrafiltration membrane with the improved hydrophilicity and antifouling property by using N,N-dimethylacetamide (DMAc) as the solvent. The effects of blend composition and evaporation time on the mechanical strength and pure water flux were investigated. It was found that the optimal composition of the casting solution was: 18wt% (PES), 4wt% (Polyvinylpyrrolidone K30), 3wt% (CA) and 20s (Evaporation time). The characteristics of CA-PES blend membranes were investigated through the methods of contact angle goniometer, antifouling property, compatibility, thermo gravimetric analysis and SEM. The results showed that the hydrophilicity and antifouling property of CA-PES ultrafiltration membranes were enhanced in comparison with the pure PES membranes. The CA-PES membranes exhibited semi-compatibility and good thermal stability below 270°C. This study provided a potential industrial application prospect of CA-PES membranes prepared in DMAc.

Thermal degradation and crystallization characteristics of multiphase polymer systems with and without compatibilizer

Effects of blend composition and compatibilizer concentration on the thermal degradation and crystallization characteristics of polyolefin blends are reported. Phase morphology and therefore, blend composition played a crucial role in the thermal degradation behaviour of the blends. Although compatibilization significantly improved the thermal stability of the blends, melting and crystallization parameters of the polymers were only marginally affected. Compatibilized blends with co-continuous morphology exhibited a type of “co-degradation” and “co-crystallization”.

Effect of blend composition on ternary blend organic solar cells using a low band gap polymer

This work investigates the influence of blend composition in ternary blend bulk heterojunction organic solar cells composed of poly(3-hexylthiophene-2,5-diyl) (P3HT), poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta [2,1-b:3,4-b′]dithiophene-siloe 2,6-diyl]] (Si-PCPDTBT) and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM). The use of the low band gap Si-PCPDTBT vastly improves the spectral response, when compared to a P3HT:PC71BM binary system. The optimum blend composition occurred at a total polymer concentration of 50wt%. At low polymer concentrations, the P3HT phase was amorphous in nature. Increasing the polymer content led to the formation of crystalline polymer domains, as evidenced by XRD measurements. This significantly enhanced the charge carrier transport throughout the active layer. XPS depth profiles indicated that variations in the polymer content also influenced the mixing between the Si-PCPDTBT and the P3HT host matrix. This analysis showed that the 50wt% was conducive to a larger interaction between the two polymers. A comprehensive analysis of the relative contributions of each molecule to the photoluminescence suggested that the polymer concentration not only affects the film microstructure, it also influences the photoluminescence quantum yield of the blend. This is caused by alterations to the recombination mechanisms occurring in the constituent materials, which, in turn, influences photocurrent generation. This result shows that the overall polymer content must be chosen carefully to strike a delicate balance between improved absorption and effective charge generation and collection.

Dynamic mechanical, mechanical and thermal analysis of CPI/NBR blends: effect of blend composition and crosslink density

Blends of cis-polyisoprene (CPI) and nitrile butadiene rubber (NBR) in different volume ratio were prepared to see the effect of composition on different properties. Structure characterization has been done through X-ray diffraction and scanning electron microscope. Scanning electron micrographs confirm homogeneous nature of all the blends. The dynamic mechanical analyzer was used to measure damping, storage modulus, glass transition temperature and mechanical properties (Young’s modulus and tensile strength) of these blends. Activation energy and fragility were determined for the non-Arrhenius (fragile) behavior of viscosity using Vogel–Fulchuer–Tammann (VFT) equation. Thermal conductivity has been analyzed through thermal constant analyzer. Results indicate that all the measured properties are dependent on blend composition and crosslink density.

Morphological evolution during thermal and strain induced crystallization in poly(ethylene terephthalate)/poly(ether imide) blend films

The effect of blend composition and deformation history on the development of structural hierarchy in crystallizable PET rich blends of PET/PEI from amorphous precursors was investigated. PET/PEI films are melt miscible consequently the addition of PEI to PET increases the glass transition temperature while slightly broadening it as a result of partial micro phase separation. The crystallization in these films were found to be affected by two main factors: I) blend composition ii) the extent of deformation imposed on the films leading to preferential orientation. In the absence of orientation, the increase of PEI fraction leads to decrease of crystallizability as expected from the dilution effect that spatially prevents the crystallizable polymer chains from coming together. Stretching process and resulting stress levels and crystallinity depend on the blend concentration. The increase of PEI at a given temperature increase the stress levels during stretching due to both the increase of Tg and its breadth. The increase PEI concentration lead to increase in highly defective crystallites due to intrusion of bulky PEI chains into the PET crystalline regions. Above 30% PEI, the blend crystallizability disappears.

Effect of Blend Composition and Additives on the Morphology of PCPDTBT:PC71BM Thin Films for Organic Photovoltaics.

The use of solvent additives in the fabrication of bulk heterojunction polymer:fullerene solar cells allows to boost efficiencies in several low bandgap polymeric systems. It is known that solvent additives tune the nanometer scale morphology of the bulk heterojunction. The full mechanism of efficiency improvement is, however, not completely understood. In this work, we investigate the influences of blend composition and the addition of 3 vol % 1,8-octanedithiol (ODT) as solvent additive on polymer crystallization and both, vertical and lateral morphologies of poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] and [6,6]-phenyl C71-butyric acid methyl ester (PCPDTBT:PC71BM) blend thin films processed from chlorobenzene-based solutions. The nanoscale morphology is probed with grazing incidence small- and wide-angle X-ray scattering as well as X-ray reflectivity and complemented with UV/vis spectroscopy. In PCPDTBT:PC71BM films the use of ODT is found to lower the solubility of fullerene in the polymer matrix and to promote polymer crystallization, both vertical and lateral microphase separation with morphological coarsening, and formation of a fullerene-rich topping layer. The enhanced photovoltaic performance is explained by these findings.

Effect of Blend Compositions on Mechanical Properties of Irradiated Titanium Dioxide (TiO<sub>2</sub>)/Polyvinyl Chloride (PVC)/Epoxidized Natural Rubber (ENR) Nanocomposites

In this study, effect of blend compositions of irradiated polyvinyl chloride (PVC)/epoxidized natural rubber (ENR) blends was carried out. In previous work, it was reported that the mechanical properties of 50/50 composition irradiated blend had performed the highest strength with addition of 6 wt% of titanium dioxide (TiO2). However, the combination of PVC/ENR in a certain ratio might results in optimal mechanical properties and other specific properties for the new blends formed. Thus, addition of 6 wt% TiO2 and varies compositional range of PVC/ENR ranging from 30, 50 and 70 wt% were prepared by melt-blending technique and the effects on the mechanical properties were investigated. The blends were exposed to 0-150 kGy of electron beam irradiation before being characterized. With addition of 6 wt% TiO2, the characterization of mechanical properties including tensile strength, impact and hardness shows increment in values for all compositions. The increments of tensile strength were fall within 6-18% and as expected 70/30 PVC/ENR blends have shown the highest value. Based on the result, it revealed tensile and impact strengths achieved the optimum value at 100 kGy, while hardness increased as the radiation dose increased. From scanning microscope electron (SEM), micrographs have illustrated the blends with addition of 6 wt% TiO2 are smooth, continuous phase and less void appearance were seen. At higher dose rate, fracture paths were found to be continuous and penetrate deep into the material and this indicates that the failure is essentially brittle and it supports the above findings.

On O2 gas permeability of PP/PLA/clay nanocomposites: A molecular dynamic simulation approach

Polypropylene/poly(lactic acid) (PP/PLA) blends were prepared by reactive blending in a co-rotating twin-screw extruder. Effect of blend composition on oxygen permeability through compression molded films was investigated and correlated to the microstructure. Two blends, PP-rich (75/25) and PLA-rich (25/75), were selected in order to consider the effect of incorporation of clay and compatibilization on the permeability. The PP-rich blends had greater oxygen barrier properties compared to those of PLA-rich blends. Several proposed models of permeability for blends and nanocomposites were examined. These models failed to predict the permeability values, especially for PLA-rich blends. The failure was attributed to the immiscibility issue leading to appearance of microvoids at the interface. Molecular dynamics simulations were performed by employing the COMPASS force field to estimate the diffusivity of oxygen gas through pure components, PP-rich and PLA-rich systems. The simulated results were in good agreement with the available experimental data.

Influence of Blend Composition on Crystallization of Poly(L-Lactic Acid)/Poly (Ethylene Oxide) Crystalline/Crystalline Blends

The effect of blend composition on crystallization morphology and behavior of a crystalline/crystalline blend, poly(l-lactic acid) (PLLA)/poly(ethylene oxide) (PEO), during slow, non-isothermal crystallization was studied by polarized light microscopy (PLM) connected with a hot-stage and differential scanning calorimetry (DSC). The results showed that all of the PLLA/PEO blends produced spherulites which gradually became bigger and looser, as well as coarser, with the increment of the PEO content, indicating that the PEO crystals was resided in the interlamellar or interfibrillar (between clusters of commonly oriented lamellae) regions of the PLLA spherulites. In the (25/75) and (10/90) blends, the nucleation and growth processes of the PEO spherulites could be clearly observed in the pre-existing PLLA spherulites. The onset crystallization temperature and the melting point of one component decreased with increasing the content of the other one owing to the good miscibility of the two components in the non-crystalline state and the interaction between their macromolecules, indicating that the crystallization of each component was influenced by the other one.

INFLUENCE OF ELECTRON BEAM TREATMENT ON THE CRYSTALLIZATION AND THERMAL STABILITY OF LDPE/EPDM BLENDS

The effect of blend composition and Electron Beam (EB) irradiation on the crystallization and thermal behavior of Low Density Polyethylene (LDPE)/Ethylene-Propylene-Diene elastomer (EPDM) blends had been studied. Melting temperatures were found to remain unchanged upon variation of blend composition as well as irradiation dose. But the degree of crystallinity and Tc (crystallization temperature) were decreased with increase in EPDM content and EB dose. On the other hand, thermal stability (in terms of onset temperature and degradation temperature) and activation energy were increased with increase in EPDM content and irradiation dose. But the speed of degradation slowed down with increasing EPDM content and EB dose. Interestingly, once Trimethylolpropane Triacrylate (TMPTA) and Triallyl Cynuerate (TAC) were incorporated into the blends, the degrees of change of these properties were more in same direction upon irradiation. At higher irradiation dose properties were demoted due to chain scission.

Effect of prior photodegradation on the biodegradation of polypropylene/poly(3-hydroxybutyrate) blends

In this work, the effect of blend composition and previous photodegradation on the biodegradation of polypropylene/poly(3-hydroxybutyrate) (PP/PHB) blends was studied. The individual polymers and blends with or without the addition of poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) [P(E-MA-GMA)] as a compatibilizer (in the case of 80/20 blend) were exposed to UV light for 4 weeks and their biodegradation was evaluated. The biodegradation of PHB phase within the blends was hindered as PHB was the dispersed phase and PP fibrous particles were observed at the surface of the blend samples after biodegradation. Previous photodegradation lessened PHB biodegradation but enhanced the biodegradation of PP and the blends within the biodegradation time studied. Photodegradation resulted in cracks at the surface of PP and the blends, which probably facilitated the biotic reactions due to an easier access of the enzymes to deeper polymer layers. It also resulted in a decrease of molecular weight of PP phase and formation of carbonyl and hydroxyl groups which were consumed during biodegradation. Size exclusion chromatography analysis revealed that only the short chains of PP were consumed during biodegradation. POLYM. ENG. SCI., 53:2109–2122, 2013. © 2013 Society of Plastics Engineers