Blend Composition Research Articles

Prototype Design for Grading Structures in Powder Bed Fusion Processes.

While targeted alignment in certain additive manufacturing (AM) methods such as material extrusion (MEX) and stereolithography (SLA) has been well documented in the research community, a method for targeted alignment of added fillers or fibrous materials in powder bed fusion (PBF) AM devices has yet to be successfully achieved. Similarly, incorporation of multimaterials does not work easily with any of the AM technologies. This study creates a prototype design that could be integrated into a PBF system to allow for multimaterial layer deposition and alignment of powders and powder blends. The rheological properties of polyamide powder and a range of polyamide composite blends (incorporating milled carbon fibre, graphite flakes, polytetrafluoroethylene, and glass microspheres) in different concentrations were studied, and together with the particle size distribution and particle morphology analysis were applied for the design of a prototype hopper for incorporation in the PBF system to create targeted multimaterial deposition. Different concept designs, multichambered and multi-hopper with hopper angles calculated specifically for the composite blend powders selected, were proposed. Initial deposition trials outside a PBF process were tested, and the deposited layers were measured.

Single-layer organic photovoltaics fabricated via solution-based electrical doping of ternary bulk heterojunction films

The commercial viability of organic photovoltaics (OPVs) can be improved by simplifying their device geometry and easing fabrication complexity. Here, we demonstrate that solution-based p-type electrical doping of ternary bulk heterojunction (BHJ) films, which comprise 2 donor polymers and 1 fullerene acceptor (2D:1A), enables the realization of efficient single-layer OPVs. Systematic and detailed investigations of the optoelectronic characteristics of films with varying donor ratios, and their photovoltaic performance, demonstrate p-type electrical doping via post-process immersion into a 12-molybdophosphoric acid hydrate (PMA) solution, resulting in a reduced trap density and charge recombination without significantly changing the BHJ morphology. Furthermore, PMA doping of films comprising optimized ternary blend compositions and polyethylenimine enables the demonstration of single-layer OPVs with economic top electrode metals and a high level of performance under outdoor and indoor illumination conditions. These PMA-doped 2D:1A BHJ films are an attractive platform to reduce the efficiency-cost gap and accelerate the commercialization of OPVs for emerging applications.

How can nonprofit boards innovate for growth? An integrative‐systematic review

AbstractDespite the nonprofit sector's significance in economic contribution, workforce, and social impact, it faces unique innovation hurdles and is not well positioned for sustainability, growth, and prosperity. However, with only a partial, disconnected view from the extant research, we do not understand the relationship between boards and nonprofit innovation for growth. To address this problem, we conducted a systematic literature review drawing on 27 studies published since 2000 to provide a first‐in‐field and comprehensive integration of disparate, mono‐factorial research. We conceptualize a new, multifactorial model that depicts a blend of board composition, relations and practice factors, and organizational and environmental characteristics that influence nonprofit innovation for growth.

Regulation of dewetting and morphology evolution in spin-coated PS/PMMA blend films via graphene-based Janus nanosheets

Spin-coated blend films with complex phase-separated morphology find broad applications while precise tailoring of the morphology is still challenging. In this study, graphene oxide (GO)-based Janus nanosheets were synthesized by interfacial polymerization in a GO nanosheet stabilized Pickering emulsion with polystyrene (PS) and poly(hydroxyethyl methacrylate) synchronously being grafted to the GO nanosheet from the oil and water sides. The Janus nanosheets make the morphology of spin-coated PS/poly(methyl methacrylate)(PMMA) blend films tunable over the full height of the film until the substrate as their preferential assembly at the PS/PMMA interface and attachment on the glass substrate drive the top PS phase to migrate towards the substrate and the bottom PMMA phase to dewet from the substrate towards the air. By varying blend composition and Janus nanosheet loading, morphologies are readily transformed from a PS network on top of PMMA to PS droplets in the PMMA matrix and from PS encapsulated by PMMA to PMMA cavities in the PS network, etc.. This enables generating thin films with various morphologies ranging from a flat surface to cavity-network structures, droplet-matrix structures or bi-continuous structures, etc. at will. Moreover, the morphologies trapped by jammed nanosheets at the interface are super stable against further evolution upon annealing.

Decoupling the interplay of polymer properties and particle size in stability of co-continuous blend composites

Interfacially localizing particles in co-continuous polymer blends requires a complex interplay between the properties of polymers, such as interfacial tension between them, Γ, viscosity, η, viscosity ratio between them, and particle properties, such as particle size and particle surface chemistry. Here, we investigate the formation and coarsening dynamics of four co-continuous blend composites based on polypropylene, PP (or linear low-density polyethylene), and poly(ethylene-co-vinyl acetate), EVA filled with pristine silica of two sizes (140 and 250 nm). By choosing polymer blend components with different viscosities and interfacial tensions and particles with varying size and size distributions, we were able to elucidate their relative contributions in the stabilization of co-continuous polymer microstructures. By utilizing confocal rheology, we show that the evolution of storage modulus during coarsening of polymer blend composites is primarily dependent on the strength of the initial interfacial particle network. Our findings indicate that the initial domain size and kinetic control of interfacial particle localization in co-continuous polymer blends are determined by the Γ/η ratio of the neat blend. However, this relationship does not hold in low viscosity systems. When polymer blend viscosity is lower, it reduces the kinetic barrier at the interface, leading to a higher proportion of particles localizing in the favorable EVA phase. We also find that the smaller particles have a higher propensity for interfacial localization. These findings provide insight into the success of kinetic particle trapping at the interface of co-continuous blends and the resulting composite properties based on the choice of component properties.

Optimisation of extrusion process parameters to make ABS-PC filament for 3D printing using Taguchi-GRA technique

ABSTRACT This paper attempts to optimise the single screw extrusion (SSE) process parameters for extruding Acrylonitrile-butadiene-styrene (ABS) and Polycarbonate (PC) blend filament, having improved tensile strength and melt flow rate. The melt flow and mechanical properties of ABS-PC blend filament are highly reliant on the SSE process parameters. Thus, optimising the process parameters to fabricate the blend filaments with high performance has become essential. Grey relational analysis has been integrated with the Taguchi method to optimise the SSE process parameters by evaluating the grey relational grades in terms of the performance index. Experimentation has been carried out according to Taguchi’s L9 orthogonal array (OA), which has been designed considering three SSE process parameters, i.e. screw rotation, blend composition and chamber temperature. The co-continuous structure and compatibility between the phases of the blend obtained at ABS:PC 50:50 by wt%. Micrographs and thermographs support the results. The tensile strength of the 3D printed ABS:PC 50:50 by wt.% composite specimen has improved by 38.02% as compared to virgin ABS.

Physicochemical and sensory properties of cookies produced from malted sorghum and cassava grate composite flour blends

Physicochemical and sensory properties of cookies produced from malted sorghum and cassava grate composite flour blends

Physicochemical and sensory properties of cookies produced from malted sorghum and cassava grate composite flour blends

Malted sorghum - cassava flour was formulated into blends to produce cookies. Sorghum grains were sorted, washed, steeped (12 hours), malted (48 hours) and oven dried. Freshly harvested cassava roots were manually peeled, washed, grated and dried (using hybrid solar dryer at 50 oC). The dried malted sorghum grains and cassava were processed into flour and sieved. The blends were prepared by homogenously mixing malted sorghum flour and high quality cassava grate flour in varied proportion labelled as sample A (100 % Malted Sorghum Flour) Sample B (60 % Malted Sorghum Flour and 30 % Cassava Flour), sample C (70 % Malted Sorghum Flour and 30 % Cassava Flour) and Sample D (80 % Malted Sorghum Flour and 20 % Cassava Flour) separately prepared into cookies and subjected to proximate, mineral, anti-nutrients, physical and sensory analysis using standard analytical methods with chemicals of analytical grade. The result for moisture, Ash, Fat, Fibre, Protein, Carbohydrate and energy content for samples A, B, C and D respectively ranged from 3.11 % - 6.81 %; 1.41 % - 1.52 %; 21.66 % - 23.41 %; 2.20 % - 2.67 %; 4.41 % - 7.26 %; 60.86 % - 63.85 % 473.09 Kcal - 478.82 Kcal. The mineral result for sodium, potassium and calcium 15.06 mg/100 g, 12.70 mg/100 g, 14.40 mg/100 g and 17.00 mg/100 g; 24.70 mg/100 g, 28.17 mg/100 g, 21.60 mg/100 g and 25.17 mg/100 g; 11.30 mg/100 g, 13.10 mg/100 g, 10.09 mg/100 g and 10.09 mg/100 g respectively. The result recorded for colour ranged from 6.20 - 7.40; aroma was 6.30 - 7.30; taste ranged from 6.10 - 7.20; texture ranged from 5.60 - 5.90 and overall acceptability ranged from 5.70 - 6.50. It can be concluded that combination of Malted Sorghum and Cassava Flour in cookies production will help to enhance the utilization of both crops, nutritional intake, increase variety and reduce wheat importation.

Injectable Hydrogel Guides Neurons Growth with Specific Directionality.

Visual disabilities affect more than 250 million people, with 43 million suffering from irreversible blindness. The eyes are an extension of the central nervous system which cannot regenerate. Neural tissue engineering is a potential method to cure the disease. Injectability is a desirable property for tissue engineering scaffolds which can eliminate some surgical procedures and reduce possible complications and health risks. We report the development of the anisotropic structured hydrogel scaffold created by a co-injection of cellulose nanofiber (CNF) solution and co-polypeptide solution. The positively charged poly (L-lysine)-r-poly(L-glutamic acid) with 20 mol% of glutamic acid (PLLGA) is crosslinked with negatively charged CNF while promoting cellular activity from the acid nerve stimulate. We found that CNF easily aligns under shear forces from injection and is able to form hydrogel with an ordered structure. Hydrogel is mechanically strong and able to support, guide, and stimulate neurite growth. The anisotropy of our hydrogel was quantitatively determined in situ by 2D optical microscopy and 3D X-ray tomography. The effects of PLLGA:CNF blend ratios on cell viability, neurite growth, and neuronal signaling are systematically investigated in this study. We determined the optimal blend composition for stimulating directional neurite growth yielded a 16% increase in length compared with control, reaching anisotropy of 30.30% at 10°/57.58% at 30°. Using measurements of calcium signaling in vitro, we found a 2.45-fold increase vs. control. Based on our results, we conclude this novel material and unique injection method has a high potential for application in neural tissue engineering.

Blend composition effect on the diameter of electrospun chitosan (CHT)/poly(ethylene oxide) (PEO) nanofibers

This work reports how the different ratios of chitosan (CHT) and (PEO), the needle-to-collector distance, and the voltage of the applied potential affected the diameter of the fibers. The results suggested that the experimental conditions fell within an instability region, not following theoretical behaviors. However, the statistical analysis provided information regarding which conditions were statistically equal and which ones were different at 95%. The best condition was a CHT/PEO ratio of 80/20, a distance of 20 cm, and a voltage of 20 kV. These electrospun nanofibers had a smooth and homogeneous surface and a diameter of (320 ± 8) nm. The incorporation of neomycin sulfate (NS) led to rough and clustered fibers due to the formation of hydrogen bonds between the drug and the polymers. The crystallinity decreased from 0.82 (CHT/PEO 80/20) to 0.13 (CHT/PEO 80/20-NS) confirming the absorption of the drug. The CHT/PEO 80/20-NS displayed improved antimicrobial activity, and the controlled release assay indicated a two-stage release profile attractive for the treatment of skin wounds, releasing higher amounts at first, and sustaining the release for 4 h. These nanofibrous mats would be potentially suitable for wound dressing purposes.

Rheological Characteristics of Starch-Based Biodegradable Blends.

Thermoplastic starch was blended with commercially available biodegradable polyesters of poly(butylene adipate-co-terephthalate) (PBAT) and poly(lactic acid) (PLA) for its improved performance and processability. The morphology and elemental composition of these biodegradable polymer blends were observed by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively, while their thermal properties were analyzed using thermogravimetric analysis and differential thermal calorimetry. For rheological analysis, the steady shear and dynamic oscillation tests of three samples at various temperatures were investigated using a rotational rheometer. All three samples exhibited significant shear thinning at all measured temperatures, and their shear viscosity behavior was plotted using the Carreau model. The frequency sweep tests showed that the thermoplastic starch sample exhibited a solid state at all temperatures tested, whereas both starch/PBAT and starch/PBAT/PLA blend samples exhibited viscoelastic liquid behavior after the melting temperature such that their loss modulus at low frequencies was greater than the storage modulus, and inversion occurred at high frequencies (storage modulus > loss modulus).

Additive Manufacturing of Carbon Fiber Reinforced Epoxy Thermoset with Improved Thermomechanical Properties

Laser Powder Bed Fusion (LPBF) is a widely used additive manufacturing technique for powder-based polymers and metallic materials. Thermoplastics like Polyamide 12 and Polyamide 6 are commonly used in LPBF; thermosetting polymers are gaining attention due to their superior stability. Epoxies are a popular thermoset, but some exhibit low physical properties and brittleness, leading to reduced toughness. The work presented in this paper explores the effect of using short carbon fibers (CF) as additives to epoxy-based thermosetting material on physical and thermomechanical properties. A total of six epoxy thermoset/CF composite powder blends were prepared by varying reinforcing materials weight percentages (0 wt%, 0.3 wt%, 0.6 wt%, 1 wt%, 5 wt%, and 10 wt%). Tensile, four-point bending, and dynamic mechanical analysis (DMA) test samples were printed using the LPBF technique. Significant improvements in the physical and thermomechanical properties were obtained in the thermoset composites with 5 wt% of CF due to good adhesion between reinforcing materials and the matrix and a low level of porosity. Fracture surface analysis was performed via scanning electron microscopy (SEM), which provided insight into the influence of CF on the properties of thermosetting composites. The findings of this research demonstrate the feasibility of improving the inferior physical and thermomechanical properties of 3D-printed CF-reinforced epoxy. With a certain amount of CF reinforcement, Young’s modulus and fracture modulus can be increased by around 52% and 259%, respectively.

Compatibilized bio-based polybutylene-succinate blended composites filled with surface modified Si3N4 for improved rigidity and thermal performance

In this study, polybutylene succinate was melt blended with polypropylene (PP) to fabricate partially bio-based and miscible composites filled with various loading silicon nitride (Si3N4) particles. Oleic acid and PP-grafted maleic anhydride were used as a functionalizing agent for Si3N4 and as a compatibilizer for polymer blends, respectively. The surface functionalization of the Si3N4 particles enhanced the interfacial adhesion between the filler and the blended polymers, affecting the thermal and mechanical properties of the composites. The thermal conductivity of the composite filled with only 18.6 vol% surface-treated Si3N4 increased by 342% compared to that of the blended polymer. In addition, the surface treatment of Si3N4 significantly improved the Young’s modulus, tensile strength, and thermal stability of the corresponding composites. However, the temperature-dependent storage modulus was unaffected by the surface treatment of Si3N4 and increased as the loading content of the Si3N4 particles increased.

Design of super-toughened, heat-resistant and antistatic polyethylene terephthalate-based blend composites by constructing a tenacious interface

It's a great challenge to achieve the synchronous enhancement of the fracture toughness and strength via designing the microstructures of blend composites. Herein, multi-walled carbon nanotubes (MWCNTs) were incorporated into polyethylene terephthalate/ethylene butyl acrylate-glycidyl methacrylate terpolymer (PET/PTW) blend. Effects of MWCNTs on the mechanical properties, phase morphology, crystallization behaviors, heat resistance and antistatic property of the blend were investigated. It is found that MWCNTs are selectively located at the two-phase interface of the blend and induce epitaxial crystallization of PET matrix, which better strengthens the interfacial adhesion of blend composites. Tenacious interface endows blend composites with superior fracture toughness and strength. The impact strength and tensile strength of the blend composite only containing 0.5 wt% MWCNTs are as high as 72.3 kJ/m2 (without fracture) and 38.9 MPa, respectively. The toughening mechanisms are attributed to the role of MWCNTs in compatibilizing, stress transferring and hindering the rapid propagation of cracks at the interface of the blend. Moreover, MWCNTs endow the blend composites with outstanding heat resistance and antistatic property, which enlarges the application fields of PET. This work offers a dexterous and effective blueprint for manufacturing of high mechanical performances PET-based blend composites.

Miscibility of nitrated poly(phenylene oxide) and styrene–acrylonitrile copolymer blends

AbstractPoly(2,6‐dimethyl‐1, 4‐phenylene oxide) (PPO) is a well‐known high heat‐resistant polymer and miscible with polystyrene. However, it is not miscible with many polymers containing polar groups. In the present study, PPO was nitrated to prepare a nitrated PPO (NPPO) containing polar nitro groups and blended with a copolymer of styrene/acrylonitrile (SAN). Dynamic mechanical analysis (DMA) data showed that NPPO in SAN‐rich phase was miscible with SAN, while NPPO in NPPO‐rich phase was partially phase‐separated from SAN, both over the entire blend composition range from NPPO wt. fractions of 0.1–0.5 investigated for this work. Analyses of Fourier‐transform infrared (FTIR) and ultra‐violet (UV–VIS) spectra indicated that the miscibility of NPPO with SAN was caused by intermolecular hydrogen bonding of CN group of SAN with OH end‐group of NPPO in the NPPO/SAN blends. NPPO's OH end‐group, meta‐nitro 2,6‐dimethyl phenol, was produced during nitration of PPO due to chain scission of aryl ether bond. Besides the intermolecular hydrogen bonding, dipole‐diplo interaction of the CN and nitro groups resulted in dissociation of the CN dimers and trimers to the CN monomers in the NPPO/SAN blends.

Employing impedance spectroscopy to investigate electrical conduction mechanism in polymer composite blends containing conductive masterbatch: PP/EVA/ (PP-g-MA/MWCNTS)

Impedance spectroscopy analysis has been employed to investigate the effect of melt mixing time on electrical conduction mechanism, direct contact or electron tunneling, of a polymer blend using a conductive masterbatch. A novel approach is proposed to correlate the dispersion/distribution states of conductive nanoparticles within the phases, achieved through kinetic control of the conductive masterbatch, and their impedance properties. A blend of polypropylene and ethylene-vinyl acetate copolymer (PP/EVA) was considered as a case study for the matrix. An electrically conductive masterbatch of multiwalled carbon nanotubes (MWCNTs) in polypropylene-grafted-maleic anhydride (PP-g-MA) was added to the blend. The masterbatch in varying amounts was mixed with PP/EVA in a range of 1 min–4.5 min. The co-continuous morphology of the ternary polymer blend was validated via scanning electron microscopy micrographs. The atomic force microscopy (AFM) results showed that as the mixing time of the masterbatch increases the interconnected structures within the conductive interphase decrease. Impedance spectroscopy using alternating current was employed to probe the conduction mechanism in the composite blends. The impedance spectroscopy results revealed that for samples with low mixing time, a dielectric relaxation peak occurs at high frequencies due to the existence of more conductive pathways as a consequence of the interconnected structures of the masterbatch phase. Also, the major contribution of conductance was direct contact in the samples with low mixing times while electron tunneling mechanism was considerable for the samples with high mixing times. Dielectric constant was increased as a result of interfacial polarization boosting with mixing time. The percolation threshold was considerably decreased from 0.95 v% for simultaneous direct mixing method to 0.16 v% for the masterbatch method.

β-CaSiO3 and colloidal n-SiO2 based blended cement composites- their properties, regression analysis and micro-characterization studies

This paper examines the effect on mechanical properties such as compressive strength, flexural strength, and dynamic modulus of elasticity (DYE) of different proportions of wollastonite (β-CaSiO3) and colloidal nano-silica (n-SiO2) partially replacing cement. Durability indicators (water absorption, sorptivity and sulphate treatment test) were also examined to ascertain the quality of hardened paste mixes with respect to the control mix. The regression models were found for mechanical properties using different parameters from the results obtained, and statistical relations were established and validated. Regression analysis shows the significance of every parameter considered and model for the prediction of mechanical strengths. Finally, the results were substantiated by the microstructural characterization by FESEM. β-CaSiO3 and colloidal n-SiO2 replaced cement by 15%, and 1.5%-6% with an offset of 1.5%, respectively at low (0.25), medium (0.40) and high (0.55) water/binder (w/b) ratio. FESEM micrographs showed dense Calcium-silicate-hydrate (CSH) gel and stratlingite (CASH) was formed by blended cement paste mixes containing β-CaSiO3 and n-SiO2. n-SiO2 at 3% and CaSiO3 at 15% replacements of cement (NS3 mix) was the optimum replacement level for the cement paste mix. Analysed regression model suggests that the models and parameters were found significant and can also be used for prediction (based on R2 values and p-value).

Enhancement of the Mechanical and Thermal Properties of Polypropylene and Nylon 6.6 Composite Blends

The mechanical and thermal properties of nylon 6.6 on polypropylene (PP) blends were investigated. Five weight percentages of nylon 6.6, 1 wt%—5 wt%, were blended with PP by an injection molding process to produce PP/nylon 6.6 blends. The impact of the mixture on the mechanical properties was investigated by performing a three-point bend test to determine the flexural strength and hardness test using nanoindentation. Both differential scanning calorimetry and thermogravimetric analysis were used to study the thermal properties of the mixture. Chemical and morphological testing was performed by Fourier-transform infrared spectroscopy and scanning electron microscope tests. Mechanical testing revealed improved strength, modulus, and hardness of the PP/nylon 6.6 blends. The 2 wt% blend showed elastic modulus, tensile, and yield stress enhancement. TGA showed variable results with improved thermal resistance for the 3 wt% and 4 wt% blends, whereas there was no effect for the 2 wt% blend and reduced thermal resistance for the 1 wt% and 5 wt% blends. DSC analysis revealed no influence on the melting temperature of the blends. SEM images showed a homogeneous mixture between PP and nylon 6.6, which substantiated the interfacial adhesion between PP and nylon 6.6 and was verified by FTIR.

The effect of epoxy vitrimer on the structure and properties of thermoplastic polyurethane/polycaprolactone polymer composites

AbstractA vitrimer (ESO‐S) was prepared by direct curing of epoxy soybean oil (ESO). A series of polymer/ESO‐S blend composites were prepared by adding different content of ESO‐S, and the corresponding characteristics change of thermoplastic polymer composites was explored. Fourier transform infrared spectroscopy (FTIR) test demonstrated that ESO‐S can achieve covalent bonding and intermolecular hydrogen bonding between ESO‐S and polymer matrix, thus the interfacial compatibility between composite components was improved. The tensile strength of composites was increased by adding the ESO‐S of suitable content. The tensile strength reached the maximum value (38.15 MPa) when the ESO‐S content was 0.8 wt%. In addition, the thermal stability and melting temperature of the composites were also improved.

Rheological behaviour of different composite materials for additive manufacturing of 3D bone scaffolds

The production of scaffolds for bone tissue applications is requiring a combination of physical and biological properties, which are depending on the materials morphology and pro-cessing conditions during the production process. The aim of the paper is the investigation of rheological behaviour of polymer and composite blends regularly used for the production of scaffolds for bone tissue applications with the use of additive manufacturing. Poly-ε-caprolactone (PCL), hydroxyapatite (HA), β-tri-calcium phosphate (TCP) and Bioglass 45S5 blends containing different ceramic concentrations (10 wt%, 15 wt% and 20 wt%) were prepared with the use of melt blending procedure and investigated with the use of oscillation and rotational rheology tests. Results are showing that all blends are presenting viscoelastic behaviour with higher viscous modulus, compared with elastic modulus for low frequencies, with this difference reducing while the frequency is increasing. All blends are presenting shear-thinning behaviour suitable for use with additive manufacturing methods. Viscous and elastic modulus are increasing by adding ceramic particles. Results are presenting that PCL/HA blends of the same material concentration are presenting higher elastic modulus properties compared with the other blends, while PCL/Bioglass blends are presenting lower loss factor, lower relaxation time and lower shear viscosity making them easier to handle during the printing procedure.