Polypropylene (PP)–Acacia mangiumcomposites: the effect of acetylation on mechanical and water absorption properties

Acacia mangiumwood flour (AMWF)–polypropylene (PP) composites were produced at different filler loading (20, 30, 40, and 50 w/w) and mesh no. (35, 60, 80, and 100 mesh). The AMWF–PP composites (using unmodified or modified wood flour) were compounded using a Haake Rheodrive 500 twin screw compounder. The mechanical and water absorption (WA) properties of modified (only at mesh no. 100) and unmodified AMWF–PP composites were investigated. Increase in the mesh number (35–100) of the unmodified AMWF showed increased flexural and impact properties. Flexural modulus exhibited higher properties as the filler loading increased (20–50). However, flexural and impact strength showed the opposite phenomenon. Water absorption and thickness swelling increased as the mesh number and filler loading increased. This has been attributed to the presence of hydrophilic hydroxyl groups of the filler. Modified AMWF–PP composites exhibited higher mechanical properties and good water resistance when compared to unmodified AMWF–PP composites at all values of filler loading. The evidence of the failure mechanism (from impact strength) of the filler–matrix interface was analyzed using scanning electron microscope.     

No more ‘core-shell’ in binderjetting of bioceramics: Novel solution and experimental validation in microstructure and mechanical properties

During binderjetting of bioceramics, many commercial 3D printers dispense binder in a default ‘core-shell’ manner. Using such a conventional approach, more binder is dispensed at the periphery (shell) and less binder at the ‘core’ of the structure. The inhomogeneous binding of the powder particles from the shell to the core significantly impacts the microstructure and biomechanical properties. To address this, we hypothesised ‘segmentation’ of a 3D printable design file by slicing and discretising with an array of thin solid “segments”, separated with an infinitesimal gap in a periodic manner. In this novel approach, the printing software commands the printhead to print each of the “segments” individually. The inter-segment and intra-segment binder “bleeding” among the segments results in a printed part with a homogeneously bound cross-section, without any “core-shell” effect. This hypothesis was experimentally validated by better microstructure, improved density, and enhanced mechanical strength properties in binderjet printed 3 mol% yttria stabilised ZrO₂.     

Effects of the molecular weight and CC functionality of poly 1-hexene on the properties of poly 1-hexene-based high impact polystyrene

Here we are aimed to unravel the effects of CC functionality and molecular weight of the rubber on the final properties of poly1-hexene-based high impact polystyrenes (HIPS). In this regard, various HIPS samples were synthesized by free radical polymerization of styrene in the presence of different weight fractions of various poly1-hexene-based impact modifiers including: (i) high molecular weight poly1-hexene (PHex), (ii) low molecular weight poly1-hexene (Olig), and (iii) 1-hexene/1,5-hexadiene copolymer (Copolym). Results showed that by increasing CC functionality from PHex to Oligm and Copoly, the degree of grafting increases which has its influence on the mechanical, thermal and morphological perspectives of the synthesized HIPSs. Besides CC unsaturation degree, the effect of rubber molecular weight on the final HIPS properties was studied as well. According to the results, molecular weight has significant effect on the final HIPS performance, too. Finally, our obtained results suggest new HIPS/Copolym sample as the one with the highest mechanical and thermal properties which is comparable well with commercial HIPS/polybutadiene grades. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47169.     

Effect of nanoclay on mechanical and thermal properties of triblock SBS (styrene–butadiene–styrene) and its binary blend nanocomposites: comparison between polyethylene and polystyrene

ABSTRACT

In this study, the effect of organo-modified nanoclay (OMMT) on the mechanical and thermal properties of SBS and its blend with low-density polyethylene (LDPE) and polystyrene was investigated. The effect of nanoclay content in the presence of LDPE or PS on the final properties of SBS was studied by tensile tester, dynamic mechanical thermal analysis (DMTA), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Addition of nanoclay affected the mechanical and rheological properties. From X-ray and DMTA results, it was found that due to more affinity between the nanoparticles and the SBS/PE blend, the 2 theta characteristic peak of nanoclay shifted to lower angles. SEM studies showed better dispersion and lower inter-particle distance of nanoparticles in SBS/PE composites in comparison with SBS/PS and SBS composites, confirming the XRD and DMTA results. It can be concluded that nanoclay acts as a compatibilizer in the SBS/LLDPE blend. TGA studies showed higher stability of SBS/PS composites compared to SBS and SBS/PE ones.     

Effects of molecular weight on poly(ω-pentadecalactone) mechanical and thermal properties

A series of poly(ω-pentadecalactone) (PPDL) samples, synthesized by lipase catalysis, were prepared by systematic variation of reaction time and water content. These samples possessed weight-average molecular weights (M_w), determined by multi-angle laser light scattering (MALLS), from 2.5 × 10⁴ to 48.1 × 10⁴. Cold-drawing tensile tests at room temperature of PPDL samples with M_w between 4.5 × 10⁴ and 8.1 × 10⁴ showed a brittle-to-ductile transition. For PPDL with M_w of 8.1 × 10⁴, inter-fibrillar slippage dominates during deformation until fracture. Increasing M_w above 18.9 × 10⁴ resulted in enhanced entanglement network strength and strain-hardening. The high M_w samples also exhibited tough properties with elongation at break about 650% and tensile strength about 60.8 MPa, comparable to linear high density polyethylene (HDPE). Relationships among molecular weight, Young's modulus, stress, strain at yield, melting and crystallization enthalpy (by differential scanning calorimetry, DSC) and crystallinity (from wide-angle X-ray diffraction, WAXD) were correlated for PPDL samples. Similarities and differences of linear HDPE and PPDL molecular weight dependence on their mechanical and thermal properties were also compared.     

The effect of silk fibroin nanoparticles on the morphology,rheology, dynamic mechanical properties,and toughness of poly(lactic acid)/poly(ε-caprolactone) nanocomposite

The silk fibroin nanoparticles (SFNPs) were extracted from silkworm cocoons and used as a nanofiller in poly(lactic acid) (PLA)/poly(ε-caprolactone) (PCL) blend. The nanoparticle localization was studied theoretically and experimentally and the effects of SFNP on the morphology, rheology, toughness, and dynamic mechanical properties of the blend were investigated. According to the calculated wetting coefficient, SFNP should be thermodynamically located in the PLA matrix during the melting process. The results of SEM illustrated a common sea-island structure for the PLA/PCL blend and the incorporation of SFNP reduced the PCL domain sizes from 1.170 ± 92 μm to 794 ± 46 nm. The atomic force microscopy results showed that the nanoparticles are mainly located in the PLA matrix and also, partially at the phase interface with a thickness of layers around 80 nm. The rheological tests displayed the network formation of SFNP in the prepared nanocomposites. The dynamic mechanical analysis revealed that by the addition of SFNP, the storage modulus of neat PLA and PLA/PCL blend were increased by around 57 and 50%, respectively and the glass transition temperatures (Tg) values of PLA and PCL shifted toward each other. Additionally, using SFNP caused a lower water uptake and higher impact strength (~64%) of the blend.     

Mechanism of in-situ formation of spinel and its effect on the mechanical properties of Al2O3–C refractories

This work looked at the in-situ formation mechanism of magnesia alumina spinel in Al₂O₃–C refractories with magnesia addition at different firing temperatures. A comprehensive study on the mechanical properties of Al₂O₃–C refractories was performed in comparison to traditional analogs. The magnesia alumina spinel was in-situ formed at the firing temperature of 1150 °C in Al₂O₃–C refractories. With the increase of the firing temperature, the Al₂O₃ phase was gradually dissolved in spinel phase to form aluminum rich spinel phase, resulting in a decrease in its lattice constant due to the defects formation. The formed spinel phase was homogenously distributed and bonded well with corundum, improving the interfacial bond, load transferring capacity and crack propagation resistance. The formation of spinel phase also enhanced the sintering of the alumina matrix owing to the solid solution of alumina in the spinel. Therefore, the mechanical properties such as cold modulus of rupture and hot modulus of rupture in Al₂O₃–C refractories achieved a substantial enhancement compared with traditional refractories.     

Demineralized whey–gelatin composite films: Effects of composition on film formation,mechanical, and physical properties

In this study, the objective was to prepare and characterize films with different concentrations of demineralized whey (3–10%) and gelatin (1–3%) containing glycerol (10–70%) as a plasticizer and chitosan or nanochitosan as an additive. Mechanical properties, thickness, grammage, opacity, moisture content, water, and ethanol solubilities of the obtained films were determined. The formation of films without glycerol and gelatin was not possible. A higher gelatin concentration led to more desirable mechanical properties. Thickness, grammage, opacity, and moisture content remained almost constant after increasing gelatin concentration. Heightening glycerol concentrations raised water and ethanol solubility. Despite presenting high water solubility, the films showed low ethanol solubility. The formulation containing whey (3%), glycerol (20%), gelatin (3%), and chitosan (0.1%) resulted in the highest performing film concerning physical and mechanical aspects. Through Fourier transform infrared spectroscopy analysis, it was possible to observe the displacement and the frequency reduction of the band near 3,300 cm⁻¹, revealing different protein interactions. It indicates that hydrogen bonds occur between the amino group and  OH of the protein molecules reducing film hydrophilicity. Contact angle measurements also showed a less hydrophilic character. The films present the potential to prolong the shelf life of food, such as dairy products.     

Yttrium substituted Co–Cu–Zn nanoferrite: A synergetic impact of Y3+ on enhanced physical properties and photocatalysis

Co_0.5Cu_0.25Zn_0.25Y_xFe_2-xO₄; (0≤x≤0.1; step 0.02) (CCZY) spinel ferrites were prepared by citrate technique. The prepared CCZY samples have crystallite sizes ranging from 21 to 34 nm. The nanoscale nature of the samples was, also, established by HRTEM micrographs. Even though the substitution route here involves the replacement of magnetic ions Fe³⁺ by a non-magnetic one Y³, the magnetization of CCZY nanoparticles did not show a continual decrease as expected. The nanoferrite Co_0.5Cu_0.25Zn_0.25Y_0.06Fe_1.94O₄, has a moderate value of saturation magnetization 63.45 emu/g (decreased with 11.55% than the pristine sample) and higher coercivity 416.44 Oe (increased with 21.83% than the pristine sample), which may be a suitable candidate for data storage applications. All CCZY nanoferrite have direct optical band gap within the range 1.57 eV–1.50 eV; which doesn't introduce a regular behavior with Y/Fe substitution process. Distinctively, the MB dye removal shows an optimum value with the nanoferrite CCZY (0.1), which gives a degradation efficiency of 95% after 60 min only. The outstanding increase in catalytic performance of the nanoferrite CCZY (0.1) was correlated with the size factor and saturation magnetization. The desirability function approach enabled to distinguish the optimal material (CCZY (0.1)) with the superior catalytic performance; the smallest size and convenient magnetic properties. Hence, the nanoferrite Co_0.5Cu_0.25Zn_0.25Y_0.1Fe_1.9O₄ can be utilized efficaciously for water treatment, via the safe photocatalytic process; without sabotaging the environment.     

Gasification of Brazilian coal-chars with CO2: effect of samples’ properties on reactivity and kinetic modeling

The gasification of coals obtained from important coalfields in Brazil was investigated in 1.0?bar of CO₂ using a thermogravimetric analyzer. Tests were carried out in two sequential steps: pyrolysis under N₂ at 1213 K and isothermal gasification under CO₂ in the temperature range of 1113–1213 K. The kinetic study was performed in the kinetically controlled regime and three gas-solid models were fitted to the experimental data. According to the results, subbituminous coal-chars presented higher reactivities than bituminous types, with maceral and ash compositions playing a key role in the overall process. The reaction rates increased with increasing temperature, with maximum values found in the conversion range of 10–60%. The random pore model that predicts a maximum point of reactivity over the reaction course suitably described the gasification kinetics. Values of activation energy between 146.63(±0.03) kJ/mol and 215.09(±0.05) kJ/mol were found, which are consistent to literature data of coals gasified worldwide. Despite the relatively high ash content (32–45%), the Brazilian coals appeared to be sufficiently reactive to be gasified, thus indicating the significance of this study to the development of gasification process in Brazil.     

The effect of dense polymer brush on the microfibrillated cellulose for the mechanical properties of poly(ε-caprolactone) biocomposites

Two different cellulosic fibers [pristine microfibrillated celluloses (MFCs) and 2,2-bis(hydroxymethyl)propionic acid-modified MFCs (bis-MPA-modified MFCs)] were grafted by poly(ε-caprolactone) (PCL) molecules through the ring-opening polymerization (ROP) method. The PCL-grafted MFCs were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and elemental analysis. The results showed that the grafting of PCL on the bis-MPA-modified MFCs was more efficient than that of the pristine MFCs due to the higher density of the activated hydroxyl groups on the bis-MPA-modified MFCs. Furthermore, the numerous PCL chains bound to the bis-MPA-modified MFCs (PCL-g-mMFC) demonstrated the stronger interfacial adhesion between the modified MFC fibers and the PCL matrix, as well as the greatly improved dispersion of the modified MFCs in the PCL matrix of the PCL/cellulose biocomposites.     

Agricultural use of three organic residues: effect on orange production and on properties of a soil of the ‘Comarca Costa de Huelva’ (SW Spain)

Disposal of urban, agricultural and industrial organic residues impliesan increasing problem because of all the economic and environmentalrepercussions involved. One of the most adequate ways of managing this problemis the agricultural use of these wastes as organic amendments. Three organicresidues (AC, olive mill waste water sludge compost; MWC, municipal solid wastecompost; and PS, paper mill sludge) were used in a 3-year field experimentinvolving orange production. The effect of their application on crop productionand on soil quality was investigated. Soil samples (0–20 cm depth)collected 11 months after the last soil amendment were analysed for: pH and EC,Kjeldahl-N, available-P, available-K, total organic carbon, humic substances,dehydrogenase, phosphatase, -glucosidase, urease andbenzoyl-argininamidehydrolysing protease (BAA-protease) activities. Generally, the application of the MWC and PSincreased orange yield when compared to control. Moreover, total organic carbonand humic substances significantly increased in soils treated with all theorganic amendments. Organic fertilisation increased the Kjeldahl-N andavailable-P contents of the soil. The application of the organic residues also causedsignificant increases in dehydrogenase, -glucosidase, urease andBAA-protease activities of the soil. Significant positive correlations (p <0.01) between these enzymatic activities and total organic carbon were foundforall treatments. Significant positive correlation between dehydrogenase, urease,-glucosidase, and BAA-protease and orange yield was also found. However,a clear inhibition of phosphatase activity was observed in soils treated withPS. The results indicate that the repeated application to the soil of moderateamounts of organic amendments has positive effects on the chemical andbiochemical properties of the soil, as well as on the orange yield.     

Effect of polytetrafiuoroethylene on flame retardancy and mechanical properties of silicone rubber filled with Mg ( OH ) 2/Al ( OH ) 3 complex

研究了聚四氟乙烯(PTFE)对Mg(OH)2/Al(OH)3填充硅橡胶阻燃性能和力学性能的影响.结果表明,PTFE不但能够改善硅橡胶的阻燃性能,而且还能使力学性能尤其是撕裂强度得到显著提高.当PTFE用量为2.5份(质量),撕裂强度达17.1 kN·m-1,比不含PTFE的试样提高了51%,而且其极限氧指数也有一定增加.     

Effect of cobalt-60 γ radiation on the physical and chemical properties of poly(ethylene terephthalate) polymer

The structural, optical, and morphological properties of Co⁶⁰ γ irradiation on poly(ethylene terephthalate) polymer samples were studied with X-ray diffraction (XRD), ultraviolet–visible spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy. The diffraction pattern of virgin sample showed that the polymer was semicrystalline in nature. However, because of irradiation, the crystallinity decreased up to a dose level of 110 kGy and increased up to 300 kGy. The crystallite size, strain, and dislocation were calculated from the XRD data, and the crystallite size decreased from 291.07 to 346.90 Å. The absorption edge shifted from 315 to 330 nm, and the band gap of the samples decreased from 3.79 to 3.66 eV. The SEM micrographs showed radial bulging along with inhomogeneous liner exfoliation, and also, a rocky shape pattern with different sizes was observed. A significant change was found in the Raman spectra of the γ-irradiated polymer at the highest dose. The results of the structural, optical, and morphological studies show recovery characteristics at the highest dose level of 300 kGy. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Production, mechanical properties and in vitro biocompatibility of highly aligned porous poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) scaffolds

We produced highly aligned porous poly(ε-caprolactone) (PCL)/hydroxyapatite (HA) scaffolds by unidirectionally freezing PCL/HA solutions with various HA contents (0, 5, 10 and 20 wt% in relation to the PCL polymer) and evaluated their mechanical properties and in vitro biocompatibility to examine their potential applications in bone tissue engineering. All the prepared scaffolds had a highly aligned porous structure, in which the HA particles were uniformly dispersed in the PCL walls. The elastic modulus of the PCL/HA scaffolds significantly increased from 0.12 ± 0.02 to 2.65 ± 0.05 MPa with increasing initial HA content from 0 to 20 wt%, whereas the pore size decreased from 9.2 ± 0.7 to 4.2 ± 0.8 μm. In addition, the PCL/HA scaffolds showed considerably enhanced in vitro cellular responses that were assessed in terms of cell attachment, proliferation and osteoblastic differentiation.     

Structure and physical properties of Ba(PO3)2–AlF3–BaSO4 fluoro-sulfo-phosphate glasses

Alkali-earth-metaphosphate-based fluoro-sulfo-phosphate M(PO₃)₂–AlF₃–MSO₄ (MPFS, M = Ca, Sr, Ba) glasses have been developed via simultaneously incorporating fluoride and sulfate into metaphosphate glass. Their glass-forming regions were efficiently determined under the guidance of thermodynamic calculation method. The physical and structural properties of BaPFS glass were investigated in detail. Furthermore, near-infrared spectroscopic properties of Er³⁺-doped BaPFS (Er–BaPFS) glass were studied. Physical parameters, such as Abbe's number ν_d (55-75) and nonlinear refractive index n₂ (1.17-1.86 × 10⁻¹³ esu), of BaPFS glass are strongly depended on P/F/S ratio. The structure of BaPFS glass gradually depolymerizes and tends to become multianionic when Ba(PO₃)₂ is substituted by AlF₃ and BaSO₄. Anion-substitution strategy effectively modulates the property and structure of glass, providing a scheme to derive glass materials. In addition, enhanced emission at ~1.5 μm has been observed from Er–BaPFS glass along with large emission cross section (5.0-5.5 × 10⁻²¹ cm²) and long lifetime (6.7-7.3 ms), resulting in large figure of merit (3.46-3.84 × 10⁻²³ cm²·s), which is a promising candidate for solid-state laser.     

Study on the effect of Ti,Al, Cu,and Ag doping on the bonding properties of soldered β-Sn(100)/ZrO2(111) interface

Selecting active elements for filler metal is very important in soldering of ZrO₂ ceramics. In this paper, the effects of Ti, Al, Cu, and Ag active elements on the bonding strength and electronic structures of soldered β-Sn(100)/ZrO₂(111) interface were studied via the method of first principle calculation. The work of adhesion (W_ad) results show that the O₂-terminated interface is more stable than other kinds of interfaces. Then, the atoms of Ti, Al, Cu, and Ag were doped into the interface by replacing the Sn atom in situ. It is found that additions of Ti, Al, and Cu atoms can increase the W_ad, and Ag atom has the opposite effect. From the results of heat of segregation, doping Ti and Al into the interface is stable in thermodynamics and doping Cu and Ag is not stable. The forming of strong ionic-covalent Ti-O and Al-O bonding contributes to the increase of the interfacial adhesion strength. The calculation results indicate that Ti and Al can act as active elements in Sn to solder ZrO₂. The Ti-O and Al-O compounds formed at interface can improve the wetting and bonding between Sn-based solder and ZrO₂ ceramics.     

Effect of two-step sintering on microstructure and mechanical properties of ceria-stabilized zirconia-toughened alumina-added titania (CSZTA–TiO2)

Effect of two-step sintering (TSS) on microstructure and mechanical properties of ceria-stabilized zirconia-toughened alumina with added TiO₂ (CSZTA–TiO₂) was studied. A coprecipitation technique was used to produce the CSZTA–TiO₂ powders. The synthesized powders were compacted using a uniaxial hydraulic press and conventionally sintered in air. The phase and microstructure of sintered samples were studied using X-ray diffraction and scanning electron microscopy techniques. Phases were quantified using the Rietveld refinement method. Different TSS schedules were followed to optimize microstructure and mechanical properties. Mechanical properties of the CSZTA-4TiO₂ composite were evaluated and found as follows: Vickers's hardness of 1650 ± 9.6 HV10, indentation fracture toughness of 8.45 ± .14 MPa √m, compressive strength of 2088 MPa, and Young's modulus of 158 GPa.     

MoSi2–Si3N4 composites: Influence of starting materials and fabrication route on electrical and mechanical properties

The fabrication method and the mechanical and electrical properties of different MoSi₂–Si₃N₄ composite materials were investigated. Commercially available individual compounds, one-stage combustion synthesized MoSi₂–Si₃N₄ and submicron MoSi₂ powders were used as starting materials, followed by hot pressing. It was found that the sintering atmosphere used, nitrogen or argon, had a significant effect on the phase composition, mechanical and electrical properties of the final materials. It was shown that in some cases partial nitridation of MoSi₂ occurred with the formation of MoSi₂–Mo₅Si₃–Si₃N₄ ternary composites. The electrical conductivity of the composites depends also on the microstructure of materials. It was shown that the composites fabricated using combustion synthesized MoSi₂ powders (500 nm) are characterized by higher flexural strength at room temperature compared to those from commercial powders. On the other hand, the composites fabricated from the commercial powders had higher strength and fracture toughness at elevated temperatures (up to 1200 °C). For all composites, the strength decreased significantly at temperatures over 1000 °C due to the brittle–ductile transition of the MoSi₂ phase.     

Effect of yttria substitution on structure,optical and mechanical properties of (Gd,Y)2O3–MgO nanocomposite ceramics

A citrate-nitrate combustion method was applied to synthesize fine composite Gd_2-xY_xO₃-MgO (x = 0, 0.02, 0.2, 0.3, 0.4, 0.6) nanopowders. Y₂O₃ substitution inhibited Gd₂O₃ phase transition from cubic structure to monoclinic structure during sintering, thereby stabilizing its cubic structure to room temperature. This approach led to nanocomposite ceramics with a grain size of about 190 nm and increased the transmittance to 85% over the 3–5 μm wavelength range when x = 0.3. However, the addition of Y₂O₃ weakened the mechanic properties of the nanocomposite ceramics.