Showing papers in "Journal of Macromolecular Science, Part B in 2022"

Empirical Determination of the Internal Energy of Polyethylene based on the Pressure-Volume-Temperature-Entropy Equation of State

Abstract: Abstract The internal energy, U, of polyethylene (PE) was determined by the relations that and the pressure-volume-temperature-entropy equation of state (P-V-T-S Eos) evaluated by the experimental P-V-T data and Cp at 1 atm for PE where CV is the isochoric heat capacity, is the thermal pressure coefficient and CP is the isobaric heat capacity. The 3-dimensional (3D) plot, 3D plot, with the three axes, x = VU, y = SU, z = TU expressed by the 3D (VU , SU , TU ), the 3D (TU, PU. SU ) or the 3D (TU , VU, PU ) at constant U in PE were determined where the four variables, PU , VU , TU , and SU were determined under U being constant. The P-V-T-S behaviors under the iso-internal energy process where U is constant were monitored by the 3D (VU, SU, TU ). The 3D (V, T, P) plot for PE under were expressed by a line not a plane

Thermal, Optical, and Color Modification in Makrofol VLG 7-1 Nuclear Track Detector Due to Gamma Irradiation

Abstract: Abstract Makrofol VLG 7-1 is a sort of Makrofol (bisphenol-A polycarbonate) nuclear track detector. We believe that the current study is the first one that deals with the effect of γ-ray irradiation on Makrofol VLG 7-1. Samples of Makrofol films were treated with various γ-ray dosages (20–140 kGy). The resultant outcome of the γ-ray irradiation on the thermal and optical characteristics of the Makrofol samples were explored applying thermogravimetric analysis (TGA) and ultraviolet spectroscopy (UVs). The degradation temperature, activation energy of thermal decomposition, optical band gap, refractive index, Urbach energy, and optical dielectric parameters were characterized and interpreted based on the γ-ray dosage. The optical bandgap dropped from 4.26 to 4.14 eV for a γ-ray dosage of 140 kGy, accompanied with a rise in both Urbach energy and thermostability of the samples. We attribute this to the dominance of crosslinking. Additionally, the color differences between the pristine and the irradiated samples were characterized. The pristine Makrofol was uncolored. It exhibited noteworthy color changes during the γ-ray treatment, as the color intensity reached a value greater than 5. This is an acceptable match in commercial reproduction on printing presses.

Empirical Determination of the Pressure–Volume– Temperature–Entropy Equation of State of Polyethylene in Isothermal, Isobaric and Isochoric Ensembles: II. Correlation Between the Equations of State in the Various Ensembles

Abstract: Abstract The pressure–volume–temperature–entropy equations of state, P–V–T–S Eos, of polyethylene (PE) for its isothermal, isobaric and isochoric ensembles were reported in our previous report (Part 1). In this report the correlation between the P–V–T–S Eos in the various ensembles was analyzed quantitatively where it was found that the three dimensional P–T–V plane for the PT –T–VT Eos in the isothermal ensemble was almost the same as that for the P–TP –VP Eos in the isobaric ensemble, while the 3D T–P–S plane for the T–PT –ST Eos in the isothermal ensemble was almost the same as that for the TP –P–SP Eos in the isobaric ensemble where the subscript of T and P mean isothermal and isobaric ensembles, respectively. The isothermal bulk modulus, and its first and second pressure derivatives and were calculated and it was found that the 3D T–PT – plane in the isothermal ensemble was almost the same as that for the TP –P– in the isobaric ensemble, and the 3D T–PT – plane in the isothermal ensemble was different only slightly from the 3D TP –P– plane in the isobaric ensemble, while a considerable difference was observed between the 3D T–P– planes for the isothermal and isobaric ensembles.

Empirical Determination of the Isoenthalpic and Isoentropic Equations of State of Polyethylene Based on the Pressure–Volume–Temperature–Entropy Equation of State

Abstract: Abstract The isoenthalpic and isoentropic equations of state of polyethylene (PE) have been determined based on the empirical pressure–volume–temperature–entropy equation of state, P – V – T – S Eos. The three dimensional plot, 3D plot, for the isoenthalpic Eos consists of the variables pressure (PH ), volume (VH ), temperature (TH ), and entropy (SH ) satisfying the condition that the enthalpy, H, is constant, while the 3D plot for the isoentropic Eos consists of the PS , VS , TS and HS satisfying the condition that the entropy, S, is constant. The 3D TH – PH – VH plot determined for the isoenthalpic Eos for PE showed a considerable difference from the 3D TS – PS – VS plot for the isoentropic Eos for PE. The thermodynamic derivative, for the isoenthalpic Eos with constant H in PE was positive, while the for the isoentropic Eos with constant S was negative. Thermodynamic derivatives for the isoenthalpic and isoentropic equation of state have been evaluated based on the experimental 3D plots and discussed in terms of the thermodynamic relations.

Phase Structure Analysis and Composition Optimization of Poly(Lactic Acid)/Poly(Butylene Adipate-co-terephthalate) Blends

Abstract: Poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends with different mass ratios of PLA and PBAT (PLA/PBAT: 100/0, 80/20, 60/40, 40/60, 20/80, and 0/100) were prepared by a monomer melt blending method. The processability, mechanical properties, microstructure, thermal properties of the PLA/PBAT blends were tested. The change of phase structure of the PLA/PBAT blends with different proportions of its components was characterized and the relationship between phase structure and mechanical properties was determined. The results showed that the PLA/PBAT (80/20) blend had the best comprehensive performance of the blends with different properties; the torque test results showed that the maximum torque and balance torque of the PLA/PBAT (80/20) blend were 5.67% and 38.67% lower than those of PLA, respectively, while the mechanical properties tests showed that the impact strength of PLA/PBAT (80/20) blend was 4.27 times that of PLA. SEM test results showed that there were a large number of PBAT doming uniformly dispersed in the PLA matrix in the form of microbeads in the PLA/PBAT (80/20) blend while the results of the TGA tests showed that the Ts and T50% of the PLA/PBAT (80/20) blend increased by 3 °C and 6 °C compared to PLA, respectively, and the DSC tests results showed that the cold crystallization temperature of the PLA/PBAT (80/20) blend was 16 °C lower than that of PLA.

Antibacterial Activity of AgNO3 Incorporated Polyacrylonitrile/Polyvinylidene Fluoride (PAN/PVDF) Electrospun Nanofibrous Membranes and Their Air Permeability Properties

Abstract: Abstract Polyacrylonitrile (PAN)/polyvinylidene fluoride (PVDF) nanofibers incorporated with AgNO3 in various concentrations were produced as membranes and investigated for their antibacterial properties and air permeability. To characterize the AgNO3 incorporated PAN/PVDF nanofibers Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Fourier-Transform Infrared (FT-IR) Spectroscopy, the Brunauer–Emmett–Teller (BET) method and air permeability analyses were carried out. Based on the SEM results, the prepared nanofibers had a smooth and beadless surface. For 20 wt% PVDF concentration, AgNO3 addition up to 20 wt% did not disrupt the fiber structure. The antibacterial activity of the AgNO3 incorporated PAN/PVDF nanofibrous membranes were investigated against bacterial strains of E. coli and S. aureus. For each AgNO3 concentration from 5 wt% to 20 wt%, the PAN/PVDF nanofibrous membranes showed antibacterial activity in correspondence with the measured inhibition zones. However, the 10 wt% AgNO3 concentration was found to be the optimum concentration providing desirable nanofiber morphology and antibacterial properties. Air permeability findings of the nanofibrous membranes did not show a significant difference for the tested AgNO3 concentrations. In summary, the results indicated that AgNO3 incorporated PAN/PVDF nanofibrous membranes are appropriate for use as air filtration materials.

A Thermal Conductive Epoxy Composite based on Spherical MgO Particles and Boron Nitride Sheets

Abstract: Abstract The performance and life of high-power electronic devices are closely related to heat dissipation. Preparing high thermal conductivity, electrically insulating, polymer-based packaging materials for electronic devices is critical to achieving high heat dissipation. In the research described here spherical magnesium oxide (MgO) particles of various sizes and boron nitride (BN) sheets were used to prepare epoxy composites and their enhancement of heat transfer was investigated. In addition, the BN sheets were surface modified by γ-aminopropyltriethoxy silane (APTES) to increase interfacial compatibility between epoxy resin and BN, which enhanced the composite thermal conductivity. The composites with the highest thermal conductivity were made with 5 µm spherical MgO particles and BN sheets at a filler wt% ratio of 3:1 (MgO: BN). Using functionalized BN sheets enhanced the dispersion and compatibility of the 3:1 mixed filler. The thermal conductivity of the composite containing 45 wt% of the 3:1 mixed filler consisting of 5 µm spherical MgO particles and APTES functionalized BN sheets was 0.92 W/(m·K) as compared to 0.2 W/(m·K) for the epoxy resin alone.

Rheological, Mechanical, and Thermal Properties of Ultrahigh Molecular Weight Polypropylene/Low Molecular Weight Polypropylene Blends

Abstract: Abstract Ultra-high molecular weight polypropylene (UHMWPP), with a molecular weight of more than 106 g/mol, is expected to have superior properties, such as high mechanical strength, high thermal properties, high chemical resistance and outstanding tribological properties. However, UHMWPP has a very poor processability due to its high melt viscosity. Therefore, we aimed to improve processability of UHMWPP by blending it with a low molecular weight polypropylene (LMWPP). We attempted to improve the interfacial miscibility and intermolecular entanglement of the UHMWPP/LMWPP system by using a kneader machine. The addition of LMWPP tended to change the mechanical, thermal, and rheological properties of the blend system.

Effect of a Novel Graphene on the Flame Retardancy and Thermal Degradation Behavior of Epoxy Resin

Abstract: Abstract The effect of graphene modified with a phosphorus and silicon-containing compound (GO-DOPO-V) on the flame retardancy and thermal stability of epoxy resin (EP) was studied by cone calorimetry and thermogravimetric analysis (TGA) in nitrogen. After incorporation of 2 wt% GO-DOPO-V into EP, maximum decreases of 28.8% in peak heat release rate (pHRR) and 15.6% in total heat release (THR) were achieved compared to that of pure EP. It was shown that GO-DOPO-V significantly promoted the formation of an EP tight char layer and the char residue of EP/GO-DOPO-V composite at 600 °C was 13.39 wt%, which was almost twice that of pure EP. Furthermore, the non-isothermal degradation behavior of EP/GO-DOPO-V composites were investigated also in a nitrogen atmosphere. It was found that the addition of GO-DOPO-V changed the degradation behavior of EP composites in the early and middle stages. Both the Kissinger and Flynn–Wall–Ozawa methods revealed that the addition of GO-DOPO-V increased the thermal degradation activation energy of EP, and improved the flame retardancy of the polymer matrix.

Influence of the Matrix Molecular Weight on the Morphology and Properties of Poly(Ethylene Terephthalate)/Poly(Ethylene-Octene) Blends

Abstract: Abstract Poly(ethylene terephthalate)/poly(ethylene-octene) (PET/POE) blends compatibilized with glycidyl methacrylate grafted poly(ethylene-octene) (mPOE) were prepared by melt blending using a twin screw extruder. The effects of the molecular weight of the PET matrix on the morphology and properties of the PET/POE/mPOE blends are described. The results of the SEM analysis showed that the average particle diameters of the dispersed phase decreased with an increase in the PET molecular weight. The results of the mechanical property tests showed that the notch Charpy impact strength and elongation at break of the PET/POE/mPOE blends improved with an increase in the PET molecular weight. However, the flexural strength, flexural moduli and tensile strength were nearly unchanged. The crystallization rate of PET in the PET/POE/mPOE blends improved with decreasing PET molecular weight.

Empirical Determination of the Partition Function of Polyethylene Based on Its Pressure-Volume-Temperature-Entropy Isochoric Equation of State. II. The Pressure and Entropy Expressed by the Modified Partition Function

Abstract: Abstract In our previous report, an empirical partition function, for polyethylene (PE) was determined based on a pressure (PV ) – temperature (TV ) – volume (V) – entropy (SV ) equation of state where the variables, PV , TV and SV , were isochoric variables with V = const. evaluated by using the experimental P-V-T data and the isobaric heat capacity, CP , at 1 atm. In this work we describe the proposal of a modified, reformed partition function of the Debye model, where the is expressed by the summation of the terms of T, T −1 and T 3 and the Boltzmann factors of for i = 1, 2, 3 and 6. The modified reformed pressure, at constant volume calculated based on the showed that the Boltzmann factors, for i = 3 and 6 were dominant and increased with increasing temperature and the terms were negative and decreased with increasing temperature, while the modified reformed entropy, showed that the Boltzmann factors of for i = 3 and 6 were also dominant and increased with increasing temperature and the term increased rapidly over a higher temperature range. All Boltzmann factors of for i = 1, 2, 3 and 6 in the modified reformed isochoric heat capacity, CV,m-RD , calculated based on the were positive, which was different from that in the previous work where one negative Boltzmann factor was observed.

Largely Improved Mechanical Properties of Polyurethane Nanocomposites via In Situ Polymerization with Low Loading of Graphene Oxide

Abstract: Abstract Polyurethane nanocomposites were prepared and reinforced by graphene oxide (GO) via in situ polymerization. A two-step solvent-replacement process was used to perfectly disperse GO in the PU nanocomposites. The composites exhibited significant improvement in mechanical properties. With only a small amount (0.02 wt%) of GO, the tensile strength showed an increment of 60%. The interfacial interaction between GO and the polymer matrix was deeply investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy, and thermogravimetric analysis. The results showed that the thickness and thermal stability of the polymer-grafted-GO increased obviously. The extreme improvement of the mechanical properties is attributed to the excellent dispersion of GO in the matrix and the strong interfacial interaction. In addition, the resiliency of the PU–GO nanocomposites is still outstanding.

Rheological, Mechanical and Thermal Properties of Ultrahigh Molecular Weight Polypropylene/Low Molecular Weight Polypropylene Blends

Abstract: Ultra-high molecular weight polypropylene (UHMWPP), with a molecular weight of more than 106 g/mol, is expected to have superior properties, such as high mechanical strength, high thermal properties, high chemical resistance and outstanding tribological properties. However, UHMWPP has a very poor processability due to its high melt viscosity. Therefore, we aimed to improve processability of UHMWPP by blending it with a low molecular weight polypropylene (LMWPP). We attempted to improve the interfacial miscibility and intermolecular entanglement of the UHMWPP/LMWPP system by using a kneader machine. The addition of LMWPP tended to change the mechanical, thermal, and rheological properties of the blend system.

Preparation and Properties of Sodium Alginate/Silk Fibroin Microcarriers

Abstract: Abstract Injectable porous microcarriers, with excellent biocompatibility, biodegradability, high cell seeding density and simple implantable procedures in the body, have been widely used in bone tissue engineering. In this work sodium alginate/silk fibroin (SA/SF) porous microcarriers were prepared cross-linked by SrCl2 or CaCl2 using emulsion method combined with freeze-drying method. The morphology and structure of the microcarriers were characterized by scanning electron microscopy (SEM). The cell proliferation ability and osteogenic activity of the microcarriers were investigated by culturing rat bone marrow mesenchymal stem cells (rBMSCs). The SA/SF microcarriers showed an interconnective porous structure with an average particle size of 254.3 ± 50.0 μm and an average pore size of 42.0 ± 5.3 μm. The SA/SF microcarriers cross-linked with SrCl2 showed higher cell proliferation ability and osteoinductive ability than those cross-linked with CaCl2. These features indicated that the designed SA/SF microcarriers are ideal for tissue engineering.

Empirical Determination of the Internal Energy of Polyethylene Based on the Pressure-Volume-Temperature-Entropy Equation of State. II. The Revised Internal Energy Based on the Zero Kelvin Isotherm

Abstract: Abstract In our previous reports, two types of the internal energy for polyethylene (PE) were derived, which were based on the thermodynamic relation that and based on the partition function, that where CV is the isochoric heat capacity, is the thermal pressure coefficient and is the Boltzmann factor. In this work, a revised internal energy based on the UTH, Urev.TH , was derived by introducing a zero Kelvin internal energy. A revised internal energy based on the UPF , Urev.PF , was also derived by introducing the zero Kelvin internal energy. The zero Kelvin internal energy, U(V, T = 0 K), was determined based on a zero Kelvin isotherm, which was determined from the P-V-T equation of state derived in our previous work. In this report, the three-dimensional (3D) plot, 3D plot, with the three axes, x = TU, y = PU, z = VU expressed by the 3D (TU , PU , VU ) and the 3D (TU, VU. SU ) at constant U in PE were determined by the Urev.TH where the processes were characterized by decreasing of the volume and the entropy with increasing of the pressure, while the temperature in the iso-internal process had a maximum with increasing the pressure, which were different from those determined by the UTH in our previous work. The revised internal energy Urev.PF was expressed by the summation of the terms of T 2 and T 4, the Boltzmann factors and the U(V,T = 0 K) where the temperature dependence of the T 4 term and the Boltzmann factors with i = 6 and 3 were dominant in the Urev.PF at V = 1.04 cm3/g, while at V = 0.85 cm3/g in the range of high pressure, the U(V,T = 0 K) became a controlling factor. In the case of the U rev,PF at constant temperature T = 320 K, the volume dependence of the T 2 term and the U(V,T = 0 K) were dominant factors.

In-Vitro Degradation Behaviors of Composite Scaffolds Based on Poly(Lactide-co-Glycolide-co-ε-Caprolactone), 1,4-Butanediamine Modified Poly(Lactide-co-Glycolide) and Bioceramics

Abstract: Abstract In this work a novel type of composite scaffolds based on poly(lactide-co-glycolide-co-ε-caprolactone) (PLLGC), 1,4-butanediamine modified poly(lactide-co-glycolide) (BMPLGA), nanobioactive glass (NBAG) and β-tricalcium phosphate (β-TCP) were fabricated by using a thermally induced phase separation (TIPS) method. The in-vitro degradation behaviors were investigated by immersing the scaffolds in phosphate buffered saline (PBS, pH = 7.27) solution at 37 °C for 40 days. The properties, including the PBS pH value change and the water uptake, mass loss and morphology changes of the composite scaffolds, were investigated by comparing with pure PLLGC/BMPLGA scaffolds. The introduction of NBAG and β-TCP nanoparticles decreased the degradation rate of the PLLGC/BMPLGA matrix and improved the wetting behavior. The decrease in the degradation rate of the composite scaffolds correlated well with the results obtained from mass loss, water uptake and pH measurements. The degradation rate of the PLLGC/BMPLGA polymer in the composite scaffolds decreased as a result of the alkaline effect of the NBAG and β-TCP particles, with the OH- ions formed neutralizing acidic polymeric degradation products and binding the H+ ions from the tissue fluids.

Study of the Diamagnetic Properties of Liquid Polydimethylsiloxane (PDMS) with the Moses Effect

Abstract: Abstract The relationship between the magnetic susceptibility and degree of polymerization of liquid polydimethylsiloxane (PDMS) was studied experimentally. The magnetic susceptibility of the liquid PDMS was established with the Moses effect, i.e., study of the shape of the near-surface well (the well created near the surface-vapor interface) created in the liquid by a permanent magnetic field. The study of the shape of the near-surface well was carried out under experimental registration of the laser beam reflected from the PDMS/air interface. The broad range of available molecular weights of PDMS made it suitable for the study. The diamagnetic susceptibility, of PDMS was measured for a broad range of molecular weights. The plot of magnetic susceptibility, χ, against the number of repeating units in the chain, n, was linear. The result was compared with the magnetic susceptibility predicted by the Pascal law. The volume magnetic susceptibility of the liquid PDMS was established as = (−7.77 ± 0.06) · 10−6. The magnetic susceptibility of the PDMS monomer was established as χexp (n = 1) = (60.3 ± 0.32) · 10−11, which is in a satisfactory agreement with the Pascal empirical rule.

Improvement in Thermal Conductivity of Through-Plane Aligned Graphite Flake/Silicone Modified Epoxy Resin Composites

Abstract: Abstract We describe, here, our study of the thermal conductivity (TC) properties of silicone modified epoxy resin (SEP) films which were prepared by blending low molecular weight SH-023-7 silicone resin with Dow 332 epoxy resin as the matrix of composites using graphite flakes (GF) as a thermally conductive filler. The SEP/GF composites with different filler contents and SEP/vertically aligned GF (AGF) composites utilizing various magnetic field intensities were fabricated, and the TC, and thermal stability (TS) were characterized by thermal gravimetric analysis, and the morphology was observed by scanning electron microscopy (SEM). According to the experimental results, both the TC and TS increased with the increasing addition of filler. When the weight fraction of M (M = ) was 60 wt%, the TC of the composites was 1.38 W/mk, which was 5.52 times higher than that of pure SEP (0.25 W/mK). In addition, the addition of graphite also increased the decomposition temperature of the composites. The vertically aligned GFs resulted in effective, vertical, thermally conductive pathways in the SEP matrix, and the SEP/AGF composites exhibited much higher through-plane TC compared to the non-orientated SEP/GF composites. The SEP/AGF reached 5.66 W/mK, which was approximately 4.1 and approximately 23 times higher than 60 wt% SEP/GF and pure SEP, when the nano-Fe3O4 content was 0.4 g, the strength of magnetic field was 0.65 T and the added amount of M was 60 wt%. In addition, by SEM observation, when the flake graphite was found in the direction of the magnetic field orientation, the graphite formed heat conduction channels touching each other in the magnetic field direction, improving the TC. Using XRD analyses the orientation degree of the graphite in the composite showed that the graphite obviously changed its internal orientation in the composite material when subjected to the magnetic field in the SEP melt.

Ultrahigh Low-Temperature Toughness of Polypropylene Composites with Low Ductile-Brittle Transition Temperature by Introducing Traces of Needlelike Wollastonite

Abstract: Abstract In order to survive harsh settings, such as outer space, deep sea and high plains, needlelike wollastonite fibers (WF) were incorporated into polypropylene/ethylene octene block copolymer/β-nucleating agent (PP/OBC/β-NA) blends with the hope of tailoring the low-temperature toughness. The results revealed that WF showed very satisfactory toughening effects in the PP/OBC/β-NA/WF composites at low temperature (–20 °C). The impact strength of the WF-0.05 was as high as 32.1 kJ/m2 at −20 °C, which was 286.6% higher than that of the WF-0 sample, and even 832.6% higher than that of the pure PP sample. SEM characterization showed that by simultaneously adding WF and β-NAs, much coarse and tremendous plastic deformation appeared in the WF-0.05 after impacting. The low-temperature toughening mechanism is systematically discussed. The increase of β-crystallinity, caused by the synergy of β-nucleating agent and WF fillers, was mainly responsible for the enhancement of the impact strength of the composites with WF. On the other hand, when the transmitting of the stress, the overlapping of the stress and the hindering effect of WF on cracks occurred simultaneously; it resulted in the excellent low temperature toughness of the PP composites. Such outstanding-performance material with the advantages of facile processing and low cost is unprecedented. It shows a promising future application in many fields, especially aerospace, navigation, and the automotive industry.

Preparation and Adsorption Performance of Cellulose Acetate Fiber-Chitosan/Titanium Dioxide Surface Layers Composite Membranes Prepared Based on a Sol-Gel Method

Abstract: Abstract CA/CS/TiO2 composite membranes were formed by cellulose acetate (CA) electrospun fibers which were used as the basal layer, and chitosan (CS)/sol-gel titanium dioxide (TiO2) which was coated as a surface layer on one side. The composite membrane exhibited a smooth and flat surface when the CS:TiO2 ratio was 10:1 (mass ratio) and the CA:CS ratio was 12:10 (volume ratio). This layered structure of the membrane exhibited a water flux of 119 L/(m2·h). Adsorption testing of this composite membrane for dyes showed that the adsorption capacities of methylene blue and rhodamine were 42 and 51 mg/g, respectively. The composite membrane showed better adsorption performance for rhodamine mainly because of the bonding between the hydroxyl groups of CS and TiO2 and the carboxyl groups of the rhodamine dye. The adsorption processes of the two dyes were in accord with a second-order kinetic equation.

Preparation and Characterization of Poly(lactide-co-glycolide-co-ε-caprolactone)- 1,4-Butanediamine-Modified Poly(lactide-co-glycolide)/Nano-Biaoactive Glass-β-Tricalcium Phosphate Composite Scaffolds

Abstract: Abstract Polymer/bioceramic composite scaffolds have gained importance in treating bone defects. In this paper we described a novel degradable scaffold material for bone tissue repairing prepared by combining poly(lactide-co-glycolide-co-ε-caprolactone) (PLLGC) and 1,4-butanediamine-modified poly(lactide-co-glycolide) (BMPLGA) with nano-biaoactive glass (NBAG) and nano β-tricalcium phosphate (β-TCP). The composite scaffolds were characterized by using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The FTIR results indicated that the inorganic fillers of NBAG and β-TCP were successfully incorporated into the PLLGC/BMPLGA matrix. The influences of the inorganic filler content and freezing temperature on the porosity and compressive strength of the composite scaffolds were studied. The composite scaffolds showed an interconnected pore structure with the pore size ranging from 20 to 100 μm depending on the freezing temperature and the inorganic fillers. The compressive strength was enhanced with increasing content of the inorganic fillers and the freezing temperature; however, the porosity decreased. We suggest the PLLGC-BMPLGA/NBAG-β-TCP composite scaffolds have great potential for application in bone tissue regeneration.

Tailoring the Microstructural, Optical, and Magnetic Properties of MgFe2O4 Nanoparticles Capped Polyethylene Glycol Through a Bio-Inspired Method

Abstract: Abstract Ferrite materials have found applications in numerous areas, chiefly for hyperthermia in cancer therapy, targeted drug delivery and photodegradation. In this work, magnesium ferrite nanoparticles (MgFNPs) were formulated using polyethylene glycol (PEG) as a capping agent to tailor the properties and heighten the biocompatibility for suitable biomedical applications. The characterization results clearly showed the effect of PEG tailoring the properties of the formulated MgFNPs. A crystallite size with a value between 16 and 91 nm was determined from the X-ray diffraction (XRD) analysis. The scanning electron microscopy (SEM) analysis showed particles of spherical shape for all the samples and the particle size was enhanced as the concentration of PEG increased. The vibrating sample magnetometer (VSM) showed a ferromagnetic nature for the samples with reduced saturation magnetization as the concentration of PEG was increased. The PEG concentration heightened the properties of the sample and can be highly optimized for suitable biomedical applications.

Influence of Carbon Nanotubes Purity on the Properties of Carbon Nanotubes/Low-Density Polyethylene Composites

Abstract: Abstract The influence of carbon nanotubes (CNTs) purity on the viscosity, thermal properties, impedance characteristics, and conductivity of CNT/low-density polyethylene (LDPE) nanocomposites was investigated. Two grades of CNT of similar aspect ratios but with different levels of carbon purities were investigated. CNTs with 90% ( and 95% ( carbon purity were used. The impedance analysis showed a lower electrical percolation threshold (EPT) of the compared to the . Also, at the same nanofiller loading, the characteristic frequency ( ) of the composites was higher than that of the composites. For example, at 7 wt% CNT, the of the and composites were 102 and 1.0 Hz, respectively. This finding reveals better dispersion of the compared to the in the LDPE. The better dispersion of CNT90 compared to CNT95 in the LDPE is supported by the processing behavior analysis that showed higher viscosity and mixing torque for the composites compared to the composites.

Fabrication and Characterization of Zwitterionic Coatings with Anti-oil and Anti-biofouling Activities

Abstract: Abstract Underwater ultraoleophobic materials with superhydrophilic surfaces have great potential for several applications due to their anti-fouling, self-cleaning, oil/water separation, droplet manipulation, and drag reduction properties. In our research described here an underwater ultraoleophobic coating containing zwitterion carboxybetaine acrylamide (CBAA) was prepared using self-polymerization of dopamine (DA) and co-deposition of polydopamine (PDA) with zwitterionic poly(carboxybetaine acrylamide) (PCBAA) based on hydroxyl radical activation. The morphology of the coatings could be easily controlled by adjusting the initial ratio of dopamine/carboxybetaine acrylamide (DA/CBAA). The structures, surface morphologies and properties of the coatings so obtained were analyzed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements. The polydopamine/poly(carboxybetaine acrylamide) (PDA/PCBAA) coatings exhibited excellent superhydrophilicity and underwater superoleophobicity with water contact angles (WCA) of 1.5° and underwater oleophobicity contact angles (OCA) of 160°. The anti-biofouling, oil-water separation, and mechanical stability properties for PDA/PCBAA co-deposited coating were comprehensively investigated. These interesting properties make the coatings promising candidates for numerous applications.

Performance of SiO2 Filled Functional Polypropylene Substrates for 5th Generation Communication

Abstract: Abstract Three grades of functional polypropylene (FPP)/silica (SiO2) (FPPASP16 xSiO2 y, FPPASP17 xSiO2 y and FPPASP18 xSiO2 y) and their crosslinked FPP/SiO2 (CLFPPASP16 xSiO2 y, CLFPPASP17 xSiO2 y and CLFPPASP18 xSiO2 y) nanocomposites were satisfactorily made for applying as fifth generation (5 G) mobile communication substrates. Significantly smaller linear thermal expansion coefficient (LCTE) but larger dielectric constant (εr), dielectric loss (tan δ) and onset degradation temperature (DTonset) were acquired for CLFPPa xSiO2 y than those of the corresponding FPPa xSiO2 y sequence having identical SiO2 loadings. It is worth emphasizing that substantially smaller εr, tan δ and LCTE values were acquired for every FPPa xSiO2 y and CLFPPa xSiO2 y sequence filled with appropriate SiO2 loadings. Quite small εr/tan δ ( 2.41/0.00539, 2.36/0.00361, 2.53/0.00653, 2.52/0.00671, 2.46/0.00461 and 2.62/0.00821, all measured at 1 MHz) and LCTE (∼140 ppm/°C, 152 ppm/°C, 75 ppm/°C, 127 ppm/°C, 142 ppm/°C and 56 ppm/°C) values suitable for 5 G communication were acquired for FPPASP16 95SiO2 5, FPPASP17 94SiO2 6, FPPASP18 95SiO2 5, CLFPPASP16 95SiO2 5, CLFPPASP17 94SiO2 6 and CLFPPASP18 95SiO2 5 filled with optimum loadings of SiO2 nanoparticles, respectively. All free volume properties estimated for every FPPa xSiO2 y and CLFPPa xSiO2 y sequence enlarged to a largest value as the SiO2 loadings approached the corresponding optimum value. Possible reasons accounting for these substantially diminished dielectric and LCTE and improved thermal degradation properties of the FPPa xSiO2 y and CLFPPa xSiO2 y films are proposed.

Effect of Phenolic Resin and Nano-Calcium Carbonate Particles on the Curing Kinetic of Epoxy Composites

Abstract: Abstract The research described here studied the curing kinetics of pure epoxy (EP), epoxy/phenolic resin (EP/PH) and epoxy/nano-CaCO3 particles (EP/NPs) composites by isothermal differential scanning calorimetry (DSC). A model free technique (isoconversional technique) was used to study the curing reaction kinetics and the results showed that the activation energies (Ea) of the pure EP, EP/PH, and EP/NPs composites remained constant at different conversions. The research showed a decrease of Ea for the EP/NPs system, while there was a small increase of Ea for the EP/PH. This can be attributed to the acceleration effect of the nano-CaCO3 for the EP/NPs system and the low reactivity of PH for the EP/PH system.

Study on Preparation and Performance of Reactive Polyurethane Hot Melt Adhesives Based on a Polycarbonate Diol and a Polyester Diol

Abstract: Abstract Reactive polyurethane hot melt adhesives (HMPURs) containing a mixture of poly 1,3-propylene sebacate diols (PPSe) and poly 1,6-hexanediol carbonate diols (PHC) as soft segments were prepared to investigate the influence of the relative content of PHC and PPSe on the properties of the HMPURs. The results showed that the HMPURs had excellent thermal stability below 250 °C; when the temperature was above 250 °C but below 360 °C, the HMPURs prepared from PPSe or PHC had better thermal stability than the HMPURs prepared from the mixture. With the increase of PHC content, the melting viscosity and elongation at break (δ) of the HMPURs decreased, while the open time and bond strength of the adhesive on PC substrates increased. When the polycarbonate diol content in the soft segments was higher than 50%, the HMPURs had better hydrolysis resistance than when it was lower.

Comparative Study of the Structural, Mechanical and Electrochemical Properties of Polyacrylonitrile (PAN)-Based Polypyrrole (PPy) and Polyvinylidene Fluoride (PVDF) Electrospun Nanofibers

Abstract: Abstract In this study, polyacrylonitrile (PAN)-based polypyrrole (PPy) and polyvinylidene fluoride (PVDF) nanofibers (PAN/PPy, PAN/PVDF and PAN/PPy/PVDF) were produced by an electrospinning method and their mechanical and electrochemical properties were compared, resulting in obtaining a composite material that had high mechanical strength and electrical conductivity at the same time. The morphological, structural, mechanical and electrochemical performance of the nanofibers were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) surface area measurements, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicated that beadless and smooth nanofiber formation was achieved for all of the PAN/PPy, PAN/PPy/PVDF and PAN/PVDF combinations. PAN/PPy/PVDF, containing 80 wt% PAN 10 wt% PPy and 10 wt% PVDF, had the highest BET surface area and the smallest pore size. In terms of mechanical properties, PAN/PPy/PVDF nanofibers (80 wt% PAN, 10 wt% PPy, 10 wt% PVDF) also showed the highest Young Modulus, 36.82 MPa, while that of the PAN/PPy nanofibers was the lowest. Therefore, in terms of physical and mechanical properties, the PAN/PPy/PVDF combination was favored. However, in terms of the electrochemical properties, CV and EIS data showed that the PAN/PPy nanofibers had the highest electrical conductivity among the PAN-based nanofibers.

Comparative Study of the Structural, Mechanical and Electrochemical Properties of Polyacrylonitrile (PAN)-Based Polypyrrole (PPy) and Polyvinylidene fluoride (PVDF) Electrospun Nanofibers

Abstract: In this study, polyacrylonitrile (PAN)-based polypyrrole (PPy) and polyvinylidene fluoride (PVDF) nanofibers (PAN/PPy, PAN/PVDF and PAN/PPy/PVDF) were produced by an electrospinning method and their mechanical and electrochemical properties were compared, resulting in obtaining a composite material that had high mechanical strength and electrical conductivity at the same time. The morphological, structural, mechanical and electrochemical performance of the nanofibers were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) surface area measurements, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicated that beadless and smooth nanofiber formation was achieved for all of the PAN/PPy, PAN/PPy/PVDF and PAN/PVDF combinations. PAN/PPy/PVDF, containing 80 wt% PAN 10 wt% PPy and 10 wt% PVDF, had the highest BET surface area and the smallest pore size. In terms of mechanical properties, PAN/PPy/PVDF nanofibers (80 wt% PAN, 10 wt% PPy, 10 wt% PVDF) also showed the highest Young Modulus, 36.82 MPa, while that of the PAN/PPy nanofibers was the lowest. Therefore, in terms of physical and mechanical properties, the PAN/PPy/PVDF combination was favored. However, in terms of the electrochemical properties, CV and EIS data showed that the PAN/PPy nanofibers had the highest electrical conductivity among the PAN-based nanofibers.