Volume 40, Issue 2

Epoxy composites with different weight percentages of calcium carbonate and calcium phosphate were synthesized as bone tissue substitutes (BTS) for internal dosimetry. The Fourier-transform infrared spectroscopy analysis confirmed that no chemical reaction occurred between the polymer and the fillers. Thermogravimetric analysis also showed improvement in the thermal properties of the composites due to the fillers. The uniform distribution of fillers in the epoxy matrix was established by X-ray radiography. The attenuation behavior of BTS was probed for low energy γ source 241 Am (59.5 keV) using planar HPGe detector. The measured mass attenuation coefficients of BTS were found to match with the values calculated using XCOM software. The radiological properties derived for these composites were found to be on par with those of ICRU-44 cortical bone and B-100 bone equivalent plastic.

In this study, polyurethane (PU) scaffolds were fabricated by electrospinning technology and modified through the deposition of polydopamine (PDA) on the activated surface under oxygen plasma treatment. Herein, the effect of the modification process on the homogeneous surface coating and the changes in the physicochemical and biological properties were evaluated. Morphological observations demonstrated decoration of the nanofibrous microstructure with PDA, while the uniformity and homogeneity of the deposited layer increased after plasma oxygen treatment. Hydrophilicity measurements and swelling ratio indicated a remarkable improvement in the interaction of scaffolds with water molecules when the PDA coating is applied on the surface of the treated nanofibers. The biomineralization of the samples was characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) images. It was found that PDA has the capability for mineralization, and the amount of deposited hydroxyapatite increased as a function of PDA content. The in vitro evaluation of constructs indicated great improvement in cell-scaffold interactions, biocompatibility, and alkaline phosphatase activity after coating the PDA on the plasma-modified matrix. These results suggest that PDA coating, especially after oxygen plasma treatment, improves the physicochemical and in vitro properties of PU scaffolds for bone tissue engineering application.

Recent research has proven that starch offers a wide range of industrial, commercial, and utility applications if they are optimally processed and refined. In this study, the effect of hydrogen peroxide (HP), sodium persulfite, peracetic acid (PAA), and sodium perborate (SPB) bleaching agents on the physiochemical, surface, mechanical, and flow properties were investigated. The various bleached starch bioplastics were characterized using Fourier transform infrared, scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis. Hydroxyl and carbonyl (C=O) stretching were seen for HP- and PAA-bleached starch bioplastics at 3285 and 1736 and 3265 and 1698 cm −1 , respectively. The C=O band was absent for SPB-treated starch, whereas the C=S band was seen on sodium hyposulfite (SHS)-treated starch. The morphologies of starch were retained with little agglomerations, except for HP-treated starch bioplastics with a morphology change. HP-treated starch had the highest percentage crystallinity (66%) and the highest thermal stability (74% weight loss), whereas PAA-treated starch had the lowest percentage crystallinity (34%) and the lowest thermal stability (88% weight loss). HP- and SHS-bleached starch bioplastics had the best surface, mechanical, and expansion properties.

Polyethylene terephthalate (PET) fiber samples were irradiated using different gamma radiation doses. The physicochemical and structural properties of the irradiated PET samples, either the pristine sample or the sample chemically modified with polyethylene glycol (PEG), were assessed using X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. The surface morphology and characteristics of the irradiated PET fiber samples were investigated using scanning electron microscopy (SEM). The pristine and PEG-modified PET fibers were exposed to gamma radiation with doses ranging from 0.5 to 20 kGy. The FTIR analysis results showed certain degradation via irradiation, deduced from a decrease in the intensities of most of the PET original infrared bands. The XRD and DSC analysis results indicated the reduction of crystallinity upon irradiation of pristine and modified PET fibers. Conversely, an improvement in the crystallinity was observed at high doses compared with low doses. The crystallinity of the PEG-modified PET was found to be improved. Two types of morphological changes, wrinkles and small particles, were observed on the PET fiber surface due to gamma irradiation.

The stereocomplex formation is a promising method to improve the properties of poly(lactide) (PLA)-based products due to the strong interaction of the side-by-side arrangement of the molecular chains. Recently, electrospinning method has been applied to prepare PLA stereocomplex, which is more convenient. The objective of the current study is to make stereocomplexed PLA nanofibers using electrospinning method and compare their properties and structures with pure poly(l-lactide) (PLLA) fibers. The stereocomplexed fibers were electrospun from a blend solution of high molecular weight PLLA and poly(d-lactide) (1:1 ratio). The morphology of the obtained electrospun fibers was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Differential scanning calorimetry was applied to study their thermal properties and crystallinity. Fourier transform infrared spectroscopy (FTIR) test was conducted on the samples to characterize their chemical properties. The SEM and AFM images indicated that smooth uniform fibers with a cylindrical structure were produced. Besides, the FTIR results and thermal properties confirmed that only stereocomplex crystallites formed in the resulting fibers via the electrospinning method.

In this work, a skin-core structure was designed, and three kinds of dual-wavelength fluorescent anti-counterfeiting (DWFA) fibers, including UV short-wavelength/UV long-wavelength, infrared/UV short-wavelength, and infrared/UV long-wavelength excitable DWFA fibers with skin-core structure, were spun using fluorescent powder/PP pellets as the skin material and pure PP as the core material. The results showed that these DWFA fibers emitted two different colors of light under excitation of two different wavelength lights, which exhibited higher anti-counterfeiting safety. Take UV short-wavelength/UV long-wavelength DWFA fibers, for example; the influence of skin-core ratio on the structure and properties of fibers were investigated, and then the luminous efficiency of DWFA fibers with skin-core structure and homogenous structure was compared. The microscope photos and 3D simulation of fluorescent powder in fibers by confocal laser scanning microscope showed that the fluorescent powders were basically distributed in the skin layer of fibers. The crystallinity degree and tensile strength of DWFA fibers with skin-core structure decreased first and then increased with the decrease in skin-core ratio, whereas elongation of fibers showed an increasing trend. Compared with homogenous DWFA fibers, the skin-core DWFA fibers exhibited higher luminous efficiency under the same fluorescent powder content.

Recently, due to sustainable development and environmental protection policies, there is increasing interest in the development of new biodegradable polymer-based multifunctional composites. Chitosan is one of the most remarkable and preferred biopolymers, which is environmentally friendly as well as renewable, biocompatible, and inexpensive. Though it has a wide range of potential applications, the major limitation of chitosan – the problem of poor mechanical performance – needs to be solved. In this work, graphene oxide was first produced and then used to manufacture a chitosan/graphene oxide/zinc oxide composite film through a casting method. The properties of the chitosan film and the chitosan/graphene oxide/zinc oxide composite film were investigated using Fourier transform infrared spectroscopy, mechanical, thermal gravimetric, and ultraviolet (UV)-visible spectroscopy analyses. The results showed that the incorporation of graphene oxide and zinc oxide into the chitosan matrix resulted in enhanced mechanical properties and thermal stability of chitosan biocomposite films. The graphene oxide- and zinc oxide-reinforced chitosan film showed 2527 MPa and 55.72 MPa of Young’s modulus and tensile strength, respectively, while neat chitosan showed only 1549 MPa and 37.91 MPa of Young’s modulus and tensile strength, respectively. Conversely, the addition of graphene oxide decreased the transmittance, notably in the UV region.

Into purified organic wastewater, α-, β-, and γ-cyclodextrin (α-, β-, and γ-CD) were added to polyvinyl alcohol (PVA) with ammonium persulfate as the crosslinker. The CD/PVA composite film with low water solubility and supramolecular adsorption was prepared by solvent evaporation. Fourier transform infrared spectroscopy showed that when CD was successfully added to PVA, the crosslinking process had no effect on -OH, and the structure was stable after soaking in water for 120 h. Solubility experiments showed that the stability of PVA in water was significantly improved. The results of phenolphthalein adsorption showed that the composite film followed the Langmuir isothermal adsorption and the pseudo-second-order kinetics. According to the Langmuir equation, the theoretical maximum adsorption capacities of α-, β- and γ-CD/PVA composite films were 0.41, 2.05, and 2.00 mg/g, respectively. The parameters of the Freundlich equation indicate that the adsorption of the composite film is physical adsorption. The time for α-CD/PVA composite film to reach equilibrium was the shortest, while the longest was for β-CD/PVA composite film. The intraparticle diffusion model showed that the adsorption was mainly affected by the diffusion of the boundary layer, and the diffusion rate limitation of the boundary layer of the high-concentration phenolphthalein solution was more obvious.

Glass fiber composites are prevalent molded materials used in various fields, including aviation engineering, automobile manufacturing, and medical equipment production. The length of a glass fiber affects the mechanical properties of a glass fiber composite. Studies have reported that breakage occurs in long fibers subjected to screw plasticization, injection processes, and geometrical changes in injection molding. Moreover, multigate injection molding can result in weldlines on the final product, consequently reducing its strength. Further exploration is required to determine how product strength is affected by weldlines generated through injection molding with glass fiber composites and how product tensile properties associated with weldlines can be improved. Therefore, this study designed a mold with a vent area and a plug-in mold-surface-heating device to examine changes in the weldlines and tensile properties of long-glass-fiber composite specimens fabricated through injection molding using two melts. The results revealed that fiber length decreased with increasing screw speed; such declines in fiber length affected the tensile strength of the long-glass-fiber-reinforced polyamide-66 composites. In addition, because the arrangement and distribution of the glass fibers were affected by the melt flow rate, melt flow direction, and changes in mold cavity volume, the weldline tensile strength varied with the depth of the vent area. Mold surface heating improved the specimen surface roughness by 5.79% and effectively improved the interfacial adhesion between the fibers and melts, thereby resulting in more favorable weldline tensile strength. This also notably reduced the depth of weldlines produced by the adhesion of two melts.

In this research, the photocatalytic degradation performance in a commercial low-density polyethylene (LDPE) film was investigated in the presence of zinc oxide (ZnO) nanoparticles grafted with two amounts of polyacrylamide. Fourier-transform infrared spectroscopy (FTIR) besides thermogravimetric analysis (TGA) test results reinforced the successful grafting of polyacrylamide to the extent of 10 and 39 wt.% on the ZnO nanoparticles. The photocatalytic degradation of the films under ultraviolet (UV) radiation was evaluated by characterizing the mechanical properties, weight loss, and morphology. The UV absorption and emission for ZnO nanoparticles were increased after grafting with 10% polyacrylamide. The tensile strength of the nanocomposite films increased with the incorporation of nanoparticles. The presence of ZnO nanoparticles in LDPE films increased the rate of degradation after 200 h of irradiation. The polyacrylamide grafting improved the dispersion of ZnO particles in LDPE matrix, whereas the increase of grafting extent from 10 to 39 wt.% reduced the photocatalytic performance of ZnO nanoparticles.