Polymer Science, Series B最新文献

Ethyl acrylate and butyl acrylate were used as monomers, vinyl monochloride acetate was used as the crosslinker in vulcanization reactions and sodium dodecyl sulfate was used as the emulsifier to prepare a general-purpose acrylic rubber. The synthetic products were characterized by infrared spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, and other methods. Then, the raw rubber, carbon black, vulcanizing agent, and so forth were mixed and then vulcanized, and the performance of the product was tested. The results showed that the synthesized acrylic rubber contained low levels of ash and volatile matter. The structure of the acrylic rubber was consistent with its design, and the glass transition temperature was –28.1°C. A study showed that the product vulcanized quickly. When the dosage of butyl acrylate was increased, the tensile strength decreased, and the elongation at break increased. The working temperature was reduced by adding plasticizer. With increasing plasticizer (RS-735) content, the elongation at break increased, and the tensile strength decreased. When the RS-735 level reached 10 phr, the brittleness temperature of the product decreased to –28°C. This product is resistant to oil and high temperatures, and it can be used widely in environments from –28 to 180°C.

Carbon nanotubes (CNTs)/polyamide-6 (PA6) nanocomposites with different CNTs loadings have been prepared by in situ polymerization approach. Then the blends were extruded into fibers using melt spinning technology to prepare as-spun and drawn fibers. Scanning electron microscopy observation on the fracture surfaces of the composite’s fiber shows not only a uniform dispersion of CNTs but also a strong interfacial adhesion with the matrix. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results show that CNTs act as strong heterogeneous nucleating agents for PA6 crystals. The breaking strength of drawn composite fibers, with incorporating less than 4 wt % CNTs, is slightly higher than that of pure PA fibers prepared at the same draw ratio. The PA6/CNTs composite fibers reveal a high increase in breaking strength as the draw ratio increased. Due to the electric conductivity of CNTs, electrical resistivity of the PA6/CNTs composite fibers is reduced.

Inspired by mussel heuristic chemistry, a novel method for improving surface wettability and adhesion of carbon fibers with epoxy resins was proposed by codepositing gallic acid and polyethylene imine on the carbon fiber surfaces in a convenient operation. The results of scanning electron microscopy, infrared, Raman and X-ray photoelectron spectra revealed that gallic acid and polyethylene imine could undergo Michael addition or Schiff base reaction and codeposit on the carbon fiber surfaces successfully. The gallic acid-polyethylene imine codeposited carbon fibers were used to fabricate epoxy matrix composites. The results of mechanical tests showed that interlaminar shear strength, flexural modulus and strength of the gallic acid-polyethylene imine codeposited carbon fiber composite were increased by 27, 38, and 27% respectively, compared with those of the untreated carbon fiber composite. The conclusion can be drawn that the gallic acid-polyethylene imine codeposition is an effective method for improving interfacial properties of carbon fiber reinforced epoxy resin matrix composites.

The possibility of using organomineral complexes of polyhexamethylene guanidine hydrochloride as a functional additive for a waterborne paint based on polyvinyl acetate has been investigated. Organomineral complexes containing 20 and 30 wt % guanidine polymer have been obtained, with intercalation of polyguanidine chains into the interlayer space of montmorillonite being observed. It has been revealed that the stability of the polymer film to water is retained when organomineral complexes are introduced into a polyvinyl acetate dispersion, whereas the water resistance of the film sharply decreases when free polyguanidine is added. There was no significant influence of organomineral complexes on the rheological characteristics of the dispersion and its sedimentation stability. Testing of waterborne paints with various additives has shown that introduction of organomineral complexes into the material prevents the coating from fouling by biofilms of gram-positive bacteria Staphylococcus aureus and Rhodococcus erythropolis, with the hardness, water resistance, and water-vapor transmission of the coatings being retained at a satisfactory level.

Articular cartilage (AC) defects may be caused by injury or osteochondral pathology, which is a major risk factor for catastrophic degenerative arthritis. Currently, AC defects are a serious concern for patients because clinical treatments are not satisfactory. Owing to the limited self-healing ability of AC, the proliferation and chondrogenesis of seed cells are necessary for cartilage tissue regeneration. To treat AC defects, growth factors are required to regulate the behavior of seed cells for optimal therapeutic effects. Considering these issues, injectable hydrogels are suitable for both the repair and regeneration of AC because of their unique structural and functional features. After literature search and analysis, we introduced several gelation methods for injectable hydrogels. We then highlighted the biomedical applications of injectable hydrogels in the field of AC tissue engineering, with an emphasis on composite hydrogels, cell therapy, and carrier delivery. Finally, the achievements and challenges of injectable hydrogels for AC repair and regeneration were discussed based on previous studies. The summarized developments help to understand injectable hydrogels in the field of cartilage tissue engineering.

In this study, the hydrothermal method was used to synthesize the rare earth catalyst ethylene glycol cerium (EG-Ce), and its catalytical performance on polyethylene glycol terephthalate (PET) and low-melting polyethylene glycol terephthalate (LmPET) were investigated. Using the rare earth catalyst EG-Ce, cerium-catalytic polyester (PET-Ce), and cerium-catalytic low-melting point polyester (LmPET-Ce) were effectively synthesized. The differences in melting point, inherent viscosity, thermal stability, and other parameters of the PET produced by the EG-Ce and traditional ethylene glycol antimony (EG-Sb) were compared. The outcomes demonstrate that the rare earth catalyst EG-Ce had superior catalytic activity than EG‑Sb in the polymerization process. The LmPET produced by EG-Ce also exhibited excellent mechanical properties and adhesive quality than the items which produced by EG-Sb. The rare earth-based catalyst reduced the safety risk than heavy metal antimony, indicating that is a good candidate as a catalyst in polyester and low-melting polyester synthesis.

Solvent-free polyurethane acrylate (PUA) by UV-cured process generally has low molecular weight, and thus shows weak mechanical properties, which limited its application. Herein, five kinds of linear polyetheramine modified polyurethane acrylates (PUPEA) were prepared using polyetheramine (PEA) instead of partial acrylic monomers as capping agents at the end of the polyurethane to improve the resilience and elongation. Structures of PUPEA were characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (¹H NMR). Mechanical properties, hydrophobicity and thermodynamic properties of the obtained PUPEA were investigated and compared with those of conventional PUA. The results show that the semi-capping polyurethane with PEA instead of HEA can significantly improve the resilience and flexibility, specially, the flexibility increases about thrice to fourfold higher than those of PUA. Moreover, PUPEAs provide the self-healing properties and self-adhesive properties, while the conventional PUA does not have. Therefore, the introduction of PEA can effectively regulate the properties of PUA, which expands the application of UV-curable polyurethane elastomers in flexible electronic sensors.

Using the polymerization filling technique, composite materials have been obtained based on ultra-high molecular weight PE and fillers of platelike (graphene or graphite nanoplatelets) and spherical (silica) types. The tensile stress–strain characteristics of samples obtained using different pressing modes have been examined. It has been revealed that the cooling rate of the samples during pressing affects the values of ultimate tensile strength and modulus of elasticity in tension. The characteristics of composites processed at a low cooling rate (10 K/h) are 30% higher than those of the samples obtained at a high cooling rate (10 K/min). Using DSC, DMA, and X-ray diffraction methods, it has been shown that the way of cooling affects the crystallite size of compressed samples of composite materials.

The chemical oxidative polymerization (COP) method was used in the lab to create the nanocomposite materials polypyrrole (PPY), reduced graphene oxide (rGO), polypyrrole-copper oxide (PPY-CuO), and polypyrrole-copper oxide-graphene oxide (PPY-CuO-GO). It was discovered by analysis of the X-Ray diffraction (XRD) results that CuO was successfully absorbed into the surface of PPY with an average crystallite size of 38 nm. The aggregation in the PPY polymer chain was accelerated by the anisotropic behavior of CuO. The conductivity of the PPY-CuO-GO nanocomposite was considerably improved, and the current density was enriched. When compared to the original PPY, the PPY-CuO-rGO nanocomposite was shown to have an improved current density of 49.20 A/cm² and reduced band gap 1.92 eV. The PPY-CuO-rGO nanocomposite can be employed as an electron transporting layer (ETL) material for organic light emitting diodes (OLED) application due to the increased current density and high electron-hole recombination rate.

The operating conditions of products made of polymeric materials significantly affect their service life. Herein we have investigated the influence of duration of natural climatic factors of the Republic of Sakha (Yakutia) (very cold climate zone) impact on the structure and properties of polyethylene grade 273-83. IR spectroscopic studies have shown that radical oxidative reactions causing a decrease in the polymer molecular weight occur in the material during long-term natural exposure. Investigation of the melt flow index has shown that, besides the reactions accompanied by rupture of the macromolecular chains, crosslinking processes also occur in the polymer. These processes lead to a decrease in the polymer molecular weight and broadening of the molecular weight distribution. It has been shown that the change in the degree of crystallinity and the lamellas thickness is non-monotonic and is determined by the weather conditions during the exposure period. Changes in the intensity of solar radiation, as well as average daily and seasonal temperatures of the ambient air, together with chemical changes occurring in the polymer during natural exposure, lead to the appearance of areas of ordered structures in the amorphous phase, resulting in the decrease in thickness of the amorphous phase which determines the material plasticity. Therefore, the stresses in the macromolecular chains of the polymer in the amorphous phase are so much increased that the polymer exhibits the behavior of a brittle material.