Volume 44, Issue 3

The rheological characterization of STFs plays an essential role in understanding the suspension’s stability and the structural changes that occur under the impact of shear forces. This study aims to investigate the rheological behavior of STF after adding titanium diboride (TiB 2 ) as an additive. STF modified with 2 % w/W TiB 2 compared to other concentrations (1 %, 1.25 %, and 3 %) showed a maximum rise in viscosity (max), i.e., 18,484 Pa s during steady state rheology, as compared to untreated STF. In dynamic rheology, the same sample demonstrated maximum values of G′ and G ″ at a constant frequency of 30 rad/s, G ′ and G ″ improved by 25 and 11 times, respectively, over unmodified STF. Furthermore, for constant strain amplitudes, the maximum values of G ′ and G ″ were observed at a strain amplitude of 700 %. G ′ and G ″ improved by approximately 6.5 and 6 times over unmodified STF, respectively. The findings of the dynamic and steady-state rheological analyses demonstrated that integrating TiB 2 into the STF improved the ST behavior.

In order to study the effect of nanoparticle dimensions on the thermodynamic properties of PHBV and PHBV blends, one-dimensional cellulose nanocrystals (CNC), two-dimensional graphene, and zero-dimensional hydrophobic nano-silica were selected to regulate the crystallization and mechanical properties of poly( β -hydroxybutyrate- co -valerate) (PHBV) and PHBV blends. The morphology, crystallization process, mechanical property and rheological response of PHBV nanomaterials were analyzed. Experimental results show that the three selected nanomaterials all hinder the crystallization process of PHBV, among which two-dimensional graphene exhibits the most obvious hindrance. At the same time, two-dimensional graphene can improve the tensile strength and impact strength of PHBV. However, in the rheological response of PHBV nanocomposites, zero-dimensional hydrophobic nano-silica and one-dimensional cellulose nanocrystals show more obvious regulatory effects than two-dimensional graphene.

The process of wound healing is complex and dynamic. Given the unique nature of the skin, wound healing requires dressings that meet a wide range of functional requirements. Due to their unique structure and properties, hydrogel dressings provide ideal conditions for supporting the process of wound healing and can be enhanced with additional functions to meet the specific requirements of different types of wounds. Compared to traditional wound dressings, the newly developed hydrogel wound dressing offers several advantages, including its soft texture, ability to retain moisture, oxygen permeability, and comfort. With the advancement of medical technology, higher demands are being placed on the functionality of hydrogel dressings. Therefore, this paper offers a comprehensive overview of hydrogel wound dressings with various functions. These functions primarily include hemostatic hydrogel dressings, antibacterial hydrogel dressings, angiogenesis-promoting hydrogel dressings, and other functional hydrogel dressings. The paper also reviews the research and application of these dressings in recent years.

Synthetic polymeric hydrogel is a potential substitute for soft biological tissues. However, the poor mechanical properties of traditional synthetic hydrogels limit their applications in biological fields. Herein, a series of tough physical hydrogels have been prepared by micellar polymerization, in the existence of sodium bromide (NaBr), using methacrylic acid (MA) and stearyl acrylate (SA) as monomers, cetyltrimethyl ammonium bromide (CTAB) as cationic surfactant. The hydrogels exhibit excellent mechanical properties: modulus, toughness, and tearing fracture energy up to 7.8 MPa, 34 MJ m −3 , and 16,600 J m −2 , respectively. Moreover, it was found that the toughness of the hydrogels can be modulated in a very wide range by different post-treatments, e.g., dried/reswelling, freezing/thawing, or heated treatments. After post-treatments, the elastic physical hydrogels even turn into brittle plastics: modulus and toughness vary by 3 and 4 orders of magnitude, respectively. The mechanism for this wide tunability is attributed to the change of electrostatic attraction, crystallization, and phase separation during post-treatments.

Composite films of polytetrafluoroethylene (PTFE) and polyimide (PI) combine the advantages of both materials like excellent inertness to chemicals and thermal stability, which provide great potential in applications under harsh environments. However, strong adhesion between PTFE and PI layers still remains a big challenge. In this study, fluorinated ethylene propylene (FEP) as an intermediate layer was found to significantly enhance the adhesion of PTFE films to PI film, with peel strength up to 350 N/m in the manufactured direction comparing to the value of 0 for PTFE/PI composite film without FEP. It’s superior to that of commercially available products (25 N/m) under the same test conditions. The improved performance is attributed to the formation of interlocks of molecules at the interfaces between the PTFE and FEP layers, and FEP and PI layers as observed in the images obtained by atomic force microscope (AFM) and scanning electron microscopy (SEM).

Recently, the fabrication of a scaffold from biomaterials has been increased due to the lack of adequate natural bone for grafting. In this study, hydroxyapatite-chitosan-alginate-polyamide (HCAP) synthetic scaffold was fabricated using the thermally induced phase separation (TIPS) technique. The scaffold was cross-linked with either a chemical cross-linker (calcium chloride, 2-hydroxyethyl methacrylate (HEMA), or glutaraldehyde (GTA)) or a physical cross-linker (gamma irradiation (IR)) resulting in scaffolds HCAP-CaCl 2 , HCAP-HEMA, HCAP-GTA, and HCAP-IR, respectively. The cross-linked scaffolds were characterized based on physicochemical properties, cytotoxicity, and biocompatibility. HCAP-GTA showed the highest density and the lowest swelling ratio and biodegradation rate closely matching with those of the HCAP-IR. Porosity and density of the HCAP, HCAP-IR, and HCAP-GTA scaffolds were 92.14, 87.26, and 83.33 %, and 0.241, 0.307, and 0.335 g/cm 3 , respectively. The swelling ratio for the same scaffolds was 149, 110, and 108 % after 72 h of observation. Brine shrimp cytotoxicity and RBC biocompatibility assay confirmed the non-toxic nature of HCAP-IR and HCAP-GTA scaffolds. The HCAP-IR scaffold was tested for bone regeneration in the rabbit mandible defect model. Histological analysis revealed the regeneration of new bone and restoration of bone defect at the site of injury. These findings indicate that radiation induced physically cross-linked HCAP scaffold could be used as an alternative in bone defect replacement therapy.

The interleaved fiber-reinforced polymer composites (FRPs) by carbon nanotubes (CNTs)/thermoplastic polyetherketone-cardo (PEK-C) hybrid interleaves show the potential of comprehensively improving the mechanical properties of composites and have been hotspot. However, the synergistic effect and mechanism of CNTs and TP resin have not been attained. The interlaminar region of interleaved composites is too narrow and complex to be fully analyzed. Therefore, the layered resin structure composed of an interlayer and a matrix (epoxy) layer was prepared to model the interlaminar region in this study. The evolution of gradient structure developed by the layered structure in curing and the influence of presence of CNTs in interlayer were investigated based on morphology characterization. The results showed that epoxy resin gradually diffused into the interlayer, resulting in the concentration gradient and the resultant gradient phase structure. The presence of CNTs in hybrid interlayer hindered the resin diffusion and consequently hindered the formation of dual-phase structure, which was not conducive to the toughness improvement. The inappropriate high temperature was not recommended due to the effect of facilitating diffusion, probably resulting in the formation of excrescent epoxy layer in the interlaminar region and undesired mechanical performance. This study conducted experiments on resin system to simplify the interesting subject and the results will help to develop the synergistic mechanism of TP resin and nanoparticles.

An innovative reactor concept is reported that allows for efficient mass transfer from the liquid phase to the base material and compensates for the growth of the material throughout the synthesis of polymer electrolyte membranes (PEM). The novel reactor allows for the synthesis of PEMs with high reproducibility of their dimensions and properties. PEMs are synthesized via graft copolymerization of the monomers acrylic acid and 2-acrylamido-2-methylpropane sulfonic acid on poly(vinylidene fluoride) films serving as base material, which was activated by electron beam treatment. Both monomers are already containing protogenic groups; thus, follow-up functionalization reactions are avoided. The PEMs were characterized with respect to their electrochemical properties (area specific resistance, recharge current, and ion exchange capacity) relevant for application in vanadium flow batteries and compared to commercially available PEMs.