Electrospun Semi-Alicyclic Polyimide Nanofibrous Membrane: High-Reflectance and High-Whiteness with Superior Thermal and Ultraviolet Radiation Stability for Potential Applications in High-Power UV-LEDs

Polymeric nanofibrous membranes (NFMs) with both high whiteness and high thermal and ultraviolet (UV) stability are highly desired as reflectors for ultraviolet light-emitting diodes (UV-LEDs) devices. In the current work, a semi-alicyclic and fluoro-containing polyimide (PI) NFM with potential application in such kinds of circumstances was successfully fabricated from the organo-soluble PI resin solution via a one-step electrospinning procedure. In order to achieve the target, a semi-alicyclic PI resin was first designed and synthesized from an alicyclic dianhydride, 3,4-dicarboxy-1,2,3,4,5,6,7,8-decahydro-1-naphthalenesuccinic dianhydride (or hydrogenated tetralin dianhydride, HTDA), and a fluoro-containing diamine, 2,2-bis[4-(4-amino-phenoxy)phenyl]hexafluoropropane (BDAF), via an imidization procedure. The derived PI (HTDA-BDAF) resin possessed a number-average molecular weight (Mn) higher than 33,000 g/mol and was highly soluble in polar aprotic solvents, such as N,N-dimethylacetamide (DMAc). The electrospinning solution was prepared by dissolving the PI resin in DMAc at a solid content of 25–35 wt%. For comparison, the conventional high-whiteness polystyrene (PS) NFM was prepared according to a similar electrospinning procedure. The thermal and UV stability of the derived PI and PS NFMs were investigated by exposure under the UV-LED (wavelength: 365 nm) irradiation. Various thermal evaluation results indicated that the developed PI (HTDA-BDAF) NFM could maintain both the high reflectance and high whiteness at elevated temperatures. For example, after thermal treatment at 200 °C for 1 h in air, the PI (HTDA-BDAF) NFM exhibited a reflectance at a wavelength of 457 nm (R457) of 89.0%, which was comparable to that of the pristine PI NMF (R457 = 90.2%). The PI (HTDA-BDAF) NFM exhibited a whiteness index (WI) of 90.88, which was also close to that of the pristine sample (WI = 91.22). However, for the PS NFM counterpart, the R457 value decreased from the pristine 88.4% to 18.1% after thermal treatment at 150 °C for 1 h, and the sample became transparent. The PI NFM maintained good optical and mechanical properties during the high dose (2670 J/cm2) of UV exposure, while the properties of the PS NFM apparently deteriorated under the same UV aging.

Optimization of Materials Composition and UV-VIS Light Wavelength Towards Curing Time Performance on Development of Tissue Engineering Scaffold

VAT photopolymerization 3D printing is a process that solidified a vat of liquid photopolymer resin solution into desired products in the presence of UV light. Achieving an optimal property with shorter curing time is an ultimate goal when using functional or special resins. In this study, the effect of wavelength with different compositions of UHT resin mixed PEG solution is studied. Different sources of light were identified, which is UV-A with a wavelength of 365 nm and VIS with a wavelength greater than 420 nm. The PEGconcentrations were varied at 40%, 50%, and 60%. While UHT concentration ratio added into solution was 30%, 50%, and 70%. It has been observed that the optimum curing under UV and VIS wavelength were 9.55 minutes and 17.48 minutes respectively. The feasible range to optimize results of curing time, PEG 48%and UHT 41% with the result 8.6 minutes for the UV-A. Meanwhile, for VISwavelength, PEG 49% and UHT 64% with the result 16 minutes. The success of this study will lead to further innovation on UV-VIS light source in 3D printing in terms of energy efficiency, safety, and cost as well as further evaluation of the performance with respect to the mechanical properties of tissue engineering scaffold.

The Antibacterial Properties and Safety of a Nanoparticle-Coated Parquet Floor

Floor antibacterial technology prevents the human body from cross-infection with bacterial diseases. The most commonly used approach to endow daily-used floors with antibacterial properties is to apply a thin film of antibacterial agents on the parquet floor surface. In the present study, five commercial antibacterial nanoparticles were first dispersed in melamine resin solution, and then applied on a floor. Afterwards, the antibacterial properties of the nanoparticle-coated floor were investigated, in which Escherichia coli was used as the target bacteria. The impact of the nanoparticle dispersing agents on the ultimate antibacterial properties of the floor were also investigated. The results showed that silver nanoparticle-loaded hydroxyl zirconium sodium phosphate (Ag-HZDP) was most suitable as the antibacterial agent of a melamine coating for parquet flooring. With the help of sodium hexametaphosphate, the antibacterial agent was able to disperse well in the melamine resin solution and was also able to disperse well on the floor surface. When the loading amount of Ag-HZDP was 1 wt % or higher, the prepared antibacterial floor was able kill almost all the bacteria cultivated on its surface. Moreover, the prepared antibacterial floor had a lower toxicity compared with a pristine cedar substrate. The present study provides an effective way to provide daily-used parquet floors with excellent antibacterial properties.

Fabrication of Conducting Polyacrylate Resin Solution with Polyaniline Nanofiber and Graphene for Conductive 3D Printing Application

Three-dimensional printing based on the digital light processing (DLP) method offers solution processability, fast printing time, and high-quality printing through selective light curing of photopolymers. This research relates to a method of dispersing polyaniline nanofibers (PANI NFs) and graphene sheets in a polyacrylate resin solution for optimizing the conductive solution suitable for DLP-type 3D printing. Dispersion and morphology of the samples with different filler contents were investigated by field emission scanning electron microscope (FE-SEM) and optical microscope (OM) analyses. The polyacrylate composite solution employing the PANI NFs and graphene was printed well with various shapes and sizes through the 3D printing of DLP technology. In addition, the electrical properties of the printed sculptures have been investigated using a 4-point probe measurement system. The printed sculpture containing the PANI NFs and graphene sheets exhibited electrical conductivity (4.00 × 10−9 S/cm) up to 107 times higher than the pure polyacrylate (1.1 × 10−16 S/cm). This work suggests potential application of the PANI NF/graphene cofiller system for DLP-type 3D printing.

Increasing the strength of destroyed wood of wooden architecture monuments by surface modification

The Anglican Church in Arkhangelsk built in 1833 represents a wooden architecture monument. The article describes the strengthening of partially destroyed samples of the Anglican Church wood by surface modification. The first layer of the sandwich coating is nitrilotrimethylphosphonic acid, which forms covalent bonds with the substrate, partially strengthening the wood. The second layer is an epoxy resin solution, which forms covalent bonds with the coating of the first layer, with hydroxyl groups of the first layer involved in the curing of the second layer as well. A two-layer surface coating is formed, while the strength of the wood increases by 2 – 2.5 times, water absorption decreases by 3 times, and mass loss in combustion is no more than 9% according to GOST 27484-87. The monument preservation increases.