Study on the Microstructure of Polyester Polyurethane Irradiated in Air and Water

Inactivation of microorganisms on fabrics using plasma-activated nebulized mist driven by different plasma gases

The disinfection of fabrics is crucial in preventing the spread of infectious diseases caused by pathogenic microorganisms to maintain public health. A previous study proved that plasma-activated nebulized mist (PANM) could effectively inactivate microorganisms both in aerosol and attached to the surface. In this study, the PANM driven by different plasma gases were employed to inactivate microorganisms on diverse fabrics. The PANM could efficiently inactivate a variety of microorganisms, including bacteria, fungi, and viruses, contaminating different fabrics, and even across covering layers of different fabrics. The mites residing on the cotton fabrics both uncovered and covered with various types of fabrics were also effectively inactivated by the PANM. After 30 times repeated treatments of the PANM, notable changes were observed in the color of several fabrics while the structural integrity and mechanical strength of the fabrics were unaffected and maintained similarly to the untreated fabrics with slight changes in elemental composition. Additionally, only trace amounts of nitrate remained in the fabrics after the PANM treatment. Therefore, the PANM treatment supplied an efficient, broad-spectrum, and environmentally friendly strategy for industrial and household disinfection of fabrics.

Effects of Low-Level Gamma Radiation on Common Nitroaromatic, Nitramine, and Nitrate Ester Explosives

The aging of high explosives in an ionizing radiation field is not well understood, and little work has been done in the low dose and low dose rate regime. In this study, four explosives were exposed to low-level gamma irradiation from a 137Cs source: PETN, PATO, and PBX 9501 both with and without the Irganox 1010 stabilizer. Post-irradiation analysis included GC-MS of the headspace gas, SEM of the pellets and powder, NMR spectroscopy, DSC analysis, impact sensitivity tests, and ESD sensitivity tests. Overall, no significant change to the materials was seen for the dose and dose rate explored in this study. A small change in the 1H NMR spectrum of PETN was observed and SEM and ESD results suggest a surface energy change in PATO, but these differences are minor and do not appear to have a substantial impact on the handling safety.

Recent Developments in Lignin- and Tannin-Based Non-Isocyanate Polyurethane Resins for Wood Adhesives—A Review

This review article aims to summarize the potential of using renewable natural resources, such as lignin and tannin, in the preparation of NIPUs for wood adhesives. Polyurethanes (PUs) are extremely versatile polymeric materials, which have been widely used in numerous applications, e.g., packaging, footwear, construction, the automotive industry, the lighting industry, insulation panels, bedding, furniture, metallurgy, sealants, coatings, foams, and wood adhesives. The isocyanate-based PUs exhibit strong adhesion properties, excellent flexibility, and durability, but they lack renewability. Therefore, this study focused on the development of non-isocyanate polyurethane lignin and tannin resins for wood adhesives. PUs are commercially synthesized using polyols and polyisocyanates. Isocyanates are toxic, costly, and not renewable; thus, a search of suitable alternatives in the synthesis of polyurethane resins is needed. The reaction with diamine compounds could result in NIPUs based on lignin and tannin. The research on bio-based components for PU synthesis confirmed that they have good characteristics as an alternative for the petroleum-based adhesives. The advantages of improved strength, low curing temperatures, shorter pressing times, and isocyanate-free properties were demonstrated by lignin- and tannin-based NIPUs. The elimination of isocyanate, associated with environmental and human health hazards, NIPU synthesis, and its properties and applications, including wood adhesives, are reported comprehensively in this paper. The future perspectives of NIPUs’ production and application were also outlined.

Chemistry for Audio Heritage Preservation: A Review of Analytical Techniques for Audio Magnetic Tapes

Vast and important cultural resources are entrusted to magnetic tape around the world, but they are susceptible to degradation, which may lead to severe replay problems. Audio magnetic tapes are complex and multicomponent devices containing organic compounds and metal systems, which can be potential catalysts for many degradative reactions in the presence of water, light, or heating. The aim of this review is to collect the literature concerning the analytical determinations and instrumental approaches that can achieve the chemical identification of the components in the tape and the degradation state. Thus, a combination of destructive (such as acetone extraction) and non-destructive techniques (such as ATR FTIR spectroscopy) have been proposed, together with SEM, ESEM, XRD and TGA analyses to assess the chemical and physical characterization of the tape with the purpose to individualize restoration treatments and optimize conditions for preservation. The impact of the studies reviewed in this paper may go beyond audio, being potentially relevant to video, data, instrumentation, and logging tapes.

FT-IR investigations on effect of high doses of gamma radiation-induced damage to polystyrene and mechanism of formation of radiolysis products

The present article focuses on the influence of gamma irradiation and post-irradiation storage conditions on FT-IR spectra of 1 mm thick polystyrene irradiated with 51, 77 and 129 kGy. The increase in amplitude corresponding to 3600, 3400 and 2100 cm^- 1 stretching frequencies clearly showing the formation of O-H and C=O bonds (~ 25%). On prolonged storage (2160 h) in the dark, there is an increase in O-H group (~ 28%). The electron cloud facilitates the formation of hydroxyl group in irradiated polystyrene. The post-irradiation treatment with heat conversely showed a reduction of O-H, C-H and C=O (9-16%) groups due to radical-radical recombination at higher temperatures and light intensities. This investigation finds its applications in memory devices, optical sensors, radiation dosimetry and different space and radiation facilities.

Environmentally-Friendly Synthesis of Carbonate-Type Macrodiols and Preparation of Transparent Self-Healable Thermoplastic Polyurethanes

Carbonate-type macrodiols synthesized by base-catalyzed polycondensation of co-diols and dimethyl carbonate as an environmentally-friendly route were subsequently utilized for the preparation of transparent and self-healable thermoplastic polyurethanes (TPUs) containing a carbonate-type soft segment. Three types of macrodiols, obtained from mono, dual and triple diol-monomers for target molecular weights of 1 and 1.5 kg mol-1, were analyzed by ¹H NMR integration and the OH titration value. Colorless transparent macrodiols in a liquid state at a room temperature of 20 °C were obtained, except the macrodiol from mono 1,6-hexanediol. Before TPU synthesis, macrodiols require pH neutralization to prevent gelation. TPUs synthesized by a solution pre-polymer method with 4,4'-methylene(bisphenyl isocyanate) and 1,4-butanediol as a chain extender exhibited moderate molecular weights, good transparencies and robust mechanical properties. Especially, the incorporation of 3-methyl-1,5-pentanediol within carbonate-type macrodiols enhanced the transparency of the resultant TPUs by decreasing the degree of microphase separation evidenced by ATR-FTIR and DSC. Interestingly, packing density of hard segments and the degree of microphase separation determined the self-healing efficiency of TPUs, which showed good performances in the case of sourced macrodiols from triple diol-monomers.

Radiation Crosslinking of Polyurethanes: Characterization by FTIR, TGA, SEM, XRD, and Raman Spectroscopy

Gamma radiation can be used for enhancing the physical properties of polyurethane (PU). Radiation was used to crosslink a polyurethane at room temperature; four samples of the PU solid film are irradiated at variable four radiation doses 0, 50, 100, and 150 kGy under vacuum conditions. Crosslinking radiation is more common than oxidative degradation and crosslinking is believed to be more efficient in the soft segment of PU. The structure of the PUs is performed by Fourier transform infrared (FTIR-ATR), Thermogravimetric Analysis (TGA-DTG), and X-ray Diffraction (XRD) which have been used to investigate the effect of gamma radiation on the polyurethane (PU). The results showed that the radiation crosslinking of polyurethanes improved the thermal stability and the crystallinity. The microstructure modifications of polyurethane samples have also been studied as a function of the dose using the scanning electron microscope (SEM). The effects of gamma irradiation on the color changes of polyurethane were observed. The irradiated PUs have conjugated structure and are capable of emitting purple fluorescence.

Microstructure Changes in Polyester Polyurethane upon Thermal and Humid Aging

The microstructure of compression molded Estane 5703 films exposed to 11%, 45%, and 80% relative humidity and 70 °C for 1 and 2 months has been studied by small-angle neutron scattering (SANS), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Scattering data indicated increase of the interdomain distance and domain size with a higher humidity and longer aging time. GPC data showed a progressive shortening of polyurethane chains with increasing humidity and aging time. The shortening of the polyurethane chains caused a drop of the glass transition temperature of soft segments, and promoted crystallization of the soft segments during long-time storage of the aged samples at room temperature. FTIR showed a substantial increase in the number of inter-urethane H-bonds in the aged samples. This correlates with the increase of the hard domain size and the degree of phase separation as measured by SANS. The data collected reveals that the reduced steric hindrance caused by hydrolysis of ester links in polybutylene adipate residues promotes the organization of hard segments into domains, leading to the increase of domain size and distance, as well as phase segregation in aged Estane. These findings provide insight into the effects of humidity and thermal aging on the microstructure of aged polyester urethane from molecular to nanoscale level.