Deterioration of polyaramid and polybenzimidazole woven fabrics after ultraviolet irradiation

In this study the degradation of woven fabrics of meta‐aramid and the blend of para‐aramid and polybenzimidazole fibers when exposed to environmental conditions has been investigated under accelerated ageing conditions. Generally, these polymeric materials have been used for the outer layer of protective clothing, particularly for fire‐fighting. The performance of these fabrics plays an important role in preventing burn‐injuries to fire fighters. Frequent exposure of these materials to various environmental conditions (especially sunlight) can degrade the polymeric chain and affect their performance properties. Hence, the degradation of the fabrics has been studied in terms of loss of tensile and tear strength; reduction in abrasion resistance; and extension at break. It was observed that ultraviolet (UV) irradiation negatively impacted on the mechanical properties of both the polymeric materials significantly. This can be attributed to chemical changes in the polymeric chains due to the photo‐oxidation of the polymer. Scanning electron microscopy images revealed surface decomposition of the filaments due to UV irradiation. Exposure of polybenzimidazole resulted in rapid loss of mechanical and chemical properties in comparison with meta‐aramid. However, decomposition and degradation of polybenzidimazole was not statistically significant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43073.     

Preparation of photoresponsive polymeric adsorbent containing amphiphilic polymer with azobenzene moiety and its application for cell adhesion chromatography

In order to develop a new type column chromatography, a polymeric adsorbent was prepared by grafting a photoresponsive polymer containing an azobenzene moiety on the surface of controlled pore glass beads. The polarity of the surface of the polymeric adsorbent was increased by UV irradiation because of trans–cis isomerization of azobenzene moiety. Adhesion chromatography of erythrocytes was carried out using the photoresponsive polymeric adsorbent. The erythrocytes were adhered to the adsorbent in the dark and separated from the adsorbent by UV irradiation. This behavior appears to be caused by the photoresponse of the polarity change on the surface of the polymeric adsorbent. The morphology of the erythrocytes which adhered on the surface of the photoresponsive polymeric adsorbent remained unchanged both in the dark and after UV irradiation. The amount of erythrocytes which adhered to the adsorbent increased with increasing the molecular weight of the grafted polymer and the hydrophobicity of the surface.     

Study of poly(vinyl chloride)/acrylonitrile–styrene–acrylate blends for compatibility,toughness, thermal stability and UV irradiation resistance

A novel rigid poly(vinyl chloride) (PVC)/acrylonitrile–styrene–acrylate (ASA) copolymer blend with good ultraviolet (UV) irradiation resistance and toughness was reported. ASA with good weatherability and toughness was mixed with PVC by conical twin‐screw extruder to improve the UV irradiation resistance and toughness of PVC. The blends were characterized using Fourier‐transform infrared spectra, dynamic mechanical analysis, and scanning electron microscope. Notch Charpy impact test was used to characterize the UV radiation induced changes in toughness. The results showed that ASA was able to toughen PVC with simultaneously improving heat resistance, thermal stabilization, and protecting PVC from irradiation photochemical degradation. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2143–2151, 2013     

Topographical and chemical characterization of polymer surfaces modified by physical and chemical processes

Nanoscale changes to the surface of polymeric materials enables changes in materials' adhesion, wettability, printability, chemical functionality, and bioactivity, while maintaining desirable bulk properties. Polymer surface modification is therefore used in applications such as antimicrobial or non‐fouling materials, biosensors, and active packaging. The range of available modification and analytical techniques used across laboratories prevents accurate comparison of techniques in terms of their effects on surface chemistry and topography. It was therefore our goal to evaluate the effects of four surface modification techniques (chromic acid, piranha solution, ultraviolet irradiation, and oxygen plasma) on polyethylene films. Changes in surface chemistry and topography were quantified using attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), contact angle measurement, and direct measurement of available surface carboxylic acids. Roughness increased in the order: piranha (57.7 nm); oxygen plasma (76.3 nm); UV irradiation (76.4 nm); chromic acid (120 nm). Hydrophobicity decreased in the order: piranha (77.20), chromic acid (73.50), oxygen plasma (61.70), UV irradiation (58.70). Functionalization (by IR absorbance intensity between 1680–1780 cm⁻¹) increased in the order: oxygen plasma (0.06), piranha (0.09), chromic acid (0.34), UV irradiation (0.50). By analyzing these methods using consistent analytical techniques, side‐by‐side comparisons have been accurately made. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

CdS/PVA In-Situ Polymerization Composite Films with Enhanced Structural,Optics, Limiting Effect and Electrical Properties

Cadmium sulfide doped Poly(vinyl alcohol) (CdS/PVA) polymeric films have synthesized by using in-situ polymerization technique and ultrasonic approach at the various molar weight of CdS. Subsequently, CdS/PVA polymeric films have been prepared with the objective of studying the effect of CdS nanoparticles on structural, optical and dielectric properties of PVA matrix films. XRD analysis was used to investigate the structural changes of CdS/PVA polymeric films. XRD study evidently shows a cubic crystal structure for CdS powder with the lattice constants a?=?5.818 Å and the space group F-43m. All polymeric films revealed the appearance of smaller new peaks related to the presence of CdS into PVA matrix. The dependence of optical properties was investigated by using UV–vis spectroscopy. The estimated band gaps energies revealed a redshift that confirms the active region in solar cell devices. The optical limiting effect showed a completely UV–Vis blocking of the synthesized polymeric films at the high molar of CdS contents. Dielectric properties were measured by using high-frequency LCR meter (4200-SCS) and were found to be strongly dependent on frequency and molar of CdS concentration. Dielectric permittivities were strongly influenced by the applied angular frequency and the real parts were decreased with increasing the molar CdS concentration. AC conductivity increased with angular frequency and decreased with increase in molar weight of CdS content. The results revealed that all synthesized materials are potentially suitable for optics technology devices.     

The effect of some fluoropolymers' structures on their response to UV irradiation

The response of three commercial fluoropolymer films, untreated and γ-irradiated poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) (PVDF), and poly(ethylene-co-tetrafluoroethylene) (ETFE), to ultraviolet (UV) irradiation was studied. The changes in tensile properties, thermal behavior, and chemical structure were investigated. The UV resistance of the PVF film is the lowest, and that of ETFE is the highest among the studied films. The biaxially oriented PVF films undergo massive chain scission under the UV irradiation. The chain scission process in both oriented PVF and PVDF films, although at different levels, is accompanied by increased solubility, increased upper glass transition temperatures, and decreased elevated temperature shrinkage. The UV exposure at 50°C, above the polymers' T_g has annealing effects, mainly reflected by a shift to higher temperatures of their upper glass transition. PVF films are unaffected by a low-dose ionizing radiation. However, the γ-irradiated films show reduction of their UV resistance. PVDF films undergo both chain scission and crosslinking by γ radiation, and the addition of UV exposure mainly causes further chain scission. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1471–1481, 1998     

Correlation between Macro- and Microstructural Changes in Ge:SiO2 and SiO2 Glasses under Intense Ultraviolet Irradiation

The photochemical transformation mechanism of defects in germanosilicate and silica glasses under ultraviolet (UV) laser irradiation has been investigated based on the changes in Raman spectra before and after irradiation. Two types of silica glasses, fused silica (type I) and dry synthetic silica (type IV), and germanosilicate optical fiber preforms were irradiated by intense UV photons from excimer lasers. Spectral changes in optical absorption and Raman spectra were examined to clarify a correlation between the microscopic defect formation and the macroscopic structural changes causing a photorefractive effect. Successive generation of E' centers through divalent centers is closely correlated with changes in Raman spectra, indicating that large structural changes in the glass network involved in this process would be the origin of photon-induced densification of the glasses. In addition, it has been proposed that the successive generation of E' centers is mediated by transient divalent centers converted from relaxed cation homobondings.     

Effect of Gamma Irradiation on Structural and Optical Investigations of Borosilicate Glass Doped Yttrium Oxide

The structural, physical, and optical properties of prepared glass samples of the composition formula 30SiO₂-(40-x)B₂O₃-20Na₂O-10Al₂O₃-xY₂O₃, where x = 0, 1, 5, 7 (wt%) were studied before and after gamma irradiation using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-visible spectroscopy. The optical absorption spectra of study glasses were recorded in the UV/visible range of 200–900 nm. The optical band gap energies were calculated from absorption data. These results show that E_opt decreases with increasing concentration of Y₂O₃. The changes occurring in the optical parameters obtained from absorption spectra before and after irradiation have been referred to irradiation induced structural defects and compositional changes.     

Mechanical properties of clay coating films containing styrene–butadiene copolymers

The mechanical properties of clay-based pigmented coating films bonded with a series of carboxylated styrene–butadiene latex binders have been investigated. The in-plane tensile strength and the elongation at rupture increased with increasing amount of polymeric binder. It is suggested that this is due to an improvement in stress transfer through the structure. The mechanical behavior of the films was furthermore found to be strongly related to the properties of the polymeric binder at the usage temperature. In torsional pendulum experiments an increase in the glass transition temperature of the polymeric binder was observed when it was incorporated in the coating film. This is interpreted as being the result of a decrease in the segmental mobility of the polymer molecules due to the presence of the clay particles, i.e., due to the interaction between the clay pigments and the binder. The interaction was, however, less noticeable in experiments using an NMR (nuclear magnetic resonance) technique. If the clay was replaced by calcium carbonate, a strong interaction, as measured using NMR, was observed between CaCO₃ and the styrene–butadiene polymer, although the in-plane mechanical strength and ductility were reduced. A structural model accounting for some of the observed differences in mechanical behavior between clay-based and CaCO₃-based coating films is suggested.     

紫外光照射对新型双马来酰亚胺基复合材料性能的影响

利用紫外灯对T700碳纤维增强双马来酰亚胺基复合材料(T700/5429)进行了90 d的紫外光照射,采用扫描电子显微镜、万能试验机、傅里叶变换红外光谱仪及动态热机械分析仪分析了紫外光照射前后复合材料的表面形貌、弯曲断面形貌、特征基团透射峰面积及力学性能的变化情况。结果表明,经90 d的紫外光照射后,T700/5429表面纤维出现裸露,树脂基体有脱落的现象;而复合材料的面内压缩强度和弯曲强度保持较好。透射峰面积的变化、纤维裸露及玻璃化转变温度的降低表明了90 d紫外光照射会使双马来酰亚胺树脂基体的酰亚胺环裂解。     

Adhesion Performance and UV-Curing Behaviors of Interpenetrated Structured Pressure Sensitive Adhesives with 3-MPTS for Si-Wafer Dicing Process

Abstract

As Si-wafers, as used in the electronic industry, become thinner and thinner, it is important to investigate the conditions which are suitable for easily peelable acrylic dicing tapes. In the ‘pick-up’ process, the adhesion strength decreased after UV irradiation as a result of polymer network formation. In this study, interpenetrating polymer network (IPN) structured acrylic pressure sensitive adhesives (PSAs) were investigated with two different types of UV irradiation — a steady UV irradiation and a pulsed UV irradiation of 100 mJ/cm². The PSAs binder contained 2-ethylhexyl acrylate (2-EHA), acrylic acid (AA) and 3-methacryloxypropyl trimethoxysilane (3-MPTS). The hexafunctional monomer, dipentaerythritol hexacrylate (DPHA) and 3-methacryloxypropyl trimethoxysilane (3-MPTS) were used as diluent monomers. The adhesion performance as related to the peel strength and the tack properties on the Si-wafer substrates, was examined with increasing UV dose. The effect of UV-curing on the behavior and viscoelastic properties of the ‘pick-up’ acrylic tapes was investigated using Fourier transform infrared — attenuated total reflectance spectroscopy (FTIR–ATR) and an advanced rheometric expansion system (ARES). It is also necessary to consider the contaminants on the Si-wafer substrates left behind after releasing the dicing tapes, because of possible damage to the Si-wafers and subsequent processes. Field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) analysis revealed little residue on the Si-wafer after removing the tapes and after more than the specific level of UV dose.     

Xerographic printing of textiles: Polymeric toners and their performance

Xerographic printing of a number of common fabrics was investigated. The role of the polymeric binder used for the formulation of the commercially available and custom‐made toners was investigated. Fabric performance tests (crockfastness), friction tests, and morphological investigations using scanning electron microscopy were performed. The intricate relations of toner and fabric properties with the results of an important overall industrial performance test for fabrics (crockfastness) are discussed. Both cohesive and adhesive toner failure can be important. Improved toner performance was achieved with a thermoset polymer as the toner binder. However, curing times for the thermoset polymer used are not sufficiently short for high‐speed industrial printing. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2425–2434, 2000     

Enhancement of Photostabilization of Poly(vinyl chloride) Doped with Sulfadiazine Tin Complexes

New sulfadiazine tin complexes were synthesized in 67–80% yields from the reaction of sulfadiazine, and different organotin(IV) chlorides and their structures were established. The synthesized complexes were used as additives at a low concentration (0.5% by weight) to enhance poly(vinyl chloride) (PVC) photostability. The PVC samples containing sulfadiazine tin complexes (thickness = 40 μm) were fabricated and irradiated with ultraviolet light at room temperature for 300 h. The changes that occurred within the PVC samples upon irradiation were investigated by inspecting the loss in weight, reduction in the average molecular weight, formation of small degradation fragments containing polyene, carbonyl, and hydroxyl moieties, and changes in the ultraviolet absorption intensity of polymeric materials. The surface morphology of irradiated PVC samples was investigated using optical, atomic force, and scanning electron microscopies. There were lesser changes within the PVC samples with sulfadiazine tin complexes compared to the blank PVC sample. The dimethyltin(IV) complex was found to be the most efficient additive in stabilizing PVC against irradiation. The role played by the complexes in reducing the photodegradation of PVC was investigated, and a mechanism was proposed. J. VINYL ADDIT. TECHNOL., 26:370–379, 2020. © 2019 Society of Plastics Engineers     

Variation of lexan polycarbonate properties by electron beam

The modifications in microstructural, optical, and photoluminescence properties of the Lexan polycarbonate (bisphenol‐A‐polycarbonate) films exposed to different electron doses have been studied using UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), positron annihilation lifetime spectroscopy, photoluminescence spectroscopy, and scanning electron microscopy (SEM). The obtained UV–vis spectroscopy results showed decrease in optical energy gap, optical activation energy, and increase in number of carbon atoms per cluster with increase in electron dose. The chemical changes in electron irradiated polymers due to chain scission and reconstruction have been observed from FTIR spectroscopy. The correlation of positron lifetime study with optical measurement is obtained, and electron irradiation‐induced microstructural modifications within the polymer is understood. SEM result shows the degradation of Lexan polymer after electron irradiation. The mechanical properties and average molecular weight of Lexan decrease after irradiation, whereas average number of chain scissions per original polymer molecule increases. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

紫外老化对UP/GF层合板性能的影响

对玻璃纤维增强不饱和聚酯树脂(UP/GF)基层合板进行了人工紫外加速老化试验,分析了试样紫外老化前后的巴氏硬度、质量保持率以及拉伸、弯曲性能的演变规律。结果表明,随紫外老化时间的增加,试样的巴氏硬度呈先上升后下降的趋势;紫外老化最初的168 h内,质量损失率占整体质量损失的近50%,之后保持在一个相对平稳的状态;其拉伸强度和弯曲强度在紫外老化前期有所上升,在紫外老化168 h开始下降;从傅立叶变换红外光谱图中可以看出,试样中没有新的物质产生,只是化学结构发生了变化;紫外老化后,UP含量明显减少,在拉伸断裂过程中,有明显的玻璃纤维从UP树脂中拔出而留下凹槽空洞。     

A macroscopically nondestructive method for characterizing surface mechanical properties of polymeric coatings under accelerated weathering

The surface of coatings and plastics is the first target in any degradation process initiated by ultraviolet (UV) radiation or mechanical stress (via scratch and abrasion). Surface damage can lead to changes in optical, morphological, and mechanical properties and can result in pathways for ingress of moisture and corrosive agents. Current test methods for monitoring performance of protective coatings focus on chemical properties and optical properties, such as color and gloss measurements, or invasive tests such as abrasion and cross-cut adhesion. In this study, a macroscopically nondestructive performance protocol using nanoindentation metrology via a well-controlled scratch test was applied to evaluate the scratch resistance and monitor the surface mechanical property changes in a protective coating under accelerated weathering. Polyurethane (PU) coatings with different polyol compositions were chosen for this study. Coating specimens were exposed to high-intensity UV radiation at 55°C and 75% RH conditions. Exposed specimens were removed at specified UV exposure times for surface modulus/hardness and scratch resistance characterization via nanoindentation and scratch test. The effect of polyol type and UV radiation dose on the scratch damage (scratch morphology) was investigated and correlated with the surface hardness and modulus of the materials.     

Side chain functional carbazole-fluorene electroactive polymers: Optical,electrochemical properties,antimicrobial activity and thin film morphologies

A new electroactive polymer based on fluorene and carbazole moieties with double bond side chain (MP25) was synthesized and then double bond at the side chain was functionalized with  COOH and  Si(OEt)₃ as ITO/glass compatible groups. Electrochemical and optical properties of the polymers were elucidated with cyclic voltammetry (CV), ultraviolet–visible absorption (UV–Vis), and photoluminescence (PL) spectroscopy. It was observed that all polymers absorbed only the UV region and emitted blue light. By using CV, HOMO values were found as approximately 5.45 eV. According to AFM results, when the rough MP25 polymer thin film was modified with ITO/glass compatible groups, more uniform and smoother polymer thin films were obtained. Thermogravimetry analyses (TGA) shown that the MP25-Si and MP25-COOH were stable against thermo-oxidative decomposition. The weight loss of MP-25-Si was found to be only %23 at 700°C. Additionally, antimicrobial activity of MP25 polymers was also investigated. According to test results, all polymers were found to have antimicrobial activity against C.albicans.     

Influence of the environment during a photodegradation of multilayer films

The influence of different stratosphere parameters on the degradation of a multilayer film was investigated. The selected multilayer was a three polymeric layers film, a polyamide 6 film inserted between two poly(ethylene terephthalate) (PET) films. Samples were exposed for several ageing under ultraviolet radiations (filtered at 270 nm), varying the atmosphere at 55 mbar pressure (atm, atm + ozone, N₂, and T = ?55 °C or +23 °C). Evolution of it mechanical properties defined by uniaxial tractions, thermo‐optical properties defined by spectrophotometry UV–vis‐NIR, chemical properties defined by FTIR‐ATR, and thermal and dielectric properties defined, respectively, by differential scanning calorimetry (DSC) and dynamical dielectric spectroscopy (DDS), were investigated. Our results showed that UV irradiation causes multilayer films degradations, that is, principally decrease of UV transmittance and stress and strain at break (?50%). An increase of the ageing temperature causes an acceleration of these degradations. Degradations principally occur on the PET side of the multilayer exposed to UV radiation. Moreover, the DDS analysis shows a plasticization effect of the primary mode in the polyamide 6 due to photo‐oxidation. Oxygen diffusion is the principal element for this plasticization, indeed it not occurs in a nonoxidative environment (nitrogen), or at low ageing temperature (?55 °C). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44075.     

Pretreatment of wool/polyester blended fabrics to enhance titanium dioxide nanoparticle adsorption and self‐cleaning properties

This research aims to enhance the self‐cleaning properties of fibre‐blended fabric using surface pretreatment prior to the application of titanium dioxide nanoparticles. To this end, the polyester/wool fabric was modified, in that the wool fibres were oxidised with potassium permanganate and the polyester fibres were hydrolysed with lipase before nano processing. Butane tetracarboxylic acid was also used to enhance the adsorption of the nanoparticles and also to stabilise them on the fabric surface. The self‐cleaning properties of the fabric were examined through staining of the fabric with CI Basic Blue 9 and then discolouring by exposing to ultraviolet and daylight irradiation. Some other properties of the treated fabrics, such as water drop absorption, crease recovery angle and bending were investigated and are discussed in detail. The colour changes of different samples indicated an appropriate discoloration on the titanium dioxide‐treated fabrics after ultraviolet and daylight irradiation. Overall, the surface pretreatment of the wool and polyester fibres improved the self‐cleaning properties of the fabric significantly.