Basic dyeable polyester: a new approach using a VUV excimer lamp

Surface treatment of polyester fabric was carried out using a vacuum ultraviolet (VUV) excimer lamp. The hydrophilicity of the polyester fabric was significantly improved by surface modification, as indicated by the decrease in wetting time and wicking time. This approach can be used to create added value for polyester fabric, which otherwise suffers from low hydrophilicity. Further changes on irradiation were characterised by atomic force microscopy and the crystallinity and tensile strength of the samples were also tested. Basic dyeability of the microdenier polyester fabric was seen to improve greatly on exposure to the excimer lamp, followed by grafting with acrylic acid. The effects were observed to increase with an increase in irradiation time. The best effect was obtained for irradiation time of 10 min. These enhanced properties were accompanied by an insignificant loss in crystallinity and tensile strength of treated fabrics.     

Grafting of silk with electron beam irradiation

The radiation-induced graft polymerisation of hydroxyethyl methacrylate on silk fabric has been studied using an electron beam irradiation technique. Two irradiation processes, pre-irradiation and coirradiation, were compared, and some factors affecting the degree of grafting were investigated. The physical and mechanical properties such as whiteness, breaking strength and resilience of the radiation-grafted silk fabrics were examined. The hydroxyethyl methacrylate grafting of silk with electron beam irradiation increases silk weight and improves the crease resistance of silk. Electron spin resonance technique shows the formation of free radical species on the electron beam irradiated silk and the rapid decay of radicals in water.     

Radiation grafting/crosslinking of silk using electron‐beam irradiation

The radiation grafting of silk with methacrylamide (MAA) was studied using an electron‐beam (EB) irradiation technique. Two irradiation processes, preirradiation and coirradiation, were compared, and some factors affecting the degree of grafting were investigated. The radiation crosslinking of silk with dimethyloldihydroxyethylene urea (DMDHEU) was preliminarily studied. The physical and mechanical properties such as whiteness, breaking strength, and resilience of the radiation‐grafted/crosslinked silk fabrics were examined. The radiation grafting of silk with MAA increases the silk weight, while the radiation crosslinking of silk with DMDHEU imparts improved crease resistance to silk. X‐ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) analysis indicate the formation of peroxy and free‐radical species on the EB‐irradiated silk. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2028–2034, 2004     

Electron beam-induced crosslinking of silk fibers using triallyl isocyanurate for enhanced properties

In this paper, electron beam (EB) radiation-induced crosslinking of silk fibers by triallyl isocyanurate was accomplished for the first time by exposing the silk fabric in an inert atmosphere. The effect of EB dose (100–300 kGy) on the degree of crosslinking was found to show correlation with sol–gel contents and confirmed by Charlesby–Pinner plot along with their chemical stability in different solvents. Uniform and homogeneous distribution of particles on the fiber surface was observed under a scanning electron microscope, and elemental composition of those particles was detected similar to the silk by energy-dispersive X-ray spectra. Chemical changes occurred due to EB irradiation and crosslinking in the silk polymer was affirmed by attenuated total reflectance–Fourier transform infrared spectroscopy. From the thermogravimetric analyses, the thermal stability of the irradiated fibers with respect to weight loss was found to have increased from 17 to 32% at higher temperature range. The changes in mechanical property, stiffness, water contact angle, and degree of crosslinking of silk proportionately change with respect to the EB dose. However, 200 kGy EB dose was found optimum based on physical, chemical, and thermal properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47888.     

Effects of ultraviolet irradiation treatment on the surface properties and adhesion of moso bamboo (Phyllostachys pubescens)

The poor adhesion of bamboo coatings is a serious issue in the bamboo industry. To overcome this problem it is necessary to modify the actual surface of the bamboo before finishing. A study on the surface properties and adhesion of moso bamboo (Phyllostachys pubescens) were investigated with various UV irradiation conditions including irradiation time and dose using different UV lamps. Two types of wood coatings, i.e., solvent‐borne nitrocellulose (NC) lacquer and waterborne polyurethane (PU) coating, were used in the study, and 180° peel strength and shear strength tests for measuring adhesion of films were conducted. The results revealed that the wettability and the carbonyl group concentration of the bamboo surface were increased. This was particularly apparent for an irradiation time less than 15 s with a mercury UV lamp (H‐lamp), rated at an intensity of 100 W/cm kept at a distance of 15 cm. In all the treatments, the greenish appearance of moso bamboo was retained and the adhesion was improved. Especially, using solvent‐borne NC lacquer finishing, the higher‐dose (under a mercury UV lamp combined with metal halide lamp; H + M‐lamps) irradiated bamboo had the best adhesion, while, for waterborne PU coating, the H‐lamp irradiated one showed the best improvement. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

γ-Ray-induced degradation: A comparative study for homo- and copolymers of polypropylene

Disposable medical supplies are currently made of polypropylene, which are conveniently sterilized by exposure to γ-rays. However, the homopolymers (HP) and random copolymer (CP) of polypropylene, when exposed to high-energy γ-irradiation, undergo oxidative degradation and loss in mechanical properties. In the current article, a comparative study of the effect of γ-irradiation at different irradiation doses and the postirradiation oxidation on both the polymers is reported. The loss in mechanical properties was monitored by the bend angle and tensile measurements. The yellowness index measurements were carried out as a function of the irradiation dose and postirradiation storage time. The changes in the molecular weight (MW) and molecular weight distribution (MWD) were monitored using melt index (MI) measurements. The changes in chemical structure was determined using infrared spectroscopy. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2715–2720, 1997     

Effect of ultraviolet irradiation on the selective transport of alkali metal ions through 2,3-epithiopropyl methacrylate–methacrylic acid copolymer membrane

Cationic exchange membranes were prepared with 2,3-epithiopropyl methacrylate (ETMA)–methacrylic acid (MAc) copolymer. Transport of alkali metal ions against their concentration gradient through the membranes was investigated by using the system which contains HCl (left side) and alkali metal solution including two kinds of alkali hydroxides (right side). The effect of ultraviolet (UV) irradiation on the selective transport of alkali metal ions through the ETMA–MAc copolymer membranes was investigated. The membranes were irradiated with a 6-W low pressure mercury lamp at a distance of 10 cm at room temperature in air. The transport selectivity could be increased by using UV-irradiated membranes and the selectivity increased with increasing irradiation time up to 2–3 h, although the transport rate of alkali metal ions decreased with increasing time of UV irradiation. The maximum selectivity of K⁺/Na⁺, Na⁺/Li⁺, and K⁺/Li⁺ were 1.7, 2.0, and 4.2, respectively. In order to explain this phenomena, the effect of UV irradiation on the properties of the membranes was studied. It was concluded that the increase of the selectivity is attributed to the formation of the dense membrane by photocrosslinking of the membrane by UV irradiation.     

Structure and physical properties of epoxide-treated tussah silk fibers

The structural characteristics and physical properties of epoxide-treated tussah silk fibers from Antheraea pernyi silkworm are discussed in relation to the increasing weight gain values. Ethyleneglycol diglycidylether (E) and glycerin diglycidylether (G) were used as modifying agents. The noticeably high weight gain values (about 140%) obtained were attributed to the catalytic effect of SCN^? anion absorbed by the fibers during the pretreatment under reduced pressure conditions. The amino acid analysis showed that epoxide G exhibited a slightly higher reactivity toward tyrosine, while arginine preferably reacted with epoxide E. The peak of loss modulus (E″) determined by dynamic viscoelastic measurements became broader and its position linearly shifted to lower temperature when the weight gain increased, and a minor peak appeared in the low-temperature region below 50°C. Differential scanning calorimetry (DSC) thermograms showed that the position of the decomposition peak of modified silk fibers shifted to lower temperature with increasing weight gain values. The minor and broad endothermic peaks, appearing in the reference sample at about 234 and 290°C, disappeared by epoxide treatment. X-ray diffraction patterns of tussah silk fibers suggested that the epoxide treatment does not affect directly the crystalline regions but causes a decrease of molecular orientation in the amorphous regions. Both briefringence (Δn) and isotropic refractive index (n_iso) of tussah silk fibers decreased by the reaction with epoxides, although with different rate and extent, confirming the decrease of average molecular orientation. The extent of decrease of strength and elongation depends on the kind of epoxide and on the weight gain value. Epoxide-treated tussah silk fibers did not show significant changes of surface characteristics as the weight gain values attained up to 60%.     

Biodegradation of Bombyx mori silk fibroin fibers and films

The in vitro biodegradation of Bombyx mori silk fibroin was studied by incubating fibers and films with proteolytic enzymes (collagenase type F, α‐chymotrypsin type I‐S, protease type XXI), for times ranging from 1 to 17 days. The changes in sample weight and degree of polymerization of silk fibers exposed to proteolytic attack were negligible. However, tensile properties were significantly affected, as shown by the drop of strength and elongation as a function of the degradation time. Upon incubation with proteolytic enzymes, silk films exhibited a noticeable decrease of sample weight and degree of polymerization, the extent of which depended on the type of enzyme, on the enzyme‐to‐substrate ratio, and on the degradation time. Protease was more aggressive than α‐chymotrypsin or collagenase. Film fragments resistant to enzymatic degradation were enriched in glycine and alanine. FT‐IR measurements showed that the degree of crystallinity of biodegraded films increased. Soluble degradation products of silk films consisted of a range of peptides widely differing in size, deriving from the amorphous sequences of the silk fibroin chains. Biodegraded fibers showed an increase of surface roughness, while films displayed surface cracks and cavities with internal voids separated by fiber‐like elements. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2383–2390, 2004     

Thermo-Mechanical Properties and Abrasive Wear Behavior of Silicon Carbide Filled Woven Glass Fiber Composites

A study was done to determine the effect of physical, mechanical, thermal and three body abrasive wear response of Silicon Carbide (SiC) filled Glass Fiber Reinforced Epoxy (GFRE) composites. The main purpose was to study the influence of different weight percentages (wt.%) of SiC filler in addition to that of glass fiber. A three body abrasive wear analysis was conducted by varying different factors such as fiber/filler reinforcement, abrasive particle size, normal load, sliding distance and sliding velocity. An attempt was made to find out the dominant factor and the effect of each factor on specific wear rate analysis. Physical and mechanical properties, i.e. density, hardness, tensile strength, flexural strength, inter laminar shear strength and impact strength, were determined for each weight percent of filler reinforcement to determine the behavior of mechanical properties with varying SiC filler loading. Thermo – mechanical properties of the material, i.e. storage modulus, loss modulus and tan delta with temperature were measured using a Dynamic Mechanical Analyzer (DMA). The result shows the increasing / decreasing trend and critical points of each analysis. The trend and major factors responsible for reducing the specific wear rate were determined. Mechanical properties, i.e. hardness and impact strength, increase with the increase in SiC content, whereas tensile strength, flexural strength and inter laminar shear strength decrease. Worn surfaces were studied using scanning electron microscopy (SEM) to give an insight into the wear mechanisms.     

Polyurethanes and polyurethane cationomers bearing nitroaromatic groups and their photobehavior

Elastomer-type polyether urethanes and polyether urethane cationomers with nitroaromatic groups were prepared and the effect of UV irradiation on their characteristics was evaluated comparatively with a model compound. The photobehavior by UV irradiation with a high-pressure Hg lamp was studied in solution, following the change of absorption bands characteristic for nitro structures as a function of irradiation time. UV irradiation causes diminution of the intensity of characteristic UV absorption bands and a decrease of molecular weight.     

Physical properties of silk fibers treated with ethylene glycol diglycidyl ether by the pad/batch method

This paper deals with the epoxide treatment of silk fabrics by the pad/batch method. The optimum reaction conditions, i.e., NaOH concentration, and reaction temperature were 2.5 g/L and 30°C, respectively. A weight gain of 8.5% was attained at a reaction time of 6 h. This value slightly increased to 10% after 24 h. The reactivity of tyrosine and basic amino acid residues was dependent on the reaction time and did not significantly differ from the results of epoxide-treated silk fiber by the conventional method in tetrachloroethylene. The moisture regain slightly decreased at 4% weight gain and then increased with the epoxide content, exceeding the value of the untreated control. The crease recovery of the epoxide-treated silk fabrics measured in the wet state was significantly improved, whereas that in the dry state was almost unchanged. The rate of photoyellowing of the epoxide-treated silk fabrics by the pad/batch method was reduced significantly compared with that of the untreated control. Among the mechanical properties, elongation at break and tensile modulus remained unchanged, whereas the tensile strength slightly increased following the epoxide reaction. The thermal properties were evaluated by DSC and TGA and on the basis of the dynamic viscoelastic measurements. The DSC curve of the epoxide-treated sample showed a slight increase of the decomposition temperature of silk fibroin. The rate of weight loss determined by TGA remained unchanged regardless of the chemical modification, whereas the peak of loss modulus became broader and shifted to lower temperature. The X-ray diffractograms showed that the crystalline structure of silk fibers was not affected by the reaction with epoxides. © 1993 John Wiley & Sons, Inc.     

GPC/LS Analysis of the Photodegradation Products of Poly(phenylmethylsilane)

The photodegradation of poly(phenylmethylsilane) (PPMS) was studied using two sources of irradiation: a commercial Hg lamp and a neodymium: yttrium aluminium garnet (Nd:YAG) laser tuned to a wavelength of 266 nm. The degradation products were studied using a coupled system: Gel Permeation Chromatography/Light Scattering (GPC/LS). We focus on the importance of having a multiangle detector on the line with the GPC to obtain information related to molecular conformation, molecular weight, polydispersity and mass during the photodegradation. The results obtained were a function of the UV source. At the beginning of the photodegradation, the PPMS was strongly affected by the Hg lamp; and, the molecular weight as a function of volume retention showed the presence of at least two different species that contained differently shaped molecules. In the photodegradation of PPMS using Nd:YAG laser, the molecular weight as a function of volume retention showed a single conformation. On the basis of the polydispersity as a function of UV exposure time, it was observed that after 10 seconds of irradiation using either the Hg lamp or the laser source, homolytic scission of silicon–silicon bonds in the termini of the polymer chain was the main depolymerization process. Finally, after 25 seconds (with Hg lamp) and 60 seconds (with laser) of exposure the polydispersity was considerably increased owing to random chain scissions.     

A comparative study of ultrasonic degumming of silk sericin using citric acid,sodium carbonate and papain

The utilisation of ultrasonics has been shown to enable efficient and environmentally friendly textile wet processing. This study conducted a comparative investigation of silk degumming by using a conventional heating bath and ultrasonic irradiation at a range of ultrasonic frequencies. Citric acid, sodium carbonate and papain were used as degumming agents. Sericin degumming rate, fibre whiteness, fibre surface morphology, fibre structure characteristics and fibre tensile properties were measured and analysed. Results showed that ultrasonics at a lower frequency produced a greater degumming rate than at a higher frequency. Ultrasonics is a more effective way than the conventional heating bath of improving degumming efficiency, especially at a lowered temperature of 60 °C. When sodium carbonate was applied at 90 °C, a conventional heating bath was found to be more effective than ultrasonics. Papain was found to be more effective in sericin removal than citric acid and sodium carbonate, with a degumming rate of 22% achieved at 60 °C under ultrasonic irradiation at 40 kHz. The use of papain can, however, cause a possible overreaction to silk under certain severe conditions, resulting in a loss of fibre whiteness. Negligible changes in fibre structure characteristics were measured by Fourier Transform–infrared spectroscopy and X‐ray diffraction after ultrasonic degumming with papain. Slightly reduced fibre strength and increased fibre extensibility were observed in ultrasonically degummed silk samples compared with un‐degummed and conventionally degummed silk samples.     

Chemical modification of Bombyx mori silk with epoxide EPSIB

Bombyx mori silk fabrics were chemically modified by EPSIB (a multifunctional silicone‐containing epoxy crosslinking agent). The reactivity of the epoxy groups with silk fibroin was studied by using amino acid analysis. The physical properties of the modified silks such as resiliency (both wet and dry), moisture regain, dyeing behaviors, and solubility in a mixture solvent (C₂H₅OH × CaCl₂ : H₂O = 2 : 1 : 8, molar ratio) were examined. The modified silk fabrics exhibited a significantly improved resiliency, a small increase in moisture regain and whiteness, and a slightly decreased tensile strength. The contents of Serine, Trosine, Lysine, and Histidine decreased linearly as the wet crease recovery angle (CRA) increased. The solubility in the mixture solvent also decreased as the wet CRA increased. The changes of physical properties, especially the wet CRA, were mainly due to the presence of stable cross‐links between silk fibroin and epoxy groups. The DSC and TGA analyses showed that EPSIB‐modified silk fibroin had a higher thermal stability compared with the control. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3579–3586, 2004     

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。     

Degradation of poly(L‐lactide) films under ultraviolet‐induced photografting and sterilization conditions

The degradation of polymers under ultraviolet (UV) irradiation has been a great concern for biomaterial and agricultural applications. The major objective of this research was to study the effect of UV irradiation on the representative bulk and surface properties of poly (L ‐lactide) (PLA) films. Two UV sources with different spectral outputs and intensities were chosen so that one of them could be used for surface modification and the other could be used for UV sterilization of the PLA films. The results established that the molecular weight of PLA decreased significantly during irradiation from the photografting lamp under atmospheric conditions. Irradiation through a Pyrex container was shown to minimize polymer degradation during UV exposure from the photografting lamp. The PLA films UV‐irradiated under the sterilization lamp for 12 h revealed a similar reduction in the molecular weight and no change in the surface hydrophilicity. However, significantly less photodegradation was observed under the sterilization lamp when the samples were held in a Pyrex container. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

光屏蔽剂对聚甲醛耐老化性能的影响

采用炭黑和纳米级氧化锌两种光屏蔽剂对共聚甲醛进行耐老化改性,对比了改性前后聚甲醛耐紫外光、耐热氧及耐热水老化性能的变化。结果表明,紫外光老化对聚甲醛性能影响最显著,两种光屏蔽剂均能减缓聚甲醛的光降解过程。炭黑的光屏蔽效果优于氧化锌,但会加速聚甲醛热氧降解。聚甲醛试样表面层相对分子质量的变化规律基本上与试样断裂伸长率、冲击强度以及色差变化规律保持一致。     

Physical characteristics of silk fibers modified with dibasic acid anhydrides

The objective of this study was to investigate the physical properties of silk fibers modified with dibasic acid anhydrides. These are potentially attractive modifying agents to reduce the rate of photoyellowing of silk during and following UV irradiation. Several analytical techniques were employed, which included the measurement of the basic mechanical properties (tensile strength and elongation at break), equilibrium regain, amino acid analysis, dynamic viscoelastic measurements, X-ray diffractometry, and scanning electron microscopy (SEM). The succinylated silk fibers, which have been conditioned under different relative humidity atmospheres, always exhibited slightly higher equilibrium regain values than those of equivalently conditioned glutarylated silks. The amount of the basic amino acid residues slightly decreased following modification with both succinic and glutaric anhydrides. The birefringence values and the isotropic refractive indices decreased only slightly, which suggests that the fine structure of the treated silk fibers was not significantly altered. The X-ray diffraction curves demonstrated that no changes in the crystalline structure were induced by reaction with dibasic acid anhydrides. The tensile properties of the modified silks remained more or less unchanged. Only the initial tensile resistance of glutarylated silks in the dry state significantly decreased. The dynamic viscoelastic behavior of modified silk fibers was characterized by a reduced thermal stability. In fact, the onset temperature of the prominent E peak corresponding to the molecular movement shifted to lower values. The surfaces of modified silk fibers were as smooth as that of the untreated control sample. © 1994 John Wiley & Sons, Inc.     

The effect of vacuum and radiation on solid propellant properties

To understand the changes occurring in solid propellants on storage under space environments, the effect of vacuum and radiation on different propellants were studied. It was found that propellants lost weight on vacuum storage and that the rate and extent of weight loss depended upon the plasticizer content, the exposed surface area and the vacuum level. Mechanical properties and burning rates were practically unaffected and the effect on thermal decomposition was marginal. On the other hand, irradiation with gamma rays resulted in a drastic deterioration of mechanical properties and in a large increase in the rate of thermal decomposition at 225 °C. Radiation had no effect on burning rates.