UV-induced graft polymerization of acrylamide on cellulose by using immobilized benzophenone as a photo-initiator

Photo-active moiety, benzophenone, was incorporated onto cotton fabrics by using butyl tetracarboxylic acids (BTCA). Then, grafting of polyacrylamide on the cotton fabrics was performed by exposing the fabrics to longer UV wavelength irradiation. The chemical structure and thermal properties of the polyacrylamide grafted cotton fabrics were investigated by SEM, FTIR, XRD, and TGA, and the results verified the successful grafting of polyacrylamide on cotton fabrics. Also, it was observed that active chlorine contents were created on the polyacrylamide grafted cotton fabrics through simple chlorination process, and the chlorine treated cotton fabrics showed excellent antibacterial abilities like the powerful cyclic amide halamines.     

Improved microwave absorption and electrostatic charge dissipation efficiencies of conducting polymer grafted fabrics prepared via in situ polymerization

Polyaniline (PANI) and polypyrrole (PPY) were grafted over cotton fabrics by in situ polymerization. FTIR spectra show systematic shifting of bands corroborating surface grafting of conducting polymers on cotton fabric. SEM images revealed that the surface coating of PANI was smoother than PPY. However, better control over coating thickness and uniformity was achieved in PPY fabric. The probable formation mechanism of grated fabrics has also been proposed. The good thermal stability and acceptable electronic conductivity values indicate that these fabrics could be used for electrostatic charge dissipation and microwave absorption. The antistatic studies have shown complete charge dissipation (decay time <0.01 sec). The microwave absorption studies of the conducting fabrics in X‐band (8.2–12.4 GHz) show absorption dominated total shielding effectiveness in the range ?11.3 to ?11.7 dB (>92% attenuation) and ?9.2 to ?9.6 dB (>88% attenuation) for fabrics grafted with PPY and PANI, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

Durable antimicrobial cotton fabrics containing stable quaternarized N-halamine groups

A novel N-halamine precursor with tertiary amino group (5,5-dimethylhydantoinyl-3-ylethyl)-dimethylamine (DEADH), was synthesized and then covalently bonded onto cotton fabrics modified by 3-chloropropyltrimethoxysilane to form quaternarized N-halamine precursor grafted cotton fabrics which could be transferred to N-halamine structure upon exposure to dilute sodium hypochlorite solution. The grafted cotton fabrics were characterized by FT-IR, X-ray photoelectron spectroscopy, and field emission scanning electron microscope. The antimicrobial test showed that the cotton fabrics grafted with the quaternarized N-halamine were capable of 7-log inactivation of Staphylococcus aureus and Escherichia coli O157:H7 within 1 min of contact time. Very interestingly, it was found that the grafting process and following chlorination had almost no adverse effect on the tensile strength of cotton fabrics. Furthermore, the antimicrobial cotton fabrics exhibited good washing durability and stability.     

Semiconducting Fabrics by In Situ Topochemical Synthesis of Polydiacetylene: A New Dimension to the Use of Organogels

A diyne functionalized 4,6‐O‐benzylidene β‐d ‐galactopyranoside gelator, which can align its diyne motifs upon self‐assembly (gelation) have been synthesized. The organogel formed by this gelator undergoes topochemical polymerization to polydiacetylene (PDA) under photoirradiation. This strategically designed gelator has been used to make semi‐conducting fabrics. By developing the organogel on the fabrics, the gelator molecules were made not only to self‐assemble on the fibers, but also to adhere to fabrics through hydrogen bonding. UV irradiation of the gel‐coated fabric/fiber resulted in the formation of PDA on fibers. The benzylidene motif could be deprotected to get PDA with pendant free sugars that strongly bind to the cotton fibrils through multiple hydrogen bonds. Conductivity measurements revealed the semiconducting nature of these fabrics.     

Novel UV-protective formulations for cotton, PET fabrics and their blend utilizing irradiation technique

A novel coating formulation to impart ultraviolet (UV) protection property to cotton, Polyethylene trephethalate (PET) and cotton/PET fabrics was prepared and gamma rays as an ionizing radiation was utilized for surface curing. Natural occurring aluminum potassium sulfate (Alum) was used individually and in binary coat with Zinc Oxide (ZnO), to induce the UV-blocking properties. It was found that using Alum (0.3 g/ml) caused a prompt increase in ultraviolet protection factor (UPF) over the uncoated fabrics. Moreover, the incorporated ZnO in the binary coat increased the UPF for two to threefold than the stand-alone Alum coating, specially in case of PET coated fabric. Water absorbance and moisture regain of ZnO and Alum/ZnO coated fabrics showed a decrease over the blank samples, due to the usage of oligomer/monomer combination. On contrary, Alum showed a hydrophilic effect with the increase in its content in the formulation. Surface Electron Microscope showed the homogenous coating of fibers. X-ray diffraction (XRD), energy dispersive X-ray (EDX) and water vapor permeability were also tested for coated samples.     

Surface amine‐functionalization of UHMWPE fiber by bio‐inspired polydopamine and grafted hexamethylene diamine

Ultrahigh molecular weight polyethylene (UHMWPE) fibers exhibit excellent mechanical property, but their low surface activity limits the application in many fields. In this work, an efficient method was used to improve the surface activity and adhesion property of UHMWPE fibers. The amine functionalized UHMWPE fibers were prepared by the combination of bio‐inspired polydopamine (PDA) and grafted hexamethylene diamine (HMDA). The chemical structure of UHMWPE fibers was characterized by X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy. The surface morphologies and mechanical property of the fibers were investigated by scanning electron microscopy and tensile testing respectively. In addition, a single‐fiber pull‐out test was carried out to investigate the adhesion property of the fibers with epoxy resin matrix. The results showed that PDA was coated on the surface of UHMWPE fibers and then HMDA was successfully grafted on the PDA layers. The excellent mechanical property of UHMWPE fibers had no obvious change. Compared with the pristine UHMWPE fibers, the interfacial shear strength of the PDA coated UHMWPE fibers with the epoxy resin matrix improved by 28.3%, while the IFSS of the HMDA grafted UHMWPE fibers had an increase of 82.7%. Copyright © 2017 John Wiley & Sons, Ltd.     

Using graphene/TiO2 nanocomposite as a new route for preparation of electroconductive,self-cleaning,antibacterial and antifungal cotton fabric without toxicity

A novel and efficient process is reported for fabrication of electroconductive, self-cleaning, antibacterial and antifungal cellulose textiles using a graphene/titanium dioxide nanocomposite. Cotton fabric was loaded with graphene oxide using a simple dipping coating method. The graphene oxide-coated cotton fabrics were then immersed in TiCl₃ aqueous solution as both a reducing agent and a precursor to yield a fabric coated with graphene/titanium dioxide nanocomposite. The crystal phase, morphology, microstructure and other physicochemical properties of the as-prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and UV-Vis reflectance spectroscopy. Electrical resistance, self-cleaning performance, antimicrobial activity and cytotoxicity of treated fabrics were also assessed. The electrical conductivity of the graphene/titanium dioxide nanocomposite-coated fabrics was improved significantly by the presence of graphene on the surface of cotton fabrics. The self-cleaning efficiency of the treated fabrics was tested by degradation of methylene blue in aqueous solution under UV and sunlight irradiations. The results indicated that the decomposition rates of methylene blue were improved by the addition of graphene to the TiO₂ treatment on fabrics. Moreover, the graphene/titanium dioxide nanocomposite-coated cotton samples had negligible toxicity and possessed excellent antimicrobial activity.     

Functionalization of cotton fabrics with rutile TiO<Subscript>2</Subscript> nanoparticles: Applications for superhydrophobic,UV-shielding and self-cleaning properties

The superhydrophobic cotton fabrics were prepared by combining the coating of titanium dioxide (TiO₂) with the subsequent dodecafluoroheptyl-propyl-trimethoxysilane (DFTMS) modification. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements revealed that the nanosized TiO₂ sphere consisted of granular rutile. The TiO₂ layer coated on the cotton altered both the surface roughness for enhancing the hydrophobicity and UV-shielding property. The cotton fabric samples showed excellent water repellency with a water contact angle as high as 162°. The UV-shielding was characterized by UV-vis spectrophotometry, and the results indicated that the fabrics could dramatically reduce the UV radiation. The photocatalytic progress showed that organic stains were successfully degraded by exposure of the stained fabric to UV radiation. Such multifunctional cotton fabrics may have potentials for commercial applications.     

Thermo- and pH-responsive polypropylene microporous membrane prepared by the photoinduced RAFT-mediated graft copolymerization

Thermo- and pH-responsive polypropylene microporous membrane prepared by photoinduced reversible addition–fragmentation chain transfer (RAFT) graft copolymerization of acrylic acid and N-isopropyl acrylamide by using dibenzyltrithiocarbonate as a RAFT agent. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM) were used to characterize the structural and morphological changes on the membrane surface. Results of ATR/FT-IR and XPS clearly indicated that poly(acrylic acid) (PAAc) and poly(N-isopropyl acrylamide) (PNIPAAm) were successfully grafted onto the membrane surface. The grafting chain length of PAAc on the membrane surface increased with the increase of UV irradiation time, and decreased with the increase of the concentration of chain transfer agent. The PAAc grafted membranes containing macro-chain transfer agents, or the living membrane surfaces were further functionalized via surface-initiated block copolymerization with N-isopropyl acrylamide in the presence of free radical initiator, 2,2′-azobisisobutyronitrile. It was found that PNIPAAm can be grafted onto the PAAc grafted membrane surface. The results demonstrated that polymerization of AAc and NIPAAm by the RAFT method could be accomplished under UV irradiation and the process possessing the living character. The PPMMs with PAAc and PNIPAAm grafting chains exhibited both pH- and temperature-dependent permeability to aqueous media.     

聚砜与丙烯酸的紫外光辐射接枝共聚及其表征

在均相溶液体系下,运用紫外光辐射引发合成了聚砜与丙烯酸的接枝共聚物。用化学滴定、漫反射傅立叶变换红外光谱和热分析等技术对接枝聚合物进行了表征。结果表明:丙烯酸被接枝在聚砜链上;光照时间、单体浓度和光引发剂浓度对接枝率均有较大影响。膜表面接触角的研究表明,接枝共聚物膜的亲水性比改性前有所提高。     

Elaboration of nano-structured grafted polymeric surface

The surface grafting of multi-polymeric materials can be achieved by grafting as components such as polymers poly(N-isopropylacrylamide) and/or surfactant molecules (hexatrimethylammonium bromide, polyoxyethylene sorbitan monolaurate). The chosen grafting techniques, i.e. plasma activation followed by coating, allow a large spectrum of functional groups that can be inserted on the surface controlling the surface properties like adhesion, wettability and biocompatibility. The grafted polypropylene surfaces were characterized by contact angle analyses, XPS and AFM analyses. The influence of He plasma activation, of the coating parameters such as concentrations of the various reactive agents are discussed in terms of hydrophilic character, chemical composition and morphologic surface heterogeneity. The plasma pre-activation was shown inevitable for a permanent polymeric grafting. PNIPAM was grafted alone or with a mixture of the surfactant molecules. Depending on the individual proportion of each component, the grafted surfaces are shown homogeneous or composed of small domains of one component leading to a nano-structuration of the grafted surface.     

Mechanical and physico-chemical characterization of cyclodextrin finished polyamide fibers

We present the study of the cyclodextrin (CDs) finishing of polyamide fibers (PA) by means of citric acid (CTR) as crosslinking agent. We observed that the mode of grafting happened by the formation of a crosslinked polymer formed between CTR and CDs. This polymer physically adhered to the fibers network and was resistant to hot water washings. Modified fibers were characterized by evaluating the contact angle with a polar liquid and by studying the hysteresis of damping of PA fibers (Cahn balance) with various grafting rates and by studying the absorptivity of grafted fabrics via the technique of the posed drop (Digidrop^® instrument). Then a mechanical characterization of the PA fabrics grafted with various proportions of CDs was accomplished, by traction and tear tests by using a tensile-test bench Lohmergy. Finally a topographic study of PA grafted surfaces was approached by atomic force microscopy (AFM and LFM; contact and non-contact mode) which permitted to evaluate the roughness and the chemical heterogeneity of the grafted surfaces.     

Polyethylene glycol grafted cotton as phase change polymer

Thermal storage cotton possessing solid–solid phase change properties was prepared by direct grafting of polyethylene glycol (PEG) on cotton fiber/cloth. Attempt has been made to characterize intermediates so that desired grafting could be obtained. The grafting was done by using urethane linkage and the grafted cotton was found to undergo solid–solid phase transition. The modified cotton was characterized by using Fourier transform infrared spectroscopy (FT-IR), ¹³C CPMAS, polarizing optical microscopy, differential scanning calorimetry (DSC) and thermogravimetry respectively. The DSC study revealed quite good storage effect of grafted cotton and the enthalpy of melting was found to be 55–59 J/g with a peak appearing at around 60 °C. During cooling scan, the crystallization peak appeared at around 38 °C. Further, thermogravimetric analysis confirmed good thermal stability up to 300 °C. Appreciable improvement of mechanical properties of cotton has been observed after grafting. The polarizing optical micrograph clearly showed change of morphology after grafting, i.e., the grafted PEG adhering to fiber surface.     

In situ production of silver nanoparticle on cotton fabric and its antimicrobial evaluation

An ecological and viable approach for the in situ forming silver nanoparticles (AgNPs) on cotton fabrics has been used. Silver nanocoated fabric of brownish yellow color (AgNPs, plasmon color) was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). SEM images revealed that the surface of the modified cotton was rougher than that of normal cotton. In addition, SEM images showed the presence of AgNPs on the surface of the treated fabric. Silver mapping and elemental analysis of the silver nanocoated cotton fabric using EDS confirmed the presence of AgNPs in a homogeneous distribution. Also, FTIR spectra of silver nanocoated sample showed more intense and broad peaks with a slight red shift if compared with those of blank sample indicating the binding of AgNPs with cellulose macromolecules. Different coating levels and the impact of repeated washings have been evaluated against different microbial strains by growth inhibition zone. The results of antimicrobial studies reveal that the presence of a low coating level of nanosilver is enough for producing an excellent and durable antimicrobial cotton fabrics.     

Radiation induced graft polymerization of a fluorinated acrylate onto fabric

A fluoride acrylate monomer, 1H,1H,2H,2H-nonafluorohexyl-1-acrylate (denoted as F4), was grafted onto cotton fabric through a simultaneous irradiation induced graft polymerization technique. The grafted cotton fabric (denoted as cotton–F4) is superhydrophobic (SCF) when the degree of grafting (DG) exceeded 10%. The morphology of the cotton fabric was unchanged. In addition, the mechanical properties of the cotton fabric and SCF samples were also studied. The results showed that the decrease in mechanical properties was less than 20%, indicating that the SCF retained good mechanical strength.     

Growth and fire resistance of colloidal silica-polyelectrolyte thin film assemblies

Thin films of colloidal silica were deposited on cotton fibers via layer-by-layer (LbL) assembly in an effort to reduce the flammability of cotton fabric. Negatively charged silica nanoparticles of two different sizes (8 and 27 nm) were paired with either positively charged silica (12 nm) or cationic polyethylenimine (PEI). PEI/silica films were thicker due to better (more uniform) deposition of silica particles that contributed to more than 90% of the film weight. Each coating was evaluated at 10 and 20 bilayers (BL). All coated fabrics retained their weave structure after being exposed to a vertical flame test, while uncoated cotton was completely destroyed. Micro combustion calorimetry confirmed that coated fabrics exhibited a reduced peak heat release rate, by as much as 20% relative to the uncoated control. The 10 BL PEI-8 nm silica recipe was the most effective because the coating is relatively thick and uniform relative to the other systems. Soaking cotton in basic water (pH 10) prior to deposition resulted in better assembly adhesion and flame-retardant behavior. These results demonstrate that LbL assembly is a useful technique for imparting flame retardant properties through conformal coating of complex substrates like cotton fabric.     

Functionalization of cotton fabrics with corona/air RF plasma and colloidal TiO2 nanoparticles

This study discusses the possibility of using a corona discharge at atmospheric pressure and air RF plasma at low pressure for the cotton fibre activation prior to deposition of colloidal TiO₂ nanoparticles in order to enhance antibacterial, UV protective and self-cleaning properties. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of TiO₂ nanoparticles on the surface of cotton fibres. XPS elemental mapping indicated that TiO₂ nanoparticles were more evenly distributed across the surface of untreated and corona pre-treated cotton fabrics in comparison with RF plasma pre-treated fabric. Atomic absorption spectroscopy measurements revealed that the equivalent total content of TiO₂ in the cotton fabrics pre-treated by corona and RF plasma was 31% higher than in the fabric that did not undergo any treatment prior to loading of TiO₂ nanoparticles. In order to achieve maximum bacteria (Gram-negative bacteria Escherichia coli) reduction, untreated cotton fabric had to be loaded with colloidal TiO₂ nanoparticles twice, but only once following corona or RF plasma pre-treatment. Deposition of TiO₂ nanoparticles onto cotton fabrics provided maximum UV protective rating of 50+. Extraordinary photocatalytic activity of TiO₂ nanoparticles deposited onto cotton fabrics was proved by self-cleaning of blueberry juice stains and photodegradation of methylene blue in aqueous solution under UV illumination.     

Introducing carboxyl and aldehyde groups to softwood-derived cellulosic fibers by laccase/TEMPO-catalyzed oxidation

For more cost-effective and/or value-added utilization of cellulosic fibers in pulp and paper industry, fiber engineering is an important concept. Essentially, fibers can be engineered via various mechanical, chemical, and biological processes. In the current study, the combined use of laccase and TEMPO was applied to introduce carboxyl and aldehyde groups to softwood-derived cellulosic fibers (bleached softwood kraft pulp). The process conditions in preparation of the engineered fibers were optimized. Under the conditions studied, the maximum increases in carboxyl and aldehyde contents were 360 % and 225 %, respectively. The effectiveness of the laccase/TEMPO system could be well explained by the reaction cycles in catalytic oxidation pathways. The findings of the current work may provide useful insights into the enzymatic modification of cellulosic fibers for papermaking applications.     

Characterization of N-isopropyl acrylamide/acrylic acid grafted polypropylene nonwoven fabric developed by radiation-induced graft polymerization

Radiation-induced graft copolymerization of N-isopropylacrylamide (NIPAAm) and acrylic acid (AA) mixture was carried out on polypropylene nonwoven fabric to develop a thermosensitive material and has been found to affect the thermal and physical characteristics of fabric. The grafted fabrics with different monomer ratios were characterized by thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), contact angle and atomic force microscopy (AFM). Results of FTIR clearly indicated that poly(acrylic acid) and poly(N-isopropyl acrylamide) were successfully grafted onto the membrane surface. TGA results showed that the thermal stability of PP fabric increased after grafting of NIPAAm/AA. The crystallinity values from DSC and XRD were found to decrease with increase in degree of grafting because of the addition of grafted chains within the noncrystalline region. The decrease in contact angles of the grafted fabric with an increase of the degree of grafting shows that PNIPAAm/PAA exists as the hydrophilic component. The increase in surface roughness after grafting was observed by AFM.     

The Grafting of Per-(2,3,6-O-allyl)-�� Cyclodextrin onto Derivatized Cotton Cellulose via Thermal and Atmospheric Plasma Techniques

In recent years, cyclodextrin applications have been expanding to include textile finishing, providing new and unique functionalities to the fabric substrates. In this work the grafting of Per-(2,3,6-O-allyl)-?? cyclodextrin by plasma and conventional thermofixation methods is described. The fabric substrate was cotton and activated by the surface modification of the fibers by the synthesis of iododeoxycellulose, cellulose peroxide, and a cellulose diazonium salt. Several plasma machines and conventional thermal techniques for fixation were studied. Iododeoxycellulose gave the best results by thermofixation and the in situ mode of the APJeT atmospheric plasma machine. Linoleic, ricinoleic, oleic acids were included in the grafted cyclodextrin fabrics as possible wound healing agents. The cyto-compatibility of the treated samples either included or un-included with fatty acids shows promising results.