Surface modification of polyethylene terephthalate film by CO2 laser‐induced graft copolymerization of acrylamide

Graft copolymerization of acrylamide onto polyethylene terephthalate (PET) using a CO₂ pulsed laser was performed to improve water wettability. After laser irradiation in air, the films were placed in the aqueous solution of monomer and then heated to decompose peroxides formed onto the irradiated PET film. Peroxide density was determined spectrophotometrically by means of the iodide method. The grafted PET surfaces were characterized by attenuated total reflectance infrared spectroscopy, scanning electron microscopy, and contact angle measurements. The electron micrographs showed that the grafting changed the surface morphology of the PET film, which is consistent with the infrared spectra of the grafted films. To evaluate the surface hydrophilicity, water drop contact angle was determined. The contact angle decreased as a result of graft polymerization. It was also found that the hydrophilicity is related to the surface morphology and grafting level. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 401–407, 2000     

Femtosecond‐laser‐assisted wet chemical etching of polymer materials

Polymers are modified by femtosecond‐(fs)‐IR‐laser irradiation under various process parameters. Several sorts of thermoplastic polymer are employed: polymethylmethacrylate (PMMA), fluorinated PMMA, poly‐N‐methyl methacrylimide (PMMI), polystyrol, polycarbonate, polyimide, and polyethylene. After the fs‐laser‐induced modification process, the irradiated area is developed by an aqueous solution of a solvent agent (n‐hexane, benzene, and methylisobutylketone). The surface topography of the fs‐laser‐irradiated area is characterized by stylus‐profilometry before and after the development procedure. Some preliminary explanations are given about the solution mechanism of the fs‐laser‐irradiated polymer region. The experimental results are relevant for the fabrication of three‐dimensional (3D)‐structures in the volume of a transparent polymer material by fs‐laser irradiation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1229–1238, 2006     

Comprehensive study of polymer fiber surface modifications Part 1: high‐fluence UV‐excimer‐laser‐induced structures

Recently, there has been great interest in physico‐chemical surface treatments for modifying polymer surfaces. Ultraviolet (UV)‐excimer‐laser irradiation of polymers is of particular interest. In this study, polyamide was irradiated by a 193 nm excimer laser with a fluence above its ablation threshold (high‐fluence). Morphological changes of the resulting samples were characterized by scanning electron microscopy (SEM) and tapping mode atomic force microscopy (TM‐AFM). Chemical modifications by laser treatment were studied by X‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and chemical force microscopy (CFM). Topographical results indicated that ‘ripple‐like’ structures of micrometer size were formed after laser irradiation. XPS and Tof‐SIMS results showed that bond scission occurred on the polymer surface under the action of high‐fluence. Changes in surface chemical properties of the laser‐irradiated polyamide were supported by CFM experiments. Copyright © 2004 Society of Chemical Industry     

Surface modification of polyethylene by plasma pretreatment and UV‐induced graft polymerization for improvement of antithrombogenicity

The purpose of this study was to enhance blood compatibility of polyethylene (PE) films. Glycidyl methacrylate (GMA) was grafted onto the surface of PE by Ar plasma pretreatment and UV‐induced graft polymerization without photo‐initiator, then heparin was immobilized onto the poly (glycidyl methacrylate) segments. The surface compositions and microstructure of GMA graft polymerized PE films were studied by X‐ray photoelectron spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transfer Infrared (ATR‐FTIR) spectroscopy. It was confirmed that heparin was successfully immobilized onto the surface of PE films by XPS analysis. The antithrombogenicity of the samples was determined by the activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), and plasma recalcification time (PRT) tests and platelet adhesion experiment. Results indicated that the antithrombogenicity of modified PE was improved remarkably. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2014–2018, 2004     

Preparation and high‐temperature behavior of HfC–SiC nanocomposites derived from a non‐oxygen single‐source‐precursor

A single‐source precursor for the preparation of HfC‐SiC ceramics was synthesized via a Grignard reaction using bis(cyclopentadienyl)hafnium(IV) dichloride, trans‐1,4‐dibromo‐2‐butene, and (chloromethyl)trimethylsilane as raw materials. The composition, structure, pyrolysis process and high‐temperature behavior of the precursor were investigated. The results show that the precursor with a backbone comprising Hf–C, Si–C and CH=CH groups exhibits good solubility in common solvents, such as tetrahydrofuran, dimethylbenzene, and chloroform. Pyrolysis of the precursor at 1000°C yielded a microcrystalline HfC phase with a ceramic yield of 63.86 wt%. The pyrolytic products at 1600°C were HfC–SiC nanocomposite ceramics, which exhibited good thermal stability up to 2400°C. The formation of a (Hf,Si)C solid‐solution would be beneficial for densification during the sintering process. The non‐oxygen structure, high ceramic yield, homogeneous composition and excellent high‐temperature behavior of the pyrolytic products make the as‐prepared precursor a promising material for the preparation of high‐performance ultra‐high‐temperature ceramics.     

High temperature surface neutralization process with random copolymers for block copolymer self‐assembly

Hydroxyl terminated poly(styrene‐r ‐methyl methacrylate) (P(S‐r ‐MMA )) random copolymers (RCPs ), with molecular weight (M _n) spanning from 1700 to 69 000 g mol^?1 and equal styrene unit content, were grafted at different temperatures onto a silicon oxide surface and subsequently used to study the orientation of nanodomains with respect to the substrate, in cylinder forming polystyrene‐b ‐poly(methyl methacrylate) (PS ‐b ‐PMMA ) block copolymer thin films. When the grafting temperature increases from 250 to 310 °C, a substantial increase in the grafting rate is observed. In addition, an increase in the surface neutralization efficiency occurs thus resulting in an increase in the robustness of the surface neutralization step. These data revealed that the neutralization of the substrate is the result of a complex interplay between RCP film characteristics and underlying substrate properties that can be finely tuned by properly adjusting the temperature of the grafting process. © 2016 Society of Chemical Industry     

Isotactic polypropylene hollow microfibers prepared by CO2 laser‐thinning

An isotactic polypropylene hollow microfiber was continuously produced by using a carbon dioxide (CO₂) laser‐thinning method. To prepare the hollow microfiber continuously, the apparatus used for the thinning of the solid fiber was improved so that the laser can circularly irradiate to the hollow fiber. Original hollow fiber with an outside diameter (OD) of 450 μm and an internal diameter (ID) of 250 μm was spun by using a melt spinning machine with a specially designed spinneret to produce the hollow fiber. An as‐spun hollow fiber was laser‐heated under various conditions, and the OD and the ID decreased with increasing the winding speed. For example, when the hollow microfiber obtained by irradiating the CO₂ laser to the original hollow fiber supplied at 0.30 m min^?1 was wound up at 800 m min^?1, the obtained hollow microfiber had an OD of 6.3 μm and an ID of 2.2 μm. The draw ratio calculated from the supplying and the winding speeds was 2667‐fold. The hollow microfibers obtained under various conditions had the hollowness in the range of 20–30%. The wide‐angle X‐ray diffraction patterns of the hollow microfibers showed the existence of the highly oriented crystallites. Further, the OD and ID decreased, and the hollowness increased by drawing hollow microfiber obtained with the laser‐thinning. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2600–2607, 2006     

Plastic identification and comparison by multivariate techniques with laser‐induced breakdown spectroscopy

The classification of plastics is very important in the recycling industry. A quick online classification allows the installation of the equipment in this line of work. Whether qualitative or quantitative analysis, the basic component of any laser‐induced breakdown spectroscopy (LIBS) measurement is the emission spectrum recorder from single plasma. Each fire of the laser atomizes a portion of the sample in the pulse focal volume and produces plasma that excites and re‐excites the atoms to emit light. The plasma light is collected and recorded in an ensuing measurement. In this sense, the LIBS technique offers all possible advantages: speed, the possibility of online analysis, nondestructive analysis, and so on. In this article, we discuss details related to the analysis of the emission spectrum. The plastics used in this study were low‐density polyethylene (PE), high‐density PE, polypropylene, polystyrene, and poly(ethylene terephthalate). Hierarchical cluster analysis was proven to be the best method because the four polymers could be divided into two clusters, which allowed their identification and classification in a fast and easy way that could be carried out with commercial software and could be implanted online in a recycling factory, as conventional data analysis techniques are limited to the qualitative identification and calculation of elemental abundances. Principal component analysis on LIBS spectra can be used to better describe the chemical variations in the samples and to extract a greater understanding of the chemical structure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Surface modification of poly(ether sulfone) ultrafiltration membranes by low‐temperature plasma‐induced graft polymerization

Low‐temperature helium plasma treatment followed by grafting of N‐vinyl‐2‐pyrrolidone (NVP) onto poly(ether sulfone) (PES) ultrafiltration (UF) membranes was used to modify commercial PES membranes. Helium plasma treatment alone and post‐NVP grafting substantially increased the surface hydrophilicity compared with the unmodified virgin PES membranes. The degree of modification was adjusted by plasma treatment time and polymerization conditions (temperature, NVP concentration, and graft density). The NVP‐grafted PES surfaces were characterized by Fourier transform infrared attenuated total reflection spectroscopy and electron spectroscopy for chemical analysis. Plasma treatment roughened the membrane as measured by atomic‐force microscopy. Also, using a filtration protocol to simulate protein fouling and cleaning potential, the surface modified membranes were notably less susceptible to BSA fouling than the virgin PES membrane or a commercial low‐protein binding PES membrane. In addition, the modified membranes were easier to clean and required little caustic to recover permeation flux. The absolute and relative permeation flux values were quite similar for the plasma‐treated and NVP‐grafted membranes and notably higher than the virgin membrane. The main difference being the expected long‐term instability of the plasma treated as compared with the NVP‐grafted membranes. These results provide a foundation for using low‐temperature plasma‐induced grafting on PES with a variety of other molecules, including other hydrophilic monomers besides NVP, charged or hydrophobic molecules, binding domains, and biologically active molecules such as enzymes and ribozymes. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1699–1711, 1999     

Surface modification of polysulfone membranes by low‐temperature plasma–graft poly(ethylene glycol) onto polysulfone membranes

A novel and general method of modifying hydrophobic polysulfone (PSF) to produce highly hydrophilic surfaces was developed. This method is the low‐temperature plasma technique. Graft polymer‐modified surfaces were characterized with the help of Fourier transform infrared attenuated total reflection (FTIR–ATR) and X‐ray photoelectron spectroscopy (XPS). Study results demonstrated that poly(ethylene glycol) (PEG) could be grafted onto the PSF membrane surface by low‐temperature plasma. The hydrophilic character of the modified surfaces was increased in comparison with that of the parent membrane. The contact angle for a modified PSF membrane was reduced apparently. We analyzed the effectiveness of this approach as a function of plasma operating variables including plasma treatment power and treatment time. Hence, plasma‐induced graft polymer modification of membranes can be used to adjust membrane performance by simultaneously controlling the surface hydrophilicity and hemocompatibility. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 979–985, 2000     

Chiral separation of mandelic acid by temperature‐induced aqueous two‐phase system

BACKGROUND: R‐mandelic acid is an important chiral pharmaceutical intermediate, which is commonly obtained by biotransformation. This work has focused on using novel chiral recognition technology, aqueous two‐phase extraction, for the chiral separation of mandelic acid. RESULTS: The copper (II) formed a 2:1 complex with β‐CD in an alkaline solution, which was isolated from solution by the addition of ethanol. The complex structure was characterized by IR and UV spectroscopy. The chiral recognition system was established by adding Cu₂‐β‐CD into the triton‐114 aqueous two‐phase extraction system, which preferentially recognizes the (R)‐enantiomer rather than the (S)‐enantiomer. Factors affecting the extraction mechanism were analyzed, namely the concentration of Cu₂‐β‐CD and tritonX‐114, the types of salts, pH, and temperature. It was found that the concentration of Cu₂‐β‐CD and temperature were the most important influencing factors for chiral separation of mandedlic acid. The experimental results showed that the ee values increased with pH and concentration of trition‐114, and the maximum ee was 67.91%. The addition of inorganic salt had a strong influence on ee, which decreased when salt was added into the aqueous two‐phase extraction system. CONCLUSION: A novel chiral recognition technology ‐ aqueous two phase extraction is reported in this paper.The tritonX‐114 aqueous two phase system have a good recognition ability for mandelic acid. Copyright © 2012 Society of Chemical Industry     

Facile one‐step high‐temperature spray pyrolysis route toward metal carbide nanopowders

Fine ultrahigh‐temperature ceramic (UHTC) powders have found very important applications in many fields. In this work, a facile high‐temperature spray pyrolysis (HTSP) approach is implemented for the synthesis of HfC and TaC UHTC nanopowders starting from organic solvent (e.g., ethanol or 1‐pentanol) solutions of metal precursors (HfCl₄ or TaCl₅). It is proposed that, during HTSP, the precursor solution droplets would continuously undergo rapid drying, thermolysis (i.e., removal of low molecular weight species such as H₂, H₂O, and CO), and finally in situ carbothermal reduction (CTR) process to give rise to metal carbide nanopowders. The as‐obtained materials are shown by SEM as uniform and separated nanoparticles (~90 nm), whereas TEM reveals the carbide (e.g., HfC) nanoparticles are actually even smaller (~10‐20 nm) and embedded in amorphous carbon from excess solvent decomposition. It is found that among different processing parameters, the organic solvent used and the metal precursor concentration could largely influence the formation of metal carbide. In addition, lower HTSP temperatures (≤~1500°C for HfC) only lead to oxide‐carbon mixtures while higher temperatures (≥~1650°C) promote carbide formation. The HTSP method developed in this work is simple, low‐cost and efficient, and could potentially be optimized further for future large‐scale manufacturing of ultrafine UHTC nanopowders.     

Time‐resolved measurements of pyrolysis and combustion products of PMMA

We studied transient chemical speciation during high‐temperature solid material pyrolysis and combustion in air. Our objective was to develop a database of chemical burn signatures. The material tested was the thermoplastic PMMA. Material samples were heated in an infrared furnace until they pyrolyzed, ignited, and combusted in air. Time‐resolved quantitative measurements of the exhaust species CO₂, O₂, hydrocarbons, and CO along with exhaust gas temperature were obtained. Two categories of experiments were conducted: (1) pyrolysis tests in which there was no combustion; (2) combustion tests with chemical reaction and heat release. During heating, the sample underwent numerous processes that appear as diagnostic sequences. In the pyrolysis tests, as the furnace temperature was raised, the CO and hydrocarbon (HC) signals underwent transition from one peak to two peaks. In the combustion tests, spontaneous ignition occurred at higher test temperatures as evidenced by an exothermic reaction reported by the thermocouples, leading to three‐peak CO and HC profiles. The measured O₂/CO₂ ratio of 1.3 ± 0.1 agreed with stoichiometric methyl‐methacrylate monomer decomposition. Calculations of the power output using two independent methods supported (1) that combustion was experimentally observed in the furnace, and (2) the accuracy of the combustion gas analysis. Copyright © 2012 John Wiley & Sons, Ltd.     

Micropatterning of poly(p‐phenylene vinylene) by femtosecond laser induced forward transfer

Conjugated polymers are important materials for optical applications, among which poly(p‐phenylene vinylene) (PPV) has a major role due to its applicability in sensors, organic light‐emitting diodes and large area displays. Despite advances on the synthesis of PPV‐based polymers and the improvements of their properties, its printing process, in particular involving the solid phase, remains unsuitable for the development of electro‐optical microcircuits. This paper demonstrates the printing of PPV from the solid phase in 2D micropatterns. Such an achievement was performed using laser induced forward transfer with femtosecond pulses, which allows area‐selective deposition within reduced scales as thin as ca 100 nm and 5 µm wide. Raman, fluorescence and electrochemical impedance spectroscopies confirm that the printed PPV micropatterns have the same structure, emission spectrum and conductivity as the target material, revealing the conservation of their original properties even after laser irradiation. The printing process was carried out using PPV films, overcoming the insolubility issue of this material. The optical and electrical characterization of the transferred PPV demonstrates the potential of this method for the patterning of electro‐optical microdevices, since luminescence and electrical conductivity were preserved. © 2018 Society of Chemical Industry     

Comprehensive study of polymer fiber surface modifications Part 2: low‐temperature oxygen‐plasma treatment

Polyamide fibers were treated with a low‐temperature oxygen plasma and the effects on the morphology, chemistry and crystallinity of the material were studied. Topographical results illustrate that changes in the surface morphology of the oxygen‐plasma‐treated polyamide correlate well with the discharge power and treatment time. The effects can be categorized into three groups: surface cleaning resulting in a smoother surface, surface etching with formation of ‘ripple‐like’ structures of sub‐micrometer size, and surface melting with down grading of the material. Chemical studies show that the surface oxygen content of the polyamide increases after oxygen‐plasma treatment. The latter induces the formation of many hydroxyl and carboxylic acid functional groups. These groups mainly replace the hydrocarbon or carbonyl groups in the polyamide. Differential scanning calorimetry (DSC) results indicate that a short treatment time does not affect the degree of crystallinity of the polyamide material, while a long plasma‐treatment time slightly increases the crystallized fraction. Copyright © 2004 Society of Chemical Industry     

Novel rapid‐cure adhesives for low temperature using thiirane compound

We investigated improvement of workability (viscosity), storage stability, and curing ability of thiirane resin for adhesive applications. The viscosity of bisphenol‐F thiirane resin was lower than that of bisphenol‐A thiirane resin, especially at low temperatures, thus improving ease of handling. Addition of diphenyl decyl phosphite improved its storage stability to a level similar to that of bisphenol‐A epoxy resin. The curing of bisphenol‐F thiirane resin increased three times faster by adding 2,4,6‐tris(dimethylaminomethyl)phenol (DMP‐30) as a tertiary amine. In applications of this new thiirane resin as civil and architectural adhesives, a superior curing ability at low temperature was attained. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2953–2957, 2001     

Surface modification of polypropylene membrane by low‐temperature plasma treatment

Microporous polypropylene membranes were low temperature plasma treated with acrylic acid and allylamine. Parameters of plasma treatment were examined and optimized for the enhancement of membrane performance properties. Excess power damaged the membrane surface and excess monomer flow rate increased the reactor pressure to interfere with the glow discharge. Longer plasma treatment time resulted in even more plasma coating and micropore blocking. The contact angle with water decreased and wettabilities increased with the increase of plasma treatment time. Deposition of the plasma polymer on the membrane surface was confirmed by FTIR/ATR spectra of the treated surface. In determining the flux, the hydrophilicity of the surface played a role as important as that of the micropore size. Adequate plasma treatment could enhance both water flux and solute removal efficiency. Results from the BSA (bovine serum albumin) solution test confirmed that fouling was greatly reduced after the plasma treatment. The BSA solution flux through the plasma‐treated membranes depended on pH, whereas pH variation had no serious effects on the untreated membrane. Modification of the surface charge by the plasma treatment should exert a substantial influence on the adsorption and removal of BSA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1555–1566, 2001     

Characterization of acrylic acid‐grafted PP membranes prepared by plasma‐induced graft polymerization

Acrylic acid (AA)‐g‐polypropylene (PP) membranes were prepared by grafting AA on to a microporous PP membrane via plasma‐induced graft polymerization. The grafting of AA to the PP membrane was investigated using Fourier transform infrared spectroscopy (FTIR). Pore‐filling of the membranes was confirmed by field emission‐scanning electron microscopy (FESEM) and energy dispersing X‐ray (EDX). Ion exchange capacity (IEC), membrane electric resistance, transport number and water content were measured and analyzed as a function of grafting reaction time. The prepared AA‐g‐PP membranes showed moderate electrochemical properties as a cation‐exchange membrane. In particular, membranes with a degree of grafting of 155% showed good electrical properties, with an IEC of 2.77 mmol/g dry membrane, an electric resistance of 0.4 Ω cm² and a transport number of 0.96. Chronopotentiometric measurements indicated that AA‐g‐PP membranes, with a high IEC had a sufficient conducting region in the membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Surface modification of MWNTs with BA‐MMA‐GMA terpolymer by single‐step grafting technique

In this article, a facile strategy was developed to prepare BA‐MMA‐GMA/MWNTs (multiwalled carbon nanotubes) hybrid nanoparticles as nanofillers in rubber by single‐step grafting technique. First, a new macromolecular surface modifier butyl acrylate (BA)‐α‐methyl methacrylate(MMA)‐glycidyl methacrylate (GMA) terpolymer was synthesized via radical copolymerization. Afterward, this terpolymer modifier was covalently grafted onto the surface of crude MWNTs by single‐step grafting technique. The structure, surface properties, and thermal stability of modified MWNTs were systematically investigated by FTIR, TGA, and TEM. FTIR results showed that BA‐MMA‐GMA terpolymer was successfully grafted onto the surface of MWNTs. TGA indicated that the optimum mass fraction of macromolecular modifier coated on the surface of MWNTs was 9 wt %. TEM images revealed that an organic coating layer was formed and the modified MWNTs showed good dispersibility in acetone. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011