Surface Properties Of Fibers Research Articles

Dry etching plasma applied to fique fibers: influence on their mechanical properties and surface appearance

Plasma is a novel technique used in order to modify the surface properties of fibers used as a reinforced of polymeric composites. In this way, this paper shows the results of a research aimed to understand the effect of the dry etching plasma on natural fique fibers. Using different exposure times, the influence of plasma treatments on the tensile strength and surface appearance were investigated. Results showed that natural fibers could be effectively plasma treated without decreasing the strength and with significant modification of their surface appearance.

Mechanically-induced dimensional extensibility of fibers towards tough fiber networks

The beneficial effect of materials with high aspect ratio as composite reinforcement has prompted continuous interest towards cellulosic fibers. Besides providing stiffness, fibers can potentially contribute to composite extensibility. While mechanical treatments are typically used to adjust the physical and surface properties of fibers, less is known about ensuing effects on their extensibility and that of associated networks. Fiber network dimensional extensibility of 16% was achieved by processing the precursor aqueous fiber dispersions following a simple mechanical treatment with a judicious combination of low (PFI refining) and high concentrations and temperatures (Wing defibrator). Consequently, deformation of fibers and increased inter-fiber bonding resulted in a three-fold increase in strength to rupture of the fiber network leading to the structures with unprecedented toughness.

Hydrophobic cellulose fibers via ATRP and their performance in the removal of pyrene from water

ABSTRACTIn the present work, cellulose fibers were modified by grafting with poly(lauryl acrylate) and poly(octadecyl acrylate). The grafted materials were prepared by polymerization of the corresponding monomers via surface initiated atom transfer radical polymerization, starting from cellulose papers previously modified with 2‐bromoisobutyryl groups. The polymerizations were carried out in the presence of ethyl‐2‐bromoisobutyrate, as a sacrificial initiator, added to control the molecular weight of the anchored segments, and polymerization kinetics. The grafting of both polymers was confirmed by infrared spectroscopy and elemental analysis. The effect of grafting these polymers on the thermal stability, morphology, and surface properties of cellulose fibers was studied using thermogravimetric analysis, scanning electron microscopy, and measuring water contact angle, respectively. The results reveal that grafting poly(lauryl acrylate) and poly(octadecyl acrylate) to cellulose confers the filter paper a hydrophobic character, and increases its affinity with pyrene, allowing the removal of this pollutant from water. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44482.

Impact of surface plasma treatment on the performance of PET fiber reinforcement in cementitious composites

The purpose of this study is to demonstrate the influence of plasma treatment on the surface properties of PET fibers used as micro reinforcement in cementitious composites. The stress transfer across cracks that untreated fibers are able to accomplish can be enhanced via plasma treatment. The increase in surface roughness and the activation of polar groups result in the reduction of surface energy as observed during wetting angle measurements. The improvement in adhesion between primary (non-recycled) fibers and the surrounding matrix brought about a more pronounced strain hardening of the specimens tested in four-point bending. Plasma treatment of thinner fibers from recycled PET led to a lower capacity for transferring tensile stresses due to the reduced cross-sectional area of the fibers. The considerable bridging force provided by the plasma treated primary PET fibers resulted in the prevention of excessive and abrupt cracking, and limited crack openings.

Effect of fiber length and surface characteristics on the mechanical properties of cementitious composites

A disadvantage of conventional concrete is its low flexural strength and ductility in tension. Cracks form when the tensile strength of conventional concrete, which is limited, is exceeded due to various actions (loads, restrained shrinkage, temperature variation, chemical reactivity) accentuating the effects of carbonation and chloride-induced corrosion of concrete and reinforcement, thereby compromising the residual service life and strength of concrete members. Addition of fibers to enhance the flexural capacity of structural materials through crack control is an ancient idea that is now spearheading novel developments in the area of high-performance cementitious materials. Currently, the state of the art is focused on the use of synthetic fibers in self-consolidating, fine-aggregate cementitious mixes that demonstrate strain hardening properties in tension, outstanding crack control and improved durability performance. This paper deals with experimental characterization of the performance of a material of this class, reinforced with PVA fibers (polyvinyl alcohol with original hydrophilic surface properties). Parameter of study is the length of the fibers as well as the fiber surface properties which are chemically modified through pertinent surfactants. The parametric study compares the mechanical response of FRC to that of plain (unreinforced) cementitious material of the same composition, through tests of material samples in uniaxial compression, extension, splitting and flexure.

Tubing-Electrospinning: A One-Step Process for Fabricating Fibrous Matrices with Spatial, Chemical, and Mechanical Gradients.

Guiding newly generated tissues in a gradient pattern, thereby precisely mimicking inherent tissue morphology and subsequently arranging the intimate networks between adjacent tissues, is essential to raise the technical levels of tissue engineering and facilitate its transition into the clinic. In this study, a straightforward electrospinning method (the tubing-electrospinning technique) was developed to create fibrous matrices readily with diverse gradient patterns and to induce patterned cellular responses. Gradient fibrous matrices can be produced simply by installing a series of polymer-containing lengths of tubing into an electrospinning circuit and sequentially processing polymers without a time lag. The loading of polymer samples with different characteristics, including concentration, wettability, and mechanical properties, into the tubing system enabled unique features in fibrous matrices, such as longitudinal gradients in fiber density, surface properties, and mechanical stiffness. The resulting fibrous gradients were shown to arrange cellular migration and residence in a gradient manner, thereby offering efficient cues to mediate patterned tissue formation. The one-step process using tubing-electrospinning apparatus can be used without significant modifications regardless of the type of fibrous gradient. Hence, the tubing-electrospinning system can serve as a platform that can be readily used by a wide-range of users to induce patterned tissue formation in a gradient manner, which will ultimately improve the functionality of tissue engineering scaffolds.

Characteristics of high yield pulp fibers by xylanase treatment

The effects of xylanase treatment on the fiber surface properties of high yield pulp (chemithermomechanical pulp, alkaline peroxide mechanical pulp, and bleached chemithermomechanical pulp) were studied. Fibers surface composition and surface structure were investigated by X-ray photoelectron spectroscopy and scanning electron microscopy, respectively. The former demonstrated an increase in the atomic oxygen to carbon ratio, a decrease in the lignin content, and variation in the C1s on the fiber surface of enzymatically treated samples. An enrichment of a large proportion of open and fibrillated fibers was visualized by the latter, resulting in an improvement in the pulp’s physical strength-related properties. Surface modification using enzymatic treatments allow for improved fiber surface properties to obtain new products through sustainable technologies.

Surface modification of electrospun fibres for biomedical applications: A focus on radical polymerization methods.

The development of electrospun ultrafine fibres from biodegradable and biocompatible polymers has created exciting opportunities for biomedical applications. Fibre meshes with high surface area, suitable porosity and stiffness have been produced. Despite desirable structural and topographical properties, for most synthetic and some naturally occurring materials, the nature of the fibre surface chemistry has inhibited development. Hydrophobicity, undesirable non-specific protein adsorption and bacterial attachment and growth, coupled with a lack of surface functionality in many cases and an incomplete understanding of the myriad of interactions between cells and extracellular matrix (ECM) proteins have impeded the application of these systems. Chemical and physical treatments have been applied in order to modify or control the surface properties of electrospun fibres, with some success. Chemical modification using controlled radical polymerization, referred to here as reversible-deactivation radical polymerization (RDRP), has successfully introduced advanced surface functionality in some fibre systems. Atom transfer radical polymerization (ATRP) and reversible addition fragmentation chain transfer (RAFT) are the most widely investigated techniques. This review analyses the practical applications of electrospinning for the fabrication of high quality ultrafine fibres and evaluates the techniques available for the surface modification of electrospun ultrafine fibres and includes a detailed focus on RDRP approaches.

Influence of microwave plasma treatment on the surface properties of carbon fibers and their adhesion in a polypropylene matrix

A commercially available carbon fiber (CF) with an epoxy-based sizing (EP-sized CF) and an unsized CF have been plasma treated to study the effect on the fiber-matrix adhesion towards a polypropylene matrix. The EP-sized fiber was chosen because of its predictable low adhesion in a polypropylene (PP) matrix. The fibers have been modified using a microwave low-pressure O2/CO2/N2-gas plasma source (Cyrannus®) developed at IWS in a batch process. One aim of this study was the evaluation of parameters using high energies and short time periods in the plasma chamber to see the effect on mechanical performance of CF. These results will be the fundamental work for a planned continuous plasma modification line. The CF surface was characterized by determining the surface energies, single fiber tensile strength and XPS analysis. The adhesion behavior before and after plasma treatment was studied by single fiber pull-out test (SFPO) and scanning electron microscopy (SEM). It was shown that the CO2- and O2-plasma increases the number of functional groups on the fiber surface during short time plasma treatment of 30 s. Carboxylic groups on the unsized CF surface resulting from O2-plasma treatment lead to an enhanced fiber-matrix adhesion, whereas the fiber strength was merely reduced.

Effects of different plasma treatments of short fibers on the mechanical properties of polypropylene‐wood composites

In this work, a custom‐made reactor was developed to treat batches of short wood fibers with plasma. Three different plasma gases were tested: air, methane (CH4) and sulfur hexafluoride (SF6). The latter showed very promising results and was therefore used to prepare additional samples to determine the effects of plasma treatment and conditions on the wood fiber surface properties as well as the adhesion in a polypropylene matrix. As a result, composites made out of fibers plasma treated for 40 min at 60 W demonstrated an increase in the elastic modulus of more than 25%. Scanning electron microscope micrographs of the composites’ fracture surfaces indicated stronger interactions between treated fibers and the matrix. The incorporation of fluorine on treated fiber surfaces, mostly in covalent bonds with carbon, was clearly observed and analyzed by X‐ray photoelectron spectroscopy. The water contact angle on wood specimens treated under similar conditions displayed hydrophobic to superhydrophobic behavior, with contact angles exceeding 130°. POLYM. COMPOS., 39:1468–1479, 2018. © 2016 Society of Plastics Engineers

Using bulk properties of UV-polymerized thin layers for fiber modification

The surface properties of fibers can be regarded as instrumental toward innovative functional textiles as applied in many high-end industries. Accordingly, not only the modification of surface chemistry, but also of the physical and morphological properties is an important objective in modern materials science and technology. Besides other powerful chemical and physical techniques, UV-induced graft copolymerization and photopolymerization are interesting ways to improve or introduce surface functionalities of the fiber. While the majority of reported work focused on the surface of the deposited thin layer itself and its potential effect on – for example, wettability, adhesion, protein adsorption and microbial activity, this paper reviews earlier studies by the authors which were devoted to bulk properties of these thin, less than 500-nm thick layers and the resulting effect on fiber properties. One major factor is the high and controllable cross-linking of polymerized layers, which affects mechanical, thermal and chemical stability. This results in interesting applications as thin barrier coating in view of improved fiber stability in critical environments and stress conditions, examples of which are reported in this paper. A recent observation is the effect of the controlled cross-linking on the mobility of monomers and electrical charges in the thin layer, which could open an avenue toward thin-layer capacitors and energy storage on textiles.

Interactions between Surfactants in Solution and Electrospun Protein Fibers: Effects on Release Behavior and Fiber Properties.

Intermolecular interaction phenomena occurring between endogenous compounds, such as proteins and bile salts, and electrospun compounds are so far unreported, despite the exposure of fibers to such biorelevant compounds when applied for biomedical purposes, e.g., tissue engineering, wound healing, and drug delivery. In the present study, we present a systematic investigation of how surfactants and proteins, as physiologically relevant components, interact with insulin-loaded fish sarcoplasmic protein (FSP) electrospun fibers (FSP-Ins fibers) in solution and thereby affect fiber properties such as accessible surface hydrophilicity, physical stability, and release characteristics of an encapsulated drug. Interactions between insulin-loaded protein fibers and five anionic surfactants (sodium taurocholate, sodium taurodeoxycholate, sodium glycocholate, sodium glycodeoxycholate, and sodium dodecyl sulfate), a cationic surfactant (benzalkonium chloride), and a neutral surfactant (Triton X-100) were studied. The anionic surfactants increased the insulin release in a concentration-dependent manner, whereas the neutral surfactant had no significant effect on the release. Interestingly, only minute amounts of insulin were released from the fibers when benzalkonium chloride was present. The FSP-Ins fibers appeared dense after incubation with this cationic surfactant, whereas high fiber porosity was observed after incubation with anionic or neutral surfactants. Contact angle measurements and staining with the hydrophobic dye 8-anilino-1-naphthalenesulfonic acid indicated that the FSP-Ins fibers were hydrophobic, and showed that the fiber surface properties were affected differently by the surfactants. Bovine serum albumin also affected insulin release in vitro, indicating that also proteins may affect the fiber performance in an in vivo setting.

Investigations of plasma induced effects on the surface properties of lignocellulosic natural coir fibres

The development of lignocellulosic natural-fibre-reinforced polymers composites are constrained by two limitations: the upper temperature at which the fibre can be processed and the significant differences between the surface energy of the fibre and the polymer matrix. Since the fibres and matrices are chemically different, strong adhesion at their interface is needed for the effective transfer of stress and bond distribution throughout the interface. The present study investigated the plasma induced effects on the surface properties of natural coir fibres. Weakly ionized oxygen plasma was created in two different discharge chambers by an inductively coupled radiofrequency (RF) discharge. The water absorption studies showed an increase of water sorption from 39% to 100%. The morphological study using scanning electron microscopy (SEM) analysis also confirmed the surface changes which were observed after the plasma treatment. The topographic measurements and phase imaging done using atomic force microscopy (AFM) indicated difference in topographic features and etching of coir wall, which points to the removal of the first layer of coir fibre. X-ray photoelectron spectroscopy (XPS) analysis revealed that the oxygen content measured for samples treated at 50Pa increased from initial 18% to about 32%.

Preparation of Graphene Oxide Coatings onto Carbon Fibers by Electrophoretic Deposition for Enhancing Interfacial Strength in Carbon Fiber Composites

Graphene oxide (GO) were utilized to improve the interfacial performance of carbon fiber (CF) and epoxy resin. An effective way to prepare graphene oxide/carbon fiber hybrid fiber was proposed by the treatment with hydrogen peroxide and concentrated nitric acid combined with electrophoretic deposition process. A characterization of the fiber surface properties was done before and after coating (surface morphologies, surface chemistry, and surface energy). Results showed that a uniform and thick graphene oxide films were tightly attached on the surface of carbon fiber. Moreover, surface wettability of carbon fibers to epoxy resin is significant improved by enhanced surface free energy due to the deposition of GO. Meanwhile, the introduction of GO in the carbon fiber/epoxy resin composites results in a 55.6% enhancement in the interlaminar shear strength, measured by short beam shear tests. Such a fabrication process is simple and effective, without complex chemical reactions and long processing time, and can be a continuous one for industrial scale.

Surface properties and fibre-matrix adhesion of man-made cellulose epoxy composites – Influence on impact properties

Previously conducted studies showed that UD regenerated cellulose fibre-reinforced thermoset composites can obtain specific Charpy impact strength values in the range of glass fibre reinforced composites. Composites of two different viscose fibre types, each with and without an oily avivage, were investigated. Despite similar mechanical properties of the fibres the impact strength of the CR fibre composites was about twice as high as that of the standard fibre composites.To reveal a possible explanation for this effect the fibre surface properties were investigated more closely. AFM measurements showed no differences in fibre surface topologies. However the physico–chemical properties of the fibre types differ. IGC measurements showed that the standard Cordenka fibre without avivage (“std wo a.”) possesses a slightly higher specific surface energy and base number (Kb) than the CR fibres without avivage (“CR wo a.”) resulting in a better adhesion to the highly polar epoxy. This is also shown by the pair specific interaction parameters (Isp) and the work of adhesion. Both are clearly higher for the epoxy – “std wo a.” pair. Accordingly the measured fibre pull-out lengths of the CR fibres are one order of magnitude higher than of the std suggesting a weaker interfacial shear strength between the CR fibres and epoxy. Within the same fibre type the samples without avivage show longer pull-out lengths. As a weaker fibre-matrix adhesion causes stronger crack deflection and energy dissipation these results correspond well with the previously measured Charpy impact strengths.

Morpho-chemical characterization and surface properties of carcinogenic zeolite fibers

Erionite belonging to the zeolite family is a human health-hazard, since it was demonstrated to be carcinogenic. Conversely, offretite family zeolites were suspected carcinogenic. Mineralogical, morphological, chemical, and surface characterizations were performed on two erionites (GF1, MD8) and one offretite (BV12) fibrous samples and, for comparison, one scolecite (SC1) sample. The specific surface area analysis indicated a larger availability of surface sites for the adsorption onto GF1, while SC1 shows the lowest one and the presence of large pores in the poorly fibrous zeolite aggregates. Selected spin probes revealed a high adsorption capacity of GF1 compared to the other zeolites, but the polar/charged interacting sites were well distributed, intercalated by less polar sites (Si–O–Si). MD8 surface is less homogeneous and the polar/charged sites are more interacting and closer to each other compared to GF1. The interacting ability of BV12 surface is much lower than that found for GF1 and MD8 and the probes are trapped in small pores into the fibrous aggregates. In comparison with the other zeolites, the non-carcinogenic SC1 shows a poor interacting ability and a lower surface polarity. These results helped to clarify the chemical properties and the surface interacting ability of these zeolite fibers which may be related to their carcinogenicity.

Enhanced surface free energy of polyimide fibers by alkali treatment and its interfacial adhesion behavior to epoxy resins

In this article, polyimide (PI) fibers were modified by alkali treatment, and PI fiber-reinforced epoxy composites were fabricated. The effects of different alkali treatment times on the surface properties of the PI fibers and the adhesion behaviors of PI fiber/epoxy composites were studied. The surface morphologies, chemical compositions, mechanical properties, and surface free energy of the PI fibers were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, single-fiber tensile strength analysis, and dynamic contact angle analysis, respectively. The results show that alkali treatment plays an important role in the improvement of the surface free energy and the wettability of PI fibers. We also found that, after the 3 min, 30 °C, 20 wt% NaOH solution treatment, the fibers possessed good mechanical properties and surface activities, and the interlaminar shear strength of the composites increased to 64.52 MPa, indicating good interfacial adhesion properties.

Strength of hydroentangled fabrics manufactured from photo-irradiated poly para-phenylene terephthalamide (PPTA) fibres

Photo-irradiation of poly para-phenylene terephthalamide (PPTA) fibre is normally associated with deterioration of physical properties. Nonwoven fabrics produced from 100% photo-irradiated PPTA fibres might therefore be expected to yield fabrics with poorer mechanical properties compared to those produced from non-irradiated fibres. To test this hypothesis, the bursting strength of hydroentangled fabrics manufactured from photo-irradiated PPTA fibres was explored. Prior to fabric manufacture, virgin PPTA staple fibres were photo-irradiated under controlled lighting conditions (xenon short arc lamp with a luminous flux of 13,000 lm) for 0, 5, 10, 20, 40, 60 and 100 h. The photo-irradiated fibres were then hydroentangled to produce nonwoven fabrics. Photo-irradiation exposure of PPTA fibre up to 30 MJ m−2 was not found to be detrimental to fabric bursting strength and at irradiation energies of 5–10 MJ m−2 a small, but statistically significant increase in fabric bursting strength was observed compared to fabrics manufactured from non-irradiated fibre. This may be linked to a change in the surface and skin properties of the PPTA photo-irradiated fibres identified by atomic force microscopy (AFM) following photo-irradiation.

Influence of chemical surface treatment of basalt fibers on interlaminar shear strength and fracture toughness of epoxy-based composites

In our study, the effect of chemically treated basalt fibers on the mechanical interfacial properties of basalt fibers reinforced epoxy composites was investigated. The surface properties of the basalt fibers were determined by Fourier Transform Infrared (FT-IR) spectroscopy. The surface structure of the basalt fibers was analyzed Atomic Force Microscopy (AFM). The acid and alkali chemical treatments led to significant changes in the surface characteristics of the fibers. The chemically treated fibers improved the mechanical interfacial properties, interlaminar shear strength (ILSS) and fracture toughness (KIC) of the composites. Composites treated with H2SO4 had higher values of ILSS and KIC than the KOH-treated composites. These results are attributed to the improvement of interfacial bonding strength, which was caused by an increase of the surface roughness of basalt fibers.

Modification of the cellulosic component of hemp fibers using sulfonic acid derivatives: Surface and thermal characterization

The aim of this study was to characterize the surface, morphological, and thermal properties of hemp fibers treated with two commercially available, inexpensive, and water soluble sulfonic acid derivatives. Specifically, the cellulosic component of the fibers were targeted, because cellulose is not easily removed during chemical treatment. These acids have the potential to selectively transform the surfaces of natural fibers for composite applications. The proposed method proceeds in the absence of conventional organic solvents and high reaction temperatures. Surface chemical composition and signature were measured using gravimetric analysis, X-ray photoelectron spectroscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR). XPS data from the treated hemp fibers were characterized by measuring the reduction in O/C ratio and an increase in abundance of the CCO signature. FTIR confirmed the reaction with the emergence of peaks characteristic of disubstituted benzene and amino groups. Grafting of the sulfonic derivatives resulted in lower surface polarity. Thermogravimetric analysis revealed that treated fibers were characterized by lower percent degradation between 200 and 300°C, and a higher initial degradation temperature.