Copolymer Fibers Research Articles

Centrifugal melt spinning of polyvinylpyrrolidone (PVP)/triacontene copolymer fibres

Polyvinylpyrrolidone/1-triacontene (PVP/TA) copolymer fibre webs produced by centrifugal melt spinning were studied to determine the influence of jet rotation speed on morphology and internal structure as well as their potential utility as adsorbent capture media for disperse dye effluents. Fibres were produced at 72 °C with jet head rotation speeds from 7000 to 15,000 r min−1. The fibres were characterised by means of SEM, XRD and DSC. Adsorption behaviour was investigated by means of an isothermal bottle point adsorption study using a commercial disperse dye, Dianix AC-E. Through centrifugal spinning nanofibers and microfibers could be produced with individual fibres as fine as 200–300 nm and mean fibre diameters of ca. 1–2 µm. The PVP/TA fibres were mechanically brittle with characteristic brittle tensile fracture regions observed at the fibre ends. DSC and XRD analyses suggested that this brittleness was linked to the graft chain crystallisation where the PVP/TA was in the form of a radial brush copolymer. In this structure, the triacontene branches interlock and form small lateral crystals around an amorphous backbone. As an adsorbent, the PVP/TA fibres were found to adsorb 35.4 mg g−1 compared to a benchmark figure of 30.0 mg g−1 for a granular-activated carbon adsorbent under the same application conditions. PVP/TA is highly hydrophobic and adsorbs disperse dyes through the strong “hydrophobic bonding” interaction. Such fibrous assemblies may have applications in the targeted adsorption and separation of non-polar species from aqueous or polar environments.

Solution electrospinning of polypropylene-based fibers and their application in catalysis

Since the dissolution of polyolefins is a chronic problem, melt processing has been tacitly accepted as an obligation. In this work, polypropylene (PP) was modified on molecular level incorporating poly(ethylene glycol) (PEG) as graft segment (PP-g-PEG) in a range of 6 to 9 mol%. Gold nanoparticles were nucleated in the presence of the copolymer chains via redox reaction. The dissolution of the amphiphilic comb-type graft copolymers containing gold nanoparticles (80 nm in diameter) was achieved in toluene and successfully electrospun from its solution. The diameter of composite fibers was in the range from 0.3 to 2.5 μm. The design of the structurally organized copolymer fiber mats provided a support medium for the nanoparticles enhancing the active surface area for the catalytic applications. The resulting composite fibers exhibited rapid catalytic reduction of methylene blue (MB) dye in the presence of sodium borohydride (NaBH4) compared to corresponding composite cast film.

Excellent dielectric properties of PVDF-based composites filled with carbonized PAN/PEG copolymer fibers

Weak interfacial bonding between carbon materials and polymer matrix impedes the formation of homogeneous composites, challenging to the enhancement of dielectric properties of such systems. In this work, we designed novel carbonized polyacrylonitrile/polyethylene glycol copolymer fibers (CPCFs) and then used them as fillers to enhance the dielectric properties of poly(vinylidene fluoride) (PVDF)-based composites. These CPCFs are rich in nitrogen (8.55%) and oxygen (3.94%) atoms on the surface of them. The results of molecular dynamic (MD) simulations indicate that the existence of these atoms significantly increase the interaction energy between CPCFs and PVDF matrix from −45.13kcal/mol to −62.22kcal/mol, which promotes the intercalation of conductive CPCFs into insulated PVDF matrix to form ultrathin microcapacitors. As a result, the largest dielectric constant of CPCFs/PVDF composites can reach 1583 (1kHz), which is about 150times higher than that of pure PVDF.

Preparation of a thermosensitive fiber and its carbon dioxide adsorption/desorption properties

A thermosensitive fiber (VF-NIPAAM-co-AM) was developed by grafting N-isopropylacrylamide (NIPAAM) and acrylamide (AM) onto the surface of viscose fiber (VF) through the simultaneous grafting copolymerization approach. The grafted fiber was subsequently aminated with triethylenetetramine (TETA) to prepare a solid amine adsorbent for CO2 capture. The effect of NIPAAM/AM molar ratio on the thermosensitive properties of the grafted fiber was investigated. It was found that the contact angle of VF-NIPAAM-co-AM increased with the increasing of NIPAAM/AM molar ratio. For all the prepared fibers, the contact angle of VF-NIPAAM-co-AM at 343K was higher than that at 293K, indicating the thermosensitive property of the grafted copolymer fibers. After amination, the contact angle of VF-NIPAAM-co-AM-TETA at 293K and 343K were 79.86°and 84.14°, respectively. Even though the contact angles of aminated fibers decreased, the fiber still retained a certain thermosensitive property. Studies on the adsorption and desorption behaviors of VF-NIPAAM-co-AM-TETA and VF-AM-TETA indicated that CO2 could be more efficiently and completely desorbed from VF-NIPAAM-co-AM-TETA at 80°C than from VF-AM-TETA, a structurally similar fiber but without NIPAAM.

Elastic poly(ε-caprolactone)-polydimethylsiloxane copolymer fibers with shape memory effect for bone tissue engineering

A porous shape memory scaffold with biomimetic architecture is highly promising for bone tissue engineering applications. In this study, a series of new shape memory polyurethanes consisting of organic poly(ε-caprolactone) (PCL) segments and inorganic polydimethylsiloxane (PDMS) segments in different ratios (9 : 1, 8 : 2 and 7 : 3) was synthesised. These PCL-PDMS copolymers were further engineered into porous fibrous scaffolds by electrospinning. With different ratios of PCL: PDMS, the fibers showed various fiber diameters, thermal behaviour and mechanical properties. Even after being processed into fibrous structures, these PCL-PDMS copolymers maintained their shape memory properties, and all the fibers exhibited excellent shape recovery ratios of >90% and shape fixity ratios of >92% after 7 thermo-mechanical cycles. Biological assay results corroborated that the fibrous PCL-PDMS scaffolds were biocompatible by promoting osteoblast proliferation, functionally enhanced biomineralization-relevant alkaline phosphatase expression and mineral deposition. Our study demonstrated that the PCL-PDMS fibers with excellent shape memory properties are promising substrates as bioengineered grafts for bone regeneration.

New understanding on the reaction pathways of the polyacrylonitrile copolymer fiber pre-oxidation: online tracking by two-dimensional correlation FTIR spectroscopy

FTIR spectroscopy in combination with scaling-MW2D and 2D correlation analysis is used to study the reaction pathways of polyacrylonitrile copolymer fibers pre-oxidation.

Mechanical reinforcement of PBO fibers by dicarboxylic acid functionalized carbon nanotubes through in situ copolymerization

An optimized interfacial interaction in CNTs & PBO copolymer fibers was put into effect via dicarboxylic acids functionalized CNTs, which results in well dispersed, high reactivity and efficient load transfer between CNTs fillers and PBO matrix.

Polystyrene‐b‐poly(2,2,2‐trifluoroethyl acrylate)‐b‐polystyrene copolymers: Synthesis and fabrication of their hydrophobic porous films, spheres, and fibers

ABSTRACTNew block copolymers Polystyrene‐b‐poly (2,2,2‐trifluoroethyl acrylate)‐b‐Polystyrene (PS‐PTFEA‐PS) with controlled molecular weight (Mn=5000‐11000 g⋅mol−1) and narrow molecular weight distribution (Mw/Mn=1.13‐1.17) were synthesized via RAFT polymerization. The molecular structure and component of PS‐PTFEA‐PS block copolymers were characterized through 1H NMR, 19F NMR, GPC, FT‐IR and elemental analysis. The porous films of such copolymers with average pore size of 0.80‐1.34 μm and good regularity were fabricated via a static breath‐figure (BF) process. The effects of solvent, temperature, and polymer concentration on the surface morphology of such film were investigated. In addition, microstructured spheres and fibers of such block copolymers were fabricated by electrospinning process and observed by scanning electron microscopy (SEM). Furthermore, the hydrophobicity of porous films, spheres, and fibers was investigated. The porous film showed a good hydrophobicity with the water‐droplet contact angles of 129°, and the fibers showed higher hydrophobicity with the water‐droplet contact angles of 142°. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 678–685

Testing and analyses of copolymer fibers based on 5-amino-2-(p-aminophenyl)-benzimidazole

Fibers containing 5-amino-2-(p-aminophenyl)benzimidazole are being considered for use as reinforcement in soft body armor applications. Past research in this laboratory has resulted in a suite of tests that have been used to detect degradation in other fibers and are now being applied to the fibers in question. Due to the architecture of the yarns in this study, two methods to extract single filaments for tensile testing were described and analyzed. A dry method resulted in fibers with surface damage, reflected in a high standard deviation in strength. A wet extraction method showed a reduction in surface damage and a lower standard deviation in strength. Fourier Transform Infrared analysis detected signs of hydrolysis in the fibers that were exposed to water. Although no noticeable loss in tensile strength was noted upon exposure, the possibility of hydrolysis in these fibers may indicate a need for further study.

Smart Fiber Membrane for pH-Induced Oil/Water Separation.

Wastewater contaminated with oil or organic compounds poses threats to the environment and humans. Efficient separation of oil and water are highly desired yet still challenging. This paper reports the fabrication of a smart fiber membrane by depositing pH-responsive copolymer fibers on a stainless steel mesh through electrospinning. The cost-effective precursor material poly(methyl methacrylate)-block-poly(4-vinylpyridine) (PMMA-b-P4VP) was synthesized using copper(0)-mediated reversible-deactivation radical polymerization. The pH-responsive P4VP and the underwater oleophilic/hydrophilic PMMA confer the as-prepared membrane with switchable surface wettability toward water and oil. The three-dimensional network structure of the fibers considerably strengthens the oil/water wetting property of the membrane, which is highly desirable in the separation of oil and water mixtures. The as-prepared fiber membrane accomplishes gravity-driven pH-controllable oil/water separations. Oil selectively passes through the membrane, whereas water remains at the initial state; after the membrane is wetted with acidic water (pH 3), a reverse separation is realized. Both separations are highly efficient, and the membrane also exhibits switchable wettability after numerous cycles of the separation process. This cost-effective and easily mass-produced smart fiber membrane with excellent oil-fouling repellency has significant potential in practical applications, such as water purification and oil recovery.

Conformational Analysis of Chemically Reactive Groups in Polikon K. Part 2

Probable spatial fragments modeling polyacrylonitrile fiber, the monomerized composition, and Polikon K—Polikon K1a material were developed. The Polikon K1a model identified the most probable reaction site of the polyacrylonitrile copolymer fiber with reactive CH3– groups of the polymer matrix, namely, the reaction with a C≡N group via cleavage of one bond and formation of a methylene bridge. IR transmission spectra in the range 4000-200 cm–1 were calculated for the obtained models. Experimental and calculated IR spectra were compared in the range 2000-400 cm–1. The calculated IR spectrum correlated with the experimental spectrum of Polikon K.

Hybrid ZnO/TiO2Loaded in Electrospun Polymeric Fibers as Photocatalyst

Hybrid ZnO/TiO2nanoparticles were applied as potential photocatalyst agents incorporated into electrospun fibers of enteric block copolymers. The resistance of fibers avoids aggregation and contributes to prolonged action of semiconductor nanoparticles under continuous light irradiation. Such behavior is attributed to the minimal aggregation degree and elevated efficiency of photodegradation of modified nanoparticles in comparison with pristine ones. Hybrid ZnO/TiO2in nanofibers contributes to the association of different mechanisms such as N-deethylation and cleavage of dye molecules applied in the overall process of photodegradation.

Liquid-Phase Catalytic Oxidation of Styrene by a Fiber-Supported Copper(II) Complex with High Catalytic Performance

A new type of polymer-supported catalyst, [PS-(PBIM)2Cu (II)], was synthesized by loading 2-(2’-pyridyl) benzimidazole on chloromethylated propylene-styrene graft copolymer fiber and subsequent treatment with Cu (OAc)2 in methanol. The prepared catalyst was used in the oxidation of styrene with tert-butyl hydroperoxide (TBHP) as the oxidant. The important reaction conditions, such as the reaction temperature, the ratio of oxidant/styrene, and the recycle times were examined. The experimental results show that the catalyst reveals relatively high catalytic performance with 84% conversion for styrene. The suitable conditions are as follows: n (styrene):n (TBHP)=1:3, the reaction temperature of 80 °C and the reaction time of 8 h. In addition, the catalyst used repeatedly for 3 times can still possess high catalytic activity.

진공압밀 공법용 등방성 스펀본드 지오텍스타일의 성능평가

In this study, the performance of isotropic spun-bonded geotextiles, which are used in vacuum consolidation,was tested both in the laboratory and in the field. Two kinds of isotropic spun-bonded geotextiles were prepared. One was a matrix/binder structure using low-melting polyethylene terephthalate (PET) copolymer (co-PET) fibers forweb bonding. The other consisted of sheath/core (co-PET/PET) fibers. Through the index test, it was seen that the performanceof the sheath/core structure isotropic spun-bonded geotextiles was better for use with vacuum consolidationthan the matrix/binder structure isotropic spun-bonded geotextiles. However, the drainage performance test, which simulatesa construction environment, showed that the sheath/core structure isotropic spun-bonded geotextiles were unstable. The matrix/binder isotropic spun-bonded geotextiles showed better results for the drainage test and the field testresults for the matrix/binder isotropic spun-bonded geotextiles showed that they were suitable for use with vacuum consolidation.

Improved compressive strength of poly(p-phenylene benzobisoxazole) copolymer fiber containing multi-functional comonomer

Multi-functional comonomer from pentaerythritol (PE) and terephthaloyl chloride (TPC) was synthesized and used for polymerization of poly(p-phenylene benzobisoxazole) (PBO) copolymer. PBO copolymer fibers were prepared from PBO copolymers using a dry-jet wet spinning. The tensile strength of PBO copolymer fibers was higher than that of PBO, and showed 42 % increase at 0.5 mol% loading of comonomer. The tensile modulus of PBO copolymer fiber at 0.5 mol% loading showed 192 % increase compared to PBO fiber. The compressive strength of PBO copolymer fiber had values between 0.46 GPa and 0.6 GPa with the comonomer content. 64-114 % increase in compressive strength of PBO copolymer fibers was observed compared to PBO fiber.

Superhydrophobic surfaces of electrospun block copolymer fibers with low content of fluorosilicones

Abstract A series of well-defined poly[methyl(3,3,3-trifluoropropyl)siloxane]- b -poly(methyl methacrylate) (PMTFPS- b -PMMA) diblock copolymers with low content of PMTFPS were synthesized by atom transfer radical polymerization (ATRP) of MMA from PMTFPS macroinitiators (PMTFPS-Br). The polymerization result reveals that the ATRP of MMA from PMTFPS-Br is fist-order with respect to MMA under different polymerization conditions, demonstrating a typical characteristic of living polymerization. The results also show that PMTFPS- b -PMMA diblock copolymers can exhibit a total surface tension ( γ S ) varying from 25.28 mN/m to 21.87 mN/m with the change of PMTFPS contents from 2.6 wt% to 22.2 wt%. Moreover, the water contact angles of electrospun PMTFPS- b -PMMA surfaces could be higher than 150° with water roll-off angles less than 10°, which denotes a superhydrophobic property. However, the electronspinning conditions, especially the concentration of spinning solution, would have important effect on the surface morphology, surface composition and wetting behavior of electrospun films. It was found that bead-free fibers with uniform diameter as well as good superhydrophobic property could be prepared on condition that the polymer concentration of spinning solution was as high as 32 wt% in the mixed solvent of DMF and THF.

Effect of draw ratio on the morphologies and properties of BPDA/PMDA/ODA polyimide fibers

3,3,4,4-Biphenyltetracarboxylic dianhydride/pyromellitic dianhydride/4,4-oxydianiline(BPDA/PMDA/ ODA) polyimide copolymer fibers with different draw ratios were prepared from the imidization of polyacrylic acid(PAA) fibers via a dry-jet wet-spinning process. Their morphologies, microcrystal orientations, thermal stabilities, and mechanical properties were investigated via scanning electron microscopy(SEM), wide angle X-ray diffraction( WAXD), thermogravimetric analysis(TGA), and tensile experiments. In order to acquire fibers with better mechanical performance, we aimed at obtaining the optimal draw ratio. Drawing during thermal imidization resulted in a decreased diameter of fiber from 25.8 μm to 16.9 μm corresponding to draw ratio from 1 to 3.5. WAXD results show that the degree of the orientation of the undrawn sample is 64.1%, whereas that of the drawn sample is up to 82%. The as-spun fiber and those with different draw ratios all exhibit high thermal stabilities, i.e., the temperature at a mass loss of 5% can reach as high as 570 °C. The tensile strengths and tensile modulus of the fibers increase with the draw ratios, and the maximum tensile strength and modulus are 0.90 and 12.61 GPa, respectively.

Research on the low-loss Topas cyclic olefin copolymer fiber

Research on the low-loss Topas cyclic olefin copolymer fiber

Effect of electrospun ethylene vinyl alcohol copolymer (EVOH) fibres on the structure, morphology, and properties of poly(lactic acid) (PLA)

The effect of ethylene content and of the concentration of the solution used for electrospinning on the morphology of electrospun poly ethylene vinyl alcohol (EVOH) fibre was studied. Also, poly(lactic acid) (PLA) filled with electrospun EVOH fibres was investigated. Good interfacial adhesion between PLA and EVOH fibres was obtained with smaller diameter fibres. The effect of electrospun fibres resulted in disrupted lamellar morphology and also decreased the degree of crystallinity related to the semicrystalline framework. Surface roughness was calculated using atomic force microscopy (AFM). Surface roughness increased with the increase in fibre diameters. The rheology experiments revealed that electrospun EVOH fibres enhance the storage modulus of PLA composites while having low crystallinity. EVOH fibres showed the capacity of tuning the degradation behaviour. The good interfacial morphology between PLA and smaller diameter fibres slowed down the degradation rate, whereas composites with larger diameter fibres, due to poor interfacial adhesion showed faster degradation rate than the other compositions, because large EVOH fibres afford channels by which NaOH solution can easily penetrate throughout the composite material. The incorporation of EVOH fibres into PLA matrix allowed obtaining materials with increased storage modulus and also showed viability to tune the degradation behaviour of PLA based products.

Barrier Screw Compounding and Mechanical Properties of EAA Copolymer and Cellulose Fiber Composite

Abstract The difficulty of feeding cellulose fibers and thermoplastics into the extruder or injection molding machine is addressed, this being a serious problem in the production of cellulose fiber composites for industrial applications. Agglomerates consisting in cellulose fibers and ethylene-acrylic acid copolymer (EAA) with different cellulose contents and different fiber lengths were processed with two different screws in order to better understand how the dispersion of the fibers can be improved by melt extrusion. A conventional screw with a compression ratio of 4:1 and a screw with barrier flights were used at different screw rotation speeds. The fiber length and fiber content were measured and microscopic analyses were performed in order to estimate the number and size of the cellulose fiber aggregates in the final composites. It was concluded that the barrier screw was more effective than the conventional screw in breaking up the fiber aggregates and dispersing the fibers. More but smaller cellulose aggregates were observed when the barrier screw was used, and the reduction of length was significantly greater for long than for short fibers. In contrast to that was expected, the samples containing the shorter fibers had better mechanical properties, probably due to a better dispersion of the fibers.