Different Degrees Of Orientation Research Articles

Investigation of the influence of the draw ratio on the enzyme catalysed degradation of poly(ethylene terephthalate) fibres using nanoscale surface thermal analysis

Enzyme catalysed hydrolysis provides an environmentally friendly route for controlled degradation of poly(ethylene terephthalate) fibres. In this work, the hydrolysis of PET fibres with different degrees of orientation by a cutinase from Humicola insolens (HiC) was investigated using the advanced nanoscale surface sensitive thermal analysis (nanoTA) with the aim, to better understand the mechanism of the enzyme catalysed degradation. The hydrolysis was found to occur preferentially at the outer fibre layer, leading to a release of monomer and ablation of the fibre surface. As polymer amorphous regions are more susceptible to enzymatic hydrolysis and since initially hydrolysis is limited to the outer fibre layer, the change in crystallinity occurs mainly in the fibre surface region and does not contribute to the overall crystallinity of the fibre. A higher degree of fibre orientation by drawing reduces the attack of the enzyme and preserves the high order and strength of the fibres during the hydrolysis. The results provide further basis for the optimisation of enzyme catalysed surface hydrolysis and polymer degradation processes of PET fibres.

Комплексная диэлектрическая проницаемость пленок ПВДФ в диапазоне инфранизких частот, определенная методом релаксационных карт термостимулированных токов

The paper shows the possibility of interpreting the results of thermal activation spectroscopy of PVDF polymer films obtained by thermally stimulated currents of fractional polarization using the concepts of low-frequency dielectric spectroscopy. The paper presents the results of the study of temperature-frequency dependences of the components of complex dielectric permittivity in PVDF films with different degrees of orientation, polymorphic composition and pore percentage. It also provides the parameters of electrically active defects responsible for relaxation processes in the temperature range under study.

The colloidal structure of a cellulose fiber

We present a small angle X-ray scattering (SAXS) study of the colloidal structure of regenerated cellulose fibers, air-gap spun from an ionic liquid solution. Based on the data, and a different interpretation of the anisotropic SAXS pattern, we propose a slightly different colloidal structure of the fibers, than what is commonly assumed for regenerated cellulose fibers. Fibers with two different degrees of orientation, as produced by different draw ratios, DR = 2 and 15, respectively, are analyzed. The 2D SAXS pattern is highly anisotropic with striking cross-like pattern, having scattering predominantly perpendicular and parallel to the fiber axis. This cross-like pattern suggest a colloidal structure with oriented crystalline lamellae of ca. 10 nm thickness, embedded within a continuous matrix of amorphous cellulose. The lamellae are oriented with their normal parallel with the fiber axis. Complementary wide angle X-ray diffraction data confirm that the lamellae normal direction corresponds to the cellulose chain direction (c-direction) in the monoclinic cellulose crystal (Cellulose II).Graphic abstract

Structure evolution in all-aromatic, poly(p-phenylene-vinylene)-derived carbon fibers

Carbon fiber (CF) structure is strongly influenced in terms of CF's crystallinity, crystallite dimensions, orientation, and interlayer spacing by the structure of the CF precursor, including its sp2/sp3 carbon content, and the process parameters for spinning, oxidative stabilization, and carbonization/graphitization. In order to retrieve information about structure formation in all-aromatic CF precursors, poly(p-phenylene-vinylene) (PPV) fibers have been prepared through dry spinning of a sulfinyl-based precursor polymer followed by thermal conversion into PPV. By applying different stretch ratios, different degrees of orientation were realized. Subsequent thermal conversion of these PPV fibers into CFs with and without additional tension during carbonization allowed for following structure formation in the final CFs. Wide-angle X-ray scattering and Raman data were recorded at different stages of carbonization and compared to those of a poly(acrylonitrile)-derived CF as well as to lignin- and cellulose-derived CFs. Structure formation during carbonization was correlated with the sp2/sp3 carbon content of the CF precursors. The all-sp2 carbon precursor PPV was found to favor crystallite growth in the direction of the CF axis, parallel to the individual graphite planes, and formation of ordered graphitic structures at an earlier stage and to a higher extent than in high-/all-sp3 carbon precursors.

Dry adhesives from carbon nanofibers grown in an open ethanol flame.

Based on magnetic-field-assisted growth of carbon nanofibers in an open ethanol flame we fabricated arrays of carbon nanofibers with different degrees of orientation. Inspired by the dry adhesive system of geckos we investigated the adhesive properties of such carbon nanofiber arrays with ordered and random orientation. AFM-based force spectroscopy revealed that adhesion force and energy rise linear with preload force. Carbon nanofibers oriented by a magnetic field show a 68% higher adhesion (0.66 N/cm2) than the randomly oriented fibers. Endurance tests revealed that the carbon nanofiber arrays withstand 50.000 attachment/detachment cycles without observable wear.

The influence of crystal orientation on the change in Li chemical potential of LiCoO2 under mechanical stress

Change of the lithium chemical potential in a crystalline LiCoO2 with the application of a mechanical stress was discussed based on the results of electromotive force (emf) measurements between preferentially-oriented LiCoO2 films on Li0.33La0.55TiO3 solid electrolytes under mechanical stress. [00l]-oriented LiCoO2 films with different degrees of orientation were prepared, and it was investigated how the direction of mechanical stress to the crystal lattice affects emf. It is found that emf emerged when mechanical stress was applied. The magnitude of emf under stress was dependent not only on the magnitude of applied stress but also the degree of the film orientation. This clearly demonstrated that the crystal orientation, i.e. the direction of mechanical stress to the crystal, affects the lithium chemical potential.

Ion Conducting Conduits with a Tortuosity of One from One Electrode to Another: The Role of Domain Connectivity and Tortuosity on Ion Conductivity in Block Copolymer Electrolyte Thin Films

Block copolymer electrolytes (BCEs) are attractive candidates for electrochemical devices due to their ability to micro-phase segregate into two chemically distinct domains – one ion conducting and one ion insulating and mechanically resilient. BCEs can be simultaneously optimized for both ion conductivity and mechanical rigidity, variables inversely correlated in traditional polymer electrolytes. Recent reports correlate anisotropic orientation of the domains relative to the electrode to increase ionic conductivity, however it can be difficult to probe structure characteristics such as interconnectivity and tortuosity and the role of defects, like grain boundaries, on ion conductivity in bulk membrane materials1–3. This contribution disseminates a powerful, analytical platform for probing the relationship between BCE microphase separation and ion conductivity with unprecedented resolution via directed self-assembly (DSA) of BCE thin films into interdigitated electrode architectures. In this approach, we aligned the poly(styrene-b-2-vinylpyridine) (PSbP2VP) block copolymer to different degrees of orientation between two in-plane electrodes using topographic electrode guiding walls – a process known as graphoepitaxy. Using different wall designs, we oriented the block copolymer domains into pathways with varying transport lengths, tortuosities, and interconnectivities4. Following orientation, we modified the P2VP domain via a Menshutkin reaction to form an anion conducting domain5. The reaction is used to convert the 2-vinyl pyridine to n-methyl-2-vinylpyridinium iodide. The process is shown in Figure 1 along with a micrograph showing orthogonally oriented BCE domains relative to the electrode walls. The orientation and structures of the BCE were characterized using routine surface metrology tools such as SEM and AFM. Visual python code quantified the micrographs by extracting factors such as tortuosity and structure factors and correlated them to the ion conductivity performance. Structure variables such as ion conduction length, orientation to electrodes, tortuosity, and interconnectivity were characterized using electrochemical impedance spectroscopy (EIS). From the EIS, we inferred mechanisms of ion migration that contribute to the complex circuit behaviors of micro-phase segregated BCEs. We also report unexpected behaviors for interconnected and anisotropic domains that suggest further enhancements in solid state electrolyte systems and warrant future studies. Controlling the BCE architecture in thin film BCEs is envisioned as an attractive, unprecedented platform to understand the role structure plays in ion transport. Establishing accurate structure-property relationships will play a prominent role in the rationale design of BCE membrane separators for fuel cells, flow batteries, and electrolyzers with high ion conductivity without sacrificing mechanical integrity.

Controlled direction of electrical and mechanical properties in nickel tethered graphene polyimide nanocomposites using magnetic field

Oriented hybrid nickel tethered graphene polyimide resin nanocomposites with different degrees of orientation were prepared by in-situ magnetic field solvent casting method. Magnetization of the hybrid Ni-graphene polyimide nanocomposites exhibited a maximum in the magnetic field direction and a minimum perpendicular to the magnetic field direction indicating the orientation of the superparamagnetic nickel nanoparticles. In-plane dc electrical conductivity of the 1.3vol.% Ni-graphene was 2.5 times higher when cast in a high magnetic field compared to films cast without an applied magnetic field. The through-plane dc conductivity of the 1.3vol.% oriented Ni-graphene polyimide nanocomposites decreased with increasing magnetic field strength and reached insulation (10−12S/cm) for the films cast in high magnetic field. The in-plane tensile modulus of the polyimide exhibited a 35% increase when 0.16vol.% Ni-graphene was added to the polyimide and cast in a low-strength magnetic field. Further addition of Ni-graphene, up to 1.3vol.%, to the polyimide resulted in nearly constant tensile moduli. Tensile strength of nickel graphene nanocomposites showed up to 2-fold increase compared to the neat polyimide. Scanning electron microscopy (SEM) revealed that the Ni-graphene nanosheets were oriented in the magnetic field direction.

Process-property-structure relationship in miniaturized injection moulded polyoxymethylene samples

Micro-injection moulding is one of the key manufacturing technologies for thermoplastic polymeric materials for the mass production of high value miniaturized components. However, this process is not just a straightforward down scaling of the conventional injection moulding technique. Indeed, during the micro-injection the polymer melt is forced to flow at high strain rates through very small channels in nonisothermal conditions; this can lead to complex microstructures and to parts with unexpected performances. In this work, the relationships among the processing conditions, the mechanical properties and the microstructural characteristics of polyoxymethylene miniaturized specimens obtained by injection moulding were investigated. The attention was focused on the influence of the process temperatures on the mechanical behavior, examined by uniaxial tensile tests, and on the microstructural characteristics of the specimens, examined by differential scanning calorimetry, wide-angle X-ray diffraction, polarized light microscopy, and dynamic-mechanical thermal analysis. The results highlighted that material ductility in the miniaturized specimens is significantly affected by the mould temperature, because of the sample microstructure. Different degrees of orientation of polymer crystallites and different morphologies of the skin/core transition region were observed in dependence on the process temperatures. POLYM. ENG. SCI., 54:512–521, 2014. © 2013 Society of Plastics Engineers

Basic Study on the Discrimination of Poly(ethylene terephthalate) Fibres by Polarized Confocal Raman Spectroscopy

In forensics, fibres are usually identified by Fourier transform infrared (FT-IR) spectroscopy. Poly(ethylene terephthalate) (PET) fibres from garments are commonly identified, and it is important to be able to discriminate between PET fibres with different manufacturing histories. However, while FT-IR can be used for PET identification, it cannot be used to fully discriminate between different manufacturing subgroups. In this report, the application of polarized confocal Raman microspectroscopy, with the calculation of polarization ratios, can provide better discrimination of manufacturing subgroups than FT-IR. However, the effects of fibre degree of orientation and crystallinity on Raman results have not been investigated previously. In the present study, the effects of these fibre parameters on Raman-derived polarization ratios were investigated for 21 different PET fibres from four different manufacturers. Among the different Raman bands, the 1614 cm−1 band provided the best discrimination of the manufacturing subgroups. The 1614 cm−1 polarization ratio was affected by the fibre degree of orientation but not by the degree of crystallinity. The discriminating power of this method was 83.8 %, and the standard deviation at the 1614 cm−1 polarization ratio was quite low. Furthermore, polarization ratios, even though the fibres varied in diameter (10–45 μm), gave similar values calculated utilizing the intensity of the 1614 cm−1 band. Confocal Raman microspectroscopy can successfully discriminate fibres with different degrees of orientation and crystallinity, and different diameters, when the 1614 cm−1 band is used to calculate the polarization ratio.

Preparation of oriented graphite/polymer composite sheets with high thermal conductivities by tape casting

Oriented graphite/polymer composite sheets were prepared using natural, crystalline flake graphites as raw materials, polyvinyl butyral as binders, polyethylene glycol and dibutyl phthalate as plasticizers by a tape-casting method at room temperature. The dependences of the binder contents and the blade heights on the orientation of the composite sheets were studied, and the effect of the orientation on the thermal conductivity was investigated. X-ray diffraction patterns and scanning electron microscope images showed that as-prepared samples showed different degrees of orientation. The thermal conductivity increased with the degree of orientation. The highest thermal conductivity of 490 W/(m·K) could be achieved by optimizing the binder contents and the blade heights.

Orientation microstructure and properties of poly(propylene carbonate)/poly(butylene succinate) blend films

AbstractThe blends of high molecular weight poly(propylene carbonate) (PPC) and poly(butylene succinate) (PBS) were melt blended using triphenylmethane triisocyanate (TTI) as a reactive coupling agent. TTI also serves as a compatibilizer for the blends of PPC and PBS. The blend containing 0.36 wt % TTI showed that the optimal mechanical properties were, therefore, calendared into films with different degrees of orientation. The calendering condition, degree of orientation, morphologies, mechanical properties, crystallization, and thermal behaviors of the films were investigated using wide‐angle X‐ray diffraction, scanning electron microscopy, tensile testing, and differential scanning calorimetry (DSC) techniques. The result showed that the as‐made films exhibited obvious orientation in machine direction (MD). Both tensile strength in MD and the tear strength in transverse direction (TD) increased with increasing the degree of orientation. The orientation of the film also increased the crystallinity and improved the thermal properties of the PPC/PBS blend films. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Electrooptical properties of aqueous suspensions of nickel hydrosilicate nanotubes

We present the results of our investigations of electrooptical effects that occur as a result of light scattering by an aqueous polydisperse system the disperse phase of which consists of nickel hydrosilicate nanotubes with a chrysotile structure. Multilayer nanotubes were synthesized by the hydrothermal method and had the composition Ni3Si2O5. The dimensions of nanotubes were as follows: the length was 0.1–1 μm or more, the outer diameter was 10–15 nm, and the inner diameter was 3 nm. We have studied relative changes in the intensities of light transmitted and scattered by the suspension that were caused by the orientation of nanotubes in an external electric field. Experiments have been performed at different directions of the linear polarization of the incident and scattered light, different scattering angles, and different degrees of orientation of nanotubes along the field. These measurements allowed us to determine the magnitude of electrooptical effects, such as the conservative dichroism, the light scattering, and the influence of the orientation of nanotubes in the field on the intensity and degree of depolarization of light scattered by them. Curves of free relaxation of electrooptical effects and their field dependences allowed us to determine the distributions of nanotubes and their aggregates in the colloid over lengths and polarizability anisotropy values. The dependences of the degree of depolarization of the scattered radiation on the scattering angle and the relaxation dependences of electrooptical effects allowed us to characterize the aggregation stability of nanotubes in water.

Stretched inverse opal colloid crystal substrates-induced orientation of fibroblast

Recently, there has been increasing interest in studying the interaction between mammalian cells and nanometer-sized structures. However, the effect of nanostructures on cell behavior, such as cell morphology and alignment, is still largely unknown. Inverse opal colloid crystal substrates, which can be stretched to produce nano-scale pore structures of different degrees of orientation, serve as a convenient model system to study the effect of nanotopography on cell morphology and cell alignment. In this work, we fabricated inverse opal colloidal crystal films that were either unstretched or stretched to three, four or six times their original length, producing pore structures of increasing degree of orientation. Human dermal fibroblast-fetal (HDF-f) cells were seeded and cultured on these four types of substrates. The results from fluorescence microscopy and scanning electron microscopy indicated that cells showed the highest degree of alignment when cultured on inverse opal colloid crystal films that were stretched the most (six times original length). The results also demonstrated that the orientation of nanostructures could affect both the morphology and growth direction of fibroblasts. The ability to control the direction of cell growth through the engineering of nanostructures could have important applications in tissue engineering, especially for tissues with anisotropic structures, such as cardiac muscle, blood vessel, tendon and ligament.

Hot consolidated all-PP composites from textile fabrics composed of isotactic PP filaments with different degrees of orientation

Self-reinforced polypropylene composites (SRPPC) were hot pressed from textile layers (carded mat, knitted fabrics) at three different temperatures (160, 165 and 170°C) by setting a constant pressure (6 MPa) and constant holding time (2 min). Both textiles consist of two kinds of isotactic polypropylene (iPP) fibers differing in their orientation. In these compositions the highly oriented iPP works as reinforcement and the less oriented one fulfills the role of the matrix after hot consolidation. Two textile assemblies, viz. carded (also needle punched) mats and knitted fabrics were hot pressed; and the properties of the resultant SRPPC plates were investigated under tensile and falling weight impact conditions. The microstructure of the SRPPC was analyzed by light microscopy using polished sections and by SEM using cut surfaces.

Calculation of the Band Intensities of the IR Spectra of Oriented Polymers

An attempt has been made to extend the theory of IR spectra of polymers to oriented polymers. Formulas for the absorption-band intensities in polarization IR spectra of oriented polymers reflecting the dependence of the polarized absorption-band intensity on the structural and orientation characteristics of polymers have been obtained. These formulas permit calculating the intensity of polarized absorption bands at different degrees of orientation of the polymer.

Optical properties and orientation in polyethylene blown films

AbstractWe report structural factors affecting the optical properties of blown polyethylene films. Two types of blown polyethylene films of similar degrees of crystallinity were made from (1) single‐site‐catalyst high‐density polyethylene (HDPE; STAR α) and (2) Ziegler–Natta‐catalyst HDPE (ZN) resins. The STAR α film exhibited high clarity and gloss, whereas the ZN film was turbid. Small‐angle X‐ray scattering (SAXS), small‐angle light scattering (SALS), and optical microscopy gave quantitative and qualitative information regarding structure and orientation in the films. A new approach is described for determining the three‐dimensional lamellar normal orientation from SAXS. Both the clear STAR α and turbid ZN films had similar lamellar crystalline structures and long periods but displayed different degrees of orientation. It is demonstrated that optical haze is related to surface features that seem to be linked to the bulk morphology. The relationship between haze and structural orientation is described. The lamellar orientation is linked to rodlike structures seen in optical microscopy and SALS through a stacked lamellar or cylindrite morphology on a nanometer scale and through a fiberlike morphology on a micrometer scale. The micrometer‐scale, rodlike structures seem directly related to surface roughness in a comparison of index‐matched immersion and surface micrographs. The higher haze and lower gloss of the ZN film was caused by extensive surface roughness not observed in the STAR α film. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2923–2936, 2001

Influence of morphology on photo‐degradation of low density polyethylene films

AbstractThe effect of the morphology on photo‐degradation was investigated for low‐density polyethylene materials. For this purpose, films with different degrees of crystallinity and different degrees of orientation were prepared. For all the films, photodegradation was promoted at 336K for 12 days using a weather meter. The following results were obtained. There existed an induction period before degradation or chain scission. The induction period was longer for stretched films than for un‐stretched ones. Also, the rate of degradation became lower for stretched films. However, both the induction period and the rate of degradation hardly changed with heat‐treatment condition, that is, the degree of crystallinity. In the induction period, the density changed in a complicated manner. This complicated change must be due to the change in the molecular aggregation state of the amorphous phase. The rheological and GPC measurements indicated that photo‐degradation causes the lowering of molecular weight and the increase in higher molecular weight fraction, and consequently the broadening of molecular weight distribution. The lowering of molecular weight may be caused by chain scission and the increase in higher molecular weight fraction by the formation of crosslinks.

Solution and Solid State Behavior of Poly(N-Acetyliminoethylene)–Poly(Methacrylic Acid) Interpolymer Complexes

A thorough comparative study of poly(N-acetyliminoethylene)-poly-(methacrylic acid) blends, corresponding synthetic complexes and template complexes was performed. The experimental data, obtained from DSC, TGA, X-ray diffraction, viscometric and turbidimetric determinations, showed the dependence of the solution and solid state properties of the studied systems, not only on their structural features but also on the adopted preparative approach. The different degrees of orientation of groups involved in interpolymer hydrogen bonding interactions yielded a higher thermal stability for template complexes as compared to the other studied polymeric materials. The possibility of transforming the physical interpolymer bonds into chemical ones through a transamidation reaction was evidenced.

Effects of dispersion on interaction and orientation in barium ferrite tapes

Interactions between Ba-ferrite particles have been examined from measurements of remanence curves. Hand-spread tapes with different degrees of orientation, controlled by the orientation field and milling time, have been studied. The results show that the effect of the orientation field is to improve the easy axis distribution. Thus, as milling proceeds, squareness, the peak value of the Δ/( H) curve and the degree of easy axis orientation, all increase. Towards the end of the milling process, the tendency to stack is reduced as the dispersion quality improves and this reduces the orientational texture.