Polarized Light Microscopy Observations Research Articles

Shear-induced crystallization morphology and mechanical property of high density polyethylene in micro-injection molding

The advances of the polymer melt flow-induced crystallization behaviour and its influence on mechanical properties of high density polyethylene (HDPE) in micron injection (MI) were studied in the present paper. Analysis of mechanical performance, including yield stress and elongation at break, for samples adopted from different regions in a molded plaque showed that a higher injection speed, a higher mold temperature and a longer cooling time could effectively enhance the yield stress but negatively promoted the ductility. Then, the mechanisms of such variation of mechanical performance and the factors affecting it were investigated by means of differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and polarized light microscopy (PLM). The super high shear rate during cavity feeding in MI molding not only induced a typical three-layered structure but also developed a highly oriented fibrously morphological structure in the skin layer. However, such fully oriented morphology was much negative in the interlayer and even could not be observed in the core layer. The results from SEM and PLM observations indicated that the orientation morphology varied significantly through the plaque’s cross-section and thickness of the each layer changed with the process parameters and geometric position, and finally led to variation of the mechanical performance.

Nd:YVO4 laser removal of graffiti from granite. Influence of paint and rock properties on cleaning efficacy

This paper presents the cleaning efficiency results for four differently coloured graffiti paints applied to two types of granitic stone by Nd:YVO4 laser at 355nm. The paints were characterized in terms of mineralogy and chemistry using x-ray fluorescence, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM); paint absorbance in the ultraviolet–visible-infrared range (200–2000nm) was also assessed. The studied granites had different mineralogy, texture and porosity properties. Cleaning efficiency was evaluated by polarized microscopy, SEM, FTIR spectroscopy and spectrophotometer colour measurements. The results indicate differences in the effectiveness of surface cleaning for the blue, red and black paints as opposed to the silver paint, mainly attributed to chemical composition. No evidence was found that the granite properties had a bearing on laser effectiveness, although the degree, type and spatial distribution of transgranular fissures in the stone affected the overall assessment of cleaning effectiveness. Polarized light microscopy observations and colour measurements showed that the intensity and distribution of fissures affect the depth of paint penetration, ultimately affecting the cleaning efficiency for both granites.

Effect of β-Nucleating Agent on the Crystallization, Mechanical Properties, and Heat Resistance of Injection-Molded Isotactic Polypropylene

Injection-molded β-isotactic polypropylene (β-iPP) was prepared with a commercial β-nucleating agent (NT-A). The effect of NT-A on the crystallization, mechanical properties, and heat resistance of β-iPP was investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), polarized light microscopy (PLM), and mechanical and heat deflection tests. DSC and WAXD analysis showed that the content of β-crystals in the nucleated iPP was higher than that of pure iPP, and the content of β-crystals of the core was higher than that of the skin. PLM observations showed that injection-molded iPP had an obvious skin-core structure. NT-A induced abundant β-crystals and resulted in small spherulites which improved the Izod notched impact strength. When the content of NT-A was 0.075wt%, the Izod notched impact strength reached a maximum, 2.6 times more than that of pure iPP. The heat distortion temperature was also improved by NT-A.

Morphological Distribution in Micro-Injected Polypropylene Parts in the Presence of β-Nucleating Agent

Micro-injection molding is attracting much attention nowadays. Characterization of the morphological distribution in parts prepared by micro-injection molding is thus of growing importance. The morphological features of micro-parts may strongly differ from those of the macro-parts prepared by conventional injection molding, resulting in specific physical properties. In the present study, β-nucleated isotactic polypropylene micro-parts (μPPB) with 200 μm thickness, as well as macro-parts (PPB) with 2000 μm thickness, were prepared. Polarized light microscopy (PLM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WAXD) were used to investigate their morphological features. The results show that the morphology distribution in μPPB had many differences from that of the PPB. The one-dimensional WAXD and DSC analysis showed similar results; the degree of crystallinity of the μPPB was higher than that of the PPB. However, the content of β-crystals of μPPB was lower than that of the PPB. This can be explained by the restraining effect for the formation of β-crystals in β-nucleated isotactic polypropylene (iPP) under the strong shear field. The through-the thickness-morphology of both μPPB and PPB exhibited a “skin-core” structure from PLM observations, but the former had a large fraction of shear layer in comparison to the latter implied. The SEM observations showed that the shear layer of μPPB consisted of a highly oriented shish-kebab structure, while that of the core layer consisted of deformed spherulites structure. The two-dimensional WAXD pattern of the core layer of PPB, showing full Debye rings, indicated an overall random orientation of the iPP chains, while the arcing indicated a pronounced orientation in the shear layer. The more pronounced arcing of the μPPB indicated a more pronounced orientation.

Graphite blocks with preferred orientation and high thermal conductivity

Graphite blocks were prepared from natural graphite (NG) flake and mesophase pitch powder by a hot-pressing technique at a relatively low temperature (500 °C). The effect of pitch binder content and heat-treatment temperature on the physical properties of the graphite blocks was investigated. X-ray analyses indicate that the graphite block has a highly preferred structural orientation, and field emission scanning electron microscopy and polarized light microscopy observations further prove that the graphitic layers of the graphite flakes are clearly oriented perpendicular to the hot-pressing direction. Graphitized blocks prepared from 86 wt.% NG and 14 wt.% mesophase pitch have a low electrical resistivity of 1.45 μΩ m and a high thermal conductivity of 522 W/m K, as well as a high thermal diffusivity of 396 mm 2/s in the direction perpendicular to the hot-pressing direction at room temperature.

Morphological comparison of isotactic polypropylene parts prepared by micro‐injection molding and conventional injection molding

AbstractThe morphological feature of microparts evolved during micro‐injection molding may differ from that of the macroparts prepared by conventional injection molding, resulting in specific physical properties. In this study, isotactic polypropylene (iPP) microparts with 200 µm thickness and macroparts with 2000 µm thickness were prepared, and their morphological comparison was investigated by means of polarized light microscopy (PLM), scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and wide‐angle X‐ray diffraction (WAXD). The results presented some similarities and differences. PLM observations showed that the through‐the thickness‐morphology of micropart exhibited a similar “skin–core” structure as macropart, but presented a large fraction of shear layer in comparison to the macropart which presented a large fraction of core layer. The SEM observation of shear layer of micropart featured highly oriented shish‐kebab structure. The micropart had a more homogeneous distribution of lamellae thickness. The degree of crystallinity of the micropart was found to be higher than that of the macropart. High content of β‐crystal was found in micropart. The 2D WAXD pattern of the core layer of macropart showed full Debye rings indicating a random orientation, while the arcing of the shear layer indicates a pronounced orientation. The most pronounced arcing of the micropart indicates the most pronounced orientation of iPP chains within lamellae. Copyright © 2011 John Wiley & Sons, Ltd.

Red soils with white net-like veins and their climate significance in south China

The microstructure, particle size distribution, mineral and chemical compositions of both the white net-like veins and the red matrix of the Xuancheng laterite soil section in Anhui, south China, in the middle to lower reaches of the Yangtze River, were investigated using X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), polarized light microscopy observation, and particle size distribution analysis. There was more quartz while less clay minerals in the white veins relative to the red matrix. In particle size distribution patterns the more abundant 5–20 μm particle size component of the white veins resulted from their higher quartz content. Discrepancy in degree of weathering between the white veins and the red matrix was derived from the depletion of Fe 2O 3 (total) and MnO 2 and the relative accumulation of SiO 2 in the white veins. White veins across the lithological layers and inclusions of relict red matrix material in the white veins indicated that the net-like soils originated from an initial uniform red soil. The white spots or veins were derived from the long-term modification of the pre-existing soil or concurrent weathering soils. Hydrodynamic conditions of the groundwater exerted influence on the formation of white veins. The formation process of the white net-like veins was different from that of the red matrix, suggesting that the white vein materials reflected a hydrological imprint upon the result of these conditions. The net-like soils in south China were compatible to the mottled soils in Africa, Australia, India, and Brazil. However, much more intense depletion of Fe oxide and much better developed white veins in the net-like soils of south China suggest probably even warmer and more humid palaeoclimatic conditions relative to those in Africa, Australia, India, and Brazil during the period.

Problems in polarized light microscopy observation of birefringence of calcium pyrophosphate dihydrate crystals

To reconsider the problems arising from the use of the phase plate as a test plate inserted into a polarized light microscope system for the analysis of triclinic calcium pyrophosphate dihydrate (t-CPPD) crystals, or Ca 2P 2O 7·2H 2O in the synovial fluid of arthritis patients, we made the polarized light microscopy observations using a phase plate with a retardation of 530 nm for the synthesized t-CPPD crystals well-characterized by X-ray powder pattern indexing and single crystal X-ray diffraction measurements. The microscopy observations were made of crystals of different sizes, thicknesses and shapes. The retardation was assessed using the interference color chart at four extinction and diagonal positions both with and without the test plate. The addition and subtraction states produced by superimposing the retardations of two anisotropic materials, that is, the t-CPPD crystal and the 530 nm phase plate, were deduced from the interference color change by inserting the test plate at four diagonal positions. When the color change of a crystal at a diagonal position resulting from 90-degree rotation exhibits no clear birefringence, the interference color chart was shown to be useless. We suggested the use of a compensator whose retardation can be changed to obtain an accurate value for the retardation of the crystal.

In situobservation of electric-field-induced domain switching near a crack tip in poled 0.62PbMg1∕3Nb2∕3O3–0.38PbTiO3 single crystal

An in situ polarized light microscopy observation of electric-field-induced domain switching near a crack tip in poled 0.62PbMg1∕3Nb2∕3O3–0.38PbTiO3 single crystal is reported. In-plane 90° domain switching is found to concentrate near the crack tip and the size of switching zone increases with the electric field. The polarization directions of switched domains, the positions, and width of 90° switching zones accord well with theoretical results based on the domain switching model by Hwang et al. [Acta Metall. Mater. 43, 2073 (1995)]. However, contradicting with this model, no explicit 180° domain switching ahead of the crack tip is observed.

Novel physically structured lipid matrices of beeswax and a homolipid from Capra hircus (goat fat): a physicochemical characterization for application in drug delivery

Lipid based materials are fast becoming the carrier of choice for delivery of new chemical entities and active agents. It is important to know the thermal characteristics, crystal habit, texture and appearance of a new lipid matrix when determining its suitability for use in pharmaceutical formulations. In this study, physically structured lipid matrices containing various proportions (25% w/w, 50% w/w and 75% w/w) of beeswax in a novel homolipid from Capra hircus (goat fat) were prepared by fusion, and subjected to thermal treatments in a differential scanning calorimeter (DSC) to obtain the thermal characteristics. Further characterization of the lipid matrices was performed by X-ray diffraction, polarized light microscopy (PLM) and transmission electron microscopy (TEM). Kinetics of crystallization of the molten lipid matrices was studied in an isothermal heat conduction microcalorimeter (IMC). Analysis of thermal data from DSC indicated that the physically structured lipid matrices revealed varied melting peaks between those of the pure lipids. PLM observation exhibited qualitatively different textures for the different structured lipid matrices. The lipid matrix containing 50% w/w of beeswax presented an interference at 2θ = 1.2° d = 73.63 A different from those of the two pure lipids. The lipid matrix containing 75% w/w of beeswax showed a change in crystallization behavior after 34 h. Crystallization kinetic analysis indicated that the structured lipid matrix containing 50% w/w beeswax possessed the highest Avrami kinetic exponent n. Results obtained indicated that mixtures of beeswax and goat fat produced matrices composed of mixtures of crystals alongside mixed crystals with imperfections necessary for increased drug loading and retention capacities. The matrix containing 50% w/w of beeswax possessed ideal crystal properties for the formulation of colloidal and microparticulate lipid drug carrier systems of drug delivery.

Effect of calcined temperature on the solubility of trace elements from Manifanshi

A medical stone manifanshi were researched by using polarized light microscopy, X-ray diffraction (XRD), and inductively coupled plasma atomic emission spectrometry (ICP-AES) methods. The XRD pattern of the raw Manifanshi indicates that it is daminantly composed of plagioclase, orthoclase, quartz, and that of the calcined Manifanshi at 1000°C shows that the distortion of crystal structure in both plagioclase and orthoclase takes place at the calcined temperature. The polarized light microscopy observation suggests that the Manifanshi is naturally weathered monzo-granite porphyry. Chemical analyses reveal that the Manifanshi contains a number of healthful trace elements and rare toxic trace elements, therefore, it is a high quality Manifanshi. The solubility of trace elements was determined by measuring the concentration of trace elements from Manifanshi calcined under varying temperature conditions by ICP method, the results suggest that the calcined product at 1000°C shows the ideal result in ionic concentrations and dissolution rate of trace elements in water, which is contributed to the distortion of the crystal structure of feldspar at the calcined temperature.

A critical study of novel physically structured lipid matrices composed of a homolipid from Capra hircus and theobroma oil

There is increasing interest in drug formulation using lipids. In this study, some physically structured lipid matrices were formulated and characterized for drug delivery applications. Lipid matrices containing a novel homolipid from Capra hircus (goat fat) and theobroma oil, at 25, 50 and 75% (w/w) concentration of the homolipid were formulated by fusion. The lipid matrices were subjected to some characterization procedures such as differential scanning calorimetry (DSC) to ascertain their supramolecular properties, small angle X-ray diffraction (SAXD), wide angle X-ray diffraction (WAXD), polarized light microscopy (PLM) and isothermal heat conduction microcalorimetry (IMC). The internal structures of some selected lipid matrices were also studied by freeze-fracture transmission electron microscopy (FFTEM). DSC results obtained indicated that goat fat has a pre-transition at 15.9 ± 0.2 °C (after 1 week) and melts completely with two detectable melting peaks at 33.0 ± 0.2 and 49.9 ± 0.1 °C, and total enthalpy of 99.9 ± 2.5 mJ/mg determined after 6 weeks of preparation. The melting enthalpy of goat fat changed after 3 weeks but remained constant after 6 weeks while the melting enthalpy of the lipid matrix containing 50% (w/w) goat fat changed after 3 and 6 weeks. An increase in lower melting peak was observed in the lipid matrix containing 25% (w/w) goat fat after 6 weeks. WAXD and SAXD of the physically structured lipid matrices showed reflections of the different pure lipids but new interferences were detected in WAXD mostly between 2 θ = 17.5° and 2 θ = 27.5°. PLM observation revealed the presence of Maltese crosses for the homolipid at 37 °C, which disappeared upon heating at 51.0 °C. PLM of the structured lipid matrix containing 25% (w/w) goat fat showed distinct crystal growth after 4 weeks among the admixtures. However, IMC studies did not reveal any change in recrystallization behaviour in this lipid matrix within 24 h. Analysis of the crystallization exotherms indicated that the lipid matrix containing 50% (w/w) goat fat showed unique crystallization kinetics and possessed the lowest Avrami exponent, while goat fat alone showed slight change within the first 45 min of isothermal crystallization. Physically structured lipid matrix containing 75% (w/w) goat fat possessed the lowest growth rate constant.

New Observation on Morphology of a Thermotropic Liquid Crystalline Polyesterimide Crystallized at High Temperature

The crystal morphology of a thermotropic liquid crystalline polyesterimide, derived from N, N′‐hexane‐1,6‐diylbis(trimellitimides), 4,4′‐dihydroxybenzophenone and p‐hydroxybenzoic acid, was investigated by means of polarized light microscopy (PLM) with a hot stage and scanning electron microscopy (SEM). The PLM observation indicates a series of phase transitions in the polyesterimide: with increasing temperature, the transformation from the amorphous state to nematic was observed at 264°C, followed by the conversion of nematic to isotropic melt at 290°C; crystallization in the isotropic phase occurred when the sample was maintained at 290°C on a glass substrate (only) for extended time. Very large and perfect Hedgehog spherulites were grown at 290°C with a fast growth rate. The SEM observation provided information on branching in crystals and spherulites impingement.

The strength of paraffin gels formed under static and flow conditions

When the temperature of a solution of paraffins in oil is dropped below the ‘cloud point’ temperature, the high molecular weight n -paraffin molecules precipitate out of solution, crystallize and form a gel. The gelation and concomitant deposition of these paraffin gels in crude oil pipelines poses a major transportation problem by reducing the flow efficiency. Implementation of mechanical methods of remediation of paraffin deposition requires knowledge of the gel strength. Rheometric studies were performed on a model system to study the yield strength of paraffin–oil gels formed under various shear and thermal histories. It was observed that when the gel was formed under quiescent (shut-in) conditions, the yield stress of the gel decreased with an increasing cooling rate. However, when a shear stress was exerted on the gel during cooling (as would be experienced in a flow line), the trend of the yield stress vs. cooling rate curve was strongly influenced by the magnitude of this shear stress. Additionally, experimentation over a range of applied shear stresses revealed that the yield stress of the gel reaches a maximum at a moderate value of the applied shear. These rheometric results are explained with the help of 3-D polarized light microscopy observations of the paraffin crystal structure formed under various shear and cooling conditions using static and flow cell systems. The effects of crystal size on the gel properties are enunciated.

Microscopy and microanalysis of crystalline glazes.

Crystalline glazes on ceramic plates produced commercially in the UK and on ceramic pots produced commercially in Taiwan and Spain have been examined by X-ray diffraction, conventional and polarized light microscopy, and scanning electron microscopy in order to identify the crystalline phases present in the glazes and to ascertain through X-ray microanalysis the partitioning behaviour of the transition metal ions used to colour the glazes and the crystals within them. In each case examined, the macroscopic two-dimensional spherulites within the glazes clearly seen by the naked eye were found to consist of large numbers of radially orientated acicular crystals each 5 micro m or less in width embedded within the silica-rich glaze. Energy dispersive X-ray microanalysis and X-ray diffraction of these crystals identified these crystals as willemite, alpha-Zn2SiO4. The strong [001] texture of these crystals within the glaze evident from the X-ray diffraction patterns was consistent with polarized light microscopy observations of the willemite crystals. In addition to willemite, small iron-doped gahnite (ZnAl2O4) crystals were found in a honey-coloured crystalline glaze and acicular rutile (TiO2) crystals were found in the Portmeirion Pottery plates examined. Transition metal ions with a preference for tetrahedral coordination were observed to substitute for Zn2+ ions in willemite and to partition preferentially to the willemite crystals, whereas ions preferring octahedral coordination preferred to remain in the glaze.

Synthesis and thermotropic liquid‐crystalline behavior of novel main‐chain poly(aryl ether ketones)

AbstractNovel aromatic poly(ether ketones) containing bulky lateral groups were synthesized via nucleophilic substitution reactions of 4,4′‐biphenol and (4‐chloro‐3‐trifluoromethyl)phenylhydroquinone (CF‐PH) with 1,4‐bis(p‐fluorobenzoyl)benzene. The copolymers were characterized by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction, and polarized light microscopy observation. Thermotropic liquid‐crystalline behavior was observed in the copolymers containing 40, 50, 60, and 70 mol % CF‐PH. The crystalline–liquid‐crystalline transition [melting temperature (Tm)] and the liquid‐crystalline–isotropic phase transition appeared in the DSC thermograms, whereas the biphenol‐based homopolymer had only a melting transition. The novel poly(aryl ether ketones) had glass‐transition temperatures that ranged from 143 to 151°C and lower Tm's that ranged from 279 to 291°C, due to the copolymerization. The polymers showed high thermal stability, and some exhibited a large range in mesophase stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1347–1350, 2003

Synthesis and rheological investigation on phase behaviors of semiflexible type amorphous liquid crystalline poly(ester-imide)s

Main chain type thermotropic poly(ester-imide)s composed of N-(ω-carboxyalkylene) trimellitic imides and methylhydroquinone diacetate or hydroquinone diacetate were prepared by melt transesterification condensation. DSC and polarized light microscopy observation revealed that polymers made from hydroquinone diacetate showed both crystal melting and mesophase to isotropic phase transition but those from methylhydroquinone diacetate showed only mesophase to isotropic phase transition. The amorphous type liquid crystalline polymers showed extremely slow crystallization velocities. The mesophase of all polymers was verified as a nematic one from the drops of moduli and viscosities at the isotropic to mesophase transition during cooling. For an amorphous liquid crystalline polymer the changes of dynamic rheological properties were checked around the mesophase to isotropic phase transition. Both isotropic and nematic phases succeeded in time–temperature superposition but biphase failed.

Crystallization behavior of polypropylene in polypropylene/nylon 6 blend

This article describes the crystallization behavior of polypropylene (PP) in the presence of a crystallizable polymer, namely, nylon 6, in the binary blend of PP/nylon 6 in the composition range from 0 to 30 wt % of nylon 6 content in the blend. The crystallization behavior was studied through variation of the crystallinity with the blend composition and changes in the crystallization exotherms were recorded by differential scanning calorimetry (DSC) and the spherulite morphology was observed via polarized light microscopy (PLM). Comparison of the crystallization exotherms and melting endotherms revealed some differences which are attributed to the role of a sufficiently high thermal energy of the nylon 6 crystals on the melting of PP. The crystallinity of PP decreased in the presence of nylon 6, whereas the crystallinity of nylon 6 increased considerably in the presence of PP. The rate of nucleation of PP on addition of nylon 6 decreased rapidly in the region 0–10 wt % nylon 6 content, and, thereafter, at a higher nylon 6 content, decrease of the nucleation rate was relatively slow. PLM observation revealed the presence of composite spherulites with PP spherulites grown on the surface of the already-formed nylon 6 spherulites. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1153–1161, 1999

Plastic anisotropy and cracking at hardness impressions in single crystal ammonium perchlorate

Diamond pyramid (Vickers) microindentation hardness testing was used to investigate the plastic deformation and cracking behaviors of single crystal ammonium perchlorate (AP). Traces of slip planes and cracks formed at hardness impressions in ( 210) and (001) cleavage surfaces were analyzed on a stereographic projection basis. Indentation-forming (primary deformation) and volume-accommodating (secondary deformation) slip systems were identified, including a number of systems not reported previously. Cleavage cracks were observed to form in the regions of greatest plastic deformation and are explained in terms of specific dislocation pile-up reactions at intersecting slip systems that are strongly surface orientation dependent. Also polarized light microscopy observations have revealed far-reaching residual strains extending beyond crack tips at impressions put into the ( 210) surface, thus giving additional evidence of the wedge-opening action of dislocation pile-ups. Prominent two-fold symmetric troughs extending from impressions put into the (001) surface are attributed to the unique characteristic of outward movement by indentation-forming dislocations. An important connection is made between the identified orthorhombic slip systems and those representative of the higher-temperature rocksalt (cubic) structural form of AP.

High-performance aromatic polyimide fibres

A new polyimide has been synthesized from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 2,2′-dimethyl-4,4′-diaminobiphenyl (DMB). A high-strength, high-modulus, high-temperature fibre has been developed from this polyimide via a dry-jet wet spinning method. The tensile strength of BPDA-DMB fibres is 3.3 GPa and the tensile modulus is around 130 GPa. The compressive strength of the fibres has been investigated through a tensile recoil test (TRT), while the fibre morphology after compression has been studied via polarized light microscopy (PLM) and scanning electron microscopy (SEM). From the TRT measurements, we have observed that the compressive strength of this fibre is 665 (±5) MPa, which is higher than those of other aromatic polymer fibres. The effect of fibre diameter on the compressive strength of BPDA-DMB fibres is not substantial. The critical compressive strain for this fibre at which the kink bands start appearing under the observation of PLM is at 0.51–0.54%. Subglass relaxation processes have been observed and the measure of an apparent relaxation strength may serve as one of the factors which significantly affect the compressive strength of the fibres. Tensile tests of pre-compressed fibres reveal a continuous loss in tensile strength (up to 30%) with increasing the compressive strain (up to 2.6%). PLM and SEM observations show that during the compression BPDA-DMB fibres form regularly-spaced kink bands at ±60 ° (±2 °) with respect to the fibre axis. The kink band density initially increases with the compressive strain, and reaches a maximum at around 1.1%. Further increase of the compressive strain decreases this density due to the merge of the neighbouring bands. The size of kink bands also correspondingly increases within this compressive strain region. The morphological observation via SEM implies the existence of a skin-core structure and microfibrillar texture which are common features in polymer fibres.