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The aim of this project was to study the efficacy of current methods of quality control and quality assurance for ultra-high molecular weight polyethylene (UHMWPE) products, and find improvements where possible. Intrinsic viscosity (IV) tests were performed on three grades of polyethylene with weight average relative molar masses M ̅ $̅{M}$ w of about 6 × 105, 5.0 × 106 and 9.0 × 106. Results from three laboratories showed substantial scatter, probably because different methods were used to make and test solutions. Tensile tests were carried out to 600 % extension at 150 °C under both constant applied load and constant Hencky strain rate, on compression mouldings made by a leading manufacturer of ultra-high molecular weight polyethylene. They gave low values of M ̅ $̅{M}$ w, suggesting incomplete entanglement at ‘grain boundaries’ between powder particles. Results from conventional melt-rheology tests are presented, and their relevance to quality control and assurance is discussed. Attempts to calculate molecular weights from these data met with limited success because of extended relaxation times. Suggestions are made for improving international standards for IV testing of UHMWPE, by investigating the various factors that can cause significant errors, and by introducing methods for checking the homogeneity (and hence validity) of the solutions tested. Part 2 addresses characterization of crystallinity and structure. Part 3 covers mechanical properties, and Part 4 focuses on the sporadic crack propagation behaviour exhibited by all three grades of UHMWPE in fatigue tests on 10 mm thick compact tension specimens.

Three grades of polyethylene, with weight-average relative molar masses, M ‾ W ${\bar{M}}_{\text{W}}$ , of approximately 0.6 × 106, 5 × 106, and 9 × 106, were supplied as compression mouldings by a leading manufacturer of ultra-high molecular weight polyethylene (UHMWPE). They were code-named PE06, PE5, and PE9, respectively. Specimens cut from these mouldings were subjected to a wide range of mechanical tests at 23 °C. In tensile tests, deformation was initially elastic and dominated by crystallinity, which was highest in PE06. Beyond the yield point, entanglement density became the dominant factor, and at 40 % strain, the rising stress–strain curves for PE5 and PE9 crossed the falling PE06 curve. Fracture occurred at strains above 150 %. Differences in stress–strain behaviour between PE5 and PE9 were relatively small. A similar pattern of behaviour was observed in wear tests; wear resistance showed a marked increase when M ‾ W ${\bar{M}}_{\text{W}}$ was raised from 0.6 × 106 to 5 × 106, but there was no further increase when it was raised to 9 × 106. It is concluded that the unexpected similarity in behaviour between PE5 and PE9 was due to incomplete consolidation during moulding, which led to deficiencies in entanglement at grain boundaries; they were clearly visible on the surfaces of both tensile and wear specimens. Fatigue crack growth in 10 mm thick specimens was so severely affected by inadequate consolidation that it forms the basis for a separate report – Part 4 in this series.

Test methods including OM, SEM, TEM, DSC, SAXS, WAXS, and IR were used to characterise supra-molecular structure in three batches of polyethylene (PE), which had weight-average relative molar masses M ¯ w ${\overline{M}}_{\text{w}}$ of approximately 0.6 × 106, 5 × 106, and 9 × 106. They were applied to compression mouldings made by the polymer manufacturer. Electron microscopy showed that powders formed in the polymerization reactor consisted of irregularly shaped grains between 50 and 250 μm in diameter. Higher magnification revealed that each grain was an aggregate, composed of particles between 0.4 and 0.8 μm in diameter, which were connected by long, thin fibrils. In compression mouldings, lamellar thicknesses ranged from 7 to 23 nm. Crystallinity varied between 70 and 75 % in reactor powder, but was lower in compression mouldings. Melting peak temperatures ranged from 138 to 145 °C, depending on processing history. DMTA showed that the glass transition temperature θ g was −120 °C for all three grades of polyethylene. IR spectroscopy found negligibly small levels of oxidation and thermal degradation in mouldings. Optical microscopy revealed the presence of visible fusion defects at grain boundaries. It is concluded that relatively weak defects can be characterized using optical microscopy, but there is a need for improved methods that can detect less obvious fusion defects.

Fatigue tests were carried out on compression mouldings supplied by a leading polymer manufacturer. They were made from three batches of ultra-high molecular weight polyethylene (UHMWPE) with weight-average relative molar masses, M ¯ W ${\overline{M}}_{\mathrm{W}}$ , of about 0.6 × 106, 5 × 106 and 9 × 106. In 10 mm thick compact tension specimens, crack propagation was so erratic that it was impossible to follow standard procedure, where crack-tip stress intensity amplitude, ΔK, is raised incrementally, and the resulting crack propagation rate, da/dN, increases, following the Paris equation, where a is crack length and N is number of cycles. Instead, most of the tests were conducted at fixed high values of ΔK. Typically, da/dN then started at a high level, but decreased irregularly during the test. Micrographs of fracture surfaces showed that crack propagation was sporadic in these specimens. In one test, at ΔK = 2.3 MPa m0.5, there were crack-arrest marks at intervals Δa of about 2 μm, while the number of cycles between individual growth steps increased from 1 to more than 1000 and the fracture surface showed increasing evidence of plastic deformation. It is concluded that sporadic crack propagation was caused by energy-dissipating crazing, which was initiated close to the crack tip under plane strain conditions in mouldings that were not fully consolidated. By contrast, fatigue crack propagation in 4 mm thick specimens followed the Paris equation approximately. The results from all four reports on this project are reviewed, and the possibility of using fatigue testing as a quality assurance procedure for melt-processed UHMWPE is discussed.

Historischer Uberblick zur Entwicklung der Lichtmikroskopie und die fruhen Jahre der Elektronenmikroskopie; Abbesche Formel zur Auflosung von Mikroskopen.

Bildverarbeitung und Bildanalyse dienen einer verbesserten Darstellung von Strukturen und deren quantitativen Auswertung einschlieslich der raumlichen Strukturanalyse. Methoden der Bildsimulation sind insbesondere zur Interpretation von Hochstauflosungsaufnahmen erforderlich.

Ubersicht zu den Hauptrichtungen der Elektronenmikroskopie und zu den Anforderungen an die zu untersuchenden Proben. Darstellung der Transmissions-Elektronenmikroskopie (TEM) einschlieslich der Hochstspannungs-TEM, Hochstauflosungs-TEM und Analytischen TEM, der Techniken der Raster-Elektronenmikroskopie (REM), der Emissions-Elektronenmikroskopie und der Rastersondenmikroskopie, jeweils mit Beschreibung der Kontrastentstehung in den Aufnahmen und illustriert durch charakteristische Bildbeispiele. Ein Hinweis auf die in-situ Mikroskopie schliest das Kapitel ab.

Atomic force microscopy (AFM), also commonly known as scanning force microscopy, has evolved as an extremely useful tool for the study of the structure and properties of nanostructured systems including nanoparticles (NPs), composites, and soft matters such as polymers and biological tissues. In particular, AFM serves as an excellent complement to electron microscopic techniques, on one hand, and represents a unique tool to study the physical and functional properties of heterogeneous systems on the nanoscale on the other. The aim of this chapter is to elucidate the contribution of AFM to the structural characterization of nanomaterials with an introduction to the principles of the basic AFM techniques and sample preparation methods. A comparison with electron microscopy will also be presented, selecting some illustrative examples of imaging of NPs, soft matter, and composites. We demonstrate that AFM can conveniently be used not only to image the morphology of the materials with nanometer resolution but also to gain insight into the manipulation of the NPs in a controlled manner.

Summary A star shaped polystyrene-block-polybutadiene-block-polystyrene (SBS) block copolymer was subjected to epoxidation reaction using different reagents such as m-chloroperoxy benzoic acid (MCPBA), peracetic acid (PAA), performic acid (PFA) and hexaflouro-isopropanol (HFIP). All the methods led to the targeted modification of the block copolymer satisfactorily, some of them also accompanying rapid side reactions. The epoxidized polymer was then blended with epoxy resin comprising diglycidyl ether of bisphenol-A in presence of methylene dianiline (MDA) as hardener. The mixing of the epoxidized block copolymer into the epoxy resin led to the formation of well dispersed uniform blend morphology and imparted enhanced thermostability and ductility to the blends. A brittle-to-ductile transition was observed in the blends.

The aim of this work is to study the morphological changes after alkali treatment and functionalisation of cellulosic materials present in crude bamboo and sisal flours using ionic liquid as solvents. The flours of bamboo (BF) and sisal (SF) were subjected to acetylation and silylation using acetic anhydride (AA) and hexamethyldisilazane (HMDS) as reagents. The changes in fibres structure and morphology were studied by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) respectively. The results indicate that crude BF and SF are functionalised successfully which is confirmed by FTIR spectra and the solubility of the derivatives in different solvents. The microscopic structures of the cellulose microfibre bundles become more distinct after delignification

The nanocomposites based on sulfonated ethylene/1-octene copolymer (sEOC) and organophilic modified layered silicate were synthesized. The morphology of the ionomeric product was studied with the help of Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Fourier Transform Infrared (FTIR) spectroscopy and microhardness measurements. It was shown that via the solution cast technique, the nanocomposite with uniformly distributed filer morphology can be conveniently prepared. The significant enhancement of the mechanical properties due to ionomerization was attested with the help of depth sensing microhardness measurements. It was found that the hardness of ionomer nanocomposite comprising 5 wt.-% layered silicate is approximately four fold of the neat elastomer. DOI: http://dx.doi.org/10.3126/jncs.v28i0.8060 Journal of Nepal Chemical Society Vol.28, 2011 Page : 59-66 Uploaded date : May 7, 2013

Morphological analysis of nanocomposites of polyethylene glycol (PEG) based polyurethanes (TPU) and polyhedral oligomeric silsesquioxanes (POSS) were performed using different techniques (transmission electron microscopy, small and wide X-ray scattering, differential scanning calorimetry) as a function of molecular weight of PEG and the PEG/POSS mole ratio. A strong interdependence in crystallisation behaviour between the two crystals species, i.e. the POSS nanocrystals about 5 nm in size and the crystals in the semicrystalline soft phase of TPU, were found. The mechanical properties (Vickers hardness under load and elastic modulus) determined using recording microindentation techniques at room temperature were significantly improved by POSS for two material formulations. Based on the results of polymethylmethacrylate (PMMA)/silica (SiO2) nanocomposites containing up to 20 wt.-% well-dispersed spherical silica nanoparticles, it has been shown that the indentation fracture mechanics is a straightforward, costand time-effective, powerful tool to analyse the fracture resistance for the novel polymer materials, such as brittle nanostructured polymer-ceramic hybrids. Nepal Journal of Science and Technology Vol. 13, No. 2 (2012) 115-122 DOI: http://dx.doi.org/10.3126/njst.v13i2.7723

PART I: Structural and Morphological Characterization The Morphology of Crystalline Polymers D.C. Bassett Nanostructure Development in Semicrystalline Polymers during Deformation by Synchrotron X-Ray Scattering and Diffraction Techniques B.S. Hsiao Nanostructures of Two-Component Amorphous Block Copolymers: Effect of Chain Architecture R. Adhikari and G.H. Michler PART II: Deformation Mechanisms at Nanoscopic Level Crazing and Fracture in Amorphous Polymers: Micromechanisms and Effect of Molecular Variables H.H. Kausch and J.L. Halary Strength and Toughness of Crystalline Polymer Systems A. Galeski Microdeformation and Fracture in Semicrystalline Polymers Christopher J.G. Plummer Micromechanical Deformation Mechanisms in Polyolefins: Influence of Polymorphism and Molecular Weight S. Henning and Goerg H. Michler Micro-Indentation Studies of Polymers Relating to Nanostructure and Morphology F.J. Balta Calleja, A. Flores, and F. Ania Micromechanics of Particle-Modified Semicrystalline Polymers: Influence of Anisotropy Due to Transcrystallinity and/or Flow J. A. W. van Dommelen and H. E. H. Meijer Micromechanical Mechanisms of Toughness Enhancement in Nanostructured Amorphous and Semicrystalline Polymers G.H. Michler PART III: Mechanical Properties Improvement and Fracture Behavior Structure-Property Relationship in Rubber Modified Amorphous Thermoplastic Polymers W. Heckmann, G.E. McKee, and F. Ramsteiner Deformation Mechanisms and Toughness of Rubber and Rigid Filler Modified Semicrystalline Polymers C. Harrats and G. Groeninckx Structure-Property Relationships in Nanoparticle/Semicrystalline Thermoplastic Composites J. Karger-Kocsis and Z. Zhang Carbon Nanotube and Carbon Nanofiber-Reinforced Polymer Composites K. Schulte and M.C.M. Nolte Nano- and Microlayered Polymers: Structure and Properties T.E. Bernal-Lara, A. Ranade, A. Hiltner, and E. Baer High Stiffness and High Impact Strength Polymer Composites by Hot Compaction of Oriented Fibers and Tapes P.J. Hine, and I.M. Ward Index

Aiming at development of completely biodegradable composite materials based on locally available low-cost bamboo flour (BF) as filler, structure properties correlations in aliphatic–aromatic copolyester/BF composites fabricated by melt mixing have been studied by means of different techniques such as electron microscopy, X-ray diffraction, tensile testing, and thermogravimetric analysis (TGA). It has been demonstrated that the BF can be successfully incorporated homogeneously into the biodegradable polymeric matrix up to high content. The filler weakly adheres to the matrix as demonstrated by the pulling up of bamboo fibers on the electron micrographs and further attested by TGA. At high filler concentration, the polymer acts merely as binding material. The semicrystalline framework of the matrix polymer is hindered by the presence of the fibers, the structural changes being more pronounced at the surfaces than in the bulk, which indicates preferential segregation of the fibers toward the specimen surface. This opens new possibilities for a more detailed engineering of materials surfaces. The mechanical properties of the composites are suited for low-load-bearing applications. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

The contribution describes the development of a biocompatible nanocomposite material consisting of a resorbable polymeric matrix and osteoinductive nanoparticles that can be used to manufacture compact products, porous scaffolds, hybrid nanofibers, and alternating porous/compact structures. It is shown that the material has a good balance of stiffness, strength and toughness. The material supports osteoblast proliferation. Based on a modular design principle, several prototypes for hierarchical 3D constructs are proposed.

Nanofibers were prepared by electrospinning from pure polyvinyl alcohol (PVA), polyhydroxybutyrate (PHB), and their blends. Miscibility and morphology of both polymers in the nanofiber blends were studied by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC), revealing that PVA and PHB were miscible with good compatibility. DSC also revealed suppression of crystallinity of PHB in the blend nanofibers with increasing proportion of PVA. The hydrolytic degradation of PHB was accelerated with increasing PVA fraction. Cell culture experiments with a human keratinocyte cell line (HaCaT) and dermal fibroblast on the electrospun PHB and PVA/PHB blend nanofibers showed maximum adhesion and proliferation on pure PHB. However, the addition of 5 wt % PVA to PHB inhibited growth of HaCaT cells but not of fibroblasts. On the contrary, adhesion and proliferation of HaCaT cells were promoted on PVA/PHB (50/50) fibers, which inhibited growth of fibroblasts.

Nanostructured polymers and ultra-thin polymer layers are used more and more in technical applications like nanotechnology and microelectronics. Theretore, it is really important to understand the size-scale dependent properties as bulk polymers become thinner and more two-dimensional. Here the morphology as well as the macroscopic and the microscopic deformation behaviour of multilayered films of polypropylene (PP) and polystyrene (PS) have been investigated. For investigation different microscopic techniques and tensile testing were used. The films were prepared by multilayer coextrusion, whereas the composition of PP and PS and the film thickness ― and therefore the thickness of each layer ― varied. The thinnest calculated thickness of a single layer was about 5 nm. It is shown that the PP/PS films consist usually of homogeneous layers with only few defects. As the composition of PP/PS deviates strongly from 50/50 or the films get thinner the number of defects increases and the layered system turns to irregular lamellar system. In macroscopic tensile tests the small PS layers affect the elongation at break enormously: Most of the samples are brittle. For the films with a composition of PP/PS 90/10 and the film PP/PS 70/30 with a film thickness of 25 μm an elongation at break of 66% and higher could be reached. Transmission electron microscopy on these samples shows that the layers are characterized by plastic yielding in local deformation zones.

Polypropylene samples in a wide molecular weight range between approx. 100 kg/mol to 1600 kg/mol were processed by injection molding to thin walled micro specimens with respect to study shear induced crystallization phenomena under high shear rate and subsequently possible self reinforcement effects. The specimens nano structures were investigated and related deformation behavior under tensile studied. Novel morphologies have been detect and their micromechanical mechanism interpret and summarized.

The treatment of bone and cartilage defects with bioengineered constructs of artificial scaffolds and autogenous cells became the main challenge of contemporary regenerative medicine. Early defect repair may prevent secondary injury. Recent studies could prove that bone and cartilage cells are sensitive to microscale and nanoscale patterns of surface topography and chemical structure. Nanostructured materials provide an environment for tissue regeneration mimicking the physiological range of extracellular matrix. The article reviews several studies substantiating the superiority of nanostructured materials for bone and cartilage repair along with own results on cell attachment.

Mixtures of polystyrene-block-polyisoprene-block-polystyrene (SIS) triblock copolymer and various styrenic block copolymers (having diblock and triblock architectures) as well as polystyrene homopolymer (PS) were prepared via solution blending to determine the influence of molecular coupling on the large strain mechanical performance of the block copolymers. The techniques used were transmission electron microscopy (TEM) as well as scanning electron microscopy (SEM) for the morphological characterization and uniaxial tensile testing for the determination of mechanical properties. In the block copolymer blends, it was possible to tailor the mechanical properties as long as the molecular coupling was present among the outer polystyrene blocks. The mechanical performance of the triblock copolymer was found to deteriorate by the presence of dangling chains in the microphase-separated domains. In the blends comprising an SIS triblock copolymer and polystyrene homopolymers, the macrophase-separated compounds containing PS having molar mass exceeding the entanglement molar mass showed the optimum mechanical properties. The observed mechanical behaviour has been correlated with the fracture surface morphology of the corresponding blends.

Summary: With the aid of layer multiplying coextrusion techniques, polymer composites comprising up to thousand of uniform and alternating layers polyethylene terephthalate (PET) and polycarbonate (PC) were produced. Morphology and micromechanical deformation processes in these composites were investigated by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM). In particular, the effect of thickness of individual layers on the large strain deformation micromechanisms was analyzed. On decreasing the thickness of individual polymer layers, a transition in deformation mechanism from two-component behaviour (i.e. the localization of shear bands in individual layer) to one-component-like behaviour (with the shear bands passing unhindered through different layers) was observed at the layer thickness of ca. 1 µm. On further decreasing the layer thickness below 100 nm, the composites exhibited homogeneous plastic deformation (i.e. no localization of deformation). In contrast to pure PET, even after long annealing, the composites showed tough behaviour during tensile loading.

Polyvinyl alcohol (PVA) nanofibers, PVA/Type I Collagen (Col) and their composites with hydroxyapatite nanoparticles (nano-HAp) were prepared by electrospinning techniques. The composite nanofibrous membranes were subjected to detailed analysis. Morphological investigations show that the generated nanofibers (NFs) have uniform morphology with an average diameter of ∼160 nm for pure PVA, ∼176 nm for PVA/n-HAp, ∼245 nm for PVA/Col and ∼320 nm for PVA/Col/n-HAp. It is of interest to observe that large numbers of HAp nanorods are preferentially oriented parallel to the longitudinal direction of the electrospun PVA and/or PVA/Col NFs. FTIR and thermal analysis demonstrated that there was strong intermolecular hydrogen bonding between the molecules of PVA/Col/n-HAp. Furthermore, the obtained PVA/Col/nHAp NFs scaffold (7 cm × 11 cm) has a porous structure with adjustable pore size and shape. The pore size is in the range of 650 μm with a porosity of 49.5%. On the other hand, mechanical characterizations revealed that the incorporating of 5 wt% n-HAp into the matrix of PVA/Col nanofibers could significantly improve the rigidity of the resultant biocomposite nanofibrous scaffold. These results strongly suggest a huge potential of the prepared scaffold for bone tissue engineering.

Hydroxyapatite has become the most common material to replace bone or to guide its regeneration. Nanocrystalline hydroxyapatite suspension had been introduced in the clinical use recently under the assumption that small dimension of crystals could improve resorption. We studied the resorption and osteointegration of the nanocrystalline hydroxyapatite Ostim in a rabbit model. The material was implanted either alone or in combination with autogenic or allogenic bone into distal rabbit femora. After survival time of 2, 4, 6, 8 and 12 weeks the implants had been evaluated by light and electron microscopy. We observed a direct bone contact as well as inclusion into soft tissue. But we could observe no or only marginal decay and no remarkable resorption in the vast majority of implants. In situ the nanocrystalline material mostly formed densely packed agglomerates which were preserved once included in bone or connective tissue. A serious side effect was the initiation of osteolysis in the femora far from the implantation site causing extended defects in the cortical bone.

The development of the morphology and the alignment of lamellae in melt elongation of blends of an asymmetric linear styrene-butadiene block copolymer (LN3) and polystyrene (PS 158K) was investigated. PS 158K and LN3 formed two-phase polymer blends with PS 158K resp. LN3 inclusions, depending on the concentration of polystyrene. The block copolymer was arranged in a lamellar phase with a lamellae thickness of ∼ 13 nm. Our rheological experiments revealed that the complex modulus, the elongational viscosity and the recovered stretch of the blends primarily resulted from a superposition of the properties of the blend components. In melt elongation, pure LN3 started to crumple at a small Hencky strain. In the blends, the presence of the PS 158K inclusions led to a macroscopically more uniform elongation, but with an anisotropic Poisson ratio. The LN3 inclusions in the PS 158K matrix were deformed into a filament-like shape. In the blends with a LN3 matrix the alignment of the block copolymer lamellae parallel to the loading direction increased with applied extensional strain. In the latter case, the lamellae thickness did not decrease significantly. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Pure anatase TiO2 submicrotubes were successfully fabricated by a template-directed method. Electrospun poly(vinyl pyrrolidone) (PVP) fibers were used as a soft template for coating with titanium dioxide using an atomic layer deposition (ALD) technique. The deposition was conducted onto a template at 70 °C by using titanium tetraisopropyl oxide (TIP) [Ti(OiPr)4] and pure water as precursors of TiO2. Crystalline structure, microstructure, and optical properties of the TiO2 deposited layers before and after calcination were studied in detail. While the as-deposited TiO2 layers onto ES fibers were completely amorphous with thickness of about 60 nm, the TiO2 layers after calcination at 500 °C for 4 h were properly converted into polycrystalline nanostructured TiO2 submicrotubes with high quality of anatase. Thereby, the optical band gap energy was also tuned with a blue shift. As final products the self-supported free-standing mats consisting of pure anatase TiO2 submicrotubes can be easily handled and reclai...

It has been known for more than 20 years that, in crazes of polystyrene (PS), the craze fibrils show a very high ductility with elongations at break up to 300%. Later, a similarly high ductility was found in laminated multilayer tapes and in styrene‐butadiene‐styrene (SBS) block copolymers with an arrangement of very tiny PS lamellae. In both cases the widths of the highly ductile PS parts were in the range of 20–30 nm. This effect of “fibril yielding” or “thin layer yielding” is discussed in light of the entanglement network model of amorphous polymers, developed originally to explain the fibrillar structure of PS crazes. An analysis shows that the condition for homogeneous yielding of brittle polymers is fulfilled if the strands or layers have thicknesses less than two‐times the entanglement mesh size (30 nm in PS). In such structures, a coherent entanglement network exists only in the length direction and, if it is loaded, no constraints (due to lateral entanglements) can hinder stretching. Since, in t...

Chevron morphology was observed using transmission electron microscopy in various semicrystalline polymers deformed in tensile experiments. The morphological and mechanical prerequisites for chevron structure formation in semicrystalline polymers were revealed. It was demonstrated that chevron folding is a common deformation mode which can appear in real, i.e. globally unoriented or partially oriented samples, in areas where the lamellar stacks are oriented perpendicular to the deformation direction. Similarities with the behaviour of other layered systems were found. The mechanism of chevron formation is discussed in the light of the fundamental statements of the folding theories and is related to the specific microstructure of the polymers. The effect of boundary conditions, deformation temperature and macroscopic strain on the characteristics of the chevron structure is described.

The present study attempts to find out the similarity and dissimilarity in structure and mechanical properties of PA6 deformed by channel die compression and by a new method combining the compression and rolling and which is known as rolling with side constraints. The resulting materials were characterized by texture investigation by WAXD and SAXS while mechanical properties by tensile tests and DMTA. The fractured surfaces of rolled samples at high deformation ratio was visualized by using SEM. The present study indicates that the crystalline texture and lamellar structure of PA6 samples after the deformation by the two methods are similar at the corresponding strains, some differences develop at a hardening stage at which the time allowed for creep under load plays an important role. Above the compression ratio of 1.8 an intense shear banding occurs at ±45°. With further deformation to compression ratio of 4.0 the shear band planes are tilted 20–26° from the flow direction only. In association with the appearance of shear bands a fraction of γ-form crystals is generated which are oriented with macromolecular chain axes along shear planes and in the direction of shear. Those γ-crystals are misaligned with α-crystals that are deformed and oriented along the flow direction. The bifurcation of orientation of α- and γ-crystals is a reason of a unique fracture behavior of highly oriented samples: fracture occurs along shear planes with γ-crystals and fracture surfaces are nearly flat.

Based on the results from agglomerate-free PMMA nanocomposites with 10 and 20 wt.-% spherical SiO 2 nanoparticles, it has been shown that indentation fracture mechanics is a straightforward, powerful, cost-effective and time-effective tool for analyzing the fracture resistance of novel polymer materials, such as brittle nanostructured polymer-ceramic hybrids. In contrast to pure PMMA, the R-curve effect, i.e., the enhancement in crack resistance as function of crack size, was not observed in the nanocomposites investigated. Fracture toughness was found to depend on the SiO 2 nanoparticle content, and the maximum value was observed at 10 wt.-%. A significant reduction in fracture toughness occurred at 20 wf.-% SiO 2 nanoparticles, which is associated with a percolation of the bound layers (interfacial layers) around the SiO 2 particles. From DSC data, the thickness of the interfacial polymer layer was estimated to be about 9 nm.

Using different microscopic techniques, we investigate the morphology and the micro-deformation processes in two entirely different classes of polymer based composites: natural biocomposites and synthetic polymer composites. The emphasis has been put on the comparison of the micromechanical properties of those composite materials. In the natural layered composites exemplified by human cortical bone, analogous to the synthetic glassy polymers, craze-like deformation zones were formed. A strong dependence of deformation mechanisms (such as transition from formation of single crazes to multiple crazing behaviour) on the layer dimension was observed in the layered composites made up of different amorphous polymers.

The relationship between the morphology and the mechanical properties of nanostructured blends,comprising an asymmetric styrene/butadiene star block copolymer,exhibiting cocontinuous-like morphology and low molar mass homopolymers, was studied by electron microscopy, microindentation hardness, and tensile testing methods. Results show that the deformation behavior of these systems is significantly modified by the presence of unentangled homopolymer chains, leading partly to a decrease in mechanical properties. In contrast to common polymer blends, in which usually, the hardness values do not markedly deviate from the additivity law, the H-values in the system investigated show large deviations from the linear additivity behavior. The observed anomalous behavior is discussed in terms of the enhanced local flow processes induced by the phase-separated morphology at a nanometer scale.

The morphology formation in the blends comprising a high density polyethylene (HDPE) and selected ethylene/1-octene copolymers (EOCs) was studied with variation of blend compositions using atomic force microscopy (AFM). The binary HDPE/EOC blends studied showed well phase-separated structures (macrophase separation) in consistence with individual melting and crystallization behavior of the blend components. For the blends comprising low 1-octene content copolymers, the lamellar stacks of one of the phases were found to exist side by side with that of the another phase giving rise to leaflet vein-like appearance. The formation of large HDPE lamellae particularly longer than in the pure state has been explained by considering the different melting points of the blend components. The study of strain induced structural changes in an HDPE/EOC blend revealed that at large strains, the extensive stretching of the soft EOC phase is accompanied by buckling of HDPE lamellar stack along the strain axis and subsequent microfibrils formation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1887–1893, 2007

The morphology and mechanical properties of nylon (copolyamide 6/66)/ acrylonitrile-butadiene rubber (NBR) blends have been studied with special reference to the effect of blend ratio and crosslinking systems. Morphological investigations of the blends using scanning and transmission electron microscopies show that a uniform and finer dispersion of the elastomer phase is achieved by dynamic crosslinking. The effects of various crosslinking systems such as sulphur and dicumyl peroxide on the morphology and mechanical properties of these blends were analysed. Morphological stability of the blends upon annealing has been investigated and the mechanical properties of the blends have been discussed. Attempts have been made to correlate the morphology with the mechanical properties of the dynamically vulcanized blends. The stability of the blend morphology during annealing has been examined.