Orientation distribution in the noncrystalline regions of biaxially drawn poly(ethylene terephthalate) film: A chain-intrinsic fluorescence study

We have studied development of the in-plane distribution of “amorphous orientation” during sequential and simultaneous biaxial drawing of poly(ethylene terephthalate) film, using polarized intrinsic fluorescence. The machine direction (MD) draw ratio was always fixed at 3.5, and the transverse direction (TD) draw ratio was varied. The rate of increase in the proportion of TD-oriented chains with increasing TD draw ratio is almost identical in the sequential and simultaneous processes up to a draw ratio of 2.7. At this point, sequential drawing starts to involve transverse realignment of MD-oriented chains, which accelerates redistribution of orientation from the MD to the TD. Consequently, in sequential drawing, a “balanced” biaxial orientation distribution is achieved at a TD draw ratio significantly below the MD draw ratio, whereas at the same TD draw ratio in the simultaneous process, MD orientation remains dominant. At equal MD and TD draw ratios, the non-crystalline chains in sequentially drawn film are predominantly oriented along the TD, but their orientation distribution is isotropic in simultaneously drawn film. High-temperature annealing at fixed dimensions diminishes the proportion of TD-oriented chains in films with transverse draw ratios < 2.5. We attribute this to a more highly developed crystallite network in the MD, which constrains orientational relaxation along the MD. A balanced distribution of amorphous orientation is directly responsible for achieving balanced tensile strength and balanced extensibility. © 1993 John Wiley & Sons, Inc.     

The role of patch hybridization on tensile response of cracked panel repaired with hybrid composite patch: experimental and numerical investigation

ABSTRACT

This article presents a distinct perspective of structural repair by bonding the hybrid composite patch. A novel hybrid composite patch is prepared from the carbon and glass fibers to repair the cracked panel. Different volume fractions of constituents are maintained to prepare the composite patch with varying stiffness. The elastic constant of the composite patch is derived by applying the rule of hybrid mixture and modified Halpin Tsai equation. The stress intensity factor in the panel and interfacial stresses in the adhesive layer are evaluated to assess repair efficiency and repair durability. Effects of the elastic modulus of the adhesive on the performance of composite patch repair are demonstrated. The load carrying capacity and failure strength are examined for variation in patch stiffness. The disbonded surface morphology is investigated through scanning electron microscopy after failure. The results reveal that the hybrid composite patch provided sufficient reinforcement to reduce the stress intensity and interfacial stresses. Patch hybridization has offered a pragmatic solution and proposed as an alternative patch material to repair the cracked structure.     

Mechanical properties and morphology of PP/ABS blends compatibilized with PP‐g‐2‐HEMA

Polypropylene (PP) and acrylonitrile–butadiene–styrene blends of different composition were prepared using a single‐screw extruder. The binary blend of PP/ABS was observed to be incompatible and shows poor mechanical properties. PP‐g‐2‐hydroxyethyl methacrylate (2‐HEMA) was used as a compatibilizer for the PP/ABS blends. The ternary compatibilized blends of PP/ABS/PP‐g‐2‐HEMA showed improvement in the mechanical properties. Electron micrographs of these blends showed a homogeneous and finer distribution of the dispersed phase. The mechanical performance increased particularly in the PP‐rich blend. The 2.5‐phr (part per hundred of resin) compatibilizer was observed to bring improvement to the properties. The suitability of various existing theoretical models for the predication of the tensile moduli of these blends was examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 72–78, 2003     

Preparation and electrochemical characterization of sulfonated polysulfone cation‐exchange membranes: Effects of the solvents on the degree of sulfonation

Sulfonated polysulfone cation‐exchange membranes with various degrees of sulfonation were prepared by a treatment with chlorosulfonic acid in different solvents of various polarities, and the effect of the solvent polarity on the degree of sulfonation was explored. These membranes were characterized by their ion‐exchange capacity, volume fraction of water, and electrochemical properties. The counterion transport numbers, permselectivity, and fixed charge densities of these membranes were estimated from membrane potential data and varied with the degree of sulfonation, concentration, and external salt concentration. The counterion mobility in the membrane phase was also estimated from membrane conductance measurements. These membrane were found to have good electrochemical properties and are suitable for various types of electromembrane processes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2344–2351, 2005     

Quantification of design associated engineering properties of sesame (Sesamum indicum L.) seed varieties as a function of moisture content

The investigation was intended to examine the influence of selected moisture levels (4.26, 12.66, 25.31, 37.89, 50.21% wet basis) on engineering properties namely, dimensional, gravimetric, frictional, aerodynamic as well as mechanical properties of five selected varieties of sesame seed namely GT-3, GT-4, GJT-5, GT-6, and TKG 22. The investigation finds out that fluctuations in moisture level significantly (p ≤ 0.05) influenced the engineering properties assessed. Increase in moisture content influenced a rise in length, width, thickness, geometric mean diameter, arithmetic mean diameter, sphericity, volume, volumetric expansion coefficient, elongation ratio, flakiness ratio, surface area, projected area, thousand seeds weight, compressibility index, Hausner ratio, angle of repose, coefficient of friction, terminal velocity and Reynolds number of selected sesame verities. Whereas, a reverse trend was observed in aspect ratio, true density, bulk density, tapped densities, drag coefficient, and hardness with moisture content variation. The frictional characteristic of the seed showed improved stability with less flow ability at higher moisture levels. These outcomes disclosed that variation of seed moisture content is authoritative during designing and construction of machinery and process equipment related to sesame. It may be also beneficial in computation of design for hoppers, silos, conveyors, drying, and heat transfer equipment as well as other sesame seed-related process and handling equipment.     

Morphology of Amylose Propionate On the Origin of Two Dimensional Spherulites in Polymers

Crystals of amylose propionate have been grown from dioxane and aniline at different temperatures. Study of morphology of various growth structures reveals that generation of vertical lamellae is very much common in polymer crystals and orientation of these lamellae on further growth determines the final morphology of resulting growth structures. A probable mechanism for the development of hedrites and two dimensional spherulites has been discussed. Various evidences obtained from the study of cellulose triacetate, polyacrylonitrile, polyoxymethylene and polyethylene support this mechanism and suggest that the development of growth structures follow mainly a common mechanism of growth.     

Morphology of Amylose Acetate Role of Intercrystalline Linkages in Polymers

Crystals of amylose acetate have been grown by film formation method of crystal growth. Isolated fibres and fibres present in spherulites showed characteristic twisting and branching habit. Etching of the crystals reveals that some features are observed in a film, and that they are mainly associated on the surface of a film. Various growth stages have been obtained simply by varying concentration of polymer solution at constant temperature. Presence of linkages is found in fibrillar as well as lamellar crystals. Linkages are clearly observed in all growth stages indicating that they may be due to typical growth of features. Evidence obtained for several polymers indicate that linkages are the characteristics of structures grown from concentrated solution as well as from melt. The concentration and location of intercrystalline linkages can be considered to have profound effect on physical properties of polycrystalline material.