Shear Extrusion Research Articles

Super-selective polysulfone hollow fiber membranes for gas separation: rheological assessment of the spinning solution

A polysulfone spinning solution used recently to produce enhanced selectivity gas separation hollow fiber membranes was rheologically assessed using a rotational rheometer and an optical shear cell. Effects of temperature and shear rate on viscosity, power law behavior and normal force provided some clues regarding phase inversion and molecular orientation. At relatively low temperatures, phase inversion may occur in the absence of a shear field. At moderately low temperatures, phase inversion may be induced by applied shear. At higher temperatures, phase inversion is not induced by shear but rather shear induces molecular orientation. The results suggest that, unless spinning at low temperature, extrusion shear does not directly induce demixing during membrane formation but, instead, is linked indirectly to phase inversion through induced molecular orientation which, in turn, affects the subsequent dry or wet precipitation stages in spinning. This work is a step towards the construction of phase diagrams and determining their distortion in shear fields. Such knowledge, coupled with deeper insights into induced polymer molecule orientation, would enable further improvements in spinning techniques and membrane performance.

Rheological behavior of (short) carbon fiber/thermoplastic composites. Part II: The influence of matrix type

This study is the second of a series of two papers on the rheological properties of VGCF/thermoplastic composites, its aim being to compare the performance of different thermoplastic matrices when reinforced with sub-micron Vapor Grown Carbon Fibers (VGCF). For this purpose, two polymers (polypropylene, PP, and polycarbonate, PC) were used to produce composites with different levels of fiber incorporation. The highest content VGCF composites were produced, in pellet form, using a co-rotating twin-screw extruder. These were subsequently diluted during the injection molding stage to obtain composites with different levels of fiber content. The rheological characterization was performed, using the latter materials, by means of both capillary and rotational rheometries, results being presented and discussed in terms of reinforcing capability and its susceptibility to temperature, for the relevant functions in both shear (steady and oscillatory) and extensional flows. The results show that VGCF have a higher reinforcing capability, both rheological and mechanical, when incorporated in the PP matrix. This better performance can be due either to better adhesion between the fibers and PP in comparison to PC, or to a higher degree of melt penetration of non-wetted fiber rich areas and lower fiber length degradation, owing to the lower viscosity of PP in the extrusion shear rate range.

PHYSICO-CHEMICAL AND RHEOLOGICAL PROPERTIES OF LOW-FAT, HIGH-ADDED WATER BEEF SAUSAGE EXTENDED WITH COMMON BEAN FLOUR

Beef sausages extended with common bean flour were manufactured using 5 levels of fat and added water (AW) (25% fat /5% AW; 20% fat/10% AW; 15% fat /15% AW; 10% fat/20% AW and 5% fat 25% AW). Decreasing in fat levels with a simultaneous increase in the amount of added water did not affect (P>0.05) pH and ash content, but decreased cooking yields and increased expressible moisture. The lowest L* (lightness) values (p < 0.05) was recorded for the 25% fat/5% AW formulation. High-fat, low-added water batter required more extrusion shear stress than low-fat, high-added water batter. Beef sausage textural characteristics were reduced by replacing added water by fat.

Influence of time and adhesive system on the extrusion shear strength between feldspathic porcelain and bovine dentin

Objectives: The behavior of dual-cure cements over time remains unclear. This study evaluated the extrusion shear strength of the bond between feldsphatic porcelain and bovine dentin at different time intervals, using three adhesive systems based on dual-cure cements and one based on a self-cure cement. Methods: The adhesive systems evaluated included: C&B/One-Step, Enforce/Prime&Bond NT Dual-Cure, RelyX ARC/Single Bond and Variolink II/Syntac SC. Discs of bovine root dentin, 2.5 mm thick, had the root canal prepared with a standardized taper. Porcelain truncated cones etched with 4% hydrofluoric acid and silanized were bonded into the perforations. The extrusion shear test was performed after 15 min, 4 h, 12 h, 24 h, and 7 days. Data were analyzed using the Weibull distribution. The failure mode was accessed by stereomicroscope and SEM. Results: Statistical differences were found between 15 min and 7 days for Variolink II/Syntac SC and RelyX ARC/Single Bond, and between 15 min and 24 h for Enforce/Prime&Bond NT Dual-Cure. For C&B/One-Step, difference was found between 15 min and 4 h. Between 24 h and 7 days, only the system RelyX ARC/Single Bond showed a significant increase in the characteristic strength. SEM analysis revealed that the failure involved the hybrid layer/dentin or the hybrid layer/adhesive interfaces, regardless of the time interval and adhesive system. Significance: High characteristic strengths were observed after 15 min when dual-cure cements were used. In general, the values found at 24 h or 7 days were higher than at 15 min. However, there was always a considerable probability of bonding failure at low stress levels for all the systems tested.

Analysis of Rubber Particles Produced by the Solid State Shear Extrusion Pulverization Process

Abstract Vulcanized natural rubber was pulverized using a single screw extruder in a non-cryogenic Solid State Shear Extrusion (SSSE) process where rubber granulates were subjected to high compressive and shear stresses. The produced particles had diameters ranging from 40 to 1700 µm. Reprocessing of the produced powder resulted in a narrower particle size distribution. Considerable heat generated in the extruder due to friction caused surface oxidation of the fine rubber particles and, in turn, initiation of agglomeration of a portion of the produced particles. Physical, chemical, and thermal analyses were performed on the produced rubber particles and the rubber granulates to determine the effects of the pulverization process. The produced particles had irregular shapes with rough surfaces. The external surfaces of the particles were porous, but no microporosity was detected by nitrogen BET analysis. Swelling and extraction experiments showed that both the crosslink density and gel fraction of the particles were lower than those of the rubber granulates. The reprocessing of the produced particles caused further reduction in the crosslink density and the gel fraction. A correlation was established between the crosslink density and the gel fraction. Thermal analysis revealed similar behavior of all particles and the granulates in a nitrogen environment, but there was considerable thermo-oxidative degradation of the fine particles in air. The chemical analysis indicated that some of the bonds were broken during the pulverization process, and partial devulcanization had taken place.

401 押出し加工を用いた材料改質と高機能構造材の製造(特別OSセッション 軽量化・高強度化への材料代替・材料進化)

Extruded aluminum shapes have been used for constructive components of the automotives in order to reduce the total weight of ones in the last several years. This paper describes a new manufacturing method of the bumper inner with curvature, knowledge of conform extrusion for the condenser tubes and a new extrusion procedure with shear strain. In experiment of shear extrusion, tensile strength and elongation of products are better than those of the ingot made material. On the conform extrusion, the result of numerical simulation based on upper bound theorem shows the extrusion condition of minimum total energy. And bending of bumper inner is calculated by FEM. It is clear-that bending process is influenced by the geometry of cross section.

熱電変換材料 Ｂｉ‐Ｔｅ系熱電材料のせん断付加押し出し

For improvement of the figure of merit in Bi-Te system, anisotropic microstructure control becomes very important with grain size refinement. The conventional powder compaction processes are mostly ineffective or inefficient in texture control. New alternative processing is strongly awaited to make anisotropic microstructure control for enhancement of thermoelectric properties. In this study, the shear extrusion processing was proposed to make texture control in Bi0.4Sb1.6Te3 alloyment from green compact. In this method, strong shear strain is applied to the sample, resulting in selective shear deformation along the cleavage crystal surface and rearrangement of crystalline orientations through the extrusion passage.As the result, the electrical resistivity of sheared sample was improved from 2.11×10-5(Ωm) to 1.17×10-5 (Ωm) without decrease of Seebeck coefficient. Then, higher power factor of 4.09×10-3 (W/mK2) can be achieved.

A study of extrusion shear and forced convection residence time in the spinning of polysulfone hollow fiber membranes for gas separation

Polysulfone hollow fiber membranes for gas separation were spun using a forced convection technique. Experiments were designed to decouple the effect of extrusion shear from forced convection residence time in the dry gap allowing both factors to be investigated. The main objective was to study the pure influence of shear and its capacity to increase membrane selectivity. The results suggested that extrusion shear influences phase inversion dynamics. Increasing shear decreased active layer thickness and increased pressure-normalized flux. This was discussed in terms of thermodynamic instability and polymer precipitation/coalescence speed. Increasing shear was found to increase selectivity to levels greater than the intrinsic value for the amorphous membrane polymer. This may be as a result of induced molecular orientation in the active layer. However, a critical shear rate existed beyond which selectivity deteriorated. This was attributed to the development of surface pores as the active layer thins. Membranes spun at intermediate forced convection residence times exhibited the highest selectivities. Skin formation must be complete, but excessive residence time allows deleterious non-solvent encroachment from the lumen. The results indicate that if enhanced selectivity and high flux are to be achieved, membranes should be spun at a high shear rate and an optimized residence time in order to minimize surface defects, increase the critical shear rate, decrease active layer thickness and heighten molecular orientation.

Pulverization of rubber under high compression and shear

Non-cryogenic pulverization of rubber material was obtained under high compression and shear using a modified Bridgman Anvil apparatus. The effects of operating variables, such as temperature, normal and shear forces, shear rate, and residence time were examined, and optimum conditions for obtaining desired particle size distribution with minimum agglomeration were identified. Based on our strain energy storage theory, a criterion of pulverization was obtained and computational analysis of deformation of rubber using a Mooney-type equation for stored energy was performed. The numerical values for strain energy distribution in a rubber disk, which indicate potential pulverization under different compression and shear forces, were obtained using the ANSYS computer program. This information was used as a guide to obtain optimum operating conditions and design parameters for optimum design of the solid state shear extrusion (SSSE) pulverization process [H. Arastoopour, Single Screw Extruder for Solid State Shear Extrusion Pulverization, U.S. Patent No. 8,101,468 (1998)].

Physical Properties of Extruded Products as Affected by Cheese Whey

ABSTRACTCorn, rice and potato flour were extruded with sweet whey solids (SWS) or whey protein concentrate (WPC) using low and high shear extrusion processing conditions. WPC added at product content of 25% had minimal effect on the texture of extruded products. Expansion and breaking strength were improved in some processes through changes in extrusion shear and moisture. Whey product incorporation resulted in reduced specific mechanical energy input to the process. Increasing whey product concentration beyond 25% reduced expansion and water absorption indices significantly, affecting textural hardness. Product quality characteristics were directly related to the whey product content.

Powder extrusion: Fundamentals and different applications

AbstractWe propose a novel polymer extrusion process, known as the solid state shear extrusion pulverization and modification (SSSE process), based on the simultaneous action of shear deformation and pressure at selected temperatures. This process can be used for continuous pulverization and copulverization of various polymers. Including different blends, filled materials, thermoplastics, vulcanized rubbers, crosslinked polymers, polymer composites, and natural polymers. Various aspects of this process are considered, including unusual microstructure and properties of powders, low energy consumption, and mechanochemical effects. Possible applications of SSSE to polymer/rubber recycling and to obtaining advanced polymer powders and modified powders are considered, together with scaling‐up problems of equipment suitable for industrial application.

Self-compatibilization of polymer blends via novel solid-state shear extrusion pulverization

The mechanochemistry of a novel economical solid-state shear extrusion (SSSE) pulverization is investigated. SSSE compatibilizes incompatible blends in situ; the process has great potential in recycling of post-consumer plastic waste (PCPW). It is proposed that SSSE causes this self-compatibilization of blends by rupturing polymer chains and allowing them to recombine with their neighboring chains. When this recombination involves dissimilar chains at an interface between powder particles, block copolymers are formed, and if the chain transfer reactions are possible, graft copolymers are formed. These copolymers at the interfaces in the phase-separated, incompatible blend lower the interfacial tension and increase the adhesion at the interfaces, thus compatibilizing the blend. Our nuclear magnetic resonance (NMR) and rheology studies reveal the formation of long chain branches (LCBs) in an linear low-density polyethylene (LLDPE), which is equivalent to the formation of graft copolymers in blends. With NMR, an increase from ∼ 0.2 to ∼ 2.0 of the number of LCBs per 1000 carbon atoms is observed due to pulverization of the LLDPE. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1179–1187, 1997

Self‐compatibilization of polymer blends via novel solid‐state shear extrusion pulverization

Self‐compatibilization of polymer blends via novel solid‐state shear extrusion pulverization

Advanced recycling technology for unsorted plastic waste

AbstractThe object of this paper is to present results of our continuous effort to develop an advanced recycling technology for unsorted (mixed) plastic waste. The pulverization of plastics occur when pressure and high shear are coupled with extensive cooling of the extruder. Under certain processing parameters, plastic chips or flakes (used as feedstock) are converted into a controlled particle size powder. Melt flow rate data has been generated for post‐consumer polyolefins previously made via the new Solid‐State Shear Extrusion (SSSE) pulverization process. A first‐of‐a‐kind laboratory scale, modified co‐rotating twin‐screw extruder ZE‐25 was built by H. Berstorff Maschinenbau, GmbH, Germany, and is now operational at BIRL's Polymer Reclamation Center. Although the post‐consumer polyolefins include a variety of colors, the products from this process are homogeneous, and unusually light in color. The pastel color of the pulverized material demonstrates another advantage of this process as a step in plastics recycling. Several parts of different geometry have been injection molded using coarse powder as a feedstock without pelletization. Mixes of post‐consumer, muliticolor flakes of high density polyethylene (HDPE) and green/clear flakes of polyethylene terphthalte (PET) have been successfully pulverzed and tested. Currently, HDPE and PET are being sorted due to their incompatibility in order to be recycled. This novel extrsion‐pulverization process offers new opportunities for developing value‐added products from commingled plastic waste.

Effect of Shear Energy on Size Reduction of Starch Granules in Extrusion

AbstractThe changes of size and size distribution of starch granules under extrusion conditions have been investigated by using a single screw extruder and an optical microscope coupled with an image analysis system. The mechanical energy input and material processing time were key factors influencing the degree of starch granular size reduction. In a high shear extrusion process (T=40°C), the weight average granular size of extrudate was reduced from ˜12.4μ (raw waxy corn starch) to 1˜2μ, whereas in a low shear extrusion (T=90°C), and granular size was reduced to ˜7μ. Fine particles (±0.5μ) were observed in both extrusion processes. They were 76% (w/w) under a high shear and long processing time conditions and 5% in a low shear and short time process. During the size reduction process, the peaks of size distribution of starch granules shifted from the large size region toward the medium size region and finally to a rather narrowed peak at the small size region when extensive size reduction measures were applied. Extrusion processes can be used to reduce starch granular size effectively.

Morphological studies on extruded films and filaments of polypropylene

AbstractIn the present work, an attempt has been made to study the development of morphology during extrusion and uniaxial stretching of polypropylene (PP) films and filaments at corresponding conditions. Dies for extrusion of films and filaments were designed to achieve similar extrusion velocity and shear rates. Orientation in films and fibers of PP produced from these dies was determined by birefringence and wide‐angle X‐ray diffraction (WAXD). The degree of crystallinity was determined by density and WAXD. The superstructure developed during extrusion was studied in films by small‐angle light scattering. It was inferred that films and fibers prepared under similar conditions would produce similar morphology. Hence, films can be characterized by optical techniques when it is difficult to study fibers. © 1994 John Wiley &amp; Sons, Inc.

Rheological and textural behaviour of double cream cheese. Part I: Effect of curd homogenization

Double cream cheese was made by classical cheesemaking and different products were obtained by varying the curd homogenization pressure (0, 5, 10, 20, 30 and 50 MPa). Rheological and textural behaviour of cheeses were estimated by determining flow curves, viscoelastic parameters G′ and G″ (dynamic testing) and extrusion shear stress (capillary extrusion). Flow curve results were not reliable because the majority of cheese were ‘brittle’ and product destructuration was observed during sampling. Extrusion shear stress increased with the homogenization pressure, and a pressure of around 20 MPa seems to be a value which determines the borderline between two cheese structures. Storage modulus (G′) increased and loss modulus (G″) decreased with the pressure. This, with extrusion results, indicates that fat re-emulsification leads to a product better organized and thus more elastic because of more interactions between particles. Emphasis was placed on the importance of the upstream steps in the manufacturing process, especially on the fat phase destabilization.

Rheological and textural behaviour of double cream cheese. Part II: Effect of curd cooling rate

The influence of curd cooling rate and mode (static or dynamic cooling) on the rheological behaviour of double cream cheese was investigated by measuring flow curves, dynamic parameters (G′ and G″) and extrusion shear stress ( τ e). It was found that an increase in curd cooling rate produces softer cheeses (decreased static yield value and extrusion shear stress) with a weaker structural organization (decreased G′ and G″). This effect seems to be linked to mechanical stress in the heat exchanger, the more so when the final temperature was low. Another spectacular phenomenon was the appearance of a second static yield value ( τ′ y) in the flow curves for dynamic cooling (cooling rates: 30°C/min, 50°C/min, 57°C/min). This second peak increased with cooling rate increase and could be correlated with a ‘sticky’ characteristic of the cheeses. An emulsion destabilization in the heat exchanger was considered to be the origin of the structure change observed. Owing to rapid cooling, the fat crystallization did not influence the emulsion destabilization.

Solid State Shear Extrusion (SSEE) for Pulverization of Flexible and Rigid Polyurethane Foam Wastes

Solid State Shear Extrusion (SSEE) for Pulverization of Flexible and Rigid Polyurethane Foam Wastes

An equation of motion for a thick viscoelastic plate

In this paper an equation of motion is presented for a general thick viscoelastic plate, including the effects of shear deformation, extrusion deformation and rotatory inertia. This equation is the generalization of equations of motion for the corresponding thick elastic plate, and it can be degenerated into several types of equations for various special cases.