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Results of computer modeling of the process of co-extrusion of two-layer ring profile insulation in extrusion dies by the finite-element method are presented. Design features of the 3D models are specified. Recommendations for obtaining high-quality products are presented.

This study aimed to evaluate the survivability of Lactiplantibacillus plantarum 299v encapsulated in chitosan-coated calcium alginate beads with inulin as prebiotic in simulated gastrointestinal conditions and roselle juice. The concentration of calcium chloride and inulin for L. plantarum 299v microencapsulation was optimised and the survivability of free and microencapsulated L. plantarum was assessed under simulated gastrointestinal conditions. Storage stability of the optimised encapsulated L. plantarum 299v-inulin was determined throughout four (4) weeks of storage in roselle juice at 4 °C and 25 °C. The optimized formula for L. plantarum 299v was 2.0% (w/v) of calcium chloride and 3.0% (w/v) of inulin. Optimized calcium alginate-chitosan L. plantarum 299v microbeads with inulin did not affect (p > 0.05) the bead diameter, with a mean diameter of 685.27 μm, and microencapsulation efficiency of 95%. Encapsulated L. plantarum 299v with inulin showed higher survivability (>107 CFU/mL) than free cells and encapsulated L. plantarum 299v without inulin under simulated gastrointestinal conditions and after four (4) weeks of storage in roselle juice at 4 °C. The results indicate that co-extrusion encapsulation and addition of inulin had improved the viability of L. plantarum 299v in roselle juice by protecting probiotic against unfavourable gastrointestinal conditions and prolonged storage. Resumo O objetivo deste estudo foi avaliar a capacidade de sobrevivência de Lactiplantibacillus plantarum 299v encapsulado em esferas de alginato de cálcio revestidos com quitosana, com inulina como prebiótico, em condições gastrointestinais simuladas e suco de rosélia. A concentração de cloreto de cálcio e inulina para a microencapsulação de L. plantarum 299v foi otimizada e a sobrevivência de L. plantarum livre e microencapsulado foi avaliada em condições gastrointestinais simuladas. A estabilidade do encapsulado otimizado L. plantarum 299v-inulina durante armazenamento foi determinada ao longo de quatro semanas em suco de rosélia a 4 °C e 25 °C. A fórmula otimizada para L. plantarum 299v foi de 2,0% (w/v) de cloreto de cálcio e 3,0% (w/ v) de inulina. Microesferas otimizadas de alginato de cálcio-quitosana contendo L. plantarum 299v com inulina apresentaram diâmetro médio de 685,27 μm sem diferença significativa (p>0,05) em relação às partículas sem inulina, e eficiência de microencapsulação de 95%. L. plantarum 299v encapsulado com inulina mostrou maior capacidade de sobrevivência (> 107 CFU/mL) do que células livres e L. plantarum 299v encapsulado sem inulina em condições gastrointestinais simuladas e após quatro semanas de armazenamento em suco de rosélia a 4 °C. Os resultados indicam que a a encapsulação por coextrusão e a adição de inulina melhoraram a viabilidade de L. plantarum 299v em suco de rosélia, protegendo o probiótico contra condições gastrointestinais desfavoráveis e prolongando o armazenamento.

The complexes [Pt(tolpy)Cl(L)] (tolpy = 2-(4-tolyl)pyridyl; L = dmso, dms, py, PPh3, CO) are precursors for the catalytic cleavage of C–C bonds and extrusion of CO from a series of unactivated keto...

One of the routes to minimize the environmental impact of plastics waste is the use of bio-sourced and biodegradable alternatives, particularly for packaging applications. Although Polyhydroxyalkanoates (PHA) are attractive candidates for food packaging, they have poor processability, particularly for extrusion film blowing. Thus, one relatively successful alternative has been blending PHA with a biodegradable polymer. This work proposes film blowing of a co-extruded Poly (hydroxybutyrate) (PHB) layer with a poly butylene adipate-co-terephtalate (PBAT) layer to enhance bubble stability, mechanical and barrier properties. Co-extrusion is detailed, together with the different strategies followed to improve adhesion between film layers and the PHB content in the films. Films with thicknesses below 50 micron and elongation at break beyond 500 % were consistently produced., This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 774088. LH also acknowledges funding from the Portuguese Foundation for Science and Technology Investigator Programme through grant IF/00606/2014.

In this work, the numerical simulation of the non-isothermal steady co-extrusion fiber spinning with flow-induced crystallization is explored. The model is based on the formulation originally proposed by China et al. in which Newtonian and Phan-Thien-Tanner (PTT) fluids are considered the core and the skin layer, respectively. The polymeric flow rate fraction, Deborah dimensionless number and the PTTs parameters on the temperature, the velocity and the crystallization profiles are analyzed. The numerical results show: the temperature profile is sensitive to the polymeric layer flow rate and the deformation parameters (shear thinning and extensional), the tensile stress induced crystallization parameter has a strong influence at the onset of the process, increasing drastically temperature and crystallinity.

Various casing types can be used to produce dry fermented sausages. Within the group of dry fermented sausages, efflorescence formation represents a current issue for the meat processing industry. Therefore, this study aims to investigate the coherence between the casing type and the efflorescence amount. Different casing materials (co-extruded alginate, collagen, and natural casing) were used for the sausage production. The sausages were stored under modified atmosphere packaging at 4 °C and visual and chemical analyses were conducted regularly during 8 wk of storage. Image analyses revealed different amounts of efflorescences for the sausages with alginate (72.2%), collagen (48.3%), and natural casings (25.0%). The magnesium content increased in different amounts on the surface of the sausages produced with alginate (88%), collagen (83%), and natural (59%) casing. The calcium content significantly increased on the alginate casings by 32% but the other casing types showed no enrichment of calcium on the surface. It seems likely that the differences regarding the efflorescence formation occur due to differences in the average pore size of the casings.

This study aimed to compare two processes for the encapsulation of Lactobacillus acidophilus LA3 using alginate or a blend of alginate–shellac as the wall material and sunflower oil as the core. The particles were dried and stored for up to 60 days at 25 °C for stability studies, and the survival of the encapsulated probiotics in simulated gastrointestinal fluids was evaluated. The viability of the LA3 encapsulated by co-extrusion using alginate or a blend of alginate–shellac was, respectively, 6.2 and 7.2 log CFU/g (colony-forming units per gram), after 60 days of storage, while the viability of the LA3 encapsulated by extrusion was, respectively, 5.3 and 6.2 log CFU/g. The particles produced with the blend of alginate–shellac presented additional protection to the probiotics, as revealed by the increased survival rates in simulated gastrointestinal fluids. Taken together, these data provide a promising alternative for the incorporation of the probiotic L. acidophilus LA3 into new functional foods.

Present study was undertaken to optimize the process conditions for development of food grains (maize, defatted soy flour, sesame seed)-banana based nutritious expanded snacks using extrusion processing. Experiments were designed using Box–Behnken design with banana pulp (8–24 g), screw speed (300–350 rpm) and feed moisture (14–16% w.b.). Seven responses viz. expansion ratio (ER), bulk density (BD), water absorption index (WAI), protein, minerals, iron and sensory acceptability were considered for optimizing independent parameters. ER, BD, WAI, protein content, total minerals, iron content, and overall acceptability ranged 2.69–3.36, 153.43–238.83 kg/m3, 4.56–4.88 g/g, 15.19–15.52%, 2.06–2.27%, 4.39–4.67 mg/100 g (w.b.) and 6.76–7.36, respectively. ER was significantly affected by all three process variables while BD was influenced by banana pulp and screw speed only. Studied process variables did not affected colour quality except ‘a’ value with banana pulp and screw speed. Banana pulp had positive correlation with water solubility index, total minerals and iron content and negative with WAI, protein and overall acceptability. Based upon multiple response analysis, optimized conditions were 8 g banana pulp, 350 rpm screw speed and 14% feed moisture indicating the protein, calorie, iron content and overall sensory acceptability in sample as 15.46%, 401 kcal/100 g, 4.48 mg/100 g and 7.6 respectively.

It is of great importance to understand the stretching and folding mechanism in the multiflux co-extrusion die to get uniform multilayer distribution at the end of die lip in the multilayer co-extrusion processes. In this work, to understand the mechanism of the layer distribution, modeling and numerical simulation were carried out for three-dimensional flow analysis in the multilayer co-extrusion die. The multilayer flow fields were numerically visualized and analyzed on the arbitrary cross-section of the multiflux die. In addition, numerical results for the multiflux die characteristics were obtained for non-Newtonian fluids in terms of power-law index for the cross model, which will be useful for the optimal design of screw and die, simultaneously, in the multilayer co-extrusion process.

Encapsulation confers protection to substances as essential oils from processes like oxidation, evaporation or uncontrolled release. In this study almond oil capsules were obtained by co-extrusion/gelling technique. Chitosan was used as shell material and sodium triphosphate pentabasic as cross linking agent. Different encapsulation process variables were studied: cross-linker concentration, nozzles size and potential. Optical microscopy was used to determine the capsules morphology and degradability tests were performed in order to study capsules degradation over time. Results showed that nozzles size and cross linking concentration are key variables to consider in the encapsulation process. Degradability tests showed rapid weight loss.

An unprecedented nickel-catalyzed decarbonylative silylation via CO extrusion intramolecular recombination fragment coupling of unstrained and nondirecting group-assisted silyl ketones is described. The inexpensive and readily available catalyst performs under mild reaction conditions and enables the synthesis of structurally diverse arylsilanes, including heterocyclic and natural product derivatives.

INTRODUCTION: Currently, hot melt extrusion (HME) is a promising technology in the pharmaceutical industry, as evidenced by its application to manufacture various FDA-approved commercial products in the market. HME is extensively researched for enhancing the solubility and bioavailability of poorly water-soluble drugs, taste masking, and modifying release in drug delivery systems. Additionally, its other novel opportunities or pharmaceutical applications, and capability for continuous manufacturing are being investigated. This efficient, industrially scalable, solvent-free, continuous process can be easily automated and coupled with other novel platforms for continuous manufacturing of pharmaceutical products. AREAS COVERED: This review focuses on updates on solubility enhancement of poorly water- soluble drugs and process analytical tools such as UV/visible spectrophotometry; near-infrared spectroscopy; Raman spectroscopy; and rheometry for continuous manufacturing, with a special emphasis on fused deposition modeling 3D printing. EXPERT OPINION: The strengths, weakness, opportunities, threats, (SWOT) and availability of commercial products confirmed wide HME applicability in pharmaceutical research. Increased interest in continuous manufacturing processes makes HME a promising strategy for this application. However, there is a need for extensive research using process analytical tools to establish HME as a dependable continuous manufacturing process.

This work focused on the development of a concentric multi-layered fixed-dose combination via an advanced manufacturing technique, hot-melt co-extrusion. The dosage form was designed to offer differing release behaviour; immediate and sustained release from the coat and core, respectively. Hydrochlorothiazide and losartan potassium were incorporated as anti-hypertensive drugs. Solid-state characterisation revealed that both were transformed into their amorphous forms. In-vitro dissolution testing showed desired release performances offering both immediate and modified release.

Lactobacillus acidophilus NCFM (L-NCFM) was microencapsulated via co-extrusion technique with mannitol. Optimization of coating material, locust bean gum (0% to 2%, w/v) and prebiotic, mannitol (0% to 5%, w/v) was tested on bead size and microencapsulation efficiency. L-NCFM cells microencapsulated in three different forms were tested in simulated gastric juice (pH 2.0) and simulated intestinal juice (pH 7.5) and storage test at 4 °C and 25 °C for 4 weeks. 0.5% (w/v) locust bean gum and 3% (w/v) of mannitol are the optimal concentrations to produce bead size of 570 µm, microencapsulation efficiency of 96.81% and cell count 8.92 log CFU/mL. Microencapsulation of L-NCFM with mannitol protect cells better in acidic environment. The viability of encapsulated L-NCFM with mannitol at 4 °C throughout the storage period for 30 days ranged from 8.62 log cfu/mL to 6.80 log cfu/mL, which met the minimum required for probiotic (106CFU/mL).

This study investigates the effect of microencapsulation (via co-extrusion technology using high methoxyl pectin-enhanced alginate as a shell formulation) on the storage stability and antioxidant properties of kenaf seed oil. Microencapsulated kenaf seed oil (MKSO) and unencapsulated oil were stored at 25 °C for 28 days and at 65 °C for 24 days. The oils were then subjected to stability and quality evaluation based on peroxide, p-anisidine, and total oxidation values, conjugated diene and triene levels, thiobarbituric acid reactive substances, free fatty acids, total phenolic content, and the radical scavenging activity assays of 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid). The results showed that there was a significant increase (p

In this study, Mg/Al composite rod with a thin 6082 aluminum alloy coated AZ31 magnesium alloy was successfully prepared by co-extrusion. Microstructure and texture of the extruded Mg/Al rod were systemically studied. A comparative study about electrochemical behavior of the Mg core and the Al sleeve was also addressed. Our results show that, co-extrusion can greatly refine grains of Mg alloy, but does not change the texture component. The 6082 sleeve exhibits a much better corrosion resistance than the AZ31 core. This study provided a novel approach to improve corrosion resistance of Mg alloy. The Al sleeve served as a barrier to protect the Mg alloy from corrosion.

In order to further solve the problem of the flow path of the head of the existing wood-plastic composite co-extrusion, the structural defects of the head are accurately found. This article first simulates the core and shell flow channels separately to simulate whether they are uniformly extruded and whether the exit speed is consistent. It is further analyzed that the cause of the uneven coating of the part is the problem of the shell flow channel and its structure. It does not meet the design requirements. Then, by proposing a variety of different flow channel structure optimization schemes, further simulations are performed, and the fluid flow trend is analyzed based on the simulation results. First of all it is determined that the existing flow path shape itself has problems. Considering the structure of the overall nozzle flow channel, based on the analysis of the flow channel trend, a new solution for the design of the co-extrusion ring flow channel is proposed. Further solve the structural problem of the coating head,which improved the design efficiency and reduced the waste of personnel and materials caused by continuous die testing. It has certain reference value for follow-up.

Pyrimidines, pyrroles, cycloreversion,CO extrusion, Two possible mechanisms for the transformation of a 1,4-dihydropyrrolo[3,2-b]pyrrole derivative into a tetrasubstituted pyrrole have been studied theoretically and one of them has been found in reasonable accord with the experimental data. This mechanismis part of the very rare example of rearrangement of dihydropyrimidines into pyrroles.

Wood filler is a porous and anisotropic material having different size, shape, and aspect ratio. The use of wood fillers such as wood particle, wood flour, and wood pulp in wood plastic composites (WPCs) are growing rapidly because these wood fillers give improved strength and stiffness to WPCs. However, the wood fillers have originally poor compatibility with plastic matrix affecting the mechanical properties of WPCs. Therefore, to improve compatibility between wood and plastic, numbers of physical and chemical treatments were investigated. While the various treatments led to improved performances in WPC industries using petroleum-based plastics, full biodegradation is still issues due to increased environmental concerns. Hence, bio-based plastics such as polylactide and polyhydroxybutyrate having biodegradable characteristics are being applied to WPCs, but relatively expensive prices of existing bio-based plastics prevent further uses. As conventional processing methods, extrusion, injection, and compression moldings have been used in WPC industries, but to apply WPCs to engineered or structural places, new processing methods should be developed. As one system, co-extrusion technique was introduced to WPCs and the co-extruded WPCs having core-shell structures make the extended applications of WPCs possible.

High fiber snack foods are attracting consumers’ attention due to their health benefits. In this research, corn meal and polydextrose are co-extruded with a twin-screw extruder and the screw speed is varied from 150 to 190 rpm. The objective of the research is to evaluate the effects of screw speed on the product quality. As the screw speed is increased, the expansion ratio and crispness of the fried extrudate are enhanced while the bulk density and hardness are reduced. Increase in screw speed results in increased water absorption index and water solubility index of the product. As the screw speed is increased, the mechanical energy of the extrusion process is also increased. The screw speed has significant correlation with the expansion index, bulk density and texture properties of the fried extrudate (p < 0.05).

The present article reports the results of preliminary studies, carried out for the first time, related to the production of bimetallic tubes by tailoring the initial materials characteristics through powder metallurgy (P/M) and cold extrusion route. It is shown that the domination of consolidation (volume change) during simultaneous deformation of P/M preforms reduces the differential velocity between the core and the sleeve as indicated by lower failure propensity of extrudes. High interfacial friction at the dissimilar P/M preform interface and in turn the high interfacial bond aids the sound flow over a wide range of processing conditions. In addition, the non-uniformities of deformation would be accommodated by the softer preform near the interface through micro-mechanical interactions. It is believed that the current approach of producing the bimetals greatly enhances the manufacturing flexibility and reduces the tool cost. ? 2005 Elsevier B.V. All rights reserved.

Fine-scale ceramic objects are fabricated by forcing a thermoplastic ceramic extrusion compound through a die with reduction ratio R. Objects with complex shapes are fabricated by assembling an extrusion feedrod from a shaped ceramic compound with space-filling fugitive compound. After each reduction state, R2 extrudates are assembled into a feedrod and extruded again, reducing the size and multiplying the number of shaped objects. Several stages of extrusion produce arrays of objects in the size range of 10 µm.

A multilayer ceramic actuator composed of piezoelectrically active Pb(Zn1/3Nb2/3)0.2–Pb(Zr0.5Ti0.5)O0.8 (PZN–PZT) layers and electrically conducting PZN–PZT/Ag layers was fabricated by the co-extrusion process. For the piezoelectric layers, PZN–PZT, which is sinterable at a low temperature (900°C), was used. For the conducting layers, a PZN–PZT/Ag composite, made by mixing silver particles with the PZN–PZT matrix, was employed. For the co-extrusion process, piezoelectric and conducting feedrods were made by mixing the PZN–PZT and PZN–PZT/Ag, respectively, with a thermoplastic polymer. The initial feedrods, which were composed of five 3 mm-thick PZN–PZT layers, two 1.5 mm-thick PZN–PZT layers, and six 1 mm-thick PZN–PZT/Ag layers, were co-extruded through a 24 mm × 2 mm reduction die at 105°C to produce continuous multilayered green sheets. The sheets were stacked, warm pressed, and sintered at 900°C for 4 h after binder burnout. The sintered multilayer actuator showed distinct layers without any reaction products or cracks at the interface. The thicknesses of the piezoelectric and conducting layers were about 200 and 70 μm, respectively. The displacement of the multilayer actuator, composed of 40 piezoelectric layers (with a total height of 10.8 mm), was about 10 μm at an applied voltage of 500 V.

In support of the Convert Program of the U.S. Department of Energy’s National Nuclear Security Administration (DOE/NNSA) Global Threat Reduction Initiative (GTRI), Pacific Northwest National Laboratory (PNNL) has been investigating manufacturing processes for the uranium-10% molybdenum (U-10Mo) alloy plate fuel for the U.S. high-performance research reactors (USHPRR). This report documents the results of PNNL’s efforts to develop the extrusion process for this concept. The approach to the development of a co-extruded complex-shaped fuel has been described and an extrusion of DU-10Mo was made. The initial findings suggest that given the extrusion forces required for processing U-10Mo, the co-extrusion process can meet the production demands of the USHPRR fuel and may be a viable production method. The development activity is in the early stages and has just begun to identify technical challenges to address details such as dimensional tolerances and shape control. New extrusion dies and roll groove profiles have been developed and will be assessed by extrusion and rolling of U-10Mo during the next fiscal year. Progress on the development and demonstration of the co-extrusion process for flat and shaped fuel is reported in this document

Objectives Co-extrusion implies the simultaneous hot-melt extrusion of two or more materials through the same die, creating a multi-layered extrudate. It is an innovative continuous production technology that offers numerous advantages over traditional pharmaceutical processing techniques. This review provides an overview of the co-extrusion equipment, material requirements and medical and pharmaceutical applications. Key findings The co-extrusion equipment needed for pharmaceutical production has been summarized. Because the geometrical design of the die dictates the shape of the final product, different die types have been discussed. As one of the major challenges at the moment is shaping the final product in a continuous way, an overview of downstream solutions for processing co-extrudates into drug products is provided. Layer adhesion, extrusion temperature and viscosity matching are pointed out as most important requirements for material selection. Examples of medical and pharmaceutical applications are presented and some recent findings considering the production of oral drug delivery systems have been summarized. Summary Co-extrusion provides great potential for the continuous production of fixed-dose combination products which are gaining importance in pharmaceutical industry. There are still some barriers to the implementation of co-extrusion in the pharmaceutical industry. The optimization of downstream processing remains a point of attention.

Co-extrusion of materials, which differ in strength and ductility, is a comparatively new and little investigated process. However, this process is of commercial interest since it allows high-quality laminated products to be fabricated. The practical application of this type of co-extrusion was aided greatly by a theoretical analysis of the stress-strain state of the layers of unequal-strength materials. This analysis allowed the optimal strain conditions for steady state co-extrusion to be defined, as well as the specific extrusion conditions defining the limits for steady state processing. The work reported in this paper gives examples of the application of the co-extrusion process to the production of laminated mill products.

Flash vacuum thermolysis (FVT) of 6-aryl-1,3-dioxine-4-thiones 9 leads to the formation of acylthioketenes 10, which are characterized by Ar matrix IR spectroscopy as well as on-line tandem mass spectrometry. The thioketenes 10 undergo a 1,3-shift of the aryl group to generate thioacylketenes 11. Ketenes 11 cyclize to 3-aryl-thiet-2-ones 12, which are also characterized by matrix IR spectroscopy and tandem mass spectrometry. The thiet-2-ones 12 undergo two kinds of reaction under the FVT conditions: (i) cheletropic CO extrusion with formation of arylthioketenes 13, and (ii) cycloreversion to COS and arylacetylene.

The multi-faceted bonding of CO in molecular phosphorus compounds is described using calculated P–C bond strengths as a criterion. Full compliance matrices at coupled cluster level of HPCO (1a), singlet oxaphosphirane-3-ylidene HP(η2-CO)), the dimer (HPCO)2 as well as PCH, HPCH2 and H2P–CH3 were calculated to obtain quantifiable data and enable comparison. The quest for CO coordination and activation was examined for phosphaketenes 1a–f: the P–C compliance constants (in A mdyn−1) reveal a clear trend that shows a weakening of the P–CO bond strength from 1a to mono-ligation as in [(OC)5W{P(CO)Me}] (1c) (0.301), in H3BP(CO)Me (1b) (0.322), to bis-ligation as in [{(OC)5W}2P(CO)R] (1f) (0.488) to (H3BP)2(CO)Me (1d) (0.649). Availability of p-type electron density at phosphorus drastically strengthens the P–CO bond and weakens the C–O bond via π–back-donation, bis complexes are better described as weak CO (C→P) adducts to phosphorus. In complexes [(OC)5W{P(CO)R}] the CO activation by phosphorus equals that of CO activation through tungsten in pentacarbonyltungsten complexes. A comparative study of various CO bonding motifs in molecular compounds indicates that acyclic (2) or cyclic diphospha-urea derivatives (2–5) or isomers (6) display P–CO bond strengths (compliance constants range 0.502–0.640) well below that of the P–C bond of H2P–CH3 (0.364), thus providing insight into the bonding and the ease of CO extrusion, experimentally known for some cases. A highly unusual adduct of CO was obtained in silico through two-fold P-ligation in diphosphiren-3-ones 2a–d, the parent compound of which was found to be properly described as a side-on (PP)→(CO) complex, in contrast to its aza-analogue 2aN. A drastic weakening of the P–CO bond strength is observed from P2CO (2a) (0.502) to the C2-symmetrical (H3BP)2CO (2b) (0.913); the latter represents an extreme case of a weakly bound CO. Furthermore, calculated 31P NMR shifts and scalar 1J(P,E) couplings were correlated with P–CO and PC–O compliance constants as a tool for experimentalists.

Small Rings, 86. – Attempts to Synthesize Alkyltri-tert-butyltetrahedranes by the Cyclopentadienone Route; Photochemical Behavior of the Cyclopentadienones Only the Tetra-tert-butyltetrahedranes 8a–c can be synthesized by photochemical CO extrusion from the corresponding cyclopentadienones 6a–c. This strategy fails with other cyclopentadienones like 6d–f.

Co-extrusion by means of only one single screw with a double channel was studied. The effects of the operating conditions, the material properties and the screw geometries on the inter-channel flow and the output rate were determined. The flow mechanism and the application to the composites with stratified structures were discussed. The inter-channel flow rate decreased with decrease in the back pressure, the stock temperature, the screw rotational speed and the viscosity difference between polymer melts in both channels. The decrease in the compression ratios of channels, the barrier flight in the compression zone and the sealing at the flight clearance with the polyamide-packing reduced the inter-channel flow significantly without a decrease in the output rate. With this method, co-extrudates with distinctly stratified cross-sections were prepared. The single screw with double-channel could be applied effectively to the co-extrusion of composites with stratified structures such as sheath-and-core structures, and it is particularly suitable to distribute the additives heterogeneously or to enclose the waste polymer.

An experimental study of the co-extrusion of polyethylene and TiO2-filled polyethylene through capillary and rectangular cross-section dies has been carried out. The influence of viscosity ratio, cross-section type, die length and duration of flow has been studied. Low viscosity melts will encapsulate high viscosity melts during flow through cylindrical and rectangular dies. Low viscosity unfilled melts can encapsulate higher viscosity filled melts and low vicosity filled melts can encapsulate higher viscosity unfilled melts. However, the rate and extent of encapsulation seems to be greater for the former case. This may be due to differences in the viscosity-shear stress behavior of the filled and unfilled melts. In rectangular dies, the extent of encapsulation for any pair is greater when the interface is initially perpendicular to the shorter cross-section dimension. The results are consistent with the idea that encapsulation primarily depends upon the ratio of die length to initial interface length.