Numerical Simulations of Polymer Melt Conveying in Co-Rotating Twin Screw Extruder

The 3 D non isothermal flow of non Newtonian viscous polymer melt in a co rotating twin screw extruder is modeled. The distributions of the velocity, temperature, pressure and the viscous dissipation in the flow domain are presented by using a fluid dynamics analysis package (Polyflow). The numerical results show that the temperatures are high in the intermeshing region and on the screw surface, the maximum pressure and the minimum pressure occur in the intermeshing region, and the flow rate is almost proportional to the screw speed.

Numerical study on mixing performance of screw elements in intermeshing counter-rotating and co-rotating twin-screw extrudes

The flow process of unplasticized polyvinyl chloride （U PVC） through the mixing zone of intermeshing counter rotating and co rotating twin screw extruders （TSEs） were numerically simula ted by the finite element method. Three dimensional isothermal flow field of U-PVC in two kinds of TSE was calculated. The mixing performance of the screw elements of the extruders was statistically analyzed by particle tracking method. The dispersive mixing performance was characterized by the mixing index, the logarithm of stretching, and the segregation scale. The distributive mixing per forulance was characterized by the resident time distribution. The results indicate that the counter rotating TSE can build higher pressure and generate higher axial velocity and shear rate, whereas the co rotating TSE has better performance in dispersive and distributive mixing.

3D-Printed PLA Filaments Reinforced with Nanofibrillated Cellulose

In the current study poly(lactic acid)PLA composites with a 3 wt%and 5 wt%of nanofibrillated cellulose(NFC)were produced by 3D-printing method.An enzymatic pretreatment coupled with mechanical fibrillation in a twin screw extruder was used to produce high consistency NFC.Scanning electron microscopy(SEM)equipped with Fibermetric software,FASEP fiber length distribution analysis,Furrier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TGA),tensile tests,impact tests and differential scanning calorimetry were used to characterize NFC and PLA/NFC composites.The results of the fiber length and width measurements together with the results of the SEM analysis showed that enzymatic hydrolysis coupled with a twin screw extrusion could effectively reduce the diameter and length of cellulose fibers.The produced NFC consisted of microand nanosized fibers entangled in a characteristic 3D-network.Based on the FT-IR analysis,no new bonds were formed during the enzymatic hydrolysis or fibrillation process.The TGA analysis confirmed that produced NFC can be used in hightemperature extrusion processing without NFC degradation.During the PLA/NFC composites preparation the NFC agglomerates were formed,which negatively influenced PLA/NFC composites impact properties.The slightly improved tensile strength and elastic modulus were reported for all composites when compared to the neat PLA.The elongation at break was not affected by the NFC addition.No significant differences in thermal stability were detectable among composites nor in comparation with the neat PLA.However,the crystallinity degree of the composite containing 5 wt%NFC was increased in respect to the neat PLA.

Effect of Extrusion Process Parameters and Particle Size of Sorghum Flour on Expanded Snacks Prepared Using Different Varieties of Sorghum （Sorghum bicolour L.）

Sorghum is a staple food grain in many semi-arid and tropic areas of the world, because of its good adaptation to hard environments and its good yield of production. Among important biochemical components for sorghum processing are levels of starch and starch depolymerizing enzymes. Due to presence of high amount of starch （56%-73%）, sorghum could be the good candidate for manufacturing of expanded snacks. The effect of various extrusion process parameters on structural and functional properties of extruded snacks prepared using three selected varieties of sorghum including SPV 1411 （Parbhani moti） and SPV 1595 （Parbhani jyoti） （newly developed varieties） and M-35-1 （Maldandi） were investigated in this study. Sorghum flour of different particle size viz. 2, 0.84 and 0.49 mm, was subjected to different extrusion processing conditions： feed moisture content （16%-24%）, die temperature （110-150 ~C）, screw speed （150-270 rpm） and feed rate （50-120 g min^-1）. The feed moisture and die temperature （process variables） showed significant effect on the physical properties. This process parameter also increased dietary fibre with decrease in the content of tannins. Box-behnken design was successfully used to show a relationship between extrusion processing conditions and physical properties of extrudates. The extrudates obtained using SPV 141 l, a variety of sorghum, showed significant results in all attributes compared to SPV 1595 and M-35-1, at feed moisture 22%, die temperature 130℃ and screw speed 210 rpm with 90% overall acceptability.

Rheological,mechanical,thermal,tribological and morphological properties of PLA-PEKK-HAp-CS composite

The present study reports investigations on rheological,mechanical,thermal,tribological and morphological properties of feedstock filaments prepared with polylactic acid-polyether ketone ketone-hydroxyapatite-chitosan(PLA-PEKK-HAp-CS)composite for 3D printing of functional prototypes.The study consists of a series of melt processing operations on melt flow index(MFI)setup as per ASTM D-1238 for melt flow certainty followed by fixation of reinforcement composition/proportion as 94%PEKK-4%HAp-2%CS(B)by mass in PLA matrix(A).The blending of reinforcement and preparation of feedstock filament for fused deposition modeling(FDM)set up has been performed on commercial twin screw extruder(TSE).The results of study suggest that feedstock filaments prepared with blend of 95%A-5%B(by mass)at 200℃processing temperature and 100 r/min rotational speed on TSE resulted into better tensile properties(35.9 MPa peak strength and 32.3 MPa break strength)with 6.24%surface porosity,42.67 nm surface roughness(R_(a))and acceptable heat capacity(2.14 J/g).However as regards to tribological behavior,the minimum wear of 316μm was observed for sample with poor tensile properties.As regards to crash application for scaffolds the maximum toughness of 1.16 MPa was observed for 85%A-15%B(by mass)at 200℃processing temperature and 150 r/min rotational speed on TSE.

Refueling for Steady-State Plasma by Repetitive Pellet Injection in Large Helical Device

A repetitive pellet injector has been developed for investigation ofrefueling issues towards the steady-state operation in Large Helical Device (LHD). Continuousoperation of more than 10000 pellet launching at 10 Hz has been demonstrated. The maximum repeatingrate is 11 Hz. No technical constraint for longer operation has been found. The reliability ofpellet launch has exceeded 99.9%. The initial application to the NBI-heated plasmas has beensuccessful in the last experimental campaign of LHD. Although the pulse length is limited by theoperational constraint of NBI, the plasma with a density of 8 X 10^(19) m^(-3) has been sustainedfor 2 s by the pellet injection at 10 Hz. A prospect for the future experiment is discussed on thebasis of the initial result.

Simulation of cottonseed cake melt flow in metering zone of a single screw extruder

Research on the extrusion of natural polymers(food,feed,etc.)is relatively new due to the complex physicochemical transformations of raw materials,although plastics melt conveying and transport have been well studied.The structure and composition,rheological behavior as well as extrusion processing of natural polymer are much more complicated.In this study,a quasi-three-dimensional(3D)fluid flow model for non-Newtonian,non-isothermal and undeveloped temperature was developed,the model prediction being in reasonably good agreement with the experiment.Results show that the influence of moisture content,among other process variables,is the most significant,followed by screw speed.Some interaction exists between these two variables and the screw speed effect becomes marginal at high moisture contents.In addition,viscosity change in the channel was studied.