Wall slip boundary condition is first introduced into twin-screw extrusion with the Navier slip law. Three-dimensional isothermal flow in the twin-screw extruder is simulated by using the finite element package POLYFL...Wall slip boundary condition is first introduced into twin-screw extrusion with the Navier slip law. Three-dimensional isothermal flow in the twin-screw extruder is simulated by using the finite element package POLYFLOW. Profiles of velocity contours in the screw channel and shear rate distributions in the intermeshing region are presented for different slip coefficients. Curves of axial pressure difference, average shear rate and dispersive mixing index vs. the slip coefficient are plotted and discussed. Comparisons are also made between the wall slip conditions and the non-slip condition. The simulation results indicate that, as the level of wall slip decreases, the axial pressure difference rises, the shear effect is intensified and the axial mixing is also enhanced. All these flow characteristics seem to level off with the increase of the slip coefficient. However, because of the inherent limitation of the Navier slip law, use of an overestimated slip coefficient would predict an over-sticky state between the screw surface and the polymer melt.展开更多
The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after proces...The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after processing is about 1%-2% . FTIR spectra indicate the paraaffin oil residue is trivial and UHMWPE is not oxidized. SEM reveals the HA nano particles are homogeneously dispersed by twin-screw extrusion and the inter-particle spaces are penetrated with UHMWPE fibrils by swelling treatment. HRTEM image indicates the HA particles and UHMWPE are intimately contacted by mechanical interlocking. Compared with the unfilled UHMWPE, stiffness of the composite with the HA volume fraction 0. 23 was significantly enhanced to 9 times without detriment of the yield strength and the ductility.展开更多
Rice-glucose-lysine blend was extruded using a co-rotating twin-screw extruder.The effects of different extrusion conditions on the browning properties of extrudates were analyzed and compared using the CIE Lab system...Rice-glucose-lysine blend was extruded using a co-rotating twin-screw extruder.The effects of different extrusion conditions on the browning properties of extrudates were analyzed and compared using the CIE Lab system of measurement.Extrusion process variables included moisture content,screw speed,barrel temperature,and screw geometry.The influence of product temperature on the browning property of extrudates was significant(P<0.05).The color parameters were related to product temperature by a 4th degree polynomial(P<0.05).Hunter color scale values(L*,a*,b*,-L*a*/b*,Whiteness Index,and Yellowness Index)from extruded samples were analyzed to relate to extrusion process variables.Product temperature and browning properties were modeled and tested at various screw configurations and extrusion conditions.Product temperature and browning property models were verified using different screw geometries and other processing conditions with reasonable accuracy.展开更多
The aim of the research was to examine the influence of organo-modified Indian bentonite （IB） nanoclay dispersed in vinyisster on the mechanical properties of nanoclaylvinylesterlglass nanocomposRes. Nanoclay was or...The aim of the research was to examine the influence of organo-modified Indian bentonite （IB） nanoclay dispersed in vinyisster on the mechanical properties of nanoclaylvinylesterlglass nanocomposRes. Nanoclay was organically modified using cationic surfactant hexadecyltrimethylammonium bromide （HDTMA-Br） by cation exchange method and dispersed in vinylester using ultrasonication and twin screw extrusion. XRD of nanoclaylvinylester revealed exfoliaUon at 4 wt.% nanoclay indicating uniform dispersion in the polymer. DSC results showed improvement in glass transition temperature by 22.3% in 4 wt.% nanoclaylvinylester/glass when compared with that of vinylester/glass. Nanoclay/vinylester/glass with 4 wt,% nanoclay showed 29.23%, 23.84% and 60.87% improvement in ultimate tensile strength （UTS）, fiexural strength （FS） and interlaminar shear strength （ILSS） respectively when compared with those of vinylester! glass. The mode of tensile failure examined by SEM showed no agglomeration of nanoclay in 4 wt.% nanoclayNinylester/glass specimens.展开更多
文摘Wall slip boundary condition is first introduced into twin-screw extrusion with the Navier slip law. Three-dimensional isothermal flow in the twin-screw extruder is simulated by using the finite element package POLYFLOW. Profiles of velocity contours in the screw channel and shear rate distributions in the intermeshing region are presented for different slip coefficients. Curves of axial pressure difference, average shear rate and dispersive mixing index vs. the slip coefficient are plotted and discussed. Comparisons are also made between the wall slip conditions and the non-slip condition. The simulation results indicate that, as the level of wall slip decreases, the axial pressure difference rises, the shear effect is intensified and the axial mixing is also enhanced. All these flow characteristics seem to level off with the increase of the slip coefficient. However, because of the inherent limitation of the Navier slip law, use of an overestimated slip coefficient would predict an over-sticky state between the screw surface and the polymer melt.
文摘The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after processing is about 1%-2% . FTIR spectra indicate the paraaffin oil residue is trivial and UHMWPE is not oxidized. SEM reveals the HA nano particles are homogeneously dispersed by twin-screw extrusion and the inter-particle spaces are penetrated with UHMWPE fibrils by swelling treatment. HRTEM image indicates the HA particles and UHMWPE are intimately contacted by mechanical interlocking. Compared with the unfilled UHMWPE, stiffness of the composite with the HA volume fraction 0. 23 was significantly enhanced to 9 times without detriment of the yield strength and the ductility.
文摘Rice-glucose-lysine blend was extruded using a co-rotating twin-screw extruder.The effects of different extrusion conditions on the browning properties of extrudates were analyzed and compared using the CIE Lab system of measurement.Extrusion process variables included moisture content,screw speed,barrel temperature,and screw geometry.The influence of product temperature on the browning property of extrudates was significant(P<0.05).The color parameters were related to product temperature by a 4th degree polynomial(P<0.05).Hunter color scale values(L*,a*,b*,-L*a*/b*,Whiteness Index,and Yellowness Index)from extruded samples were analyzed to relate to extrusion process variables.Product temperature and browning properties were modeled and tested at various screw configurations and extrusion conditions.Product temperature and browning property models were verified using different screw geometries and other processing conditions with reasonable accuracy.
文摘The aim of the research was to examine the influence of organo-modified Indian bentonite （IB） nanoclay dispersed in vinyisster on the mechanical properties of nanoclaylvinylesterlglass nanocomposRes. Nanoclay was organically modified using cationic surfactant hexadecyltrimethylammonium bromide （HDTMA-Br） by cation exchange method and dispersed in vinylester using ultrasonication and twin screw extrusion. XRD of nanoclaylvinylester revealed exfoliaUon at 4 wt.% nanoclay indicating uniform dispersion in the polymer. DSC results showed improvement in glass transition temperature by 22.3% in 4 wt.% nanoclaylvinylester/glass when compared with that of vinylester/glass. Nanoclay/vinylester/glass with 4 wt,% nanoclay showed 29.23%, 23.84% and 60.87% improvement in ultimate tensile strength （UTS）, fiexural strength （FS） and interlaminar shear strength （ILSS） respectively when compared with those of vinylester! glass. The mode of tensile failure examined by SEM showed no agglomeration of nanoclay in 4 wt.% nanoclayNinylester/glass specimens.
