Effect Of Screw Speed Research Articles

Dynamic particle analysis for the evaluation of particle degradation during compounding of wood plastic composites

A dynamic image analysis method was applied for particle characterisation to study the effect of different process conditions during twin-screw compounding of WPC. The use of distributions based on different types of quantity is discussed with respect to their sensitivity to reveal the effects of different process conditions on particle degradation. Distributions based on length proved to be most suitable to represent the initially broad length distribution of the particles before processing. Sensitivity was strong enough to show differences in particle size after processing depending on process conditions. Particle size was reduced by more than 97% compared to initial size. Degradation was stronger with increasing wood content and when the screw design contained more mixing elements. The effect of screw speed and feed rate was dependent on filler content and screw design.

Effects of Extrusion Process Parameters on a Cereal-Based Ready-to-Eat Expanded Product Formulated with Carrot Pomace

The effects of extrusion process parameters, i.e., screw speed (300–500 rpm), die temperature (120–180°C), feed moisture content (14–20%), and sample formulation (60–80% rice flour/10–30% pulse flour [red lentil]/10% carrot pomace), on the functional (bulk density [BD], expansion ratio [ER], water absorption index [WAI], and water solubility index [WSI]), physical (hardness and overall acceptability [OA]), and system (specific mechanical energy [SME]) properties of an expanded rice-based snack product were investigated. The experiments were planned using a Box-Behnken design, and the extrusion process parameters were optimized for maximum ER, WAI, and OA and minimum BD, WSI, SME, and hardness within the experimental range using response surface methodology. Analysis of variance (ANOVA) revealed the higher significant (P ≤ 0.05) effects of feed moisture content on functional properties and of die temperature on physical properties, followed by the effect of screw speed on system properties, compared with o...

The effect of processing parameters on cell structure and mechanical properties of extrusion‐foamed poly(vinyl chloride) sheets

The objective of this study was to investigate the effect of processing parameters on cell structure and mechanical properties of extrusion‐foamed poly(vinyl chloride) sheets. For this purpose, the effects of screw speed and die temperature on cell morphology, density, and mechanical properties, including tensile strength, elongation at break, flexural strength, and notched impact strength of the foam samples, were determined under the same conditions. The experimental results indicated that the extrusion‐foaming process was comparatively stable as the screw speed changed in the range of 5.5–8.5 rpm. It was also shown that the lower the die temperature, the higher the die pressure and pressure drop rate, which is conducive to uniform bubble nucleation. In addition, the lower die temperature was beneficial for bubble solidifying and shaping. Therefore, in the range of temperature allowed, the lower the die temperature, the foamed poly(vinyl chloride) sheets with better cell structure and mechanical performance can be obtained. J. VINYL ADDIT. TECHNOL., 22:377–383, 2016. © 2014 Society of Plastics Engineers

The Effect of Screw Speed on Extrusion Quality of the Single-Screw Extruder

This paper adopts the method of multi-phase flow to simulate the extrusion process of single-screw extruder based on different screw speed by using the finite element analysis software, and get the conclusion that the screw speed has a significant effect on the extrusion quality and outlet pressure of the single-screw extruder. With the increase of the screw speed, the extrusion quality of the single-screw extruder gets worse and the outlet pressure of the single-screw extruder increases.

Effects of Screw Speed and Sesame Cake Level on Optimal Operation Conditions of Expanded Corn Grits Extrudates

Abstract Mixtures of sesame cake (0–20%) and corn grits processed in a single-screw extruder to improve the nutritional value of corn-expanded extrudates. Response surface methodology (RSM) was used to analyse the effect of screw speed (X1) and sesame cake level (X2) on the objective (radial expansion ratio (Y1), hardness (Y2), degree of gelatinization (Y3), and water solubility index (Y4)) attributes of a corn-based sesame cake extrudates. The optimum acceptable regions determined from subjective decision and previous studies by referred authors. Therefore, it assumed that radial expansion ratio should be more than 4, hardness should be less than 7.7 kgf, degree of gelatinization should be more than 69%, and water solubility index should be less than 2.9%. Individual contour plots of the different responses were overlaid, and regions meeting the optimum radial expansion ratio of 4.03, hardness of 7.51 (kgf), degree of gelatinization of 69.28(%), and water solubility index of 2.87 (%) were identified at the screw speed of 311 rpm and the sesame cake level of 16%, respectively.

Effect of extrusion cooking process parameters on the retention of bilberry anthocyanins in starch based food

The aim of this research was to investigate the influence of extrusion cooking on the retention of bilberry bioactives. Maize starch was mixed with 2% of bilberry extract and extruded using a twin screw extruder. The effects of screw speed (180–7201/min), moisture content (18–28%, wet base) and barrel temperature (100–160°C) on the retention of anthocyanins, total phenolics and antioxidant activity in extruded samples were investigated. While total phenolics and antioxidant activity were unaffected by extrusion cooking, anthocyanin retention was depending on barrel temperature, moisture content, screw speed and flow rate. The highest retention was observed at the lowest barrel temperature (100°C, c/c0=0.82), the highest moisture content (28%, c/c0=0.90), the lowest screw speed (180 1/min, c/c0=0.75) and the highest flow rate (30kg/h at 3601/min, c/c0=0.77), respectively. Even at the highest screw speed of 7201/min investigated, the anthocyanin retention could be enhanced by increasing the flow rate. The addition of a flow channel extended the exposure time and decreased anthocyanin retention. A comparison between offline heating of bilberry extract solutions and extrusion cooking indicated that the rate constant of anthocyanin degradation depends on moisture content and interactions with mechanical energy. Extruded samples showed a high retention of color and anthocyanins up to 82% even after 40months of storage. Extrusion cooking offers thus the chance to produce products rich in total phenolics and antioxidants while anthocyanins retention can be adjusted.

The plasticating sequence in barrier extrusion screws part I: Modeling

The plasticating sequence in barrier screws is modeled from hopper to die. The aim is to couple this routine to an optimization algorithm and use the software to set optimal operating conditions and screw design. The procedure developed to describe the geometry of the barrier section enables tackling most of the existing solutions. Calculations encompass gravity solids conveying in hopper, drag solids conveying, delay in melting, melting, and melt conveying. The onset and length of melting are decoupled from the beginning and profile of the barrier, providing a more realistic description of the effect of operating conditions and screw geometry. Predictions of melting and pressure axial profiles, output, distributive mixing, melt exit temperature, viscous dissipation, and mechanical power consumption are presented, and the effect of screw speed is discussed for a variety of barrier screw designs. POLYM. ENG. SCI., 54:1791–1803, 2014. © 2013 Society of Plastics Engineers

Residence Time Distribution of Soy Protein Isolate and Corn Flour Feed Mix in a Twin-Screw Extruder

The residence time distribution (RTD) of soy protein isolate (SPI) and corn flour mixture through a twin-screw extruder under different conditions was evaluated. A full-factorial design of experiments was used to select the variables at different levels. The feed mixture was prepared by blending corn flour and SPI in the ratio of 4:1 (20% SPI content). The effect of screw speed (75, 100 and 125 rpm), feed mixture moisture content (25, 30 and 35%) and die diameter (3 and 5 mm) were investigated. All factors were found to have a significant (P < 0.05) effect on the mean resident time and its variance (square of standard deviation). Higher screw speed, higher initial moisture content and larger die diameter resulted in a shorter mean residence time. Two conventional flow models were used to represent the RTD profile in the extruder – the frequency model (F-distribution) and the cumulative RTD model (E distribution). The parameters of these models – the half-concentration internal age and particle accumulation rate – were determined by a nonlinear regression. The parameters of these models were responsive and related to process variables and both F- and E-distributions were well predicted. Practical Applications Residence time distribution (RTD) is an important parameter that describes the time spent by particles through any continuous processing system. RTD study is important with respect to extrusion processing because the properties of extruded product depend on the shear, pressure, time and temperature history of the product in the extruder. The study is aimed at evaluating RTD of a protein-rich formulation obtained by different blends of soy protein isolates and corn flour which are prepared for producing protein-rich soy-based products. The study is important because it examines the influence of selected process and product variables on the residence time of particles in the twin-screw extrusion system.

The effects of nanoclay dispersion levels and processing parameters on the dynamic vulcanization of TPV nanocomposites based on PP/EPDM prepared by reactive extrusion

AbstractThe study considers the effects of different dispersion levels of nanoclay on the crosslinking reaction of thermoplastic vulcanizate (TPV) nanocomposites based on polypropylene/ethylene propylene diene M‐class rubber (PP/EPDM). PP nanocomposites with dispersion level ranging from intercalated structures to a mixture of intercalated tactoids and exfoliated layers were used as the thermoplastic phase. Dimethylol phenolic resin or octylphenol‐formaldehyde resin was used as curing agents, along with stannous chloride dihydrate as the catalyst, to vulcanize the rubber phase during the reactive extrusion process. Initially, temperature effects were investigated in internal batch mixer. Subsequently, the effects of screw speed (i.e., shear rate and residence time) were evaluated along the screw length. Different criteria such as nuclear magnetic resonance (NMR) signal line width, bound curative content, and residual diene concentration were used to evaluate the extent of crosslinking, along with normalized storage modulus and gel content. X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) micrographs showed that the dynamic vulcanization process improves the dispersion level of nanoclay in the final TPVs. It was found that the presence of nanoclay influences the crosslinking reaction, mainly through its effect on the continuity index of the EPDM phase. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Effect of Speed and Back Pressure on the Performance of Screw Press in Dewatering of Cassava Mash

A cassava mash process handling machine was developed and tested. Studies were conducted on the effect of screw speed at 20rpm to 100rpm at 20rpm interval. Back pressure was induced by the use of spring of 100N, 200N and 300N. Using a TMS 4(2)1425 variety of cassava, the performance of the screw press unit of the machine was evaluated. The operating parameter of the machine at 40-50 rpm produce a mash with an average moisture content of 52% moisture content wet basis. With the back pressure set at 200N as the machine standard.

An experimental study of single‐screw extrusion of HDPE–wood composites

AbstractSingle‐screw extrusion experiments were carried out to study the extrusion characteristics of HDPE–wood composites. Three screw geometries (A, B, and C) were used, and the effects of screw speed on output, melting, and pressure profile were studied. Screw A had a much higher compression ratio than screws B and C, which directly affected the melting behavior of the polymers. Screws B and C had the same compression ratio; however, screw C had the same metering capacity as screw A. Therefore, by comparing screws B and C, the effect of feed depth on the solid conveying capacity was investigated. It was found that while screw B had higher outputs than both screws A and C as expected, screw C had a much lower output than screw A for highly filled resins even though they had the same metering capacity. For HDPE, screws A and C showed the same output as expected. Further examinations of the pressure profiles and melting profiles from screw extraction experiments confirmed that screw C showed a severely starved solids conveying capacity for wood‐filled resins, which limited the total outputs. Comparing the outputs and pressure generations between theoretical predictions and actual experimental results, it was evident that due to the inaccurate assumption of fully filled channels common in single screw extrusion, both outputs and pressure generations in the extruders were overpredicted. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:197–218, 2010; View this article online at wileyonlinelibrary. DOI 10.1002/adv.20190

Morphology Evolution in PC/PE Blends with and without Compatibilization During Twin-Screw Extrusion

The morphology evolution in polycarbonate/polyethylene (PC/PE) blends with and without compatibilization in a twin-screw extruder was studied using a scanning electron microscope (SEM). The effects of screw speed and compatibilizer on the morphology of PC/PE blend during the extrusion were discussed in detail. It was found that the shape and size of the dispersed phase in the uncompatibilized PC/PE blend are both influenced by the screw speed. The evolution of dispersed phase morphology can be affected by increasing screw speed, and the dispersed particle size decreases with the increasing of the screw speed. As a compatibilizer, the addition of the (ethylene-methyl acrylate-glycidyl methacrylate) copolymer (E-MA-GMA) could accelerate the breakup of the PC dispersed phase and decrease the dispersed particle size. The dispersed droplet size in the PC/PE blend with compatibilization was hard to change at different positions along the screw axis with a higher screw speed. Along with the addition of the compatibilizer, the dispersed particle size was slightly influenced by the screw speed.

Mechanical and microstructural properties of soy protein – high amylose corn starch extrudates in relation to physiochemical changes of starch during extrusion

Mechanical and microstructural properties of expanded extrudates prepared from blends of high amylose corn ( Zea mays L. ssp. Mays) starch (HACS) and soy protein concentrate (SPC) were studied in relation to the physicochemical changes in starch. Effects of screw speed (230 and 330 rpm) and SPC level (10%, 20%, 30% and 50%) on expansion and mechanical properties were determined. Compared with 230 rpm, screw speed at 330 rpm resulted in increased specific mechanical energy, expansion ratio, water absorption and water solubility indices and decreased bulk density and piece density. Varying screw speeds did not significantly affect the mechanical strength of extrudates or starch molecular weight distribution. Bulk and piece densities, and water absorption index (WAI) only slightly increased or exhibited no significant trends as SPC level increased to 20%. A substantial increase in bulk and piece densities and decrease in expansion ratio and WAI were observed as SPC level increased from 20% to 30%. The trends were either reversed or moderated as SPC increased to 50%. These results in combination with average crushing force and water solubility index data provided a significant insight into the interactions between HACS and SPC during extrusion processing. As compared to an earlier baseline study by our research group on normal corn starch – SPC extrudates, results from the current study indicated that the expansion of extrudate containing HACS alone was lower than that of extrudates containing normal corn starch. However, expansion of the HACS–SPC blends was not significantly impacted at 10–20% SPC levels, whereas the expansion of normal corn starch was significantly reduced.

Produção de farinha instantânea de mandioca: efeito das condições de extrusão sobre as propriedades térmicas e de pasta

With the advancement of technology, there is the possibility of introduction of differentiated flours, such as cassava instant flour. This alternative has generated great interest from the cassava processing industries. This study aimed to assess the effect of extrusion temperature, moisture content and screw speed on the thermal and viscosity properties of extruded cassava flour. The results showed significant effects of process parameters on the viscosity properties, with effect of screw speed on cold viscosity, viscosity peak and breakdown. The viscosity peak was influenced by the three parameters of extrusion process. No significant effects of operational conditions were observed on the final viscosity and retrogradation. The thermal properties of extruded cassava flours showed no residual enthalpy of gelatinization.

Effects of Fiber Characteristics on the Rheological and Mechanical Properties of Polycarbonate/Carbon Fiber Composites

Rheological and mechanical properties of the polycarbonate (PC)/carbon fiber (CF) composites with different initial fiber length, sizing effect of the fiber, fiber content and screw speed have been studied. PC/CF composites were prepared by twin screw extruder. In the studies of sizing effect of the fiber on the rheological properties of the PC/CF composites, the viscosities of the composites prepared with the sized carbon fibers gave higher values than that prepared with unsized carbon fibers because of the increase in the fiber length after extrusion for the sized fibers. From the results of the effect of screw speed on the rheological and mechanical properties of PC/CF composites, we found that the viscosity and tensile strength decreased with increasing screw speed. This is mainly due to that the fact that the fiber length after extrusion has been decreased from 163 to 148 μm with the increase of the screw speed from 100 to 200 rpm when the fiber content used in the composites is equal. From the above results, it is suggested that the fiber length after extrusion of the PC/CF composites has a strong effect on the rheological and mechanical properties of the composites. Also, a relationship among the initial fiber length, sizing effect of the fiber, fiber content and screw speed has been studied comprehensively for the PC/CF composites.

Relationship between fiber degradation and residence time distribution in the processing of long fiber reinforced thermoplastics

Long fiber reinforced thermoplastics (LFT) were processed by in-line compounding equipment with a modified single screw extruder. A pulse stimulus response technique using PET spheres as the tracer was adopted to obtain residence time distribution (RTD) of extrusion compounding. RTD curves were fitted by the model based on the supposition that extrusion compounding was the combination of plug flow and mixed flow. Characteristic parameters of RTD model includ- ing P the fraction of plug flow reactor (PFR) and d the fraction of dead volume of continuous stirred tank reactor (CSTR) were used to associate with fiber degradation presented by fiber length and dispersion. The effects of screw speed, mixing length and channel depth on RTD curves, and characteristic parameters of RTD models as well as their effects on the fiber degradation were investigated. The influence of shear force with different screw speeds and variable channel depth on fiber degradation was studied and the main impetus of fiber degradation was also presented. The optimal process for obtaining the balance of fiber length and dispersion was presented.

Effects of microcompounding process parameters on the properties of ABS/polyamide‐6 blends based nanocomposites

AbstractMelt intercalation method was applied to produce acrylonitrile‐butadiene‐styrene/polyamide‐6 (ABS/PA6) blends based organoclay nanocomposites using a conical twin‐screw microcompounder. The blend was compatibilized using a maleated olefinic copolymer. The effects of microcompounding conditions such as screw speed, screw rotation‐mode (co‐ or counter‐), and material parameters such as blend composition and clay loading level on the morphology of the blends, dispersibility of nanoparticles, and mechanical properties were investigated. Furthermore, corotating screws were modified to achieve elongational flow which is efficient for obtaining dispersive mixing. The morphology was examined by SEM analysis after preferential extraction of the minor phase. Subsequently, the SEM micrographs were quantitatively analyzed using image analyzer software. The morphology of the blends indicated that processing with counter‐rotation at a given screw speed yielded coarser morphology than that of processed with corotation. X‐ray diffraction analysis showed that highest level of exfoliation is observed with increasing PA6 content, at 200 rpm of screw speed and in corotation mode. Also, the effects of screw speed, screw rotation mode, and screw modification were discussed in terms of XRD responses of the nanocomposites. The aspect ratio of the clay particles which were measured by performing image analysis on TEM micrographs exhibited a variation with processing conditions and they are in accordance with the modulus of the nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Effect of brewers spent grain addition and screw speed on the selected physical and nutritional properties of an extruded snack

The effect of screw speed (100–300 rpm) and addition of brewers spent grain (BSG, 0–30% based on the maize flour used) on the approximate composition (crude protein, crude fat, total starch, crude fibre), physical (expansion, hardness, bulk density, SME, water absorption and solubility indexes), nutritional (total antioxidant capacity, TAC; total phenolic compounds, TPC; phytic acid, PA; protein in vitro digestibility, PIVD; resistant starch, RS) and colour (Hunter L, a, b) properties of an extruded snack food was investigated. A decrease in hardness was observed at increased screw speeds whereas scattered data was obtained with increasing BSG levels. Results indicated that addition of BSG resulted in reduced expansion and increased PA, PIVD and RS values ( P < 0.05). On the other hand, addition of BSG to the samples has no significant effect on the TAC and TPC values ( P < 0.05). Increased screw speeds resulted in increased expansion and decreased RS values ( P < 0.05). Screw speed has no significant effect on the TAC, TPC, colour, PA and PIVD values of BSG added samples ( P < 0.05). Addition of BSG caused a decrease in the Hunter L values giving darker samples.

Physical and sensory evaluation of a nutritionally balanced gluten-free extruded snack

The effect of screw speed (220–340 rpm) and feed rate (22.0–26.0 kg/h, db) on the firmness, expansion ratio, colour and sensory properties of a nutritionally balanced gluten-free extruded snack were investigated. Regression equations describing the effect of each variable on the responses were obtained. Results indicated that feed rate and screw speed both had an effect on the firmness of the product at 95% confidence interval (CI). The interaction between the two factors was also found to be significant at 95% CI. The effect of screw speed was significant whereas the quadratic effect of feed rate was found significant on the lateral expansion (95% CI). Lateral expansion increases as screw speed increases. The results indicated that changes in the extrusion variables did not affect the flavour and overall acceptability of the final product at 95% CI for the feed rate and screw speed ranges studied in this work.

Digital image processing for measurement of residence time distribution in a laboratory extruder

A non-labor intensive, non-destructive method based on image processing was developed to measure residence time distribution in a laboratory extrusion process. The a ∗ value (of L ∗ a ∗ b ∗ color space) was measured using image processing instead of a colorimeter to determine concentration of tracer in the product. The method was faster and less subject to human error. The a ∗ values obtained by the two methods correlated well with r 2 > 0.98 and MSE < 4.70. The parameters of the residence time distribution (RTD) were found to be similar. Effects of screw speed and barrel temperature on RTD as determined by the image processing method correlated well with the previously reported results. Increases in screw speed and temperature resulted in decreases in the mean residence time and increases in degree of mixing. A 3 × 2 factorial design with screw speeds of 80, 120 and 160 rpm and barrel temperatures of 120 and 160 °C was used for the experiment.