Effects Of Screw Configuration Research Articles

Effect of screw configuration and processing parameters on glass fiber residual length and properties of glass fiber reinforced polybutylene terephthalate composites

AbstractGlass fiber reinforced polybutylene terephthalate (GF‐PBT) composite is widely applied in automobile, electronic and electrical appliances, industrial machinery due to excellent toughness, mechanical properties, heat resistance, solvent resistance and processing fluidity. However, consistent with other glass fiber reinforced composites, glass fibers are easy to fractured and hard to be dispersed during processing, limiting its improvement of material performance. A series of studies on the factors, such as screw configuration, processing parameters, were carried out through eight different screw configurations with five different screw elements in twin‐screw extruder (TSE) to evaluate the effects caused by processing stress, screw speed, mixing section temperature, feeding rate and processing length in GF‐PBT composite. The rotation number Nt was innovatively introduced and a novel exponential model was established to successfully predict the glass fiber residual length in the PBT system. The average glass fiber residual length at different axial positions of the screw during the processing was evaluated through the emergency stop experiment and the main reason for the glass fiber fracture was revealed. The results showed that the screw configuration affects the mechanical properties through the dispersion of glass fiber bundle, the residual length of glass fiber and the uniformity of length distribution, while the process parameters have little effect on the tensile strength and elongation at break, and have a greater impact on the notch impact strength, bending strength and bending modulus in PBT system.

Process Simulation of Twin‐Screw Granulator: Effect of Screw Configuration on Size Distribution

AbstractThe effect of screw configuration on granule size distribution (GSD) using gPROMS FormulatedProduct (gFP) software to perform optimization, estimation of complex processes, and analyses is evaluated. Twin‐screw granulation modeling was used to investigate the contribution of screw configuration and liquid‐to‐solid (L/S) ratio on GSD. Lactose and Avicel were the granulating materials. Twelve different configurations were investigated under three feed rates as consistent with literature and at various L/S ratios. Results indicate that kneading elements promote the recovery of 100–1000 µm granules while reducing the production of oversized granules. Higher feed rates support the production of fines and agglomerates, while a low feed rate produces 100–1000 µm granules.

Continuous film casting of polycarbonate/single‐walled carbon nanotubes composites with ultrasound‐assisted twin‐screw extruder: Effect of screw configuration

AbstractPolymer films are widely used in various industries, and incorporation of nanofillers into polymer films can give much more versatility in their applications. Polymer/carbon nanotubes (CNTs) composite films with good electrical conductivity can easily find applications in anti‐static or electrostatic discharge (ESD) protection. In the present study, efforts were devoted to investigate novel ultrasound‐assisted twin‐screw extrusion technology on improving the dispersion and distribution of single‐walled carbon nanotubes (SWNTs) in polycarbonate (PC) composites films via extrusion process. As a key processing parameter, effect of screw configuration on the performance of the composite films were systematically studied. Electrical, rheological, morphological and mechanical properties were characterized to illustrate the processing‐structure–property relationship during continuous film casting of PC/SWNTs composites with ultrasound‐assisted twin‐screw extruder. Results indicated that the screw configuration containing more kneading blocks led to better SWNTs dispersion and distribution, while the effect of ultrasound was more prominent in screw design with less kneading blocks.

The effect of screw configuration and formulation variables on liquid requirements and granule quality in a continuous twin screw wet granulation process

The effect of two screw configurations with varying stagger angle was evaluated on the liquid amount required to produce good quality granules for a highly (mannitol-based) and a poorly (DCP-based) soluble formulation containing different binders. It is generally known that the use of a higher liquid amount improves the granule quality in twin screw granulation. However, from an industrial point of view, lower liquid amounts for effective granulation are preferred, as this speeds up the production time as less time is required for drying. A screw configuration containing mixing elements with a higher stagger angle (90°) produced granules with a lower friability and a larger size at lower liquid-to-solid ratios compared to a screw configuration with all the mixing elements staggered at 60°. For each binder, incorporating a highly soluble filler into the formulation allowed granulation at lower liquid-to-solid ratios compared to a filler having a poorer aqueous solubility. The different binder types affected the granule quality and liquid requirements for granulation differently. Furthermore, similar granule quality between (partially) pregelatinized starches and in situ gelatinized starches was achieved.

Effect of Screw Configuration on the Rate of Correction for Guided Growth Using the Tension-band Plate.

This study investigated the effect of screw configuration on the rate of correction of coronal angular deformity of the knee joint in children who underwent guided growth using the tension-band plate. Consecutive patients (76 patients with 154 physes; mean age: 11.8±2.2 y) who underwent guided growth using the tension-band plate for coronal angular deformity (genu varum or genu valgum) were included. The mechanical lateral distal femoral angle, mechanical medial proximal tibial angle, and screw angle were measured from the teleroentgenograms of preoperative and postoperative periodic follow-up visits. The mean initial screw angle and the mean rate of correction were 16.7±10.5 degrees and 6.5±5.3 degrees per year, respectively. The rate of correction was significantly affected by age at surgery, sex, physis treated, severity of deformity, and rate of change in screw angle (all P<0.001). However, the initial screw angle and type of deformity did not affect the rate of correction. The rate of correction per year was 3.6 degrees higher in boys than in girls and 2.8 degrees higher in the distal femur than in the proximal tibia. A 1 degree increase in the rate of change in screw angle was associated with a 0.5 degree increase in the correction rate. Screw angle significantly increased with follow-up duration (P<0.001) and the change in screw angle was significantly affected by age, sex, and physis treated (all P<0.001). This study demonstrated that screw configuration did not affect the correction rate of coronal angular deformity for guided growth using the tension-band plate. Therefore, surgeons only need to insert the screws according to anatomic restriction, not considering the screw configuration when using the tension-band plate for guided growth in children. Prognostic level III.

Image processing for detecting complete two dimensional properties’ distribution of granules produced in twin screw granulation

In this study, an image processing technique is implemented to measure complete two-dimensional particle size and liquid content distribution (2D-distribution) of the granules produced in twin screw granulation (TSG). The effects of liquid binder viscosity and liquid to solid ratio (L/S) on the 2D-distribution, and the residence time distribution were studied. The effect of screw configuration on granule formation at different conditions was also investigated, were the mean residence time distribution (MRTD) in conveying elements decreases with the increase of L/S ratio and viscosity. While in kneading elements the MRTD decreases with the increase of L/S and increases with the increase of viscosity. The mean liquid saturation level of the granule is exponentially related to its size. As well, the increase in binder viscosity and L/S ratio leads to more uneven/bi-model particle size distribution (PSD) in the conveying elements, while kneading elements change the initial bi-model PSDs into more homogenous mono-model like distributions.

Effects of screw configuration on chemical properties and ginsenosides content of extruded ginseng.

BackgroundThe purpose of this study was to investigate the effects of screw configuration on chemical properties and ginsenosides content of extruded ginseng and to select the most suitable screw configuration for the processing of ginseng.MethodThe extrusion conditions were set as follows: moisture content (20%), barrel temperature (140°C), screw speed (200 rpm), and feeding rate (100 g/min).ResultThe extruded ginseng of screw configuration 6 has the highest DPPH free radical scavenging rate, reducing power and total phenol, which is the most suitable configuration for the development of ginseng extract products. In addition, the extruded ginseng of screw configuration 9 has the highest content of total saponin, and the content of rare ginsenoside Rg3 which is scarcely present in the ginseng raw material powder was significantly increased. This intended that twin‐screw extrusion process enables the mutual conversion between ginsenosides and rare ginsenoside Rg3 had achieved.ConclusionThe extrusion process promotes the development and utilization of ginseng and provides theoretical basis for the design and development of screw configuration of twin‐screw extruded ginseng.

Finite Element-Predicted Effects of Screw Configuration in Proximal Humerus Fracture Fixation.

Internal fixation with the use of locking plates is the standard surgical treatment for proximal humerus fractures, one of the most common fractures in the elderly. Screw cut-out through weak cancellous bone of the humeral head, which ultimately results in collapse of the fixed fracture, is the leading cause of failure and revision surgery. In an attempt to address this problem, surgeons often attach the plate with as many locking screws as possible into the proximal fragment. It is not thoroughly understood which screws and screw combinations play the most critical roles in fixation stability. This study conducted a detailed finite element analysis to evaluate critical parameters associated with screw cut-out failure. Several clinically relevant screw configurations and fracture gap sizes were modeled. Findings demonstrate that in perfectly reduced fracture cases, variation of the screw configurations had minor influence on mechanical stability of the fixation. The effects of screw configurations became substantial with the existence of a fracture gap. Interestingly, the use of a single anterior calcar screw was as effective as utilizing two screws to support the calcar. On the other hand, the variation in calcar screw configuration had minor influence on the fixation stability when all the proximal screws (A-D level) were filled. This study evaluates different screw configurations to further understand the influence of combined screw configurations and the individual screws on the fixation stability. Findings from this study may help decrease the risk for screw cut-out with proximal humerus varus collapse and the associated economic costs.

Effect of screw configuration on the dispersion and properties of polypropylene/multiwalled carbon nanotube composite

AbstractThe effect of extruder screw configuration on the dispersion and properties of compatibilised polypropylene (PP)/multi‐walled carbon nanotube (MCNT) composite is investigated. Three principle screw designs with mainly conveying elements (medium intensity), kneading elements (high intensity), and folding elements (chaotic mixing) were used to prepare polypropylene nanocomposites containing 4wt% of maleic anhydride grafted polypropylene (MAH‐g‐PP) compatibilizer and different nanotube loadings. The effect of each screw configuration and nanotube loading on the tensile, rheological, and electrical properties of the nanocomposites were studied. The screw configurations were found to have a strong influence on the electrical resistivity while only slightly affected the tensile properties of the nanocomposites. Scanning electron microscopy examinations showed that the use of screw configuration consisting of kneading elements promoted the dispersion of nanotubes and resulted in a low electrical percolation at 2wt% of MCNT.

Analysing the effect of screw configuration using a stochastic twin-screw granulation model

In this work, a framework for modelling twin-screw granulation processes with variable screw configurations using a high-dimensional stochastic population balance method is presented. A modular compartmental approach is presented and a method for estimating residence times for model compartments based on screw element geometry is introduced. The model includes particle mechanisms for nucleation, primary particle layering, coalescence, breakage, and consolidation. A new twin-screw breakage model is introduced, which takes into account the differing breakage dynamics between two types of screw element. Additionally, a new sub-model for the layering of primary particles onto larger agglomerates is presented. The resulting model is used to simulate a twin-screw system with a number of different screw configurations and the predictive power of the model is assessed through comparison with an existing experimental data set in the literature. For most of the screw configurations simulated, the model predicts the product particle size distribution at large particle sizes with a reasonable degree of accuracy. However, the model has a tendency to over-predict the amount of fines in the final product. Nevertheless, the model qualitatively captures the reduction in fines associated with an increase in the number of kneading elements, as observed experimentally. Based on model results, a number of key areas for future model development are identified and discussed.

Effects of extruder screw configurations on thermal properties of glass fiber‐reinforced polyamide 6 composites throughout the direct long‐fiber‐reinforced thermoplastics process

The direct long‐fiber‐reinforced thermoplastics (D‐LFT) process is a series of processes involving two twin‐screw extruders, a conveyer, and a compression molding machine. The second twin‐screw extruder is designed for mixing continuous fibers with polymer melt and plays an important role in the D‐LFT process. This study investigates effects of the screw configurations of the second extruder on thermal properties of glass fiber‐reinforced polyamide 6 (PA6) composites throughout the D‐LFT process. Two screw configurations, which generate low and high shear stress in composite melt (named the conveying and mixing screws, respectively), were used in the second twin‐screw extruder. Samples were taken from four different locations along the D‐LFT process and characterized using triple detection gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results suggested that the molecular weight of the PA6 matrix increased in the later stages of the D‐LFT process (i.e., after the second extruder) by branching of PA6 molecules. In addition, the mixing screw decreased the molecular weight of the PA6 matrix more than the conveying screw. However, such a decrease in molecular weight had little influence on the thermal stability and crystallization behavior of the composites. POLYM. COMPOS., 40:3500–3509, 2019. © 2019 Society of Plastics Engineers

Effects of Screw Configuration, Screw Speed, and Stearic Acid Addition on the Functional Properties and Structural Characteristics of Maize Starch Extrudates

Effects of Screw Configuration, Screw Speed, and Stearic Acid Addition on the Functional Properties and Structural Characteristics of Maize Starch Extrudates

Effects of chain-extending stabilizer on bioplastic poly(lactic acid)/polyamide blends compatibilized by reactive extrusion

The immiscible bio-plastic blend of poly(lactic acid) (PLA) and polyamide11 (PA11 or Nylon11) was compatibilized, using a catalyzed the ester-amide interchange chemical reaction during reactive extrusion. The effects of screw configuration on mixing and reaction optimization were explored. It was found that effective mixing and minimized degradation were achieved when kneading elements were installed only near the die end of the extruder rather than near the beginning of the melt section. However, significant degradation of PLA could not be avoided during processing, which led to a decrease in mechanical strength of blend. To prevent the molecular weight reduction, tris(nonylphenyl) phosphite (TNPP) stabilizer was introduced to improve the thermal stability of PLA matrix. Improvement to both tensile strength and elongation were achieved in the resulting PLA/PA11/TsOH/TNPP blend.

Effects of Screw Configuration on the Preload Force of Implant-Abutment Screws.

The aim of this study was to investigate the effects of tightening torque, screw head angle, and thread number on the preload force of abutment screws. The test specimens consisted of three self-manufactured components (ie, a thread sleeve serving as an implant analog, an abutment analog, and an abutment screw). The abutment screws were fabricated with metric M1.6 external threads. The thread number varied between one and seven threads. The screw head angles were produced in eight varying angles (30 to 180 degrees). A sensor unit simultaneously measured the preload force of the screw and the torsion moment inside the screw shank. The tightening of the screw with the torque wrench was performed in five steps (15 to 35 Ncm). The torque wrench was calibrated before each step. Only the tightening torque and screw head angle affected the resulting preload force of the implant-abutment connection. The thread number had no effect. There was an approximately linear correlation between tightening torque and preload force. The tightening torque and screw head angle were the only study parameters that affected the resulting preload force of the abutment screw. The results obtained from this experiment are valid only for a single torque condition. Further investigations are needed that analyze other parameters that affect preload force. Once these parameters are known, it will add value for a strong, but detachable connection between the implant and abutment. Short implants and flat-to-flat connections especially will benefit significantly from this knowledge.

Effect of screw configuration on the dispersion of nanofillers in thermoset polymers

Abstract This paper deals with the study of screw configuration for dispersing nanofillers in thermoset polymers using an intermesh co-rotating twin screw extruder. The influence of kneading elements on the dispersion of nanoclay in epoxy was examined using 10 different screw configurations. Nanoclay was dispersed in epoxy at a barrel temperature of 5°C and a screw speed of 100 rpm. The combination of right hand kneading block and three/four lobed kneading blocks resulted in uniform dispersion of nanofiller. Positive staggered angle with right hand kneading elements yielded uniform dispersion of the nanofiller. Mechanical properties of epoxy nanocomposites processed with these configurations were better than those of neat epoxy. Excessive shear was associated with four lobed kneading block (4KB)/4KB configuration and hence degradation of polymers leading to shorter chains, whereas inadequate shearing in neutral kneading block (NKB)/NKB configuration led to agglomerations. These observations were evidenced by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

Age-related optimization of screw placement for reduced loosening risk in locked plating.

When using locked plating for bone fracture fixation, screw loosening is reported as one of the most frequent complications and is commonly attributed to an incorrect choice of screw configuration. Choosing a patient-optimized screw configuration is not straightforward as there are many interdependent variables that affect device performance. The aim of the study was to evaluate the influence that locking screw configuration has on loosening risk and how this is influenced by bone quality. This study uses finite element models that incorporate cortical bone heterogeneity, orthotropy, and geometrical nonlinearity to examine the effect of screw configuration on variables associated with loosening and interfragmentary motion. Strain levels within the bone were used as indicators of regions that may undergo loosening. The study found that, in healthy bone under axial loading, the most important variables influencing strain levels within the bone were the size of the bridging span (working length) and the plate rigidity. Unlike healthy bone, osteoporotic bone was found to be particularly sensitive to the spacing of the screws within the plate. Using two empty screw holes between the screws closest to the fracture was found to reduce the strain levels at the first screw by 49% in osteoporotic bone (compared to only 2.4% in healthy bone). The study also found that under torsional loading the total number of screws used was the most important variable with a 59% reduction in the strain around the screws closest to the fracture when using six rather than four screws in osteoporotic bone. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1856-1864, 2016.

Xylose removal from lignocellulosic biomass via a twin-screw extruder: The effects of screw configurations and operating conditions

It was the objective of this study to evaluate the feasibility of separating xylose from lignocellulosic biomass (steam-exploded corncobs) in a co-rotating twin-screw extruder, through water addition and solid–liquid separation. Eight screw configuration profiles were evaluated to define the best performance on xylose recovery. Subsequently, operating conditions (barrel temperature, screw speed and water flow rate) were examined with respect to xylose recovery and specific mechanical energy consumption of the motor drive. It was found that liquid/solid separation highly depended on the position and spacing of reverse screw elements. For a given configuration the xylose recovery increased with increases in temperature and was only weakly correlated with the agitation rate. The xylose recovery went through a maximum when the flow rate of additional water was approximately 0.33 kg h−1 water per kg h−1 biomass feed rate. Furthermore, operating conditions influenced the specific mechanical energy consumption of the motor drive, allowing to minimize the amount of energy needed to obtain a prescribed xylose removal.

Understanding the Processing Window of Hypromellose Acetate Succinate for Hot‐Melt Extrusion, Part I: Polymer Characterization and Hot‐Melt Extrusion

ABSTRACTThe aims of this study were to assess the processing window of hypromellose acetate succinate (HPMCAS) as a polymeric carrier for hot‐melt extrusion, and to investigate the effect of screw configuration and processing parameters on the physicochemical properties of HPMCAS extrudates. The processability was investigated using a Brabender® mixer and a Pharma 11 Twin Screw Extruder. HPMCAS extrudates were characterized with regard to glass transition temperature, true density, yellowness index, crystallinity, morphology, and free succinic acid/acetic acid/succinoyl group/acetyl group content. The specific energy input and mean residence time were also calculated and correlated to the physicochemical properties of final extrudates. Additionally, the effect of the die opening size of the twin screw extruder was investigated. The glass transition temperature of HPMCAS was found to be 137 and 133°C, using dynamic mechanical analyzer and oscillatory rheometer, respectively. HPMCAS demonstrated a shear thinning behavior at all temperatures tested (150, 160, and 170°C). The process conditions, screw configurations, as well as the diameter of die opening significantly affect the amount of free acetic acid and succinic acid. With a modified screw configuration and 1‐mm die, the amounts of free acetic acid and succinic acid from the material processed at 180°C were 0.114% and 0.337%, respectively. Moreover, when the die was removed, the amounts of free acetic acid and succinic acid were further reduced to 0.084% and 0.294%, respectively. In conclusion, we successfully extruded HPMCAS at a temperature as low as 130°C and up to 180°C without any significant thermal degradation.

Ultrasonic treatment of PP/CNT composites during twin‐screw extrusion: Effect of screw configuration

PP/CNT composites were prepared by means of an ultrasonic twin extruder with three screw configurations at ultrasonic amplitudes up to 13 μm to compare their efficiency in dispersing CNT in PP. Using these screw configurations, the pressure in the ultrasonic treatment zone was varied in order to elucidate the effect of pressure on ultrasonic cavitation behavior in PP and PP/CNT composites. Rheological and mechanical behaviors were analyzed to reflect the dispersion of CNT. The results indicated that the dispersion of CNT in PP is more related to the number of kneading elements in the screw configuration and less to the residence time. This was explained by simulating the mixing effect using the flow analysis network. Comparison of the complex viscosities of untreated and treated PP indicated that at the same amplitude of ultrasonic treatment, PP degraded more at lower ambient pressure. At the lowest ambient pressure, the cavitation in the polymer matrix was intense at the highest amplitude but it had not always led to the best dispersion due to the suppression of the cavitation in the agglomerates. Therefore, the ultrasonic treatment increased the dispersion level of CNT in PP with the best improvement not always occurring at the highest amplitude. Composites prepared at an ultrasonic amplitude of 10 μm in the screw configuration providing an intermediate pressure exhibited elongation at break as high as 320% compared to 247% for the untreated composites. POLYM. COMPOS., 38:2695–2706, 2017. © 2015 Society of Plastics Engineers

The effects of screw configuration on the screw fill degree and special mechanical energy in twin-screw extruder for high-moisture texturised defatted soybean meal

To control the mechanical energy output by adjusting the screw configuration during soybean protein extrusion texturisation, the relationship between the screw configuration and the special mechanical energy was investigated. Different types of screw elements, element lengths and positions were designed and configured, while the other parameters were kept unchanged. The screw fill degree and specific mechanical energy output were detected. The results demonstrate that when the helix angle of conveying elements turns from forward (45°) to reverse (−37.5°), the disc width of the kneading elements decreases from 7.5mm to 5mm, and when the disc stagger angle turns from forward (45°) and forward (90°) to reverse (−45°), the screw fill degree and specific mechanical energy increase. When the length of the reverse kneading element increases, the screw fill degree and specific mechanical energy increase. When the distance between the reversing knead element and the die increases or the element space between the reversing knead element increases, the specific mechanical energy appears to decrease. Thus, the elements with reverse helix or stagger angles, narrow kneading disc, long length and flow-restricting ability increase the screw fill degree and induce high special mechanical energy. The special mechanical energy increases when the reverse kneading element is located at the screw position where the material viscosity is relatively high during extrusion.