Counter-rotating Twin Screw Extruder Research Articles

Effect of antioxidants and fire retardants as mineral fillers on the physical and mechanical properties of high loading hybrid biocomposites reinforced with rice husks and sawdust

In this study, the physical and mechanical properties of recycled high density polyethylene (rHDPE) reinforced with a high loading hybrid of rice husks and sawdust were evaluated, and the effect of antioxidants (AOs) and fire retardants (FRs) as additives were investigated. The rHDPE and natural fibres were compounded into pellets by a compounder, then the pellets were extruded using a counter-rotating twin-screw extruder and test specimens were prepared using the hot and cold press process. Maleic anhydride was used as a coupling agent to increase the adhesion of the fibre/matrix interface. The thermal behaviour of biocomposites was evaluated using a thermal gravimetric analyser (TGA). The mechanical behaviour was measured using tensile, flexural and impact testing in comparison with non-added AOs and FRs. From the study, samples with 0.5wt.% of antioxidants and 20wt.% of fire retardants produce the most reasonable strength and elasticity of composites. Furthermore, the effect of the presence of antioxidants and fire retardants on water uptake was minimal. Microstructure analysis of the fractured surfaces of biocomposites confirmed improved interfacial bonding.

The effects of poplar bark and wood content on the mechanical properties of wood-polypropylene composites

Bark, as a residue from trees, is mostly used for thermal energy production, but a better utilization of this resource was considered as an alternative raw material for wood-plastic composites (WPCs). The influence of bark, wood, and blending of bark and wood flour content of the poplar tree on the mechanical characteristics of WPCs were investigated. Wood and bark flours with 2% maleic anhydride-grafted polypropylene (MAPP) and polypropylene were compounded into pellets using a counter-rotating twin-screw extruder, and test specimens were prepared by injection molding. The results showed that both bark fiber and wood flour increased mechanical strength (flexural strength (MOR), flexural modulus (MOE), tensile modulus, and tensile strength) significantly (P<0.05). Composites made with bark flour exhibited lower mechanical strength compared to those made with wood flour and wood flour/bark flour. Differences in chemical composition between bark and wood, fines, low aspect ratio (length/width) of bark flour, delamination between fines and matrix, and the lower intrinsic fiber strength of bark fibers compared to wood fibers are good explanations for this demarcation. The notched impact strength of all reinforced composites was significantly lower than neat polypropylene (P < 0.05).

Effect of Flame Retardants on Wood Plastic Composites-HDPE Based

Recently, research on natural fiber reinforced polymer composites has gained importance due to the abundant sources of fibers that can be obtained at very low cost. In this study, wood plastic composite (WPC) materials is made by mixing (compounding) high density polyethylene (HDPE) and (ligno) cellulose fiber, i.e. rice husk reinforced with sawdust have been manufactured using a high volume process using counter rotating twin screw extruder. Different fire retardant agents have been employed in order to improve fire behavior in this study. The flammability and thermal stability of WPC-HDPE based in different compositions have been carried out by fire test method according to ASTM D635-06 and evaluated by thermo gravimetric analysis respectively. The properties of flexural strength and impact strength were also included.

Simulation of screw pumping characteristics for intermeshing counter-rotating twin screw extruders

Intermeshing counter-rotating twin screw extruders play an important role in polymer processing, especially for the extrusion of profiles and pipe, largely from polyvinyl chloride. There has been little effort on flow modeling of these machines and most of this has involved representing the machine as a “leaky” positive displacement pump and estimating leakages. In recent years, M.H. Hong and the authors have developed more general methods of simulation of flow in this machine and both applied and experimentally verified it for a few designs. Here we extend these efforts to a broader range of screw designs, especially with deeper screw channels where transverse shearing induced by the flights is important. Calculations are done for isothermal power law fluids. The results are compared with experiment. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Morphological Characterisation and Dynamic Rheology of Nano-Structured Blends of Polystyrene and SEBS

Polystyrene homopolymer (hPS) was melt-blended with styreneethylene/ butylene-styrene (SEBS) in a counter-rotating twin-screw extruder to produce hPS/SEBS blends. The morphology of the hPS/SEBS blends was investigated using environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM). The dynamic rheological behaviour of the blends was studied using a parallel plate rheometer. TEM and ESEM images of the hPS/SEBS blends showed three different morphologies at three different SEBS concentration ranges. When SEBS concentration was less than 30 wt%, the hPS-rich blends hPS/SEBS 90/10 and 80/20 showed a droplet/matrix morphology. When SEBS concentration was between 30 and 70 wt%, the blend morphology revealed a co-continuous nano-structure. At SEBS concentrations 80 wt% and above, TEM images of the SEBS-rich blends showed that the homopolymer hPS was absorbed within the bulk of SEBS, resulting in a modification of its original microstructure. Dynamic rheological tests showed that the blend morphology had significant effect on their rheological behaviour at low frequencies.

A Global Model for Closely Intermeshing Counter-rotating Twin Screw Extruders with Flood Feeding

Abstract A composite model has been developed to simulate the extrusion process for intermeshing counter-rotating twin-screw extruders. An experimentally based melting model, solids conveying model, and new improved metering model, were combined to develop this formulation. The procedure for global design of a flood feed intermeshing counter-rotating twin screw extruder is presented. Illustrative calculations are made for polyvinyl chloride and high density polyethylene in this type of machines with different screw designs. Computations are made for axial variation of the fill factor, pressure, temperature and melting profiles. Simulations were found to match with experimental results well. The model was also applied to scale-up.

Effect of Thermo-Mechanical Degradation of Polypropylene on Hygroscopic Characteristics of Wood Flour-Polypropylene Composites

In this research, the influence of thermo-mechanical degradation of polypropylene (PP) on water absorption and thickness swelling of beech wood flour–PP composites were studied. For this purpose, a virgin PP was thermo-mechanically degraded by two times extrusion under controlled conditions. The results showed that the melt flow index, water absorption and thickness swelling of PP significantly increase by extrusion and re-extrusion. The virgin PP and degraded polypropylene were compounded with wood flour (at 60% by weight wood flour loading) in a counter-rotating twin-screw extruder in presence or absence of MAPP to produce wood flour–PP composites. From the results, the composites containing recycled PP exhibited higher water absorption and thickness swelling. The use of MAPP decreased water absorption and thickness swelling in composites made of virgin or recycled PP.

Hybridization Effect of Glass Fibre on Mechanical, Morphological and Thermal Properties of Polypropylene-Bamboo/Glass Fibre Hybrid Composites

Polypropylene/bamboo fibre-reinforced composites (BFRP) and polypropylene-bamboo/glass fibre based hybrid composites (BGRP) using an intermeshing counter-rotating twin-screw extruder followed by injection moulding in which maleic anhydride grafted polypropylene (MAPP) was used as a compatibilizer. The effect of hybridization on the mechanical performance of hybrid composites has been assessed. It was observed that replacement of 15 wt.% of bamboo fibre by 15 wt.% of glass fibre with 2 wt.% of MAPP on a total amount of 30 wt.% of fibre content showed optimum mechanical performance. The water uptake of the hybrid composites was also found to be less than that of their unhybridized counterpart. The crystallization, melting behaviour and thermal stability of the hybrid composites were investigated employing differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA ). TGA thermograms showed an increase in thermal stability of the matrix polymer after incorporation of bamboo and glass fibres, confirming the effect of hybridization and efficient fibre matrix interfacial adhesion. The fibre-matrix interfacial morphology of the tensile fractured specimens was studied using scanning electron microscopy (SEM) which showed less fibre pullout and fewer gaps between the fibre and the base matrix in case of MAPP-treated hybrid composites.

Performance and thermal behavior of wood plastic composite produced by nonmetals of pulverized waste printed circuit boards

A new kind of wood plastic composite (WPC) was produced by compounding nonmetals from waste printed circuit boards (PCBs), recycled high-density polyethylene (HDPE), wood flour and other additives. The blended granules were then extruded to profile WPC products by a conical counter-rotating twin-screw extruder. The results showed that the addition of nonmetals in WPC improved the flexural strength and tensile strength and reduced screw withdrawal strength. When the added content of nonmetals was 40%, the flexural strength of WPC was 23.4 MPa, tensile strength was 9.6 MPa, impact strength was 3.03 J/m 2 and screw withdrawal strength was 1755 N. Dimensional stability and fourier transform infrared spectroscopy (FTIR) of WPC panels were also investigated. Furthermore, thermogravimetric analysis showed that thermal degradation of WPC mainly included two steps. The first step was the decomposition of wood flour and nonmetals from 260 to 380 °C, and the second step was the decomposition of HDPE from 440 to 500 °C. The performance and thermal behavior of WPC produced by nonmetals from PCBs achieves the standard of WPC. It offers a novel method to treat nonmetals from PCBs.

Characterization of HDPE/MMT-Based Nanocomposites

A series of HDPE/MMT nanocomposites with different proportions of compatibilizers, PE-g-MAH (AC573A and 5TP409/E) were prepared in a counter rotating twin screw extruder. The effect of nanoclay loading, compatibilizer type and amount was examined. The work was carried out using a specific grade of HDPE recommended for blow-moulding applications and modification of the same by blending with selected polymer and nanofiller to achieve the desired properties. The composition containing higher percentage of nanoclay showed improvement in mechanical properties. About 17% in tensile modulus and about 20% increase in flexural modulus were observed with high-viscous compatibilizer. The dispersion behaviour of nanoclay in PE matrix was studied using X-ray diffraction and transmission electron microscopy. It was clear from WXRD that in all nanocomposite samples, the peaks were shifted to lower 2 values implying that the d-spacing increases and that intercalation occurred. Low molecular weight compatibilizer PE-g-MA resulted in better intercalation than high molecular weight compatibilizer. It was observed that in the case of 5% AC573A loading, there was slight decrease in d-spacing value which indicated that some exfoliation also occurred in nanocomposite. Nanocomposite containing PE-g-MAH is higher concentration gives better dispersion than at low concentration. TEM results show that PE-g-MAH (AC573A) at 5% loading is more efficient as compatibilizer (not many aggregates seen) than other compositions.

The effects of fiber length and fiber loading on the mechanical properties of wood-plastic (polypropylene) composites

This study examined the effects of wood pulp fiber length (short, medium, and long), and fiber loading (27%, 37%, 47%, and 0% [non-reinforced PP]) with 3% maleic anhydride-grafted polypropylene on the mechanical properties of wood-plastic composites (WPCs). Polypropylene and fibers were compounded into pellets using a counter-rotating twin-screw extruder and test specimens were prepared by injection molding. The results show that increases in fiber length and fiber loading significantly increased (P < 0.05) the mechanical properties of the WPCs (MOE and tensile modulus). The behavior of the composites against MOR and impact strength varied according to fiber length and loading level. In general, the tensile strength was observed to be the same.

Eigenschaften von extrudierten Holz-Kunststoff-Werkstoffen auf Basis von Refiner-(TMP-)Fasern und Hanffasern

At present, wood particles (wood flour) with a low aspect ratio are mostly used as fillers in wood-plastic composites (WPC). Reinforcement of WPC and improved strength properties may be achieved by using real wood fibres with a high aspect ratio. WPC based on 70% (wt.) refiner (TMP) wood fibres and mechanically processed hemp fibres were extruded in a two-step process. Eleven compounds based on the two natural fibre types were prepared using a thermokinetic mixer and extruded in a conical, counter-rotating twin-screw extruder. Additional formulation components were polypropylene fibres, maleic anhydride-modified polypropylene (MAPP) and lubricant. It was determined that compounding in a thermokinetic mixer is a useful step for processing of WPC with refiner and hemp fibres as little fibre damage occurred. However, during extrusion, both natural fibre types were severely shortened due to strong shear forces, and homogeneous dispersion of fibres in the matrix was not achieved. WPC based on hemp fibres displayed the best strength properties of the formulations tested. Current extruder screw and die configurations need to be modified to achieve improved fibre reinforcement and to create new, structurally demanding applications for WPC. Using dynamic mechanical analysis, fibre-matrix adhesion of WPC was investigated, and activation energies for glass transition of selected formulations were calculated. Activation energy for formulations containing MAPP was higher than for WPC without MAPP. This indicates that better fibre-matrix adhesion was achieved in formulations with MAPP.

Effect of Thermomechanical Degradation of Polypropylene on Mechanical Properties of Wood-Polypropylene Composites

In this research, the influence of thermomechanically degraded polypropylene (PP) on mechanical properties of beech sawdust-PP composites was studied. For this purpose, a virgin PP (VPP) was thermomechanically degraded by two times extrusion under controlled conditions in a twin-screw extruder at a rotor speed of 100 rpm and a temperature of 190°C. The results showed that melt flow index, flexural modulus, and hardness of PP were significantly increased by extrusion and re-extrusion of VPP. The PP (virgin and recycled PP in each stage) and beech sawdust were compounded at 60% weight sawdust loading in a counter-rotating twin-screw extruder in the presence or absence of maleated polypropylene (MAPP) to produce sawdust-PP composites. The nominal cross section and density of the manufactured composites were 70 × 10 mm2 and 1 g/cm3, respectively. From the results, the composites containing recycled PP exhibited higher flexural properties and hardness and lower impact strength. In the presence of MAPP, all mechanical properties increased.

Influence of short bamboo/glass fiber on the thermal, dynamic mechanical and rheological properties of polypropylene hybrid composites

The present article summarizes the development of polypropylene-bamboo/glass fiber reinforced hybrid composites (BGRP) using an intermeshing counter rotating twin screw extruder followed by injection molding. Maleic anhydride grafted polypropylene (MAPP) has been used as a coupling agent to improve the interfacial interaction between the fibers and matrix. The crystallization and melting behavior were investigated employing differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) indicates an increase in thermal stability of the matrix polymer with incorporation of bamboo and glass fibers, confirming the effect of hybridization and efficient fiber matrix interfacial adhesion. The dynamic mechanical analysis (DMA) showed an increase in storage modulus ( E′) indicating higher stiffness in case of hybrid composites as compared with untreated composites and virgin matrix. The rheological behavior of the hybrid composites has also been studied using time–temperature superposition (TTS) principle and corresponding viscoelastic master curves have been constructed.

Preparation and Properties of Polypropylene/Vapor Grown Carbon Fiber Composite Monofilaments by Melt Compounding

Polypropylene (PP)/vapor grown carbon fiber (VGCF) composites by melt compounding using a counter-rotating twin screw extruder were prepared, then by melt spinning PP/VGCF monofilaments with a high draw ratio of 9 were obtained. The properties and structure of the PP/VGCF composites and monofilaments were characterized by tensile testing, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Increasing the aspect and draw ratios resulted in an increase in the tensile strength of PP/VGCF monofilaments. The improvement of the tensile strength was observed for the addition of a small amount of 1 wt%, however, it was not observed for the addition of 3 wt%. Although the composites continued to be aggregates, VGCF was found to disperse in the PP matrix and increased the nucleation speed of the composite monofilaments, thereby leading to an increase in the crystallization rate of the as-spun monofilament owing to nanoscale structures formed from VGCF by drawing.

Properties of Polystyrene/Organoclay Composites Prepared by Melt Compounding Using a Twin-screw Extruder; Poly (styrene-&lt;I&gt;co&lt;/I&gt;-vinyloxazoline)-based Masterbatch Approach

We tried to prepare Polystyrene (PS) /Organoclay nanocomposites by melt compounding using a counter-rotating twin-screw extruder. The effects of a masterbatch process using Poly (styrene-co-vinyloxazolin)(OPS)-based masterbatch on the properties of prepared composites were investigated in this study. These composites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The mechanical properties were assessed by tensile testing, and the thermal properties of the composites were analyzed by differential scanning calorimetry (DSC). The d002 distance of clay platelets in the case of using masterbatch decreases with an increase in clay content included in the masterbatch. The values of Young's modulus and the glass transition temperature (Tg) of composites were the highest in the case of using masterbatch with 20 wt% clay content (OPS:organoclay= 4:1). This result implies the existence of optimal clay content in preparing a masterbatch for PS/OPS/organoclay composites with good performance. In addition, the Young's modulus and Tg of the composites showed the highest values when PS with the highest viscosity was used.

Polypropylene—Bamboo/Glass Fiber Hybrid Composites: Fabrication and Analysis of Mechanical, Morphological, Thermal, and Dynamic Mechanical Behavior

Hybrid composites of polypropylene reinforced with bamboo and glass fibers (BGRP) were fabricated using an intermeshing counter rotating twin screw extruder followed by injection molding. Maleic anhydride grafted polypropylene (MAPP) has been used as a coupling agent to improve the interfacial interaction between the fibers and matrix. The mechanical properties of the hybrid composites were studied from tensile, flexural, and impact tests. Mechanical tests indicated an increase in tensile, flexural, and impact strength of the BGRP hybrid composites at a bamboo:glass fiber ratio of 15:15 ratio in the presence of 2 wt% of MAPP. Nearly, 69, 86, and 83% increase in tensile flexural and impact strength respectively has been observed as compared with virgin PP. The fiber matrix interfacial morphology of the tensile fractured specimens was studied using scanning electron microscopy (SEM) which showed less fiber pullout and comparatively less gaps between the fiber and the base matrix in the case of MAPP treated hybrid composites. The crystallization, melting behavior and thermal stability of the hybrid composites were investigated employing differential scanning electron microscopy (DSC) and thermogravimetric analysis (TGA). Thermogravimetric analysis (TGA) showed an increase in thermal stability of the matrix polymer with incorporation of bamboo and glass fibers, confirming the effect of hybridization and efficient fiber matrix interfacial adhesion. The dynamic mechanical analysis (DMA) showed an increase in storage modulus (E′) indicating higher stiffness in case of hybrid composites as compared with untreated composites and virgin matrix. The tan δ spectra presented a strong influence of fiber content and coupling agent on the α and γ relaxation process of PP.

Cure modeling and mechanical properties of counter rotating twin screw extruder devulcanized ground rubber tire—natural rubber blends

Ground rubber tire (GRT) powder was devulcanised using a counter-rotating twin-screw extruder and the product was mixed with virgin natural rubber (NR) in various proportions. The data obtained from a cure rheometer was used to fit in a four-parameter logistic model to correlate the variation of torque with time. The mechanical properties were evaluated which suggested that tensile strength and elongation at break increased with increase in virgin natural rubber when added to the extrusion processed GRT.

Biodegradable Composites Applied to the Automotive Industry: The Development of a Loudspeaker Front

The interest of the automotive industry on biodegradable and green composites is increasing dramatically due two environmental legislation that obliges automakers to reduce the disposal of waste from vehicles [1]. As an answer to this recent demand several research groups are working on the development of these composites. This work shows the development of a loudspeaker front made of two different biodegradable composites: PLA (polylactic acid) and SCA (blend of starch and cellulose acetate) reinforced with different percentages of cellulose spent fibres. The composites were previously extruded on a counter-rotating twin screw extruder and injection moulded into tensile specimens. The mechanical properties of the produced tensile specimens were assessed with an Instron Universal Testing Machine as well as the morphological aspects of the materials, studied with optical and scanning electron microscopies. After these preliminary set of tests, the best composites were chosen to produce the final parts (loudspeaker front). These parts were injection moulded on a Ferromatik Milacron K85 injection moulding machine (850 kN clamping force) and subjected to a wide set of automotive tests to evaluate their performance. The best materials for this application proved to be the PLA reinforced composites, although there is still a large window for improvement of properties, based on the engineering of the matrix/reinforcement interface and also on the improvement of the thermal properties of the PLA material.

Experimental Studies on Screw Characteristics in Closely Intermeshing Counter-rotating Twin Screw Extruder

Abstract Experimental studies were carried out to characterize the screw pumping behavior of various screw elements for a closely intermeshing counter-rotating twin screw extruder. The pumping capacity of the screw elements was compared to earlier flow simulations by some the authors of this type of twin screw extruder.