Co-rotating Twin Screw Extruder Research Articles

Poly(Vinyl Alcohol) Fiber Reinforced High Density Poly(Ethylene) Composites: Melting and Crystallization Behavior

In the present study, high density poly(ethylene) (HDPE)/poly(vinyl alcohol) (PVA) fiber composites were prepared via melt blending technique using a co-rotating twin screw extruder (TSE). The effect of four different PVA fiber concentrations (i.e. 0, 5, 10, 20 wt%) on the melt and crystallization behavior of the HDPE/PVA fiber composites were investigated. The surface morphology of the composites was analyzed by a scanning electron microscopy (SEM). Whereas, the melt and crystallization behavior of the composites were analyzed by a differential scanning calorimetry (DSC). The SEM analysis on the cryo-fractured surface of the HDPE/PVA fiber composites exhibited that the PVA fibers were well blended/distributed in the HDPE matrix. Additionally, the DSC test results showed that the addition of PVA fiber in the HDPE matrix did not significantly change the melting peak temperature (Tm) of the composites. Furthermore, a slight decrease of the crystallization peak temperature (Tc) can be observed when the PVA fiber was incorporated in the HDPE matrix, which indicated a weak nucleation ability of the PVA fibers in the HDPE crystallization process. The same trend was also observed for the crystallinity index (Xc). The crystallinity index of the composites decreased with increasing PVA fiber loadings.

Microstructural, thermal and rheological correlations to mechanical response of polyamide-6(glass filled)/polyetherimide blend: effect of ethylene-octene copolymer on toughening of blend

Melt mixed glass-filled polyamide 6(PA6)/polyetherimide (PEI) blends were prepared in a co-rotating twin screw extruder over the entire composition range of 0–100 wt% of polyamide 6. These blends were characterized by structural, rheological, mechanical and thermal properties. Crystallization behavior and phase morphology of the blends were also investigated. The blend with the composition PA6/PEI 75/25 showed overall improved mechanical properties along with low resultant viscosity which can be processed on standard equipment. Shear viscosity along with shear stress of the blends were analyzed using shear rheometer which concluded that the blends can be processed on standard equipment due to resultant low viscosity. Scanning electron microscope micrographs revealed that the morphology of the blends showed a two phase structure in which the minor phase was dispersed as domains in the continuous phase. Polyolefin elastomer (POE) as impact modifier was added to the above composition in the range of 0–15 phr to study its effect. The thermal characteristics of PA6, PEI, and PA6/PEI blends with and without POE were investigated using DSC and TGA which revealed that the melting temperature and crystallization temperature of the blend remained unchanged while XRD results showed percent crystallinity was increased slightly. Furthermore, it can be said that the blend with composition PA6/PEI 75/25 with 10 phr impact modifier loading was suitable for high end applications because it combines the high mechanical properties of glass-filled PA6 with inherent flame-retardant property of PEI while POE overcomes the physical weakness of moisture absorption.

Assessment of Compatibility in Polypropylene/Poly(lactic acid)/Ethylene Vinyl Alcohol Ternary Blends: Relating Experiments and Molecular Dynamics Simulation Results

ABSTRACTTwo systems of polypropylene (PP), poly(lactic acid) (PLA) and ethylene vinyl alcohol copolymer (EVOH) ternary blends having different compositions were extruded in a co-rotating twin screw extruder. The first system was PP/PLA (75/25) with various EVOH contents, the second one was PP/EVOH (75/25) having various PLA contents. The effects of composition on the morphology and the tensile and impact properties of the blends were investigated. There were increases in the tensile modulus and tensile strength with an increase in the EVOH and PLA contents in the first and second systems, respectively. A molecular dynamics (MD) simulation was used to investigate the compatibility between the components. Prediction of the miscibility of the blends was carried out by determining the interaction parameters (χ), mixing energies (ΔHmix), phase diagrams and Gibbs free energies. The MD simulation showed a UCST behavior for the components. Moreover, the simulation results showed a compatibilizer effect for the EVOH component. The experimental values of the dynamic mechanical thermal analysis (DMTA) and mechanical properties were correlated to the MD results. There was a good correlation between the MD and DMTA results. The modulus values using the parallel and Davis models were near to the experimental ones. A good fitting to the mixture law with addition of EVOH confirmed a good compatibilzing effect of it between the PP and PLA components.

Automatic Optimization of Screw Configuration of an Intermeshing Co-rotating Twin Screw Extruder using Artificial Intelligence Algorithm

Automatic Optimization of Screw Configuration of an Intermeshing Co-rotating Twin Screw Extruder using Artificial Intelligence Algorithm

Cross-Linked Hydrophobic Starch Granules in Blends with PLA

Abstract The majority of native starch is used in the food sector and in the paper industry. Only a small amount is used in polymer engineering. One reason for the reluctance of the plastics processing industry to use starch as a filling material in polymer blends is the unsatisfactory mechanical behavior of starch when combined with thermoplastics. Another reason is the hydrophilicity of starch. In order to make these materials capable of competing, an amelioration of the mechanical properties is compulsory. By means of modifying the native starch and optimizing the compounding process, it is possible to improve the performance of starch blends, and, thus, increase the number of application areas of these materials. For this reason, native starch was modified with a cross-linking agent using a laboratory mixer. Subsequently, the modified starch and poly(lactic acid) were compounded using a co-rotating twin screw extruder. Cross-linking of the native starch in the laboratory mixer resulted in an increase in the mechanical strength of the starch blends. In addition, the blends with cross-linked starch displayed lower moisture absorption levels than blends with native starch as a filling material.

Recycling of resin cured IIR-based ground bladder rubber with the assistance of subcritical fluids

In this work, the devulcanization reaction of isobutylene–isoprene rubber (IIR)-based ground bladder rubber (GBR) in GBR/ethylene–propylene–diene monomer (EPDM) blend was investigated through a co-rotating twin-screw extruder. The influences of subcritical fluids (blank sample, water, ethanol, and n-propanol) and temperatures (160°C, 180°C, and 200°C) were investigated. The results confirmed the effectiveness of subcritical fluids in decreasing the gel content. Moreover, gel permeation chromatography analysis demonstrates that the devulcanizing processes with subcritical fluids are more homogeneous, making the molecular weight of sol detached from the devulcanized blend more uniform. Proton nuclear magnetic resonance spectra confirm that the reactivity of devulcanization of subcritical ethanol was the best. The optimal extrusion temperature for devulcanization is 180°C, at which the mechanical properties of the revulcanized IIR/(devulcanized ground bladder rubber [DGBR]/EPDM) blends achieve the best state. When promoting agent alkylphenol polysulfide (450) works with the assistance of subcritical ethanol at the best reaction condition (180°C, 2.0 MPa, and 500 r min−1), the tensile strength and elongation at break of the revulcanizate retain 94.7% and 110.2% of vulcanized IIR (15.91 MPa, 483.62%), respectively.

Some effects of radiation treatment of biodegradable PCL/PLA blends

Abstract Changes in melt flow rate (MFR), mechanical properties, and morphology occurring upon the electron beam (EB) irradiation of polycaprolactone/polylactide (PCL/PLA) blends were discussed. Reference samples and examined blends were prepared using co-rotating twin screw extruder. The obtained materials were irradiated with high-energy EB. The applied radiation dose was 40 kGy. Studies have shown that EB irradiation affected the properties of PCL/PLA blends in different ways. In the case of pure PLA and blends with a significant content of PLA the degradation process mainly occurred, whereas in pure PCL and blends with a significant content of PCL the degradation process was almost absent. Moreover, it was found that properties of PCL/PLA blends depended mainly on the content of PLA phase that was more susceptible to electron radiation than the PCL one.

Effects of Compatibilizer and Thermoplastic Starch (TPS) Concentration on Morphological, Rheological, Tensile, Thermal and Moisture Sorption Properties of Plasticized Polylactic Acid/TPS Blends

The blends of polylactic acid plasticized with acetyl tributyl citrate (P-PLA) and thermoplastic wheat starch (TPS) were prepared by a co-rotating twin screw extruder and the effect of maleic anhydride grafted PLA (PLA-g-MA) content as reactive compatibilizer on blends compatibility through morphological, rheological and tensile properties of the blends was investigated. Considerable improvement in properties of P-PLA/TPS (70/30 w/w) blend with incorporating the optimum PLA-g-MA content of 4 phr was achieved as this blend exhibited better morphological and rheological properties with an increase by 158 and 276% in tensile strength and elongation at break, respectively, compared to the uncompatibilized blend. Also the thermal stability and moisture sorption properties of the blends as effected by TPS content were studied. Decreasing in thermal stability and increasing in equilibrium moisture content of the blends were observed with progressively increasing of TPS content. For prediction the moisture sorption behaviour of blends with various TPS contents at different relative humidity, the moisture sorption isotherm data were modeled by GAB (Guggenheim–Anderson–de Boer) model.

Effect of SEBS-g-MAH addition on the mechanical, rheological, and morphological properties of polycarbonate/acrylonitrile–butadiene–styrene blends

In this research, the effect of maleic anhydride–grafted styrene–ethylene/butylene–styrene (SEBS-g-MAH) compatibilizer on different properties of polycarbonate and poly(acrylonitrile–butadiene–styrene) (PC/ABS) blends was investigated. For this purpose, blends of PC and ABS at different ratios, without and with varying concentrations of compatibilizer, were prepared by melt compounding in a co-rotating twin-screw extruder followed by injection molding. The effectiveness of the compatibilizer was investigated by studying the microstructure and the mechanical, thermal, and rheological properties of the blends. It was found that the addition of the compatibilizer increases tensile strength, modulus, elongation at break, impact strength, complex viscosity, and thermal stability. This effect was noted at a loading of 1 wt% of compatibilizer, where enhanced interactions between the PC and ABS can be seen. Rheological methods, based on dynamic viscoelastic tests, allowed us to distinguish between emulsion-like and co-continuous morphologies and allowed an insight into the effect of the compatibilizer on the interfacial tension.

Toughening of Wood-plastic Composites Based on Silane/Peroxide Macro Crosslink Poly(propylene) Systems

The toughening of wood-plastic composites (WPC) based on silane/ peroxide macro crosslink poly(propylene) (PP) systems was studied. A 23 experimental design was adopted to initially optimize three parameters: silane, wood flour, and talc contents of the WPC formulation. The WPCs were manufactured on a co-rotation twin screw extruder. Test specimens were prepared via injection molding. The WPC compounding formula with 8 phr of silane, 35 phr of wood flour, and 20 phr of talc was used to study the effect of ultra-high molecular weight polyethylene (UHMWPE) as a toughener. The impact strength was improved up to a 10-phr UHMWPE loading. The flexural properties and heat distortion temperature (HDT) slightly decreased. When exceeding 10 phr of UHMWPE, the unmelted UHMWPE agglomerated and the mechanical properties were inferior. The fiber/matrix interfacial adhesion was enhanced by the sauna treatment. A marginal increase in the fracture toughness was observed. The impact strengths increased with the addition of ethylene propylene diene terpolymer (EPDM) as a rubber toughener. However, high EPDM contents caused a decrease in the HDT. The sauna incubation of the EPDM-toughened WPC enhanced the impact strengths. The EPDM effectiveness was determined by the better PP matrix toughness and UHMWPE/PP interfacial adhesion.

Inline UV/Vis spectroscopy as PAT tool for hot-melt extrusion.

Hot-melt extrusion on co-rotating twin screw extruders is a focused technology for the production of pharmaceuticals in the context of Quality by Design. Since it is a continuous process, the potential for minimizing product quality fluctuation is enhanced. A typical application of hot-melt extrusion is the production of solid dispersions, where an active pharmaceutical ingredient (API) is distributed within a polymer matrix carrier. For this dosage form, the product quality is related amongst others to the drug content. This can be monitored on- or inline as critical quality attribute by a process analytical technology (PAT) in order to meet the specific requirements of Quality by Design. In this study, an inline UV/Vis spectrometer from ColVisTec was implemented in an early development twin screw extruder and the performance tested in accordance to the ICH Q2 guideline. Therefore, two API (carbamazepine and theophylline) and one polymer matrix (copovidone) were considered with the main focus on the quantification of the drug load. The obtained results revealed the suitability of the implemented PAT tool to quantify the drug load in a typical range for pharmaceutical applications. The effort for data evaluation was minimal due to univariate data analysis, and in combination with a measurement frequency of 1Hz, the system is sufficient for real-time data acquisition.

Studies on the effect of compatibilizers on mechanical, thermal and flow properties of polycarbonate/poly (butylene terephthalate) blends

Bisphenol-A polycarbonate (PC) and poly(butylene terephthalate) (PBT) were melt blended with ethylene-n-butylacrylate-glycidylmethacrylate terpolymer (E-BA-GMA) at various proportions in order to study the effects of compatibilizers on mechanical, thermal and flow properties of blends. Furthermore, on the basis of this study, PC and PBT were melt-blended at 60/40 proportion with three different compatibilizers viz., ethylene-n-butylacrylate copolymer (E-BA), E-BA-GMA and random copolymer of ethylene and glycidylmethacrylate (E-GMA) at 3 phr loading in a co-rotating twin screw extruder. Tensile, flexural and impact tests were carried out on injection molded samples of PC/PBT blends. The notched izod impact strength increases enormously (∼2–3 times) on addition of any one of the three compatibilizers, and elongation at break (%) also improves tremendously (3, 5 and 4 times) on incorporation of E-BA, E-BA-GMA and E-GMA copolymer, respectively while other mechanical properties decreases slightly (3%–8%) on addition of any one of these compatibilizers. The heat deflection temperature (HDT) raises ∼8 °C–9 °C on addition of either E-BA-GMA or E-GMA, while E-BA shows a negative effect on HDT. The melt flow index diminishes significantly (∼5%–20%) on incorporation of these compatibilizers. The morphology studies via scanning electron microscopy of these four blends were carried out to confirm the mechanical results.

Effects of extrusion conditions on the physicochemical properties of soy protein/gluten composite

Soybean protein-gluten blend was extruded using a co-rotating twin-screw extruder. Effects of different extrusion conditions on the textural properties of extrudates were analyzed by central composite design through the evaluation of texturization index, water holding capacity, and hardness of extruded protein products. Extrusion process variables including feed moisture content (40%-60%), screw speed (12-20 Hz), extrusion temperature (120°C-180°C), and gluten content (16%-32%) were studied by the nonlinear regression equations analysis. The extrusion process was also optimized using response surface methodology (RSM). The influence of moisture content on the hardness of extrudate was the most significant. The optimized results, including feed moisture content, extrusion temperature, screw speed and gluten content were 49.18%-50.15%, 155.24°C-159.86°C, 16.41-16.73 Hz, 20.00%-20.03%, respectively. The microstructures of TISP products were analyzed by scanning electron microscopy (SEM) and the changes of protein molecules before and after extrusion were also analyzed by SDS-PAGE electrophoresis. Keywords: soybean protein, gluten, extrusion, response surface methodology (RSM), SDS-PAGE electrophoresis, Microstructural properties DOI: 10.25165/j.ijabe.20181104.4162 Citation: Wu M, Sun Y, Bi C H, Ji F, Li B R, Xing J J. Effects of extrusion conditions on the physicochemical properties of soy protein/gluten composite. Int J Agric & Biol Eng, 2018; 11(4): 230-237.

Influence of extruder screws speed and process temperature on the extrudate shape changes of the maize-spelt blends

The objective of the study was examination of changes in the shape factors of extruded products, which occur as a result of different settings of the extrusion process variables. Samples analysed included products created by means of the extrusion process from a mixture of spelt flour and cornmeal, with the share of spelt at 70 to 100%. The samples were made with the use of a co-rotating twin screw extruder. Two speeds of extruder screw rotation (300 and 350 rpm) as well as two levels of temperature (120 and 140°C) were set during the investigation. The samples obtained were photographed in a light box, following which they underwent an image analysis with the use of specialist vision software. Four shape-related factors were determined: area, elongation factor, Heywood circularity factor and compactness factor. It was determined that the product shape changed significantly depending on the share of spelt flour in the mixture. Moreover, it was observed that change in the screw rotation speed within the analysed range may cause material changes in the shape of particular extrudates.

Simulation of Epoxy/Cloisite-15A Multifunctional Nanocomposites using Twin Screw Extruders

Simulation of material flow through kneading elements with different staggering angles for the processing of polymer nanocomposites is an emerging area of research. This research presents simulation of epoxy/Cloisite-15A nanocomposite processing in intermesh co-rotating twin screw extruder using Solidworks. Staggering angles of 15°, 30°, 45°, 60° and 90° and disc thickness (3 mm and 6 mm) were considered for the configuration of kneading elements for the simulation. Material flow rate of 1 kg/s was maintained constant for all the configurations with 2 % intensity of turbulence. Boundary conditions were applied at the inlet and front and rear sides of the screw. Staggering angle of 60° and disc thickness of 6 mm corresponded to high pressure and velocity. Uniform particle distribution and high shear rate were obtained in case of 60° staggering angle and 3 mm disc thickness.

MODIFIED POLYLACTIDE FILAMENTS FOR 3D PRINTING WITH IMPROVED MECHANICAL PROPERTIES

We investigated the effects of two different types of impact modifiers, i.e. core-shell rubber and aliphatic polyester, on the mechanical and thermal properties of polylactide (PLA) filaments for 3D printing. First, PLA/impact modifier blends with various concentrations of impact modifiers were prepared by melt blending in a co-rotating twin screw extruder and test specimens by injection molding. The mechanical and thermal properties of blends were investigated by tensile and bending tests, dynamic mechanical analysis (DMA) and Charpy impact test. It was found that core-shell rubber remarkably improved Charpy impact strength at loadings above 5 wt % (up to 746 %). As shown by DMA, the PLA/10 wt % core-shell rubber blend exhibited better damping performance as compared to neat PLA over the whole examined frequency range, especially at high frequencies, which explained the increase in impact strength. The filament for a fused deposition modeling (FDM), 3D printer was prepared from blend with the highest impact strength (PLA/10 wt % core-shell rubber), whereas PLA and acrylonitrile-butadiene-styrene copolymer (ABS) filaments were used for reference. Test specimens were prepared by using a consumer FDM 3D printer. The mechanical and thermal properties were investigated by tensile and bending tests, DMA, Charpy impact test, and ultra-fast differential scanning calorimetry (Flash DSC). Specimens from PLA blend exhibited 109 % increase in Charpy impact strength as compared to neat PLA. In contrast to injection molded specimens, 3D printed PLA blend exhibited higher tensile E modulus than neat PLA, which was ascribed to improved interlayer adhesion. Moreover, DMA and Flash DSC analysis of 3D printed specimens showed an increase in the glass transition temperature as compared to injection molded specimens. This phenomenon was ascribed to reduction of free volume because of slow cooling in 3D printing process, which is also the reason for increased tensile E modulus of the PLA blend. All tested PLA, PLA blend and ABS filaments were in amorphous state as shown by Flash DSC analysis. Bending test showed an increased toughness of PLA blend in comparison to neat PLA and also higher toughness as compared to ABS. The modified polylactide (PLA/10 wt % core-shell rubber) filament thus combines easy processability of PLA filament and impact toughness of ABS filament.

Effects of micro particle reinforcement on mechanical properties of 3D printed parts

PurposeThe purpose of this paper is to characterize the effects of different micro particle reinforcement with same weight ratio in acrylonitrile-butadiene-styrene (ABS) feed-stocks for 3D printing process.Design/methodology/approachIn this study, composite filaments were produced by using a co-rotational twin screw extruder and used as building material to print samples in a commercial fused deposition modeling (FDM) 3D printer. The reinforcement particles, ZrB2 and Al, have different properties, including density, surface area, purity and particle morphology, and were expected to improve mechanical properties of 3D printed samples. Differential calorimetry scanning and melt flow index studies were applied on the materials to observe the change in glass transition temperatures and melt flow behaviors, respectively. Also, to evaluate the mechanical properties, tensile and three-point bending test were carried out. Fractured surfaces were characterized via energy-dispersive X-ray spectroscopy for validation of the reinforcements in the ABS matrix. Moreover, scanning electron microscope micrograph examination was conducted on the fractured surfaces to characterize fracture modes.FindingsFor 3D printed samples, a strain increase of at least 82.5 per cent was achieved by using micro particle reinforcement with a weight ratio of 1.5 per cent.Research limitations/implicationsHigher filler ratios of the reinforcement particles cause loss on the printability of the feed-stocks.Practical implicationsReinforced ABS stands out as a possible solution to overcome robustness problems in FDM printing.Originality/valueEven though the effects of printing parameters on the mechanical properties of 3D printed parts have been vastly studied in the literature, studies conducted on improvement of the building materials are limited. This paper proposes to create novel feed-stock materials for achieving printed parts with superior properties using polymer composites.

Development of Dispersion during Compounding and Extrusion of Polypropylene/Graphite Nanoplates Composites

Abstract Carbon-based nanoparticles have unique electrical, thermal, barrier and mechanical properties. When incorporated into polymer matrices, the resulting nanocomposites are potentially suitable for a wide scope of advanced applications. In practice, the properties of the nanocomposites are strongly determined by the level of dispersion achieved and by the degree of polymer/particle interfacial bonding. Production and processing of nanocomposites are often carried out in successive thermo-mechanical cycles. These may change the state of nanoparticle dispersion. This work analyzes the evolution of the dispersion of graphite nanoplates (GnP) in a polypropylene matrix during compounding in a co-rotating twin screw extruder and subsequent processing in a single screw extruder, aiming at a better understanding of the kinetics and stability of dispersion. Dispersion was evaluated along the compounding and processing stages and correlated with the composite electrical conductivity, an important engineering property. Two commercial GnP were used as received and chemically modified to graft PP-g-MA (fGnP-PP). Compositions with 2 or 10 wt.% of GnP and fGnP-PP were studied.

Fabrication of Admicelled Natural Rubber by Polycaprolactone for Toughening Poly(lactic acid)

Natural rubber (NR) with polycaprolactone (PCL) core–shell (NR-ad-PCL), synthesized by admicellar polymerization, was acted as an impact modifier for poly(lactic acid) (PLA). PLA and NR-ad-PCL were melt-blended using a co-rotating twin screw extruder. The morphology of PLA/NR-ad-PCL blends showed good adhesion as smooth boundary around rubber particles and PLA matrix. Only 5 wt% of rubber phase, NR-ad-PCL was more effective than NR to enhance toughness and mechanical properties of PLA. The contents of the NR-ad-PCL were varied from 5, 10, 15 and 20 wt%. From thermal results, the incorporation of the NR-ad-PCL decreased the glass transition temperature and slightly increased degree of crystallinity of PLA. Mechanical properties of the PLA/NR-ad-PCL blends were investigated by dynamic mechanical analyser, pendulum impact tester and universal testing machine for tension and flexural properties. The increasing NR-ad-PCL contents led to decreasing Young’s and storage moduli but increasing loss modulus. Impact strength and elongation at break of the PLA/NR-ad-PCL blends increased with increasing NR-ad-PCL content up to 15 wt% where the maximum impact strength was about three times higher than that of pure PLA and the elongation at break increased to 79%.

INFLUENCES OF PROCESS VARIABLES AND SUBCRITICAL FLUIDS ON EPDM-ASSISTED DEVULCANIZATION OF SBR-BASED GROUND TIRE RUBBER

ABSTRACT The devulcanization reaction of SBR-based ground tire rubber (GTR) in GTR/EPDM blend was investigated through a co-rotating twin-screw extruder by increasing the screw rotation speed in the presence of subcritical fluids (water, ethanol, and propanol). The influences of the screw rotation speed, the promoting agents, and temperature were investigated. The results show that subcritical fluid, which is a swelling agent and reaction medium, promotes the devulcanization reaction, increases the selectivity of crosslink breakage, keeps the extrusion material from oxidative degradation, reduces the gel particle size of the devulcanized blends, and significantly improves the mechanical properties of the revulcanizate. Among different subcritical fluids (water, ethanol, propanol), the influence of subcritical ethanol is significantly obvious. When promoting agent 450 is added under the best reaction conditions (ethanol, 200 °C, 2.2 Mpa, and 600 rpm), the tensile strength and elongation at break of the revulcanizate retains 99.6% and 209% of vulcanized SBR (24.0 MPa, 356%), respectively.