Extrusion Step Research Articles

From Lab to Pilot Scale: Melt Electrospun Nanofibers of Polypropylene with Conductive Additives

In this paper, the feasibility of fabricating polypropylene (PP) nanofibers was investigated using conductive additives such as sodium stearate (NaSt), sodium oleate (NaOl) and Irgastat during melt electro spinning with a single nozzle lab and a 600- nozzle pilot scale device. Varying PP grades of high melt flow indices (MFI=450-1200 g/10 min) were used with different amounts of additives. The effects of the additives on the fiber diameters, thermal properties, electrical conductivity and polymer degradation were investigated. On a lab scale, fiber diameters of less than 500 nm were achieved with the compound of PP HL712FB, 4 wt% NaSt and 2 wt% Irgastat. The lab scale device was extended by a heatable spinning chamber, which affects fiber diameter reduction. The fabrication of nanofibers was in principle attributed to the increase in electrical conductivity with the introduction of the additives. On a pilot scale, the smallest fiber diameter of 6.64 μm could be achieved with PP HL508FB and 2 wt% NaSt. The comparison between the production of the fibers with a single nozzle and the pilot scale plant has revealed that a transfer of results is not possible without further ado. Due to the higher dwell time in the nozzle, a strong thermal degradation of the polymer could be detected with the high temperature size exclusion chromatography, whereby NaOl had the strongest influence on the thermal degradation. The high melt flow PP HL712FB and its compounds could not be processed with the pilot scale device due to its low viscosity, resulting in an insufficient pressure built up within the spinneret. Another reason for the non-spinnability of the material is the higher thermal and mechanical stress caused by the preceding melts preparation in an extrusion step. Further adjustments to the pilot plant are necessary to ensure a constant temperature distribution in the nozzle plate to achieve uniform fiber cross sections. The implementation of an uneven collector has successfully led to an even deposition of the fibers to obtain an isotropic non-woven fabric.

Safety assessment of the process 'RecyPET Hungária', based on RecyPET Hungária technology, used to recycle post-consumer PET into food contact materials.

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the recycling process RecyPET Hungária (EU register number RECYC0146). The input is hot caustic washed and dried poly(ethylene terephthalate) (PET) flakes originating from collected post‐consumer PET containers, containing no more than 5% of PET from non‐food applications. The flakes are dried and extruded. The output of the extrusion step is cut into pellets in an underwater chamber and then recrystallised. The crystallised pellets may then be fed into a solid‐state polycondensation (SSP) reactor. The recycled plastic is intended for manufacture of bottles for soft drinks or water. The applicant provided a challenge test, but the flakes contaminated with the surrogates and the pellets obtained after extrusion and crystallisation were extracted with n‐hexane without showing sufficient recovery. The Panel considered the extraction as unreliable and could therefore not conclude on the efficiency of the decontamination process. Furthermore, the flow charts provided by the applicant did not enable a clear identification of the steps relevant for the decontamination efficiency, and no sufficiently clear overview of the operational parameters of the steps of the process and the challenge test was provided. Without this information, a proper safety evaluation could not be performed. The Panel concluded that the process RecyPET Hungária is not sufficiently characterised and the applicant has not demonstrated in an adequately performed challenge test or by other appropriate evidence that the recycling process RecyPET Hungária is able to reduce contamination of the PET input to a concentration that does not pose a risk to human health.

Effect of contaminants and processing regime on the mechanical properties and moldability of postconsumer polyethylene terephthalate bottles

In this research, post-consumer polyethylene terephthalate (PC-PET) bottles were processed and characterized. The aim was to investigate the influence of number and type of melt processing steps and the presence of contaminants on the mechanical properties and moldability of PC-PET. Results and observations of current research showed that direct processing of PC-PET by injection molding (i.e. skipping melt extrusion step) is preferable in order not to deteriorate mechanical properties especially the toughness of PC-PET. Contaminants found in PC-PET waste stream include labels and bottle cap rings made of polyethylene (PE) and paper labels. Unlike PE contaminants, paper contaminants can drastically reduce toughness of PC-PET and severely affect its moldability. Molded samples of PC-PET containing traces of papers appeared incoherent and fragmented pieces due to poor adhesion between PET and papers. The recommendation given by current research is to remove paper contaminants from PC-PET waste stream before melt processing and melt processing steps should be limited.

A real case study of mechanical recycling as an alternative for managing of polyethylene plastic film presented in mixed municipal solid waste

This work presents an investigation on mechanical plastic recycling in order to promote the mechanical recycling rate of polyethylene plastic film presented in municipal solid waste, which had not been collected selectively, and diminish the amount of this material that is deposited in landfills. The study provides information about the main composition of the raw material, the characteristics of recycled plastic film and the effluents obtained during its recycling process that included washing (without chemicals), drying and extrusion steps. First, raw material characterization was performed that included determination of main properties of washing water obtained after its cleaning. Then, analysis of main effluents of the mechanical recycling process was carried out. Finally, ash content, relative density, thermal properties, mechanical properties, rheological properties, among others, were determined for recycled material and compared with the virgin material.

Influence of phase morphology on the rheology and thermal conductivity of HDPE/PA6 immiscible blends with alumina whiskers

The thermal conductivity (TC) of HDPE/PA6/alumina whisker composites was measured as a function of the whisker amount and HDPE/PA6 ratio and related to their composite morphology and rheological properties. The preparation of the composites, in two extrusion steps, encouraged filler localization in the HDPE phase. The addition of the whiskers produced a morphological refinement in composites with 60/40 and 50/50 HDPE/PA6 ratios, resulting in a sea-island morphology with smaller domains of polyamide (dispersed phase). For the 40/60 HDPE/PA6 ratio, a sea-island microstructure with dispersed polyethylene domains filled with alumina was observed. The best TC data was measured in composites with a 50/50 HDPE/PA6 ratio, which was associated with an increase in the effective filler amount in the host phase, in agreement with the rheological data. Induced flow at low shears produced an increase in TC, which was associated with conductive network strengthening for the 40/60 and 60/40 HDPE/PA6 ratios.

Rheological and thermorheological assessment of polyethylene in multiple extrusion process

The relationship between rheological properties and structural changes in polyethylene chains due to the recycling of two linear low-density polyethylenes (LL-A and LL-B) has been investigated. These samples were subjected to multiple extrusion processes (9 extrusion steps). According to the results of gel content experiments, crosslinking did not occur. The results of the gel permeation chromatography indicated that the chain scission was slightly predominant during the re-extrusion, while the rheometry results clearly show the effects of long-chain branching during degradation. Therefore, the degradation proceeded through both paths. Based on the rheological results and the Cole-Cole method, LL-B exhibited a higher degradation rate during the extrusion process (because of the low antioxidant content), compared to LL-A. The results of thermorheological methods including van-Gurp-Palmen and activation energy spectra indicated that the extent of thermorheological complexity was intensified with increasing the number of extrusion cycles and consequently increasing the number of long-chain branches.

Connected Process Design for Hot Working of a Creep-Resistant Mg–4Al–2Ba–2Ca Alloy (ABaX422)

With a view to design connected processing steps for the manufacturing of components, the hot working behavior of the ABaX422 alloy has been characterized for the as-cast and extruded conditions. In the as-cast condition, the alloy has a limited workability, due to the presence of a large volume of intermetallic phases at the grain boundaries, and is not suitable to process at high speeds. A connected processing step has been designed on the basis of the results of the processing map for the as-cast alloy, and this step involves the extrusion of the cast billet to obtain a 12 mm diameter rod product at a billet temperature of 390 °C and at a ram speed of 1 mm s−1. The microstructure of the extruded rod has a finer grain size, with redistributed fine particles of the intermetallic phases. The processing map of the extruded rod exhibited two new domains, and the one in the temperature range 360–420 °C and strain rate range 0.2–10 s−1 is useful for manufacturing at high speeds, while the lower temperature develops a finer grain size in the product to improve the room temperature strength and ductility. The area of the flow instability is also reduced by the extrusion step, widening the workability window.

Cellular Morphology Optimization of Polypropylene/CaCO3 Composite Films Designed for Piezoelectric Applications

In this work, the cellular morphology of polypropylene (PP)/calcium carbonate (CaCO3) composite films was optimized with respect to piezoelectric cellular films criteria. To do this, a series of PP films filled with CaCO3 micro-particles of three different particle sizes (3, 6 and 12 microns) were developed at various weight concentrations (3 to 44 wt. %). Before going through a gas diffusion expansion (GDE) step to inflate the initiated cells, all composite films were first produced via extrusion/calendaring then biaxially stretched to initiate the cellular structure by interfacial delamination between the CaCO3 particles and PP matrix. After biaxial stretching and GDE, it was observed that only films with filler contents above 23 wt.% and 12 μm particle size presented a well-developed cellular structure. By optimizing the extrusion, biaxial stretching and GDE steps, we were able to generate a required cellular morphology where the average cell height ranged between 5 and 8 μm, which is considered good for further Corona charging. Also, the average cell aspect ratio (cell length divided by cell height) ranged between 4 and 10 with an average cell wall thickness between 7 and 12 μm, which is also considered as optimum for good piezoelectric properties.

Effect of temperature in the conversion of methanol to olefins (MTO) using an extruded SAPO-34 catalyst

The methanol-to-olefin (MTO) reaction was investigated in a bench-scale, fixed-bed reactor using an extruded catalyst composed of a commercial SAPO-34 (65 weight percentage, wt-%) embedded in an amorphous SiO2 matrix (35 wt-%). The texture properties, acidity and crystal structure of the pure SAPO-34 and its extruded form (E-SAPO-34) were analyzed and the results indicated that the extrusion step did not affect the properties of the catalyst. Subsequently, E-SAPO-34 was tested in a temperature range between 300 and 500 °C, using an aqueous methanol mixture (80 wt-% water content) fed at a weight hour space velocity (WHSV) of 1.21 h‒1. At 300 °C, a low conversion was observed combined with the catalyst deactivation, which was ascribed to oligomerization and condensation reactions. The coke analysis showed the presence of diamandoid hydrocarbons, which are known to be inactive molecules in the MTO process. At higher temperatures, a quasi-steady state was reached during a 6 h reaction where the optimal temperature was identified at 450 °C, which incidentally led to the lowest coke deposition combined with the highest H/C ratio. Above 450 °C, surges of ethylene and methane were associated to a combination of H-transfer and protolytic cracking reactions. Finally, the present work underscored the convenience of the extrusion technique for testing catalysts at simulated scale-up conditions.

Simultaneous plasticization and blending of isolate soy protein with poly[(butylene succinate)‐co‐adipate] by one‐step extrusion process

ABSTRACTThis article focuses on the preparation of isolated soy protein plasticized by a glycerol and water mixture/poly[(butylene succinate)‐co‐adipate] blends by an original single step extrusion process. Prepared blends were injection‐molded and characterized for their molecular interaction, morphology, rheological, thermal, dynamic mechanical, and mechanical properties. The comparison of these results with those obtained using a more regular two‐step compounding process validates the technical efficiency of this cost‐effective one‐step approach. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46442.

Relationship between extrusion temperature and corrosion resistance of magnesium alloy AZ61

Abstract The extrusion-shear (ES) process for magnesium alloys is a newly developed plastic deformation technique, which combines one step of direct extrusion and two steps of ECAP (equal channel angular pressing). Corrosion resistances of the AZ61 magnesium alloy fabricated by ES with different billet temperatures have been investigated and evaluated through immersion and electrochemical tests. Influences of Cl- concentrations, immersion times and pH values on the corrosion behaviors of samples have been evaluated by analyzing corrosion morphologies and compositions, and phase compositions of corrosive products by using SEM and X-ray diffraction. According to the experimental results, samples processed by ES at 440 °C billet temperature have a higher corrosion resistance than those prepared at a billet temperature of 400 °C, which might be attributed to the grain-size reduction and the redistribution of inter-metallic particles within microstructures.

Influence of the dimensions of spheroniser plate protuberances on the production of pellets by extrusion-spheronisation

The influence of the dimensions of square-patterned pyramidal protuberances on a spheronisation plate on pellet yield, size and shape distributions, surface tensile strength and surface morphology was investigated using a 45wt% microcrystalline cellulose/water paste. Tests were conducted using four extrudate diameters (1.0, 1.5, 2.0 and 2.5 mm) generated by screen extrusion and seven plate geometries, including a flat plate as a control. Geometrical analyses of the protuberance shapes provide some insight into the observed differences. Sharper protuberances reduced yield (promoting breakage and attrition) but tended to give narrower size distributions and less even pellet surfaces. The pellet yield for 1 mm extrudates was also subject to losses caused by fragments passing through the 1.0 mm gap between the plate and the spheroniser wall. Pellet tensile strengths were noticeably greater for 1.0 mm diameter extrudates, which is attributed to the greater extensional strain imparted on the paste during the extrusion step. For some geometries there is an optimal ratio of extrudate to protuberance dimensions.

Effects of Extrusion-Shear and Direct Extrusion on the Plastic Deformation of AZ31 Magnesium Alloy

Based on characteristics of direct extrusion for magnesium alloy seamless tube and continuous equal channel angular pressing (ECAP) of tubes, a new composite extrusion process of tubes including direct extrusion and many steps ECAP was invented firstly, which are shorten for TES process in this paper. A three-dimensional finite element thermo-mechanical coupled model and conditions for TES process were established. The extrusion process and cumulative strains evolution during TES process were simulated. The results show that TES process can improve the cumulative strains significantly. The microstructures observations of longitudinal sections for tubes fabricated by direct extrusion and TES process were carried out. It was found that when the extrusion temperature was 400°C, and extrusion ratio was 8.4 and the channel angle was 150°, TES process can refine the microstructures of tubes effectively.

Development of Sustained Release Pellets of Galantamine HBr by Extrusion Spheronization Technique Incorporating Risk based QbD Approach

Objective: The present research aims to integrate the concept of quality by design (QbD) to develop galantamine HBr modified release pellets and to scrutinize the critical factors that can affect the quality of the pellets prepared by extrusion spheronization technique. Materials and Methods: Modified release pellets of galantamine HBr were prepared using Compritol 888 ATO and ethyl cellulose (EC) as release retardants. Avicel pH 101 was selected as an extruder aid. Before converting the wet extrudates in pellets, pregelatinized starch was sprinkled on them to improve the physical properties of the pellets. Qualitative risk analysis was performed to screen and identify the significant factors using Failure Mode Effect Analysis (FMEA) model. Central composite design was adopted to optimize the formulation. Concentration of Compritol and concentration of ethyl cellulose were selected as independent factors and drug release at 2, 6, and 10 h were selected as dependent variables. The pellets were evaluated for size, shape, flow, % yield, % friability and drug content. Results and Discussion: Concentration of Compritol and concentration of EC were found to be critical factors from FMEA model. All the batches of central composite design showed excellent flowability, spherical shape, desired size, yield, friability and drug content. Multiple linear regression analysis and analysis of variance were performed to identify the effect of independent variables on different responses. Design space was generated from the data. In vivo plasma concentration time profile was predicted from in vitro data. Conclusion: Concentration of Compritol and EC were found to be significant for the development of modified release pellets. Innovative finding of the present research is to explore the potential use of pregelatinized starch as a dry binder in the post wet extrusion step.

Contact mechanics of isotactic polypropylene: Effect of pre-stretch on the frictional response

Polymers are increasingly used in applications where relative moving parts are in contact. The dissipation of energy due to friction, i.e. heat production, reduces a product's lifetime significantly. Since in processing often an extrusion or injection moulding step is used in product formation, the induced anisotropic microstructure leads to a spatial variation of mechanical properties, for example frictional resistance. In this work we compare the scratch response of isotropic isotactic polypropylene (iPP) to the response of various oriented iPP systems. Subjected to single-asperity contact with a rigid diamond, the surface penetration and lateral force are measured. For various combinations of applied normal load and sliding velocity, the surface penetration and lateral force are measured. Optical profilometry measurements are used to explain the (large) differences in residual scratch profile between tests performed in the direction parallel and transverse to the orientation direction, respectively. As the anisotropy increases with the amount of orientation, both the maximum tensile stress and the strain hardening increase substantially. The penetration depth, for oriented systems governed by the transverse viscoelasticity and yield stress, is comparable for all loading angles and decreases with increasing amount of orientation. The direction of lowest frictional resistance is shown to be the direction parallel to the oriented crystals. The combination of decreasing global deformation and friction reduction as a result of pre-stretch decelerates strain localization, therewith delaying crack initiation which eventually leads to abrasive wear. Along with that, the substantial amount of elastic recovery after scratching in the transverse direction is related to the pre-tension of the perpendicular crystal network.

Novel bio-nanocomposite hybrids made from polylactide/nanoclay nanocomposites and short flax fibers

This article aims to formulations and properties of novel hybrid biomaterials containing unique four-phase combinations of polylactide (PLA), nanoclays, flax fibers, and coupling agents. A PLA-grafted maleic anhydride (PLA- g-MA) masterbatch containing 10 wt% PLA- g-MA was obtained by reactive extrusion and was further used, after dilution, as a coupling agent. In addition, three PLA masterbatches containing 10 wt% of three different grades of nanoclays, one untreated nanoclay and two organonanoclays, were also compounded. In a subsequent extrusion step, the nanoclay masterbatches were diluted in PLA down to 4 and 2 wt% while simultaneously incorporating in each one 20 wt% of short flax fibers. Those bio-nanocomposites were compounded without and with an equivalent content of PLA- g-MA, that is, with 4 and 2 wt%, respectively, through the dilution of 10 wt% PLA- g-MA masterbatch. The effects of the nanoclay chemistries, PLA- g-MA, and of flax fibers presence on the properties of bio-nanocomposite hybrid materials were investigated. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, rheology, mechanical properties (tension, flexural, and Izod impact), and reprocess ability tests were used to characterize the bio-nanocomposite hybrid materials. In a second step, PLA- g-MA was replaced by an epoxy/styrene/acrylic copolymer for comparison purpose of their respective effect in bio-nanocomposite performances. Mechanical properties of bio-nanocomposites containing the second coupling agent were also evaluated. The effect of the epoxy/styrene/acrylic copolymer is discussed in comparison with the effect of PLA- g-MA.

Safety assessment of the process 'Krones' used to recycle post-consumer PET into food contact materials.

This scientific opinion of the EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids deals with the safety assessment of the recycling process Krones pellet (EU register number RECYC0149). The input to the process is washed and dried poly(ethylene terephthalate) (PET) flakes originating from collected post‐consumer PET containers and containing no more than 5% PET from non‐food consumer applications. In this technology, washed and dried PET flakes are extruded to pellets that are then crystallised and decontaminated in a reactor at high temperature under vacuum. Having examined the results of the challenge test provided, the Panel concluded that two steps, the extrusion (step 2) and the decontamination in the vacuum reactor (step 4), are the critical steps that determine the decontamination efficiency of the process. The operating parameters to control the performance of these critical steps are temperature, residence time and, for the vacuum reactor, also pressure. Under these conditions, it was demonstrated that the recycling process is able to ensure that the level of migration of potential unknown contaminants into food is below the conservatively modelled migration of 0.1 μg/kg food. Therefore, the Panel concluded that the recycled PET obtained from this process when used up to 100% for the manufacture of materials and articles for contact with all types of foodstuffs for long‐term storage at room temperature, with or without hotfill, is not considered of safety concern. Trays made of this recycled PET should not be used in microwave and conventional ovens.

Aligning cellulose nanofibril dispersions for tougher fibers

Nanocomposite materials made from cellulose show a great potential as future high-performance and sustainable materials. We show how high aspect ratio cellulose nanofibrils can be efficiently aligned in extrusion to fibers, leading to increased modulus of toughness (area under the stress-strain curve), Young’s modulus, and yield strength by increasing the extrusion capillary length, decreasing its diameter, and increasing the flow rate. The materials showed significant property combinations, manifesting as high modulus of toughness (~28–31 MJ/m3) vs. high stiffness (~19–20 GPa), and vs. high yield strength (~130–150 MPa). Wide angle X-ray scattering confirmed that the enhanced mechanical properties directly correlated with increased alignment. The achieved moduli of toughness are approximately double or more when compared to values reported in the literature for corresponding strength and stiffness. Our results highlight a possibly general pathway that can be integrated to gel-spinning process, suggesting the hypothesis that that high stiffness, strength and toughness can be achieved simultaneously, if the alignment is induced while the CNF are in the free-flowing state during the extrusion step by shear at relatively low concentration and in pure water, after which they can be coagulated.

Hydrogen Bond Directed Photocatalytic Hydrodefluorination: Overcoming Electronic Control.

The photocatalytic C-F functionalization of highly fluorinated arenes is a powerful method for accessing functionalized multifluorinated arenes. The decisive step in the determining regioselectivity in fluorine functionalization is fluoride fragmentation from the radical anion of the multifluorinated arene. To date, the availability of regioisomers has been dictated by the innate electronics of the fluorinated arene, limiting the synthetic utility of the chemistry. This study investigates the remarkable ability of a strategically located hydrogen bond to transcend the normal regioselectivity of the C-F functionalization event. A significant rate acceleration is additionally observed for hydrodefluorination of fluorines that can undergo intramolecular hydrogen bonds that form 5-8-membered cycles with moderately acidic N-H's. The hydrogen bond is expected to facilitate the fragmentation not only by bending the C-F bond of the radical anion out of planarity but also by increasing the exothermicity of the fluoride extrusion step through protonation of the naked fluoride. Finally, the synthetic utility of the method is demonstrated in an expedited synthesis of the trifluorinated α-phenyl acetic acid derivative required for the commercial synthesis of Januvia, an antidiabetic drug. This represents the first synthesis of a commercially important multifluorinated arene via a defluorination strategy and is significantly shorter than the current strategy.

Palladium‐Catalyzed Deformylation Reactions with Detailed Experimental and in Silico Mechanistic Studies

A facile, efficient, and general deformylation reaction with a wide‐ranging functional group compatibility has been developed with palladium acetate as a precatalyst under exogenous ligand‐free conditions. The mechanistic details of the palladium‐catalyzed deformylation reaction have been outlined on the basis of a combination of experimental and computational studies. The heterogeneous pathway is predominant for the deformylation, and homogeneous catalysis occurs to a lesser extent. This ligand‐free catalytic cycle is proposed to undergo oxidative addition, migratory extrusion, and reductive elimination as the key steps. Kinetic studies reveal a first‐order rate dependency with respect to the aldehyde. Furthermore, kinetic isotope effects, competition experiments, and Hammett studies suggest that the migratory extrusion step is the rate‐determining step. For the homogeneous pathway, the experimental findings are also supported by DFT studies.