Co-rotating Twin Screw Extruder Research Articles

Cysteine, sodium metabisulfite, and glutathione enhance crosslinking between proteins during high moisture meat analog extrusion processing and may improve the fibrousness of the products.

High moisture meat analog (HMMA) products processed using extrusion have become increasingly popular in the last few years. Because the formation of disulfide bonds is believed to play a critical role in the texturization mechanism, this study aimed to understand how chemical compounds capable of reducing disulfide bonds, specifically cysteine, sodium metabisulfite, and glutathione, affect the texture and the chemical interactions between the proteins. Wheat protein blended with cysteine, sodium metabisulfite, or glutathione at levels of 0, 0.5, 1.0, 2.5, 5.0, and 7.5 g kg-1 was extruded at three different temperatures (115, 140, and 165 °C) using a co-rotating twin-screw extruder. The feed rate (85 g min-1), the moisture content (600 g kg-1), and the screw speed (300 rpm) were kept constant. Unextruded and extruded material was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, polymeric protein fractionation, and sulfhydryl group/disulfide bond analysis. Extruded samples were further analyzed for their hardness and their anisotropic index. The inclusion of reductants significantly affected the structure of the obtained extrudates. Although reducing agents had a relatively small impact on the total amount of disulfide bonds, their action significantly enhanced crosslinking between the proteins. At select conditions, samples with high fibrousness were specifically obtained when cysteine or sodium metabisulfite was included at levels of 5.0 g kg-1. In the presence of reducing agents, it is believed that disulfide bonds are split earlier during the process without binding to them, giving the protein strands more time to unravel and align, leading to a better flow behavior and more fibrous products. © 2024 Society of Chemical Industry.

Modelling supercritical CO2 flow in a co-rotating twin screw extruder using the level-set method

Supercritical CO2 has been used in recent years to replace conventional blowing agents in extrusion processes. So far, computational fluid dynamics analyses of such extrusion processes are relatively scarce. In this work, a multiphase model of a co-rotating twin screw extruder is presented that uses the level-set method to describe the interface between supercritical CO2 and polypropylene - which is modelled as an inelastic, non-Newtonian fluid - under various operating conditions. The results show that the level-set method is a promising technique to describe multiphase flow and can predict both stable and unstable processing regimes as described by experimentalists in literature.

Effect of Coupling Agent on the Properties of Pineapple Leaf Fiber/ Polypropylene Composite

Natural fibre matrix composites have been utilized in numerous industries, including the automotive, construction, and aerospace sectors. Maleic anhydride grafted polypropylene (MAPP) was used in this study to examine the effect of the coupling agent on the properties of a composite-produced using pineapple leaf fibre. The weight ratios of pineapple leaf fibre, polypropylene, and MAPP were 20g:180g, 15g:180g:5g, and 10g:180g:10g, respectively. The materials were mixed using a co-rotating twin-screw extruder machine at 170 °C and 50 rpm. The composite was then manufactured by injection molding at 185 °C. The mechanical and physical properties of PALF composite were examined by using a tensile test, impact test, and water absorption test. Thermal Gravimetric Analysis (TGA) was used to characterize the thermal properties of PALF/PP, and PALF/PP/MAPP composite. The surface morphology and fracture surface of the composite was characterized by using Scanning Electron Microscopy (SEM). Compared to the composite containing 5 g of MAPP, the tensile strength composite containing 10 g of MAPP produced a stronger interfacial bond. According to the impact test, adding more MAPP increases the material's strength and stress transmission. The average percentage of water absorption indicates low water absorption after the addition of the coupling agent. It can be concluded that the addition of a coupling agent improved the composite's properties.

Influence of γ-Irradiation on the Electronic Structure and the Chemical and Mechanical Properties of Poly(hydroxybutyrate-valerate)/Poly(caprolactone) Blends: Insights from Experimental Data and Computational Approaches

In this study, we investigated the influence of γ-irradiation (0, 50, and 100 kGy) doses on the chemical and mechanical properties of biodegradable poly(hydroxybutyrate-valerate)/poly(caprolactone) (PHBV/PCL) polymer blends rich in low-molar-mass PCL, which were prepared using a co-rotating twin-screw extruder. In parallel, the density functional theory (DFT) and the time-dependent DFT (TD-DFT) methods were used together with a model containing four monomer units to provide an insight into the electronic structure, chemical bonds, and spectroscopic (such as Nuclear Magnetic Resonance (NMR) and Ultraviolet-visible (UV-vis)) properties of PHBV and PCL blend phases, which are critical for predicting and designing new materials with desired properties. We found that an increase in γ-irradiation doses caused splitting instead of crosslinks in the polymer chains, which led to evident deformation and an increase in tensile strength at break of 2.0 to 5.7 MPa for the PHBV/PCL blend. Further, this led to a decrease in crystallinity and proved the occurrence of a more favorable interaction between the blend phases.

Reactive processing-microstructure-mechanical performance correlations in biodegradable poly(lactic acid)/expanded graphite nanocomposites.

Reactive extrusion is a promising method to prepare biodegradable nanocomposites with enhanced modulus, strength and toughness. In this study, biodegradable extended nanocomposites based on poly(lactic acid) (PLA)/expanded graphite (EG) were prepared by melt-compounding using a co-rotating twin-screw extruder. Effects of EG loading, aspect ratio, delamination and dispersion state on the mechanical and thermo-mechanical properties of PLA/EG nanocomposites were investigated. Adding the largest EG (EGL) nanoplatelets, having the average particle size of 48.2 μm and aspect ratio of 19.5, to the PLA matrix enhanced the Young modulus, tensile strength, ultimate strain and tensile toughness of the extended PLA sample with benzoyl peroxide (BP) between 40-100%. The observed enhancements originated from restricted PLA molecular motions, assisted PLA crystallization and intensified BP activity in extending the PLA chains. In contrast, EG nanofiller (EGS), with the lowest aspect ratio and size, lowered the PLA relaxation time and accelerated the PLA crystallization. This type of EG showed the weakest reinforcing effect on PLA. For the EG type (EGM) with an intermediate size and aspect ratio, it was observed that the presence of the nanoparticles had a negligible effect on the PLA molecular dynamic and reduced the PLA crystallization rate. The highest impact strength was observed for the PLA/EGM nanocomposite at 1 phr loading.

Aynı Yöne Dönen Çift Vidalı Ekstrüderli Tandem Bir Termoplastik Geri Dönüşüm Sisteminde Vida Yapılanmasının İncelenmesi

Polymers have rapidly replaced the utilization of glasses, ceramics, metals, and organic textiles due to their cost-effectiveness, lightweight nature, and enhanced functionality. Nevertheless, as a consequence of their chemical composition, polymers undergo a protracted degradation process in natural environments, resulting in a significant accumulation of plastic waste since their inception. This accumulation has now reached a critical threshold, posing a substantial risk to both human well-being and the preservation of natural ecosystems. In the recycling process of thermoplastic wastes, it is necessary to subject them to two rounds of melting in order to obtain compounds. This practice results in a reduction of the recycling numbers associated with thermoplastics, which possess a finite recycling lifespan, by 50%. The present work involved the construction of a tandem recycling process, wherein molten waste polymers were immediately introduced into a co-rotating twin screw extruder. In contrast to alternative approaches, a process-dependent screw configuration has been devised for the twin-screw system employed in the delivery of molten material. The product derived from 80% waste thermoplastic was thereafter compared to the original product as an outcome of the aforementioned procedure. Properties similar to those of pure Polypropylene were seen in some physical and chemical characteristics.

Influence of Extruder Setup and Process Parameters on the Product Quality of Solid Polymer Electrolytes Using Melt Extrusion

All solid-state batteries (ASSBs) are the next generation battery technology, in which the classical liquid electrolyte is replaced by an ion-conducting solid electrolyte. Materials that are used as solid-state electrolytes are generally divided into three material classes: polymers, oxides and sulphides. Electrolyte materials for ASSBs have been extensively studied regarding their electrochemical performance and their stability towards the electrode materials. Nevertheless, the commercialization of ASSBs is still hindered by the material availability in case of oxide and sulphides and the knowledge of scaled production routes for all kinds of separators. Polymers are readily available on the global market. It is thus possible to focus more on the processing routes of polymer based solid electrolytes. The use of thermoplastics as matrix for solid electrolytes (SE) offers the prospect of facile upscaling of the process from lab-scale to industrial series production by the implementation of a solvent-free thermal extrusion process. A twin-screw extruder offers the possibility of continuously mixing the SE components to produce homogeneous polymer based SEs. With two feeding units, the addition of the components takes place separately. This eliminates the time-consuming premixing step to obtain a homogeneous mixture.Thermoplastic poly(ethylene oxide) (PEO) is one of the most investigated materials for polymer based SEs due to its capability to dissolve alkali salts like Lithium(bistrifluoromethanesulfonyl)imide (LiTFSI). The thermal process route of PEO and its effect on the polymeric properties are currently under investigation. Previous works from our research group show that the processability of PEO not only depends on the conductive salt (LiTFSI), but also on its molecular weight and applied process parameters. [1] With increasing molecular weight, PEO becomes more sensitive towards thermal and mechanical load that leads to chain scissoring and degradation even at small load. Hence, the use of low molecular weight PEO (Mw= 100.000 g mol-1) is preferable for the dry production of PEO based SEs.The aim of this work is to optimize the extrusion process using a co-rotating twin-screw extruder for the solvent free production of solid PEO/LiTFSI-electrolytes in a molar ratio of 20:1 (EO:Li). Here, we investigate the effects of several extruder set-ups on the mixing behaviour of PEO and LiTFSI. Therefore, type of dosing and screw design are varied. The screw can be designed with conveying, kneading and mixing elements. We compare the dry extrusion of a premixed PEO/LiTFSI (20:1) batch with dry extrusion of PEO/LiTFSI (20:1) using two feeding units, one for each component. Process parameters, such as pressure at the extruder die, actual screw speed, torque and barrel temperature are continuously measured during the production. Process temperature and screw speed are optimized to avoid degradation of PEO. PEO/LiTFSI-electrolytes are produced with a process temperature of 90 °C across the whole extruder barrel and with screw speeds of 5 – 15 rpm. The products are evaluated by their homogeneity and quality of the extruded electrolytes. Optical microscopy is used for macroscopic evaluation and the Li-salt distribution is checked with SEM/EDX. Conductivity and rheology measurements are performed to determine the lithium concentration within the electrolyte and loss of molecular weight, respectively. For the determination of the ionic conductivity, we examine electrochemical impedance spectroscopy (EIS). The characterization of the extruded electrolytes helps to find optimal process parameters for the production of polymer based SEs.

Preparation and characterization of woven jute fabric layered composite by using bamboo fiber reinforced polymers as resin matrix

In the present study, a novel hybrid composite product has been prepared by using plain woven jute fabric as one component and short bamboo fiber reinforced thermoplastic (BPC) as the second component. BPC was prepared using a co-rotating twin screw extruder and the same was used as a resin matrix for preparing hybrid jute fabric composite (JFC) via layering method. In this work, the effect of polymer type i.e., polypropylene (PP) and high-density polyethylene (HDPE), coupling agent (CA) and bamboo fiber content (10%, 30%, and 50%) in the BPC on physical, mechanical, water absorption and thermal properties of JFC has been investigated. The properties of BPC bonded JFC were compared with similarly produced composites using neat polymers. Mechanical properties and water absorption behavior in BPC bonded JFC were significantly improved with increased proportion of bamboo fibers in BPC, more specifically up to 30% fiber reinforcement. Also, the properties in fabricated composite were significantly higher in samples added with CA. Experimental results showed that flexural strength in 3L/JFC prepared with 30%-BPC was increased by 35% and 50%, as compared to similarly produced composite from neat PP and HDPE, respectively. Similarly, compared to neat PP and HDPE based JFC, the flexural modulus of 3L/JFC prepared with 30%-BPC was increased by 79% and 120%, respectively. Scanning electron microscopic images showed the evidence of physical bonding between BPC matrix and jute fabric in the form of mechanical interlocking. In general, the properties of BPC bonded hybrid JFC were significantly higher than those of similar composites made from pure polymers.

Simulation of Multiphase Flow and Mixing in a Conveying Element of a Co-Rotating Twin-Screw Extruder by Using SPH

Multiphase flows and mixing in partially filled conveying elements of twin-screw extruders (TSEs) were simulated by using smoothed-particle hydrodynamics (SPH). A validation of SPH using experiment from the literature for a co-rotating twin-cam mixer indicated good agreement. A two-phase Poiseuille flow was also used to validate the accuracy of our approach. The results of two-phase flow in TSE show that the viscosity ratio significantly affects the flow and mixing of two-phase fluids. The symmetry of flow field is broken with different parameters. In the full filled case, the pressure squeezes particles into the gap, which is conducive to improve the performance of mixing of fluids. On the contrary, in the partially filled case, because there is no background pressure, particles tend to bypass the gap and flow to the cavity of the chamber. This work laid a foundation for further study of polymer blending by simulation.

Spray Drying Enzyme-Treated Cellulose Nanofibrils.

Enzyme-treated cellulose nanofibrils (CNFs) were produced via a lab-scale mass colloider using bleached kraft pulp (BKP) to evaluate their processability and power requirements during refining and spray-drying operations. To evaluate the energy efficiency in the CNF refining process, the net energy consumption, degree of polymerization (DP), and viscosity were determined. Less energy was consumed to attain a given fines level by using the endoglucanase enzymes. The DP and viscosity were also decreased using the enzymes. The morphological properties of the enzyme-pretreated spray-dried CNF powders (SDCNFs) were measured. Subsequently, the enzyme-pretreated SDCNFs were added to a PP matrix with MAPP as a coupling agent. The mixture was then compounded through a co-rotating twin-screw extruder to determine whether the enzyme treatment of the CNFs affects the mechanical properties of the composites. Compared to earlier studies on enhancing PMCs with SDCNF powders, this research investigates the use of enzyme-pretreated SDCNF powders. It was confirmed that the strength properties of PP increased by adding SDCNFs, and the strength properties were maintained after adding enzyme-pretreated SDCNFs.

Thermo-mechanical and morphological studies of Hal-reinforced PEEK

This study is focused on exploring the thermo-mechanical properties and behaviour of PEEK-Hal nanocomposites as a case study for understanding the interactions between nanoparticles and polymers, as well as to explore potential applications of nanocomposites in the field of engineering. The selection of Poly (ether ether ketone) (PEEK) polymer is based on its notable chemical resistance, exceptional mechanical properties and high thermo-oxidative stability. Halloysite nanotubes (Hal) are chosen for their environmentally friendly nature, non-toxic properties, cost-effectiveness, tuneable release and rapid adsorption rates. This research paper focuses on the fabrication of PEEK-Hal polymer composites with varying concentrations using a co-rotating twin screw extruder. The prepared composites are thoroughly characterized using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The mechanical properties are assessed using a universal testing machine (UTM), impact tester, and hardness tester, respectively. The surface morphology is examined using field emission scanning electron microscopy (FE-SEM) technique. The results highlight the substantial benefits of incorporating Hal, improving interfacial adhesion, and establishing favourable interactions between the PEEK and Hal. The incorporation of Hal notably enhances the stiffness and storage modulus of the PEEK-Hal composites. Additionally, the presence of Hal restrains the mobility of the macromolecular chains within the composite. This study demonstrates that the PEEK-Hal composite with a 3% concentration of Hal (PH3) exhibits remarkable thermo-mechanical properties.

Investigation of the effect of materials and processing conditions in twin-screw extrusion

Three polymeric materials; polystyrene (amorphous), low-density polyethylene (semi-crystalline), and poly(methyl methacrylate) (amorphous) were used to explore their behavior and properties during processing using a co-rotating twin-screw extruder. Injection molding and compression molding were used for preparing the test specimens. Screw speed and barrel set temperatures were considered as the main processing variables while observing the process energy consumption of the extruder. The tensile, thermal, and rheological properties of the extruded materials under different processing conditions were evaluated. Test results confirmed that the motor power of the extruder for processing polystyrene and low-density polyethylene increased with increasing screw speed and decreased with increasing barrel set temperatures. Motor power for processing poly(methyl methacrylate) increased significantly with increasing screw speed. The total power consumption of the barrel heaters for processing polystyrene and low-density polyethylene slightly increased with the barrel set temperatures. The tensile modulus of polystyrene decreased with increasing screw speed at higher barrel set temperatures, while low-density polyethylene showed no significant variation. The tensile modulus of poly(methyl methacrylate) did not exhibit a clear trend with the extruder process settings. The effect of process settings on the glass transition temperature and melting temperature of the polymers was not significant, and no evidence was found of any molecular degradation during processing. Rheological properties of poly(methyl methacrylate) showed a significant variation with increasing screw speed and barrel set temperatures, while those of polystyrene and low-density polyethylene did not exhibit a consistent variation.

Optimization of Machine and Process Parameters for Development of Protein and Antioxidant Rich Composite Food using Twin Screw Extruder

Background: Nutritional quality of extruded products can be enhanced through protein, minerals and antioxidants rich foods viz. legumes, green leafy vegetables, dietary fibres, by-products, etc, leading to improvement in functional properties of products and health of consumers. Methods: Extrudates were prepared from maize, defatted soy meal, sesame and spinach using a co-rotating twin screw extruder and dried in a tray dryer at 50oC up to about 5.5% moisture content (w.b.) and analyzed for important product quality parameters. Result: Quality characteristics of developed food grains-spinach based composite food were affected by variability in independent studied parameters. Optimized extrusion conditions for desired composite food from food grains-spinach were as 14% moisture content, 117oC DHT and 335rpm screw speed. These conditions resulted in the products with 18.26% protein, 73.88% in vitro protein digestibility, 2.46 protein efficiency ratio, 2.84% total minerals, 4.67mg/100g iron, 190 mg/100g calcium, 24.05% antioxidant activity with consumer acceptability ≥7 by 92.52%.

Resource-efficient manufacturing process of composite materials: Fibrillation of recycled textiles and compounding with thermoplastic polymer

This study aimed to develop a manufacturing process for recycled textile long fiber thermoplastics (RT-LFT) and thereby contribute to circular economy. Three different post-consumer textiles (cotton denim and plain weave, and silk plain weave) were cut into strips and fed directly into a co-rotating twin-screw extruder in which the textile was fibrillated and compounded with polypropylene (PP). The fibrillation of the textile, fiber dispersion, and interaction with the matrix polymer were studied, and the thermal and mechanical properties of the composites were evaluated. For example, cotton denim composites containing 30 wt% fiber content resulted in 26% increase in yield strength and a 72% increase in modulus when compared with that of PP. The RT-LFT process is a straightforward method for transforming used textiles into composites like cups and bottoms, offering advantages such as reduced manufacturing costs, add value for waste material, and lower carbon emissions.

Tailoring PLA/ABS Blends Compatibilized with SEBS-g-MA through Annealing Heat Treatment.

In this work, blends based on poly (lactic acid) (PLA)/acrylonitrile-butadiene-styrene (ABS) compatibilized with maleic anhydride-grafted (SEBS-g-MA) were prepared in a co-rotational twin-screw extruder by varying the concentrations of the compatibilizing agent. The influence of the compatibilizing agent on the morphology, mechanical, thermal, thermomechanical, and rheological properties of the prepared materials was analyzed. The effect of annealing on the properties of the blends was also investigated using injection-molded samples. The X-ray diffraction (XRD) results proved that the increments in crystallinity were an effect of annealing in the PLA/ABS/SEBS-g-MA blends, resonating at higher heat deflection temperatures (HDTs). The impact strength of the PLA/ABS blends compatibilized with 10 wt% SEBS-g-MA was significantly increased when compared to the PLA/ABS blends. However, the hardness and elastic modulus of the blends decreased when compared to neat PLA. The refined morphology shown in the scanning electron microscopy (SEM) analyses corroborated the improved impact strength promoted by SEBS-g-MA. The torque rheometer degradation study also supported the increased compatibility between SEBS-g-MA, PLA, and ABS. The TGA results show that the PLA/ABS and PLA/ABS/SEBS-g-MA blends are more thermally stable than the neat PLA polymer at higher temperatures. The results showed that the ideal composition is the heat-treated PLA/ABS/SEBS-g-MA (60/30/10 wt%), given the high impact strength and HDT results. The results of this work in terms of mechanical improvement with the use of compatibilizers and annealing suggest that the PLA/ABS/SEBS-g-MA system can be used in the production of 3D-printing filaments.

Development of 3D printed nanomaterials for restoration of exterior artworks

Despite the great potential of 3D printing technologies coupled with nanotechnologies, just few studies are present in the scientific literature. Application of nanocomposites materials for 3D printing in the field of cultural heritage restoration, is a promising approach to obtain novel and functionalized materials for the artworks element to be recreated. In this context, the present work aims to study innovative nanocomposites materials suitable for the considered application. A commercial PLA filament was additivated with SiC, SiO2 and TiO2 nanoparticles, synthetized by CO2 laser pyrolysis. Nanocomposite filaments were produced by a co-rotating twin-screw extruder and specimens were produced by 3D printing and analysed against their mechanical and hydrophobic properties by means of tensile tests and water absorption and contact angle measurements, respectively.

Flow modeling for conveying sections in a co-rotating twin-screw extruder based on energy dissipation rate for continuous mixing of lithium-ion battery slurries

In the present work, we propose a new modeling scheme for flows of non-Newtonian fluids in the fully filled narrow-pitched conveying section in a co-rotating twin screw extruder, emphasizing the application to viscoplastic lithium-ion battery slurries for electrode manufacturing. A predictive tool for the relationship between flow rate, screw speed, and pressure build-up was presented for flows with a general class of inelastic non-Newtonian fluids. By introducing the effective viscosity and effective shear rate based on the energy dissipation rate, we showed that the conventional relationship between throughput number and pressure number for various non-Newtonian fluids collapse into a single master curve of a Newtonian fluid, from which the predictive relationship between flow rate, screw speed, and pressure build-up was established. The method was validated numerically with power-law fluids, a Carreau fluid, and a Herschel-Bulkley fluid (anode slurries) for a narrow-pitched conveying element module.

Designing of carbon fiber-reinforced polymer (CFRP) composites for a second-life in the aeronautic industry: strategies towards a more sustainable future

Over the last few years, the use of carbon fiber-reinforced polymer composites (CFRP) in the aeronautic sector has significantly increased, given these materials’ outstanding properties. Consequently, the accumulation of composite residues is becoming an environmental hurdle. Therefore, in a world where sustainability and circularity remain on the lead, the replacement of thermosets by thermoplastics as polymeric matrices emerges as a promising technique, given the recyclability of these materials. Following this perspective, in this work, carbon fiber-reinforced polymer (CFRP) composite “residues” were incorporated into a poly(etheretherketone) (PEEK) matrix, as a strategy towards a more sustainable future, aiming at developing novel compounds for the aeronautic industry. The influence of two different fiber sizes (<600 and 600–1000 μm) on the neat PEEK properties was assessed through formulations developed using a co-rotating twin screw-extruder, under optimized processing conditions. Furthermore, the potential thermo-oxidative degradation, and the recycling feasibility of the neat PEEK and its compounds, were evaluated by submitting the materials to several thermo-mechanical cycles. The results showed that PEEK compounds were successfully prepared, and presented a good fiber distribution and absence of fiber agglomerates. A positive impact on the mechanical performance of PEEK was found by the incorporation of 3.3 wt.% of short carbon fibers (sCF) with larger sizes (600–1000 μm). The reprocessing of neat PEEK and its compounds for 15 consecutive cycles demonstrated their remarkable thermo-mechanical stability, without any sign of degradation or irreversible loss of properties. The fiber length and fiber length distribution of reprocessed compounds showed that major variations occurred after the first extrusion cycle, especially for larger sizes.

Emission and Mechanical Properties of Glass and Cellulose Fiber Reinforced Bio-Polyamide Composites.

Climate change, access, and monopolies to raw material sources as well as politically motivated trade barriers are among the factors responsible for a shortage of raw materials. In the plastics industry, resource conservation can be achieved by substituting commercially available petrochemical-based plastics with components made from renewable raw materials. Innovation potentials are often not used due to a lack of information on the use of bio-based materials, efficient processing methods, and product technologies or because the costs for new developments are too high. In this context, the use of renewable resources such as fiber-reinforced polymeric composites based on plants has become an important criterion for the development and production of components and products in all industrial sectors. Bio-based engineering thermoplastics with cellulose fibers can be used as substitutes because of their higher strength and heat resistance, but the processing of this composite is still challenging. In this study, composites were prepared and investigated using bio-based polyamide (PA) as a polymer matrix in combination with a cellulosic fiber and, for comparison purposes, a glass fiber. A co-rotating twin-screw extruder was used to produce the composites with different fiber contents. For the mechanical properties, tensile tests and charpy impact tests were performed. Compared to glass fiber, reinforced PA 6.10 and PA 10.10, a significantly higher elongation at break with regenerated cellulose fibers, can be achieved. PA 6.10 and PA 10.10 achieve significantly higher impact strengths with the regenerated cellulose fibers than the composites with glass fibers. In the future, bio-based products will also be used in indoor applications. For characterization, the VOC emission GC-MS analysis and odor evaluation methods were used. The VOC emissions (quantitative) were at a low level but the results of the odor tests of selected samples showed values mostly above the required limit values.

Polypropylene Degradation on Co-Rotating Twin-Screw Extruders.

Nowadays, usable plastic materials with defined properties are created by blending additives into the base polymer. This is the main task of compounding on co-rotating twin-screw extruders. The thermal and mechanical stress occurring in the process leads to a mostly irreversible damage to the material. Consequently, the properties of the polymer melt and the subsequent product are affected. The material degradation of polypropylene (PP) on a 28 mm twin-screw extruder has already been studied and modeled at Kunststofftechnik Paderborn. In this work, the transferability of the previous results to other machine sizes and polypropylene compounds were investigated experimentally. Therefore, pure polypropylene was processed with screw diameters of 25 mm and 45 mm. Furthermore, polypropylene compounds with titanium dioxide as well as carbon fibers were considered on a 28 mm extruder. In the course of the evaluation of the pure polypropylene, the melt flow rates of the samples were measured and the molar masses were calculated on this basis. The compounds were analyzed by gel permeation chromatography. As in the previous investigations, high rotational speeds, low throughputs and high melt temperatures lead to a higher material degradation. In addition, it is illustrated that the previously developed model for the calculation of material degradation is generally able to predict the degradation even for different machine sizes by adjusting the process coefficients. In summary, this article shows that compounders can use the recommendations for action and the calculation model for the material degradation of polypropylene, irrespective of the machine size, to design processes that are gentle on the material.