Production of Filament Yarns Made of PEEK

This project is a part of European commission collaborative Safeprotex project of Seventh Framework Programme to manufacture high protective clothing for complex emergency operations. The goal of this thesis is to manufacture polyetheretherketone, PEEK, fibers by melt spinning and modify them to provide antimicrobial, self-cleaning and antipollution properties. PEEK has excellent thermal and mechanical properties and good chemical resistance. The literature review clearly shows that PEEK should be easily spinnable. Melt spinning is a process where polymer is melted, normally by extruder or piston system. The system of TUT is based on Göttfert capillary rheometer which is a piston system. Melt material is pushed through a small hole after which it faces cold air and starts to cool down. Solidified fiber is drawn to a roll. PEEK modification is done by sulfonate groups that change the chemical structure so that functional properties are possible. Without modification the reaction does not happen. Reaction is based on benzophenone compounds that are excited by UV-light. During the experimental part DSC, TGA and rheological tests were made to characterize PEEK. The results of these tests confirm that PEEK has excellent thermal properties and it should be easily spinnable. Fiber spinning of virgin PEEK turned out to be easy and the best achieved fibers were less than 20 μm in diameter. Operating temperature and hole diameter turned out to be the most important parameters in our spinning system. TUT piston system, Göttfert capillary rheometer is not designed for fiber spinning which lead to a few problems most importantly variations in fiber thickness. PEEK modification was done by our Italian partner company Next Technology Tecnotessile. Modification provided wanted functional properties but it also made spinning more difficult, worsened thermal stability and made the fibers more brittle. Modified PEEK was mixed with virgin PEEK to avoid these problems. At best, 1.5 % of modified PEEK could be added to virgin PEEK and still be able to make fibers of it. /Kir1

Melt Spinning, Functionalization and Durability of Polyetheretherketone-Based Fibres

Polyetheretherketone (PEEK)-based polymer fibres have attracted much interest due to their many outstanding properties. Along with one of the highest use temperatures among thermoplastics, PEEK also has excellent mechanical properties and chemical resistance. Because of these properties, PEEK and PEEK fibres are often used in demanding conditions. In this dissertation, PEEK-based polymer fibres were pushed to the limit in four different situations: melt spinning of fine filaments, photoageing, maximum recommended use temperature, and contaminants. To fight contaminants, PEEK was modified via a sulfonation reaction into sulfonated polyetheretherketone (SPEEK) and then melt compounded with polypropylene (PP) to produce antimicrobial and self-cleaning properties. The goal of this dissertation was not only to measure changes in the properties but also to improve the properties.The general spinnability of PEEK was good with viscosity control deemed crucial to improving that spinnability. In addition to a long and large die and a short spinning path, a low viscosity PEEK grade and a high processing temperature are recommended. Tests provided new information on the quantitative effects of processing parameters on the smallest spinnable fibre diameter. The smallest obtained fibres had an average diameter of 18 µm and a mechanical strength of approximately 280 MPa.Photodegradation was one of the main weaknesses of PEEK fibres. Ageing PEEK for up to 1056 h in a UV chamber degraded the fibres rapidly from elastic to brittle. Thermal ageing, for up to 128 d at 250 °C, produced effects similar to those of photoageing, including embrittlement, but also some different effects. In both cases, ageing caused crosslinking, which was verified by rheological measurements. Changes in the carbonyl group absorption band, measured by Fourier transform infrared spectroscopy (FTIR), were significantly bigger in photodegradation than in thermal degradation. Differential scanning calorimetry (DSC) turned out to be a poor method to detect ageing in photodegradation, but in thermal degradation it revealed a decrease in the melting temperature and an increase in the glass transition temperature. In both cases, decreased thermal stability was verified by thermogravimetric analysis (TGA).A SPEEK/PP blend was successfully produced in various compositions. Compounding produced an immiscible polymer blend, in which approximately 1-µm SPEEK particles were homogenously dispersed in the PP matrix. According to electron paramagnetic resonance (EPR) measurements, this blend formed stable radicals with their number correlating with the SPEEK concentration. The thermal properties of SPEEK were inferior to those of PEEK, a reason that made the melt spinning of SPEEK/PP blend challenging. At 200 °C, stable melt spinning process was achieved and good quality yarns were produced. The mechanical tenacity of SPEEK/PP 5:95 yarns was approximately 20% lower than that of otherwise similar PP yarns

Text Topics and Treatment Response in Internet-Delivered Cognitive Behavioral Therapy for Generalized Anxiety Disorder : Text Mining Study

Publisher Copyright: © 2022 Sanna Mylläri, Suoma Eeva Saarni, Ville Ritola.Background: Text mining methods such as topic modeling can offer valuable information on how and to whom internet-delivered cognitive behavioral therapies (iCBT) work. Although iCBT treatments provide convenient data for topic modeling, it has rarely been used in this context. Objective: Our aims were to apply topic modeling to written assignment texts from iCBT for generalized anxiety disorder and explore the resulting topics' associations with treatment response. As predetermining the number of topics presents a considerable challenge in topic modeling, we also aimed to explore a novel method for topic number selection. Methods: We defined 2 latent Dirichlet allocation (LDA) topic models using a novel data-driven and a more commonly used interpretability-based topic number selection approaches. We used multilevel models to associate the topics with continuous-valued treatment response, defined as the rate of per-session change in GAD-7 sum scores throughout the treatment. Results: Our analyses included 1686 patients. We observed 2 topics that were associated with better than average treatment response: "well-being of family, pets, and loved ones"from the data-driven LDA model (B=-0.10 SD/session/Δtopic; 95% CI -016 to -0.03) and "children, family issues"from the interpretability-based model (B=-0.18 SD/session/Δtopic; 95% CI -0.31 to -0.05). Two topics were associated with worse treatment response: "monitoring of thoughts and worries"from the data-driven model (B=0.06 SD/session/Δtopic; 95% CI 0.01 to 0.11) and "internet therapy"from the interpretability-based model (B=0.27 SD/session/Δtopic; 95% CI 0.07 to 0.46). Conclusions: The 2 LDA models were different in terms of their interpretability and broadness of topics but both contained topics that were associated with treatment response in an interpretable manner. Our work demonstrates that topic modeling is well suited for iCBT research and has potential to expose clinically relevant information in vast text data.Peer reviewe

New particle formation in the fresh flue-gas plume from a coal-fired power plant: effect of flue-gas cleaning

Atmospheric emissions, including particle number and size distribution, from a 726 MWth coal-fired power plant were studied experimentally from a power plant stack and flue-gas plume dispersing in the atmosphere. Experiments were conducted under two different flue-gas cleaning conditions. The results were utilized in a plume dispersion and dilution model taking into account particle formation precursor (H2SO4 resulted from the oxidation of emitted SO2) and assessment related to nucleation rates. The experiments showed that the primary emissions of particles and SO2 were effectively reduced by flue-gas desulfurization and fabric filters, especially the emissions of particles smaller than 200 nm in diameter. Primary pollutant concentrations reached background levels in 200–300 s. However, the atmospheric measurements indicated that new particles larger than 2.5 nm are formed in the flue-gas plume, even in the very early phases of atmospheric ageing. The effective number emission of nucleated particles were several orders of magnitude higher than the primary particle emission. Modelling studies indicate that regardless of continuing dilution of the flue gas, nucleation precursor (H2SO4 from SO2 oxidation) concentrations remain relatively constant. In addition, results indicate that flue-gas nucleation is more efficient than predicted by atmospheric aerosol modelling. In particular, the observation of the new particle formation with rather low flue-gas SO2 concentrations changes the current understanding of the air quality effects of coal combustion. The results can be used to evaluate optimal ways to achieve better air quality, particularly in polluted areas like India and China

The impact of 3D printing process parameters on the dielectric properties of high permittivity composites

Fused filament fabrication (FFF) is a well-known and greatly accessible additive manufacturing technology, that has found great use in the prototyping and manufacture of radiofrequency componentry, by using a range of composite thermoplastic materials that possess superior properties, when compared to standard materials for 3D printing. However, due to their nature and synthesis, they are often a great challenge to print successfully which in turn affects their microwave properties. Hence, determining the optimum printing strategy and settings is important to advance this area. The manufacturing study presented in this paper shows the impact of the main process parameters: printing speed, hatch spacing, layer height and material infill, during 3D printing on the relative permittivity (εr), and loss tangent (tanδ) of the resultant additively manufactured test samples. A combination of process parameters arising from this study, allowed successful 3D printing of test samples, that marked a relative permittivity of 9.06 ± 0.09 and dielectric loss of 0.032 ± 0.003

Production of Filament Yarns Made of PEEK

This project is a part of European commission collaborative Safeprotex project of Seventh Framework Programme to manufacture high protective clothing for complex emergency operations. The goal of this thesis is to manufacture polyetheretherketone, PEEK, fibers by melt spinning and modify them to provide antimicrobial, self-cleaning and antipollution properties. PEEK has excellent thermal and mechanical properties and good chemical resistance. The literature review clearly shows that PEEK should be easily spinnable. Melt spinning is a process where polymer is melted, normally by extruder or piston system. The system of TUT is based on Göttfert capillary rheometer which is a piston system. Melt material is pushed through a small hole after which it faces cold air and starts to cool down. Solidified fiber is drawn to a roll. PEEK modification is done by sulfonate groups that change the chemical structure so that functional properties are possible. Without modification the reaction does not happen. Reaction is based on benzophenone compounds that are excited by UV-light. During the experimental part DSC, TGA and rheological tests were made to characterize PEEK. The results of these tests confirm that PEEK has excellent thermal properties and it should be easily spinnable. Fiber spinning of virgin PEEK turned out to be easy and the best achieved fibers were less than 20 μm in diameter. Operating temperature and hole diameter turned out to be the most important parameters in our spinning system. TUT piston system, Göttfert capillary rheometer is not designed for fiber spinning which lead to a few problems most importantly variations in fiber thickness. PEEK modification was done by our Italian partner company Next Technology Tecnotessile. Modification provided wanted functional properties but it also made spinning more difficult, worsened thermal stability and made the fibers more brittle. Modified PEEK was mixed with virgin PEEK to avoid these problems. At best, 1.5 % of modified PEEK could be added to virgin PEEK and still be able to make fibers of it. /Kir1

Melt Spinning, Functionalization and Durability of Polyetheretherketone-Based Fibres

Polyetheretherketone (PEEK)-based polymer fibres have attracted much interest due to their many outstanding properties. Along with one of the highest use temperatures among thermoplastics, PEEK also has excellent mechanical properties and chemical resistance. Because of these properties, PEEK and PEEK fibres are often used in demanding conditions. In this dissertation, PEEK-based polymer fibres were pushed to the limit in four different situations: melt spinning of fine filaments, photoageing, maximum recommended use temperature, and contaminants. To fight contaminants, PEEK was modified via a sulfonation reaction into sulfonated polyetheretherketone (SPEEK) and then melt compounded with polypropylene (PP) to produce antimicrobial and self-cleaning properties. The goal of this dissertation was not only to measure changes in the properties but also to improve the properties.The general spinnability of PEEK was good with viscosity control deemed crucial to improving that spinnability. In addition to a long and large die and a short spinning path, a low viscosity PEEK grade and a high processing temperature are recommended. Tests provided new information on the quantitative effects of processing parameters on the smallest spinnable fibre diameter. The smallest obtained fibres had an average diameter of 18 µm and a mechanical strength of approximately 280 MPa.Photodegradation was one of the main weaknesses of PEEK fibres. Ageing PEEK for up to 1056 h in a UV chamber degraded the fibres rapidly from elastic to brittle. Thermal ageing, for up to 128 d at 250 °C, produced effects similar to those of photoageing, including embrittlement, but also some different effects. In both cases, ageing caused crosslinking, which was verified by rheological measurements. Changes in the carbonyl group absorption band, measured by Fourier transform infrared spectroscopy (FTIR), were significantly bigger in photodegradation than in thermal degradation. Differential scanning calorimetry (DSC) turned out to be a poor method to detect ageing in photodegradation, but in thermal degradation it revealed a decrease in the melting temperature and an increase in the glass transition temperature. In both cases, decreased thermal stability was verified by thermogravimetric analysis (TGA).A SPEEK/PP blend was successfully produced in various compositions. Compounding produced an immiscible polymer blend, in which approximately 1-µm SPEEK particles were homogenously dispersed in the PP matrix. According to electron paramagnetic resonance (EPR) measurements, this blend formed stable radicals with their number correlating with the SPEEK concentration. The thermal properties of SPEEK were inferior to those of PEEK, a reason that made the melt spinning of SPEEK/PP blend challenging. At 200 °C, stable melt spinning process was achieved and good quality yarns were produced. The mechanical tenacity of SPEEK/PP 5:95 yarns was approximately 20% lower than that of otherwise similar PP yarns

The effects of UV irradiation to polyetheretherketone fibres : Characterization by different techniques

The effects of UV irradiation on polyetheretherketone (PEEK) fibres were investigated in this study. PEEK fibres were manufactured with a melt spinning system and then artificially aged with simulated solar UV light. Fibres were then characterized by mechanical tests, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), rheology, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). PEEK, best known for its excellent thermal stability, suffered greatly from the effects of UV irradiation. The low UV stability manifested as embrittlement of the fibres in the mechanical tests, increased crosslinking rate in the rheological tests, formation of carbonyl and hydroxyl groups and changes in the nature of the carbon-hydrogen bonds in the FTIR, diminished thermal properties in TGA, and transverse cracks in the SEM photos. DSC was found to be an inaccurate technique for estimating the degradation level of PEEK fibres, whereas the carbonyl index measured by FTIR was found to be the most convenient technique. © 2014 Elsevier Ltd. All rights reserved.submittedVersionPeer reviewe

A comparison of rheology and FTIR in the study of polypropylene and polystyrene photodegradation

Rheology and FTIR spectroscopy are compared as methods to study the degree of photodegradation in polypropylene (PP) and polystyrene (PS) sheets. The materials are hot pressed, artificially photo-aged with fluorescent lights for 4-2048 h and then measured with a rotational rheometer and FTIR. Both materials show a tendency for chain scission which can be seen as a reduction in viscosity. Changes in PP can be observed with both methods after 256 h of irradiation. Changes in PS become significant in rheology after 64 h but in FTIR only after 1024 h of irradiation. Due to the different chemical nature of the materials, the degradation of PS is rather linear with exposure, whereas the degradation of PP is more exponential. Using the zero shear viscosities obtained through extrapolations of the Cole-Cole and Carreau-Yasuda models, relative molecular weights are estimated with the aid of the power-law relationship between these two. These results are compared with the carbonyl indices determined from the FTIR spectra. Rheology is found to be a viable alternative for FTIR in certain situations.acceptedVersionPeer reviewe

Characterization of thermally aged polyetheretherketone fibres : Mechanical, thermal, rheological and chemical property changes

This paper investigates the effects of thermal degradation on polyetheretherketone (PEEK) fibres. PEEK samples were aged at a constant temperature of 250 °C for 1-128 days and characterized with mechanical tests, FTIR (Fourier Transform Infrared Spectroscopy), DSC (Differential Scanning Calorimetry), rheology, TGA (Thermogravimetric Analysis), SEM (Scanning Electron Microscopy), and UV-Vis diffuse reflectance spectroscopy. The short-term thermal annealing had a positive effect on the mechanical properties, due to the formation and growth of secondary crystals. Crosslinking in the material was verified by rheological inspections. The crosslinking increased the mechanical strength and modulus but reduced the elongation at break of the fibres. FTIR tests showed that carbonyl and hydroxyl groups were slowly formed on the surface of the fibres while ring opening reactions took place. The thermal ageing reduced the thermal stability of PEEK. The decreased stability was observed in the decomposition onset temperature after 8 d and in the melting point and the glass transition temperature after 32 d. The first signs of degradation, crosslinking, embrittlement, and reduced thermal stability, were visible roughly after 8 d of ageing, whereas the deterioration in general usability occurred after 64 d.submittedVersionPeer reviewe