Acid aging effects on surfaces of PTFE gaskets investigated by thermal analysis

This paper investigates the effect of a prolonged acid attack on the surface of PTFE by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). PTFE is very non-reactive, partly because of the strength of carbon\u2013fluorine bonds and for its high crystallinity, and, as a consequence, it is often used in containers and pipework with reactive and corrosive chemicals. The PTFE under analysis is commercialized by two alternative producers in form of Teflon tapes. These tapes are adopted, as gaskets, in process plants where tires moulds are cleaned by acid solutions inside a multistage ultrasonic process. In this case, PTFE shows, in a relatively short operation time, inexplicably phenomena of surface degradation, which could be related, in general terms, to an acid attack. But, even considering the combined effect of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the risk of the extreme erosion phenomena as observed. The present experimental research aim at investigating this contradiction. A possible explanation could be related to the presence in the cleaning solution of unexpected fluorides, able to produce fluorinating agents and, thus, degrade carbon-fluorine bonds. Considering more the 300 chemical elements a tire compound consists in, it is really complex to preserve the original chemical composition of the cleaning solution. In this research PTFE samples have been treated with different mixtures of acids with the aim at investigating the different aging effects. The thermal analysis has permitted the experimental characterization of PTFE surface properties after acid attack, providing evidence of the degradation phenomena. In particular, the different acid treatments adopted for accelerating the aging of gaskets have highlighted the different behaviour of the PTFE matrix, but also differences between manufacturers

Carbon Fibers Waste Recovery via Pyro-Gasification: Semi-Industrial Pilot Plant Testing and LCA

Carbon-fiber-reinforced polymers (CFRPs) are increasingly used in a variety of applications demanding a unique combination of mechanical properties and lightweight characteristics such as automotive and aerospace, wind turbines, and sport and leisure equipment. This growing use, however, has not yet been accompanied by the setting of an adequate recycling industry, with landfilling still being the main management route for related waste and end-of-life products. Considering the fossil-based nature of carbon fibers, the development of recovery and recycling technologies is hence prioritized to address the environmental sustainability challenges in a bid to approach mitigating the climate emergency and achieving circularity in materials’ life cycles. To this aim, we scaled up and tested a novel semi-industrial pilot plant to pyrolysis and subsequent oxidation of uncured prepreg offcuts and cured waste of CFRPs manufacturing. The environmental performance of the process proposed has been evaluated by means of a life cycle assessment to estimate the associated carbon footprint and cumulative energy demand according to three scenarios. The scale-up of the process has been performed by investigating the influence of the main parameters to improve the quality of the recovered fibers and the setting of preferable operating conditions. The pyro-gasification process attested to a reduction of 40 kgCO2 eq per kg of recycled CFs, compared to virgin CFs. If the pyro-gasification process was implemented in the current manufacturing of CFRPs, the estimated reduction of the carbon footprint, depending on the composite breakdown, would result in 12% and 15%. This reduction may theoretically increase up to 59–73% when cutting and trimming waste-optimized remanufacturing is combined with circular economy strategies based on the ideal recycling of CFRPs at end-of-life

Acid aging effects on surfaces of PTFE gaskets investigated by Fourier transform infrared spectroscopy

This paper investigates the effect of a prolonged acid and thermal attack, on the surface of PTFE by Fourier Transform Infrared Micro-Spectroscopy (\u3bcFT-IR). The materials are commercialized by two alternative producers in form of Teflon tapes. These tapes are installed in process plants where tires moulds are cleaned inside a multistage ultrasonic process. In these cases, Teflon tapes, having a role of gaskets, show inexplicably phenomena of degradation in relatively short operation periods. Even considering that these gaskets are exposed to the combined effect of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the possibility of these severe erosion phenomena. An interesting explanation can be related to the potential presence in the cleaning solution, mainly based on sulfamic acid, of highly reactive chemical compounds, as chlorides and fluorides, originated by the disaggregation of elements from the tire composition and/or additives used as processing aids and/or by catalytic effect generated by fluorine produced by PTFE degradation. In general, up to 300 different chemical elements, both organic and inorganic, natural and synthetic, are merged in a tire. Since this composition is practically unknown, especially regarding additives and \u201cunusual elements\u201d, representing a secrecy of each tire manufactures, it is really complex to define the chemical composition of the cleaning solution with an appropriate precision. As a consequence, the gaskets have been treated with different mixtures of acids in the way to combine a larger range of possibilities. Thus, the \u3bcFT-IR experimental characterization of PTFE surface properties followed an appropriate accelerated aging, aiming at actuating the specific mechanics of wearing as in industrial use. The different acid treatments adopted for accelerating the aging of gaskets have highlighted the different behaviour of the PTFE matrix, but also differences between manufacturers

Acid Aging Effects on Surfaces of PTFE Gaskets Investigated by Thermal Analysis

This paper investigates the effect of a prolonged acid attack on the surface of PTFE by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). PTFE is very non-reactive, partly because of the strength of carbon–fluorine bonds and for its high crystallinity, and, as a consequence, it is often used in containers and pipework with reactive and corrosive chemicals. The PTFE under analysis is commercialized by two alternative producers in form of Teflon tapes. These tapes are adopted, as gaskets, in process plants where tires moulds are cleaned by acid solutions inside a multistage ultrasonic process. In this case, PTFE shows, in a relatively short operation time, inexplicably phenomena of surface degradation, which could be related, in general terms, to an acid attack. But, even considering the combined effect of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the risk of the extreme erosion phenomena as observed. The present experimental research aim at investigating this contradiction. A possible explanation could be related to the presence in the cleaning solution of unexpected fluorides, able to produce fluorinating agents and, thus, degrade carbon-fluorine bonds. Considering more the 300 chemical elements a tire compound consists in, it is really complex to preserve the original chemical composition of the cleaning solution. In this research PTFE samples have been treated with different mixtures of acids with the aim at investigating the different aging effects. The thermal analysis has permitted the experimental characterization of PTFE surface properties after acid attack, providing evidence of the degradation phenomena. In particular, the different acid treatments adopted for accelerating the aging of gaskets have highlighted the different behaviour of the PTFE matrix, but also differences between manufacturers

Acid Aging Effects on Surfaces of PTFE Gaskets Investigated by Fourier Transform Infrared Spectroscopy

This paper investigates the effect of a prolonged acid and thermal attack, on the surface of PTFE by Fourier Transform Infrared Micro-Spectroscopy (FT-IR). The materials are commercialized by two alternative producers in form of Teflon tapes. These tapes are installed in process plants where tires moulds are cleaned inside a multistage ultrasonic process. In these cases, Teflon tapes, having a role of gaskets, show inexplicably phenomena of degradation in relatively short operation periods. Even considering that these gaskets are exposed to the combined effect of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the possibility of these severe erosion phenomena. An interesting explanation can be related to the potential presence in the cleaning solution, mainly based on sulfamic acid, of highly reactive chemical compounds, as chlorides and fluorides, originated by the disaggregation of elements from the tire composition and/or additives used as processing aids and/or by catalytic effect generated by fluorine produced by PTFE degradation. In general, up to 300 different chemical elements, both organic and inorganic, natural and synthetic, are merged in a tire. Since this composition is practically unknown, especially regarding additives and “unusual elements”, representing a secrecy of each tire manufactures, it is really complex to define the chemical composition of the cleaning solution with an appropriate precision. As a consequence, the gaskets have been treated with different mixtures of acids in the way to combine a larger range of possibilities. Thus, the FT-IR experimental characterization of PTFE surface properties followed an appropriate accelerated aging, aiming at actuating the specific mechanics of wearing as in industrial use. The different acid treatments adopted for accelerating the aging of gaskets have highlighted the different behaviour of the PTFE matrix, but also differences between manufacturers

Characterization of solid residues emerging during ultrasonic cleaning treatments of tyre moulds

The present paper aims at the investigation of the nature and possible origin of solid residues found in the washing basins of Ultrasonic Mould Cleaning System (UMCS) plants. In particular, analyses have been focused on the potential PTFE provenience of the debris and the eventual effect of acid solutions used in the process. Moreover, spring vents taken apart from tyre moulds subjected to repeated use and cleaning cycles, have been analysed in order to determine signs of wear, damage extent and its possible causes. Analyses have been performed by means of FT-IR, TGA, SEM-EDX and XRF, obtaining information on both organic and inorganic fractions. Results obtained seem to indicate that the degradation of PTFE is not responsible of the presence of these debris, and the acid solutions used in the process appear not to have a significant or direct role in the degradation and oxidation patterns

Safer plasticized polyvinyl chloride synthetic leathers for the automotive industry: Evaluation of alternatives to antimony compounds as flame retardants

Automotive interiors materials, like plasticized polyvinyl chloride (pPVC) synthetic leathers (SLs), require additives for improving their flame behavior. The preferred flame retardant (FR) used in pPVC is antimony trioxide (Sb 2 O 3 , ATO), though the use of antimony poses several issues, for both human health and the environment, related to its extraction, processing, and use. In order to investigate alternatives to ATO in high-performance pPVC SLs, various commercial FRs have been selected and tested in a typical, highly plasticized formulation. These additives have been used either alone or combined to evaluate synergistic effects. Samples have been tested to assess mechanical properties, thermal stability, and flame resistance. Data have been compared with those of neat pPVC and a foil with 2 phr of ATO. Several FRs are effective in improving the flame response compared with neat pPVC, without compromising the other properties, in detail calcium hypophosphite and mixtures containing zinc hydroxystannate (ZHS). Finally, aluminum hydroxide and ZHS (ATH + ZHS) yields the cheaper among the alternatives here proposed, even though higher than ATO (+193%) whose price/performance ratio is difficult to overcome. POLYM. ENG. SCI., 2019. \ua9 2019 Society of Plastics Engineers

Studio del comportamento di guarnizioni in teflon sottoposte a degradazione controllata mediante attacco acido e temperatura

Osservazioni condotte su impianti innovativi per la pulizia degli stampi utilizzati nella formatura dei pneumatici hanno messo in evidenza come le guarnizioni commerciali in teflon (PTFE) presentano un fenomeno di degrado imprevisto, non compatibile con le condizioni nominali di impiego e che lasciano intuire la presenza di fenomeni complessi. Si tratta di impianti che consentono la pulizia di stampi, quantunque complessi, attraverso la loro immersione in vasche di lavaggio e l\u2019azione combinata di ultrasuoni, prodotti chimici, temperatura ed agitazione del liquido. La sovrapposizione dei diversi effetti fisici e chimici crea una situazione di forte stress chimico-meccanico su tutta la struttura di impianto, compresi gli elementi di connessione e contenimento. Alcune fuoriuscite di liquido, osservate durante il funzionamento degli impianti anche dopo un periodo di funzionamento relativamente breve, hanno concentrato l\u2019attenzione sulle guarnizioni. Queste sono state appositamente sottoposte a degradazione controllata e successiva caratterizzazione sperimentale per investigare meglio la situazione. In particolare, questo studio descrive le condizioni di degradazione del teflon e riporta i risultati ottenuti mediante analisi spettroscopia infrarossa (FT-IR), calorimetria differenziale a scansione (DSC) e analisi termogravimetrica (TGA) in funzione del processo di degradazione Abstract This paper describes the accelerate aging tests used for investigating the surface alteration of PTFE gaskets commercialized by two alternative producers. These gaskets are installed in modern process plants where tires moulds are cleaned by a multistage ultrasonic process. Their surface degrades inexplicably under ordinary operative conditions after a relatively short period. Even if these gaskets are exposed to a combination of ultrasonic waves, temperature, humidity and acid attack, the PTFE properties of resistance nominally exclude the possibility of severe erosion phenomena as highlighted during the real utilization. A possible explanation could be represented by the presence of unexpected chemical compounds emerging from the disaggregation of highly reacting elements from the tire composition.. Thus, the experimental characterization of PTFE properties has to follow an appropriate accelerated aging, aiming at actuating the specific mechanics of wearing as in industrial use

Evaluation of carbon fibers structure and morphology after their recycling via pyro-gassification of CFRPs

The present work presents the evaluation of the performance of single carbon fibers after pyro-gassification treatment in different gasification conditions, i.e. 500\ub0C for 30' and 60', and 600\ub0C for 20', in order to evaluate the intrinsic fiber properties that might contribute to the overall composite behavior when re-impregnated with a polymeric matrix. Such investigation, carried with different analytic techniques such as Raman spectroscopy, XRD diffractometry, SEM Microscopy with EDX atimic mapping and finally mechanical tensile test carried out on single fibers, proves that convenient pyro-gassification conditions might lead to recovery of carbon fibers with properties not far from the pristine ones. While some further tuning of the gasification condition might still be required, 500\ub0C proved to be the optimal temperature for treatment, where the structure and morphology are practically untouched and mechanical properties are well comparable with pristine fibers in terms of Young's Modulus with just a slight drop in ultimate properties