Optimization of the temperature program to scale up the stabilization of polyacrylonitrile fibers

Meinl, Juliane; Schönfeld, Katrin; Kirsten, Martin; Kittler, Karsten; Michaelis, Alexander; Cherif, Chokri

doi:10.1016/j.compositesa.2017.02.010

Cited by 17 publications

(23 citation statements)

References 19 publications

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“…The downtrend of T i in air atmosphere with the increase of pretreatment temperature and time shows a lower initial temperature of pretreated fibers than that of PAN fibers. It means that the pretreated fibers need lower temperature to induce chemical and/or physical changes during thermal stabilization in air than the PAN fibers need, which implies that thermal pretreatment of PAN fibers in nitrogen may promote the reactions during thermal stabilization in air [8,9,[27][28][29][30][31]. On the other hand, the uptrend of T i in nitrogen atmosphere implies that the thermal pretreatment in nitrogen had induced reactions or structural changes.…”

Section: Resultsmentioning

confidence: 99%

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Structural Transformation of Polyacrylonitrile (PAN) Fibers during Rapid Thermal Pretreatment in Nitrogen Atmosphere

et al. 2020

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The modification before the stabilization process could tune the exothermic behavior and the structural evolution of PAN fibers during stabilization. In this study, we demonstrate that a rapid thermal pretreatment in nitrogen can effectively mitigate the exothermic behavior of PAN fibers, such as decreasing the initial temperature, broadening the exothermal peak, and decreasing the nominal heat release during heating the fibers in air. The color of fibers has shown gradual changes from white to light yellow, yellow and brown during thermal pretreatment in nitrogen with the increase of pretreating temperature and time. The differential scanning calorimetry (DSC), Fourier Transform Infrared Spectrometer (FTIR), X-ray diffraction (XRD), and Thermogravimetric Analysis (TG) characterization have been applied to analyze the thermal properties, chemical and physical structural difference between PAN, and thermally pretreated PAN fibers. The thermal pretreatment of PAN fibers in nitrogen could induce cyclization, dehydrogenation, and cross-linking reactions, in which the cyclization play an important role on improving the cyclization index of stabilized PAN fibers. Meanwhile, the pretreatment can result in noticeable changes of the aggregation structure of PAN fibers, as indicated by the increase of crystallinity and crystalline size. These structural modifications can benefit the main cyclization reaction during stabilization and enhance the carbon yield in resultant carbon fibers. The rapid thermal pretreatment in nitrogen could increase efficiency of modification on PAN fibers, and that could save much time and energy. It is beneficial to manufacture low-cost carbon fibers and to spread the applications of carbon fibers.

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Section: Resultsmentioning

confidence: 99%

“…The stabilization is performed in a temperature of 200-300 • C [8,9,13,[29][30][31]. The maximum temperature during stabilization is typically close to the first exothermic peak temperature (T p1 ) of the DSC curve characterized in air at a heating rate of 5 • C/min.…”

Section: Resultsmentioning

confidence: 99%

Structural Transformation of Polyacrylonitrile (PAN) Fibers during Rapid Thermal Pretreatment in Nitrogen Atmosphere

et al. 2020

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“…The results of the thermal analysis in nitrogen atmosphere are presented in Appendix A (Figure A.3). The measured heat released is due to the exothermic, intra-and inter-molecular cyclization, the only occurring action under such conditions (since dehydration dehydrogenation and oxidation reactions are triggered by the presence of O2) [1,6,11,13,33,47,59,60].Confirmation that only a single event occurs is obtained by TGA (where a bending point is observed in DTG), while the DSC exotherm is accompanied by minor weight loss, a behavior characteristic of cyclization reactions [28]. The results of this analysis are presented in Table 4.…”

Section: Thermal Analysismentioning

confidence: 99%

Introduction of a Methodology to Enhance the Stabilization Process of PAN Fibers by Modeling and Advanced Characterization

Konstantopoulos

Soulis

Dragatogiannis

et al. 2020

Preprint

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A methodology is proposed for designing the stabilization process of polyacrylonitrile (PAN) fibers. In its core, this methodology is based on a model that describes the characteristic fiber length change during the treatment, through the de-convolution of the three main contributors (i.e. entropic shrinkage, creep, and chemical shrinkage). The model has the additional advantage of offering further insight into the physical and chemical phenomena taking place during the treatment. Validation of PAN-model prediction performance for different processing parameters was achieved as demonstrated by FTIR and DSC. Τensile testing revealed the effect of processing parameters on fiber quality, while model prediction demonstrated that ladder polymer formation is accelerated at temperatures over 200oC. Additionally, according the DSC and FTIR measurements predictions from the application of the model during stabilization seem to be more precise at high-temperature stabilization stages. It was shown that mechanical properties could be enhanced preferably by including a treatment step below 200oC, before the initiation of cyclization reactions. Further confirmation was provided via Raman spectroscopy, which demonstrated that graphitic like planes are formed upon stabilization above 200oC, and thus multistage stabilization is required to optimize synthesis of carbon fibers. Optical Microscopy proved that isothermal stabilization treatment did not severy alter the cross section geometry of PAN fiber monofilaments.

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“…As reações de estabilização da PAN ocorrem em temperaturas elevadas (180-400ºC), entretanto, as fibras acrílicas necessitam de uma taxa de aquecimento controlada, uma vez que as reações que ocorrem nesta etapa são muito sensíveis à temperatura (Meinl et al, 2017).…”

Section: Variáveis Que Influenciam No Processo De Estabilização Térmicaunclassified

“…A combinação de baixa massa específica e estabilidade mecânica origina um material ideal para aplicação de elevado desempenho. Essas propriedades vêm proporcionando o seu uso em diversas aplicações que lidam com configurações de baixa massa específica, eficiência energética e conscientização ambiental nas indústrias aeronáutica, nuclear, aeroespacial, e nas áreas de engenharia civil, naval, petróleo, automobilística, biomédica e esportiva (Meinl et al, 2017).…”

Section: Introductionunclassified

Caracterização da etapa de estabilização do processo produtivo de fibra de carbono a partir de poliacrilonitrila utilizando algoritmos inteligentes

Terra¹

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Terra, B. M. Caracterização da etapa de estabilização do processo produtivo de fibra de carbono a partir de poliacrilonitrila utilizando algoritmos inteligentes. 2021. 86 p. Dissertação (Mestrado em Tecnologia Nuclear) -Instituto de Pesquisas Energéticas e Nucleares-IPEN-CNEN/SP. São Paulo.Nos últimos anos, os materiais compósitos vêm expandindo, cada vez mais, sua aplicação em diversos segmentos, e em especial, os materiais compósitos poliméricos reforçados com fibra de carbono, demonstram ser um material estrutural de elevado desempenho que combina baixa massa específica e estabilidade mecânica. A produção de fibra de carbono, utilizando a poliacrilonitrila como precursor, possui diversas etapas em sequência: polimerização, fiação, estabilização térmica, carbonização e tratamento superficial. Em função da elevada duração e da importância das reações que ocorrem durante a estabilização, esta é considerada a etapa mais crítica do processo, na qual ocorre a formação do anéis aromáticos que influenciam diretamente na estrutura final da fibra de carbono e, consequentemente, na qualidade deste material. Visando otimizar o desenvolvimento deste material, bem como obter a redução do custo de produção, o presente trabalho realizou a modelagem computacional da etapa de estabilização térmica utilizando algoritmos inteligentes. Para obter o modelo, foi realizada uma prévia análise qualitativa utilizando as variáveis de processo e de qualidade dos materiais envolvidos na produção destas fibras. Esta análise inicial utilizou Mapas Auto-Organizáveis, a qual baseia-se em um treinamento não-supervisionado desta rede neural artificial. Posteriormente, foi utilizado treinamento supervisionado em uma rede neural feed-forward com retropropagação (backpropagation) para a análise quantitativa. A partir destas análises, foi possível simular a etapa de estabilização térmica de uma planta, em escala laboratorial, de produção de fibra de carbono, obtendo-se resultados com erros relativos de 2,98±0,01% e 2,48±0,02% para os parâmetros de Densidade Volumétrica e do Índice de Conversão por Espectrometria por Infravermelho com Transformada de Fourier (FTIR), quando comparados com os resultados experimentais.

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Optimization of the temperature program to scale up the stabilization of polyacrylonitrile fibers

Cited by 17 publications

References 19 publications

Structural Transformation of Polyacrylonitrile (PAN) Fibers during Rapid Thermal Pretreatment in Nitrogen Atmosphere

Structural Transformation of Polyacrylonitrile (PAN) Fibers during Rapid Thermal Pretreatment in Nitrogen Atmosphere

Introduction of a Methodology to Enhance the Stabilization Process of PAN Fibers by Modeling and Advanced Characterization

Caracterização da etapa de estabilização do processo produtivo de fibra de carbono a partir de poliacrilonitrila utilizando algoritmos inteligentes

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