The change of the outer layer of the hottest fiber

2022-08-07
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Restriction of fiber outer layer transformation on non isothermal curing and fusion operation of new type fiber compounding device. After the reaction, take out the kevar fiber sample after reaction, put it into Soxhlet extractor, extract it with formic acid for 24h, wash it with distilled water, extract it to neutral, and dry it in vacuum to constant weight to obtain kf0a and kf1

preparation of composite material samples: dry PA6 under 80, mix pa6/kf with KF to form a pa6/kf mixture with a weight percentage of 90/10, and mix it evenly with a high-speed kneader. It is extruded on sj3025 single screw extruder, the length diameter ratio of screw is 25, the four-stage extrusion processing temperature of PA6 is 230250255250, the processing temperature of pa6/kf composite is 224239253245, and the extrudate is water-cooled granulation

non isothermal differential scanning calorimetry analysis (DSC) American dupontsdtq600 differential scanning calorimetry analyzer. The temperature and enthalpy are calibrated with metal indium standard samples. In the development of materials for the testing of various physical and mechanical properties of plastic film, rubber, wire and cable, steel, glass fiber and other materials in nitrogen atmosphere, the room temperature is increased from 80/min to 250 and maintained for 8min to eliminate the thermal history, and then 5/min, 10/min, The bending and compression test machine of plexiglass materials analyzed the crystallization at the cooling rate of 15/min and 20/min, cooled to 50 for 8min, and finally heated to 250 at 20/min. The melting behavior of non isothermal crystallization samples at different temperatures was observed, including pure PA6, pa6/kf0 and pa6/kf1

results and discussion: non isothermal crystallization behavior under non isothermal conditions, the initial crystallization temperature tconset and the total crystallization time ttotal depend on the nucleation ability and cooling rate of the samples. The introduction of nucleating agent can improve tconset, while ttotal reflects the nucleation rate and growth rate of crystal. The relationship between tconset and cooling rate and the relationship between total crystallization time and cooling rate were drawn. The effects of KF addition and its surface grafting modification on tconset and ttotal were studied

when the cooling rate is the same, the initial crystallization temperature of pa6/kf is higher than that of pure PA6, indicating that the addition of KF has nucleation effect; However, after surface grafting modification, the initial crystallization temperature of KF is lower than that of unmodified KF, mainly because PA6 with the same properties as the matrix PA6 is grafted at the interface of pa6/kf1 composite, which is easier to be enriched on the fiber surface after melting, and has better wetting ability and stronger bonding with the fiber, so that the movement of the matrix PA6 macromolecular chain is constrained to a certain extent, As a result, the nucleation of PA6 in the crystallization process is not as great as that of pa6/kf0 composites. With the increase of cooling rate, the initial crystallization temperature of each sample showed a downward trend. It is the relationship between total crystallization time and cooling rate. It can be seen from the figure that when the cooling rate is the same, the addition of KF reduces the total crystallization time, which also indicates that the addition of fiber promotes crystallization

non isothermal melting behavior the multiple melting phenomenon of polymer is due to the existence of structures with different thermal and mechanical stability. This paper focuses on the melting behavior of non isothermal crystallization at different temperatures. When the cooling rate is 5/min, PA6 shows a single melting peak of about 218, which mainly corresponds to the crystal melting. With the increase of cooling rate, it shows double melting behavior. The positions of high-temperature peaks are basically about 221, while the melting peak temperature of low-temperature peaks gradually decreases, and the relative strength of the peaks also weakens, basically corresponding to the metastable crystal form. The above phenomenon is mainly because the non isothermal crystallization and melting behavior is the common result of recrystallization behavior and crystallization and melting of different crystal forms. With the increase of cooling rate, the movement of PA6 macromolecular chain is blocked to form metastable crystal forms. At the same time, some metastable crystals recrystallize and recombine to form stable crystal forms during the heating process. And reflect the non isothermal crystallization and melting behavior of pa6/kf. It can be seen that pa6/kf0 shows an asymmetric single peak when the cooling rate is 5/min, with the main peak at about 215 and the shoulder peak at about 220

with the increase of cooling rate, it shows double melting behavior. The positions of high temperature peaks are basically around 220, while the melting peak temperature of low temperature peaks gradually decreases, and the relative strength of the peaks also decreases, corresponding to the metastable crystal form. However, the melting temperature and relative strength of the low-temperature peak according to the newly released technology roadmap for energy saving and new energy vehicles are higher than those of pure PA6, which indicates that the addition of KF plays a role in nucleation and improves the perfection of crystallization. The melting behavior of non isothermal crystallization of pa6/kf1 is basically similar to that of pa6/kf0, and the effect of anionic grafting of PA6 on KF surface is not obvious

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