No abstract

Chopping is an efficient way to produce short carbon fiber (CF). Generally, there are two types of fixing constraints available in the chopping process: rigid-fixing and flexible-fixing. Simplified experiments were performed using glass and rubber as the fixing constraints in cutting a single polyacrylonitrile-based CF to reveal the influence of the fixing constraints in CF chopping. The cutting forces and the bending angles with different fixing constraints were analyzed. Furthermore, the failure surface of the CF was observed. Due to an additional bending effect in the flexible-fixing cutting, the failure surface of the CF was rough, and the cutting-off force was approximately 5% of the force in rigid-fixing cutting. Therefore, flexible-fixing cutting is a suitable way to decrease the cutting-off force in CF chopping. Moreover, it was concluded that the fiber fracture in rigid-fixing cutting is caused by compression, whereas in flexible-fixing cutting, it results from bending. We hope our work is beneficial to the design of the chopping procedure for short CF.

No abstract

No abstract

No abstract

The diversity-oriented synthesis of 2,4,6-trisubstituted pyridines via K2CO3-promoted multicomponent reactions of the β-nitrostyrenes, available substituted salicylic aldehydes and ammonium acetate have been developed.

Short carbon fiber (short-CF) has been extensively used as enforcement in composites or conductors in fibrous network materials, owing to its good subsequent processing compatibility with routine manufacturing technologies. Conventionally, short-CFs were made by cutting continuous CF-tows from thousands of meters into several millimeters length scale using a radial chopping technology, mainly through sizing, drying and chopping processes in sequence. In this work, four kinds of CF-tows with different physical properties were chopped to study the effect of a sizing agent on the production of short-CFs, including product morphology and yield ratio. All experiments were conducted on polyacrylonitrile-based CFs sized by polyurethane (PU)-acetone solution. Results show that the uniformity (an important index of short-CF appearance) of short-CFs is closely related to the unit sizing weight. The yield ratio is affected by the relative sizing amount of PU coated on CF-tows. In addition, a raw CF-tow with little fiber hairiness is beneficial to increase the yield ratio of short-CFs.

No abstract