Effect of continuous elongational flow on structure and properties of short glass fiber reinforced polyamide 6 composites

Short glass fiber (SGF) reinforced polyamide 6 (PA6) composite is an important thermoplastic engineering plastic with excellent properties such as high toughness, high strength, self-lubrication and corrosion resistance. However, due to the characteristics of difficult to disperse and easy to break of the fibers during processing, the application range of the PA6/SGF composite is limited. An innovative twin-eccentric rotor extruder (TERE), which can generate continuous elongation flow, is applied to fabricate the PA6/SGF composites in different fiber content and rotor speed. The fiber length remains good and the fibers are well dispersed in the polymer matrix so that the residual fibers after burn-off form a network interlock structure. That is, the TERE based on continuous elongational flow not only disperses the glass fibers effectively, but also reduces the fiber breakage. Under the action of elongation flow field, the fiber agglomerates undergo a periodic convergence-divergience effect, which forces the fiber agglomerates to separate from each other and disperse homogeneously in the polymer matrix. Interestingly, the charpy impact strength of the composites prepared by the TERE is about double that prepared by the twin-screw extruder (TSE) at each fiber content, which can be attributed to the more efficient fiber dispersion and longer fiber retention length. The thermal oxygen aging property, fatigue property, and creep property analysis also indicate that the TERE has a better dispersion effect than the TSE, and the fibers retain a longer length in the PA6 matrix, thereby providing more excellent service properties. Keywords: Polyamide 6, Short glass fiber, Twin-eccentric rotor extruder, Elongational flow field, Fiber length distribution