Wood fiber of aspen was used as a reinforced filler in linear low-density polyethylene (LLDPE). To improve the compatibility between the wood fiber and the LLDPE matrix, the wood fiber was treated with titanate coupling agents (i.e., TC-PBT and TC-POT) or grafted by acrylonitrile. Both treatments resulted in an improvement in the mechanical properties of the resultant composites compared with the composites filled with the untreated wood fiber. Moreover, the grafting method displayed a more obvious benefit than that of titanate coupling methods to the mechanical property improvement. This was attributed to the crystalline structure of the wood fiber to be destroyed by grafting acrylonitrile, and the amorphous fiber was easily deformed to enhance fiber adhesion at the LLDPE matrix. In addition, the effect of the concentration of the filled wood fiber and the amount of coupling agent or grafting ratio on the mechanical properties of composites are discussed.

Polypropylene(PP) and polyamide6(PA6) were extruded with a single screw extruder. It was found that when PA6 was in the dispersed phase, it could deform and fibrillate in the PP matrix in the shear force field generated by the rotating screw. Dynamic mechanical analysis and mechanical tests showed that the mechanical properties, such as the tensile strength, impact strength, and modulus, were different in the different processing directions. With the addition of PP‐g‐MAH as a compatibilzer, the number of fibrils decreased and the dimension of the dispersed phase decreased significantly. This indicated that the compatibility has a strong effect on the in‐situ fibrillation.

ABSTRACT:The in situ composite consisting of polypropylene (PP) and polyamide 6 (PA6) was obtained with extrusion method in a single screw extruder. It was found that P A6 being the dispersed phase could fibrillated in PP matrix and fibrillation occurred in the channel of the extruder. The notched impact strength increased with the increasing content of PA6 while the tensile strength decrease. The average diameter of the fibrils chai:tged hardly with the changing content of PA6 under the investigated condition. Increasing the draw rate and the impact strength and tensile strength increased obviously. When increasing the rotating speed of screw the dimension of the fibrils also became finer. The mechanical properties decreased with the increasing processing temperature and the average diameter of fibrils increased.KEY WORDS In Situ Fibrillation Composite/ Polypropylene/ Polyamide 6 /Thermoplastic/ Processing Condition/ When a suspension of fluid droplets is subjected to flow, it tend to be deformed and oriented along the flow direction. For two incompatible polymers when the effect of viscous force is larger than that of the interfacial tension, the dispersed phase in flowing blend can form ellipsoids, rods, or fibrils under different viscosity ratio of two components. 1 The well-known example is the system of liquid crystalline polymer (LCP) and thermoplastic where the dispersed phase is LCP with rigid molecular chain. Many papers had reported the formation of LCP/polymer in situ composites,2 and their mechanical properties, rheological property, and so on had been discussed in these papers. 3 • 4 For two flexible thermoplastics the dispersed phase can form fibrils in matrix although these fibrils will relax and retract easily because of its flexibility of molecular chain. If the melting temperature of dispersed-phase-formed fibrils is higher than that of the matrix and the composite is molded below the Tm of fibrils, in situ composite with the fibrils is obtained.To generate the fibrillar morphology three major methods have been used: fiber spinning, extrusion, and injection molding. It has been found that fiber spinning is particularly advantageous because the elongational force field in the spinning process is more effective for producing the fibrillar morphology than the shear force field. Polypropylene (PP)/polyamide 6 (PA6) in situ composite obtained with spinning process had been studied in some papers. 5 • 6 Under spinning condition both PP and PA6 could form fibers in the composite. It had not been reported that PP/PA6 in situ composite was obtained under ordinary extrusion processing condition. In the present study, PP/PA6 in situ composite was obtained with a single screw extruder. In this paper it was studied that how the composition and processing conditions influenced the morphology and mechanical properties of the composite.1 Supported by the National Science Foundation of Guangdong Province. tt Corresponding author. EXPERIMENTAL MaterialsBoth PA6 and PP are commercially available. PA6 is the pro...