Polyamide‐6 composites reinforced with cellulose fibers and fabricated by extrusion: Effect of fiber bleaching on mechanical properties and stability

Abstract

We prepared polyamide-6 (PA-6) composites using bleached and semibleached cellulose fibers from Eucalyptus species by processing in a corotating interpenetrating twin-screw extruder. PA-6 is a challenging matrix because of its high processing temperature, which overlaps the thermodegradation temperature of the fibers. The selection of the processing conditions for extrusion and the use of the lubricant ethylene bis (stearamide) permitted the production of composites with 20, 30, and 40 wt% of bleached fibers, which are lighter than the corresponding glass fiber composites. Composites with 30 wt% of bleached fibers yield the best mechanical properties and good fiber/matrix interaction, as demonstrated by mechanical tests and scanning electron microscopy. X-ray photoelectron spectroscopy studies showed that the natural moisture in the fibers promotes the fiber/matrix interaction through the formation of ester bonds. We assessed the effect caused by the presence of lignin in the fibers. Composites containing 30 wt% of semibleached fibers maintained the flexural properties and showed small improvements in thermal stability when compared with bleached fiber composites; however, there is a slight decrease in the tensile properties. Through accelerated aging tests, we observed that increased lignin concentration in the fibers reduced the formation of carbonyl compounds on sample surfaces, indicating a stabilization effect. POLYM. COMPOS., 00:000-000, 2015.

Direct use of Brazilian banknotes residue for the production of reinforced composites based on low‐density polyethylene

“…The third decomposition stage attributed to lignin is observed from 390 to 445 °C. The thermal characterization of the fibers is in accordance with some results reported in the literature for cellulose‐based fibers . Besides the characteristic decomposition stages of the fibers components, there is also a fourth decomposition stage from 450 to 500 °C that might be attributed to other components, probably the resin used to confer a hydrophobic character (water resistance) to the banknotes.…”

Presence of iron in polymers extruded with corrosive contaminants or abrasive fillers

“…Composites reinforced with cellulose fibers were processed and obtained as described in previous works: PP [14] , HDPE [15] and PA-6 [16] .…”

High‐density green polyethylene biocomposite reinforced with cellulose fibers and using lignin as antioxidant

“…Figure shows the TGA curves for pure processed HDPE and composites and their first derivative at the 280–380 °C range. Previous works show that cellulose fibers have a well‐defined T onset , under the same conditions, at ∼300 °C . The initial process of mass loss for the composites (i.e., the region from 240 to 380 °C in Figure ) occurs under the influence of fiber content: the higher the amount of fibers, the lower the temperature at which the mass loss occurs.…”

“…Cellulose fibers were previously used as a reinforcement for polypropylene in concentrations in the range of 20–40 wt % . More recently, cellulose fibers with a residual amount of lignin showed simultaneous reinforcement and stabilization effects for polypropylene and similar results were found for cellulose fiber reinforced polyamide‐6 . Additionally, pure lignin also acted as a primary antioxidant for polypropylene in accelerated aging experiments …”