Effects of Processing Variables of Extrusion–Pultrusion Method on the Impregnation Quality of Thermoplastic Composite Filaments

Abstract

Carbon fibre-reinforced polypropylene composite filaments were fabricated via the extrusion–pultrusion method. One of the important factors influencing composites’ filament processability and structural properties is the impregnation quality, which can be represented by interfacial adhesion between the matrix and fibre. To improve the interfacial shear strength (IFSS) of the filament, four processing variables—melt temperature, pulling speed, number of pins in the impregnation die and fibre treatment—have been optimised using the Box–Behnken response surface methodology (RSM). Analysis of variance (ANOVA) was conducted to evaluate the linearity of the response surface models. Three levels were set for each independent variable. The melt temperature was varied at levels 190, 210 and 230 °C, while the pulling speed was set at three levels, namely, 40, 47 and 50 cm/min. The number of spreader pins was varied at 1, 2 and 3 pins, and there were three variations of the fibre treatment, namely, vinyltrimethoxysilane (VTMS), γ-aminopropyltriethoxy silane (APTS) and liquid nitrogen. Twenty-seven experimental runs were conducted, and a significant regression for the coefficient between the variables was obtained. The filament IFSS was measured by a customised pull-out test, and its surface morphology was characterised using a scanning electron microscope. ANOVA showed that fibre treatment significantly affected the IFSS due to their surface roughness, followed by pulling speed and melt temperature in quadratic order. Liquid nitrogen is recommended for carbon fibre treatment because of the high surface roughness, thereby providing a better matrix–fibre bonding effect. The results demonstrated that a melt temperature of 190 °C, pulling speed of 40 cm/min, three spreader pins and treatment of the fibre with liquid nitrogen afforded the optimum impregnation quality. It is important to keep a reasonable low processing temperature to obtain the geometrical stability of the product.

Temperature Profile Measurement Using Modified Cooled Stainless Tube Technique in a Single Screw Extruder Coupled With a Modified Thermocouple Mesh – Effect of Screw Speed

“…The experimental results are listed as in Table 2 below. [13,14,15]. The radial temperature fluctuations at various screw speeds are as shown in Figure 4.…”

Cost-efficient, automated, and sustainable composite profile manufacture: A review of the state of the art, innovations, and future of pultrusion technologies

“…Fibre-surface treatment is another commonly used application for fibre-reinforced polymers to enhance impregnation by capillary effects [87] and mechanical performance by improved fibre-matrix bonding [88]. Some of the surface treatment methods that have been applied with positive outcomes for pultrusion are coupling agent treatments [89], liquid nitrogen treatments [90], and corona discharge treatments [91]. Whereas some of these fibre-surface treatment methods should be done before the pultrusion process, corona discharge treatment, for example, can also be performed continuously in the pultrusion line.…”

Manufacturing and Analysis of Overmolded Hybrid Fiber Polyamide 6 Composite

“…This treatment aimed to increase the surface roughness of fibers so that the mechanical interlocking between the matrix and fibers can be increased. Immersing carbon fiber in liquid nitrogen for 10 min has been proven to produce better fiber-matrix adhesion of CFRP than silane coupling agents [16]. A FANUC ROBOSHOT -S-2000i100A injection machine with a clamping capacity of 100 tons was used to produce overmolding specimen A. PA 6-GF pellet was fed through the hopper of the injection molding machine, plasticized, and transported to the nozzle.…”