Production and Characterisation of the Physical and Mechanical Properties of Recycled PP Fibers
This chapter explored the industrial feasibility of using melt spinning and hot drawing process to produce PP fibre under factory conditions instead of laboratory conditions. Virgin PP fibres of high tensile strength and Young’s modulus have been successf
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Production and Characterisation of the Physical and Mechanical Properties of Recycled PP Fibers
This chapter explored the industrial feasibility of using melt spinning and hot drawing process to produce PP fibre under factory conditions instead of laboratory conditions. Virgin PP fibres of high tensile strength and Young’s modulus have been successfully produced by this method. However, the production of recycled plastics with sufficient mechanical properties is still a major challenge due to degradation during their service history and heat processing stages. The aim of this chapter is to improve the tensile strength and Young’s modulus of fibres from recycled PP produced through the melt spinning and hot drawing process, and establish a relationship between mechanical properties of PP fibres with their crystallinity, crystal structure and orientation. Besides 100% recycled PP fibre, 50% of virgin PP and 5% of HDPE were mixed into the recycled PP fibre to produce 50:50 virgin-recycled PP fibre and 5:95 HDPE-recycled PP fibre, respectively. The mechanical properties of these recycled fibres produced by the melt spinning and hot drawing process were presented and compared with the virgin PP fibre. The effects of 50% of virgin PP and 5% of HDPE on fibre from recycled PP were studied in terms of crystal structure and crystallinity by differential scanning calorimetry (DSC) and wide-angle X-ray scattering (WAXS).
3.1 3.1.1
Fibre Production and Measurement Raw Materials for Fibre Production
Raw materials for producing virgin PP, recycled PP and HDPE used in this study are commercial grade granules. Their characteristics given in the manufacturer specifications are presented in Table 3.1 (LyondellBasell 2013; Martogg 2013; PTTPM 2013).
© Springer Nature Singapore Pte Ltd. 2017 S. Yin, Development of Recycled Polypropylene Plastic Fibres to Reinforce Concrete, Springer Theses, DOI 10.1007/978-981-10-3719-1_3
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Table 3.1 Characteristics of raw materials of plastic fibres Raw material
Virgin PP granule
Recycled PP granule
HDPE granule
Density (g/cm3) Melt flow index (MFI, 2.16 kg, dg/min) Tensile stress at yield (MPa) Flexural modulus (GPa) Notched izod impact strength (23 °C, type 1, Notch A, kJ/m2)
0.90 3.5 (at 230 °C)
0.90–0.92 13 (at 230 °C)
0.957 0.4 (at 190 °C)
31 1.25 4.7
35 1.48 3.5
31.4 0.8 5.8
3.1.2
Preparation of PP Fibres
As shown in Fig. 3.1, the plastic granules were fed into a single-screw extruder and melted. Temperatures of five heating zones of the extruder were set at 218, 223, 225, 233 and 235 °C. Fibres were then extruded into a water bath from the nozzle at the tip of the extruder. The extruded fibers are pulled to a chill roll and hot-drawn in the ovens at 120–150 °C. The resulting fibres through the second chill roll were smooth and had a circular cross-section of around 0.9 mm2. An indented roller die was used to mark indents on the fibres, in order to increase the bonding strength between the fibres and concrete. After inden
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