Laser diode sensors for measuring mechanical properties of recycled plastics

Abstract

Uncertainty of mechanical properties is one of obstacles in the use of recycled plastic as raw materials. This paper presents a method for measuring mechanical properties of plastic products that are partially made of recycled plastic. Specifically, the plastic type of interest in this project is Polypropylene. The proposed method employs an analysis through a relationship between optical transmittance and tensile strength, which varies with recycled compositions. Adopted from spectroscopy technique, laser diode sensor was used to measure optical transmittance. The sensor is composed of a 1550 nm laser diode as a light source and a photodiode as a detector. Experimental results from laser sensing method are equivalent to results from spectrometry. Optical transmittance, as well as tensile strength, linearly increases with the ratio of recycled plastic. Statistically, every linear function has the coefficient of determination (R 2 ) over 0.95. Thus, the mathematical relationships between optical transmittance and tensile strength were generated. In conclusions, the tensile strength of plastic with different percentages of recycled mixture can be measured by the use of the demonstrated laser diode sensor.

Using infrared spectroscopy analysis of plastic debris to introduce concepts of interaction of electromagnetic radiation with matter

“…Mean transmittance values of 95% ± 5% (transparent), 90% ± 5% (blue) and 65% ± 5% (green) were obtained. The results are comparable with those observed in [10]. In order to evaluate the transmittance variation with polymer type, we have used 1.5 mm thick transparent plastic debris and mean values of 95% ± 5% (PP), 85 ± 7 (PE), and 66% ± 7% (PS) were obtained.…”

“…These systems use laser diodes (LD) or infrared LEDs as sources of monochromatic infrared light (only one-wavelength radiation). According to [10], the plastics from household wastes (such as PE, PP, PVC, PS and PET) can be reliably identified by the first overtone of the C-H bands (near to 1.7 µm), technical non-black plastics around 1.0 µm, and black plastics only in the MIR region.…”

“…This finding is consistent with Niteroi's social and March 2020 industrial habits (figure 5): the sampled plastic debris comes mainly from household waste. In order to test the effectiveness of a lowcost optical transmittance sensor that can be used in the classroom activities, we built a onedimensional optical transmittance sensor system (figure 11(a)), following the technical information from the [8][9][10]. Its estimated cost is around US$ 3000, while a MIRS system costs around US$ 50 000.…”