Uniaxial Rotational Molding of Bio-Based Low-Density Polyethylene Filled with Black Tea Waste

Abstract

In this paper, the possibility of obtaining uniaxially rotomolded composite parts was discussed. The used matrix was bio-based low-density polyethylene (bioLDPE) filled with black tea waste (BTW) to prevent the thermooxidation of samples during processing. In rotational molding technology, the material is held at an elevated temperature in a molten state for a relatively long time, which can result in polymer oxidation. The Fourier transform infrared spectroscopy (FTIR) shows that adding 10 wt% of black tea waste has not led to the formation of carbonyl compounds in polyethylene, and adding 5 wt% and above prevents the appearance of the C–O stretching band connected with degradation of LDPE. The rheological analysis proved the stabilizing effect of black tea waste on the polyethylene matrix. The same temperature conditions of rotational molding did not change the chemical composition of black tea but slightly influenced the antioxidant activity of methanolic extracts; the detected changes suggest degradation is a color change, and the total color change parameter (ΔE) is 25. The oxidation level of unstabilized polyethylene measured using the carbonyl index exceeds 1.5 and gradually decreases with the addition of BTW. The BTW filler did not influence the melting properties of bioLDPE; the melting and crystallization temperature remained stable. The addition of BTW deteriorates the composite mechanical performance, including Young modulus and tensile strength, compared to the neat bioLDPE.

Recent Advancements towards Sustainability in Rotomoulding

“…All publications are within the past 5 years. Natural fillers such as black tea, giant reed, wood, hemp and rice were amongst findings accompanied by the experimental work with recycled carbon fibres [ 30 , 31 , 32 , 33 , 34 , 67 ]. Abhilash et al [ 34 ] reported that the addition of risk husk improved the vibrational properties from an experimental modal analysis (EMA), alluding to suitability for automobile vibrating applications by up to 15 wt% addition.…”

“…Aniśko and Barczewski studied bio-based PE and black tea waste from a tea distribution company [ 67 ]. Black tea would otherwise have been removed to landfill.…”

“…Black tea would otherwise have been removed to landfill. However, the tea was of interest due to the antioxidant activity it can provide with catechin extracts; the theaflavins and thearubigins still present in spent tea are able to scavenge radicals and protect the polymer chains [ 67 ]. Black tea was found to reduce the carbonyl index (a measurement of the extent of induced oxidation during processing) compared to neat PE.…”

“…Despite this improvement, further findings from Aniśko and Barczewski included that mechanical strengths were said to have a ‘downward trend’ with increasing filler content. The Young’s modulus decreased by nearly four times at 10 wt% of black tea, for example [ 67 ]. In addition, some studies assessed the blending of natural fibres with, specifically, bio-based materials such as PLA/PE in this area.…”

Effect of Cellulose-Based Bioplastics on Current LDPE Recycling

“…However, the presence of CAT in the blend causes a sharp reduction in maximum elongation at break, decreasing to 27% at 1 wt% CAT and only 8% at 10 wt% CAT. The stiffness of the blend increases proportionally to the amount of CAT present, with a maximum increase in the tensile modulus of 37% at 10 wt% CAT with respect to neat LDPE [ 44 , 45 ]. Nevertheless, yield strength and strain are not improved, showing no change at 1 wt% CAT, and a 17% reduction at higher CAT content.…”