Manufacture and Characterization of Recycled Polypropylene and Olive Pits Biocomposites

Abstract

The present work studies the use of olive pit (OP) as a reinforcement in the manufacture of composites based on a post-consumer recycled polypropylene (rPP). In this way, it is feasible to provide added value from olive pits, a by-product resulting from the olive industry operations, while promoting the circular economy and reducing the use of fossil-based polymers. For this purpose, suitable samples were manufactured using 25 wt% and 40 wt% of OP. Additionally, the effect of incorporating additives was studied: (a) a process control additive (PA), and (b) a coupling agent of maleic anhydride grafted polypropylene (MAPP). The results showed an improvement in Young’s and flexural modulus with the OP addition. The incorporation of PA did not present any significant improvement in the properties of the materials, nevertheless it facilitated the biocomposite manufacturing process. As for the coupling agent, it significantly improved the mechanical properties, achieving the best results with the addition of the two types of additives and 40 wt% of OP. Moreover, the thermal properties were maintained, and there was an increase in crystallinity in all composites compared to rPP. According to the results of the fracture surface analysis, the coupling agent improves reinforcement-polymer matrix cohesion.

Sustainable Polypropylene-Based Composites with Agro-Waste Fillers: Thermal, Morphological, Mechanical Properties and Dimensional Stability

“…However, their crystalline content increased and was directly correlated with the amount of filler, regardless of its type, rising by 23% and 41% for PPrh and 23% and 40% for PPop. These findings corroborate the data reported in the literature [4,23], attributing the rise in crystal content to the interaction between the filler and PP matrix, promoting the nucleation of PP crystals around the rice husk and olive pit particles. A higher crystallinity indicates material stiffness [37], suggesting that all the tested composites possessed a higher elastic modulus and decreased ductility.…”

“…The DSC analysis involved stabilizing each sample at 20 • C, followed by heating it up to 190 • C and then cooling it back to 20 • C at a rate of 10 • C/min. The degree of crystallinity (χ) for each sample was calculated using Equation (2) [23]:…”

“…In addition, significant research has been dedicated to precisely defining the natural filler content for maximum improvements in NFC mechanical properties. The common ground is an improvement in the elastic mechanical properties, i.e., a higher stiffness at the expense of significant ductility loss due to the insufficient wetting of the fibers by the polymer matrix [2,3,14,[19][20][21][22][23].…”

Manufacture and characterisation of polylactic acid biocomposites with high-purity cellulose isolated from olive pruning waste

“…BYK MAX-P 4101 (BYK-Chemie GmbH, Germany) was also used as process additive (PA) in order to improve the processability of the mixture and the distribution of the fibres into the polymer matrix. 34 Prior to preparing the biocomposites, moisture was removed from both the treated (OTPBH 2 ) and the non-treated OTP, drying them in an oven for 24 h at 60°C that was sufficient to reach constant weight. PLA pellets were dried in a KKT 75 dryer (KOCH, Germany) under the following conditions: 45°C for 5 h. The biocomposites were manufactured using two different percentages of OTP, 5 and 15% by weight.…”

Feasibility of Cherry Pit Particles as a Natural Reinforcement in Polypropylene

“…Another work on olive pits incorporating compatibilizer found similar results to the study mentioned above, but showing some beneficial effects of the compatibilizer. In that case, a recycled polypropylene was used as the matrix, and adding the compatibilizer showed a positive effect on the unreinforced polypropylene [17]. Therefore, the question remains if a compatibilizer would also improve the composite properties for cherry pits.…”