Upcycling of HDPE Milk Bottles into High-Stiffness, High-HDT Composites with Pineapple Leaf Waste Materials.

In the pursuit of sustainability and reduced dependence on new plastic materials, this study explores the upcycling potential of high-density polyethylene (HDPE) milk bottles into high-stiffness, high-heat-distortion-temperature (HDT) composites. Recycled high-density polyethylene (rHDPE) sourced from used milk bottles serves as the composite matrix, while reinforcing fillers are derived from dried pineapple leaves, comprising fibers (PALF) and non-fibrous materials (NFM). A two-roll mixer is employed to prepare rHDPE/NFM and rHDPE/PALF mixtures, facilitating filler alignment in the resulting prepreg. The prepreg is subsequently stacked and pressed into composite sheets. The introduction of PALF as a reinforcing filler significantly enhances the flexural strength and modulus of the rHDPE composite. A 20 wt.% PALF content yields a remarkable 162% increase in flexural strength and a 204% increase in modulus compared to neat rHDPE. The rHDPE/NFM composite also shows improved mechanical properties, albeit to a lesser degree than fiber reinforcement. Both composites exhibit a slight reduction in impact resistance. Notably, the addition of NFM or PALF substantially elevates HDT, raising the HDT values of the composites to approximately 84 °C and 108 °C, respectively, in contrast to the 71 °C HDT of neat rHDPE. Furthermore, the overall properties of both the composites are further enhanced by improving their compatibility through maleic anhydride-modified polyethylene (MAPE) use. Impact fracture surfaces of both composites reveal higher compatibility and clear alignment of NFM and PALF fillers, underscoring the enhanced performance and environmental friendliness of composites produced from recycled plastics reinforced with pineapple leaf waste fillers.

Achieving High-Performance Green Composites from Pineapple Leaf Fiber-Poly(butylene succinate) through Both Fiber Alignment and Matrix Orientation across the Thickness.

This research aims to develop high-performance and low-carbon composites using biobased poly(butylene succinate) (PBS) reinforced with well-aligned pineapple leaf fibers (PALF). PBS/PALF composites containing 10 and 20% PALF by weight (wt %) were prepared using a two-roll mill. During the mixing process, the molten material was slightly stretched to align the fibers in the machine direction, forming a uniaxial prepreg. The prepreg was subsequently stacked and compressed into composite sheets at compression temperatures of 120 and 140 °C. Differential scanning calorimetry, X-ray diffraction, and crystalline morphology analysis revealed the presence of matrix orientation in the prepreg, which was preserved in sheets compressed at 120 °C but not at 140 °C. The composites prepared at 120 °C exhibited significantly higher flexural strength and modulus compared to those prepared at 140 °C, attributed to the combined effect of matrix and PALF orientation. Additionally, the composites displayed an increase in heat distortion temperature, with a maximum of 10 °C higher than the matrix melting temperature (∼113 °C) for the composite with 20 wt % PALF. These findings indicate the potential for increased utilization of this low-carbon green composite.

Comparative Study of Flax and Pineapple Leaf Fiber Reinforced Poly(butylene succinate): Effect of Fiber Content on Mechanical Properties.

In this study, we compare the reinforcing efficiency of pineapple leaf fiber (PALF) and cultivated flax fiber in unidirectional poly(butylene succinate) composites. Flax, known for robust mechanical properties, is contrasted with PALF, a less studied but potentially sustainable alternative. Short fibers (6 mm) were incorporated at 10 and 20% wt. levels. After two-roll mill mixing, uniaxially aligned prepreg sheets were compression molded into composites. At 10 wt.%, PALF and flax exhibited virtually the same stress-strain curve. Interestingly, PALF excelled at 20 wt.%, defying its inherently lower tensile properties compared to flax. PALF/PBS reached 70.7 MPa flexural strength, 2.0 GPa flexural modulus, and 107.3 °C heat distortion temperature. Comparable values for flax/PBS were 57.8 MPa, 1.7 GPa, and 103.7 °C. X-ray pole figures indicated similar matrix orientations in both composites. An analysis of extracted fibers revealed differences in breakage behavior. This study highlights the potential of PALF as a sustainable reinforcement option. Encouraging the use of PALF in high-performance bio-composites aligns with environmental goals.