| 🧪 What does the paper actually show? |
| Claim: Composites reinforced with palm oil production waste |
| Fields of application: Low-density polyethylene waste |
Introduction
Scientists have developed a way to recycle polymer films, which are often used only for packaging and almost immediately become waste because of their short lifespan. Polymer films are often made of low-density polyethylene (LDPE), which can be reinforced to improve their mechanical performance.
The paper analyzed how byproducts of palm oil production can be used to prepare natural fibers (NF), cellulose (CEL), and cellulose nanofibrils (CNF), which were added to low-density polyethylene waste through thermomechanical processes to produce various composites.
Producing these composites is an excellent recycling alternative that can help reduce the environmental damage caused by this waste and create new sustainable products.
A New Scientific Approach
The production of composites reinforced with lignocellulosic materials is a strategic approach that supports sustainability, waste utilization, and improved properties in recycled materials.
In Brazil’s Amazon region, oil production generates large amounts of agricultural waste from empty fruit bunches and husk fibers. This biomass is rich in cellulose and can be used in the form of natural fibers, purified cellulose, or nanocellulose.
Cellulose-based materials are hydrophilic, meaning they have an affinity for water, unlike most polymers, such as low-density polyethylene, which is hydrophobic. Therefore, it was necessary to improve the interaction between these two components through chemical treatment of the natural fibers, the use of compatibilizing agents, or surface modification.
Materials & Methods
MATERIALS
Low-density polyethylene (LDPE) is used in a wide range of applications because of its properties, including excellent processability, low cost, flexibility, chemical resistance, and good mechanical performance. Much of the polyethylene is used for packaging, and because it has a short useful life, it quickly becomes waste that is sent to landfills or, unfortunately, dumped into the ocean. According to the paper, only 10% of LDPE is estimated to be recycled in Brazil.
Low-density polyethylene waste from the Recyclable Waste Collectors Cooperative (COCAL), in the form of packaging films, was used.
The resulting agro-industrial waste (natural fiber, cellulose, and cellulose nanofibrils) from palm oil production comes from Brasil Bio Fuels Ltda., in the city of São João da Baliza.
methods
A thermogravimetric analysis (TGA) was performed to understand the thermal decomposition of the sample and reinforcement and determine the process limitations. Thermogravimetric analysis measures changes in a sample’s mass as the temperature changes, providing data on the compound’s thermal stability.
Other parameters were also evaluated, including tensile strength, elongation at break, and impact strength, which enabled us to obtain an overall picture of the mechanical properties of the final product reinforced with natural fibers (NF), cellulose (CEL), and cellulose nanofibrils (CNF).
Experimental Results
Natural fibers (NF) ; Cellulose (CEL) ; Cellulose nanofibrils (CNF).
| Material | Tensile strength (MPa) ± uncertainty | Elongation at break (%) ± uncertainty |
| LDPE | 17,2 ± 0,8 | 179 ± 70 |
| LDPE / NF 3% | 14,9 ± 0,6 | 104 ± 24 |
| LDPE / NF 7% | 13,9 ± 0,3 | 111 ± 27 |
| LDPE / CEL 3% | 15.9 ± 0.4 | 148 ± 39 |
| LDPE / CEL 7% | 10,4 ± 0,3 | 25 ± 7 |
| LDPE / CNF 1% | 10.3 ± 0.4 | 79 ± 22 |
| LDPE / CNF 7% | 9.8 ± 0.1 | 55 ± 22 |
Elongation at break (%) = As a percentage, how much the material can stretch before breaking. 179% means the material can stretch 179% beyond its original length before breaking.
MPa = megapascal, a unit of pressure measurement.
1 MPa = 10 bar
1 MPa = 1,000,000 Pa
- LDPE compounds with increasing mass addition of NF exhibit lower tensile strength and exhibit an increasing elongation at break.
- LDPE compounds with an increasing mass addition of CEL show a more significant decrease in tensile strength and a drastic drop in elongation at break.
- LDPE composites with an increasing mass addition of CNF show a slight decrease in tensile strength and a reduction in elongation at break.
Despite the decrease in the elongation-at-break percentage observed for LDPE composites with CEL and CNF, the final values are still high due to the high deformation that is characteristic of LDPE.
Incorporating natural fibers (NF) and purified cellulose (CEL) at a low concentration (3 wt%) caused a slight increase in the impact resistance of the composites. It’s an important result because impact resistance and elongation at break define a material’s applications.
Impact resistance:
- LDPE: approximately 51 kJ/m².
- LDPE/CNF 1%: approximately 71 kJ/m².
It shows that a small amount of cellulose nanofibrils can significantly improve an important mechanical property, even when tensile strength decreases.
Limitations and Future Perspectives
The use of Amazonian agro-industrial waste, such as oil palm waste, remains largely unexplored. However, this study lays the groundwork for a sustainable alternative: using natural fiber (NF), cellulose (CEL), and cellulose nanofibrils (CNF) from palm oil waste to produce composites with improved mechanical and structural properties.
The tensile mechanical properties, such as tensile strength and elongation at break, decrease, compared with unreinforced DLPE, when natural fibers are used as reinforcement in LDPE/NF composites. However, the final results remain high, making these materials suitable for applications using fibers with low production costs.
Higher CEL and CNF contents lead to a decrease in the mechanical performance of polymer composites, which has been linked to the formation of filler aggregates. The increase in CEL and CNF contents also leads to higher production cost of the composites.
Bibliographic sources:
- de Sá Barros, S., de Andrade Junior, A.J., Arantes, V. et al. Recycling of polyethylene waste as reinforced composites with modified lignocellulosic materials from palm oil industry. Polym. Bull. 84, 31 (2027). DOI: https://doi.org/10.1007/s00289-026-06790-y
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