Recycled Polypropylene Composites Reinforced with Microcellulose Fibres and Microcellulose-Derived Biochar: Thermal,...

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Materials

Background:

• Mechanical recycling of biaxially oriented polypropylene (BOPP) films yields recycled polypropylene (rPP) with diminished properties.
• Degraded rPP properties restrict its application in high-performance products, necessitating material enhancement strategies.

Purpose of the Study:

• To investigate the reinforcement of rPP using microcellulose fibers (MCFs) and microcellulose-derived biochar (BC).
• To evaluate the impact of MCFs and BC on the thermal, rheological, mechanical, and surface properties of rPP.

Main Methods:

• Characterization using Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis/Derivative Thermogravimetric analysis (TGA/DTG), Melt Volume Rate/Melt Flow Rate (MVR/MFR), and temperature-dependent rheology.
• Mechanical testing (tensile and flexural moduli) and water contact angle (WCA) measurements were performed.
• Analysis of rPP composites with varying loadings of MCFs (2-10 parts per hundred parts of resin by weight, pbw) and BC (5-20 pbw).

Main Results:

• Both MCFs and BC acted as heterogeneous nucleating agents, increasing rPP crystallinity by 2-4% and shifting crystallization temperatures by up to 4 °C.
• MCFs introduced a low-temperature degradation step, while BC enhanced thermal stability, increasing degradation temperatures by up to 20 °C and char yield.
• MCFs reduced melt viscosity (increased MVR/MFR by 20-25%), whereas BC increased melt stiffness (decreased MVR/MFR by up to 50%).
• Tensile and flexural moduli increased by 15-25% with MCFs and 40-50% with BC.
• MCFs decreased WCA to 63.0°, enhancing wettability, while BC increased WCA to 108.1°, imparting hydrophobicity.

Conclusions:

• Converting cellulosic feedstock into MCFs or BC provides a bio-based method for upgrading rPP properties.
• These fillers offer distinct property modifications, enabling tailored performance for diverse applications.
• The findings align with circular economy principles by valorizing recycled materials.