Durable PP/EPDM/GF/SiO2 nanocomposites with improved strength and toughness for orthotic applications. (February 2023) - Raghvan, Sonu
Abstract: Ankle-foot orthotics need ideal specification of being light-weight, high strength, tough, stiff, and durable. Reinforced polypropylene (PP) composites with enhanced mechanical properties are the most favorable materials being used in this field, but still, it is challenging to achieve balanced blend of strength and toughness in the composites. The present study thus aims to achieve the challenging task of simultaneous improvement in stiffness and toughness in reinforced PP composites exploring the synergistic reinforcement effect of glass fibers (GFs) and nano silica (SiO2) as multiscale fillers and ethylene propylene diene monomer (EPDM) as impact modifier. EPDM is used as toughness modifier, addressing the brittle behavior, but at the cost of the strength of the polymer. Combined use of micro and nanofillers as reinforcement in toughened polypropylene provides a potential approach to balance the strength while maintaining the toughness. GFs could offer high strength and nanofillers offer ductile fracture to the material. PP, PP/GF, PP/EPDM/GF composites and PP/EPDM/GF/SiO2 nanocomposites are fabricated through melt blending technique and are characterized through SEM, mechanical evaluation, nanoindentation and dynamic mechanical analysis. Mechanical properties are evaluated in accordance with ASTM standards. PP/EPDM/GF/SiO2 nanocomposites exhibits remarkable enhancement in Tensile strength, tensile modulus, impact strength and percent elongation at break by 49 MPa (55% increase over PP), 2450 MPa (145% increase), 145 J/m (13% increase) and 156% (160% increase) respectively. The exceptional improvement in reduced modulus and hardness reveals good interfacial properties. Loss factor decrement reveals elastic behavior of nanocomposites suitable for thermoforming of nanocomposites for orthotic device fabrication. Graphical abstract: Image 1 Highlights: Durable, strong, low-cost PP/EPDM/GF/SiO2 nanocomposites for orthotic applications. Incorporation of EPDM, Glass fibers and silica nanoparticles in PP nanocomposites for balanced strength and toughness. Increased storage modulus and decrement in loss factor provides required elastic behavior for orthotic application. PP/EPDM/GF/SiO2 nanocomposites exhibits 55% increase in tensile strength, 145% increase in tensile modulus, 13% increase in impact strength, 160% increase in % elongation at break, 207% increase in elastic modulus, and 963% increase in hardness over neat PP.