The Role of Interfacial Adhesion in Polymer Composites Engineered from Lignocellulosic Agricultural Waste

Abstract

This paper presents a comprehensive study about the application of a lignocellulosic agricultural waste, sunflower husk in different polymer composites. Two types of milled sunflower husk with different geometrical factors were incorporated into polypropylene, low-density and high-density polyethylene, polystyrene (PS), glycol-modified polyethylene terephthalate (PETG) and polylactic acid (PLA). The filler content of the composites varied between 0 and 60 vol%. The components were homogenized in an internal mixer and plates were compression molded for testing. The Lewis–Nielsen model was fitted to the moduli of each composite series, and it was found that the physical contact of the filler particles is a limiting factor of composite modulus. Interfacial interactions were estimated from two independent approaches. Firstly, the extent of reinforcement was determined from the composition dependence of tensile strength. Secondly, the reversible work of adhesion was calculated from the surface energies of the components. As only weak van der Waals interactions develop in the interphase of polyolefins and sunflower husk particles, adhesion is weak in their composites resulting in poor reinforcement. Interfacial adhesion enhanced by specific interactions in the interphase, such as π electron interactions for PS, hydrogen bonds for PLA, and both for PETG based composites.

Preparation and Properties of Thermoplastic Polyurethane Composites Filled with Powdered Buckwheat Husks

“…The values of polymer matrix-filler interaction parameters suggest that chemical treatment applied for filler results in worsening of matrix-filler interaction (probably due to decreasing hydrophilicity of the filler after the treatment). On the other hand, observed values of B parameter are relatively high in comparison to this reported in the literature for other polymer composites, for example: poly(lactic acid)/milled sunflower husks (B = 2.50; 2.59), glycol modified poly(ethylene terephthalate)/milled sunflower husks (B = 2.04; 2.57), polystyrene/milled sunflower husks (B = 2.56; 2.65) [ 39 ], polypropylene/unmodified wood flour (B = 1.8), polypropylene/wood flour modified with maleic anhydride (B = 1.1) [ 40 ]. The matrix–filler interaction parameter is affected by several different factors, i.e., the size of the interface (connected to the specific surface area of the filler), surface treatment method, aggregation, and anisotropy of the filler and polymer matrix chemical structure and properties [ 38 ].…”

High-density Polyethylene - Expanded Perlite Composites: Structural Oriented Analysis of Mechanical and Thermomechanical Properties

“…The increase in composite stiffness is observed in most thermoplastic polymers' modifications using particle-shaped fillers [21,22]. The effect is caused by dispersion of the rigid structures, which limit the mobility of the polymeric chains during the strain, and is especially pronounced in the case of the good polymer-filler adhesion [23,24]. The addition of inorganic filler caused a significant decrease in elongation at break in composites compared to unmodified HDPE.…”

Utilization of Wood Flour Waste as a Filler on Polypropylene Random Pipes Industry

“…The pronounced hydrophobic nature of specific thermoplastics, like polyolefins, leads to challenges regarding compatibility with hydrophilic lignocellulosic materials. Given that the mechanical and physical characteristics of these composites are inherently linked to the compatibility and interaction among their constituents, enhancing the interface and interphase interactions in thermoplastic composites is imperative (Kun et al, 2021). Diverse methods are employed to enhance the mechanical characteristics of composites.…”

“…Two principal strategies for bolstering mechanical properties through fillers involve their treatment with coupling agents such as maleic anhydride (MAPP) (Kada et al, 2015;Arao et al, 2014;Adhikari et al, 2012). Or a chemical coupling agents such as alkaline treatment (Kun et al, 2021), typically polymers, are applied in minor quantities to treat a surface, facilitating bonding between the treated surface and other materials, such as wood and thermoplastics (Tabari, Nourbakhsh and Ashori 2011). Alkaline treatment effectively eliminates surface impurities and disrupts hydrogen bonds, thereby enhancing surface roughness (Khamtree, Ratanawilai, Ratanawilai 2020).…”