Open Access

ARTICLE

Tamarindus Indica Bark Powder as a Sustainable Bio-Based Filler for Enhancing Bondline Uniformity and Performance of Polyurethane Adhesives in Wood Bonding

Lakshmana Rao Bhagavathi^1,*, Sk. Gouse¹, T. Siva², Mohammad Faseeulla Khan^3,*
1 Department of Mechanical Engineering, Rajiv Gandhi University of Knowledge Technologies Nuzvid, Eluru District, India
2 Department of Metallurgical & Materials Engineering, Rajiv Gandhi University of Knowledge Technologies Nuzvid, Eluru District, India
3 Department of Mechanical Engineering, College of Engineering, King Faisal University, Al-Ahsa, Saudi Arabia
* Corresponding Author: Lakshmana Rao Bhagavathi. Email: ; Mohammad Faseeulla Khan. Email:

Journal of Polymer Materials https://doi.org/10.32604/jpm.2026.088128

Received 29 June 2026; Accepted 14 September 2026; Published online 18 September 2026

Abstract

Polyurethane (PU) adhesives are extensively used in wood bonding due to their high reactivity and strong adhesion. However, excessive penetration of the adhesive into the wood substrate often results in non-uniform bondline thickness, which can compromise joint performance. The use of environmentally compatible fillers offers a sustainable approach to address this limitation. In the present study, Tamarindus indica bark powder was used as a natural filler to achieve uniform bondline thickness in PU-bonded joints. Lap-shear joints were produced using untreated and treated bark powders at varying weight fractions, reinforced within a one-component moisture-curing PU adhesive. The mechanical performance and bondline morphology of these joints were systematically evaluated and compared with PU joints reinforced with microcrystalline cellulose. Further, Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) of all the samples were performed. Results indicate that the addition of bark powder enhances bondline uniformity, improves lap-shear strength, and increases thermal stability compared to unreinforced PU samples. The results demonstrate that Tamarindus indica bark powder can effectively enhance bondline uniformity, mechanical strength, and thermal stability, establishing it as a viable bio-based reinforcement for advanced PU adhesive systems in wood bonding applications.

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Keywords

Polyurethane adhesives; wood bonding; bondline thickness; Tamarindus indica bark powder; green fillers; microcrystalline cellulose

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