Effect of silicone surfactant and distilled water on the structure, morphology, density, and compressive strength of polyurethane foam with utilization of castor oil

¹ Research Center for Energy Materials, National Research and Innovation Agency (BRIN) KST BJ. Habibie. South Tangerang City, 15314, Indonesia
² Department of Mechanical Engineering, CVR College of Engineering, Hyderabad, Telangana 501510, India
³ Department of Physics, Universitas Sumatera Utara, Jl. Bioteknologi No. 1, Medan 20155, Sumatera Utara, Indonesia
⁴ Department of Metallurgical Engineering, Universitas Sultan Ageng Tirtayasa, Jl. Jendral Sudirman Km 3, Kotabumi, Cilegon City, Banten, 42435, Indonesia

^* Corresponding author: satrio.herbirowo@gmail.com

Published online: 7 January 2026

Abstract

Polyurethane (PU) foam is used almost everywhere—from packaging to insulation and construction—but its production still relies largely on petroleum-based ingredients. In this study, we explored castor oil as a renewable alternative to conventional polyols, aiming to create PU foams that are both sustainable and versatile. We prepared the foams by reacting castor-oil-based polyol with methylene diphenyl diisocyanate (MDI), using different amounts of water as a blowing agent (1%, 10%, and 20% w/w) and silicone surfactant (2%, 10%, and 18% w/w) to help stabilize the foam structure. By adjusting these components, we examined how the formulations affected the foam’s appearance, density, and strength. Small changes in water and surfactant content led to three clear foam types: a rigid foam (1% water, 18% surfactant), a semi-rigid foam (10% water, 2% surfactant), and a flexible foam (20% water, 10% surfactant). The rigid foam showed the highest strength and density, while the semi-rigid and flexible versions had progressively softer and lighter structures. Overall, our findings show that castor-oil-based PU foam can be tuned to meet different performance needs simply by adjusting its formulation. This offers a practical and renewable pathway for producing PU foams with properties comparable to those made from petroleum-based materials.