Creating Polyurethane Films from Renewable Resources and Examining Their Mechanical Characteristics with IPDI and CHDI

The polymer industry primarily relies on petroleum-based raw materials for polyurethane (PU) production. However, extensive research is being conducted to identify sustainable alternatives. This study explores the use of bio-based polyols derived from limonene and geraniol. Limonene is naturally sourced from citrus fruits like oranges, lemons, limes, and grapefruits, while geraniol is found in essential oils such as citronella, rose, and palmarosa oil. These renewable materials contribute to making the polymer industry more sustainable. In PU synthesis, isophorone diisocyanate (IPDI) and cyclohexyl diisocyanate (CHDI) are used. The structural characterization of polyols and PUs is carried out using Fourier Transform Infrared Spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR). Mechanical properties, including tensile strength and hardness, are evaluated through standard testing methods, while thermal behavior is analyzed using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). DSC results indicate good miscibility of the synthesized PUs, with glass transition temperatures (Tg) of 75°C for IPDI-based PU and 64.47°C for CHDI-based PU. TGA analysis reveals that the thermal degradation of these PUs begins beyond 200°C. In mechanical testing, the highest recorded tensile strength was 36 MPa for IPDI-based PU, while CHDI-based PU exhibited a tensile strength of 26 MPa. Additionally, the hardness values were 85 for IPDI-based PU and 74 for CHDI-based PU. The gel fraction analysis, which assesses the degree of cross-linking, shows that IPDI-based PU has a higher cross-link density than CHDI-based PU. Overall, IPDI-based polyurethane demonstrates superior mechanical strength and thermal stability compared to its CHDI counterpart, making it a preferable option for applications that demand high-performance materials.