Optimization of the supercritical carbon dioxide foaming process for biodegradable polylactide using response surface methodology

Name: Yudanto, Yusuf Arya

keyword: Cell morphology

; Compressive modulus

; Optimization

; Polylactide

; Polymeric foams

; Polyurethane

; Response surface methodology

; Creep-resistant

; Supercritical CO2

; Wettability

Abstract: An optimization study utilizing response surface methodology (RSM) and central composite design (CCD) was conducted to investigate batch foaming processes using supercritical CO2 as the physical blowing agent for neat polylactide (PLA) and polylactide/polyurethane (PLA/PU) blend foams. This study investigates the effect of single processing parameters on the properties of neat PLA foams. We demonstrate a complex interplay between foaming conditions and resulting foam properties, driven by competing effects of cell collapse and nucleation under varying temperatures, pressure, and time. Notably, thicker cell walls and higher sphericity, achieved through optimized foaming conditions, significantly enhance the foam’s compressive modulus and resistance to localized collapse. These findings underscore the critical role of processing parameters in tailoring the mechanical properties of PLA foams for diverse applications. Significant interactions between foaming process parameters were identified, impacting the properties of neat PLA foams. Foam density and average cell size exhibited an inverse relationship with foaming temperature and time. Initially, increases in both parameters decreased foam density and increased average cell size, attributed to enhanced gas dissolution at higher temperatures and longer durations, promoting rapid cell growth. Subsequent rises in these factors slightly increased foam density, possibly due to instability of foam structure and excessive gas diffusion. Compressive modulus was influenced by temperature and time, achieving the highest modulus at 50% strain under shorter foaming times and lower temperatures, facilitating rapid PLA solidification and smaller crystallite growth. Cell density decreased with rising temperature and pressure, likely from increased CO2 dissolution fostering more cell nuclei and reduced cell merging. Optimal lightweight PLA foams were obtained at 180°C, 165 bar, and 2.3 hours. Moreover, chemically recycled PLA, synthesized into polyurethane and blended with commercial PLA, demonstrated interactions between foaming parameters affecting foam properties. Higher IPDI composition and foaming temperatures reduced foam density by promoting cell nucleation and cell merging. The compressive modulus was influenced by increased foaming temperature and IPDI composition, impacting cellular structure and smaller cell morphology. Optimal lightweight PLA/PU blend foams were achieved at 1 mL of IPDI composition, 165°C of foaming temperature, and 174 bar of foaming pressure with fixed foaming time of 1.5 hours, highlighting the potential of these materials in diverse applications. These studies highlight the dual potential of PLA-based foams: neat PLA foam as an eco-friendly absorbent for organic solvents and oil, and PLA/PU blend foam as a remarkably creep-resistant material, paving the way for advanced applications across diverse industries

Thammasat University. Thammasat University Library

Address: BANGKOK

Email: preserv@tu.ac.th

Name: Pakorn Opaprakasit

Role: advisor

Created: 2023

Modified: 2024-08-05

Issued: 2024-08-05

DOI: 10.14457/TU.the.2023.82

eng

DegreeName: Master of Science

Level: Master's Degree

Descipline: Engineering and Technology

Grantor: Thammasat University

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