Polylactic Acid (PLA) Foaming: Design of Experiments for Cell Size Control

Miada Abubaker Osman,Mahmoud Rouabhia,Nick Virgilio,Frej Mighri

doi:10.4236/msa.2022.132005

Abstract

In this study, a design of experiments (DoE) approach was used to develop a PLA open-cell foam morphology using the compression molding technique. The effect of three molding parameters (foaming time, mold opening temperature, and weight concentration of the ADA blowing agent) on the cellular structure was investigated. A regression equation relating the average cell size to the above three processing parameters was developed from the DoE and the analysis of variance (ANOVA) was used to find the best dimensional fitting parameters based on the experimental data. With the help of the DoE technique, we were able to develop various foam morphologies having different average cell size distribution levels, which is important in the development of open-cell PLA scaffolds for bone regeneration for which the control of cell morphology is crucial for osteoblasts proliferation. For example, at a constant ADA weight concentration of 5.95 wt%, we were able to develop a narrow average cell size distribution ranging between 275 and 300 μm by varying the mold opening temperature between 106°C and 112°C, while maintaining the foaming time constant at 8 min, or by varying the mold foaming time between 6 and 11 min and maintaining the mold opening temperature at 109°C.

Highlights

IntroductionThere are several methods to produce polymer foams, such as injection or compression molding, and extrusion
The central composite design (CCD) technique was used in this work to design the three levels of the three independent processing parameters shown in Table 1, which are the foaming time under compression, X1, the mold opening temperature, X2 ( ̊C), and the ADA blowing agent weight concentration, X3
Open-cell foamed Polylactic acid (PLA) scaffolds were developed by compression molding and a three-level factorial Design of Experiments (DoE) was used to optimize the molding parameters to reach a well-controlled open-cell structure

Summary

Introduction

There are several methods to produce polymer foams, such as injection or compression molding, and extrusion. For all the foaming processes (extrusion, injection, or compression molding) using chemical foaming agents, the selection of the latter is based on a general rule of thumb. Its decomposition temperature should be relatively close to the polymer processing temperature, and the released gas should not chemically react with the polymer [3]

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Conclusion