Characterization of chemically foamed poly(lactic acid)

K Litauszki,Á Kmetty

doi:10.1088/1757-899x/903/1/012018

Abstract

This paper presents the characterization of poly(lactic acid)-based chemically foamed foam structures. We used extrusion grade, high molecular weight poly(lactic acid) as matrix material and azodicarbonamide as foaming agent. The resulting foams were characterized by foam density, cell population density, scanning electron microscopy, and based on the fracture surface of the foam cross-section, we calculated cell size distribution. The obtained distributions were fitted with the use of log-normal distribution in each case. We presented the effect of chemical blowing agent content (0.5 wt%, 1 wt%, 2 wt%, 4 wt% and 8 wt%) on the PLA-based foam structure and the effect of processing temperature (190 °C, 210 °C and 230 °C) on cell size distribution.

Highlights

The characterization of foam structures at a microstructural level can be approached from four aspects
We measured the density of foam samples calculated their cell population density, examined them by scanning electron microscope (SEM) and calculated the log-normal cell size distribution
The SEM images show that a small amount of cells nucleated at low chemical blowing agent (CBA) content (0.5 wt% and 1 wt%), and cell size is around 300 μm

Summary

Introduction

The characterization of foam structures at a microstructural level can be approached from four aspects. The first approach is based on the amount of material in the foam structure (density, relative density and void fraction). The foam structure can be characterized (2) by the ratio of open and closed cells, (3) cell size distribution and (4) cell structure anisotropy. Cell size distribution is typically investigated along a surface, such as a cross-section (2D). The cross-sectional surfaces used for observation are typically produced with a microtome or are cryogenic fracture surfaces. The number of cells, their size, their distribution and the degree of anisotropy can be determined from these images [1]. Cell size distribution is typically described with a log-normal distribution [2,3,4,5]

Methods

Results

Conclusion