Using Microcellular Starch Foam as an Environmentally Benign Filler in Paper
Venditti and Pawlak, Paper Science and Engineering
Introduction The objective of this project is to determine if starch can be substituted as a filler
in the production of paper. An additional objective is to describe the effect this change has on
the physical properties of the sheet. Research in the area of microcellular starch foams is
important because there is potential to introduce sheet properties that will create a stronger, less
dense sheet. Also, starch is a readily available, renewable, and biodegradable resource that could
prove more cost effective and environmentally conscious that current filler technology. The
proposed research will address the problem of determining an optimal method of incorporating
the microcellular starch foam into the sheet. Once the foam is successfully added to the sheet,
the effects of the starch foam on the mechanical properties of the sheet will be determined.
Project Additional Information This project will be primarily experimental. A peer reviewed
journal article will be prepared on the results. An experienced post doc will mentor the student.
The project is currently being funded by the USDA so there is some support for supplies and
equipment. The student should have basic undergraduate chemistry through organic chemistry.
Any experience with polymers and chemical engineering principles is a plus.
Background The worldwide availability and low cost of starch make it a desirable raw material
to use in industrial processes. Approximately 4.5 billion pounds of starch were used in annually
in the US for industrial applications in 1991, much of that being used in the paper industry.
Currently, starch is used by the paper industry as a wet-end additive, surface coating, and as an
adhesive. Starch, being a biodegradable resource derived from a renewable resource is highly
attractive when compared to petroleum based resources or resources mined from the earth.
Microcellular foams are low density, solid foams. They consist of a solid matrix with air-filled
pores. Starch based foams can be made using methods originally developed for other polymeric
materials. Microcellular foams can be made by gelatinizing starch then cooling the gel in a
mold. Air-drying causes the porous structure to collapse, but freeze-drying preserves the
structure and promotes low-density foam. Alternatively, the water can be replaced with a low
surface tension liquid such as ethanol and liquid carbon dioxide and then extracted to preserve
the matrix structure . The solvent-exchange process can be used with various types of starches,
including high-amylose corn and wheat starches. The starch foams formed are white, opaque,
and have densities ranging from 0.1 to 0.32 grams per cubic centimeter.
Research Plan
Microcellular foams from starch will be produced with varying amounts of sizing agents using
solvent exchange methods. The foams optical properties and structure will be determined. An
interpretation of the structure/properties relationship of the solid foams will be proposed. The
foams will then be ground into particles for incorporation into paper. The paper samples with
and without the starch foams incorporated will be produced, analyzed, and interpreted. Properties
of the paper (optical and mechanical) will be determined versus type and concentration of the
foam particles.