Industrial Crops and Products 12 2000 125 – 135
Synthesis and properties of water-resistant polyglucaramides
Geoffrey A.R. Nobes , William J. Orts, Gregory M. Glenn
United States Department of Agriculture, Agricultural Research Ser6ice, Western Regional Research Center,
800
Buchanan Street, Albany, CA
94710
, USA Received 8 August 1999; accepted 26 March 2000
Abstract
Replacing nonrenewable polymers with renewable ones is desirable for packaging applications. For this purpose, a number of polyglucaramides were synthesized and tested for applications requiring water resistance. The polymers
were prepared from the polycondensation of esterified glucaric acid and a diamine, the former being obtained from the oxidation of glucose, thus providing a renewable source for the monomer. Polyglucaramides were prepared with
up to a 74 yield. The polymers were characterized by differential scanning calorimetry DSC,
1
H and
13
C nuclear magnetic resonance NMR spectroscopy, X-ray diffraction and gel permeation chromatography GPC. The
polyglucaramides were tested for their usefulness by incorporating them into pressed fiber-reinforced composite panels. Two polyglucaramides were chosen for further testing. These imparted a detectable degree of water
resistance to the panels. Published by Elsevier Science B.V.
Keywords
:
Fiber-reinforced panels; Mechanical properties; Polyglucaramides; Water resistance www.elsevier.comlocateindcrop
1. Introduction
Commodity polymers derived from nonrenew- able resources such as fossil fuels are extremely
widespread in modern life, being used in numer- ous plastics applications. However, despite their
inherent usefulness, they present a major environ- mental problem since typical disposal involves
deposition into the largely anaerobic conditions of landfill. The consequence is that plastic products
may languish in the environment for many years. Because commodity plastics are derived from
petroleum feedstocks, alternative renewable re- sources derived from plant material are being
developed.
Starch is an abundant biopolymer, which repre- sents one type of renewable resource from which
plastics can be produced Galliard and Bowler, 1987; Koch and Ro¨per, 1988; Zobel, 1988; Mad-
dever and Chapman, 1989; Ro¨per and Koch, 1990; Doane, 1992; Kim and Pometto, 1994;
Glenn and Hsu, 1997; Ellis et al., 1998. Starch can also be foamed to make products with low
density and good insulating properties Glenn and
Corresponding author. Tel.: + 1-510-5595628; fax: + 1- 510-5595936.
E-mail address
:
nobespw.usda.gov G.A.R. Nobes 0926-669000 - see front matter Published by Elsevier Science B.V.
PII: S 0 9 2 6 - 6 6 9 0 0 0 0 0 0 4 7 - 9
Irving, 1995; Glenn et al., 1996, but they do not have good water resistance. Therefore, a water-re-
sistant coating must be applied to the starch- based product in order to impart water resistivity
to it. The purpose of the present study was to incorporate a water-insoluble polymer derived
from renewable resources in the formulation of starch-based plastic products in order to avoid the
need for a coating.
Polyglucaramides or hydroxylated nylons are one class of water-insoluble polymer derived from
renewable resources. These polymers are struc- turally analogous to nylons in that they are com-
posed of a diacid component and a diamine component. With polyglucaramides, the diacid
component is glucaric acid, a six-carbon diacid with hydroxyl groups at positions 2, 3, 4 and 5,
hence the term hydroxylated nylon. Glucaric acid is a product of the oxidation of glucose. The
chemistry of polyglucaramides was developed by Kiely and coworkers beginning in the late 1980s
Kiely and Lin, 1989; Kiely and Chen, 1994; Kiely et al., 1994; Chen and Kiely, 1996. The synthesis
of polyglucaramides involves a reaction se- quence based on unprotected esterified
D
-glucaric acid by simple condensation reactions. This sys-
tem is efficient and allows for a great deal of versatility in polymer composition because of the
large variety of diamines that can be used.
The first step in the production of polyglu- caramides is the hydrolysis of starch by either
chemical i.e. acid or enzymatic methods or a combined approach to glucose see Fig. 1. In the
second step, the glucose is oxidized to form glu- caric acid. Following a direct esterification of
glucaric acid, it can be reacted with a multifunc- tional amine, usually a diamine, to form the
polyglucaramide see Fig. 1. The polymeriza- tion reaction occurs at room temperature and no
specialized reaction conditions, such as an inert atmosphere, are needed. The polymer is isolated
by filtration.
In this
study, semicrystalline
polyglu- caramides were prepared and were processed
with various agricultural fibers to form composite panels.
2. Materials and methods
