Film properties from crosslinking of cellulosic derivatives with a
polyfunctional carboxylic acid
V. Coma
a,
*
, I. Sebti
a
, P. Pardon
b
, F.H. Pichavant
b
, A. Deschamps
a
a
Laboratoire de Chimie des Substances Ve
´
ge
´
tales, Institut du Pin-Universite
´
Bordeaux 1, 351 cours de la Libe
´
ration, 33405 Talence, France
b
Recherche Applique
´
e en Chimie Industrielle Organique, Institut du Pin-Universite
´
Bordeaux 1, 351 cours de la Libe
´
ration, 33405 Talence, France
Received 17 July 2001; revised 30 May 2002; accepted 30 May 2002
Abstract
In order to decrease water sensitivity of packaging materials based on water-soluble cellulose derivatives, and especially to avoid partial
solubilisation of films into food products, crosslinking of hydroxy propyl methyl cellulose (HPMC) with citric acid was carried out using
different contents of polycarboxylic acid and catalyst. To determine reticulation rate or ester bond rate in crosslinked cellulosic derivatives,
FTIR in transmittance, based on of the ester band (1735 cm
21
) was compared to acid–base titration. Infra-red spectroscopy had advantages
over time consuming titration. Crosslinking of the hydrophilic polymers induced a strong influence on water solubility and an improvement
in the water vapor barrier of about 34%. q 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Cellulosic based packaging; Crosslinking; Moisture barrier properties
1. Introduction
Water-soluble cellulose derivatives are mainly used for
non-food applications, especially packaging because of
their edibility and biodegradability. A limitation of these
packaging materials is their water sensitivity, producing a
loss of barrier properties when the degree of hydration
increases and also, a solubilisation of bio-coatings into food
with a significant water activity. In previous publications,
we reported a study of bioactive edible packaging material
based on hydroxy propyl methyl cellulose (HPMC). It was
found that the moisture barrier was improved by stearic acid
incorporation into the film forming solution, however there
were difficulties in preparing a homogenous composite film
with both hydrophobic and hydrophilic compounds (Sebti,
Pichavant, Pardon, & Coma, 2000; Coma, Sebti, Pardon,
Deschamps, & Pichavant, 2001). For these reasons, an
homogeneous packaging film was prepared from HMPC by
chemical modification allowing an increase in hydrophobi-
city. Crosslinking of HPMC can be considered a useful
approach to prepare non-water soluble cellulose derivatives
with interesting moisture barrier properties, which could be
used as biodegradable packaging materials. Keslter and
Fennema (1986) reported that, crosslinking would decrease
polymer chain mobility which, in synthetic polymers,
increases the resistance to vapor and gas transport. An
attempt was made to enhance barrier characteristics by
crosslinking modified polysaccharides chains. Highly
water-soluble HPMC crosslinked to various extents should
offer the possibility to modulate its biodegradability.
Glutaraldehyde has been frequently used to crosslink
polysaccharides (Kawase, Michibayashi, Nakashima, Kur-
ikawa, Yagi, & Mizaoguchi, 1997) but it is reported to
contain cytotoxic chemical species (Dal Pozzo et al., 2000).
Polyethyleneglycol (PEG) was also used as linking factor,
especially on chitosan (Dal Pozzo et al., 2000). According to
Zhou, Luner, and Caluwe (1995), the effectiveness of
carboxylic acids to crosslink papers increased with their
functionality in the order of 1,2,3,4 butane tetra carboxylic
acid (BTCA) . Tricarballylic acid . Succinic acid. This
phenomenon could be due to their ability to form highly
reactive cyclic anhydride under thermal reaction conditions.
These previously results showed higher crosslinking
effectiveness with polycarboxylic acid with at least three
reactive groups. As a result, citric acid was selected, taking
into account its non-toxicity and its wide use in the food
industry as a safe natural additive.
The present work was aimed at introducing a certain
degree of crosslinking in cellulosic derivative via a citric
0144-8617/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
PII: S 0 1 4 4 - 8 6 1 7 ( 0 2 ) 0 0 1 9 1 - 1
Carbohydrate Polymers 51 (2003) 265–271
www.elsevier.com/locate/carbpol
*
Corresponding author. Tel.: þ33-55796-2913; fax: þ 33-55684-6422.
E-mail address: v.coma@ipin.u-bordeaux.fr (V. Coma).