Barrier Properties of Biodegradable Bacterial Polyester Films - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 57

Chapter 6
Barrier Properties of Biodegradable Bacterial
Polyester Films
Nad è ge Follain, Fr é d é ric Chivrac, Florent Girard, and St é phane Marais
iNtroduCtioN
With the increasing concern of human society to environmental and energy problems,
the family of microbial synthesized polymers poly(hydroxyalkanoates) (PHA) have
been attracting more and more attention in both academic and industrial fields due to
their complete biodegradability and the renewable carbon resources used to produce
them (Doi, 1990; Müller, 1993).
Undoubtedly, the use of long-lasting polymers for short-lived applications (pack-
aging, catering, surgery, hygiene…) is facing the global growing conscience relating
to the preservation of ecological systems. Most of the today's polymers are produced
from petrochemicals and so are not biodegradable. Indeed, such alternative bio-based
packaging materials have attracted considerable research and development interest
for a significant length of time. In this context, tailoring new environment-friendly
polymers based on PHA have numerous specific properties, which open new fields
of applications. The PHA received increasing attention during the last decade due to
its biodegradability, biocompatibility and physiologically benign behavior that makes
them interesting for biomedical or food applications, for example. In the family of
PHA, polyhydroxybutyrate (PHB) and its copolymers are the most produced and in-
vestigated products, and the molecular structure differences result in copolymers that
are more ductile and processable than PHB.
The aim of this study is to evaluate the potential of bio-based packaging materi-
als from microorganisms for film applications, and the most important properties can
be narrowed down to four intrinsic properties of the material: mechanical, thermal,
gas barrier and water vapor properties. This work will focus on the two latter proper-
ties which are few considered in the literature. To date, to our knowledge, very few
researches, investigating barrier properties to diffusing water and/or gas molecules of
PHA family, have been published despite some published studies devoted to biode-
gradable polyesters including PHA. Future bio-based materials must be able to mimic
the gas and water vapor barriers of the conventional materials known today in the
considered case of replacement materials. In addition, in storage or under operation
conditions, polymer materials are often exposed to moisture and water molecules can
penetrate a polymer matrix thus modifying its physical and transport properties. When
compared to conventional polymers, PHBV copolymers showed a very good balance
of barrier properties as regards to water and diffusing gas molecules. Besides, these
copolymers have the great advantage of its moisture insensitivity and low hydrophilic
character, common drawback of bio-based polymers.