Barrier Properties of Biodegradable Bacterial Polyester Films - Natural Polymers, Biopolymers, Biomaterials, and Their Composites, Blends, and IPNs - page 69

table 1. (Continued)

Glass
transition
temperature
(°C)

Tensile
strength
at break
(MPa)

Melting
temperature
(°C)

Young's
modulus
(MPa)

Crystallinity
(%)

Elongation
at break (%)

Density

PLA
Dow-Cargill -
Natureworks

1.25 152 58 0-2 2000 - 9

PCL
Solvay - CAPA680

1.11 65 -61 67 190 14 > 500

PCL
Solvay - CAPA6500

- 59 - 41 383 36.1 668

PEA
Bayer - BAK1095

1.07 112 -29 33 262 17 420

PBSA
Showa - Bionolle3000

1.23 114 -45 41 249 19 > 500

PBAT
Eastman - Eastar Bio
14766

1.21 110-115 -30 20-35 52 9 > 500

Source: Data extracted to Sudesh, 2000; Averous, 2004; Bardwaj, 2006; Duquesne, 2007.

traNsPort ProPerties
The objective of this section is to describe the barrier properties of PHA polymers
compared to common polymers and some commercially available polyesters. To
achieve this objective, the transport properties of the polymer films have been per-
formed with diffusing molecules either at liquid state for sorption measurements or at
gas and liquid state for permeation measurements.
Generally, water and carbon dioxide molecules, subjects of great importance in the
field of packaging, are considered in the case of sorption measurements because poly-
esters contain ester groups on the backbone structure which can interact with water or
carbon dioxide molecules.
For permeation measurements, diffusing molecules are classified as a function of
the difference in their kinetic diameter and their interaction capacity: nitrogen for its
chemical inertia, carbon dioxide, dioxygen for their molecule diameter, and water for
its ability to interact with the polymer. The permeation mechanisms depend on the
chemical nature of the polymer and the diffusing molecules characteristics, explaining
why barrier properties are classified according to the type of diffusing molecules. Most
important external parameters are temperature and humidity affecting the behavior
and the structure of both the polymer and the diffusing molecule. Therefore, it is of
prime importance to know in which conditions tests have been carried out.

Water Vapor sorption
Even though results from different research teams are difficult to compare due to the
differences in methods and measuring conditions, data shown in Figure 8 (data recal-
culated from original papers (Gouanve, 2007; Guptaa, 2007; Miguel, 1999a; Oliveira,