Environmental Engineering Reference
In-Depth Information
Table 8.2
Selected Barrier Properties of Common Plastic
Packaging Films (25 μm Thick) Measured at 38°C
Source: Adapted from Bhunia et al. (2013).
Polymer Oxygen transmission rate
(OTR) at 25°C and 0% RH
(cm
3
/m
2
/day)
Water vapor
permeability at 38°C and
90% RH (g/m
2
/day)
LDPE
7750
16-31
HDPE
1550-3100
6
PET
50-90
16-23
PP
1550-2480
6
PS
3100-3500
109-155
PC
2480
140
PVDC
2-16
0.8-5
PVC
465-9300
31-155
PA
15-30
155
PET/Al
foil/PE
0
0
Often, there is no single cost-effective plastic material that meets the
combination of barrier properties as well as the mechanical integrity
demanded by a specific packaging application. Multilayer packaging
addresses this problem; in fact, approximately 17% of all packaging
laminates are multilayer constructs. For instance, ethylene vinyl alcohol
(EVOH) copolymer resins offer an excellent high-barrier to gases, but only
under dry conditions. Therefore, it is generally sandwiched between layers
of hydrophobic plastics; multilayer films with PET/EVOH/EVA or LLDPE/
EVOH/LLDPE are used in food packaging. Plastic beer bottles, for instance,
use PET/EVOH/PET constructs (Bucklow and Butler, 2000). Other useful
properties such as heat sealability (at 110-125°C) are often built into
multilayer films by adding a copolymer (ethylene-
co
-propylene) or
terpolymer (ethylene-
co
-propylene-
co
-butene) layer on either side of
polyolefin or multilayer film. Composite polymer/paper/foil packages used
for beverages or juices are even more complex in design. The specialized
design of these affords excellent protection to the beverage but recycling
