Study on successful preparation of gas barrier multilayer films with
thickness of 80µm while PE film used as 2 outer layers and PE/EVOH or
PA6/EVOH polymer blend used as middle layer.
- For PE/PE-EVOH/PE multilayer films: Appropriate compatibilizer
content was 4%. When the PE/EVOH polymer blend layer content increased,
the mechanical properties of the multilayer films decreased slightly, the
oxygen transmission rate decreased, the water vapor transmission rate
increased. With the content of PE/EVOH (70/30) polymer blend layer 5 -
20%: oxygen transmission rate of the films 20.60 - 2.34 ml/m2.day, the water
vapor transmission rate of the films 4.78 – 9.58 g/m2.day.
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r even though PE-g-MAH has
low viscosity. The results also showed that when increasing the content of
PE-g-MAH compatibilizer, the torque of the polymer blend increased.
3.1.1.3. Mechanical properties of PE/EVOH polyme blends
Effects of PE/EVOH ratio on mechanical properties of PE/EVOH
polymer blends with and without PE-g-MAH compatibilizer were presented
in Table 3.1.
Table 3.1. Effect of the composition ratio on the mechanical properties
of PE/EVOH polymer blend
PE/EVOH
ratio
PE-g-MAH
compatibilizer (%)
Tensile
strength (MPa)
Elongation at
break (%)
100/0
0
29.5 1005.4
90/10 19.6 765.7
80/20 15.8 420.3
70/30 12.4 256.2
60/40 10.1 148.5
50/50 7.6 89.6
0/100 25.2 17.1
90/10
4
24.5 359.2
80/20 26.4 389.3
70/30 28.3 404.9
60/40 27.1 367.5
50/50 25.5 315.8
7
In samples without PE-g-MAH compatibilizer, both tensile strength
and elongation at break of the polyme blend samples decreased with
increasing EVOH content. This is because PE and EVOH have differences in
nature, chemical structure, polarity, surface interaction energy ... so the low
adhesion between PE and EVOH leads to agglomeration of a large EVOH
amount in the PE matrix.
In the presence of a compatibilizer, the mechanical properties of the
polymer blends were significantly improved. Tensile strength and elongation
at break increased because PE-g-MAH acted as an effective compatibilizer
between EVOH dispersion phase and PE matrix. Adding PE-g-MAH
increased the dispersion of EVOH and increases the adhesion between phases
to enhance the mechanical properties of polymer blends.
The results also showed that in the presence of 4% compatibilizer,
when the EVOH content increased from 10-30%, the tensile strength and
elongation at break increased. Tensile strength was significantly improved
when increasing EVOH content in polymer blends possibly due to high
tensile strength of EVOH. However, when the EVOH content was > 30%, the
mechanical properties of the polymer blends decrease because the tensile
strength was strongly influenced by the phase interaction between PE and
EVOH. This showed that when the EVOH content increased, the binding
capacity of PE and EVOH decreased.
The effect of the PE-g-MAH content on the mechanical properties of
the PE/EVOH polymer blends was presented in Table 3.2.
Table 3.2. Effect of PE-g-MAH content on mechanical properties of
PE/EVOH 70/30 polymer blend
PE-g-MAH content
(%)
Tensile strength
(MPa)
Elongation at break
(%)
0 12.4 256.2
2 25.6 379.8
4 28.3 404.9
6 26.5 416.3
8 24.1 420.4
10 23.9 418.5
The results showed that the tensile strength of the polymer blends
increased when the content of compatibilizer increased from 0-4%. However,
when the PE-g-MAH content continued to increase to > 4%, the tensile
strength of the polymer blend decreased and then stabilized. Elongation at
break increased when the PE-g-MAH content increased to 6%, then almost
unchanged. However, when the PE-g-MAH content continued to increase,
the mechanical properties of the polymer blend samples decreased.
8
3.1.1.4. Surface morphology of PE/EVOH polymer blends
SEM images of fracture surface of PE/EVOH polymer blends without
and with PE-g-MAH compatibilizer wre shown in Figure 3.6 and Figure 3.7.
a) PE/EVOH 90/10 b) PE/EVOH 80/20 c) PE/EVOH 70/30
d) PE/EVOH 60/40
e) PE/EVOH 50/50
Fig. 3.4. SEM images of fracture surface of PE/EVOH polymer blends
without PE-g-MAH compatibilizer
a) PE/EVOH 90/10
b) PE/EVOH 80/20 c) PE/EVOH 70/30
d) PE/EVOH 60/40
e) PE/EVOH 50/50
Fig. 3.5. SEM images of fracture surface of PE/EVOH polymer blends with
4% PE-g-MAH compatibilizer
SEM images of fractured surface of the polymer blends showed that in
the polyme blends without compatibilizer (Fig. 3.4), the phases dispersed
unevenly, forming distinct phase separation regions, the dispersion of EVOH
in PE matrix was quite large and coarse. With polymer blends containing
compatibilizer, when the EVOH content increased from 10-30%, the
component polymers had good dispersion and compatibility with each other.
9
However, when increasing EVOH content in polymer blend from 40-50%,
the compatibility between EVOH and LLDPE phases becomes worse.
3.1.1.5. Differential scanning calorimetry (DSC) of PE/EVOH polymer blends
DSC curves of PE/EVOH polymer blends with 4% PE-g-MAH
compatibilizer at different PE/EVOH ratios were summarized in Table 3.3.
Table 3.3. Effect of the LLDPE/EVOH ratio on thermal properties of
polymer blends
LLDPE/EVOH
ratio
Tg (
o
C) Tm (
o
C) Tc (
o
C)
Polyme blend LLDPE EVOH LLDPE EVOH
100/0 -20.7 121.8 - 104.8 -
90/10 -14.5 121.3 182.1 104.7 161.9
80/20 -2.4 120.4 182.7 104.6 161.3
70/30 6.32 122.0 183.0 102.5 159.2
60/40 6.5 và 38.5 120.7 184.0 103.8 161.1
50/50 6.0 và 38.8 122.3 184.2 104.3 160.9
0/100 40 - 184.4 - 162.3
The results showed that at 4% PE-g-MAH compatibilizer, when
increasing the EVOH content from 0-30%, a Tg in the range Tg of EVOH
(Tg = 40
o
C) and Tg of LLDPE (Tg = -20.7
o
C). This proves that in the
presence of a PE-g-MAH compatibilizer, at 10-30% EVOH, the two
polymers had good compatibility with each other. When the EVOH content
continued to increase from 40-50%, two Tg values appeared in the range of
Tg of the two component polymers. However, there was a shift in Tg of
LLDPE to Tg of EVOH. This proves that at the EVOH content of 40–50%, in
the presence of a PE-g-MAH compatibilizer, there was partial compatibility
between the two polymers.
The results also showed that the melting temperature Tm of LLDPE in
polymer blends did not change much when the EVOH content increased.
However, when increasing the EVOH content, the Tm value of EVOH in the
polymer blends increased slightly but was smaller than the Tm value of
EVOH resin.
Crystallization temperature (Tc) of LLDPE in blends is almost
unchanged. Meanwhile, when increasing EVOH content, Tc value of EVOH
in polymer blend decreased slightly compared with Tc of EVOH resin.
3.1.2. Study on preparation of PA6/EVOH polyme blends
To study preparation of polymer blend PA6/EVOH, polymer blend
samples were prepared at different ratios of PA6/EVOH 100/0, 90/10, 80/20,
75/25, 50/50 and evaluate the properties of the polymer blend samples.
3.1.2.1. Viscosity of PA6/EVOH polyme blends
The effect of the components rate on the torque of PA6/EVOH polymer
blends were presented in Fig. 3.10.
10
Fig. 3.10. Curves of mixing torque versus time for PA6, EVOH, PA6/EVOH
polyme blends
The results showed that the torque in the molten equilibrium of
PA6/EVOH polymer blends was lower than EVOH and higher than PA6. In
addition, when increasing the EVOH content in the polymer blend, the torque
in the molten equilibrium of the polymer blends increased. This may be due
to the interaction between the organizational groups in the polymer blend,
namely the amino groups of PA6 and the hydroxyl groups of EVOH. When
EVOH increased, the number of hydrogen bonds between hydroxyl groups
and amine groups increased, increased the intermolecular and intermolecular
bonds leading to an increase in torque.
3.1.2.2. Mechanical properties of PA6/EVOH polymer blends
Effects of the PA6/EVOH ratio on the mechanical properties of the
polymer blends wre presented in Table 3.5.
Table 3.5. Mechanical properties of PA6/EVOH polymer blends
PA6/EVOH ratio
(%)
Tensile strength
(MPa)
Elongation at break
(%)
100/0 60.4 29.5
90/10 58.7 42.5
80/20 52.6 58.6
75/25 48.6 74.2
50/50 32.4 68.4
0/100 25.1 17.2
The results showed that the tensile strength of PA6/EVOH polymer
blends decreased when the EVOH content increased. However, the
elongation at break increased when the EVOH content increased from 0-25%,
when the EVOH content increased to higher than 25%, the elongation at
break decreased.
3.1.2.3. Surface morphology of PA6/EVOH polymer blends
Morphology of fracture surface of PA6/EVOH polymer blends was
11
shown in figure 3.11.
PA6/EVOH 90/10 PA6/EVOH 80/20 PA6/EVOH 75/25
Fig. 3.11. SEM images of fracture surface of PA6/EVOH polymer blend
Observing the fracture surface SEM images of the PA6/EVOH polymer
blends, it was found that the fracture surface was relatively smooth, difficult
to distinguish the morphology of the two phases PA6 and EVOH after
mixing. This demonstrates a good dispersion of the two phases together.
Surface morphology of the polymer blends after soaking in dioxane
solution was shown in Figure 3.12.
PA6/EVOH 90/10 PA6/EVOH 80/20 PA6/EVOH 75/25
Fig.3.12. SEM images of PA6/EVOH polyme blends after soaking in
dioxane solution
The results showed that with samples containing low EVOH content
(Fig. 3.12a), there was no EVOH dispersion zone in the PA6 substrate. When
the EVOH content increased (Fig.3.12 (b), (c) and (d)), the corrosive EVOH
regions appear and the number of these eroded regions increases and the size
of the regions were larger as EVOH the content in polymer blends increased..
3.1.2.4. Differential scanning calorimetry (DSC) of PA6/EVOH polymer blends
Effect of PA6/EVOH ratio on thermal properties (crystallization
temperature Tc, melting temperature Tm and glass transition temperature Tg)
of PA6/EVOH polymer blends was presented in Table 3.6.
The results showed that the melting temperature of PA6 in the
PA6/EVOH polymer blends decreased from 226.3
o
C to 207.1
o
C when the
EVOH content increased from 0-50%, and the molten heat absorption
process of EVOH was not observed.
Crystallization temperature of PA6 decreased from 193
o
C to 170
o
C
when the EVOH content increased to 50%. This indicated the formation of
12
intermolecular and intramolecular hydrogen bonds and chemical interactions
between two polymers that form block copolymers (consisting of EVOH
blocks and PA6 blocks).
Table 3.6. DSC analysis results of polymer PA6, EVOH and PA6/EVOH
polymer blends
PA6/EVOH
ratio
Thermal properties of polyme blends
Tc (
o
C) Tm (
o
C)
100/0 193.0 226.3
90/10 189.2 218.1
80/20 185.0 214.8
75/25 181.1 213.3
50/50 170.4 207.1
0/100 162.3 184.4
3.2. Study on preparation of gas barrier multilayer films based on
polyme blends of EVOH and evaluate the lifetime of films
3.2.1. Study on preparation of PE/PE-EVOH/PE gas barrier multilayer films
3.2.1.1. Effect of PE-g-MAH compatibilizer content on properties of PE/PE-
EVOH/PE gas barrier multilayer films
To evaluate the effect of PE-g-MAH compatibilizer content in layer 1
and layer 3 on the properties of the PE/PE-EVOH/PE multilayer film, PE/PE-
EVOH/PE multilayer film with layer 2 (PE/EVOH polymer blend) accounted
for 15% in volume, layer 1 and layer 3 (LLDPE/PE-g-MAH polymer blend)
accounted for 85% in volume were prepared. The PE-g-MAH compatibilizer
contents in layer 1 and layer 3 were 0-8%.
3.2.1.1.1. Effect of PE-g-MAH compatibilizer content on surface morphology
of PE/PE-EVOH/PE gas barrier multilayer films
SEM images of the fracture surface of the PE/PE-EVOH/PE 3-layer
films with the PE/EVOH polymer blend content of 15% with and without the
compatibilizer was shown in Figure 3.16.
Fig.3.16. SEM images of the fracture surface of the PE/PE-EVOH/PE films
a) without PE-g-MAH; b) with 2% PE-g-MAH; c) with 4% PE-g-MAH
SEM image of the fracture surface of the PE/PE-EVOH/PE films
containing the PE-g-MAH compatibilizer showed that with 2% of the
compatibilizer, the phase separation between layers was still relatively clear,
(b) (a) (c)
13
but when the content of compatibilizer increased to 4%, it was difficult to
observe the division between layers, showing good adhesion between the
layers. It can be explained that the EVOH layer requires sufficient amount of
PE-g-MAH to develop covalent bond through the reaction between the
anhydride group of PE-g-MAH and hydroxyl groups of EVOH on the
interphase surface between LLDPE and EVOH.
3.2.1.1.2. Effect of PE-g-MAH compatibilizer content on mechanical
properties of PE/PE-EVOH/PE multuilayer films
Effect of PE-g-MAH content on the mechanical properties of PE/PE-
EVOH/PE multilayer films was shown in fig. 3.17.
Fig.3.17. Effect of PE-g-MAH content on the mechanical properties of
PE/PE-EVOH/PE films
The results showed that when adding 2% PE-g-MAH, the tensile
strength of the multilayer films decreased slightly, then the tensile strength
increased slightly when the PE-g-MAH content reached 4% and was almost
unchanged if the content of PE-g-MAH continues to increase. Thus, it can be
seen that PE-g-MAH had unsinificantly affect on the mechanical properties
of the PE/PE-EVOH/PE multilayer films.
3.2.1.1.3. Effect of PE-g-MAH compatibilizer content on oxygen
transmission rate (OTR), water vapor transmission rate (WVTR) of PE/PE-
EVOH/PE multilayer films
The effect of the PE-g-MAH content on the permeability of the PE /
PE-EVOH / PE multilayer film is summarized in Table 3.8.
Table 3.8. The oxygen and water vapor tranmisison rate of the PE/PE-
EVOH/PE multilayer films with different PE-g-MAH contents (15% of
PE/EVOH)
Transmission rate
The content of PE-g-MAH (%)
0 2 4 6 8
Oxygen transmission rate
(ml/m
2
.ngày)
3.01 3.22 3.26 4.58 5.64
Water vapor transmission
rate (g/m
2
.ngày)
6.87 6.85 6.89 6.86 7.01
400
450
500
550
600
650
10
15
20
25
30
35
0 2 4 6 8 E
lo
n
g
at
io
n
a
t
b
re
ak
(
%
)
T
en
si
le
s
tr
en
g
th
(
M
P
a)
PE-g-MAH content
Độ bền kéo đứt
Độ dãn dài khi đứt
Tensile stength
Elongation at break
14
The results showed that when the PE-g-MAH content increased from 0
- 4%, the oxygen transmission rate of the PE/PE-EVOH/PE film was almost
unchanged. However, at the PE-g-MAH content> 6%, the oxygen
transmission rate increased. The results also showed that the water vapor
transmission rate of the films was not affected by the PE-g-MAH content.
3.2.1.2. Effect of PE/EVOH polyme blend (layer 2) content on properties of
PE/PE-EVOH/PE multilayer films
To evaluate the effect of PE/EVOH polyme blend layer content on the
properties of the PE/PE-EVOH/PE multilayer film, PE/PE-EVOH/PE
multilayer film with PE-g-MAH compatibilizer content layer 1 and layer 3 of
4%, PE/EVOH polymer blend content of 5 – 20% were prepared.
3.2.1.2.1. Effect of PE/EVOH polyme blend content on mechanical properties
of PE/PE-EVOH/PE multuilayer films
Effect of the content of PE/EVOH polyme blend on the mechanical
properties of PE/PE-EVOH/PE multilayer films was summarized in table 3.9.
Table 3.9. Mechanical properties of PE/PE-EVOH/PE multilayer films
The content of
PE/EVOH layer (%)
Tensile strength
(MPa)
Elongation at break
(%)
5 32.3 680.3
10 31.4 661.7
15 30.5 624.8
20 29.8 605.5
Mechanical properties measurement results showed that tensile strength
and elongation at break of multilayer films decreased slightly when
increasing the content of PE/EVOH polymer blend. This was due to the
PE/EVOH polymer blend layer had much lower elongation at break than
LLDPE resin. Especially, EVOH is a copolymers with high crystallinity (58-
70%), so it is quite brittle and low elongation, so increasing their content lead
to reduce elongation at break of the multilayer film.
3.2.1.2.2. Effect of PE/EVOH polyme blend content on oxygen transmission
rate (OTR), water vapor transmission rate (WVTR) of PE/PE-EVOH/PE
multilayer films
Results of measuring oxygen and water vapor transmission rate of
multilayer films with different PE/EVOH polymer blend contents were
presented in Table 3.10.
The results showed that when the concent of PE/EVOH polymer blend
layer increased, the oxygen transmission rate of the multilayer films
decreased significantly. When the content of PE/EVOH polymer blend layer
from 5 - 15%, oxygen transmission rate decreased sharply and then decreased
insignificantly when the content of PE/EVOH polymer blend layer increased
to 20%. The water vapor transmission rate of PE/PE-EVOH/PE films
15
increased with increasing content of PE/EVOH blend layer. This is explained
by EVOH having -OH groups leading to its hydrophilic properties.
Increasing concentration of blend layer PE/EVOH means an increase in
EVOH content leads to an increase in the number of OH groups, making
them more hydrophilic.
Table 3.10. The oxygen and water vapor transmission of the PE/PE-
EVOH/PE multilayer films (4% PE-g-MAH)
Transmission rate
The content of PE/EVOH polymer blend (%)
5 10 15 20
Oxygen transmission rate
(ml/m
2
.ngày)
20.60 12.13 3.26 2.34
Water vapor transmission
rate (g/m
2
.ngày)
4.78 5.34 6.89 9.58
3.2.2. Study on preparation of PE/PA-EVOH/PE gas barrier multilayer films
3.2.2.1. Effect of PE-g-MAH compatibilizer content on properties of PE/PA-
EVOH/PE gas barrier multilayer films
To evaluate the effect of PE-g-MAH compatibilizer content in layer 1
and layer 3 on the properties of the PE/PA-EVOH/PE multilayer film,
PE/PA-EVOH/PE multilayer film with layer 2 (PA6/EVOH polymer blend)
accounted for 10% in volume, layer 1 and layer 3 (LLDPE/PE-g-MAH
polymer blend) accounted for 90% in volume were prepared. The PE-g-MAH
compatibilizer contents in layer 1 and layer 3 were 0-10%.
3.2.2.1.1. Effect of PE-g-MAH compatibilizer content on surface morphology
of PE/PA-EVOH/PE gas barrier multilayer films
SEM image of fracture surface of the PE/PA-EVOH/PE three layer
films with the PA6/EVOH polymer blend content of 15% with compatibilizer
was shown in Figure 3.19.
(a) Fracture surface of
film
(b) Fracture surface of
LLDPE/PE-g-MAH
polymer blend layer
(c) Fracture surface of
PA6/EVOH polymer
blend layer
Fig.3.19. SEM image of fracture surface of the PE/PA-EVOH/PE film with
4% PE-g-MAH compatibilizer
Observing the fracture surface of film (Figure 3.19a), it can be seen that
the interaction at the interface between the two phases is relatively good. This
is because in the molten extrusion state, on the surface between the
16
membranes there is a covalent bond between the carbonyl group of MAH in
PE-g-MAH and the amino group in PA6 and the hydroxyl group in EVOH.
This strong interaction lead to increased adhesion between LLDPE/PE-g-
MAH polymer blend layer and PA6/EVOH polymer blend layer.
3.2.2.1.2. Effect of PE-g-MAH compatibilizer content on mechanical
properties of PE/PA-EVOH/PE multuilayer films
Effect of the PE-g-MAH content on the mechanical properties of
PE/PA-EVOH/PE mulitayler films was shown in figure 3.20.
Fig.3.20. Effect of the PE-g-MAH content on the mechanical properties of
mulitayler films
The results showed that PE-g-MAH unsignificantly affected to the
tensile strength of the PE/PA-EVOH/PE multilayer films. The results also
showed that the elongation at break of the PE/PA-EVOH/PE multilayer films
increased slightly with the addition of PE-g-MAH and the elongation at break
increased when the PE-g-MAH content in film increased.
3.2.2.1.3. Effect of PE-g-MAH compatibilizer content on oxygen
transmission rate (OTR), water vapor transmission rate (WVTR) of PE/PA-
EVOH/PE multilayer films
The influence of the PE-g-MAH content on the permeability of the
PE/PA-EVOH/PE multilayer films is summarized in Table 3.11.
Table 3.11. The oxygen and water vapor tranmisison rate of the PE/PA-
EVOH/PE multilayer films with different PE-g-MAH content (10% of
PA6/EVOH)
Transmission rate
The content of PE-g-MAH (%)
0 2.5 5 7.5 10
Oxygen transmission rate
(ml/m
2
.ngày)
1.86 2.52 2.43 4.21 5.39
Water vapor transmission
rate (g/m
2
.ngày)
6.70 6.69 6.72 6.79 6.75
The results showed that the presence of PE-g-MAH increased oxygen
tranmisison rate. However, when the PE-g-MAH content increased from 2.5
to 5%, the oxygen tranmisison rate was almost unchanged. When the PE-g-
MAH content was > 5%, the oxygen tranmisison rate increased. The results
400
450
500
550
600
650
700
10
15
20
25
30
35
0 2,5 5 7,5 10
E
lo
n
g
at
io
n
a
t
b
re
ak
(%
)
T
en
si
l
st
re
n
g
th
(
M
P
a)
PE-g-MAH content
Độ bền kéo đứt
Độ dãn dài khi đứt
Tensile stength
Elongation at break
17
also showed a similar trend for the PE/PE-EVOH/PE multilayer films, PE-g-
MAH did not affect the water vapor tranmisison rate of the PE/PA-EVOH/PE
multilayer films.
3.2.2.2. Effect of PA6/EVOH polyme blend (layer 2) content on properties of
PE/PE-EVOH/PE multilayer films
To evaluate the effect of PA6/EVOH polyme blend layer content on the
properties of the PE/PA-EVOH/PE multilayer film, PE/PA-EVOH/PE
multilayer film with PE-g-MAH compatibilizer content layer 1 and layer 3 of
5%, PA6/EVOH polymer blend content of 5 – 20% were prepared.
3.2.2.2.1. Effect of PA6/EVOH polyme blend content on mechanical
properties of PE/PE-EVOH/PE multuilayer films
Effect of the content of PA6/EVOH polymer blend layer on the
mechanical properties of mulayer films was presented in table 3.11.
Table 3.11. The mechanical properties of multilayer films with different
PA6/EVOH polymer blend layer contents
The content of
PA6/EVOH layer (%)
Tensile strength
(MPa)
Elongation at break
(%)
5 30.7 560.4
10 34.1 520.8
15 35.2 512.7
20 35.7 508.6
The results in table 3.11 showed that the tensile strength of films
increased slightly when the polymer blend layer content increased from 10-
15%. When continuing to increase the content of polymer blend layer to
20%, the tensile strength is almost unchanged.
3.2.2.2.2. Effect of PA6/EVOH polyme blend content on oxygen transmission
rate (OTR), water vapor transmission rate (WVTR) of PE/PA-EVOH/PE
multilayer films
Results of measuring oxygen and water vapor transmission rate of
multilayer films with different PA6/EVOH polymer blend contents were
presented in table 3.13.
Table 3.13 The oxygen and water vapor transmission of the PE/PA-
EVOH/PE multilayer films (5% PE-g-MAH)
Transmission rate
The content of PA6/EVOH blend layer (%)
5 10 15 20
Oxygen transmission rate
(ml/m
2
.ngày)
4.54 2.43 1.69 1.32
Water vapor transmission
rate (g/m
2
.ngày)
5.6 6.72 8.1 11.1
The results showed that, when the content of blend layer (middle layer
thickness) increased, the O2 gas transmission rate decreased significantly. In
terms of water vapor transmission rate (WVTR), when the content of blend
18
layer increased, the WVTR increased slightly.
Compared with the PE/PE-EVOH/PE multilayer membrane with the
same middle layer content, it was found that the oxygen barrier ability of the
PE/PA-EVOH/PE films was better, or the oxygen transmission rate was
lower. This can be explained by the fact that PA6 has a much higher barrier
to oxygen than PE but less than EVOH. In contrast, the water vapor barrier
ability of PE/PA-EVOH/PE multi-layer films was less than that of PE/PE-
EVOH/PE films with the same middle layer content, because PA6 contains
polar amide groups, which are hydrophilic so its water vapor transmission
rate was higher.
General comment: it can be seen that with the same content of the
middle layer, the PE/PE-EVOH/PE multi-layer film has lower WVTR but
higher OTR as compared with PE/PA-EVOH/PE multilayer film. So,
depending on the purpose of use, choose the right film. According to some
studies, to make the gas barrier film, the OTR of the film must be ≤ 5
ml/m
2
.day and the WVTR of the film must be ≤ 8 g/m2.day. The results
showed that the PE/PE-EVOH/PE multilayer film with the PE/EVOH polymer
blend content of 15% and the PE/PA-EVOH/PE multilayer film with the PA-
EVOH polymer blend content of 5, 10 and 15% (signed PAEV-5, PAEV-10,
and PAEV-15, respectively) were unsatisfactory as gas barrier film.
3.3. Study on application of gas barrier multilayer films in the preservation
of some dry agricultural products
3.3.1. Study on application of gas barrier multilayer films in the preservation of
maize grain
Corn at 10.98% moisture content is packed into PAEV-10 bags, then
vacuumed on BZQ 500 machine (Maize-CK) (vacuum pressure -0.08MPa).
The control samples (without vacuum, Maize-T) were similarly conducted.
3.3.1.1. Effect of packaging conditions on maize quality
The changes in quality of maize grain under packaging conditions were
summarized in Table 3.15.
Table 3.15. The quality of maize grain under packaging condition during
storage
Quality
indicators
Samples
Time (months)
0 2 4 6 8
Moisture
content (%)
Maize-CK 10.98 10.96 11.04 11.09 11.18
Maize -T 10.98 11.30 11.64 11.95 12.05
Starch co
Các file đính kèm theo tài liệu này:
- study_on_the_manufacturing_and_properties_of_gas_barrier_mul.pdf