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공학석사 학위논문
Barrier Properties of
Thermotropic Liquid Crystalline
Polymer Blends
열방성 액정 고분자 블렌드의 차단 특성에 관한
연구
2018년 8월
서울대학교 대학원
재료공학부
정 승 윤
i
Abstract
Oxygen barrier properties of poly(m-xylene adipamide) (MXD6)
were enhanced by blending with different ratios of Vectra B950 (VB),
a thermotropic liquid crystalline polymer. Blend sheets were
prepared with extrusion without a compatibilizer, and the sheets were
biaxially extended to form films. Thermal stability of the blends was
improved with VB content. From the differential scanning calorimetry
thermograms of the blends, it was concluded that the blends are
incomaptible and crystallization occurred during extension. VB
phases were spherical according to the scanning electron microscopy
images of the samples. Tensile strength decrement with VB content
was low compared with other non-compatibilized blend systems,
which means that interfacial adhesion between MXD6 and VB phases
exists. Oxygen permeability of the samples decreased with VB
content. The results of unextended and extended samples fits well
with the Maxwell model, which is a permeation model of composite
consisting of spherical impermeable phases. Oxygen permeability of
the extended films is lower than that of unextended sheets due to the
enhanced barrier properties with elongation.
Keyword: polymer blend, oxygen permeability, Maxwell model,
transmission rate, extension
Student Number: 2016-24557
ii
Table of Contents
Chapter 1. Introduction ............................................................ 1 1.1. Introduction ........................................................................... 1
1.2. Background Information ....................................................... 5 1.2.1. Permeation Theory ............................................................... 5
1.2.2. Tortuosity of Composites ..................................................... 7
Chapter 2. Experimental Section ............................................. 9 2.1. Materials ............................................................................... 9
2.2. Sample Preparation ............................................................... 9
2.3. Characterization .................................................................. 12 2.3.1. Thermogravimetric Analysis (TGA) .................................. 12
2.3.2. Differential Scanning Calorimetry (DSC) ........................... 12
2.3.3. Scanning Electron Microscopy (SEM) ................................ 12
2.3.4. Tensile Test ....................................................................... 13
2.3.5. Oxygen Permeability .......................................................... 13
Chapter 3. Results and Discussion ........................................ 14 3.1. Thermal Degradation .......................................................... 14
3.2. Thermal Behavior ............................................................... 17
3.3. Morphology ......................................................................... 24
3.4. Mechanical Properties ........................................................ 28
3.5. Oxygen Permeability .......................................................... 33
Chapter 4. Conclusion ............................................................ 35
Bibliography ........................................................................... 37
Abstract in Korean ................................................................ 41
1
1. Introduction
1.1. Introduction
Materials with high barrier properties are widely demanded as
packaging materials of foods, medicine and medical supplies, or
industrial supplies. For such materials polymers have suitable
features such as ease of process, excellent flexibility, transparency,
and low cost. These characteristics are also important for next-
generation organic light emitting diode (OLED) displays since flexible
materials should be used as substrates and encapsulators of flexible
OLED displays instead of currently used rigid materials such as glass.
OLEDs are much more vulnerable to oxidation than other kinds of
displays[1], hence polymers with low oxygen permeability are being
required.
However, oxygen permeability of commonly used polymers such
as polyethylene (PE) or poly(ethylene terephthalate) (PET) is much
higher than that of inorganic materials such as aluminum or silicon
oxide[2-4]. Oxygen permeability values of common polymers are
listed in Table 1.1. Numerous studies have been conducted to
improve barrier properties of such polymers, and one of the methods
is extension[3, 5]. Extension results in ordering of polymer chains
and reduction of free volume and thus barrier properties are
improved. Qureshi et al. presented that extended PET has inferior
2
oxygen permeability compared to unextended PET. They ascribed
such phenomenon to a structural transition of amorphous PET to two
phases: a dense, impermeable, and ordered phase; and a loose,
permeable, and isotropic phase[6]. Liu et al. described the drawing
effect in another way. By comparing oxygen permeability of
uniaxially extended PET, poly(ethylene naphthalate), and
copolymers based on PET; and unextended ones, both oxygen
diffusivity and solubility were concluded to be decreased with
increasing draw ratio, and especially solubility showed linear
increase with specific volumes of the polymers. They explained that
such phenomenon shows the formation of one-phase densified glass
during extension instead of that of two phases, and is caused by
decrease of free volume[7].
Another method is to form a blend with a polymer of better
barrier properties. Hu et al., Prattipati et al., and Özen et al. improved
barrier properties of PET and poly(ethylene terephthalate-co-
isophthalate) by blending with relatively impermeable poly(m-
xylene adipamide) (MXD6) or adipamide/isophthalamide copolymer.
They also conducted biaxial extension and additionally reduced
oxygen permeability[8-10]. Jang and Lee identified as well that
oxygen permeability of polypropylene/poly(vinyl alcohol) blends
decreases with increasing draw ratio[11]. Flodberg et al. lowered
oxygen permeability of PE and PET by forming a blend with poly(p-
hydroxybenzoic acid-co-2-hydroxy-6-naphtoic acid) (Vectra
A950), which is a highly impermeable thermotropic liquid crystalline
polymer(TLCP)[12-14].
3
Polymer blends have some advantages compared to other
polymer composites such as ease of manufacturing and processing.
In this study, MXD6 was coextruded with different amounts of Vectra
B950 (VB) which is a greatly impermeable copolyesteramide TLCP,
and polymer blends of varied concentration were manufactured to
lower the oxygen permeability of MXD6. The two polymers were
selected because of structural similarity: both have benzene rings and
peptide bonds, hence despite the lack of a compatibilizer interfacial
adhesion was expected to exist and therefore the blends were able
to be extended well. The blends were biaxially extended to achieve
superior barrier properties. Thermal and mechanical properties and
morphology of the samples were measured, and they were related
with oxygen barrier properties of the samples by applying
permeation theory.
4
Barrier polymer Oxygen permeability
(㎖·㎜/㎡·day·atm)
Vectra B950 0.006
Vectra A950 0.014
Vectra A950 0.03
Vectra RD501 0.016
Vectra RD802 0.019
Vectra L950 0.01
Vectra V100P, V200P, V300P 0.017-0.047
PVDC 0.015-0.25
EVOH 0.0041-0.061
Nylon MXD6 0.25
High nitrile resins 0.3
Cellophane 0.5
PEN 0.8
PET, oriented 1.6
PVC 3.1
Nylon 6 2
HDPE 59
PP 82
LDPE 218
PS 102
PC 102
Table 1.1. Oxygen permeability values of various polymers[3, 15-
17].
5
1.2. Background Information
1.2.1. Permeation Theory
When a gas permeant crosses over a material, it goes through
two processes: solution on the surface and diffusion through the
barrier material. Thus the permeability coefficient (𝑃) is a product of
diffusion coefficient (𝐷) and solubility coefficient (𝑆)[18].
𝑃 = 𝐷𝑆
To obtain the permeability, transmission rate should be measured
in advance. For instance, oxygen transmission rate (OTR) can be
evaluated with Mocon Ox-Tran instrument following ASTM D3985
method. Its diagram is described in Figure 1.1. Gas transmission rate
value varies with time, so it is a function of time, 𝐽(𝑡). According to
Fick’s second law, 𝐽(𝑡) equals to the formula below[8, 9]:
𝐽(𝑡) =𝑃𝑝
𝑙{1 + 2 ∑(−1)𝑛exp (−
𝐷𝜋2𝑛2𝑡
𝑙2)
∞
𝑛=1
}
(𝑝: pressure, 𝑙: thickness).
If one desires to determine either 𝐷 or 𝑆, 𝐽(𝑡) graph should be
thoroughly obtained. On the other hand, 𝑃 can be calculated with
steady-state permeant flux value 𝐽∞ (𝑡 → ∞)[8].
𝐽∞ =𝑃𝑝
𝑙
Therefore permeability coefficient is a multiplication of
transmission rate at equilibrium and barrier thickness divided by gas
pressure (𝑃 =𝐽∞𝑙
𝑝).
6
Figure 1.1. Diagram of Mocon Ox-Tran apparatus[3].
7
1.2.2. Tortuosity of Composites
Composites containing impermeable agents have different
diffusion properties compared with pure materials. Permeants have
to detour the impermeable sections and diffusivity decreases owing
to tortuous diffusion paths. Tortuosity varies with the shape of
impermeable phases as explained in Figure 1.2.
By introducing tortuosity factor ( 𝑓 ), how much diffusion is
obstructed can be calculated. If the diffusivity of a pure material
without the impermeable agents is 𝐷0, the diffusivity of a composite
𝐷 can be expressed as
𝐷 =𝐷0
𝑓 [18].
If the impermeable agents are spherical, Maxwell’s model can
predict tortuosity factor:
𝑓 =1 +
𝜙2
1 − 𝜙
where 𝜙 is volume fraction of the impermeable agents[19]. This is
accurate only if 𝜙 < 0.1.
In the case of solubility, if the solubility of impermeable agents
is 0,
𝑆 = 𝑆0(1 − 𝜙)
where 𝑆 is the solubility of the composite and 𝑆0 is the solubility of
the pure material. Therefore the permeability of the composite can
be calculated as
𝑃 = 𝐷𝑆 =𝐷0
𝑓⋅ 𝑆0(1 − 𝜙) [18].
8
Figure 1.2. Tortuosity difference depending on the shape of
impermeable agents[20].
9
2. Experimental Section
2.1. Materials
The polymers used in the experiment were a polyamide, MXD6,
and a TLCP, Vectra B950 (VB), which is a random copolyesteramide
of 2,6-hydroxynaphthoic acid (60%), terephthalic acid (20%), and
aminophenol (20%). MXD6 pellets (grade S6007) were supplied by
Mitsubishi Gas Chemical, Inc. VB pellets were supplied by Hoechst
Celanese Co. Chemical structures of MXD6 and VB are shown in
Figure 2.1.
2.2. Sample Preparation
Pellets were dried in vacuo for 24 hours and mixed in weight
ratios of 100/0, 95/5, 90/10, and 80/20 (MXD6/VB). The mixed
pellets were extruded through a twin screw extruder (Hankook E.M
Ltd. STS32HSS-44-4SF) which was equipped with a T-die, and
MXD6 and polymer blend sheets of approximately 0.5 mm thickness
were formed. Rotation speed of the screws was 100 rpm, and
extrusion temperatures are listed in Table 2.1.
The extruded sheets were biaxially extended at 80 ℃ and
polymer blend films were formed. The draw ratio was 2 × 2, and the
draw speed was 200 %/min.
10
⒜
⒝
Figure 2.1. Chemical structures of ⒜ MXD6, ⒝ VB.
11
⒜
⒝
⒞
Table 2.1. Extrusion temperatures of ⒜ 100/0, ⒝ 95/5 and 90/10,
and ⒞ 80/20 samples.
Feeder Zone 1 Zone 2 Zone 3 Zone 4 Zone 5
165 ℃ 220 ℃ 230 ℃ 235 ℃ 240 ℃ 245 ℃
Zone 6 Zone 7 Zone 8 Adapter Die
245 ℃ 250 ℃ 250 ℃ 245 ℃ 245 ℃
Feeder Zone 1 Zone 2 Zone 3 Zone 4 Zone 5
175 ℃ 240 ℃ 250 ℃ 255 ℃ 255 ℃ 265 ℃
Zone 6 Zone 7 Zone 8 Adapter Die
270 ℃ 270 ℃ 265 ℃ 260 ℃ 250 ℃
Feeder Zone 1 Zone 2 Zone 3 Zone 4 Zone 5
180 ℃ 245 ℃ 255 ℃ 260 ℃ 260 ℃ 270 ℃
Zone 6 Zone 7 Zone 8 Adapter Die
275 ℃ 275 ℃ 270 ℃ 265 ℃ 255 ℃
12
2.3. Characterization
2.3.1. Thermogravimetric Analysis (TGA)
TGAs of 100/0, 95/5, 90/10, 80/20, and 0/100 (pure VB)
samples were conducted with Mettler Toledo TGA/DSC 1 under
nitrogen atmosphere. Thermal degradation behaviors of the
unextended sheet samples were observed. The samples were heated
up to 550 ℃ with a heating rate of 10 ℃/min.
2.3.2. Differential Scanning Calorimetry (DSC)
Thermal analyses were conducted with Mettler Toledo DSC823e.
Pure MXD6 and VB pellets, the unextended sheet samples, and the
extended film samples were heated up to 300 ℃ with a heating rate
of 10 ℃/min, and after 5 minutes of isothermal environment at
300 ℃, they were cooled down to 25 ℃ with a cooling rate of -
5 ℃/min. Then the samples were heated up again to 300 ℃ with a
heating rate of 10 ℃/min to obtain 2nd heating curves. 2nd heating
curves were used in analysis to eliminate thermal history.
2.3.3. Scanning Electron Microscopy (SEM)
Fractured surfaces of the polymer blend sheets and films were
observed with JSM-7600F field emission scanning electron
13
microscope. The samples were fractured inside liquid nitrogen in
both machine direction (MD) and transverse direction (TD), and then
coated with platinum before observation. Pictures of 100/0 sheet and
film with 1000 magnification, and blend sheets and films with 5000
magnification were obtained.
2.3.4. Tensile Test
Mechanical properties of the unextended sheet samples were
measured with Instron-5543 universal testing machine. Specimens
which were made to be extended in MD and TD with dimensions of 2
㎝ × 10 ㎝ were tested. Elongation speed was 1 ㎝/min.
2.3.5. Oxygen Permeability
Barrier properties of the sheet and the film samples were
investigated by measuring oxygen permeability of them. OTR was
measured with Mocon OX-TRAN Mode 2/21 tester. Measurement
was conducted at 23 ℃, 0 % relative humidity, and 1 atm pressure.
The measured transmission rates were multiplied with the
thicknesses of the samples and divided with the pressure to obtain
oxygen permeability values.
14
3. Results and Discussion
3.1. Thermal Degradation
TGA curves are represented in Figure 3.1. It is certain that VB
is more thermally stable than MXD6, but it is quite hard to distinguish
the order of thermal stability of MXD6 and blend samples. Hence the
temperatures at which the samples lost 50% of their weight were
found and are provided in Table 3.1. The 50% reaching temperatures
increase with VB proportion, which means thermal stability is
improved by blending with VB.
15
Figure 3.1. TGA thermograms of the blends.
16
MXD6/VB 50% weight loss temperature(℃)
100/0 411.35
95/5 412.583
90/10 414.502
80/20 418.655
Table 3.1. Temperatures at which the samples lost 50% of weight.
17
3.2. Thermal Behavior
Thermal behaviors of the samples were investigated with their
DSC thermograms. The thermograms of pure MXD6 and blend sheets
and a pure VB pellet are provided in Figure 3.2 and 3.3, and the
results are shown in Table 3.2. In the heating and cooling curves of
the blends there is no presence of peaks corresponding to VB
because of relatively low ∆𝐻𝑚 and ∆𝐻𝑐 values of VB compared to
those of MXD6.
The glass transition temperature (𝑇𝑔) of pure MXD6 is 87 ℃, and
that of VB is 134 ℃. If MXD6 and VB are miscible, the 𝑇𝑔s of the
blends should be higher than 87 ℃[21], but actually they are all
87 ℃. This result coincides with the 𝑇𝑔 change of uncompatibilized
poly(ether imide) (PEI)/VB blends studied previously[22].
Therefore the blends are concluded as an immiscible system due to
absence of a compatibilizer. The melting temperatures (𝑇𝑚) of MXD6
are also not affected by VB content due to immiscibility.
Crystallization temperatures (𝑇𝑐) are obtained from cooling scans.
Although the 𝑇𝑐 of VB is higher than MXD6, the 𝑇𝑐s of the blends
decrease with VB content. This means that VB does not act as a
nucleating agent, and hinders the movement of MXD6 chains.
Crystallinity (𝜒𝑐) of the samples were calculated with
𝜒𝑐 =Δ𝐻𝑐
Δ𝐻𝑚0
where Δ𝐻𝑚0 is enthalpy of melting of 100% crystalline polymer and
Δ𝐻𝑐 is enthalpy of crystallization of the sample. Δ𝐻𝑚0 of pure MXD6
18
is 175 J/g[23], and Δ𝐻𝑚0 of the blends were calculated by multiplying
weight fraction of MXD6 and 175 J/g. Δ𝐻𝑐 measured from DSC
thermograms and calculated 𝜒𝑐 values are presented in Table 3.3.
Crystallinity of the films are higher than that of the sheets at every
ratio. This means that crystallization of both pure MXD6 and blends
occurred during stretching.
Figure 3.4 is a 2nd heating curve of an MXD6 pellet. A significant
difference with that of pure MXD6 sheet is an exotherm peak at
156 ℃, which is the cold crystallization peak. Therefore it can be
inferred that cold crystallization of MXD6 occurs nearby 156 ℃.
19
Figure 3.2. 2nd heating curves of sheets samples and a VB pellet
(0/100).
20
Figure 3.3. Cooling curves of sheet samples and a VB pellet
(0/100).
21
MXD6/VB 𝑇𝑔 (℃) 𝑇𝑐 (℃) 𝑇𝑚 (℃)
100/0 87 195 236
95/5 87 192 237
90/10 87 190 237
80/20 87 187 236
0/100 134 228 281
Table 3.2. 𝑇𝑔, 𝑇𝑐, and 𝑇𝑚 of sheet samples and a VB pellet (0/100).
22
Figure 3.4. A 2nd heating curve of an MXD6 pellet.
23
MXD6/VB Sheet Film
Δ𝐻𝑐 (J/g) 𝜒𝑐 (%) Δ𝐻𝑐 (J/g) 𝜒𝑐 (%)
100/0 46.22 26 66.41 38
95/5 45.40 27 58.40 35
90/10 51.98 33 63.01 40
80/20 33.98 24 43.62 31
Table 3.3. Δ𝐻𝑐 and 𝜒𝑐 of sheet and film samples.
24
3.3. Morphology
Figures 3.5, 3.6, and 3.7 are the SEM images of the samples. The
circular distinguished regions which can be identified in the images
of the blends are VB phases. It can be noticed that the phases are
nearly spherical from the images. In addition, the phases are flatter
in MD than TD. This is because the sheets went through a pair of
rollers right after they were extruded from a T-die to be formed in
uniform thickness.
Also the phases got larger as VB content increased, which means
that aggregation occurred in blend formation because of low
compatibility. High compatibility results in finer phase size. Seo et al.
observed that the size of TLCP phases in a nylon 46/VB binary blend
is larger than that in a nylon 46/VB/maleic anhydride grafted
ethylene-propylene-diene terpolymer (MA-EDPM) ternary blend
in which MA-EDPM acted as a compatibilizer, and thus has poorer
dispersion[24].
By comparing the images of unextended and extended samples,
it can be concluded that the phases were barely deformed during
extension since the temperature of extension was much lower than
the 𝑇𝑔 of VB.
25
⒜ ⒝
Figure 3.5. SEM images of cross section of ⒜ 100/0 sheet in MD
(1000×), ⒝ 100/0 sheet in TD (1000×).
26
⒜ ⒝
⒞ ⒟
⒠ ⒡
Figure 3.6. SEM images of cross section of ⒜ 95/5 sheet in MD
(5000×), ⒝ 95/5 sheet in TD (5000×), ⒞ 90/10 sheet in MD
(5000×), ⒟ 90/10 sheet in TD (5000×), ⒠ 80/20 sheet in MD
(5000×), ⒡ 80/20 sheet in TD (5000×).
27
⒜ ⒝
⒞ ⒟
⒠ ⒡
Figure 3.7. SEM images of cross section of ⒜ 95/5 film in MD
(5000×), ⒝ 95/5 film in TD (5000×), ⒞ 90/10 film in MD, ⒟
90/10 film in TD (5000×), ⒠ 80/20 film in MD (5000×), ⒡ 80/20
film in TD (5000×).
28
3.4. Mechanical Properties
Young’s modulus, elongation at break, and tensile strength of
the samples were calculated. The results are represented in Figures
3.8, 3.9, and 3.10. All the specimens were fractured brittlely and
weren’t deformed plastically. Young’s modulus increases and
elongation at break decreases with VB content in both MD and TD.
This is due to the high stiffness of VB: it has much higher Young’s
modulus and lower elongation at break than MXD6[15].
Tensile strength diminished with VB content although VB has
higher tensile strength. Such phenomenon results from low interfacial
adhesion between the two phases; however comparing with a
previous study which investigated mechanical properties of biaxially
drawn PEI/VB blend (VB 10wt%), tensile strength decrement of
MXD6/VB blend system is lower than that of PEI/VB blend system,
whose tensile strength of hoop direction decreased to nearly a half
compared with that of pure PEI[25]. This means that hydrogen bonds
formed between the peptide bonds of MXD6 and VB results in a little
interfacial adhesion.
Trends of mechanical properties in MD and TD didn’t differ
from each other, which means that aspects of alteration of
microstructure in both directions are identical, as seen in previously
presented SEM images. However the values are different―Young’s
modulus, tensile strength, and elongation at break in MD are higher
than those in TD―owing to two reasons: first, VB phases are a little
29
flatter in MD, which means that VB phases are slightly aligned in MD;
second, variation of thickness of the TD specimens was much higher
than that of MD specimens. Thickness values used in calculation were
the average values of three points of the specimens: top, middle, and
bottom. Therefore the thickness values used in calculation must have
been different from the real thickness values of the fractured point,
and actually it is probable that the real value is lower than the average
value. This difference resulted in lower Young’s modulus, tensile
strength, and elongation at break values of TD specimens. Also, the
more VB content induces more aggregation of VB phases in MD.
30
Figure 3.8. Variation of Young’s modulus of MD and TD specimens
with VB content.
31
Figure 3.9. Variation of tensile strength of MD and TD specimens
with VB content.
32
Figure 3.10. Variation of elongation at break of MD and TD
specimens with VB content.
33
3.5. Oxygen Permeability
OTRs of the samples were measured and permeability values
were calculated. The results are represented in Figure 3.11.
Permeability of the blend sheets and films decreased as proportion
of impermeable VB increased.
VB phases are spherical as observed in SEM images, so the
results can be compared with Maxwell model. Weight fraction values
were converted to volume fraction values with density values of
MXD6 and VB, which are 1.22 and 1.40 g/㎤, respectively[26, 27].
Although VB is not totally impermeable to oxygen, its diffusivity and
solubility were regarded as 0 in calculation because its permeability
value is very low when compared with MXD6 (𝑃VB
𝑃MXD6⁄ = 0.024).
Maxwell model well predicts the permeability of sheets and films.
Errors of both sheet and film are maximum at 80/20, 8.65 % and
12.51 %, respectively, which is because of limitation of Maxwell
model; its accuracy is guaranteed only if 𝜙 < 0.1.
Permeability of the extended films is lower than that of
unextended sheets. Such phenomenon resulted from increment of
crystallinity of MXD6, which was above-mentioned.
34
Figure 3.11. Permeability values of unextended sheets and
extended films, and values calculated from Maxwell model.
35
4. Conclusion
In this study, oxygen permeability of MXD6 was improved by
blending with VB which is a highly oxygen-impermeable TLCP.
Blend sheets with 100/0, 95/5, 90/10, and 80/20 weight fraction of
MXD6/VB were formed by extrusion without any compatibilizer, and
then biaxially extended to form films. Thermal and mechanical
properties and morphology of the samples were measured, and they
were related with oxygen barrier properties of the samples by
applying Maxwell permeation theory.
Thermal stability of the sheets increased with VB content due to
high thermal stability of VB. 𝑇𝑔s and 𝑇𝑚s of MXD6 contained in the
blends were independent with VB content, which means the two
polymers are incompatible. Also from the cooling thermograms of the
samples, it can be inferred that crystallinity increased during
extension.
SEM images were used to observe VB phases of the samples.
The phases were nearly spherical, and barely deformed during
extension, but the degree of deformation was low compared to other
studies which conducted extension[8, 9]. This is because extension
temperature was lower than the 𝑇𝑔 of VB.
By analyzing mechanical properties of the unextended sheets, it
can be inferred that interfacial adhesion between the two phases
exists in spite of absence of a compatibilizer, and there is no
36
remarkable difference between MD and TD.
Oxygen permeability of the unextended and extended samples
fits well with the estimated values of Maxwell model as the
impermeable TLCP phases were spherical. Because of the limitation
of the model itself, error of the model was maximum at 80/20.
Oxygen permeability of the extended samples were lower than that
of unextended samples, which was a result of additional
crystallization.
Barrier properties of the blend can be enhanced if the VB phases
were deformed a lot to be flatter to ten or more times such as other
studies[8, 9]. Such phenomenon is possible if the extension
temperature is nearby the 𝑇𝑔 of VB, but in this system MXD6 starts
cold crystallization at that temperature. Since crystallized regions of
a polymer is not able to be deformed, the sheets were all torn during
extension at high temperatures. Thus in a polymer blend system of
which the 𝑇𝑔 s are lower than the 𝑇𝑐𝑐 s of both polymers barrier
properties can be highly enhanced.
37
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41
초 록
폴리(m-자일렌 아디프아마이드) (MXD6)를 열방성 액정 고분자인
벡트라 B950 (VB)과 서로 다른 비율로 블렌딩하여 산소 차단 특성을
향상시켰다. 상용화제의 사용 없이 압출을 통해 블렌드 시트를 제작하였
고, 이후 이 시트들을 이축 연신하여 필름을 제작하였다. VB 함량이 늘
어남에 따라 블렌드의 열적 안정성은 증가하였다. 블렌드의 시차 주사
열량계의 온도 기록도로부터, 블렌드는 상용성이 없으며 연신 중 결정화
가 일어났다는 결론을 내릴 수 있었다. 주사형 전자 현미경 사진에 따르
면 VB 상은 구형이었다. 인장 강도의 VB 함량에 따른 감소량은 다른
상용화제를 미사용한 블렌드 계에 비해 낮았는데, 이는 MXD6와 VB 상
간의 계면 접착력이 존재한다는 것을 의미한다. 시료의 산소 투과도는
VB 함량에 따라 감소했다. 연신하지 않은 시료와 연신한 시료의 투과도
값은, 구형 불투과성 상을 포함하는 합성물에 적용 가능한 맥스웰 모델
의 예상치와 잘 맞아 떨어졌다. 연신한 시료의 투과도는 연신하지 않은
시료의 투과도보다 낮았는데, 이는 연신 과정에서 발생한 차단 특성의
향상에 의한 결과이다.
주요어: 고분자 블렌드, 산소 투과도, 맥스웰 모델, 전달 속도, 연신
학 번: 2016-24557
Chapter 1. Introduction1.1. Introduction1.2. Background Information1.2.1. Permeation Theory1.2.2. Tortuosity of Composites
Chapter 2. Experimental Section2.1. Materials2.2. Sample Preparation2.3. Characterization2.3.1. Thermogravimetric Analysis (TGA)2.3.2. Differential Scanning Calorimetry (DSC)2.3.3. Scanning Electron Microscopy (SEM)2.3.4. Tensile Test2.3.5. Oxygen Permeability
Chapter 3. Results and Discussion3.1. Thermal Degradation3.2. Thermal Behavior3.3. Morphology3.4. Mechanical Properties3.5. Oxygen Permeability
Chapter 4. ConclusionBibliographyAbstract in Korean
5Chapter 1. Introduction 1 1.1. Introduction 1 1.2. Background Information 5 1.2.1. Permeation Theory 5 1.2.2. Tortuosity of Composites 7Chapter 2. Experimental Section 9 2.1. Materials 9 2.2. Sample Preparation 9 2.3. Characterization 12 2.3.1. Thermogravimetric Analysis (TGA) 12 2.3.2. Differential Scanning Calorimetry (DSC) 12 2.3.3. Scanning Electron Microscopy (SEM) 12 2.3.4. Tensile Test 13 2.3.5. Oxygen Permeability 13Chapter 3. Results and Discussion 14 3.1. Thermal Degradation 14 3.2. Thermal Behavior 17 3.3. Morphology 24 3.4. Mechanical Properties 28 3.5. Oxygen Permeability 33Chapter 4. Conclusion 35Bibliography 37Abstract in Korean 41