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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