Chapter 15-2

Chapter 15-2

- more tightly packed in the crystalline than in the amorphous areas.

∙ Crystalline polymers have two-phase systems with a crystalline phase dispersed in an amorphous matrix - mostly opaque,

∙ 일반적으로 amorphous polymer (무정형 고분자) 는 transparent 하다. 예로써 a-PS, polycarbonate (PC), PMMA 등

∙ Determination of crystallinity (i) density measurement

φ = c

a c

a

ρ ρ

ρ ρ

−

− (φ = volume fraction of crystalline material) c

여기서 ρ = density of the sample

ρ = " amorphous polymer a

ρ = " crystalline polymer c

Wc =

) (

) (

a c

a c

ρ ρ ρ

ρ ρ ρ

−

−

(W_c = weight fraction of crystalline material) (ii) melting enthalpy (enthalpy of fusion)

x =

)

% 100

( crystalline polymer Hf

H_sample Δ

Δ

- polymer 의 ∆H 는 DSC (differential scanning calorimeter) 즉 시차 주 사 열분석기를 이용하여 측정한다.

- 100 % crystalline polymer 의 ∆H 는 polymer handbook 등 관련 문헌 에 잘 나타나 있으며, 고분자의 결정 즉, single crystal 의 ∆H 를 주로 측정한다.

(iii) x-ray 를 이용함,

x =

a c

c

I I

I +

여기서 x = degree of crystallinity (결정화도),

I_c = intergrating the intensities of crystalline reflections • Market and use of PE

(i) HDPE : used in blow molded containers, pipes (flexible, tough, corrosion resistant), (see Fig. 12.9)

(ii) LDPE : film, injection molding 용, wire and cable (see Fig. 12.8) (iii) LLDPE : film, 식품용 포장재 등

┏ HDPE : high viscosity ┣ LDPE : low "

┗ LLDPE : midium "

• Melt Flow Index (MFI 또는 MI) - measure of extent of polymerization,

즉 분자량을 나타내는 척도로서 공장에서 많이 사용함

• Polypropylene :

isotactic polypropylene (i-PP) 은 crystallinity 가 a-PP 보다 높다. d = 0.90 ∼ 0.915 (g/cm³) T_m = 170℃

- good electrical, chemical resistance, toughness, high abrasion resistance, (즉 내마모성이 좋다)

• Polyvinylchloride : (PVC),

- vinyl chloride monomer (VCM) is polymerized by using a free radical initiator,

( CH ₂ CH ) _n CH ₃

( CH ₂ CH ) _n

Cl