4. Model of Crystallites (Morphology)

Transcription

1 4. Model of Crystallites (Morphology) 4. Model of Crystallites (Morphology) Packing: arrangement of chain in crystals 1) Fringed micelle model 2) Folded chain model: - single crystal - spherulite - unit cell 3) Other morphologies

2 4. Model of Crystallites (Morphology) Chapter 5 4. Model of Crystallites (Morphology) Packing: How to polymers crystallize? (arrangement of chain in crystals) arranged 3-dimensionally in a crystal described in terms of unit cell and its contents ordered, regular strong secondary force vs thermal energy (H-bonding, dipole moment)

3 4. Model of Crystallites (Morphology) Chapter 5 4. Model of Crystallites (Morphology) * CH 2 CH 2 * nm - Contour length: x 2 x 10,000 = µm - Extended length: ~2.5 µm - Exptal length: 52.9 nm - thickness of crystallites: ~10 nm or 0.01 µm

4 4. Model of Crystallites (Morphology) Chapter 5 1) Fringed micelle model 1) Fringed micelle model 결정 비결정 - Coexistance of crystal/amorphous structures - Greater X c with orientation

5 4. Model of Crystallites (Morphology) Chapter 5 2) Folded chain model 2) Folded chain model Lc La lamellar surface tie molecule Left: Historic representation of the structure of fringed micelles. Right: Random coils composed of chain folds and short, coiled segments in fold micelles.

6 4. Model of Crystallites (Morphology) Chapter 5 2) Folded chain model 2) Folded chain model ( 가 ) Single crystal (lamellar crystal) - Grown in very dilute polymer solution (<0.1%, 1953) - Not believed due to complexities introduced by coil nature of chain - dimension of crystallites - reentry model ~10 µm 100Å

7 Single crystals or linear PE grown in dilute solution

8 screw dislocation TEM of fold micelles of PE

9 Truncated lozenges of PE grown by the self-seeding six sectors

10 4. Model of Crystallites (Morphology) Chapter 5 4. Model of Crystallites (Morphology) Dimension ~10 µm Thickness: 100~200 Å (50~60C atoms) Folding: 5 atoms in direct reentry model Chain axis flat surface of crystal Lamellar face or basal plane 100 ~ 200Å Chains are folding back

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12 4. Model of Crystallites (Morphology) Chapter 5 2) Folded chain model Reentry model

13 Model of Chain Folding Chapter 5 (a) adjacent re-entry with sharp folds (b) adjacent re-entry with loose folds (c) random re-entry or switch-board model

14 Imperfection Chapter 5 4. Model of Crystallites (Morphology)

15 2) Folded chain model fold length various lengths L c Addition of an infinitely long chain molecule to the side plane of a lamella of folded chain molecules. The extended chain segments of the added chain have various lengths L c ; the cross-sectional area of the added chain is L d L b.

16 2) Folded chain model The increase of long period with Tc for poly(4-methylpentene-1) precipitated from 0.1% solution in xylene.

17 Solvents: :phenol : furfuryl alcohol : m-cresol, : benzyl alcohol, : acetophenone 2) Folded chain model Solvent Effect (a) Dependence of lamellar thickness, ι, upon T C for polyoxymethylene (b) Master curve for all the data in (a) plotted against the reciprocal of the supercooling.

18 Lamellar thickness, ι 2) Folded chain model isothermally melt-crystallized PE

19 4. Model of Crystallites (Morphology) Chapter 5 4. Model of Crystallites (Morphology) ( 나 ) Spherulite: - grown from melt or concentrated solution (> 1%) - aggregate of lamellar crystallites into super-molecular structure - Maltese cross pattern

20 4. Model of Crystallites (Morphology) Chapter 5 4. Model of Crystallites (Morphology) ( 나 ) Spherulite: Radial growth up to 10 µm Amorphous region between radial arms Twisted and branched growth of ribbon like lamella heterogeneous nuclei no vs. spherulite size branch to fill the space tie molecules

21 4. Model of Crystallites (Morphology) 4. Model of Crystallites (Morphology) grown from concentrated solution (> 1%) or melt Ref. Young p

22 Polarized microscopic image of the spherulitic structure in PP

23 Fracture surface (LN 2 ) of it-pp isothermally grown at 110 o C for 5 hr after cooling from 250 o C

24 Chain folding in fold micelles Chapter 5 X-ray long periodicity R: regular lamellae with sharp folds and crystal defects by chain ends and dislocations. L: loose loops with adjacent re-entry. S: Switch-board with distant re-entries (leads to an unacceptable density at the lamellar surface).

25 Tie Molecules Chapter 5 Boundary region between spherulite grown at 95. in a polyethylene fraction, MW = 726,000.

26 Tie Molecules Chapter 5 Lateral intercrystalline links between islands of polyethylene grown from 50% solution in n-c 32 H 66.

27 Schematic illustration of the leading edge of a lath-like crystal within a spherulite

28 Oriented or Drawn Polymers Chapter 5 (a) Interlamellar amorphous model for an oriented polymer showing a considerable amount of lateral cohesiveness to the lamellae and the oriented amorphous regions. (b) Fibrils in crystalline polymers drawn to a very high draw ration.

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30 Unit Cell

31 polymer film spherulite 50 to 500 µ crystal lamella lamella 20 to 60 nm unit cell

32 Unit Cell of PE

33 Arrangement of chains in the unit cell of PE

34 Orthorhombic crystal lattice of PE

35 Crystal Systems

36 4. Model of Crystallites (Morphology) Chapter 5 3) Other morphologies 3) Other morphologies: a) chain-extended crystal b) shish-kebabs c) hedrite d) dendrite, etc

37 a) Chain extended crystal Chapter 5

38 b) Shish kebab morphology Chapter 5 produced by stirring a 5% xylene solution of PE at 510 rpm and 104.5

39 Molecular model of the shish kebab morphology

40 Model morphology of the shish-kebab

41 4. Model of Crystallites (Morphology) Chapter 5 3) Other morphologies P effect 압출 결정화증가 Fully extended chain Stress (Stirring): crystallized under stress Shish-kebob Shish: extended polymer chain Kebob: lamellar (chain folding)

42 c) Hedrites Chapter 5 SEM of polyethylene grown from supercritical propane solution.

43 d) Sheaf-like crystal Chapter 5 Sheaf-like multilayer crystals of polyethylene observed suspended in xylene before collapse. Phase contrast.

44 Optical Microscope under Crossed Polarizer Chapter 5 RT, X50 PEO Film from melt PEO Film from solution

45 편광현미경사진 (RT, X200) Chapter 5 [EO]/[LiClO4] = 4 :

46 편광현미경사진 (RT, X200) Chapter 5 [EO]/[LiClO4] = 4 : 1 80 and then air cooled to 40 (X200)

47 편광현미경사진 (RT, X200) Chapter 5 [EO]/[LiBF4] = 4 : 1 60

48 Effect of Low MW Additive (RT, X200) [EO]/[LiBF 4 ] = 4 : 1 + PPG (26 phr; MW = 400) [EO]/[LiBF 4 ] = 4 : 1 + PPG(66 phr; MW = 425)

49 Hierarchy in Polymer Crystal

50 5. Annealing Chapter 5 5. Annealing - The process of crystal improvement by heating below T m (T g < T < T m ) - At T > T c : remelting and recrystallization Fold period increase holes 생성 (Swiss cheese effect) Molecular mobility in melt as well as solid state chain folding with high degree of order Extensive conformation change during crystallization

51 Single crystal of linear PE crystallized from perchloroethylene solution, then annealed for 30 min. at 125, 10 below T m. The fold period increased from about 100 À to almost 200 À during annealing.

52 Solution-grown PE lamellae developing holes (but only in regions where layers did not overlap) after annealing on a substrate at 118 for 5 min.

53 (a) at 218 (b) at 220 Successive stages in the thickening of solution-grown lamellae of poly(4- methylpentene-1) after annealing on a substrate in air for 5 min. Note in (a) the tendency to create holes parallel to <110> and to start thickening at or near crystal edges. The sector boundaries have become prominent in (b).

54 6. Factors affecting Crystallization & T m Chapter 5 6. Factors affecting Crystallization & T m 1) Homopolymers a) 동력학적요인 b) 열역학적요인 structural effect chain flexibility effect of spacing between polar groups effect of bulkiness of side group branching effect MW effect 2) Copolymers??

55 6. Factors affecting Crystallization & T m Chapter 5 6. Factors affecting Crystallization & T m Boyer-Beaman rule for homopolymers T g /T m = 0.5 ~ 0.75 (or 0.8) (in K) Asymmetric Symmetric along the main chain T m PVC: 0.78 PS: 0.75 PE: 0.5 PVdF: 0.48 T g

56 6. Factors affecting Crystallization & T m Chapter 5 1) Homopolymers growth rate a) 동력학적요인 유동성 T 결정안정성 6. Factors affecting Crystallization & T m T effect if T c > T m : too mobile max crystallization rate T: Tc,max ~ 90%Tm regular linear polymer: high rate P effect induced orientation of molecules (fully extended chain up to 10 µ) stress effect (stirring) row nucleated structure (shish kebob)

57 6. Factors affecting Crystallization & T m Chapter 5 6. Factors affecting Crystallization & T m b) 열역학적요인 Regularity and symmetry (Structural effect): Regularity 저분자 : 순도에의해결정 고분자 : cf. random copolymer

58 6. Factors affecting Crystallization & T m Chapter 5 6. Factors affecting Crystallization & T m Symmetry para-: 대칭성 and 강도 /T m 섬유 (PET), film ortho-, meta-: 대칭성 and 강도, T m coating, adhesive

59 6. Factors affecting Crystallization & T m 6. Factors affecting Crystallization & T m Chain flexibility mobility Rigidity, T m Flexibility, T m O C O CH 2 CH 2 O

60 Tm dependence of Polyester on p-phenylene Groups

61 6. Factors Affecting Crystallization & T m Chapter 5 6. Factors affecting Crystallization & T m Effect of spacing between polar groups Polyamide * NHC * n O Hydrogen bond T m O Polyurethane * NHC O * n Polarity 감소 Polyester O * C O * n

62 Tm trend in Homologous Series of Aliphatic Polymers

63 Tm dependence on Spacing of Polar Groups

64 6. Factors Affecting Crystallization & Tm 3) Prediction of T m polyamides polyoxides poly(α-olefin) polyesters number of methylene group per repeating unit

65 Substituent Effect on Tm Chapter 5 Poly (α-olefin) Crystals

66 6. Factors affecting Crystallization & T m Chapter 5 6. Factors affecting Crystallization & T m Effect of bulkiness of side group * CH 2 CH * X n CH 3 CH 2 CH 3 T m V f 증가 CH 2 CH 2 CH 3 75 CH 2 CHCH 2 CH 3 CH CH 3 CH 2 CCH 2 CH 3 Bulky side chain 350 CH 3

67 6. Factors affecting Crystallization & T m Chapter 5 6. Factors affecting Crystallization & T m Effect of branching Effect of MW

68 슈퍼엔지니어링플라스틱 내열성과기계적특성이우수 150 C 이상에서장시간사용가능한열가소성수지 PPS, LCP, PEEK, 내열PA, PI를중심 2008년: 현재 8000톤, 820억원 ( 연평균 20.8% 의고성장 )

69 6. Factors affecting Crystallization & T m 6. Factors affecting Crystallization & T m 2) Copolymers and Polyblends

70 6. Factors Affecting Crystallization & T m 6. Factors affecting Crystallization & T m 3) Effect of Copolym. and Plasticization on lowering of Xc, Tm and Tg

71 Transition T and End-Use T 6. Factors affecting Crystallization & T m Class T use Characteristics Amorphous & structural Polymers Semi-crystalline & oriented polymers Highly semi-crystalline & oriented polymers Tough, leather-like polymers < Tg glass-like rigidity Tg < < Tm Tm -100 moderate rigidity high degree of toughness fibers ~ Tg leather Elastomer (rubber) > Tg high, local segmental mobility