4.classification of polymer 3-6new clean tepe.ppt
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1. Addition-Condensation system1.1 Addition polymerization (แบบการเติม) 1.2 Condensation polymerization (แบบควบแน่น)
2. Chain growth-Step Growth System
2.1 Chain growth polymerization (แบบลกูโซ)่2.2 Step growth polymerization (แบบขัน้)
Classification(3): polymerization methods
1.2 Condensation polymerization (แบบควบแน่น)
Part of the monomer molecule is kicked out when the monomer becomes part pf the polymer.
The part that gets kicked out is usually a small molecule like water (H2O), or HCl gas
1.1 Addition polymerization (แบบการเติม)
1. Addition-Condensation system
Monomer molecules become part of the polymer without kicking any molecules out.
2. Chain Growth-Step Growth System
monomers become part of the polymer one at a time.
2.1 Chain growth polymerization (แบบลกูโซ)่
2.2 Step growth polymerization (แบบขัน้)
monomer + monomer = dimerdimer + monomer = trimerdimer + dimer = tetramertrimer + dimer = pentamern-mer + m-mer = (n+m)mer
or
Two short chains can react to form longer chain
Chain-Growth (or addition) polymerization
nn
monomer polymer
C = C
H
H H
H
C C
H
H
H
Hn
When ethylene is polymerized to make polyethylene, the every atom of the ethylene
molecule becomes part of the polymer (none gained, none lost)
Ethylene Polyethylene
Example:
In General;Addition Polymerization = Chain Growth Polymerization - do not give off by product - monomers become part of the polymer one at a time• ประกอบด้วยขัน้ตอนต่างๆ 3 ขัน้ตอน และมกีารใชส้ารเคม ี
2 ชนิด 1. initiation ขัน้เริม่ต้นปฏิกิรยิา 1. monomer 2. Prapagation ขัน้ดำาเนินไปของปฏิกิรยิา 2. initiator 3. termination ขัน้สิน้สดุปฏิกิรยิา
Free radical Anionic -Cationic +
1.Monomer – Becomes repeating units in polymer
chains– Monomer need to have at least
1double bond 2. Initiator
- add into monomer to activate joining of monomers into long polymer chains
Functions of the 2 basic chemicals
There are 3 types of chain growth
polymerizations:
• Free radical polymerization (Free radical
initiator I)
• Anionic polymerization (Anionic initiator I-)
• Cationic polymerisation (Cationic initiator I+)
(names depend on type of initiator)
Free radical polymerizationInitiator• peroxide (ROOR, HOOH)• Azo compound (-N=N-) easily decompose into
2 free radicals when exposed to heat
H3C – C
CH3
CN
N N+ + C - CH3
CH3
CN
C – O – O - C
O O+
O
C – O O - C
O
O
C – O
O
CO
+
H3C – C – N = N – C - CH3
CH3 CH3
CN CN
1. Initiation step
Free radical จะกระตุ้นใหพ้นัธะคู่ในโมโนเมอรแ์ตกออก แล้วเกิดพันธะใหม่ขึ้น
C = C
H
H H
H
C C
H
H
H
H
2. Propagation Step
Free radical ท่ีปลายจะไปกระตุ้น monomer ตัวท่ีอยูใ่กล้คียงใหพ้นัธะคู่แตกออก Monomer ตัวท่ีเหลือจะเข้าต่อท่ีปลายในลักษณะเดียวกันไปเรื่อยๆ
C C
H
H
H
H
C = C
H
H H
H
C C
H
H
H
H
C C
H
H
H
H
C C
H
H
H
Hn
ขัน้การสิน้สดุของปฏิกิรยิา ม ี3 แบบ :1. Coupling: Mx + My Mx+y
2. Disproportionation: Mx + My Mx + My-1
3. Chain transfer agent:
3. ขัน้สิน้สดุปฏิกิรยิา (Termination step)
-C = CH H
C
H
H
+Cl – C – Cl
Cl
Cl
C – Cl
H
H
+ Cl – C
Cl
ClInitiate another chain
Anionic polymerization (I-)Initiator CH3 – CH2 – CH2 – CH2 - Li
butyl lithium
CH3 – CH2 – CH2 – C + Li+CH3 – CH2 – CH2 – CH2 - Li
H
H
-
1.ขัน้เริม่ต้นปฏิกิรยิา (Initiation step I-)
CH3 – CH2 – CH2 – C Li+
H
H
-C = C
H
H H
H
CH3 – CH2 – CH2 – CH2 - C Li+
H
H
-
2. ขัน้ดำาเนินไปของปฏิกิรยิา (Propagation Step II.)
CH3 – CH2 – CH2 – CH2 - C Li+
H
H
- + C = C
H
H H
H
CH3 – CH2 – CH2 – CH2 - C – C – C Li+
H
H
-
H H
H H
C C
H
H
H
Hn
-
Living anionic polymerization
Living polystyrene
butadiene
Living styrene-butadiene block copolymer
Here A stands for the initiator fragment end groups. Sometimes it’s a butyl group from butyl lithium, sometimes it isn’t.
- A – A – A – A – A – A – A – A – B – B – B – B – B – B – B - B
Block copolymer
Cationic polymerisation (I+)
+ +
+ +
1.ขัน้เริม่ต้นปฏิกิรยิา (Initiation step I+)
+ +
-
Initiator: AlCl3/H2O
AlCl3/H2O
2. ขัน้ดำาเนินไปของปฏิกิรยิา (Propagation Step)
n
Step-Growth (Condensation) Polymerization
In General;Condensation Polymerization = Step Growth Polymerization - give off by product - monomers become part of the polymer one at a time or two short chain react to form longer chain
H + H2O
acid alcohol ester
เอสเทอรร์ฟิเิคชนั (esterification)
monomer ท่ีใชต้้องมหีมูฟ่งัก์ชนัอยา่งน้อย 2 หมู่
diacid dial
polyester
PET
+n H2O
The first thing the two monomers will react to form a dimer.
Terapheyl chloride Ethylene glycol
ester dimer
2-mer + 2-mer = 4-mer
+ HCl
monomer + monomer = 2-mer2-mer + monomer = 3-mer2-mer + 2-mer = 4-mer3-mer + dimer = 5-mern-mer + m-mer = (n+m)mer
Nylon 6,6
This Cl atom and this H atom don’t end up in the polymer, they split off to form HCl gas.
+ N-CH2-CH2-CH2-CH2-CH2-CH2-N
H
HH
HCl-C-CH2-CH2-CH2-CH2-C-Cl
O O
nylon 6,6
adipoyl chloride hexamethylene diamine
HCl+ C-CH2-CH2-CH2-CH2-C-
O O
N-CH2-CH2-CH2-CH2-CH2-CH2-NHH
n
In a condensation polymerization, some atoms of the monomer don’t end up in the polymer.
HCl+ C-CH2-CH2-CH2-CH2-C-
O O
N-CH2-CH2-CH2-CH2-CH2-CH2-NHH
n
When nylon 6,6 is made from adipoyl chloride and hexamethylene diamine, the chlorine atoms from the adipoyl chloride, each along with one of the amine hydrogen atoms, are expelled in the form of HCl gas.
+ N-CH2-CH2-CH2-CH2-CH2-CH2-N
H
HH
HCl-C-CH2-CH2-CH2-CH2-C-Cl
O O
One example is the polymerization which produces polyurethane.There are also addition polymerization which are step growth polymerizations.
Isocyanate groups
a diisocyanate a diol
Not only monomers react, but also dimers, trimer, and so on. This makes it a step growth polymerization.Also, because no small molecule by-products are produced, it is an addition polymerization.
เอกสารประกอบจาก ดร.ธนาวดี ล้ีจากภัย MTEC
Conclusion• Chain growth polymerization: generally =
addition polymerization : monomer become part of the polymer one at
a time.– Polymer chain grows rapidly to a long size as soon as
the initiation step starts.– High molecular weight polymer is formed immediately.– monomer concentration decreases as the number of
high polymer molecules increase– the reaction mixture contains-monomer, high-
molecular weight polymer, growing chain
• Step growth polymerization: generally = condensation polymerization
: Two short chains can react to form longer chain.– monomer disappears much faster– molecular weight increase through out the
course of the reaction– high molecular weight polymer is not
obtained until the end of the reaction
Conclusion
Ref: S.L. Rosen, John Wiley & Sons 1993
Classification(4): Architecture of ChainEach structures respond to solvents differently.• Linear and Branched Polymers – can be soluble in suitable solvents
Linear polymers Branched polymers
HDPELDPE
LLDPE
• Crosslink polymers –Heavily crosslinked not soluble and not swell
ex. Ebonite bowling ball – no swelling
–Lightly crosslinked not soluble but swell in solvent
Classification(5): Number of repeating unit present in the polymer chains
• homopolymer (PE, PP, PS, PVC, PMMA, PC, PET),
• copolymer (SBR, NBR),
• terpolymer (ABS)
Different types of copolymers
—xoxoxoxoxoxoxo—Alternating copolymer
—xxoooxoxooxxxox—Random copolymer
—xxxxxooooooxxxx—Block copolymer
—xxxxxxxxxxxxxxxxxxxxxxxxx— o o o o o o o o o o o o o o Graft copolymer Graft copolymer
โคโพลิเมอรท่ี์มคีารบ์อนเป็นโครงสรา้งหลัก
(Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)
(Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)
Classification(6): orientation of polymer chains(Morphology)
• Amorphous
• Semi-crystalline
Polymer
Thermoplastic Elastomer Thermoset
Semi-Crystalline Amorphous
( lightly cross linked) (heavily cross linked )Network
Cross linked polymers
Linear/branched polymers(no cross linked)
T
% crystallinity~70%
Tg
Tm
Viscous melt
Hard&StrongBrittle
rubbery
Leathery ductile
Influence of molecular weight on properties of polymers
( Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)
Chapter 4:
Orientations and Crystallinity of Polymers
Orientation of Polymer Chains
1. Connection of chain (Configurational features) - Geometric details of how each repeat unit adds to the growing chain
- Occur during polymerization process (cannot change by rotation)
2. Rotation and twisting of chain (Conformation)- rotation of backbone or side group
Factors affecting Crystallinity of Polymers
Factors that affect properties of polymers1. Architectural features2. MW and MWD3. Configurational features4. Stereoregularity (conformation)
1. Architectural features:- Branching- Cross linking- Nature of copolymer
2. Molecular weight (MW), Molecular Weight Distribution (MWD):
Polymers with long chain and narrow molecular
weigth distribution more crystallinity
High MW
Low MWDEasily crystallized
3. Configurations: Geometric details of how each repeat unit adds to the growing chain affect properties of polymers
- Head to Head
- Head to Tail (normal arrangement)
- Tail to Tail
“Head to tail”
“Head to Head”/“Tail to Tail”
Configuration: cannot be changed by rotation of the backbone.
4. Stereoregularity—rotation around the backbone
• Rotation of Cn-Cn+1 bond• Gauche positive (g+)• Trans (t) [lowest potential energy—most probable]• Gauche negative (g-)
• Cis-Tran Isomer for C=C
Trans conformation: all backbones lie in the same plane-planar zigzag plane
- Rotation of side group- isotactic- syndiotactic- atactic (Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)
(rotation of backbone or side groups)- Rotation of backbone
•Gauche positive (g+)•Trans (t) •Gauche negative (g-)
potential energy of each conformation
Trans conformation
(Ref: A. Kumar and R.K. Gupta, McGraw-Hill 1998)
Rotation of Cn-Cn+1 bond
Cis-Trans Isomer(Rotation of Cn=Cn+1 bond)
Poly (cis-1,4-isoprene) Poly (trans-1,4-isoprene)
Rotation of side groups (Stereoisomerism)Ex. Repeat unit.
Ref.: L.H. Sperling, John Wiley & Sons, Inc. (1992)
Requirement for crystallinity– Need ordered regular chain structure (syndiotactic+isotactic)– The 2nd forces holding chains > disorder effect of thermal
energy
“Anything that reduces the regularity of backbone reduces the crystallinity.”
• Ex. PE, PP are crystalline polymers copolymer of PP/PE is amorphous
“There is no complete crystalline polymers”% crystallinity – show fraction of crystal structure inside polymers
1. The Fringed Micelle Model
2. Folded-Chain model
Models for Crystal Formation
3. Folded-Chain model
Tie molecules
Crystal Growth
Ref.: L.H. Sperling, John Wiley & Sons, Inc. (1992)
Ref.: L.H. Sperling, John Wiley & Sons, Inc. (1992)
Steps of Spherulite Formation
Spherulite (cont.)
Ref: R.J. Young and P.A. Lovell, Chapman&Hall 1991
Spherulites
Spherulites grow radiallyfrom a point of nucleationuntil other spherulites are encountered.
XRD patterns of Amorphous and Semi-crystalline Polymers
Ref: R.J. Young and P.A. Lovell, Chapman&Hall 1991
Size: size of spherulites can be controlled by the number of nuclei present. (normally dia. ~ 0.01 mm)
No. Nucleation site Size of spherulites
How to enhance transparency and reduce brittleness?Add nucleating agents
Quench polymers (increases nucleation sites)
or
Spherulite (cont.)
Effect of Crystallinity on Mechanical Properties
• more crystallites
– Ex: (density) > >
branching < < % crystalline > >
• Degree of crystallinity: สมการ amorphous + crystalline
• Branching: more branching less crystallinitya
ccc
aa
cc )w1(www1
HDPE LLDPE LDPE
Tacticity crystallinity optical properties
Atactic -->mostlyAmorphous polymers transparent
Isotactic mostly crystalline polymers
Syndiotactic
/refractive index of phase amorphous = phase crystalline transparent
Ex1: Foam ex. Foamed PS เป็นสขีาวทึบเพราะแสงผ่านเฟส PS และgas bubblesEx2: high-impact PS เป็น PS ท่ีมอีนุภาค polybutadiene rubber ขนาด 1-10 m.
กระจายอยูใ่น amorphous PS
Size of crystallites < wavelength of visible light transparent
Low degree of crystallinity fairly transparent
Effect of crystallinity on optical properties
Basic concept: เมื่อขนาดของอีกเฟสหนึ่งมขีนาดใหญ่กวา่
light passes btw. two phases ความยาวคล่ืนของแสงเกิดการหกัเหทึบแสง
w/ different refractive indices เมื่อขนาดของอีกเฟสหนึ่งมี
ขนาดเล็กกวา่ ความยาวคล่ืนของ
แสงไมเ่กิดการหกัเหโปรง่แสง
LightPasses through
Light scatters.
Liquid Crystalline Polymers
• Molecules that show a degree of order in the liq. Phase– If liq. Phase is solution lyotropic LCP– If liq. Phase is melt thermotropic LCP
• is self reinforced composite
• Ex. (lyotropic) Kevlar เป็น aromatic polyamid (“aramid”) with repeating unit
pull into fibers in the solution of H2SO4
use for bullet-proof vests (เสื้อเกราะกันกระสนุ)
Ex. (thermotropic LCP)
Note: liq. Crystalline polymers have highly aromatic backbone inhibit rotationstiff, rigid extended chain
Xydar
Vectra
Extended chain crystal
• When pulled polymer will align in the flow direction crystallize (extended chain crystal)
(the more you pull, the stronger it becomes)
Stretching Curve and Crystal Orientation
Crystal Orientation with Stretching
XRD ring with Stretching