Handout Teknologi Polimer

Teknologi Polimer Tinggi - Handout

TEKNOLOGI POLIMER TINGGI

PENDAHULUAN

Polimer dari kata :

Poli : banyak

Meros : bagian yang terulang

Produksi komersial untuk beberapa polimer

Bahan Polimer Tahun Tempat

1. Selulosa nitrat 1870 USA

2. Selulosa asetat 1985 Jerman

3. Polistiren (PS) 1930 Jerman

4. Polimetil metakrilat (PMMA) 1934 Inggris

5. PVC 1933 Jerman, USA

6. LDPE (Low Density Polietilen) 1939 Inggris

7. Poliamida (PA Nylon) 1939 USA

8. PTFE 1950 USA

9. Akrilonitril-Butadiena-Stiren (ABS) 1952 USA

10. PETP 1953 USA

11. HDPE (High Density Polietilen) 1955 Jerman

12. Polipropilen 1957 Italia

13. Polikarbonat (PC) 1959 Jerman, USA

14. LLDPE (Linear Low Density Polyetilen) 1977 USA

15. Fenol Formaldehid (PF) 1909 USA

16. Urea Formaldehid 1926 Inggris

17. Melamin Formaldehid 1938 Jerman

18. Poliuretan (PUR) 1943 Jerman

19. Epoksi (EP) 1947 USA

20. Karet Alam (vulkanisasi) 1839 Inggris, USA

21. SBR (Stiren Butadiena Rubber) 1937 Jerman

22. Akrilonitril-Butadiena 1937 Jerman

SBR = karet sintetis styrene butadiene rubber

Semula polimer disebut makro molekul.

Jurusan Teknik Kimia, Fakultas Teknik, Universitas Gadjah Mada 1


Polimer >< monomer

monomer

Istilah polimer dikemukakan oleh Staudinger

Polimer alam : = selulosa C6H10O5 - C6H10O5 - -

= karbohidrat

= karet alam

= protein

Polimer sintetis : = polistiren, polietilen

Dilihat dari rantainya :

1. Linier

H H H H

C = C C – C – C - C -

H H H H

Etilen polietilen

H H H H

C = C – C = C -C – C = C – C-

H H

Butadiena

2. Jaring (network)

Monomer karet alam : isoprene (punya ikatan rangkap, divulkanisasi, ikatan rangkap terbuka,

senyawa S masuk dan terikat dalam rantai).

Termoplastik

Polimer yang apabila dipanaskan akan melunak/meleleh.

Bila dididinginkan akan kembali ke bentuk semula.

Polimer ini mengandung ikatan linier.

Termosetting

Polimer yang apabila dipanaskan akan tetap padat dan suatu saat akan rusak.

Mempunyai struktur rantai jaring

Senyawa organik jika dipanaskan pada suhu tinggi >>> terjadi cracking (ikatan putus) atau disebut

pirolisis (rusak pada suhu tinggi).



Plastik-thermoplastics :

polyethylene PE

polypropylene PP

polystyrene PS

polyvinylchloride PVC

polyacetate POM

acrylic PMMA

polyamine (nylon) PA

polycarbonate PC

polytetrafluorethylene PTFE

Plastik-thermosetting :

epoxy EP

melamine-formaldehid MF

urea-formaldehid UF

unsaturated polyester UP

phenol-formaldehyde PF

alkyd

polyurethane PUR

Elastomers :

natural rubber NR

styrene-butadiene rubber SBR

polybutadiene BR

buthyl rubber HR

polychloroprene CR

synthetis polyisoprene IR

nitrille NBR

silicone rubber

Reaksi polimerisasi

Polimerisasi adisi

H2 H2 H2 H2

C = C + C = C - C – C – C – C –

Polimerisasi kondensasi

Penggabungan 2 molekul kecil menjadi molekul besar dengan hasil samping molekul sederhana.

O O

- C – OH + HO- - C – O - + H2O

HOOC —— OH + HOOC —— OH HOOC —————— OH

Reaksi etilen oksid :

O O O



C – C — C – C + HO – OH C – C — C – C – O – OH

H2 H H H2 OH

Sifat : polimer kondensasi

Reaksi : polimerisasi adisi

Derajat polimerisasi (DP) = degree of polymerization simbol x atau n

H2 H2 H2 H2

C = C + C = C (- C – C - ) (- C – C - ) x = derajat polimerisasi

H2 H2 H2 H2 ( CH2 – CH2 ) n

O

HO(-C - ~~~) n H n besar polimer

n kecil oligomer

O O

H-(O-C - ~~~) n OH -O – C - ~~~ >>> repeating unit

Gugus fungsional : -OH

-COOH Gugus yang bereaksi

-C=C-

-NH2

Formation of linear-branched chains :

Linear formation chain

+

Branched chain (network polymer) formation

+

Polimerisasi adisi :

bersifat chain reaction

Reaksinya cepat



Pembukaan ikatan rangkap (mengaktifkan ikatan rangkap)

Polimerisasi kondensasi :

Bersifat step reaction

Reaksinya lebih lambat

Reaksinya berhenti saat kehabisan gugus fungsional

Reaksinya satu per satu

POLI KONDENSASI

Poliester

Asam ftalat + etilen glikol : HOOC COOH + HO-CH2- CH2-OH

(Terephtalic acid)

HOOC COO-CH2-CH2-OH + H2O

HOOC ——————————OH

HOOC——— OH + HOOC ———— OH HOOC ——— OH + H2O

Pada reaksi dihampakan agar reaksi bergeser ke kanan (H2O menguap karena hampa)

Jika terjadi perubahan fasa menjadi padat maka reaksi akan berhenti (molekul tak dapat bergerak)

PET serat poliester

Dietilen glikol HO-CH2-CH2-O-CH2-CH2-OH

Untuk serat lebih kuat : HOOC COO-CH2-CH2-OH

Poliamida

Asam adipat + heksametilendiamin :

HOOC-CH2-CH2-CH2-CH2-COOH + H2N-(CH2)6-NH2

HOOC-(CH2)4-C-N-(CH2)6-NH2 + H2O

O H

Supaya reaksi bergeser ke kanan, pada pertengahan reaksi dihampakan.

2 HOOC ———— NH2 HOOC ———— NH2 + H2O

Nylon 66 (senar)

Caprolactam caproic acid

H2 H2 H2

C – C – C

CH2 CH2 + H2O H2N-(CH2)5-COOH



HN —— C=O → Nylon 6 (serat)

O H

HOOC C-N NH2 Kevlar : serat dengan kekuatan = kekuatan serat baja

O O

Cl-C C-Cl

Polimer dari Formaldehid

O

formaldehid H2CO atau H – C – H

1. Fenol Formaldehid

a. Adisi

OH OH H CH2OH

+ CH2O

mono metilol fenol

b. Kondensasi

OH OH OH OH CH2OH H CH2OH -CH2- -- CH2-

+ + H2O

OH OH Bentuk lain : -CH2- -CH2- -CH2 -

– OH

CH2

OH

Fenol formaldehid: untuk alat-alat elektronik >> termosetting

>> untuk lem >> tahan air

Fenol murni: padat >> titik leleh + 50oC >> putih

Fenol (karbol): coklat >> teroksidasi oleh udara >> PCB >> coklat >> fenol teknis

2. Urea Formaldehid

a. Adisi

HNH HN-CH2-OH



C=O + CH2O C=O

HNH HNH

Monometilol urea

Urea : gugus fungsional >> 2 NH2 >> potensial mengikat 4 formaldehid

b. Kondensasi

HN-CH2OH HN-CH2OH HN-CH2-N-CH2-N-

C + C C=O C=O C=O

NH2 NH2 NH2 NH2 NH2

Memungkinkan terbentuk polimer jenis jaring.

Urea formaldehid >> untuk lem multiplek (triplek).

Pabrik plywood biasanya mempunyai pabrik urea formaldehid sendiri.

Urea formaldehid >> putih >> kurang tahan terhadap air.

3. Melamin

>> bening seperti kaca >> mahal

NH2

C

N N >>> mempunyai 6 gugus fungsional

H2N-C C-NH2

N

Adisi dari monometilol melamin sampai dengan heksa metilol melamin.

REAKTIVITAS TETAP

O

A. H(CH2)nCOOH + C2H5OH HCl H(CH2)nC-OC2H5

B. HOOC-( CH2)nCOOH + C2H5OH HCl

r = k.CCOOH.COH

Konstanta kecepatan reaksi k, (grek/L)-1(det)-1 pada 25oC

Panjang rantai (n) kA x 10 4 kB x 10 4

1 22,1 -

2 15,3 6,0



3 7,5 8,7

4 7,4 8,4

5 7,4 7,8

6 - 7,3

7 -

8 7,5

9 7,4

>9 7,6

R-COOH + R’-OH R-COO-R’ + H2O

A B E W

r = k1CACB – k2CECW

Reaksinya digeser ke kanan dengan cara menghilangkan airnya sehingga CW << 0

r = k1CACB

r = kCCOOHCOH

= k0CkatCCOOHCOH

= k0CH+CCOOHCOH >>> r = k’CCOOHCOH

k’Jika dibuat CCOOH = COH = C, makar = k’C2

Kemudian dibuat grafik :

1/(1-p)

waktu (t)Contoh :

Asam adipat + etilen glikol

r = k0CH+ CCOOHCOH

-COOH –COO - + H+

Dibuat CH+ ~ CCOOH Tidak akan sama benar karena ada konstanta disosiasi



Jika tidak mengabaikan konstanta disosiasi

CCOOH = COH

r = k’CCOOH CCOOH.CCOOH

Konstanta disosiasi tidak diabaikan:

Kemudian dibandingkan antara order 3 dengan order 5/2 ternyata order 5/2 lebih cocok

1/(1-p)2

t

Berat molekul

1 2 3 ...........................x

monomer : repeating unit = N0

setelah reaksi = N

derajat polimerisasi = x



N0 = N x

dengan N = N0(1-p) maka :

; xn : rata-rata jumlah

analog dengan Berat Molekul

BM rata-rata jumlah (number average)

Ni : jumlah total : N

Mi : berat molekul

( fraksi mol)

BM rata-rata berat (weight everage)

>>>> >>>> Wi = Wtotal

Berat Molekul z average

xn sama untuk kedua polimer, tetapi distribusi BM berbeda

(jenis polimer sama, tapi cara membuat polimer berbeda)

Derajad polimerisasi untuk jumlah gugus fungsional tidak sama

A – A + B – B dimana NAo < NBo

Extent of reaction A = p

NA = (1-p) NAo


x

Ni


NB = NBo – p NAo

Bila : NB = NAo ( 1/r – p )

Saat reaksi, jumlah rata-rata = ½ (NA + NB)

Bila reaksi sempurna p 1

Maka

Contoh : Poliesterifikasi (reaksi keseimbangan)

p p 1- p

1/(1-p)

1 2 3 .......................... x

Misal p reaksi = 40 % >>> probabilitas yang bereaksi = 0,4

Secara statistik, probabilitas x-mer:

Nx = px-1 (1-p)



Distribusi Berat Molekul (derajad polimerisasi) Rantai Linear

Mol fraksi : Nx = px-1(1-p)

Jumlah molekul polimer N = N0 (1-p)

Jumlah x-mer Nx = Npx-1 (1-p)

Nx = N0 (1-p)2 px-1

Nx p=0,95

p=0,98 p=0,99 x

Fraksi berat

= x (1-p)2 px-1

Bila A tidak sama dengan B dan reaksi sempurna p=1

Wx = x r (x-1)/2 (1-r)2 / (1 + r )

Wx p=0,90

p=0,95

p=0,98

p=0,99

x

Rantai cabang (network)

: branching coefficient A

: fraksi yang bercabang ( A –A , A ) terhadap total gugus A

A

Perbandingan jumlah gugus fungsional r = NA/NB

= rpA2 / [1-rpA2(1-)]

= pB2/ [1-pB2(1-)]

Nilai kritis :

= 1/(f-1) >>> pada saat terjadi gel (gel point)

Derajad polimerisasi (xn)



.....A A.....

A – A + B – B A – ( B-BA-A)2-B-BA

A .....A A......

A

A

Carothers

tidak hanya untuk yang bercabang

Equimolar :

Non – Equimolar :

Untuk membuat bahan termosetting gel jangan sampai terjadi / harus dihindari

Gel point : xn = ~ pc = ........

A

A + B –B

A

1 mol = 3 grek 1,5 mol = 3 grek

Distribusi berat molekul dalam 3 dimensi (dalam fraksi berat)

Untuk masing-masing monomer mempunyai gugus fungsional f :

RING FORMATION

R – C = O ring



HO-R-COOH O

H(-OR-CO-)n-OH linier

Kecepatan pembentukan

Ring/siklis r = k1C

Linier r = k2C2

Stoll, Rouve’ dan Stoll-Comte

Siklis (k1)

HO(-CH2)n-2 – COOH

Linier (k2)

4

3

2

log C 1

0

-1

-2

4 6 8 10 11 12 13 14 16 18 20 n

Pada n=9 , nilai C minimum

n < 4 tidak mungkin membentuk siklis

POLI ADISI

C = C - C – C – C – C –

Chain reaction :

Initiation (pemicuan)

M Maktif

Propagation (perambatan)



M + Maktif MMMaktif

Spontan dan terjadi rantai yang sangat panjang

Termination

Monomer aktif (Maktif ) mati karena bertumbukan rantai sudah panjang

Reaksi poliadisi :

1. Mekanisme radikal

2. Secara ionik (kationik, anionik)

3. Koordinasi

ad) 1. Mekanisme Radikal

Initiation >> peroxide

I kd 2R*

Initiator yang sering digunakan : Benzoyl peroxide (pecah karena panas)

O O

-C – O —— O – C - COO * * + CO2

Initiator yang dipilih :

yang mudah bereaksi

yang mudah membentuk radikal

Cara initiation/cara pembentukan radikal :

dengan initiator

dengan radiasi

dengan initiator yang pecahnya karena radiasi lebih aman karena lebih awet

disimpan.

Selanjutnya R* + M RM*

Contoh : CH3 CH3

R* + H2C = C R – CH2 – C*

CH3 CH3

Propagation

RM* + M kp RMM* RMx* + M kp RM*

x+1

Termination

Mx+y (terminasi secara coupling)



Mx* + My

*

Mx + My (disproporsionasi)

Keduanya kehilangan radikal

Initiator yang lain :

Azobis Isobutyronitrile (AIBN) >> pecah karena panas.

CH3 CH3 CH3 CH3

NC – C – N = N——C – CN NC – C * + N2 + *C – CN

CH3 CH3 CH3 CH3

Initiation

ra = ka [R*][M] dengan f : faktor efisiensi

Propagation

RM* + M kp RMM* rp = kp[M*][M]

RMx* + M kp RM*

x+1

Termination

RMxMyR

RMx* + RMy

* rt = 2 kt [M*]2

RMx + RMy

Konsentrasi radikal tetap

>>>>> ri = rt

2 f kd [I] = 2 kt [M*]2

[M*] = (fkd[I]]/kt)1/2



Contoh grafik lihat buku referensi (Bilmeyer, dll)

Autoacceleration

ri rt

Grafik lihat buku referensi

Kinetic Chain Length

Jumlah monomer yang dapat digandeng oleh satu radikal

RMMM ........ MMR

Terminasi coupling v =1/2 Xn

Terminasi disproporsionasi v = Xn

Chain Transfer

Dengan solvent

Mx* + SH ktr,S MxH + S*

Dengan initiator

Mx* + (C6H5COO)2

ktr,I Mx-OCOC6H6 + C6H6COO*

Dengan monomer

X X X

-CH2 – CH* + CH2=CH ktr,M -CH=CHX + CH2CH*



Persamaan derajat polimerisasi untuk chain transfer

Bila tanpa solvent

Regulator

Mx* + RSH MxH + RS* +M RS – M*

>> Bisa mengatur M

>> Disebut juga transfer agent

>> Paling dominan : Merkaptan (bersifat racun)

Inhibitor

O O R-Mx R-Mx

H H

O (Ia) O* (Ib) O R-Mx-O



R-Mx* +

O O* (II) Quinon

OH

+ R-Mx

OH O* (III) : hidroquinone

OH

Styrene inhibitornya tertier butyl catechol ( TBC + 50 ppm ) >> bisa menahan styrene tidak

terpolimerisasi selama beberapa bulan.

Retarder

NO2 H NO2

R-Mx* + R-Mx

(plus resonance structure)

Batlet and co-worker concluded that addition to the nitro group also occurs. Price and Read found

that several m-dinitrobenzene molecules were combined with the polymer for each fragment from

the p-bromobenzoyl peroxideused as initiator in the retarded polymeration of styrene. They inferred

that radical responding to IV transfers its hydrogen atom to a molecule of styrene follows :

NO2

IV + C6H5CH=CH2 R-Mx - + CH3-CH-C6H5

NO2

POLIMERISASI KATIONIK

Initiation

Catalyst-cocatalyst : asam Lewis (Friedel-Craft) AlCL3, BF3, SnCl4, ZnCl2

BF3 + H2O H+(BF3OH) –

CH3

H+(BF3OH) - + (CH3)2-C=CH2 CH3 – C + (BF3OH) –

CH3

RCl + SnCl4 R+(SnCl5) –



A + RH K H+(AR) –

H+(AR) - + M ki HM+(AR) -

Ri = Kki[A][RH][M]

Propagation

HMn+ (AR) - + M kp HMnM+(AR) –

Rp = kp[HMn+ (AR) -][M]

Termination

HMn+ (AR) - kt Mn + H+(AR) –

Rt = kt [HMn+ (AR) -]

>> Spontaneous termination

>> Chain transfer to counter ion

Chain transfer:

HMn+ (AR) - + M kp Mn + HM+(AR) – Rt = ktr,M ......

Combination :

HMn+ (AR) - HMn(AR)

Steady State

Ri = Rt

Dominan chain transfer Ri = Rtr,M

CM : transfer constant

Sebagian reaksi polimerisasi kationik berjalan sangat cepat

Isobutylene, AlCl3 bereaksi pada - 100o C



anggapan steady-state tidak tepat.

POLIMERISASI ANIONIK

Metal amida

KNH2 K K+ + H2N: -

Styrene, -33 oC, solvent NH3 (titik didihnya)

H

H2N: - + CH=CH2 ki H2N – CH2 – C : -

Propagasi

H2N – Mn– + M kp H2N – MnM –

Chain by transfer : ke solvent

H2N – Mn– + NH3 ktr H2N – MnH + H2N: -

Initiation by Electron Transfer

. _

Na + : Na+

. _ . . . -- : Na+ + CH=CH2 + CH2 – CH2 Na+

dapat terjadi :

.. . -- -- H H -- 2 CH2 – CH2 Na+ Na+ : C – CH2 – CH2 – C : Na+

Initiation by Metal Alkyls

H H C4H9Li + CH2=C C4H9 – CH2 – C : - Li+

X X

Propagation



Mn– Me+ + M MnM – Me+

Rp = kp [M -][M]

Living Polimer

POLIMERISASI KOORDINASI

Skema Reaksi Polimerisasi

: Permukaan logam transisi

MeR : Organometal group I-III

+ MeR K1 --MeR

+ M K2 M--

Initiation

M-- --MeR Ki --Me – M – R

Propagation

M-- --Me – Mn – R Kp --Me – MnM – R

Termination

Chain transfer with monomer

M-- --Me – Mn – R ktr,M --Me – M – R + Mn

Spontaneous internal hydride transfer

--Me – Mn – R k2,M --MeH + MnR

“unsaturate”

Transfer to Me - R

R – Me -- --Me – Mn – R ktr,C --Me – R + Mn – MeR

Forming inactive site

M – M e

M-- --Me – Mn – R ktr,M + MnR

Ziegler-Natta:

Organometal : Al(Cl)3; AlClEt3

Garam logam transisi : TiCl4



Active Site :

RMx* + M RMx+1

*

Bimetallic Mechanism

CH2=CCH2 CH2 CH2 CCH2 CH2

Ti Al Ti Al

R R

CH2 CH3

CHCH3 CH

CH2 CH2 CH2

Ti Al Ti Al

R R

Mono metallic Mechanism

CH2 Cl CH2=CHCH3 CHCH3

Cl Ti (active site) Cl Ti

Cl Cl Cl Cl CH2

CH2

CHCH3

CH2 Cl Cl CH2 CH2 CHCH3

Cl Ti Cl Ti – CH2 – CHCH3 Cl – Ti CH2



Cl Cl Cl Cl Cl Cl Cl

Polipropilen

CH3

-- C – C – C – C – C – C --

CH3 CH3

Atactic: poliadisi radikal struktur tidak teratur, sifatnya lembek

-- C – C – C – C – C – C --

CH3 CH3 CH3

Isotactic: menggunakan Ziegler-Natta polimer kuat

Langmuir Adsorption

Fraksi MeR di permukaan

Fraksi M di permukaan



Ri = kiAM

Rp = kpMC * C * : konsentrasi “growing polimer”

Rtr,M = ktr,MMC *

Rtr,C = ktr,C[MeR] C *

RtM = ktMMC *

Bila dianggap steady-state:

Ri = Rt

kiAM = ktMMC * + ktr,CAC * + ktr,MMC *

C * = (.....k1AM......)/(...............)

PEMBUATAN POLIMER

1. Polimerisasi curah (bulk polymerization)

Proses sederhana, untuk kapasitas kecil

Hasilnya kental, padat sehingga perpindahan panasnya jelek

2. Polimerisasi larutan (solution polymerization)

Larutan tidak kental, perpindahan panas baik

Perlu pemisahan hasil dengan pelarut

Efek pelarut terhadap BM (lebih rendah)

3. Polimerisasi suspensi (pearl, bead)

Menggunakan air ( +suspension agent )

Kontrol suhu baik

Hasil berbentuk butir berukuran 0,1 mm – 1 mm

4. Polimerisasi emulsi

Menggunakan air + surfactant

Kontrol suhu baik

Hasil berbentuk emulsi (ukuran butir 1 mikron)

Polimerisasi suspensi: initiator lebih mudah larut dalam monomer.

Polimerisasi emulsi: initiator lebih mudah larut dalam air.



POLIMERISASI EMULSI

surfactant

Bagian surfactant :

hidrofil > suka air > ionik

hidrofob > benci air > kationik

Jenis surfactant

Anionik

Contoh :

Sabun O

—————— C – O -- Na+

hidrofob hidrofil

Dodekil Sulfonat – detergent

——————SO3 – Na+

rantai linier cepat hancur dibanding bercabang

Kationik

H – N + Cl– + sangat efektif untuk mencuci >> mahal

+ tak tahan suhu tinggi

Non-ionik

——— O – CH2 – CH2 – O – CH2 – CH2 - .........OH

hidrofil

Micelle

Stabil tapi menggerombol pada suatu saat konstan

Critical micelle capacity

C



Resep polimerisasi emulsi :

Monomer 100 bagian berat

Air 180

Emulsifier 1-5

Initiator 0,2-0,5

Initiator Persulfat

K2S2O8 S2O8 2- 2SO4

-

(Na, NH4)

Teori Smith-Ewart

menganggap surfactant inert

menganggap 1 partikel hanya menerima 1 radikal (karena apabila 2 radikal akan terminated)

CA = H.CM

NA ~ ag.kc(CAs – CA) NA : kecepatan pergerakan

db : diameter butir/gelembung

Yang lebih banyak menerima radikal diameter kecil

Periode awal reaksi

Polimerisasi terjadi di butiran kecil (misel) membentuk inti polimer

Suatu saat surfactant akan habis melapisi inti polimer yang terus berkembang.

jumlah inti polimer tetap

Periode reaksi lanjut

Polimerisasi di inti polimer

Rp = kp[M][M*]

Rp : kecepatan 1 partikel

Rp = kp[M]N/2 per cm3 water

Karena satu hidup satu mati

N : konsentrasi partikel polimer

Kecepatan penambahan volume partikel

vm : fraksi mol monomer



vu : spesific volume monomer

Sebuah partikel yang terbentuk pada waktu :

Partikel yang terbentuk

t1

t

Volum = ( t - )

dianggap 1 partikel hanya menerima 1 radikal (karena apabila 2 partikel akan terminated)

Pada waktu t, volum partikel = ( t - )

luas permukaannya :

Luas permukaan semua partikel yang terbentuk :

Pada saat t1semua surfactant habis:

Luas surfactant: At = Cs.as

Cs.as = 3/5 [(4л)1/2 3μ]3/2 t15/3

t1 = [ ......... ] (Cs as/)3/5 -2/5

Jumlah partikel yang terbentuk:

N = t1 = 0,53 (Cs as)3/5 (/)2/5

Teori ini benar untuk kelarutan kecil

tetapan 0,53 dikoreksi menjadi 0,4

COPOLYMERIZATION

M1* + M1 k11 M1

* jumlah radikal M1 tetap

M1* + M2 k12 M2

*

M2* + M2 k22 M2

* jumlah radikal M2 tetap

M2* + M1 k21 M1

*

Yang berpengaruh : sifat monomer yang ada di belakang.

Pada saat reaksi, konsentrasi radikal dianggap tetap sehingga:

k21[M2*][M1] = k12[M1

*][M2] ...........(2)

Kecepatan konsumsi monomer M1 and M2 adalah:

........................(3)



.........................(4)

Substitusi Pers.(2) ke Pers. (3) dan (4), serta Pers (3) dibagi Pers. (4), diperoleh:

.......................(5)

dengan r1 and r2 adalah monomer reactivity ratio:

....................(6)

....

.................(7)

Bila f1 dan f2 adalah mol fraksi untuk monomer M1 and M2 yang belum bereaksi:

Pers. (5) menjadi:

.....................(8)

Bila r1 dan r2 diketahui, dan komposisi monomer ditetapkan (tertentu), maka komposisi polimer (dalam increment rantai) dapat dihitung.Komposisi molekul polimer secara keseluruhan merupakan penjumlahan increment polimer yang terbentuk.

Monomer 1 Monomer 2 r1 r2

Etilen Vinil Asetat 0,130 1,230 Karbon monooksida 0,025 0,004 Propilen 3,200 0,620

Stiren Akrolinitrile 0,290 0,020 Butadiene 0, 820 1,380 Divinilbenzena 0,260 1,180 Maleat anhidrid 0,097 0,001 Metilmetakrilat 0,585 0,478 4-khlorostiren 0,816 1,062 Vinileden khlorida 1,700 0,110

Vinil khlorida Vinileden khlorida 0,205 3,068



Ideal Copolymerization

Reaktivitasnya sama baik sejenis maupun berlainan jenis

r1 r2 = 1

Persamaan menjadi:

..............(10)

...............(11)

5

28

F1 mole fraction of 1 0,5

M1 in polymer

0,2

f1mole fraction of M1 in monomer mixture

Alternating Copolymerization

Kopolimerisasi selang-seling

M1 lebih suka bereaksi dengan M2 daripada dengan M1; dan sebaliknya juga M2 M1

>> k11 ~ 0

>> r1 = k11/k12 0

f1 0

PENENTUAN BERAT MOLEKUL

Analisis gugus ujung/fungsional

Biasanya analisis secara kimia, misalnya –COOH dengan titrasi

Hanya untuk BM rendah, < 5000



Boiling point elevation and freezing point depression

polimer harus dalam larutan

dapat mengukur BM sampai 10.000-an

Kenaikan titik didih (boiling point elevation):

...........(4)

R: gas constant, T: absolute temperature, : rapat massa solvent, b: latent heat of vaporization of

solvent (per gram), C: konsentrasi solute (gram per m3), M: berat molekul solute.

Freezing point depression:

...........................(5)

if : latent heat of fusion per gram solvent.

Dengan alat vapour pressure osmometer:

untuk zat standar

untuk bahan yang ingin diketahui BM nya

Tekanan Osmosis

..........................(10)

Tekanan osmosis untuk larutan:

...........................(11)

Untuk gas: p = C.R.T

Untuk larutan: = C.R.T

= c/M RT

(/C)o = 1/M RT

Light Scattering (hamburan cahaya)

C

W T



S

P L D1

D2

R

Light Scattering Instrument

>> scattering

>> turbidity memantulkan cahaya

Where io is the turbidity due to molecules of molecular weight Mi.

Since dn/dc will be practically identical for a series of polymer homologues, a single value of H applies to all of them and we obtain in analogy with Eq. (22).

io = H ci.Mi

The forbidding appearance of the summation sign may be avoided merely by writing :i

o = H. c. Mw .........(25)where Mw is the weight average molecular weight defined by any of the following alternate expression :

.........(26)

Sedimentation

At point in a cell a distance x from the axis of rotation the force acting on a particle of mass m and

(partial) specific volume v immersed in a medium of density is given by :



M(1-v) r 2

Where is the angular velocity of rotation.

Equating this to frictional force, obtained by multiplying the velocity dx/dt by the frictional

coefficient f, leads to the primary sedimentation velocity relationship

The quantity on the left, which is determined by measuring the rate of movement of the

sedimentation constant s. Thus :

.............(40)

The mass of the sedimentation particle could be deduced from its rate of sedimentation at high

dilution in a given field, i.e. from its sedimentation constant, if the frictional coefficient f could be

determined independently.

Rate of diffusion may be utilized to secure this necessary supplementary information, since the

diffusion constant D depends also on the frictional coefficient. Thus :

..............(41)

where is the activity coefficient of the solute. This reduce at infinite dilution to

...............(42)

which in combination with eq. (40) at infinite dilution (multiplied by Avogadro’s number) given :

.................(43)

Hence the molecular weight may be calculated from the ratio of the limiting value of D and s at

infinite dilution. The problem is to secure accurate value for Do and so.

The change in the sedimentation constant with concentration enters solely from the change in 1/f1

an it is customary therefore to extrapolate i plot 1/s against c to infinite dilution.

Ff = m 2R – m/s 2 R

F(dr/dt) = m2R(1-v)

v=1/s

Sedimentation equilibrium :



Intrinsic Viscosity – Molecular Weight Relationship

K’ : approximately constant for a series of polymer homologues in given solvent.

= 0,35 – 0,40

Intrinsic viscosity may also be defined :

Gel permeation chromatography



Seperti liquid chromatography

Dapat menentukan BM tiap fraksi polimer

Perlu polimer standar untuk penentuan BM

PEMAKAIAN POLIMER

Polimer tunggal Kadang kurang menguntungkan (misalnya : PVC murni terlalu getas) Penambahan aditif

o Bahan pengisi (filter) : selulosa, tepung, TiO2, karbono Zat warnao Stabilizero Plasticizer : untuk PVC, ditambah DIOPo Lubricant (pelumas anti lengket >> silikon)

Agar mendapat bahan dengan sifat yang diinginkan penambahan aditif

Polimer campuran Kopolimerisasi : monomer A + monomer B Polymer blending (polyblend)

Penambahan karbon black pada karet menambah keras Stabilizer : Thermal: PVC + Ca stearat / Zn stearat / Sn stearat / Cd stearat UV Oxygen: ditambah anti oksidan

Bingham = o + dv/dx

Dilatant

ln

Newtonion = -dv/dx

Pseudoplastik

ln(dv/dy)

Fluida Bingham baik untuk cat agar bisa merata

SIFAT FISIS DAN STRUKTUR MIKRO



Sifat fisis dipengaruhi oleh struktur molekul (konfigurasi) dan berat molekul (distribusi BM)

Struktur:

Letak ikatan di dalam rantai

Letak rantai cabang : isotaktik, sindiotaktik, ataktik

Amorf, kristal

Glass point, melting point

alternating

random

block

Graft

Terpolimer

CH3 H CH3 CH2

C=C C=C

CH2 CH2 CH2 H

cis trans

H2 H H H2 H2 H H H2

C = C – C = C - C – C = C – C –

H H C - C = C C = CC = C C H C – C C

- C H2 H2

H2 trans cis

Isotaktik

cabangnya teratur (ke atas semua)

polypropylene

H R H R H R H - C – C – C – C – C – C – C - H H H H H H H



Sindiotaktik

teratur atas-bawah

H R H R H R H - C – C – C – C – C – C – C - H H R H H H H

Ataktik

tak teratur cabangnya

H R H H H R R - C – C – C – C – C – C – C - H H H R H H H

Sketsa bentuk kristalin dan amorf

kristalin

amorf

Struktur amorf



Diffuse transition zone Diffuse transition zone

T Viscous T Viscous Rubbery

Liquid Rubbery liquid Melting point

Glass transition flexible crystalline polymer

Glass transition

Glassy Rigid Crystalline Polymer

BM BM

Amorf Moderately Crystalline

POLIMER Tg, oCPolieteilen (LDPE)Polipropilen (ataktik)Polipropilen (isotaktik)Polivinil asetat (PVAc)Polietilentereftalat (PET)Polivinil alkohol (PVA)Polivinil chlorida (PVC)PolistirinePolimetilmetakrilat (ataktik)

-125-2010028698581

100105

PENGARUH LUAR TERHADAP POLIMER

Pengaruh senyawa kimia lain (chemical effects)Misalnya ketahanan terhadap pelarut (solvent) dari solubility parameter (δ)

Pengaruh panas dan suhu tinggi Melting point polimer Pada suhu tinggi dapat terurai (dekomposisi) pyrolysis

Pengaruh sinar/radiasiSinar UV

Biological and weathering effectsMikroorganisme alam dapat merusak polimer



SOLUBILITY PARAMETER (δ)

Meskipun dengan pendekatan ideal, solubility parameter digunakan untuk patokan larut tidaknya polimer di dalam cairan/solvent. Pelarutan terjadi bila energi bebas (free energy) untuk pencampuran (mixing) negatif.

ΔG = ΔH - TΔSΔH adalah panas pencampuran, S adalah perubahan entropi.Untuk molekul nonpolar dan tidak ada efek hydrogen bonding, ΔH positif. Hildebrand mendekati ΔH dengan persamaan:

ΔH = v1.v2(δ1- δ2)2 Indeks 1 untuk solvent dan 2 untuk polimer. v adalah fraksi volum, dan δ adalah cohesive energy density, atau sering disebut solubility parameter.Bila tidak ada interaksi yang kuat, seperti hydrogen bonding, bisa “larut” bila (δ1- δ2) kurang dari 3,5 – 4. Berikut beberapa contoh besarnya solubility parameter.

Diambil dari of Polymers", Encyclopedia of Polymer Technology, 2nd. Ed.

chemical solubility parameter

decafluorobutane 10.6neopentane 12.9 A A letter next to the solventn-hexane 14.9 A solubility parameter indicatesdiethyl ether 15.1 that the polymer correspondingcyclohexane 16.8 A to the letter (listed below)carbon tetrachloride 17.6 A B dissolves in the solvent.benzene 18.8 A Bchloroform 19.0 A B Cmethyl ethyl ketone 19.0 B Cactone 20.3 B Ccarbon disulfide 20.51,4-dioxane 20.5 B Cdimethylformamide 24.8 B C (D) (at high temperatures only)m-cresol 27.2 B C Dformic acid 27.6 B Dmethanol 29.7water 47.9

A Poly(isobutylene) 16.2B Poly(methylmethacrylate) 18.6C Poly(vinyl acetate) 19.2D Poly(hexamethylene adipamide) 27.8



POLYMER PROCESSING

Moulding: compression, injection, blow

Extrusion: piston, screw

Calendering

Spinning: melt, dry, wet

Thermoforming

POLIMER YANG DIGUNAKAN SEKARANG

Polyethylene, polypropylene, polyvinylchloride, polystyrene

Selulose, karet



Injection molding: Overview

Injection molding is used extensively for the manufacture of polymeric items. A reciprocating/rotating screw both melts polymer pellets and provides the pressure required to quickly inject the melt into a cold mold. The polymer cools in the mold and the part is ejected. Injection molding machines are sized primarily by the force available in the mold clamping unit; ranging from 20 tons in laboratory machines to over 5000 tons in large commercial machines.

Process Schematic

References

Gerd Potsch, Injection Molding: An Introduction, Hanser Publishers, New York (1995) ISBN 1-569-90193-7.

Reaction injection molding:

Reaction injection molding (RIM) is a processing technique for the formation of polymer parts by direct polymerization in the mold through a mixing activated reaction. A simplified process schematic is shown at right. Two reactive monomeric liquids, designated in the figure as A and B, are mixed together by impingement and injected into the mold. In the mold, polymerization and usually phase separation occur, the part solidifies, and is then ejected. Primary uses for RIM products include automotive parts, business machine housings, and furniture.

Process Schematic


http://www.polymerprocessing.com/operations/tim/big.html


References

C.W. Macosko, RIM, Fundamentals of Reaction Injection Molding, Hanser Publishers, New York (1989) ISBN 3-446-15196-6.

Film blowing: Overview

The majority of polymer films are manufactured by film blowing (blown film extrusion). A single screw extruder is used to melt the polymer and pump it into a tubular die, as shown in cross-section at right. Air is blown into the center of the extruded tube and causes it to expand in the radial direction. Extension of the melt in both the radial and down-stream direction stops at the freeze line (frost line) due to crystallization of the melt. The nip rolls collect the film, as well as sealing the top of the bubble to maintain the air pressure inside. This process is used extensively with polyethylene and polypropylene.

Process Schematic

References

J.F. Agassant, P. Avenas, J.Ph. Sergent, P.J. Carreau, Polymer Processing Principles and Modeling, Hanser, New York (1986). ISBN 0-19-520864-1, pages 252-262.

Extrusion: Overview

Single screw extrusion is one of the core operations in polymer processing and is also a key component in many other processing operations. The foremost goal of a single screw extrusion process is to build pressure in a polymer melt so that it can be extruded through a die or injected into a mold. Most machines are plasticating: they bring in solids in pellet or powder form and melt them as well as building pressure.

Process Schematic

References

J.L. White, Twin Screw Extrusion: Technology and Principles, Hanser Publishers, New York (1991) ISBN 3446156917.


http://www.polymerprocessing.com/polymers/PP.html

http://www.polymerprocessing.com/polymers/PE.html

http://www.polymerprocessing.com/operations/sscrew/big.html


Overview

Twin screw extrusion is used extensively for mixing, compounding, or reacting polymeric materials. The flexibility of twin screw extrusion equipment allows this operation to be designed specifically for the formulation being processed. For example, the two screws may be corotating or counterrotating, intermeshing or nonintermeshing. In addition, the configurations of the screws themselves may be varied using forward conveying elements, reverse conveying elements, kneading blocks, and other designs in order to achieve particular mixing characteristics.

Process Schematic

References

J.L. White, Twin Screw Extrusion: Technology and Principles, Hanser Publishers, New York (1991) ISBN 3446156917.

Dry spinning: Overview

Dry spinning is used to form polymeric fibers from solution. The polymer is dissolved in a volatile solvent and the solution is pumped through a spinneret (die) with numerous holes (one to thousands). As the fibers exit the spinneret, air is used to evaporate the solvent so that the fibers solidify and can be collected on a take-up wheel. Stretching of the fibers provides for orientation of the polymer chains along the fiber axis. Cellulose acetate (acetone solvent) is an example of a polymer which is dry spun commercially in large volumes. Due to safety and environmental concerns associated with solvent handling this technique is used only for polymers which cannot be melt spun.

Process Schematic

References

A. Ziabicki, Fundamentals of Fiber Formation, Wiley, New York (1976). ISBN 0471982202.A more detailed study of dry spinning is :Y. Ohzawa, Y. Nagano, and T. Matsuo, J. Appl. Polym. Sci., 13, pp. 257-283 (1969).


http://www.polymerprocessing.com/operations/tscrew/big.html


Melt Spinning: Overview

Melt spinning is the preferred method of manufacture for polymeric fibers. The polymer is melted and pumped through a spinneret (die) with numerous holes (one to thousands). The molten fibers are cooled, solidified, and collected on a take-up wheel. Stretching of the fibers in both the molten and solid states provides for orientation of the polymer chains along the fiber axis. Polymers such as poly(ethylene terephthalate) and nylon 6,6 are melt spun in high volumes.

Process Schematic

References

A. Ziabicki, Fundamentals of Fiber Formation, Wiley, New York (1976). ISBN 0471982202.A classic article which emphasizes structure development during melt spinning is:J.R. Dees and J.E. Spruiell, J. Appl. Polym. Sci., 18, pp. 1053-1078 (1974).

Filament winding: Overview

Filament winding is used for the manufacture of parts with high fiber volume fractions and controlled fiber orientation. Fiber tows are immersed in a resin bath where they are coated with low or medium molecular weight reactants. The impregnated tows are then literally wound around a mandrel (mold core) in a controlled pattern to form the shape of the part. After winding, the resin is then cured, typically using heat. The mold core may be removed or may be left as an integral component of the part.

Process Schematic

A comprehensive reference on filament winding is:Filament Winding: Its Development, Manufacture, Applications, and DesignD.V. Rosato, Interscience Publishers, New York (1964).

Calendering



Thermoforming


Handout Teknologi Polimer

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