Polypropylene (PP) has become one of the most widely used commercial polyolefins. PP is obtained through chemical synthesis with Ziegler-Natta and metallocene catalyst which produce highly linear, highly stereospecific polymers and relative narrow molecular weight distribution

H2C CH

CH3 Polymerization

iPP

Commercial isotactic PP (iPP) possesses many excellent properties, such as : Low density ~ 0.96 g/cm3

High melting temperature ~ 170°C

Good chemical resistance

Low production cost

Stiffness and Reusability

However, iPP is a linear polymer, which has relative low

melt strength and exhibits no strain hardening behavior in

the molten state.

The fluids that exhibit strain hardening have micro estructural interactions that offers resistance to molecular alignment in the direction of flow

Zhenjiang et al.Polymer 53 (2012) 121-129

Extension

PP with highly linear chains has limitations to be used in applications such as thermoforming, foaming, blow molding, film molding because the extensional deformation present in these processes is a key property.

Blow

n m

oldi

ng

Blow

n fi

lm

Foam

ing

The most effective strategy to improve extensional performance is to modify the topology of linear molecules incorporating long branches in order to increase the restrictions on molecular mobility improving the behavior of the material in extensional flow

Mb > Mc = 2Me ≈ 14 Kg/mol

The generation of branches onto the backbone of commercial PP has been achieved for different methods: Polymerization in situ: in this process the branches are generated simultaneously with the polymerization reaction. Irradiation: the generation of macroradicals is through macromolecular excitation using different doses of electron beam irradiation or electro-magnetic waves. Reactive extrusion: this process involves chemical attack of PP in the molten state in presence of an appropiate peroxide and polyfunctional monomers able to promote the generation of branches.

Modify the topology of the iPP generating long branches in its molecular structure by reactive mixing in the molten state, in order to improve their performance in elongational flow.

iPP LCBPP

Reactive mixing

PPg (1% AM) Mw=120 Kg/mol PD=2.6

Branching agent

Reaction in molten state 190 C

LCB PP

Purification

Characterization

Brabender Plastograph® 40 rpm during 15 min

Rheology (AR-G2 TA Instruments) using a 25 mm plate-plate geometry.

Espectroscopy IR (Nicolet, Madison, WI; model 5210) operating at a resolution of 4 cm-, using films of 100 μm

SEC (PgGlicerol) DSC (PgGlicerol y PgEpoxi)

Glycerol Epoxy resin 1,4 Butanediol p-Phenylendiamine

Branching Agent (Abbreviation) Chemical structure % p/p Characterization

Glycerol (PgG)

0.1 0.3 0.5 1 5

IR, Rheology, SEC and DSC

Epoxy resin (PgEp)

0.65 1.9 2.5 3.2

IR, Rheology and DSC

1,4 Butanediol (PgBOH)

0.3 0.9 2.3 3.0 4.5

IR, Rheology and DSC

p-Phenylendiamine (PgFDA)

0.11 0.21 0.34

IR and Rheology

OH OHOH

OHOH

O

OH

O

H2C CH CH CH CH2

H2N NH2

O

OO

OH OH

O

OO

HO

O

O O

H O

OH

OH

+

1792 cm-1

1784 cm-1

1735cm-1

1710 cm-1

Branching agent Glycerol

2800 2400 2000 16002600 2200 1800

Wavenumbers (cm-1)

Abs

orba

n ce

(a.u

. )

Pg

PgG01

PgG03

PgG05

PgG1

PgG5

FTIR spectra of PPgAM + Glycerol

1792 cm-1 1784 cm-1

1735cm-1

Signals at 1792 and 1860 cm-1 are due to C=O stretching of free succinic anhydride, and signal at 1780 cm-1 assigned to poly(maleic anhydride. Bands at 1715 and 1735 cm-1 assigned to stretching of the carboxylic acid group and carboxylic ester group respectively.

FTIR spectroscopy

3 4 5 6 73.5 4.5 5.5 6.5 7.5

Log M

0

0.2

0.4

0.6

0.1

0.3

0.5

0.7

Nor

ma l

ize d

Wt F

r

PgG5PgG1PgG05PgG03PgG01Pg

Molecular weight distribution of Pg and its modifications

Molecular Characterization

Mark-Houwink plot of the initial Pg and the

modified samples

Sample Mw (103 g/mol)* Mw/Mn NLCB

PPg 117 2.7 0 PPg01G 147 3.1 ~0

PPg03G 351 6.6 0.08

PPg05G 590 6.2 0.30

PPg1G 625 3.1 0.40

PPg5G 669 2.8 0.62

* Obtained by triple detection

Molecular Characterization

4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4

Log Mw

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

Log

[η]

PgPgG01PgG03PgG05PgG1PgG5

Complex viscosity (η∗) vs. frequency (ω) at 180°C

10-3 10-2 10-1 100 101 102 103

ω (s-1)

102

103

104

η* (P

a.s)

PgG5PgG1PgG05PgG03PgG01Pg

Zero shear viscosity η0 dependence on weight average molar mass MwLS for the initial material Pg and the modified samples to 180°C.

Relationship between rheological and molecular characterization

Auhl, D. et al. Macromolecules 2004, 37(25), 9465-9472.

Storage modulus (G’) vs frequency (ω) at 180°C

1E-006 1E-005 0.0001 0.001 0.01 0.1G*/Go

N

40

60

80

50

70

90

δ (°

)

PPg5GPPg1GPPg05GPPg03GPPg01GPPg

van Gurp-Palmen plot: Loss angle (δ) vs. G*/GN0 at 180°C.

40 60 80 100 120 140 160 180

T (°C)

Hea

t Flo

w (W

/ g)

Pg

PgG01

PgG03

PgG05

PgG1

PgG5

DSC curves of initial PP and modified LCBPP with increasing Glycerol

concentration. (a) Crystallization curves (b) Melting curves

Sample Tc (°C) Tm (°C) Pg 120 158,5

PgG01 120.4 159,4 PgG03 119.7 157.7 PgG05 119.5 159.2 PgG1 117 159.7 PgG5 118.5 159.8

b a

FTIR results indicated that the grafting reaction took place and glycerol has been grafted on the PP backbone. A new band appears at about 1735 cm-1 which is characteristic of carbonyl groups of the ester in the MAH molecule, and, therefore, suggesting the existence of LCB.

From GPC-LLS analysis, PPG-g showed extensive departure from

linear behavior on the high molecular weight fraction. Branched PP showed considerably increase on the long relaxation

modes by small-amplitude oscillatory shear experiments. The rheological characteristics such as higher G’ at low frequency and G* shifting to smaller values of the phase angle in the van Gurp Palmen plot confirm different relaxation mechanism for LCBPP from linear PP

Melting temperature slightly increases while crystallization temperature decreases with increasing degree of branching.

O O O

+ HO OH

O O O OH

O HO

O

PPg 1,4 Butanediol

PPg#BOH

1792 cm-1

1784 cm-1

1735 cm-1

2000 1900 1800 1700 1600 15001950 1850 1750 1650 1550

Número de onda (cm-1)

Abso

rban

cia (u

.a.)

PPg

PPg03BOH

PPg09BOH

PPg23BOH

PPg30BOH

PPg45BOH

1792 cm-1 1784 cm-1

1735 cm-1

FTIR spectroscopy

FTIR spectra of PPgAM + 1-4 butanediol

0.001 0.01 0.1 1 10 100 1000ω (s-1)

10-3

10-2

10-1

100

101

102

103

104

105

G' (

Pa)

PPgPPg03BOHPPg09BOHPPg23BOH PPg30BOHPPg45BOH

Storage modulus (G’) vs frequency (ω) at 180°C

10-6 10-5 10-4 10-3 10-2 10-1

G*/GoN

40

60

80

50

70

90

δ (°

)

PPgPPg03BOHPPg09BOHPPg23BOHPPg30BOHPPg45BOH

Rheological characterization

van Gurp-Palmen plot: Loss angle (δ) vs. G*/GN0 at 180°C.

80 100 120 140 160 18090 110 130 150 170

T (oC)

0

2

4

6

8

1

3

5

7

Hea

t Flo

w (W

/ g)

Pg

PgBOH0.3

PgBOH0.9

PgBOH2.3

PgBOH3

PgBOH4.5

100 110 120 130 14095 105 115 125 135

T (oC)

-5

0

5

10

-7.5

-2.5

2.5

7.5

12.5

Hea

t Flo

w (W

/ g)

Pg

PgBOH0.3

PgBOH0.9

PgBOH2.3

PgBOH3

PgBOH4.5

Sample Tc (°C) Tm (°C) Pg 120 158,5

PgBOH0.3 120,5 159,2 PgBOH0.9 117,8 158,2 PgBOH2.3 117,7 157,2 PgBOH3.0 118,5 156,7 PgBOH4.5 120,5 159,2

DSC heating curves (a) and cooling curves (b) of linear PP and LCB PPs.

12 16 20 24 28

2 theta, o

0

5000

10000

15000

20000

25000

Inte

nsity

, a.u

.

PPgMA- 1,4-ButanediolPPgMA0.3%0.9%2.3%3.0%4.5%

WAXD diffractogram of PP and LCB PPs

La presencia de la banda de absorción a 1735 cm-1 confirma la presencia de grupos carbonilos de éster producto de la reacción del anhídrido del Pg con el diol.

El comportamiento viscoelástico lineal de los polímeros

sugiere la presencia de estructuras moleculares complejas al evidenciar la aparición de procesos lentos de relajación que aumenta en importancia a medida que se incrementa la concentración de diol utilizada.

O

OO

OO

O

O

O O

O

O

OH

OO

O

O

OH

O

H2C CH CH

COOH

CH

CH2

CH

Estructura I

Estructura III

X 2

COOH

CH

CH2

CH

Estructura II

HC CH2CH2

1792 cm-1

1784 cm-1

1735cm-1

1900 1800 1700 1600 15001850 1750 1650 1550Número de onda (cm-1)

Abso

rban

cia (u

.a)

Pg

PgEp1.9

PgEp2.5

PgEp3.2

PgEp0.65

1735 cm-1

1782 cm-1

1790 cm-1

FTIR spectroscopy

FTIR spectra of PPgAM + epoxi

0.1 1 10 100 1000

ω (s-1)

1

10

100

1000

10000

100000

G' (

Pa)

PgEp3.2PgEp2.5PgEp1.9PgEp0.65Pg

2

Rheological characterization

Storage modulus (G’) vs frequency (ω) at 180°C

100

101

102

103

Time (s)

103

104

105

106

107

108

Ext e

n sio

n al v

isco

s it y

(Pa .

s ) PgFDA 0.34% rate 0.01PgFDA 0.34% rate 0.1

20 40 60 80 100 120 140 160 180T (oC)

-8

-4

0

4

8

Fluj

o de c

alor (

W/g

)

Pg

PgEp0.65

PgEp3.2

PgEp1.9

PgEp2.5

20 40 60 80 100 120 140 160 180T (oC)

-2

0

2

4

Fluj

o de

calo

r (W

/g)

Pg

PgEp0.65

PgEp3.2

PgEp1.9

PgEp2.5

Tc ( C) Tm ( C) Pg 120 158.5

PgEp0.65 120.5 159 PgEp1.9 123.5 160.5 PgEp2.5 124.5 161 PgEp3.2 134 161.5

DSC heating curves (a) and cooling curves (b) of linear PP and LCB PPs.

La presencia de bandas de absorción a 1715 y 1735 cm-1 confirma la presencia de grupos carbonilos de ácido y éster que resultarían de la reacción del anhídrido del Pg con la resina epoxi.

El comportamiento viscoelástico lineal de los polímeros

sugiere la presencia de estructuras moleculares complejas al evidenciar la aparición de procesos lentos de relajación que aumenta en importancia a medida que aumenta la concentración de epoxi utilizada.

El análisis térmico indica un aumento de Tc y Tm con el aumento del grado de modificación, además del tipo de estructura cristalina predominantes, α y β, que se presentan en los materiales estudiados.

SEC with triple detection indicated branched structures in the high molecular weight tail of the distribution with high molecular weight branches

El análisis térmico indica un aumento de Tc y Tm con el aumento del grado de modificación, además del tipo de estructura cristalina predominantes, α y β, que se presentan en los materiales estudiados.

3 4 5 6 73.5 4.5 5.5 6.5 7.5

Log M

0

0.4

0.8

1.2

0.2

0.6

1

1.4

d (W

)/d(L

o gM

)PgG5PgG1PgG05PgG03PgG01Pg