DESARROLLO SOSTENIBLE DE LA INDUSTRIA

DEL POLIPROPILENO:PROPIEDADES CONTROLADAS A MEDIDA

Y OPTIMIZACIÓN DEL CONSUMO ENERGÉTICO Y DE LA

DEGRADACIÓN

Enrique Vallés

PLAPIQUI

UNS – CONICET

Bahía Blanca – Argentina

Proyecto CYTED Granada 2011

Principales Líneas de Investigación del Grupo de Polímeros del

PLAPIQUI

Producción de Polímeros con Estructura Controlada

Modelamiento de Procesos de Polimerización

Relación Entre Estructura y Propiedades

Propiedades Viscoelásticas de Gomas Modelo con Estructura

Controlada

Modificación de Polímeros

Reología de Polímeros

Procesamiento Reactivo

For many special applications there is a need to improve the properties of available

commercial resins, in particular with respect to rheological behavior, heat deformation

resistance, chemical resistance, stress cracking, shrinkage, thermoforming behavior,

high melt strength, uniform cell structure of extruded foams and compatibility with

other polymers or materials.

The introduction of chain branching, crosslinks, chain scissions and grafted chemical

functional groups on a given polymer by different techniques may produce some of

the desired modifications on the polymer behavior.

The primary effect of radiation and chemical modifiers on thermoplastic polymers is

creation of macroradicals and scission of bonds. Built radicals lead to further

changes in molecular structure through chemical reactions. The final consequences

are branching, crosslinking, grafting of specific chemical groups and degradation of

the polymer chain. These processes are in competition and which one predominates

depends on the type of the polymer as well as the applied dose.

They may be used alone, in different physical environments, or with the addition of

external additives and/or reactants to further improve the desired properties of the

polymer.

Post-Reactor Modification of Polyolefins

Crosslinking

Scission

Functionalization

Original

polymer

Polymer Modification

Macroradical

Changes induced by post-reactor modification

Molecular Weight and Molecular weight distribution.

Scission and Branching.

Network formation.

Consumption and/or insertion of specific chemical groups in the polymer chains.

These structural changes induce variations on

Viscosity and elasticity of the melt.

Mechanical properties.

Thermal behavior.

Surface properties.

Compatibility.

Changes induced by post-reactor modification

Irradiation of:

Commercial polyethylene

Commercial polypropylene

Model LLDPE (hydrogenated PB)

Copolymers of ethylene with a-olefines (hexene, octadecene)

Polydimethylsiloxane

EPDM

Peroxy modification of:

Commercial polyethylene

Commercial polypropylene

Model LLDPE (hydrogenated PB)

Copolymers of ethylene with a-olefines (hexene, octadecene)

EPDM

Grafting:

Commercial polyethylene with MAn to develope starch-PE blends

Commercial SBS with MAn and CMA to improve adhesion properties of SBS

surfaces

PE with CMA to develope PE-PA blends

PE with undecenoic acid

Irradiation and peroxide modification of model

polyethylenesHydrogenated polybutadiene (HPB)

Linear polybutadienes (PB) of different molecular mass were synthesized

by anionic polymerization of butadiene under high purity conditions

following standard methods. The polymerization was carried out in

cyclohexane solution, under high vacuum and at room temperature.

The resulting polybutadienes were subsequently hydrogenated in solution

of toluene using a Wilkinson's catalyst (RhCl(PPh)3). The hydrogenation

was performed at 90 °C in a Parr reactor, working at 700–psi of hydrogen

pressure.

The resulting polymer (HPB) has a molecular structure chemically similar

to a random ethylene–(butene-1) copolymer with a composition of about

20 CH3/1000C

Changes in Polydispersity with Irradiation Dose

Since the polymers used were practically monodisperse, SEC elution curves were very sensitive to changes in the molecular weight induced by the radiation treatment.

Polymer B; Mn=45,000 , PD=1,16, Gel dose ≈ 75 kGy

Polymer C; Mn=102,000 ,PD=1,09, Gel dose ≈ 35 kGy

4-5%

PRE-GEL POST-GEL(SOLUBLE FRACTION)

Polymer B

Main assumptions to model the irradiation of

Polyolefins

In the case of radiation, the process can be modeled assuming ideal network

formation:

Each chain is composed of a discrete number of repeat units.

The irradiation process is random, that is, all monomer units in a chain are

equally likely to be subject to crosslinking and all C–C bonds are equally likely

to be subject to scission

All reactions are independent and there are no intramolecular reactions

The ratio of crosslinking to scission is taken to be constant during the entire

irradiation process.

We also assume that the crosslinking and scission reactions are independent of

each other.

Modelling the Evolution of Molecular WeightNormalized MW vs. normalized gel dose

Modelling evolution of Gel Fraction

Proportion of gel (expressed as percentage) of the radiation modified HPB polymers

as a function of the normalized radiation dose (D/Dgel).

Irradiation and peroxide modification of

commercial polyethylenes (HDPE)

Influence of the terminal unsaturations on the crosslinking efficiency

There are four fundamental and inherent polymer properties that are of

significant importance for the crosslinking of polyethylene; molecular weight,

molecular weight distribution, tertiary carbons and amount and type of

unsaturations.

In several commercial polyethylenes unsaturations are formed during the

termination step of the polymerization resulting in vinyl groups at the end of

the molecular chains.

The presence of these groups affects the kinetics of the modification

reactions and the type of molecular structure, specially when peroxides are

employed.

Irradiation of metallocenic polyethylene and

ethylene- co- 1 hexene copolymersThis work is focused on the characterization of metallocenic ethylene/1-hexene (PEH) copolymers

with molar comonomer contents of 3.3, 9.2, 13.9, and 16.1% crosslinked by a wide range of doses

of g-rays under vacuum.

Satti et al, Journal of Applied Polymer Science, Vol. 117, 290–301 (2010)

The polymers were synthesized using a 1-L Parr reactor at 333 K with an ethylene

pressure of 2 bar. The catalyst/cocatalyst used was Et[Ind]2ZrCl2/MAO. The reaction

was carried in toluene solution for 30 min

The irradiation of the samples was performed at room temperature with a 60Co

g-source. The applied doses ranged from 7 to 103 kGy.

Size exclusion chromatography (SEC) 1,2,4-trichlorobenzene at 135C and 1.0 L/min

The amount of scission was

estimated to be about 2% of the

crosslinked material for all the

irradiated samples

Evolution of the molecular weight distribution

Branching detection by Sec-MALLS

Dgel=39.6kGy

lin2s

br2s

g

Branching detection by Sec-MALLS

Number of long chain branches per 1000 monomer units estimated employing the ASTRA software

from Wyatt Technology. This requires assuming the functionality of the branch points as tetrafunctional

.

Rheological response

As the amount of applied radiation grows, the location of Pc moves towards lower d and higher G*/GNo values revealing the

increasing concentration of branching with radiation.

Trinkle s. et al Rheol. Acta (2002) 41: 103-113

Structural Changes and Rheological Response to Different

Modification Procedures

DBPH=2-5 dimethyl-2-5 di(ter-butylperoxy)-hexane

Modelling the evolution of molecular weight and gel fraction

Evolution of Crystallinity with Irradiation Dose

Comparison of the rheological behavior of a vinyl containing HDPE and its

hydrogenated counterpart modified with increasing peroxide concentrations

Journal of Applied Polymer Science,Vol. 115, 1942–1951 (2010)

HDPE (Alathon 7050) Mw=46,700 g/mol and Mn of 17,600 g/mol. The polymer had a concentration of terminal

vinyl groups of 0.033 mol/L,

Comparison of the rheological behavior of a vinyl containing HDPE and its

hydrogenated counterpart modified with increasing peroxide concentrations

1E-1 1E+0 1E+1 1E+2 1E+3

[s -1]

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

G '(

) [P

a]

References

PE

PE-250

PE-500

PE-1000

T = 170 °C

Frequency dependence of elastic modulus, G’ () of HDPE

samples modified with different amounts of peroxide measured at

170 oC

1E-1 1E+0 1E+1 1E+2 1E+3

[s -1]

1E+0

1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

G '(

) [P

a]

T = 170 °C

References

HPE

HPE-250

HPE-500

HPE-1000

HPE-2000

HPE-8000

HPE-10000

Frequency dependence of elastic modulus, G’ () of

hydrogenated HDPE samples modified with different amounts

of peroxide measured at 170 oC

Journal of Applied Polymer Science,Vol. 115, 1942–1951 (2010)

HDPE (Alathon 7050) Mw=46,700 g/mol and Mn of 17,600 g/mol. The polymer had a concentration of terminal

vinyl groups of 0.033 mol/L,

DBPH

Irradiation commercial polyethylenes (HDPE)

Influence of the initial crystallinity

Two high-density polyethylenes PE1 Mw=56,900 ( DuPont de Nemours) and PE2 Mw=80,600 ( Oxy

Petrochemical) The polydispersity (Mw/Mn) was about 2.6 for both polymers.

Irradiation commercial polyethylenes (HDPE)

Influence of the initial crystallinity

Two high-density polyethylenes PE1 Mw=56,900 ( DuPont de Nemours) and PE2 Mw=80,600 ( Oxy

Petrochemical) The polydispersity (Mw/Mn) was about 2.6 for both polymers.

Mechanical behavior of irradiated PE with different degrees

of crystallinity

Polypropylene

Polypropylene

Polypropylene

Polypropylene

Polypropylene

Modificación de las Propiedades Reológicas

del Polipropileno

En el proceso de polimerización industrial más extendido se utilizan catalizadores detipo Ziegler-Natta. Esto permite obtener un polímero con un alto grado decristalinidad y buenas propiedades mecánicas.

El proceso de polimerización genera sin embargo un polímero con muchapolidispersión y colas de alto peso molecular que le confieren al fundido altaviscosidad y elasticidad.

200.000< Mw< 700.000 y 5< PD < 20

Esto dificulta el procesamiento del material e impide su utilización directa enprocesos rápidos, haciendo necesario su modificación para disminuir la influencia delas moléculas de alto peso molecular.

La modificación del PP mediante la utilización de peróxidos en un proceso postpolimerización de extrusión reactiva, permite disminuir la polidispersión mediante laescisión de las cadenas de alto peso molecular .

Modificación de las Propiedades Reológicas

del Polipropileno

Dimetil di-terbutil peroxi hexano (DBPH)

En los trabajos que aquí se reportan se

utilizó DBPH impregnado en PP al 20 %

M. Krell, A. Brandolin y E.M. Vallés. Polymer Reaction

Engineering, 2,4, 389-408 (1994)

Modificación de las Propiedades Reológicas

del Polipropileno

M. Krell, A. Brandolin y E.M. Vallés. Polymer Reaction Engineering, 2,4, 389-408 (1994)

Esquema general de reacciones en el proceso de degradación reactiva

El planteo de las ecuaciones de balance de masa genera un sistema de infinitas

ecuaciones diferenciales acopladas.

El sistema de infinitas ecuaciones diferenciales puede ser reducido a solo 8

ecuaciones aplicando el método de los momentos de la distribución de especies

moleculares.

Los momentos de una distribución se definen como:

Momentos de orden i del polímero:

Momentos de orden i de los radicales:

Pesos moleculares promedio:

Pm = peso molecular del monómero

i

ni ][P nM

1i

io

ni ][P nD

1i

o0

11

DM

DMPmMn

11

22

DM

DMPmMw

Modificación de las Propiedades Reológicas

del Polipropileno

M. Krell, A. Brandolin y E.M. Vallés. Polymer Reaction Engineering, 2,4, 389-408 (1994)

Modificación de las Propiedades Reológicas

del Polipropileno

M. Krell, A. Brandolin y E.M. Vallés. Polymer Reaction Engineering, 2,4, 389-408 (1994)

Polypropylene

The employment of a polyfunctional monomer triallylisocyanurate (TAIC) allows a

significant improvement in the degree of crosslinking. A master batch of

polypropylene containing 10 wt% TAIC was prepared using a twin screw extruder

C.Friedrich et al, Rheol Acta (2003) 42: 251–258

Polypropylene

PP lineal con un grado de injerto de anhídrido maleico del 1% (Polybond 3200, Mw=120Kg/mol,

Mw/Mn=2.6) modificado con dosis entre 0.1% y 5% en peso de glicerol como agente

entrecruzante. La modificación se realizó por mezclado reactivo a 190 C

J. Guapacha et al, to be published

Polypropylene

PP lineal con un grado de injerto de anhídrido maleico del 1% (Polybond 3200, Mw=120Kg/mol,

Mw/Mn=2.6) modificado con dosis entre 0.1% y 5% en peso de glicerol como agente entrecruzante. La

modificación se realizó por mezclado reactivo a 190 C

J. Guapacha et al, to be published

1E-006 1E-005 0.0001 0.001 0.01 0.1

G*/G0N

40

60

80

d

1E-006 1E-005 0.0001 0.001 0.01 0.1

40

60

80

Pg

PgG01

PgG02

PgG03

PgG05

PgG1

PgG5

0.001 0.01 0.1 1 10 100 1000

s-1

100

1000

10000

Pa.s

0.001 0.01 0.1 1 10 100 1000

100

1000

10000

PgG5

PgG1

PgG05

PgG03

PgG02

PgG01

Pg

Figura 2. Grafica de van Gurp Palment. Angulo de perdida (δ)

vs. G*/GN0 a 180 C.­­

Figura 3. Viscosidad dinámica (η*) en función de la

frecuencia (ω).

Metallocene Epdm Terpolymers

with High Diene and Propylene Content

The materials used were two metallocene EPDM grades

supplied by DuPont-Dow Elastomers: NORDEL IP 4570

(EPDM-1), Mooney viscosity 70 and NORDEL IP 5565

(EPDM-2), Mooney viscosity 65, with 5 wt.-% and 7 wt.-%

ethylidenenorbornene (ENB) respectively

j. Nicolás et al., Macromol. Chem. Phys. 2004, 205, 2080-2088

Metallocene Epdm Terpolymers

with High Diene and Propylene Content

Metallocene Epdm Terpolymers

with High Diene and Propylene Content

Metallocene Epdm Terpolymers

with High Diene and Propylene Content

Melt Grafting of Polyolefins

Polythylene, Polybutadiene,SBS, Polypropylene

J. Applied Polymer Science (102) 4468-4477 (2006).

J. Polymer Science. Part A: Polymer Chemistry, 40, 3950-3958, (2002)