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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
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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
Post-Reactor Modification of Polyolefins
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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.
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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.
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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.
Polymer Modification
Crosslinking
Scission
Functionalization
Original
polymer
Macroradical
Changes induced by post-reactor modification
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Molecular Weight and Molecular weight distribution.
Scission and Branching.
Network formation.
Consumption and/or insertion of specific chemical groups in the
polymer chains.
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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
polyethylenes
Hydrogenated 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.
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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
Polymer B
POST-GEL
PRE-GEL
(SOLUBLE FRACTION)
4-5%
Main assumptions to model the irradiation of
Polyolefins

In the case of radiation, the process can be modeled assuming ideal network
formation:
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Each chain is composed of a discrete number of repeat units.
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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
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All reactions are independent and there are no intramolecular reactions
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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 Weight
Normalized 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 copolymers
This 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.
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
Satti et al, Journal of Applied Polymer Science, Vol. 117, 290–301 (2010)
Evolution of the molecular weight distribution
The irradiation of the samples was performed at room temperature with a 60Co
g-source. The applied doses ranged from 7 to 103 kGy.
The amount of scission was
estimated to be about 2% of the
crosslinked material for all the
irradiated samples
Size exclusion chromatography (SEC) 1,2,4-trichlorobenzene at 135C and 1.0 L/min
Branching detection by Sec-MALLS
Dgel=39.6kGy
g
 s2 
 s2 
br
lin
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
Trinkle s. et al Rheol. Acta (2002) 41: 103-113
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.
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
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,
Journal of Applied Polymer Science,Vol. 115, 1942–1951 (2010)
Comparison of the rheological behavior of a vinyl containing HDPE and its
hydrogenated counterpart modified with increasing peroxide concentrations
1E+6
1E+6
1E+5
1E+5
1E+4
1E+4
G '() [Pa]
G '() [Pa]
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
1E+3
T = 170 °C
References
1E+2
T = 170 °C
1E+3
References
HPE
HPE-250
1E+2
PE
HPE-500
HPE-1000
PE-250
PE-500
1E+1
HPE-2000
1E+1
PE-1000
HPE-8000
HPE-10000
1E+0
1E-1
1E+0
1E+1
 [s
1E+2
1E+3
-1]
Frequency dependence of elastic modulus, G’ ( ) of HDPE
samples modified with different amounts of peroxide measured at
170 oC
1E+0
1E-1
1E+0
1E+1
 [s
1E+2
1E+3
-1]
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)
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 de
tipo Ziegler-Natta. Esto permite obtener un polímero con un alto grado de
cristalinidad y buenas propiedades mecánicas.
 El proceso de polimerización genera sin embargo un polímero con mucha
polidispersión y colas de alto peso molecular que le confieren al fundido alta
viscosidad y elasticidad.

200.000< Mw< 700.000
y
5< PD < 20
 Esto dificulta el procesamiento del material e impide su utilización directa en
procesos rápidos, haciendo necesario su modificación para disminuir la influencia de
las moléculas de alto peso molecular.
 La modificación del PP mediante la utilización de peróxidos en un proceso post
polimerización de extrusión reactiva, permite disminuir la polidispersión mediante la
escisión 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
Esquema general de reacciones en el proceso de degradación reactiva
M. Krell, A. Brandolin y E.M. Vallés. Polymer Reaction Engineering, 2,4, 389-408 (1994)
Modificación de las Propiedades Reológicas
del Polipropileno
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:
M i   n [Pn ] i
i 1
Momentos de orden i de los radicales:
Pesos moleculares promedio:
Pm = peso molecular del monómero

Di   n [Pn ] i
o
i 1
Mn  Pm
M1  D1
M0  Do
Mw  Pm
M. Krell, A. Brandolin y E.M. Vallés. Polymer Reaction Engineering, 2,4, 389-408 (1994)
M2  D2
M1  D1
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
1E-006
1E-005
0.0001
0.001
0.01
0.001
0.1
0.01
0.1
1
10
100
1000
10000
PgG5
PgG1
PgG05
PgG03
PgG02
PgG01
Pg
60
60
Pg
PgG01
PgG02
PgG03
PgG05
PgG1
PgG5
40
1E-006
1E-005
Pa.s
80
d
80
10000
1000
1000
100
100
40
0.0001
0.001
0.01
0.1
0.001
G*/G0N
0.1
1
10
100
1000
s-1
Figura 2. Grafica de van Gurp Palment. Angulo de perdida (δ)
vs. G*/GN0 a 180 C.--
0.01
Figura 3. Viscosidad dinámica (η*) en función de la
frecuencia (ω).
J. Guapacha et al, to be published
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)