Materials Sciences and Applications, 2012, 3, 575-579 Published Online August 2012 (
PET Oligomer Waste to Modify CAP Characteristics
L. C. Mendes*, M. L. Dias, P. S. C. Pereira, L. M. R. Albuquerque
Centro de Tecnologia, Instituto de Macromoléculas Professora Eloisa Mano-IMA, Universidade Federal do Rio de Janeiro-UFRJ,
Rio de Janeiro, Brazil.
Email: *
Received May 16th, 2012; revised June 10th, 2012; accepted July 12th, 2012
To develop an improved method of reusing poly(ethylene terephthalate) (PET) waste in the production chain, it was
chemically modified with pentaerythritol (PENTE), resulting in PET/PENTE (60/40) oligomer. This was added to
petroleum asphalt cement (CAP) in different proportions—5, 10 and 20 wt%—as a modifier of bitumen characteristics.
The mixture was evaluated by thermogravimetry (TG/DTG), differential scanning calorimetry (DSC), infrared spec-
troscopy (FT-IR), optical microscopy (OM) and the adhesion-peel test. The oligomer enhanced substantially the asphalt
thermal stability-Tonset. OM images showed strong compatibility between components and PET’s amorphization. PET
oligomer increased CAP’s wettability and the mixture presented cohesive fracture through the peel test. The mixture has
excellent potential as paving material.
Keywords: PET Waste; Pentaerythritol; CAP; Recycling
1. Introduction
In recent years, the growing use of polymers in everyday
products has generated an enormous amount of munici-
pal solid waste. This has brought many environmental
problems. In general, these wastes take long time to un-
dergo spontaneous degradation and release toxic gases if
they are burned [1,2]. The majority of discarded polymer
materials are from packaging. Taking into account the
huge potential of plastics and the problems caused by
pollution from waste, there is a growing worldwide trend
to recycle them [3]. When reused, PET packages show
several advantages—lower consumption of water and
energy and environmental and social benefits, among
others [4]. Waste disposal is a main concern of society,
prompting actions by industry and research centers [5-7].
Recently, an article on PET waste oligomerization through
the action of polyfunctional alcohol—pentaerythritol was
published [8].
Polymers have been studied as modifiers of asphalt
mainly to overcome some deficiencies of asphalt cement
and to improve its properties, such as reducing perma-
nent thermal deformation and cracking. As modifier
agents, polymers are compatible and increase asphalt de-
gradation at high temperatures. The asphalt’s characteris-
tics as well as the type and amount of polymer have a
large influence on the appropriate asphaltic mixture [9,
Asphalt cement can be formed naturally, through eva-
poration of surface oil deposits, but the majority comes
from the heavy fraction of petroleum from distillation at
refineries. Petroleum asphalt cement (CAP) consists of
90% - 95% hydrocarbons—saturated and aromatic—and
5% - 10% of structures with hetero atoms (oxygen, sulfur,
nitrogen) and metals, such as vanadium, nickel and iron.
Brazilian CAPs have low sulfur and metals content but
high levels of nitrogen. Asphaltenes and maltenes are the
main asphalt components. They are complex mixtures
consisting of condensed aromatic rings, resins and satu-
rated and aromatic compounds. The ratio between as-
phaltenes and maltenes has a significant effect on asphalt
performance [11-14]. The reuse of plastics as additives
for CAP increases the possibility of using urban plastic
waste in the productive chain [15,16].
This work intended to develop a new material from
plastic arising from municipal solid waste. The discarded
PET was oligomerized by a polyfunctional alcohol. The
PET oligomer was mixed with CAP in different propor-
tions to evaluate its influence on the CAP’s thermal, ad-
hesive and morphological characteristics.
2. Experimental
2.1. Materials
Flakes of poly (ethylene terephthalate) (PET) waste with
24% crystallinity degree were supplied by CPR Ltd. (Rio
de Janeiro, Brazil). Commercial pentaerythritol, here
*Corresponding author.
Copyright © 2012 SciRes. MSA
PET Oligomer Waste to Modify CAP Characteristics
called PENTE, was provided by S. A. Degussa (São
Paulo, Brazil). Commercial zinc acetate produced by J. T.
Baker was used without further purification. The asphalt
cement was from a refinery.
2.2. Oligomer Preparation
This measurement and others are deliberate, using speci-
fications that anticipate your paper as one part of the en-
tire proceedings, and not as an independent document.
Please do not revise any of the current designations. The
PET/PENT (60/40) blend containing 0.5 wt% zinc ace-
tate catalyst was prepared by melt processing in an Ha-
ake Rheomix 600 internal mixer, at 250˚C, 60 rpm, for
10 minutes. Before processing, PET flakes were previ-
ously dried at 120˚C, for 4 hours [8].
2.3. CAP/Oligomer Mixture
The mixture of CAP with PET/PENTE oligomer in dif-
ferent oligomer proportions (5, 10 and 20 wt%), called
CAP (95/5), CAP (90/10) and CAP (80/20), respectively,
was prepared in a 500 mL glass flask, at 180˚C, with
mechanical stirring (600 rpm) for 2 hours.
2.4. Thermogravimetry and Derivative
Thermogravimetry (TG/DTG)
The TG/DTG curves were obtained by a TA thermoana-
lyzer (Q500) by heating the sample from 30˚C to 700˚C
at a heating rate of 10˚C·min 1 under nitrogen atmos-
phere. The onset temperature (Tonset), maximum degrada-
tion temperature (Tmax) and end temperature (Tend) were
2.5. Differential Scanning Calorimetry (DSC)
Calorimetric measurements were carried out in a TA
calorimeter (Q1000). The sample was heated from 20˚C
to 100˚C at a heating rate of 10˚C·min 1 under nitrogen
atmosphere (first scan), kept for 2 min to erase the ther-
mal history, and then cooled to 20˚C at the maximum
(second scan). A second heating cycle (third scan) was
performed with the same protocol as the first scan. The
variation in the baseline was evaluated considered the
PET glass transition temperature, Tg, and CAP thermal
transition temperature [17-19].
2.6. Morphological Analysis
The morphology was analyzed under a Zeiss model
THMS 600 microscope from squeezed film between two
glass slides. The assembly was inserted into the micro-
scope in the hot stage and heated from 25˚C to 280˚C,
where it was kept for 2 minutes to eliminate the thermal
history. After that, the cooling was performed until 25˚C.
The morphology of the matrix and dispersed phase was
monitored by taking photographs.
2.7. Peel Test
The adhesive characteristic of the asphaltic mixture was
evaluated based on the ASTM D1876 standard [20]. The
material was poured between aluminum plates with con-
stant thickness and the assembly was taken for peeling in
an Instron machine. The force of peeling was registered
and then test photos were taken to evaluate what kind of
fracturing—adhesive or cohesive had occurred.
3. Results and Discussion
3.1. Thermogravimetry and Derivative
Thermogravimetry (TG/DTG)
Figures 1 and 2 show the degradation and first derivative
curves of the materials, respectively. Table 1 contains
the Tonset, Tmax, and Tend degradation temperatures and
amount of residue. The PET/PENT 60/40 blend pre-
sented three degradation steps. The first one was located
at 100˚C - 175˚C and it was attributed to the absorbed
water. The next one occurred at 250˚C - 325˚C, caused
by the unreacted pentaerythritol. The final step, at 325˚C
- 525˚C, was the result of the degradation process of the
PET/PENTE oligomers.
The CAP’s curve shows a unique degradation step
pattern. Concerning the mixture CAP/oligomer, all of
them presented one stage of degradation. The Tonset and
Tmax were shifted to higher temperatures, indicating a
substantial increase of the CAP’s thermal stability and a
higher degree of compatibility.
3.2. Differential Scanning Calorimetry (DSC)
Figure 3 shows the DSC curves of the PET/PENTE,
CAP and CAP (90/10). The oligomer showed Tg around
61˚C. The CAP presented a thermal transition in the vi-
cinity of 13˚C. All mixtures revealed the same transitions
but that attributed to the Tg of the oligomer shifted to a
lower temperature (43˚C). This corroborated the high
Table 1. TG/DTG of the materials.
temperatures (˚C)
Tonset T
PET/PENTE 60/40125 495 127/285/4769.22
CAP 258 500 441 14.1
CAP (95/5) 238 488 448 0.03
CAP (90/10) 250 490 453 11.9
CAP (80/20) 281 496 448 11.3
Copyright © 2012 SciRes. MSA
PET Oligomer Waste to Modify CAP Characteristics
Copyright © 2012 SciRes. MSA
Figure 1. TG curves of the materials.
Figure 2. DTG curves of the materials.
The crystalline phase—disperse droplets is embedded in
the amorphous phase.
degree of compatibility observed in the TG/DTG analy-
The CAP (95/5) photomicrographs did not reveal any
phase separation. This might have occurred because of
the total dissolution of CAP inside the oligomer matrix.
In the mixtures with oligomer content higher than 5%,
the oligomer induced the fragmentation of the crystalline
domains. There is a sharp phase separation. The matrix is
formed by oligomer and the CAP amorphous phase. The
3.3. Units Morphological Analysis
The photomicrographs of the CAP (Figure 4) and CAP/
Oligomer mixture (Figure 5) show the morphology of
the materials in the solid and molten states. The CAP’s
images are similar and represent a heterogeneous mixture.
PET Oligomer Waste to Modify CAP Characteristics
Figure 3. First heating DSC curves of the materials.
(a) (b)
Figure 4. Optical fotographs. CAP: (a) Molten state; (b)
Solid state.
crystalline phase appeared as dispersed small droplets.
3.4. Peel Test
Figure 6 shows the force required immediately before
complete separation of the aluminum plates. For the mix-
tures, even taking into account the experimental errors,
the values of the force were similar, independent on the
oligomer content. The mixtures presented behavior simi-
lar to that of a ductile material.
Figure 7 shows the surface of the aluminum plates
after the peel test. The CAP image revealed voids on the
surface, indicating poor adhesion. For all mixtures, the
oligomer improved adhesion. All surfaces were com-
pletely coated, showing cohesive fracture of the asphaltic
mixture. The results indicated that the presence of the
oligomer increases the resistance to disaggregation and
durability of the asphaltic mixture, making it more suit-
able for paving.
4. Conclusion
In order to produce a new material from plastic waste,
PET was oligomerized by a polyfunctional alcohol and
mixed with CAP. The asphaltic mixture was character-
ized by several techniques. The DSC showed there is
excellent compatibility between the constituents. The
(a) (b)
(c) (d)
(e) (f)
Figure 5. Optical fotographs of CAP/oligomer mixture.
CAP (95/5): (a) Molten state; (b) Solid state; CAP (90/10):
(c) Molten state; (d) Solid state; CAP (80/20): (e) Molten
state; (f) Solid state.
Figure 6. Pell test of the materials.
presence of the oligomer enhanced the CAP’s thermal
stability. Morphologically, in the mixtures, PET was the
matrix and the CAP crystalline phase appeared as dis-
perse domains. The mixture presented cohesive fracture
and ductile behavior from the peeling evaluation.
5. Acknowledgements
The authors thank Fundação Coordenação do Aperfei-
çoamento de Pessoal de Nível Superior (CAPES) and
Copyright © 2012 SciRes. MSA
PET Oligomer Waste to Modify CAP Characteristics
Copyright © 2012 SciRes. MSA
(a) (b)
(c) (d)
Figure 7. Surface of the aluminum plates after the peel test:
(a) CAP; (b) CAP (95/5); (c) CAP (90/10); (d) CAP (80/20).
Universidade Federal do Rio de Janeiro (UFRJ) for sup-
porting this investigation.
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