PERFORMANCE OF AN ENVIRONMENTAL PROTECTION LINER AFTER LABORATORY UV EXPOSURE

Abstract

High-density polyethylene (HDPE) geomembranes are commonly used as an environmental protection liner due to their good chemical and mechanical resistances and low cost. Ultraviolet (UV) radiation is an essential issue in durability studies for pond applications. This study evaluated a 1.5-mm thick HDPE geomembrane exposed to ultraviolet fluorescent radiation for 8760 h in a laboratory and thermoanalytical and physical analyses were conducted towards the understanding of its performance after exposure. According to the results, although the geomembrane maintained the ductile behavior, it showed a 52.48% final decrease in stress crack resistance (SCR) compared to virgin SCR. Moreover, a considerable antioxidant depletion occurred after 8760 h exposure shown by the Std. OIT (standard oxidative-induction time) results, demonstrating a Std. OIT value decrease of 89.19% compared to the virgin Std. OIT. Such a behavior contributed to the susceptibility of thermal effects in the DSC (differential scanning calorimetry) curves and the losses observed in the SCR values, attesting the geomembrane's oxidative degradation mechanism occurred and changed the polymer's structure.

Full text

Quim. Nova, Vol. 48, No. 2, e-20250019, 1-6, 2025 http://dx.doi.org/10.21577/0100-4042.20250019
*e-mail: fernando.lavoie@usp.br
PERFORMANCE OF AN ENVIRONMENTAL PROTECTION LINER AFTER LABORATORY UV EXPOSURE
Fernando Luiz Lavoiea,*,, Marcelo Kobelnika, Clever Aparecido Valentina, Érica Fernanda da Silva Tirellib, Maria de
Lurdes Lopesc and Jefferson Lins da Silvaa
aEscola de Engenharia de São Carlos, Universidade de São Paulo, 13566-590 São Carlos – SP, Brasil
bDepartamento de Engenharia Civil, Instituto Mauá de Tecnologia, 09580-900 São Caetano do Sul – SP, Brasil
cCONSTRUCT-GEO, Departamento de Engenharia Civil, Universidade do Porto, 4200-465 Porto, Portugal
Received: 09/28/2023; accepted: 03/25/2024; published online: 06/06/2024
High-density polyethylene (HDPE) geomembranes are commonly used as an environmental protection liner due to their good
chemical and mechanical resistances and low cost. Ultraviolet (UV) radiation is an essential issue in durability studies for pond
applications. This study evaluated a 1.5-mm thick HDPE geomembrane exposed to ultraviolet uorescent radiation for 8760 h in a
laboratory and thermoanalytical and physical analyses were conducted towards the understanding of its performance after exposure.
According to the results, although the geomembrane maintained the ductile behavior, it showed a 52.48% nal decrease in stress crack
resistance (SCR) compared to virgin SCR. Moreover, a considerable antioxidant depletion occurred after 8760 h exposure shown by
the Std. OIT (standard oxidative-induction time) results, demonstrating a Std. OIT value decrease of 89.19% compared to the virgin
Std. OIT. Such a behavior contributed to the susceptibility of thermal effects in the DSC (differential scanning calorimetry) curves
and the losses observed in the SCR values, attesting the geomembrane’s oxidative degradation mechanism occurred and changed
the polymer’s structure.
Keywords: geomembrane; high-density polyethylene; ultraviolet radiation; durability; physical and thermal analysis.
INTRODUCTION
Geosynthetics used as environmental protection barriers
are polymeric sheets with low permeability coefficients; they
are sometimes combined with natural materials, industrially
manufactured, and installed in the field. Geomembranes are a
type of geosynthetics commonly employed for landll liners since
the 1970s. However, they are currently applied as a liner in water
ponds, industrial waste ponds, and waste liquid ponds. High-density
polyethylene (HDPE) geomembranes show high chemical and
mechanical resistance, associated with a low manufacturing cost and a
very low permeability coefcient, i.e., typically 10-11 to 10-13 cm s-1.1-6
Geomembranes are exposed to climate conditions during the
construction time for landll applications. However, regarding pond
applications, exposure to climate conditions on slopes above the
water table continues for a lifetime and an exposed geomembrane
can initiate UV, thermal, and oxidative degradations. Such aging
mechanisms can inuence the properties of the materials, decreasing
durability7,8 and the synergy between UV radiation and thermal
exposure can degrade the material.9,10 When UV radiation reaches
the geomembrane surface, photo-oxidation starts to act, generating
several free radical reactions, hence, degradation and polymer chain
scission and polymer property degradation.11,12
The oxidation process of HDPE degradation starts with the
free radical chain mechanism. The oxidation mechanism involves
two cycle processes, namely, a chain reaction of alkyl/alkylperoxyl
and formation of new radicals by chain reaction (homolysis of
hydroperoxides). Oxidation can be stopped if all links are blocked.13,14
The HDPE geomembrane formulation includes 2-3% of UV
protection (usually carbon black) and 0.5-1.0% of two different
types of antioxidants (primary and secondary) are used to prevent
the oxidation of the polymer during extrusion and guarantee the
longevity of the material.15,16
Several studies have analyzed the inuence of UV radiation
and weather effects on HDPE materials. Sahu et al.17 studied
1 to 3% carbon black concentrations in an HDPE using a
UV fluorescent weatherometer for 192 h and both differential
scanning calorimetry (DSC) and Fourier transform infrared
spectroscopy (FTIR) analyses revealed the total carbon black
concentrations protected the resin adequately with no HDPE
degradation. Reis et al.18 chose eight different regions in Portugal for
analyses of ve 2.0mm-thick HDPE geomembranes after 12 years
of eld exposure. Locations in the country with higher UV indexes
suggest an impact on tensile properties and antioxidant depletion.
The study also demonstrated that HDPE geomembranes covered with
nonwoven geotextiles and uncovered displayed the same behavior.
Lavoie et al.19 evaluated the nal condition of a 0.8 mm-thick HDPE
geomembrane that had been over 15 years in contact with waste
and environmental conditions in a biodegradable waste pond. The
exhumed sample exhibited brittle tensile behavior, low stress crack
resistance, and almost an entire antioxidant depletion, leading to
the conclusion its nal condition would cause a rupture, hence, an
environmental impact on the site. Lavoie et al.20 analyzed an HDPE
geomembrane exhumed from a liner in an industrial water pond after
2.25 years of operation and the results showed a mechanical brittle
behavior, indicating changes in the polymer morphology.
Safari et al.21 studied the antioxidant depletion of an exhumed
HDPE geomembrane installed 25 years ago in a hazardous waste
landll in Canada. The samples were exhumed from the bottom
and the cover liners. The authors concluded the Std. OIT (standard
oxidative-induction time) test values and some HP OIT (high-
pressure oxidative-induction time) test levels were signicantly
lower than those of a modern virgin geomembrane and the exposure
conditions signicantly inuenced the antioxidant depletion of the
geomembrane. Mendes et al.22 analyzed the behavior of an HDPE
using a phenol-type antioxidant and two HALS-type light stabilisers
(hindered amine light stabilizer) as additives in the HDPE resin after
4000 h weathering exposure in Rio de Janeiro, Brazil. The samples
Article

Lavoie et al.
2Quim. Nova
were compared with and without additives. The former displayed a
good behavior after exposure, whereas those with no additives showed
losses in ductility, an increase in crystallinity, and a reduction in the
molecular weight.
This study evaluated the behavior of a virgin 1.5-mm thick
HDPE geomembrane after a UV uorescent exposure for 8760 h.
Thermoanalytical and physical analyses were conducted towards the
understanding of the nal conditions of the sample.
EXPERIMENTAL
HDPE geomembrane
A 1.5 mm-thick HDPE smooth geomembrane provided by a
Brazilian manufacturer, formulated with 96-97.5% medium-density
polyethylene (density ≥ 0.940 g cm-3), 2-3% anti-UV additive
(carbon black), 0.5-1.0% thermostabilizers and antioxidants,23 and
produced by the extrusion blown lm process was used. According
to Ewaiset al.,24 antioxidants, stabilisers, and carbon black retard
polymer degradation due to photo-oxidation and thermal oxidation.
Accelerated weathering exposure
A UV-weathering chamber, model EQUV Philips, from Equilam
(Diadema, Brazil) with uorescent UVA-340 lamps was used and
programmed to work in cycles of 20 ± 0.01 h of UV light at 75±1°C
followed by 4 ± 0.01 h of condensation at 50 ± 0.01 °C25 for 960,
4380, and 8760 ± 0.01 h.
Melt ow index (MFI) test
A plastometer, model CEAST MF20, manufactured by Instron
(Norwood, USA) ran the MFI test.26 The material was extruded at
190 ± 0.08 °C with a 5.0 ± 0.01 kg of deadweight in a smooth bore
of 2.095 ± 0.005 mm (diameter) and 8000 ± 0.025 mm (length) and
then measured by an analytical balance with 0.0001 g precision in
10 ± 0.01 min.
Tensile test
The tensile test27 was conducted in a universal machine with
a 2-kN load cell, pneumatic grips, IV dog bone specimen, and at
50±0.05 mm min-1 test speed. The material was analyzed regarding
tensile at break in the machine direction, model DL 3000 (EMIC,
São José dos Pinhais, Brazil).
SCR test
The stress cracking was evaluated in equipment manufactured by
WT Indústria (São Carlos, Brazil) with capacity to test 20 specimens
simultaneously. The NCTL-SP (notched constant tensile load test -
single point)28 prescribes the specimen’s immersion in a solution with
10 ± 1% Igepal CO 630 and 90 ± 1% water at 50 ± 1 °C and application
of 30% of the sample’s yield strength (10 g precision) in ve specimens
notched with 20% of their thicknesses (0.001 mm precision). The result
was recorded in rupture time with 1 second precision.
OIT tests
OIT tests were conducted in two phases, i.e., an endothermic
reaction with nitrogen gas purge followed by specimen oxidation,
both in a DSC equipment model Q20 manufactured by TA Instruments
(New Castle, USA). The Std. OIT29 was conducted at 200 ± 2 °C with
140 ± 5 kPa constant oxygen pressure, 20 ± 1 °C min-1 heating rate,
and 50 ± 5 mL min-1 ow rate, whereas the HP OIT30 was conducted
at 150 ± 0.5 °C with 20 ± 1 °C min-1 heating rate and 3.4 ± 0.06 MPa
constant oxygen pressure.
DSC analysis
The analysis was performed in a DSC equipment model
Q20 manufactured by TA Instruments (New Castle, USA) using
nitrogen gas purge with 50 ± 5 mL min-1 ow, an aluminum crucible
with 10± 0.5 mg sample mass, 10 ± 1 °C min-1 heating rate, and
25to200±2 °C temperature range.
RESULTS AND DISCUSSION
Sample characterisation results
Table 1 shows the initial and minimum property values of the
samples required by American standard GRI-GM13.31
The characterisation results of the sample showed non-compliance
with the American standard for the HP OIT test results, since the
Table 1. Initial property values of HDPE geomembrane samples and minimum property values required by the American standard
Property Method Mean value ± SD GRI-GM13
Thickness / mm ASTM D519932 1.652 ± 0.039 ≥ 1.50
Density / (g cm-3) ASTM D79233 0.945 ± 0.001 ≥ 0.940
MFI (5 kg/190 °C) / (g 10 min-1) ASTM D123826 0.5054 ± 0.0102 -
Carbon black content / % ASTM D421834 2.92 ± 0.12 2.0-3.0
Carbon black dispersion (category) ASTM D559335 10 different views in category I 10 different views: 9 in categories I or
II and 1 in category III
Tensile break resistance / (kN m-1) ASTM D669327 46.93 ± 7.04 ≥ 40
Tensile break elongation / % ASTM D669327 704.67 ± 101.30 ≥ 700
Tear resistance / N ASTM D100436 242.53 ± 0.40 ≥ 187
Puncture resistance / N ASTM D483337 677.30 ± 16.47 ≥ 480
SCR / h ASTM D539728 629.84 ± 67.55 ≥ 500
Std. OIT / min ASTM D389529 199.78 ± 4.03 ≥ 100
HP OIT / min ASTM D588530 287.25 ± 1.06 ≥ 400
SD: standard deviation; MFI: melt ow index; SCR: stress crack resistance; Std. OIT standard oxidative-induction time: HP OIT: high-pressure oxidative-
induction time.

Performance of an environmental protection liner after laboratory UV exposure 3Vol. 48, No. 2
minimum HP OIT value required is 400 min. However, the HP OIT test
result was approximately 70% of the minimum value required, showing
the additive package of the sample probably has no HALS. Moreover,
the tensile elongation test result showed a high standard deviation.
MFI test results
Table 2 shows the MFI test results for both virgin and
UVuorescent exposure samples after 960, 4380, and 8760 h and
Figure 1 displays the behavior of the samples after exposure, exhibited
in retained MFI results.
According to Gulec et al.,38 the MFI test is commonly used as
a molecular weight index for chemical compatibility studies; it is
also a simple method for assessments of a molecular weight of the
polymer. Minor variations in MFI test results were observed among
the exposure samples. After 960 h of exposure, the result increased
0.68%; however, after 4380 and 8760 h of exposure, they decreased
0.18 and 1.51%. The MFI result after 8760 h demonstrates an
inuence of UV exposure on the polymer.
Tensile test results
The tensile properties evaluated were resistance and elongation
at break. Table 3 shows the results for both virgin and UV uorescent
exposure samples after 960, 4380, and 8760 h and Figure 2 displays
the behavior of the samples after exposure, exhibited in retained
tensile properties results.
Firstly, the virgin sample showed a high standard deviation due
to a 39.25 kN m-1 tensile resistance at break and a 596.50% tensile
elongation at break of the specimen.
The tensile resistance at break results decreased 5.48, 13.97,
and 11.60%, respectively, for 960, 4380, and 8760 h UV exposure,
compared to the virgin sample. On the other hand, the tensile
elongation at break decreased 6.44, 8.85, and 7.20%, respectively,
for 960, 4380, and 8760 h UV exposure compared to the virgin
sample. The slight increase in the tensile properties’ values
between 4380 and 8760 h can be attributed to a variation in the
manufacturing process. Koerner et al.39 exposed a 1.5mm-thick
HDPE geomembrane for 28,000 h using a UV fluorescent
weatherometer. The sample showed an approximately 20% higher
decrease in the tensile properties (resistance and elongation) in
comparison to the present study.
Lavoie et al.40 analyzed a 1.0 mm-thick HDPE geomembrane after
8760 h of UV uorescent exposure and reported an approximately
30% decrease in both resistance and elongation tensile values during
the exposure times. The sample analyzed in the present study showed
lower decreases in the tensile properties values after UV exposure,
hence, a better behavior.
SCR test results
Table 4 shows the SCR test results for both virgin and
UVuorescent exposure samples after 960, 4380, and 8760 h and
Figure3 displays the behavior of the sample after exposure, exhibited
in retained SCR.
The SCR results after 960, 4380, and 8760 h UV exposure
decreased, respectively, 6.75, 20.36, and 52.48%, compared to
the initial value. The SCR retained value after 1 year (8760 h) of
laboratory UV exposure obtained in this study (47.52%) is similar
to the SCR mean retained value reported by Rowe et al.41 for eleven
Table 2. MFI test results after UV uorescent exposure and retained MFI test
values compared with the virgin sample values
Exposure time / h MFI mean value ± SD /
(g 10 min-1)MFI / %
0 0.5054 ± 0.0102 100.0
960 0.5088 ± 0.0132 100.68
4380 0.5045 ± 0.0225 99.82
8760 0.4978 ± 0.0109 98.49
SD: standard deviation. MFI: melt ow index.
Figure 1. Retained MFI test results compared with virgin sample test result
after UV uorescent exposure
Table 3. Tensile test results (resistance and elongation at break) after UV uorescent exposure and retained tensile test values compared with the virgin sample
values
Exposure time / h Tensile resistance
mean value ± SD / (kN m-1)Tensile resistance / % Tensile elongation
mean value ± SD / % Tensile elongation / %
0 46.93 ± 7.04 100.0 704.67 ± 101.30 100.0
960 44.36 ± 0.48 94.52 659.30 ± 5.83 93.56
4380 40.37 ± 1.47 86.03 642.30 ± 17.46 91.15
8760 41.48 ± 3.47 88.40 653.90 ± 61.35 92.80
SD: standard deviation.
Figure 2. Retained tensile test results (resistance and elongation at break)
compared with virgin sample test result after UV uorescent exposure

Lavoie et al.
4Quim. Nova
HDPE geomembranes immersed in leachate (37%), who suggest
the SCR value can stabilize after 3 months of leachate incubation.
OIT test results
Table 5 shows the Std. OIT and HP OIT test results for both virgin
and UV uorescent exposure samples after 960, 4380, and 8760 h
and Figure 4 displays the behavior of the samples after exposure,
exhibited in retained OIT values.
The Std. OIT test results decreased 16.48, 27.99, and 89.19%,
respectively, for 960, 4380, and 8760 h of UV exposure in comparison
to the virgin sample result. A considerable decrease in the Std. OIT
results was observed between 4380 and 8760 h of UVexposure. After
1-year exposure, the depletion of the antioxidants was almost complete
and chain reaction and molecular composition started. Lavoie et al.42
evaluated two 1.0 mm-thick exhumed HDPE geomembranes in mining
facility constructions in Brazil and both showed low Std. OIT values,
brittle tensile behavior, and low SCR values.
Nonetheless, the HP OIT test results decreased 6.52, 29.74, and
53.15%, respectively, for 960, 4380, and 8760 h of UV exposure
compared to the initial value and decreased less than the Std. OIT test
results. According to Abdelaal and Rowe,43 the HP OIT test results
after HDPE geomembrane samples heat exposure conducted to a high
residual value. However, Lavoie et al.44,45 obtained HP OIT value equal
zero for one of the analyzed samples in the research, demonstrating
that is possible to completed deplete the antioxidants for this test.
DSC analysis
Figure 5 shows the DSC curves for the rst and second heatings
(Figure 5a) to verify the behavior of melting point and cooling
(Figure5b) and understand the behavior of the crystallisation point.
The rst heating (except for the virgin sample) led to a deviation in
the DSC curve before the melting point in the following temperature
ranges: 96-105 °C for the 8760 h-sample, 82-93 °C for the
4380h-sample, and 80-89 °C for the 960 h-sample. The deviation is
attributed to the effect of exposure of the material to UV radiation,
since no changes were observed in the DSC curve of the virgin
sample. In the second heating, the samples exhibited a unique curve
behavior due to the homogenization effect of the material after the
rst heating. Figure5b shows that crystallisation is similar among
the samples in function of the homogenization after melting. The
homogenization caused by the material’s melting displayed a new
polymeric conguration, since the crystallisation points are coincident
and the second evaluation of the melting point is also coincident.
The essential DSC evaluation was the rst heating analysis, which
revealed a deviation from the samples’ baseline.
Correlation between properties
The sample’s tensile properties increase after 8760 h of
UV exposure in comparison to the sample values after 4380 h
exposure can be attributed to the polymer’s crystallinity changes due
to the UV radiation degradation mechanism. A UV radiation aging
inuence is observed in the MFI test, since the value decreased for
the sample after 8760 h of UV exposure compared to the sample
value after 4380 h of exposure, correlating with the tensile test
results. Moreover, the high loss in the SCR value after 8760 h of
UV laboratory exposure corroborates the DSC curve deviation
before the melting point, which increased after the three exposure
times evaluated. Despite the maintenance of the ductility of the
geomembrane after the UVexposure, the SCR test results revealed a
brittle failure behavior. After 8760 h of UV exposure, the antioxidants’
depletion (Std. OIT) was almost complete, showing the level of
Table 4. SCR test results after UV uorescent exposure and retained SCR
test values compared with the virgin sample values
Exposure time / h SCR mean value ± SD / h SCR / %
0 629.84 ± 67.55 100.0
960 587.32 ± 24.13 93.25
4380 501.62 ± 29.72 79.64
8760 299.29 ± 18.39 47.52
SD: standard deviation. SCR: stress crack resistance.
Figure 4. Retained Std. OIT and HP OIT tests results compared with virgin
sample test result after UV uorescent exposure
Figure 3. Retained SCR test results compared with virgin sample test result
after UV uorescent exposure
Table 5. Std. OIT and HP OIT tests results after UV uorescent exposure and retained OIT test values compared with the virgin sample values
Exposure time / h Std. OIT
mean value ± SD / min Std. OIT / % HP OIT
mean value ± SD / min HP OIT / %
0 199.78 ± 4.03 100.0 287.25 ± 1.06 100.0
960 166.85 ± 3.94 83.52 268.52 ± 3.04 93.48
4380 143.87 ± 1.98 72.01 201.81 ± 2.53 70.26
8760 21.59 ± 1.01 10.81 134.57 ± 3.67 46.85
SD: standard deviation. Std. OIT standard oxidative-induction time: HP OIT: high-pressure oxidative-induction time.

Performance of an environmental protection liner after laboratory UV exposure 5Vol. 48, No. 2
degradation resulting from the exposure is directly associated with
the depletion of the antioxidant. Such a behavior contributes to the
susceptibility of thermal effects in the DSC curves, attesting the
mechanism of oxidative degradation of the geomembrane occurs and
changes the structure of the polymer.
CONCLUSIONS
This study analyzed a 1.5 mm-thick HDPE geomembrane exposed
to UV radiation for 8760 h in the laboratory.
Although the geomembrane maintained the ductile behavior after
exposure, it showed a 52.48% SCR nal decrease in comparison to
the virgin SCR result, demonstrating its susceptibility for the stress
cracking phenomenon.
A considerable antioxidant depletion was observed after 8760h
exposure according to the Std. OIT results, reaching a 89.19%
decrease in comparison to the virgin Std. OIT result. Regarding
thermal behavior, the DSC curves showed a deviation before the
melting point, which is attributed to the effect of exposure of the
material to UV radiation, since the DSC curve of the virgin sample
showed no changes.
Finally, such an antioxidant depletion behavior contributed to the
susceptibility of thermal effects in the DSC curves and the losses in
the SCR values, attesting the geomembrane’s oxidative degradation
mechanism occurs and changes the polymer’s structure.
REFERENCES
1. Rollin, A. R.; Rigo, J. M.; Geomembranes-Identification and
Performance Testing, 1st ed.; Chapman and Hall: London, 1991.
2. Koerner, R. M.; Designing with Geosynthetics, 5th ed.; Prentice Hall:
Upper Saddle River, 2005.
3. Vertematti, J. C.; Manual Brasileiro de Geossintéticos, 2ª ed.; Blücher:
São Paulo, 2015.
4. Scheirs, J.; A Guide to Polymeric Geomembranes: A Practical Approach,
1st ed.; Wiley: London, 2009.
5. Palmeira, E. M.; Geossintéticos em Geotecnia e Meio Ambiente, 1a ed.;
Ocina de Textos: São Paulo, 2018.
6. Lavoie, F. L.; Bueno, B. S.; Lodi, P. C.; Polim.: Cienc. Tecnol. 2013, 23,
690. [Crossref]
7. Rowe, R. K.; Sangam, H. P.; Geotextiles and Geomembranes 2002, 20,
77. [Crossref]
8. Kay, D.; Blond, E.; Mlynarek, J.; 57th Canadian Geotechnical
Conference; Quebec, Canada, 2004.
9. Van Santvoort, G.; Geotextiles and Geomembranes in Civil Engineering,
1st ed.; A.A. Balkema: Rotterdam, 1994.
10. Sharma, H. D.; Lewis, S. P.; Waste Containment System, Waste
Stabilization and Landlls: Design and Evaluation, 1st ed.; Wiley: New
York, 1994.
11. Suits, L. D.; Hsuan, Y. G.; Geotextiles and Geomembranes 2003, 21,
111. [Crossref]
12. Tian, K.; Benson, C. H.; Tinjum, J. M.; Edil, T. B.; J. Geotech.
Geoenviron. Eng. 2017, 143, 04017011-1. [Crossref]
13. Kelen, T.; Polymer Degradation, 1st ed.; Van Nostrand Reinhold Co:
New York, 1983.
14. Grassie, N.; Scott, G.; Polymer Degradation and Stabilization, 1st ed.;
Cambridge University Press: New York, 1985.
15. Rowe, R. K.; Ewais, A. M. R.; Can. Geotech. J. 2015, 52, 326.
[Crossref]
16. Lodi, P. C.; Bueno, B. S.; Vilar, O. M.; Mater. Res. 2013, 16, 1331.
[Crossref]
17. Sahu, A. K.; Sudhakar, K.; Sarviya, R. M.; Case Studies in Thermal
Engineering 2019, 15, 100534. [Crossref]
18. Reis, R. K.; Barroso, M.; Lopes, M. G.; Geotecnia 2017, 141, 41.
[Crossref]
19. Lavoie, F. L.; Kobelnik, M.; Valentin, C. A.; Tirelli, E. F. S.; da Silva,
J. L.; Lopes, M. L.; Case Studies in Thermal Engineering 2021, 4,
100133. [Crossref]
20. Lavoie, F. L.; Kobelnik, M.; Valentin, C. A.; da Silva, J. L.; Lopes,
M.L.; Results Mater. 2020, 8, 100131. [Crossref]
21. Safari, E.; Rowe, R. K.; Markle, J.; XIV Pan-Am CGS Geotechnical
Conference; Toronto, Canada, 2011.
22. Mendes, L. C.; Runo, E. S.; de Paula, F. O. C.; Torres Junior, A. C.;
Polym. Degrad. Stab. 2003, 79, 371. [Crossref]
23. Hsuan, Y. G.; Koerner, R. M.; J. Geotech. Geoenviron. Eng. 1998, 124,
532. [Crossref]
24. Ewais, A. M. R.; Rowe, R. K.; Scheirs, J.; Geotextiles and
Geomembranes 2014, 42, 111. [Crossref]
25. ASTM D7238: Standard Test Method for Effect of Exposure of
Geomembrane Using Fluorescent UV Condensation Apparatus; ASTM
International: West Conshohocken, PA, 2020. [Crossref]
26. ASTM D1238: Standard Test Methods for Melt Flow Rates of
Thermoplastics by Extrusion Plastometer; ASTM International: West
Conshohocken, PA, 2020. [Crossref]
27. ASTM D6693: Standard Test Methods for Determining Tensile
Properties of Nonreinforced Polyethylene and Nonreinforced
Flexible Polypropylene Geomembranes; ASTM International: West
Conshohocken, PA, 2020. [Crossref]
28. ASTM D5397: Standard Test Method for Evaluation of Stress Crack
Resistance of Polyolefin Geomembranes Using Notched Constant
Tensile Load Test; ASTM International: West Conshohocken, PA, 2020.
[Crossref]
29. ASTM D3895: Standard Test Method for Oxidative-Induction Time of
Polyolens by Differential Scanning Calorimetry; ASTM International:
West Conshohocken, PA, 2020. [Crossref]
Figure 5. DSC curves: (a) melting point (heating) stage and (b) crystallisation
(cooling) stage. (1) Virgin sample; (2) 8760 h UV uorescent sample;
(3)4380hUV uorescent sample; and (4) 960 h UV uorescent sample

Lavoie et al.
6Quim. Nova
30. ASTM D5885: Standard Test Method for Oxidative Induction Time
of Polyolen Geosynthetics by High-Pressure Differential Scanning
Calorimetry; ASTM International: West Conshohocken, PA, 2020.
[Crossref]
31. GRI-GM13: Test Methods, Test Properties and Testing Frequency
for High-Density Polyethylene (HDPE) Smooth and Textured
Geomembranes; Geosynthetic Institute: Folsom, PA, 2021. [Link]
accessed in May 2024
32. ASTM D5199: Standard Test Methods for Measuring the Nominal
Thickness of Geosynthetics; ASTM International: West Conshohocken,
PA, 2019. [Crossref]
33. ASTM D792: Standard Test Methods for Density and Specic Gravity
(Relative Density) of Plastics by Displacement; ASTM International:
West Conshohocken, PA, 2020. [Crossref]
34. ASTM D4218: Standard Test Method for Determination of Carbon Black
Content in Polyethylene Compounds by the Mufe-Furnace Technique;
ASTM International: West Conshohocken, PA, 2020. [Crossref]
35. ASTM D5596: Standard Test Method for Microscopic Evaluation of
the Dispersion of Carbon Black in Polyolen Geosynthetics; ASTM
International: West Conshohocken, PA, 2021. [Crossref]
36. ASTM D1004: Standard Test Methods for Tear Resistance (Graves Tear)
of Plastic Film and Sheeting; ASTM International: West Conshohocken,
PA, 2021. [Crossref]
37. ASTM D4833: Standard Test Method for Index Puncture Resistance
of Geomembranes and Related Products; ASTM International: West
Conshohocken, PA, 2020. [Crossref]
38. Gulec, S. B.; Edil, T. B.; Benson, C. H.; Geosynth. Int. 2004, 11, 60.
[Crossref]
39. Koerner, R. M.; Hsuan, Y. G.; Koerner, G. R.; 1st Pan American
Conference on Geosynthetics; Cancun, Mexico, 2008.
40. Lavoie, F. L.; Valentin, C. A.; Kobelnik, M.; da Silva, J. L.; Lopes,
M.L.; Tirelli, E. F. S.; Membranes 2021, 11, 390. [Crossref]
41. Rowe, R. K.; Morsy, M. S.; Ewais, A. M. R.; Waste Manage. 2019, 100,
18. [Crossref]
42. Lavoie, F. L.; Kobelnik, M.; Valentin, C. A.; Tirelli, E. F. S.; da Silva,
J.L.; Lopes, M. L.; Construction Materials 2021, 1, 122. [Crossref]
43. Abdelaal, F. B.; Rowe, R. K.; Geotextiles and Geomembranes 2014, 42,
284. [Crossref]
44. Lavoie, F. L.; Kobelnik, M.; Valentin, C. A.; Tirelli, E. F. S.; Lopes,
M.L.; da Silva, J. L.; Case Studies in Construction Materials 2022, 16,
e00809. [Crossref]
45. Lavoie, F. L.; Kobelnik, M.; Valentin, C. A.; Lopes, M. L.; Palmeira,
E.M.; da Silva, J. L.; Case Studies in Construction Materials 2023, 18,
e02212. [Crossref]