Advances and Applications in Mathematical Sciences
Volume 20, Issue 10, August 2021, Pages 2151-2162
© 2021 Mili Publications
2010 Mathematics Subject Classification: 82D60, 74E99
Keywords: EPS, lightweight, properties, compression, construction.
Received February 4, 2021; Accepted April 7, 2021
PROPERTIES OF EXPANDED POLYSTYRENE (EPS)
AND ITS ENVIRONMENTAL EFFECTS
ANKESH, JAIKANT and SANJEEV GOYAL
Department of Mechanical Engineering
J. C. Bose University of Science and Tech.
YMCA, Faridabad India
E-mail: [email protected]
ersanjeevg[email protected]
Abstract
Within the present times, where technology is pacing up dynamically altogether, the
necessity of suitable materials for the development industry is rising day by day. More and more
buildings are being constructed to cater our needs of producing facilities. Materials required for
buildings nowadays must fulfil a wider range of purposes than simply being basic building
blocks or binding material. For buildings which require to be at higher temperatures, material
used should have higher fire resistance and a high thermal conductivity while the fabric used to
build huge suspension bridges must be lightweight. Many such requirements may arise
reckoning on the environment and application of construction. Choice of fabric depends highly
on these factors and its own properties. First found within the 1950s, EPS could be a fascinating
material which serves many if not all of those purposes. Key highlights of its properties are its
lightweight alongside the others like fire resistance, chemical activity, high load carrying
capacity, high resistance against impact, etc.
Properties of EPS vary with its density, compression and strain rate. On the account of
those properties, EPS can be suitably used as backfilling material in embankments, lightweight
concrete, Structural Insulated Panels, etc. This paper highlights the manufacturing of EPS, its
properties, scope of improvement within the properties that lay effect on major applications
within the scope of the topic. Various tests performed on the EPS specimen like water capillary
absorption, mercury intrusion porosimetry, open porosity and impedance spectroscopy will be
comprehended together with the test of mechanical strength.
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I. Introduction
An explosive rise in demand within the implementation of expanded
polystyrene (EPS) to the development industry has occurred lately. EPS is a
lightweight and sturdy foam with high crash strength and strong insulation
towards heat. Additionally, it has a robust load-bearing capability at a low
weight, air tightness for regulated conditions, enduring, absolute water and
vapour-proof capacity, easy to service, quick, and economical design.
Extruded Polystyrene has been utilized in many diverse fields like food
packaging applications for several years. EPS being pocket-friendly and
energy-efficient is used more often as an effective insulation material in
building applications, as cushion travel packaging material for shock-
sensitive products, etc.
Expanded Polystyrene is an extended white spun plastic material
developed through a polymerization process from solid polystyrene beads [3].
EPS foam consistency is influenced by the dimension’s distribution of the
beads. EPS is impregnated with blowing materials including hexane (C6H12)
and pentane (C5H10) following polymerization. Expandable polystyrene is
processed to EPS by means of three steps: (1) pre-expansion of EPS beads, (2)
conditioning and maturing of beads, and (3) molding and expansion.
Polystyrene granulate is pre-foamed over 90°C to form a sufficiently
homogeneous cellular framework with tiny closed cells containing air within.
This temperature causes the foaming agent to evaporate, thus inflating the
bottom thermoplastic material to 20-50 times its original size. The inner gas
of the beads’ experiences volume expansion during this process, which creates
an air-penetrable cellular structure. During the materia’s intermediate
maturing, this process is meted out in aerated silos. The ageing period is set
counting on the beads, air temperature, scale, and density. Enhanced
mechanical elasticity and increased expansion capability are achieved by the
beads. Steady pre-expanded beads are then moulded and re-exposed to steam
to attach the beads together as an important part of the expansion step. The
stabilized beads were formed into broad blocks (Block Molding Process) or
customized structures (Shape Molding Process) during their final step.
Moreover, polystyrene foam is also produced in solid-state. Carbonic acid gas
or nitrogen is employed as an expanding agent in extrusion, during the
suspension polymerization.
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EPS is a rigid and tough, recyclable, closed-cell plastic substance that has
been used in a number of applications including impact reduction wrapping,
protective helmet, structural crashability, road filling building products,
insulated concrete (ICF) frameworks as well as lightweight EPS foamed
concrete. EPS foam is waterproof, lightweight and provides outstanding
thermal isolation. These properties render it suitable for packaging purposes
[8, 11].
Figure 1. Three significant EPS forms.
II. Properties of EPS
A. Insulating Properties of EPS against heat and its Fire Conduct
Expanded polystyrene (EPS) is found to be the most commonly used
polymer core. This is because it is lightweight, resistant to moisture and also
it has a long life. Pertaining to its low thermal conductivity, EPS acts as an
excellent insulator for heat flow. Though, it works poorly in resisting fire due
to its lower melting point temperature [1]. Studies have concluded that
softening of EPS starts when exposed to temperatures ranging from 100
o
C to
120
o
C. In the process of flashovers, EPS melted about 160°C and then
vaporized, producing poisonous gases at a temperature of 275°C. EPS is an
inert, low density hydrocarbon-derived thermoplastic which contains several
spherical beads with 2 percent polystyrene and 98 percent air. EPS is a
porous structure which enables vast air storage to accelerate fire spread
throughout the combustion processes. Fire spread characteristics of both
polystyrene foam and organic products are comparable as both are readily
ANKESH, JAIKANT and SANJEEV GOYAL
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flammable [13]. Neat EPS foam is characterized as a highly flammable
material due to its very low Limiting Oxygen Index (LOI) which is only 17%.
(1) Methods to Improve Fire Retardant Behaviour of EPS:
One approach to improve the fire resistance behaviour of EPS may be to
apply a small amount (< 1%) of fire-resistant material to the EPS insulation
material. The installation of mineral wool on EPS walls as a barrier to inhibit
horizontal fire formation.
Alternate solution is the introduction of flame-retardant additives such
as ammonium-polyphosphate (APP), [9] nano zirconia, diammonium
phosphate (DAP) and phosphorus-based acid additives into EPS. The fire
resistance mechanism emerged from the synergy between phosphorus, silicon
and nitrogen resulting in the creation of a defensive layer [1].
Pre-expanded polystyrene particles have historical influences, such as
APP, [9] melamine (MEL), and pentaerythritol (PER), been clearly mixed
with important intumescent flame retardants (IFR), to create the flame-
retardant EPS foam. However, in addition to IFR, novel additives such as
smoking silica and melamine enhanced urea formaldehyde resin have been
added to further improve the flame retardance of foam. The adhesion
between the flame retardant and the EPS surface can be a key issue to
consider in this process. A simple method has therefore been developed to
create an additional flame-retardant architecture consisting of APP, PER and
TGE in EPS foam layer.
In recent approach, flame retardants of non-halogen type are used for
microencapsulation, which has been proved as a good shielding material from
fire due to the variance of flame retardants and their easy to process property
[16]. This easy development method from the surface to higher flame
retardance produced an important and satisfying attempt to create a flame-
retardant EPS without interaction with thermal conductivity and increased
fire protection in structures and buildings, thereby reducing the potential
secondary fire-induced catastrophe.
A study presented a sample in which thermosetting phenolic resin is used
along with hydrated aluminium hydroxide shows better fire tolerance in LOI
tests in comparison to other unprocessed samples which shows that the fire
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activity of fire retarded EPS is substantially different from that of non-fire
retarded EPS. Fire-retarded EPS shrinks out of the heat supply when
subjected to heat. It won’t catch fire from small ignition sources like reefers,
electric short-circuits or welding sparks [13].
B. Mechanical Properties of EPS
(1) Density Variations: Density variations have great impacts on
mechanical properties of EPS. For instance, yield strength and compressive
elastic modulus are directly proportional to the density of EPS. Linear
relationship is seen between initial Young’s modulus and EPS density in the
elastic range. Energy absorption in low density EPS is done via distributed
cooperation and via failure of cells in high density EPS with high localized
forces at point of impact.
(2) Thickness: Thickness of EPS specimen also affects the shear modulus
of elasticity and shear strength.
(3) Loading: During the compressive loading of EPS foam, air entrapped
within the cells is also compressed and causes viscous forces which increase
with rise in loading rate, and in turn lead to rise in strain rate sensitivity.
(4) Experiments: Research was done by Ferrándiz-Mas and García-
Alcocel [6] on EPS mortar’s durability. Microstructure of cement mortar was
taken into minute consideration and analysis was carried out to test type of
EPS and its concentration effects on the strength of mortar.
Some of the methods followed were water capillary absorption, mercury
intrusion porosimetry, open porosity and impedance spectroscopy. Results
obtained are as follows: It is found that the capillary absorption coefficient is
reduced by using EPS. While explaining the microstructure pattern of EPS in
mortar, scarcity was observed due to its sponge-like and polymeric behavior.
As the insulating properties of EPS rises, compressive strength of EPS also
rises as illustrated in Heat cycles and freeze-thaw cycles. By adding air-
entraining agents, superplasticizer additives and water retainer the
workability of mortar is improved. The maximum uniaxial compressive stress
which the material can withstand before fracture is called Compressive
strength. Compressive strength of EPS product is tested at compression of
10% and this value is then assigned to EPS product (table I). [7]
ANKESH, JAIKANT and SANJEEV GOYAL
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Table I. Mechanical Properties by EPS Type [7].
Mechanical Strength (kPA)
Compressive strength
10% Compression
10% Nominal Strain
Flexural Strength
EPS 70
70
20
115
EPS 100
100
45
150
EPS 150
150
70
200
EPS 200
200
90
250
EPS 250
250
100
350
Taguchi’s approach was used for studying mixed proportion parameters
of EPS lightweight aggregate concrete by Yi Xu [14]. As a result of these tests
for density, stress-strain variations and compressive strength, it is found that
by changing the concentration of EPS in EPS lightweight concrete, its
compressive strength is significantly changed. These variations are much
more in comparison to the effect of varying water-cement ratio. Effects of
changes in cement-sand ratio are even more insignificant.
The properties like performance in traction, compression, and flexion,
wear resistance and hydrophobic nature can be enhanced by thermal
treatment. To understand the impact of thermal treatment on these
properties, both Non-treated EPS and (NTEPS) and treated EPS (TTEPS) are
compared. It is found that density of EPS increases ten times by thermal
treatment [5]. Strength characteristics of EPS increase with increase in
density, while cushioning properties of EPS foam are decided mainly by
geometry of molded part and by size of bead, processing conditions and
density by smaller extent. The flexural strength of EPS geofoam increases
with the increase in density [2].
C. Water and Moisture Absorption
The water absorption capacity of EPS is low, which further shows a
remarkable reduction as the density increases. The EPS cellular arrangement
is water-resistant, vapour-permeable and has zero capillary properties.
Although neither liquid water nor water vapour affects its mechanical
properties; however, owing to fine interstitial channels between shaped
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beads, there is still a higher chance of moisture absorption upon full
immersion of EPS.
A low temperature plasma treatment is used as a method to increase EPS
surface energy. As a result, the EPS specimen’s surface became highly
hydrophilic. In order to improve its high temperature tolerance and give it an
antibacterial character, SiO2 and TiO2 films may be deposited on the outer
surface of EPS beads [15]. In order to lower its adsorption degree to use it as
a potential sacrificial agent in chemical enhanced oil recovery, R. Diego et al.
[10] used another sort of EPS procedure where they degassed EPS in ethyl
acetate and sulfonated it. VEJELIS and VAITKUS have established that the
most reliable findings of water absorption by expanded polystyrene are
obtained by applying an increased pressure method.
Table II. Moisture Properties of Jablite EPS [7].
In addition, the shape of the sample, it’s height and its preparation
process have a major effect on the absorption of water. Table II indicates the
moisture properties of the EPS of various amounts. Because of the water-
resistant property of cell walls, the water will only enter into the tiny
channels between the fused beads.
D. Chemical Resistance Behaviour of EPS
EPS shows no chemical reaction with water, salt, or alkali solution. The
preferences of adhesives, labelling and coatings for EPS material are based
upon the insolubility of EPS in certain organic solvents. EPS’s chemical
tolerance is set by time, temperature and stress applied.
ANKESH, JAIKANT and SANJEEV GOYAL
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Table III. EPS Resistant Behavior.
Because of its thin cell walls and wide exposed surface, EPS is at risk of
solvent attack that contributes to softening and cracking of itself. In general,
by exposing moulded polystyrene thereto at 120-140°F, a material is checked
for its compliance with EPS. Its physical properties remain unchanged,
considering the ultraviolet radiation leading to superficial yellowing and
friability of moulded polystyrene. Table IV outlines the chemical tolerance of
EPS with relevance to common reagents and solvents.
E. Production of Smoke
The clear colloidal solution within the gas as a combustion and pyrolysis
result is defined as smoke [4]. The smoke will be dangerous and poor in
oxygen content. Dense black smoke is produced in conjunction with the
burning mass when the EPS is burned. because of the low EPS density, the
quantity of smoke is reduced. Production of smoke may be suppressed by
restricting the power of fabric to ignite and reducing the flame spread and
warmth released. In its use as building materials, EPS isn't used exposed, but
protected by other materials (sandwiched), so the EPS are shielded from fire.
so as to scale back smoke output during fire incidents, the surface region of
EPS insulation must be covered by non-combustible material.
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III. Environmental Effects of Eps and Its Toxicity
By binding along huge amounts of styrene molecules, polystyrene is
produced. Polystyrene may be treated as a solid, film, or foam after the
polymerization process. Styrene monomer is a hydrocarbon with C8H8 as
molecular formula which gets oxidized fully when burnt to form carbonic acid
gas, CO2, and water within the presence of excess element, as seen in the
combining equation specified below:
C₈ H₈ + 10O₂ → 8CO₂ + 4H₂O
Various gases are accustomed to blow it up into foam. The raw materials
from which it is manufactured are hydrocarbons (ethylene and benzene)
extracted from petroleum and natural gas.
The level of oxygen accessible during the combustion had a direct control
on the extent of soot and CO, and CO had formed. The total combustion of
one g of polystyrene, in theory, involves more or less 2150cm3 of oxygen. As
this tremendous quantity of oxygen is often not usable throughout
combustion, polystyrene partly burns to create additional soot and CO, as
seen within the equation.
C₈H₈ + (10-0.75 x) O₂→ xC + xCO + (8-2x) CO₂ + 4H₂O
Styrene use raises the likelihood of cancer, since styrene is one among the
carcinogens of humans (National toxicology Program, 2016). In addition, staff
members in EPS foam producing facilities are in danger of acquiring diseases
like respiratory organ tumours and malignant neoplastic disease. Long-run
exposure to vinylbenzene from EPS foam processing typically induces
weakness, impairment of the central nervous system, and body defects (US
Congress Representatives, 2011).
In reality, the globe experiences plenty more besides the toxic effects on
humans. It takes 500 years for EPS foam goods to get decomposed in order
that they are recycled in an exceedingly proper manner. Furthermore, water
quality is affected because the Advances and Applications in Mathematical
Sciences, persisting styrene in landfills leads to the leaching of styrene which
further seeps into the groundwater and thus pollutes it. Hazardous gas could
also be generated by incinerating EPS foam at a temperature of up to 900°C.
This may impact the air quality of the people residing near the incineration
ANKESH, JAIKANT and SANJEEV GOYAL
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facilities, leading to detrimental health consequences and costs [12]. Gypsum,
brick, wood or steel are used because the EPS surface insulation materials
help to stay fires from spreading to the EPS. The influence of fire-retardant
content on EPS toxicity is marginal attributable to the need for just a small
addition (0.5-0.1%) of the material. Therefore, relative to natural products,
like timber, wool, or cork, EPS emits considerably fewer harmful fumes [13].
Analysis found that starch and cellular-derived composites EPS are more
likely to take over traditional EPS in frequent uses, considering its eco-
friendly features. EPS doesn’t damage the ozone layer to any extent further
since it doesn’t use CFCs or HCFCs within the manufacturing process. It
becomes difficult for fungi and bacteria to grow on the surface of EPS. EPS
holds a high calorific value. 1kg of EPS is similar to 1.3 litres of liquid fuel,
making it a perfect material for energy recovery.
IV. Conclusion
Expanded Polystyrene (EPS) is a rigid cellular plastic typically white and
manufactured from pre-expanded polystyrene beads. High impact resistance
and good thermal insulation make it an honest choice in numerous industrial
applications. Furthermore, it possesses a light-weight however robust
structure and is known for its exceptional qualities like it has a robust load-
bearing capability at a low weight, air tightness for regulated conditions,
enduring, absolute water and vapour-proof capacity, easy to service, quick,
and economical design, which make it more adaptable within the construction
industry. This publication aims to provide balanced information based on the
manufacturing of EPS, properties concerned with it, how they can be
enhanced and their effect on major applications within the scope of the
subject. Further, viability of EPS as an insulating material has been
discussed and ways to enhance its resistance against flames are discussed
which includes a flame suppressive material coated over the surface of EPS to
make it safer from fire damages and fulfill the fire safety norms regarding
the spread of flame and inflammable properties. Consequently, EPS is an
environment friendly polymer which can be recycled completely and
effectively. Further scope of research is marked in the field of resistance
against organic solvents, health concerns attached with styrene and making
EPS flame retardant in cost effective ways.
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References
[1] Abdul Rashid, Muhammad Khairi, Nor Hafizah Ramli Sulong and Ubagaram Johnson
Alengaram, Fire resistance performance of composite coating with geopolymer-based bio-
fillers for lightweight panel application, Journal of Applied Polymer Science 137(47)
(2020), 49558.
[2] Y. Z. Beju and J. N. Mandal, Expanded polystyrene (EPS) geofoam: Preliminary
characteristic evaluation, Procedia engineering 189 (2017), 239-246
[3] Chindaprasirt, Prinya, Salim Hiziroglu, Chattichai Waisurasingha and Pornnapa
Kasemsiri, Properties of wood flour/expanded polystyrene waste composites modified
with diammonium phosphate flame retardant, Polymer Composites 36(4) (2015), 604-
612.
[4] Drysdale and Dougal, An introduction to fire dynamics, John Wiley and Sons, 2011.
[5] Ellouze, Ameni, David Jesson and Ridha Ben Cheikh, The effect of thermal treatment on
the properties of expanded polystyrene, Polymer Engineering and Science (2020).
[6] Ferrándiz-Mas, Verónica and E. García-Alcocel, Durability of expanded polystyrene
mortars, Construction and building materials 46 (2013), 175-182.
[7] Jablite, Expanded Polystyrene (EPS) Technical Information; Jablite; Vencil Resil
Limited: Kent, 2011, https:// jablite.co.uk/wp-content/uploads/2016/01/Jablite-EPS.pdf 21
[8] Levytskyi, Volodymyr, Volodymyr Moravskyi, Andrii Masyuk, Rafał Kuzioła, Katarzyna
Grąz and Ulyana Khromyak, Modified Densified Waste of Expanded Polystyrene and Its
Blends With Polyamide 6, Polymer Engineering and Science (2020), 26.
[9] Liu, Tongwei, Guopu Shi, Guozhong Li and Zhi Wang, Lightweight foamed concrete with
foam agent addition, In IOP Conference Series: Materials Science and Engineering
490(3) (2019), 032033. IOP Publishing.
[10] M. Diego, F. M.-P. Andrés, E. C.-C. Luis and V. K. Vladimir, Chem. Eng. Trans. 57
(2017), 631.
[11] Markulak, Damir, Tihomir Dokšanović, Ivan Radić and Ivana Miličević, Structurally and
environmentally favorable masonry units for infilled frames, Engineering Structures 175
(2018), 753-764.
[12] I. A. Ogundiran and Y. M. D. Adedeji, Sustainable Construction: Comparative
Advantages of Expanded Polystyrene (EPS) Fascia in Housing Delivery in Nigeria, Civil
and Environmental Research, ISSN (2014), 2224-5790.
[13] Ramli Sulong, Nor Hafizah, Siti Aisyah Syaerah Mustapa and Muhammad Khairi Abdul
Rashid, Application of expanded polystyrene (EPS) in buildings and constructions: A
review, Journal of Applied Polymer Science 136(20) (2019), 47529.
[14] Xu, Yi, Linhua Jiang, Jinxia Xu and Yang Li, Mechanical properties of expanded
polystyrene lightweight aggregate concrete and brick, Construction and Building
Materials 27(1) (2012), 32-38.
ANKESH, JAIKANT and SANJEEV GOYAL
2162
[15] A. N. Yusilawati, M. Maizirwan, Iis Sopyan, M. S. Hamzah, K. H. Ng and Chiow San
Wong, Surface modification of polystyrene beads by UV/ozone treatment, In Advanced
Materials Research Trans Tech Publications Ltd 264 (2011), 1532-1537.
[16] Zhu, Zong-Min, Ying-Jun Xu, Wang Liao, Shimei Xu and Yu-Zhong Wang, Highly flame
retardant expanded polystyrene foams from phosphorus-nitrogen-silicon synergistic
adhesives, Industrial and Engineering Chemistry Research 56(16) (2017), 4649-4658.
