Figure 8. Thermo-mechanical process used for EPS recycling.
Mechanical properties
The tensile strength, tensile strain and Young‘s modulus of the composites as a function of wood flour and coupling agent are presented in Table 2. As can be seen, the tensile strength of the composites without SMA decreased with increasing of wood flour content.
This is due to the weak interfacial adhesion and low compatibility between wood flour and polymer matrix [49, 51]. In general, the introduction of wood flour reduced the tensile strength when compared to the unfilled EPS-r without the presence of the coupling agent. The expected incompatibility between the two components gave a poor transferring stress from the EPS-r matrix to the wood flour. Consequently, the composite failure at lower tensile strength. The introduction of 2 wt% of SMA2000 improved the tensile strength of the composites, as can be seen in Table 2. The tensile strength of the composites containing coupling agent increased when compared with the composites without SMA 2000. The introduction of the coupling agent improved the stress transfer efficiency by promoting chemical bonds between the hydrophilic filler and the hydrophobic matrix [51-52]. Also, the tensile strength of compatibilised composites increases.
On the other hand, the tensile modulus increased almost linearly by wood flour incorporation. This behavior is due to the reinforcing capacity of the wood flour [53]. The tensile modulus obtained was approximately 2 times higher in the composites with 40 wt%
wood flour than in the EPS-r polymer matrix. However, composites with coupling agent presented higher tensile modulus values than composites without SMA, due to the improved interfacial adhesion. The tensile strain was almost the same for composites with and without coupling agent.
The flexural strength values of the composites with and without coupling agent are shown in Table 3. The flexural strength exhibits a similar behaviour to that of the tensile strength. The addition of 2 wt% of SMA to the polymer matrix significantly improved the flexural strength in relation to the composites without coupling agent. The flexural strength reached a maximum value with 40 wt% of wood flour and 2 wt% of SMA. The composite presented a flexural strength 22% higher than the polymer matrix. Due to the similar mechanism, as explained earlier, the flexural strength of the composites with SMA as a coupling agent increased when compared to that of non-treated composites.
Table 2. Tensile properties of the EPS-r composites with and without coupling agent
Sample Tensile strength (MPa)
Tensile strain (%)
Young Modulus (MPa)
EPS-r 37.23 ± 0.57 1.17 ± 0.02 3494 ± 64
EPS-r/10wt%WF 31.47 ± 1.54 0.74 ± 0.08 3870 ± 66
EPS-r/20wt%WF 35.21 ± 0.90 0.86 ± 0.04 4208 ± 34
EPS-r/30wt%WF 35.32 ± 1.14 0.81 ± 0.01 4525 ± 103
EPS-r/40wt%WF 35.39 ± 1.53 0.64 ± 0.06 5615 ± 116
EPS-r/10wt%WF/2wt%SMA 35.55 ± 1.38 0.82 ± 0.02 3877 ± 59 EPS-r/20wt%WF/2wt%SMA 36.43 ± 0.60 0.86 ± 0.04 4426 ± 126 EPS-r/30wt%WF/2wt%SMA 34.98 ± 0.97 0.76 ± 0.03 4985 ± 104 EPS-r/40wt%WF/2wt%SMA 37.23 ± 1.18 0.71 ± 0.05 5810 ± 72
Table 3. Flexural properties of the EPS-r composites with and without coupling agent
Sample Flexural strength (MPa)
Flexural strain (%)
Flexural Modulus (MPa)
EPS-r 46.10 ± 1.53 1.56 ± 0.06 3315 ± 189
EPS-r/10wt%WF 52.35 ± 0.77 1.51 ± 0.02 3621 ± 62
EPS-r/20wt%WF 49.09 ± 1.68 1.22 ± 0.04 4072 ± 22
EPS-r/30wt%WF 44.70 ± 1.17 0.97 ± 0.02 4844 ± 99
EPS-r/40wt%WF 46.51 ± 1.75 0.89 ± 0.04 5726 ± 86
EPS-r/10wt%WF/2wt%SMA 53.07 ± 1.09 1.54 ± 0.03 3655 ± 19
EPS-r/20wt%WF/2wt%SMA 52.33 ± 2.34 1.30 ± 0.02 4167 ± 40
EPS-r/30wt%WF/2wt%SMA 53.26 ± 1.58 1.16 ± 0.06 4886 ± 45
EPS-r/40wt%WF/2wt%SMA 56.04 ± 1.98 1.08 ± 0.04 5745 ± 94
There were no significant differences between the flexural modulus values for the composites with and without coupling agent, as presented in Table 3. However, the treated composites seem to have a slightly higher flexural modulus than the composites without SMA. In general, the flexural strain for composites with and without coupling agent presented a similar behaviour.
Impact strength
The Izod impact strength of the composites decreased by wood flour incorporation, as can be seen in Table 4. The poor interfacial bonding between the filler and the polymer matrix causes micro-cracks that are easy-to- propagate in the composite without coupling agent [52]. These micro-cracks decrease the impact strength of the composites. The addition of wood flour leads to the creation of a weak interface between the filler and the EPS-r matrix, which creates a stress concentration and crack initiation point causing a significantly reduction of the impact strength. The filler also seems to reduce the polymer chain mobility, thereby reducing the ability of the composite to absorb energy during fracture propagation [54].
Composites with coupling agent exhibited better impact strength than the composites without treatment. With the addition of the coupling agent, the interfacial bonding between the wood flour and EPS-r matrix was considerably improved. The coupling agent promotes the interfacial adhesion between filler and matrix and also improved the dispersion of the wood flour, leading to a more uniform distribution of the applied stress. Therefore, more energy for debonding and fiber pull-out is required [54-55] increasing the impact strength of these composites.
Density and void content
Mechanical properties of polymer composites are well known to be strongly affected by internal defects such as voids [56]. Consequently, the density and void content usually serve as good indicators for composite performance [56-57]. A linear relationship can be observed between the density and the composite wood flour content, as presented in Table 5. The composites without coupling agent showed slightly lower density values than composites containing SMA. In addition, the treated composites had a density only 11% higher than the polymer matrix. However the mechanical properties increased in comparison to EPS-r, which
makes these composites attractive for automotive applications that requires the combination of strong materials with low density. The incorporation of 40 wt% wood flour did not increase significantly the density of composites, which makes the development of the material particularly attractive to industry. Especially for application in automotives since this requires composites with good mechanical properties, but with low density and void content values.
Table 4. Impact strength of the EPS-r composites with and without coupling agent
Sample Impact strength (J/m)
EPS-r 123.77 ± 6.96
EPS-r/10wt%WF 96.87 ± 4.82
EPS-r/20wt%WF 92.17 ± 3.89
EPS-r/30wt%WF 78.62 ± 4.00
EPS-r/40wt%WF 71.47 ± 5.85
EPS-r/10wt%WF/2wt%SMA 107.53 ± 4.71 EPS-r/20wt%WF/2wt%SMA 100.35 ± 3.24
EPS-r/30wt%WF/2wt%SMA 96.58 ± 1.82
EPS-r/40wt%WF/2wt%SMA 81.33 ± 1.47
Table 5. Density and void content of the EPS-r composites with and without coupling agent
Sample Density
(g/cm3)
Void content (%)
EPS-r 1.072 ± 0.001 ---
EPS-r/10wt%WF 1.091 ± 0.001 1.653 ± 0.030 EPS-r/20wt%WF 1.114 ± 0.002 2.239 ± 0.184 EPS-r/30wt%WF 1.139 ± 0.001 2.973 ± 0.039 EPS-r/40wt%WF 1.180 ± 0.002 2.224 ± 0.159 EPS-r/10wt%WF/2wt%SMA 1.092 ± 0.001 1.228 ± 0.064 EPS-r/20wt%WF/2wt%SMA 1.122 ± 0.001 1.730 ± 0.103 EPS-r/30wt%WF/2wt%SMA 1.150 ± 0.002 2.214 ± 0.181 EPS-r/40wt%WF/2wt%SMA 1.188 ± 0.001 1.819 ± 0.054
Figure 9. SEM images for composite fracture surfaces without (a) and with (b) coupling agent.
The void content values for the two types of composites were compared and were found to be lower for the treated composites than for the non-treated composites. According to Padma Priya et al. [58], for composites with good mechanical properties the void content values should be less than 3%. Composites with coupling agent had void content values less than 2%, while the non-treated composite values were close to 3%. Thus, the treated composites showed lower void content values and better mechanical properties than the non-treated ones. The decreased in void content for non-treated composites may indicate the existence of a good bonding between the wood flour and EPS-r matrix in the composite.
Morphology characteristics
The SEM micrographs of the non-treated composites and those treated with 20 wt% of wood flour are shown in Figure 9(a) and (b), respectively. In Figure 9(a), examination of the cryo-fracture surface of the composite without coupling agent indicated the presence of voids which are the main responsible for fiber pull-out and larger gaps between the wood flour and the EPS-r matrix. This causes a weak interfacial adhesion at the interface [51, 55]. The SEM micrograph of the treated composite in Figure 9(b) shows strong bonding and a reduced evidence of fiber pull-out. This result demonstrates that SMA addition to the composites provides strong interfacial adhesion and good wetting. This is confirmed by the almost complete absence of voids in the polymer matrix and gaps between the fiber and the matrix [51, 54].
F
UTURET
RENDSThe trend toward EPS materials with better insulation and mechanical strength continues to be studied and developed. Novel EPS materials that aim to reduce the thermal conductivities for potential uses in special applications are under development. The global demand for EPS and its production is steadily increasing and according to the last surveys, it will grow at a CAGR of 8.2% from 2013 to 2018. The increase in EPS production necessitates the intensification of recycling efforts around the world. The technology to recycle polystyrene already exists and others will be invented. However, the high cost associated with transporting the waste EPS to recycling facilities generally is a huge obstacle [59]. The cost can be lowered considerably by reducing the volume of the waste, preferably at the point of origin [60]. Recycling polystyrene certainly shows great promise and more ways of utilizing recycled polystyrene will be discovered in the future [60]. Hopefully, the promise of sustainable EPS chain without cause environmental pollution will encourage companies, organizations and governments to work together to step up polystyrene recycling efforts [60].
C
ONCLUSIONEPS is a versatile material. The applications in packaging, construction and many others demonstrate the potential of this material. The increasing in demand, production and development of EPS also demonstrated that this material is far away to be replaced by others foam materials. On the other hand, recycling efforts need to be promoted by all members
involved in the EPS chain. Many processes can be used for recycling EPS and others will be created. However, the choice of an EPS recycling method needs to be based on technical, environmental and economic considerations. The thermal-recycling method presented in this work is an alternative to recycle EPS wastes and also contributes to the development of the EPS recycling. In addition, development composite materials with higher mechanical properties and low density can be used by industries as an interesting option to enclose environmental and economic benefits.
R
EFERENCES[1] Pohleman, HG; Echte, A. Fifty years of polystyrene. Polym. Sci. Overview, ACS Symposium Series, 175 (1981), 3685-3689.
[2] Rubin, I. Handbook of plastics materials and technology, John Wiley & Sons, New York, 1990.
[3] Dow Styrofoam invention. Available: http://building.dow.com/about/invention.htm.
[4] Snijders, EA. Water Expandable Polystyrene (WEPS) Computational and Experimental Analysis of Bubble Growth, Technische Universiteit Eindhoven, Eindhoven, 2003.
[5] EUMEPS, EPS foam insulation – Environmental product declaration, 2011.
[6] EPS Packaging Group, Expanded polystyrene (EPS) and the environment. Available:
http://www.eps.co.uk/pdfs/eps_and_the_environment.pdf.
[7] ACEPE, EPS components and transformation – Processes used. Available: http://www.
acepe.pt/index.php/eps/composicao-transformacao.
[8] EPS Industry Alliance, Expanded Polystyrene (EPS) Geofoam Applications &
Technical Data, EPS Industry Alliance, Crofton.
[9] Australian Urethane & Styrene, EPS technical data, New South Wales, 2011.
[10] Insulspan, Structure Insulation Panel System. Available: http://www.insulspan.com/.
[11] Winterling, H; Sonntag, N. Kunststoffe, 10 (2011), 18-21.
[12] Markets and Markets, Expanded polystyrene (EPS) market, by applications (Building &
Construction, Packaging & Others), & geography (North America, West Europe, Asia-Pacific & Rest of the World) – Global Trends & Forecast to 2018, Dallas, 2013.
[13] Plastemart, Rise in global demand for polystyrene and expandable polystyrene is led by demand from Asia Pacific, 2013. Available: http://www.plastemart.com/Plastic- Technical-Article.asp?LiteratureID=2032&Paper=rise-global-demand-polystyrene-expandable%20 polystyrene-EPS-led-by-asia-pacific.
[14] Merchant Research & Consulting, Ltd, Expandable Polystyrene (EPS): 2014 World Market Outlook and Forecast up to 2018, 2014. Available: http://mcgroup.co.uk/
researches/expandable-polystyrene-eps.
[15] EPS Industry Alliance, 2012 EPS recycling rate report, EPS Industry Alliance, Crofton, 2012.
[16] Japan Expanded Polystyrene Association (JPESA), EPS recycling is steadily increasing, JEPSA, Japan, 2010.
[17] Korean Foam-Styrene Recycling Association (KFRA), Waste EPS recycling status, KFRA, Seoul, 2012.
[18] Metropolitan Waste Management Group (MWMG), Polystyrene Recycling, MWMG, Melboune, 2014.
[19] Plastivida, Repensar project, Plastivida, São Paulo, 2010.
[20] Al-Salem, SM; Lettieri, P; Baeyens, J. Waste Manage, 29 (2009), 2625-2643.
[21] Shin, C. J. Colloid Interface Sci., 302 (2006), 267-271.
[22] Achilias, DS; Kanellopoulou, I; Megalokonomos, P; Antonakou, E; Lappas, AA.
Macromol. Mater. Eng., 292 (2007), 923-934.
[23] Garforth, A; Ali, S; Hernandez-Martinez, J; Akah, A. Curr. Opin. Solid State Mater.
Sci., 8 (2004), 419–425.
[24] Borsoi, C; Scienza, LC; Zattera, AJ. J. Appl. Polym. Sci., 128 (2013), 635-659.
[25] Poletto, M; Dettenborn, J; Zeni, M; Zattera, AJ. Waste Manage., 31 (2011), 779-784.
[26] García, MT; Gracia, I; Duque, G; de Lucas, A; Rodríguez, JF. Waste Manage., 29 (2009), 1814-1818.
[27] Shin, C; Chase, GG; Reneker, DH. Colloids Surf., A 262 (2005), 211-215.
[28] Noguchi, T; Miyashita, M; Inagaki, Y; Watanabe, H. Packag. Technol. Sci., 11 (1998), 19-27.
[29] Noguchi, T; Inagaki, Y; Miyashita, M; Watanabe, H. Packag. Technol. Sci., 11 (1998), 29-37.
[30] Noguchi, T; Tomita, H; Satake, K; Watanabe, H. Packag. Technol. Sci., 11 (1998), 39-44.
[31] Amianti, M; Botaro, VR. Cem. Concr. Compos., 30 (2008), 23-28.
[32] Shin, C. Packag. Technol. Sci., 18 (2005), 331-335.
[33] Kosmidis, V; Achilias, DS; Karayannidis, GP. Macromol. Mater. Eng., 286 (2001), 640-647.
[34] Kaminsky, W. Makromol. Chem., Macromol. Symp., 48/49 (1991), 381-393.
[35] Kaminsky, W; Predel, M; Sadiki, A. Polym. Degrad. Stab., 85 (2004), 1045-1050.
[36] Ward, PG; Goff, M; Donner, M; Kaminsky, W; O‘Connor, KE. Environ. Sci. Technol., 40 (2006), 2433-2437.
[37] Liu, Y; Qian, J; Wang, J. Fuel Proc. Technol., 63 (2000), 45-55.
[38] Bouster, C; Vermande, P; Veron, J. J. Anal. Appl. Pyrolysis, 15 (1989), 249-259.
[39] Williams, PT; Williams, EA. Energy and Fuels, 13 (1999), 188-196.
[40] Williams, PT; Williams, EA. J. Inst. Energy, 71 (1998), 81-93.
[41] Miskolczi, N; Bartha, L; Deák, Gy. Polym. Degrad. Stab., 91 (2006), 517-526.
[42] Karaduman, A. Energy Sources, 24 (2002), 667-674.
[43] Kiran, N; Ekinci, E; Snape, CE. Resour. Conserv. Recycling, 29 (2000), 273-283.
[44] Audisio, G; Bertini, F; Beltrame, PL; Carniti, P. Polym. Degrad. Stab., 29 (1990), 191-200.
[45] Zhang, Z; Hirose, T; Nishio, S; Morioka, Y; Azuma, N; Ueno, A; Okhita, H; Okada, M.
Ind. Eng. Chem. Res., 34 (1995), 4514-4519.
[46] Ukei, H; Hirose, T; Horikawa, S; Takai, Y; Taka, M; Azuma, N; Ueno, A. Catal.
Today, 62 (2000), 67-75.
[47] Panda, AK; Singh, RK; Mishra, DK. Renew. Sust. Energ. Rev., 14 (2010), 233-248.
[48] Kan, A; Demirboǧa, R. J. Mater. Process. Tech., 209 (2009), 2994-3000.
[49] Adhikary, KB; Pang, S; Staiger, MP. Composites Part B, 39 (2008), 807-815.
[50] Ashori, A; Nourbakhsh, A. Waste Manage., 29 (2009), 1291-1295.
[51] Kim, H-S; Lee, B-H; Choi, S-W; Kim, S; Kim, H-J. Composites Part A, 38 (2007), 1473-1482.
[52] Yang, H-S; Kim, H-J; Park, H-J; Lee, B-J; Hwang, T-S. Composite Structures, 77 (2007), 45-55.
[53] Bengtsson, M; Le Baillif, M; Oksman, K. Composites Part A, 38 (2007), 1922-1931.
[54] Nygård, P; Tanem, BS; Karlsen, T; Brachet, P; Leinsvang, B. Compos. Sci. Technol., 68 (2008), 3418-3424.
[55] Ashori, A; Nourbakhsh, A. Waste Manage., 30 (2010), 680-684.
[56] Takagi, H; Asano, A. Composites Part A, 39 (2008), 685-689.
[57] Borja, Y; Rieb, G; Lederer, K. J. Appl. Polym. Sci., 101 (2006), 364-369.
[58] Padma Priya, S; Ramakrishna, HV; Rai, SK. J. Reinf. Plast. Compos., 25 (2006), 339-345.
[59] Salhofer, S; Schneider, F; Obersteiner, G. Waste Manage., 27 (2007), S47-S57.
[60] Rubio, MR. Trends in Recycling of EPS Foam, Environment, Recycling, Waste Management, 2013. Available: http://www.ecomena.org/recycling-eps-foam/.
Editor: Cole Lynwood © 2014 Nova Science Publishers, Inc.
Chapter 4