J of material science and engineering A-2012

Materials Science & Engineering A ] (]]]]) ]]]–]]] Contents lists available at SciVerse ScienceDirect Materials Science & Engineering A journal homepage: www.elsevier.com/locate/msea Mechanical behavior of recycled polyethylene/piassava fiber composites Amal Elzubair a,c,n, Joa~ o Carlos Miguez Suarez b,c,1 a b c ~ Bloco F, 21941-972 Rio de Janeiro, RJ, Brazil Universidade Federal de Rio de Janeiro, Departamento de Engenharia Metalúrgica e de Materiais, Ilha do Fundao, ~ de Engenharia Meca~ nica e de Materiais, Prac- a General Tibúrcio, 80, Urca, 22290-270, Rio de Janeiro, RJ, Brazil Instituto Militar de Engenharia, Sec- ao Prac- a General Tibúrcio, 80, Urca, 22290-270 Rio de Janeiro, RJ, Brazil a r t i c l e i n f o Keywords: Piassava composite Leopoldinia piassaba Recycled polyethylene Surface treatment Mechanical behavior abstract The use of natural fibers for reinforcement of thermoplastics (which are found in domestic waste) is desirable since it is based on abundant and renewable resources and can be ecologically correct. Leopoldinia piassaba Wallace (commonly known as piassava), a palm tree native of Amazon-Brazil, is cheap, easily found in Brazilian markets and the main component of home appliances and decorative goods. The subject of the present work is a study of mechanical properties of composites of recycled high density polyethylene (HDPE-r) reinforced with untreated, and treated (silane and NaOH) piassava fibers, in proportions varying from 0% to 20% and injection molded under fixed processing conditions. The influence of increasing amounts of piassava fibers and of surface treatment on the mechanical behavior of the composites was investigated by thermogravimetric analysis (TGA), mechanical testing (tensile and flexure) and scanning electron microscopy (SEM). The topography of the fractured surfaces of tested tensile specimens of unfilled and filled recycled HDPE was also observed by SEM and correlated with the mechanical behavior. As the fiber content increases, the composites show a gradual change in the mechanical properties and in the fracture mechanisms. Composites with 15% and 20% of piassava fibers were found to exhibit the best mechanical performance. & 2012 Elsevier B.V. All rights reserved. 1. Introduction The use of natural fibers as reinforcement for thermoplastics is attractive since it is based on abundant and renewable resources and is ecologically sound as it stimulates the recycling of thermoplastics found in domestic waste. This is more interesting since in Brazil there are abundant native palm species whose lignocellulosic fibers have good mechanical properties. One of these fibers is piassava (Fig. 1a), which has long, hard and tough fibers that grow out of the leaf base surrounding completely the trunk [1–3]. Piassava fibers are used in the production of brooms, brushes and ropes and the economy of several Brazilian communities is based on the extraction and processing of these fibers. A recent slowdown in the market of piassava fibers had serious effects on the income of native populations making it extremely desirable to develop new non-traditional uses for these fibers [4,5]. n Corresponding author at: Universidade Federal de Rio de Janeiro, Departamento de Engenharia Metalúrgica e de Materiais, Ilha do Funda~ o, Bloco F, 21941-972 Rio de Janeiro, RJ, Brazil. Tel.: 55 21 2562 8790; fax: 55 21 2280 7443x235. E-mail addresses: amal@metalmat.ufrj.br (A. Elzubair), jmiguez@ime.eb.br (J.C. Miguez Suarez). 1 Tel.: þ55 21 2546 7248; fax: þ 55 21 2546 7043. Since plant-derived cellulose fibers are in general polar and hydrophilic, while thermoplastics are largely non-polar and hydrophobic, then such a lack of compatibility leads to poor adhesion, which, in turn results in a composite material with unsatisfactory mechanical properties. The fibers–matrix adhesion can be improved by modifying the surface of the fibers to make them more compatible with the matrix, or by introducing a coupling agent that adheres well to both the fibers and matrix [6–8]. Adhesives in the fiber cell wall (such as lignin, pectin, and hemicelluloses) are responsible for binding cellulose microfibrils together, as well as for joining adjacent fibers together to form fiber bundles. These compounds must be removed to initiate fiber separation, and thus enable better fiber distribution within the composites [7]. NaOH plays the crucial role of removing lignin by means of alkaline cleavage of ether linkages in the lignin, which may be accompanied by condensation reactions. Pectin can be completely attacked and removed without any residue being left in the fiber after NaOH treatment, but the rate of lignin removal depends on the NaOH concentration. Some alkali treatments, especially those performed at high temperatures, have been shown to selectively degrade the cementing materials in natural fibers, whilst having little effect on the cellulose components [7,9,10]. On the other hand, silane is used as a coupling agent to improve the adhesion between the fiber and thermoplastic matrix. 0921-5093/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.msea.2012.06.051 Please cite this article as: A. Elzubair, J.C. Miguez SuarezMechanical behavior of recycled polyethylene/piassava fiber composites, Materials Science & Engineering A (2012), http://dx.doi.org/10.1016/j.msea.2012.06.051 2 A. Elzubair, J.C. Miguez Suarez / Materials Science & Engineering A ] (]]]]) ]]]–]]] standard) producing fiber fragments that showed a higher frequency of effective diameters in the sieve mesh range between 0.25 and 0.71 mm. Fragments in this range were used to make the composites. The recycled high density polyethylene was obtained from post-consumer lubricating oil bottles in solid waste supplied by LMG Indústria e Comércio de Plásticos (Duque de Caxias, Rio de Janeiro, Brazil). It has a melt flow index (MFI) of 0.3 g/10 min (at 190 1C and 2.16 kg load measured according to ASTM D1238); a density of 0.96 (ASTM D792) and a melting temperature of 132 1C (ASTM D1347). 2.1. Fiber surface treatments The fragmented fibers were submitted to two treatments to improve the compatibility and adhesion between them and the matrix as follows: (i) Silane treatment, where the fibers were impregnated directly with 3-methacryloxypropyltrimetoxy silane-MPTMS (D’Altomare, Sa~ o Paulo, SP) with 1/3 silane/fiber proportion. (ii) Alkali treatment where the fibers were soaked at room temperature in NaOH aqueous solution (5%) for 48 h followed by neutralization and drying at 100 1C for 24 hours in an oven equipped with circulating air 2.2. Compounding HDPE-r pellets were hand mixed with 5, 10, 15 and 20 wt% of untreated and treated piassava fibers and compounded in a Haake reometer connected to a twin-screw extruder operating at 60 rpm and with temperatures at 150, 160, 170 and 180 1C. The resultant composites were in the form of small pellets used later for the production of tensile and flexure test specimens in a Pic-Boy injection machine at 230 1C. 2.3. Fiber and composite characterization Fig. 1. Leopoldinia piassaba Wallace or Amazon piassaba: (a) a view of the palm and (b) the fiber after fragmentation. This work is part of a project that investigates the use of piassava as natural fiber reinforcement in composites with a recycled plastic matrix, developing a new low cost material for applications where a high performance is not required. 2. Experimental In the present work, we studied an injection molded composites of HDPE-r matrix reinforced with 5, 10, 15 and 20 wt% piassava fibers (untreated and treated). The ‘‘as received’’ piassava fibers with a density of approximately 1.13 g/cm3 and a length in the range from 0.60 to 2.18 m were taken from a bale of piassava (Sa~ o Gabriel da Cachoeira, Amazonas, Brazil) whose structure, morphology and mechanical properties were reported elsewhere [11]. The fibers were fragmented in a Brabender equipment with rotating knives, washed with cold water to remove the dust and dried in an air-circulating oven at 80 1C for 2 h. The fragmented fibers (Fig. 1b) were size classified in a laboratory sieve (DIN 4188 The effects of fiber surface treatments and increasing fiber content in the composites behavior were investigated by thermogravimetric analysis (TGA), mechanical testing (tensile and flexure) and scanning electron microscopy. TGA was carried out in a Shimadzu model TGA-50 thermobalance. The samples, weighing approximately 20 mg, were heated from 25 to 700 1C with a heating rate of 20 1C/min in nitrogen atmosphere. The degradation temperature was determined. The mechanical tests were carried out at room temperature and 50% humidity in a universal testing machine of Instron Corporation; series IX automated material testing system 1.19. Tensile tests were performed with average sample dimensions: width¼13.5 mm, depth¼2.5 mm and gage length 115 mm using pneumatic grips and extensometer. The load cell is 1 kN and cross-head speed of 10 mm/min according to ASTM D638. Flexural (3-point bending) test with average sample dimensions: width¼12 mm, depth ¼5 mm and span¼100 mm, and crosshead speed of 3.3 mm/min according to D790 standards. Seven to ten specimens were tested for each composite condition, and the mean value and standard deviation for each property were calculated with software provided with the testing machine. Scanning electron microscopy (SEM) was used to analyze the morphologies of longitudinal and transversal sections of samples of untreated and treated fibers that were cryogenically fractured after being immersed for at least 30 min in liquid nitrogen. The failure mechanisms of composites specimens were studied by examining the specimens fractured in the tensile tests. The Please cite this article as: A. Elzubair, J.C. Miguez SuarezMechanical behavior of recycled polyethylene/piassava fiber composites, Materials Science & Engineering A (2012), http://dx.doi.org/10.1016/j.msea.2012.06.051 A. Elzubair, J.C. Miguez Suarez / Materials Science & Engineering A ] (]]]]) ]]]–]]] microscopic exams were realized in a model JSM 5800LV JEOL scanning electron microscope by direct observation of the topography of the samples fracture surfaces which were sputtercoated with gold in a vacuum chamber before examination. 3. Results and discussion 3.1. Thermogravimetric analysis Fig. 2 demonstrates the DTG curves (first derivatives of the TGA curves) of HDPE-r, untreated piassava fiber, and composites with untreated and treated fibers. A series of thermal events are shown. Such thermal transitions may be associated to the degradation process expected in fibers, mainly pyrolysis of their 3 main constituents: cellulose, lignin and hemicellulose, a process during which gases (such as CO, CO2), vapors are formed as well as a solid residue of charcoal [12] As evident in Fig. 2, the thermal degradation of untreated piassava fiber starts with a slight weight loss at 70 1C which proceeds till around 200 1C, most probably, this is related to the evaporation of water and any substances having low boiling point. Additionally, several competing pyrolytic reactions take place; one started at 200 1C and having a maximum at 309 1C may be attributed to pyrolysis of hemicellulose, pectin, or lignin (which continues its decomposition till about 500 1C). The other reaction starts at 372 1C and can be assigned to degradation of cellulose. Such degradation is supposed to be faster than that of lignin, but due to its partial crystallinity, cellulose can be thermally more stable than the other amorphous constituents. Fig. 2. DTG curves of HDPE-r, untreated piassava fiber, and composites: (a) with fiber treated with silane while and (b) with fiber treated with NaOH (alkali treatment). Please cite this article as: A. Elzubair, J.C. Miguez SuarezMechanical behavior of recycled polyethylene/piassava fiber composites, Materials Science & Engineering A (2012), http://dx.doi.org/10.1016/j.msea.2012.06.051 4 A. Elzubair, J.C. Miguez Suarez / Materials Science & Engineering A ] (]]]]) ]]]–]]] The first peak is observed to almost disappear in the measured curves of all composites that have been reinforced with treated fibers suggesting that this treatment has managed to wash out all the cementing materials from the fiber surfaces. Furthermore, we observed that for composites consisting of 15% and 20% fibers that were treated with silane, the cellulose degradation peak was broad and shifted to 398 and 424 1C respectively. By contrast, for those fibers that were treated with alkali, the peak was found to be shifted to 381 and 400 1C respectively. This comparison shows that the latter treatment leads to a higher thermal stability than for the case of untreated fibers. Finally, the degradation event at 493 and 495 1C is attributed to the degradation process of HDPE-r. These observations show that the thermal degradation of piassava fibers, as compared with most thermoplastics, occurs at relatively high temperatures; this confirms the good thermal resistance of this kind of fiber [13–15]. 3.2. Mechanical properties The mechanical tests parameters of the composites were summarized in Tables 1 and 2, containing the mean values and standard deviations of the measurements. On comparing the tensile and flexure (bending) results; one notice that the tensile strain decreases as the fiber content is increased, and that the flexure strain as well as the displacement are almost constant. The toughness calculated from tensile measurement decreases with increasing fiber content, and, furthermore, it shows higher values as compared to those of the flexure test. The latter features are suggestive of the type of applications wherein these composites may be used. Fig. 3 shows the tensile and flexure strength of the composites (Fig. 3a) and their tensile modulus (Fig. 3b) as a function of the content of untreated and treated piassava fibers. Our findings suggest that t the addition of piassava fiber to the polymeric matrix increased the tensile strength, as compared to the unfilled HDPE-r. The highest value of the tensile strength was achieved in the composite containing 20% of piassava fibers treated with sodium hydroxide and the lowest with fibers treated with silane. t the addition of piassava fiber to the polymeric matrix increased the tensile strength, as compared to the unfilled HDPE-r. The highest value of the tensile strength was achieved in the composite containing 20% of piassava fibers treated with sodium hydroxide and the lowest with fibers treated with silane. Furthermore, for the 15% composites, no significant differences between the treated and untreated composites were observed. The flexure strength is shown to be higher for the composite with 20% and comparable to that of the composites with 15% of untreated and sodium hydroxide treated fibers. The composites with 15% and 20% of fibers treated with silane were observed to exhibit the lowest flexure strength. In all cases, composites with 5% and 10% of treated fibers show no significant improvement. By contrast, the composites with untreated and treated fiber, as compared with the unfilled HDPE-r, do demonstrate significant differences in flexural strength. Table 1 Results of tensile test of the composites includes the mean values and standard deviation of the tensile parameters: nt stands for ‘‘not treated fiber’’, tn for ‘‘fiber treated with NaOH’’ and ts for ‘‘fiber treated with silane’’. Fiber (%) Toughness (MPa) Ultimate stress (MPa) Strain to failure Modulus (%) (MPa) 5-nt 5-tn 5-ts 10-nt 10-tn 10-ts 15-nt 15-tn 15-ts 20-nt 20-tn 20-ts 10.677 1.87 16.29 7 1.95 12.87 7 2.46 6.487 1.6 14.92 7 3.43 5.867 1.02 2.987 0.41 2.977 0.48 2.917 0.38 2.487 0.47 2.567 0.36 2.537 0.53 18.8 7 0.73 19.41 7 0.60 19.02 7 0.63 18.89 7 0.97 17.83 7 0.74 18.22 7 0.95 21.32 7 0.79 21.22 7 0.81 22.96 7 1.1 20.77 7 0.64 22.46 7 0.78 20.087 0.54 48.73 7 8.38 82.9 7 14.51 63.53 7 12.7 28.08 7 6.52 76.82 7 16.7 27.95 7 5.09 13.58 7 1.62 12.98 7 1.99 12.86 7 1.46 11.88 7 2.09 12.54 7 1.46 11.87 7 2.26 929.0 7 269 923.8 7 178 893.1 7 231 1047 7 20 958.2 7 231 982.7 7 30 1147 7 50 1228 7 25 1188 7 28 1216 7 47 1259 7 53 1240 7 17 Table 2 The mean values of the flexural properties, nt stands for ‘‘not treated fiber’’, tn for ‘‘fiber treated with NaOH’’ and ts for ‘‘fiber treated with silane’’. Fiber (%) Toughness (MPa) Ultimate stress (MPa) Strain to failure (mm/mm) Displacement (mm) 5-nt 5-tn 5-ts 10-nt 10-tn 10-ts 15-nt 15-tn 15-ts 20-nt 20-tn 20-ts 0.080 70.04 0.095 70.05 0.082 70.03 0.098 70.03 0.094 70.06 0.09 70.005 0.115 70.09 0.120 70.05 0.107 70.03 0.121 70.06 0.107 70.08 0.091 70.03 25.22 7 0.52 24.017 0.49 24.37 7 0.51 25.047 0.29 24.68 7 0.88 21.84 7 0.61 27.83 7 0.85 27.99 7 0.74 26.56 7 0.48 27.81 7 0.61 24.59 7 1.22 20.487 0.56 0.042 70.02 0.053 70.02 0.047 700 0.054 70.01 0.052 70.01 0.057 70.01 0.053 70.01 0.053 70.01 0.054 70.01 0.054 70.03 0.055 70.03 0.055 70.01 15.047 4.14 16.67 7 00 16.69 7 0.04 16.67 7 06 16.65 7 03 16.7 7 0.07 16.72 7 0 16.68 7 0 16.72 7 0 16.74 7 0 16.73 7 0 16.68 7 0 Fig. 3. Mechanical properties of composites as a function of treated and untreated fiber content: (a) tensile and flexure strengths and (b) tensile modulus. Please cite this article as: A. Elzubair, J.C. Miguez SuarezMechanical behavior of recycled polyethylene/piassava fiber composites, Materials Science & Engineering A (2012), http://dx.doi.org/10.1016/j.msea.2012.06.051 A. Elzubair, J.C. Miguez Suarez / Materials Science & Engineering A ] (]]]]) ]]]–]]] The tensile modulus of composites (Fig. 3b) increases progressively with the fiber content, the highest value being attained for composites with 20% of fibers treated with sodium hydroxide. It seems that the addition of fibers to HDPE-r produces an increase in the tensile modulus, independent of fiber treatment. Composites with untreated or treated fiber show similar mechanical behavior as the fiber amount decreased below 15 wt%. The mechanical results can be explained considering the following: First, the alignment of the fibers along the flowing direction during the injection process leads to an improvement in the tensile behavior. Secondly, the surface treatments of the fiber external layers cause a leaching out of cementing materials as well to a partial dissolution of fatty acids and phenol components resulting in a better mechanical interlocking between fiber and matrix. Finally, the alkali treatment produces a better interfacial fiber–matrix adhesion and, as a consequence, leads to a higher tensile modulus, especially, for composites with higher fiber content. 3.3. Scanning electron microscopy (SEM) Typical SEM micrographs of cross-sectioned (transversal) and longitudinal views of untreated fibers are shown in Figs. 4 and 5, respectively. Fig. 4 presents the fiber transversal view showing that piassava fibers have a cross-section which is neither circular nor fairly 5 uniform in its dimensions (Fig. 4a), which comprising a composite of tightly packed microfibrils with hollow cores (Figs. 4b–c); this is a common feature among the natural fibers [16,17]. Fig. 5 indicates that the fiber has an approximately cylindrical form (Fig. 5a) and that the fibers display also a superficial array of parenquimatic cells with spinulose bodies known as silica bodies or tylosis (Fig. 5b–c): the latter are commonly present in all palms [18]. SEM micrographs of treated piassava fibers (Fig. 6) show that both treatments produce a rougher longitudinal surface free of wax and impurities but with some cavities (these are the places from where the silica bodies have been removed, see Fig. 6a–b). It can be also noted that the internal structure remains intact and having no visible changes (Fig. 6c). It is recalled that the surface treatments, as seen in TGA, remove lignin, pectin, hemicelluloses, or any other fatty materials that might have an effect on the superficial appearance of the fiber. The fibers treated by NaOH show a cleaner surface with holes from the above-mentioned removal of spinulose silica bodies. On the other hand, fibers treated with silane exhibit rougher surfaces than the surfaces of the untreated ones. Figs. 7 and 8 present typical SEM photomicrographs of tensile fracture surfaces of composites of HDPE-r reinforced with untreated and treated piassava fibers. SEM analysis of the fractured tensile specimens of composites with untreated fibers show an occurrence of failure induced, Fig. 4. SEM microphotographs of cryogenic surfaces fracture of transversal section of untreated L. piassaba fibers: (a) transversal surface (lumen), (b) internal structure (fibril structure) and (c) vascular bundles. Please cite this article as: A. Elzubair, J.C. Miguez SuarezMechanical behavior of recycled polyethylene/piassava fiber composites, Materials Science & Engineering A (2012), http://dx.doi.org/10.1016/j.msea.2012.06.051 6 A. Elzubair, J.C. Miguez Suarez / Materials Science & Engineering A ] (]]]]) ]]]–]]] Fig. 5. SEM microphotographs of cryogenic surface fractures of longitudinal section of untreated L. piassaba fibers: (a) longitudinal surface; (b) silica bodies in the longitudinal wall and (c) detail of (b). Fig. 7. SEM microphotographs of tensile fracture surfaces of HDPE-r/untreated L. piassaba fibers composites: (a) 5% fiber and (b) 15% fiber. Fig. 6. SEM microphotographs of cryogenic surface fracture of treated L. piassaba fibers: (a) longitudinal surface after silane treatment; (b) longitudinal wall after silane treatment and (c) internal structure after alkali treatment. predominantly, by transversal fracture in the plane of the matrix. The fracture surfaces are rough and with a typical ductile nature. The fractured fibers have a random orientation showing a pull-out tendency that implies some matrix–fiber adhesion. The presence of fiber bundles in the 95/5 composites (Fig. 7a) suggests that; a composite with a smaller amount of fibers has lower mechanical strength, as indicated by the tensile tests results. SEM examination of fractured surfaces in the composites with treated fibers (Fig. 8) show modifications in the topographic aspects of the failure surfaces and normal fracture in the matrix plane. Additionally, no fiber pull-out was observed and the composites with treated fibers show, in comparison with the untreated ones, a better fiber adhesion to HDPE-r, especially for the alkalized fibers (Fig. 8b). These SEM features are in agreement with the mechanical results and support the observed changes in the properties of the HDPE-r/piassava fibers composites. 4. Conclusions The mechanical behavior of the recycled high-density polyethylene/piassava fiber composites has been analyzed with the Please cite this article as: A. Elzubair, J.C. Miguez SuarezMechanical behavior of recycled polyethylene/piassava fiber composites, Materials Science & Engineering A (2012), http://dx.doi.org/10.1016/j.msea.2012.06.051 A. Elzubair, J.C. Miguez Suarez / Materials Science & Engineering A ] (]]]]) ]]]–]]] – – – – 7 This improvement is best appreciated if compared with that of the recycled HDPE. Treatments of piassava fibers by sodium hydroxide and a silane coupling agent lead to an overall improvement of the mechanical properties of the composites. This is, most probably, due to an increase in the fiber–matrix adhesion and as such a higher strength. The thermal stability of cellulose (shown in TGA data) and the preservation of the internal structure of the microfibrils (observed in the SEM images) contribute to the improvement of the mechanical properties. The piassava fibers are suitable for application as a reinforcement phase in thermoplastic matrix composites and present a great potential even without any surface treatment. Recycled thermoplastics matrix composites with piassava fibers reinforcement can be used in the manufacture of light and/or low cost products but additional studies should be made before they are used in high performance structural applications. Acknowledgments The authors thank the Brazilian funding agencies FAPERJ, CAPES and CNPq for partial financial support. References Fig. 8. SEM microphotographs of tensile fractured surfaces of HDPE-r/treated piassava fibers composites: (a) 15% fiber (silane treated) and (b) 10% fiber (NaOH treated). aim of developing new non-traditional uses for piassava fibers; this is meant to lower the adverse effects on the income of the Brazilian rural population which were caused by the reduction of the fiber market. The following conclusions could be drawn from this investigation: – An addition of piassava fibers to HDPE-r, up to 20 wt%, improves the tensile and flexure behavior, especially the elastic modulus. [1] J.C. McCurrach, Palms of the World, Harper & Brothers, New York, 1960. [2] Encyclopedia Britannica, Vol. 17, WilliamBenton Pub, London, 1972. [3] E.B. Mano, L.C. Mendes, E. Braga-Junior, B. Chagas, G.A.A.P. Lopes, Textı́lia Braz. 35 (2000) 30–38. [4] K.K. Chawla, A.C. Bastos, Proceedings of the International Conference on Mechanical Behavior of Materials-III Cambridge, 1979, p. 191. [5] A.L. Marinelli, Polı́meros: Ciênc. Tecnol. (Braz.) 18 (2) (2008) 92–99. [6] D. Maldas, B.V. Kokta, Int. J. Polym. Mater. 27 (1994) 77–88. [7] G.W. Beckermann, K.L. Pickering, Composites A 39 (2008) 979–988. [8] A. d’Almeida, V. Calado, D. barreto, J.R. d’Almeida, J. Therm. Anal. Calorim. 103 (1) (2011) 179–184. [9] J.C.F. Walker, Wood Chemistry and Cell Wall Ultra-Structure: Primary Wood Processing, Chapman and Hall, London, 1993. [10] H.M. Wang, R. Postle, R.W. Kessler, Text Res. J. 73 (8) (2003) 664–669. [11] A. Elzubair, C.M.C. Bonelli, J.C. Miguez Suarez, E.B. Mano, J. Nat. Fibers 4 (2) (2007) 13–31. [12] N. Grassie, G. Scott, Polymer Degradation and Stabilization, Cambridge University Press, Cambridge, 1985. [13] B. Weulage, Th Lampke, G. Mars, K. Nestler, D. Starke, Thermochim. Acta 337 (1-2) (1999) 169–177. [14] K.G. Satyanarayana, K. Sukumaran, P.S. Mukherjee, C. Pavithran, S.G. Pillai, Cem. Concr. Compos. 12 (1990) 117–136. [15] J.J. Suñol, J. Saurina, F. Carrillo, M. Colom, J. Thermal, Anal. Calorim. 72 (2003) 753–758. [16] A.L. Lea~ o, J.C. Caraschi, I.H. Tan, in: E. Frollini, A.L. Lea~ o, L.H.C. Matoso (Eds.), Natural Polymers and Agrofibers Based Composites, 2000, pp. 257. [17] J. Kuruvilla, L.H.C. Matoso, Proc. of 3rd Int. Symposium on Natural Polymers and Composites, Sa~ o Carlos, SP, Brazil, 2000, p. 333. [18] P.B. Tomlinson, in: C.R. Metcalfe (Ed.), Palmae, Vol. II, Clarendon Press, Oxford, 1961, pp. 52–55. Please cite this article as: A. Elzubair, J.C. Miguez SuarezMechanical behavior of recycled polyethylene/piassava fiber composites, Materials Science & Engineering A (2012), http://dx.doi.org/10.1016/j.msea.2012.06.051