Determination of Elastic Constants of Epoxy Resin/ Biochar Composites by Ultrasonic Pulse Echo Overlap Method
Imran Oral Ahmet Kelesoglu Faculty of Education, Department of Physics Education, Necmettin Erbakan University, 42090 Meram Yeniyol, Konya, Turkey
This study is carried out in order to determine the elastic properties of Epoxy Resin (ER) Composites reinforced with various mixtures of China Poplar Char (CPC) and Pine Cone Char (PCC) as biochars by ultrasonic wave velocity measurement method. The prepared chars are mixed with epoxy resin matrix at weight percentages of 10%, 20%, and 30% for preparing the ER/Biochars (BC) composites. The effect of biochar amounts on the elastic properties of the ER/ BC composites are investigated by ultrasonic pulse echo overlap method. The morphologies of the samples are investigated by scanning electron microscopy. Based on the findings obtained from the present study, forming of the ER/CPC composites gives better values of elastic properties compared to forming of the ER/ PCC composites. According to the obtained results, the composition ratio of 70:30 is the most appropriate composition ratio for both of the ER/CPC and the ER/ C PCC composites. POLYM. COMPOS., 00:000–000, 2015. V 2015 Society of Plastics Engineers
INTRODUCTION The sustainable utilization of forest resources has been adversely influenced with increasing population of the world. The wastes of wood is one of the major environmental concern that needs to be dealt with to minimize the amount of municipal solid waste, depletion of natural resources, saving the environment and enhancing the sustainability concept for future generations’ use. Therefore, growing demand for wood polymer composites has led to continuous efforts to find new resources as an alternative to wood. Large quantities of pine cones and wood shavings are produced annually throughout the world, especially in pulp and paper industry. Wood shavings and pine cones Correspondence to: Imran Oral; e-mail:
[email protected] Contract grant sponsor: The Scientific and Technological Research Council of Turkey (TUBITAK) within the International Postdoctoral Research Scholarship Programme(2219/2014-1/1059B191400765) and Konya Necmettin Erbakan University. DOI 10.1002/pc.23488 Published online in Wiley Online Library (wileyonlinelibrary.com). C 2015 Society of Plastics Engineers V
POLYMER COMPOSITES—2015
are rarely used as reinforcement in polymer composites. Because of their fibrillar morphology and good mechanical properties, the pine cone was used as filler in several materials [1]. However, the pine cone fibers are mainly used as biosorbent for metal and dye waste waters [2, 3]. The ecofriendly biocomposites have the potential to be a new generation material which can be partial solution to many global environmental problems. Recent advances in the use of biofibers in polymer composite are carried out [4–10]. The biofiber polymer composites can be used instead of synthetic fiber-reinforced composites in various applications like automotive industry [5]. Pyrolysis is also considered to be an effective technology to recycle the wood wastes, by which biomass can be converted to valuable bio-oils, char, and gaseous products. Char formation is likely the most important condensed phase mechanism to modify the combustion process of polymers [11]. Many studies in the related literature have focused on using biochar as an adsorbent for the removal of heavy metals and organic pollutants from water [12–19]. Also, in related literature there are many studies [20–23] on the preparation of composites filled with biofillers. Mishra et al. [24] have determined the mechanical and impact behavior of agrowaste pineapple leaf fiber. Shah and Lakkad [25] studied mechanical properties of unidirectional jute and glass fibers with epoxy and polyester resins as matrix. As it is seen in the literature, there are limited studies related with the usage of biochars (BC) with epoxy resin (ER) and also ultrasonic characterisation of these materials. Ultrasonics, which is a subcategory of acoustics, deals with acoustics beyond the audio limit (20 kHz). In general, the ultrasonic wave velocity and attenuation are most required parameters for the ultrasonic nondestructive characterization or evaluation of materials. Ultrasonic velocity can be used for the determination of elastic constants (shear modulus, bulk modulus, Young’s modulus, and Poisson’s ratio), microstructure (grain size, texture, density, etc.), discontinuity (porosity, creep damage, fatigue damage, etc.), and mechanical properties (tensile strength, shear strength, hardness, etc.) [8, 26]. It is also
TABLE 1. Contents of epoxy resin and the ER/BC composites.
Sample ID
Composition ratio of ER/BC (wt%)
Hardener amount (wt%)
Catalyst (wt%)
ER ER-PCC1 ER-PCC2 ER-PCC3 ER-CPC1 ER-CPC2 ER-CPC3
100:0 90:10 80:20 70:30 90:10 80:20 70:30
30 30 30 30 30 30 30
1 1 1 1 1 1 1
80:20 and 70:30 ratios as well. The composites obtained are named as ER-PCC2 and ER-PCC3, respectively. By the same procedure, the composites of epoxy resin (ER)/ China poplar char (CPC) are prepared and they are named as ER-CPC1, ER-CPC2, and ER-CPC3 too. Only one sample which has 20 mm 3 20 mm 3 20 mm dimensions, is obtained for each kind of composites. The contents of ER and the ER/BC composites are given in Table 1. Measurements
important in low temperature physics because it is involved in the evaluation of Debye average velocity and Debye temperature [26, 27]. Ultrasonic velocity in nanofluid depends on the concentration of nanoparticles of material dispersed in polymer matrix, therefore it is not only important at bulk scale but also at nanoscale. Thus, the materials can be characterized with the knowledge of ultrasonic parameters under different physical conditions. To our knowledge, no ultrasonic study have been done yet on the ER/BC. Therefore, this paper aims to determine the elastic properties of the ER/BC composites which are formed by recycling useful wastes obtained from sawdust waste of natural China Poplar and Pine Cone, using ultrasonic pulse echo overlap method. MATERIAL AND METHOD Materials Epoxy resin used is DER321, which is based on diglycidyl ether of bisphenol-A (Dow Chemical Company, USA) and the curing agent is a cycloaliphatic polyamine called Polypox H 043 (Dow Chemical Company, USA). The catalyst (2,4,6-tris [dimethylaminomethyl) phenol) was obtained from Sigma-Aldrich, USA. The raw carbon materials pine cone char (PCC), and China poplar char (CPC) are obtained by the pyrolysis of pine cones, and China poplar shavings at 450 C, respectively. Preparation of ER/BC Composites Pine cone char (PCC) is ground to obtain char powder before being mixed with epoxy. The obtained PCC (particle size
