Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam S.M. Mousavi 1, *, A. Aghili 2, S.A. Hashemi 3, N. Goudarzian 4, Z. Bakhoda, and S. Baseri 1 Department of Chemical Engineering, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz 7134, Iran 2 Department of Polymer Engineering, Shiraz Branch, Islamic Azad University, Shiraz, Iran 3 Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran 4 Department of Applied Chemistry, Shiraz Branch, Islamic Azad University, Shiraz, Iran Department of Chemistry, Shahid Chamran, Ahvaz University, Iran Received: 29 February 2016, Accepted: 9 August 2016 Summary Surface modification of linear lowdensitypolyethylene (LLDPE), ethylenecovinyl acetate (EVA), and clay nanoparticles composite films was promoted by potassium permanganate solutions in HCl acidic medium using eight conditions by variation times and temperature, also concentrated oxidation solution of LLDPE and EVA blend films shows a very good clarity and tensile properties, this property can be improved by adding the clay nanoparticles as a filler in the composite. The influence of electron beams (EB) irradiation and amount of clay nanoparticles loading on the overall properties of linear lowdensity polyethylene (LLDPE) /ethylenecovinyl acetate blends was investigated. Samples were subjected to the EB irradiation with the dose values of 7 and 10kGy, afterwards mechanical and thermal properties of the LLDPE/EVA blends with and without clay nanoparticles at different irradiation dosages were utilized in order to analyze the characteristics of the final composite. These enhanced properties are due to the homogenize dispersion of Clay nanoparticles in LLDPE matrix. Moreover, in order to verify these characteristics and compare composite samples with and *Corresponding author: S.M. Mousavi; kempo.smm@gmail.com Smithers Information Ltd, 2016 Polymers from Renewable Resources, Vol. 7, No. 4, 2016 13
S.M. Mousavi, A. Aghili, S.A. Hashemi, N. Goudarzian, Z. Bakhoda, and S. Baseri without Clay nanoparticles (Cloisites 30B), some tests such as DSC, TGA, PSA, SEM and Optical Micrographs (OM) were taken from the samples. Keywords: Clay nanoparticles, Linear low density poly ethylene, Vinyl acetate, Electron beam (EB) INTRODUCTION Polyethylene (PE) is one of the most important polymeric materials which are widely used in engineering, construction, sports, domestics and packaging applications. The most common type of PE is high density polyethylene (HDPE) and low density polyethylene (LDPE). PE is a versatile polymer due to its properties which can be easily shaped via modification of structure or through process conditions [1]. Nevertheless, these kinds of materials were rarely used as neat polymers as the application is restricted by its melting point and swelling in hydrocarbons. Besides, in order to fulfill the increasing demand for PE in polymer applications, various additives were incorporated to be compounded with PE. In addition, additives such as fillers, plasticizers, antioxidants, stabilizer and flame retardants were added into PE in order to achieving specific properties for certain applications. Furthermore, in order to improve the mechanical and thermal properties of the neat polymer, the polymers were usually compounded with mineral fillers. Mineral fillers are the most conventional fillers that were used in thermoplastic industry to enhance the properties of polymeric products [2]. In work that had been conducted by Nwanonenyi et al. [3], they have investigated the effect of particle sizes, filler contents and compatibilization on the properties of LDPE filled periwinkle shell powder. The results shows that increase in the amount of filler and compatibilizer content at lower particle size can lead to the enhancement of mechanical performance especially elongation at break, tensile strength, modulus, hardness, flexural strength and the impact strength. In another work by Huang et al. [4], they have examined systems based on polyethylene and its copolymers. The polymer blend nanocomposite, obtained by this way, provides a new class of materials which combines the properties of polymer nanocomposite and polymer blends []. The poor flame resistance of LDPE EVA blends is mainly attributed to their hydrocarbon origin. The flame resistance of LDPE EVA blends could be improved by incorporating fire retardants [6]. The LDPE EVA matrix has significantly increased the stiffness and Young s modulus of nonirradiated and irradiated LDPE EVA blends. The increment of MMT loading level from 2. to 10 phr has gradually increased the Young s modulus of LDPE EVA blends under various irradiation dosages. The incorporation of MMT particles into ATH added LDPE EVA matrix has effectively enhanced the Young s modulus 136 Polymers from Renewable Resources, Vol. 7, No. 4, 2016
Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam by intercalating of LDPE EVA matrix into the interlayer galleries of MMT particles [7]. This can be attributed to the formation of crosslinking networks in LDPE EVA matrix that can highly restrict the mobility of LDPE EVA chains while they want to slippage between each other and thus enhancement of the Young s modulus and stiffness of the LDPE EVA blends. This phenomenon indicated that the formation of crosslinking networks of added ATH to LDPE EVA matrix could further enhance the reinforcement effect of the ATH particles in the LDPE EVA matrix by enhancing the interfacial adhesion (compatibility) within the ATH particles and LDPE EVA matrix [8]. Besides, addition of MMT particles into ATH/LDPE EVA matrix could finely intercalate into the cavities between the ATH particles and LDPE EVA matrix. LDPE EVA matrix can effectively intercalate into the interlayer galleries of MMT particles, while the ATH particles were attached to the polar section of MMT particles [9]. Moreover, the gas barrier properties of MMT filler in the LDPE EVA matrix could also impede the diffusion of flammable volatile gases from mixing with free oxygen during combustion process that can led to retardation of the combustion process of ATH/LDPE EVA blends [10]. The increment of the MMT loading level in the matrix of ATH/LDPE EVA blends could act as a char formation promoter by forming a protective layer on the surface of polymeric matrix that can led to delay in the combustion process [11, 12]. The intercalation effect of MMT particles could increase the distance between the interlayer galleries of MMT particles as indicated by the increment in dspacing value of samples. This can be explained where the hydrophobic section of MMT nanoparticles enables the molten LDPE EVA matrix to intercalate effectively into the interlayer galleries of MMT particles with the expanded dspacing [13]. The relation between the morphology of LDPE/EVA blends and their mechanical and electrical properties were also reported in several publications [14]. Several studies were indicated that the gel content and the cross linking density of EVA/LDPE blends at the optimum radiation dose increased with the higher amount of EVA content, and the highest gel content was observed when the amount of EVA in the blend reaches 30 wt% [1]. Although in the systems based on polyethylene and its copolymers, this amount was found by far less. The polymer blend nanocomposite that obtained by this way, provided a new class of materials which combined the properties of polymer nanocomposite and polymer blends [1617]. In addition, in order to enhance the performance and processability of the blend, it is necessary to tend the crosslinking of the blend by use of a suitable manner. Crosslinking with highenergy irradiation such as electron beam (EB) has attracted much attention due to the easiness and cleanness of the process [18]. Radiationinduced crosslinking often leads to the improvement of thermal stability, mechanical properties, electrical insulation properties, solvent resistance and melt strength of the LDPE/EVA blends [19]. Polymers from Renewable Resources, Vol. 7, No. 4, 2016 137
S.M. Mousavi, A. Aghili, S.A. Hashemi, N. Goudarzian, Z. Bakhoda, and S. Baseri The aim of this paper is to investigate the effect of clay nanoparticles on the morphological, thermal and mechanical properties of LDPE/EVA nanocomposites. Besides, the influence of clay nanoparticles loading and EB irradiation (7KGy and 10kGy) on the structural, mechanical, thermal, and electrical characteristics of LDPE/EVA matrix was investigated. EXPERIMENTAL Materials EVA copolymer GREENFLEX FF (VA content 19 wt%, melt index 0.7, density 0.92 g/m 3 ) that was supplied by the Polymery Europa, used as a polymeric matrix. Also the linear low density polyethylene was supplied by Tondgooyan Petrochemicals and the clay nanoparticles (Cloisites 30B) was supplied by Southern Clay Chemistry. Moreover, nanoparticles size was determined by PSA to be 36 nm. Figure 1 depicts the diagram of clay nanoparticles size that was used in this study. Figure 1. Diagram of nanoparticle size (PSA) for the clay nanoparticles Manufacturing Process For the production of composite samples, first clay nanoparticles were dispersed in an acetone solvent by ultrasonic mixer with 300w power and 7 C temperature limit, then the clay/acetone solvent was placed in to the heat oven for 8 h at 80 C for removal of the acetone and also further humidity reduction. Then LLDPE, EVA and clay nanoparticles ( wt%) were poured into the screw extruder (the screw extruder was manufactured by 138 Polymers from Renewable Resources, Vol. 7, No. 4, 2016
Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam Brabender, Germany) and mixed in 14010 C with 80 rpm rotor speed for 12 min. Then the resulting blend was poured into the cast and cooled in room temperature. After completion of the curing process, samples were cut into the desire shape and then ultrasonically cleaned with ethanol in order to remove organic materials from the surface of samples. Furthermore, samples were dried by heat oven at 0 C for 1 h and then for modification of samples surface, samples were submitted to different oxidation processes. In the first oxidation process, samples were placed into the KMnO 4 /HCl 0.0/.10 mol/l solution for 2 h at 2 C. Then samples were quickly washed in 37% (w/v) HCl for removal of oxidation residues from the samples surface and cross section. Then some specific samples were subjected to EB irradiation with two different dose levels, 7 and 10kGy. In addition, the irradiation was performed by the Rhodotron type EB accelerator machine (TT200 model) at an acceleration voltage and current of 10mV and 10mA respectively. Besides, for measuring the mechanical properties of manufactured samples, Pavan Sonnet 100t injection machine with a 42 mm diameter screw at 180 C and an injection pressure of 3 bar was used. In addition TGA and DSC tests were performed by using Shimadzu TGA0 and Mettler Toledo DSC1/00 analyzer. Moreover, specification of manufactured samples and their manufacturing condition can be seen in Table 1. Besides, a view of manufacturing process can be seen in Figure 2. Figure 2. Steps of manufacturing method, also in step 1, numbers 110 shows: 1. engine, 2. feeder, 3. cooling jacket, 4. thermocouple,. screw, 6. barred, 7. heating jacket, 8. head, 9. dies and 10. cutter, respectively Polymers from Renewable Resources, Vol. 7, No. 4, 2016 139
S.M. Mousavi, A. Aghili, S.A. Hashemi, N. Goudarzian, Z. Bakhoda, and S. Baseri Table 1. Samples specification Sample Code A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3 C4 LLDPE content (wt%) 9 8 7 6 9 8 7 6 9 8 7 6 EVA content (wt%) 10 20 30 10 20 30 10 20 30 Nano Clay content (wt%) Electron Beam (KGy) 7 7 7 7 10 10 10 10 RESULTS AND DISCUSSION Tensile Test Tensile strength and modulus tests were performed according to the ASTMD638 standard. Besides, composite samples were submitted to tensile tests on an EMIC DL 2000 machine (made by an Iranian company) at a constant crossspeed of 0 mm/min. Dumbbell specimens with 2 mm thickness and 40100 mm 2 surface area were cut from molded sheets with a Wallace die cutter S6/1/4A. Five specimens were used in each case and the average value was selected. Tensile strength and elongation at break data were recorded directly from the digital displays at the end of the each test. Tensile properties were determined for eight different kinds of samples (Table 1) from each composition. In addition, the effect of EB irradiation on the tensile properties of the LLDPE/EVA/Clay nanoparticles nanocomposites can be seen in Figure 3. As can be seen in this figure, by increase in amount of EB irradiation dose level, the amount of tensile strength was increased. However, the trend of variation of these tensile properties values for samples containing EVA are similar to those that was not applied to EB irradiation. The EB irradiation will not affect the microstructure of samples and thus the amount of tensile strength for samples that were affected by EB irradiation was similar to samples that were not subjected to EB irradiation. Moreover, it is revealed that the improvement in the tensile properties is mainly achieved at 7kGy and further increase in irradiation dose value to 10kGy, did not affect the 140 Polymers from Renewable Resources, Vol. 7, No. 4, 2016
Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam mechanical properties of samples significantly. These behaviors correspond to the variation of gel content versus dose value in which a substantial increase in crosslinking density was observed at 7kGy. In summary, improvement of mechanical properties of composite samples can achieved due to EB irradiation, but these improvement in lover EB dose level is similar to higher ones. A view of tensile properties of all samples can be seen in Figure 3. Figure 3. Tensile strength of different samples As can be seen in Figure 3, increase in the EVA content can led to increase in the overall amount of tensile strength (samples A1A4). In addition, for samples B1B4, EB irradiation with 7GKy dosage caused decrease in the overall amount of tensile strength due to addition of EVA to the blend. These amounts for sample B3 is much higher than samples B1 and B2. Besides, increase in the EB irradiation dosage level to 10KGy caused increase in overall amount of tensile strength (samples C1C4). Moreover, increase in the weight percentage of EVA from 10 wt% to 20 wt% for both B and C samples can led to increase in the tensile strength, but increasing in the EVA weight percentage more than 20 wt% with EB irradiation treatment can led to decrease in the tensile strength. These results indicates that EB irradiation can highly affect the microstructure of composite samples that can led to increase in the tensile strength and surface modification of composite samples. Elongation at Break Elongation at break increased due to increase in overall amount of fillers and additive content, a view of these values for each sample can be seen in Figure 4. Besides, increase in the amorphous regions in the presence of the EVA can led to increase in the mobility of polymer chains. However, for LLDPE/ Polymers from Renewable Resources, Vol. 7, No. 4, 2016 141
S.M. Mousavi, A. Aghili, S.A. Hashemi, N. Goudarzian, Z. Bakhoda, and S. Baseri EVA/Clay nanocomposite, sample A4 has the highest value for elongation at break, this result clearly shows that increase in the overall amount of the EVA content can led to increase in the value of elongation at break. Moreover, EB irradiation was led to decrease in the elongation at break for the samples B and C due to the restriction in the mobility of the polymer chains that was caused due to the strong crosslinking between the polymeric materials. Lowest amount of elongation at break was observed for samples C4. This result clearly shows that EB irradiation and also increase in the dose level of EB irradiation can led to decrease in the overall amount of elongation at break. In addition mechanical properties of all samples can be seen in Table 2. Figure 4. Elongation at break of different samples Table 2. Mechanical properties obtained from tensile and elongation test Sample Code A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3 C4 Tensile Strength 9.622 10.14 9.699 11.428 12.768 11.321 12.737 12.13 12.77 13.32 1.207 13.229 Elongation at Break (mm) 410.86 6.37 72.371 719.92 83.400 3.629 608.03 662.766 01.27 74.731 434.474 377.971 Clay content (wt%) EB irradiation dose (KGy) 7 7 7 7 10 10 10 10 142 Polymers from Renewable Resources, Vol. 7, No. 4, 2016
Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam As can be seen in Figure 4 and Table 2, increase in the EVA content can led to increase in the overall amount of elongation at break that is due to increase in the flexibility of composite samples. Besides, EB irradiation and also increase in the irradiation dosage can led to decrease in the elongation at break that is due to decrease in the flexibility of composite samples. For samples B2B4, increase in the EVA content with EB irradiation (7KGy) treatment can led increase in the elongation at break but for samples C2C4 this phenomenon is reverse. Decrease in the elongation at break for samples C2C4 (with increase in the EVA content) with higher irradiation dosage shows the significant effect of EB irradiation on the microstructure that can led to improvement in the tensile strength and decrease in the elongation at break due to decrease in the flexibility of the composite samples. Thermogravimetric Analysis (TGA) TGA test was performed by Shimadzu TGA0 under flowing nitrogen (20 ml/ min) atmosphere by 10 C/min temperature growth rate. 6 mg of each sample was placed in a platinum pans and the change in weight vs temperature was measured. The thermogravimetric analysis weight loss results of LLDPE/EVA/ Clay nanocomposite of untreated and treated samples by EB irradiation can be seen in Figures 7. Moreover, composite samples were subjected to the EB irradiation with the dose values of 7 and 10kGy under four conditions. Furthermore, a reasonable explanation for the achieved data is that in mild oxidation and EB irradiation conditions, a crosslinked structure was formed between the oxidized polymer chains on the film surface, which slowed down the thermal degradation in the TGA analysis in nitrogen atmosphere. On the other hand, in the harsh condition, the polymer degradation rate increased by EB irradiation and oxidation process caused decrease in the thermal stability of the LLDPE/EVA/clay nanocomposite films. Moreover by decrease in the thermal stability of the oxidized polymer, the weight loss due to increase in the temperature for samples that were not subjected to the EB irradiation was much larger than treated samples. This fact suggests that the weight loss mechanism for this kind of nanocomposite was changed due to electron beam and oxidation process. As can be seen in Figure, increase in the EVA content (without EB irradiation) can led to significant increase in the thermal stability of composite samples, but increase in the weight percentage of EVA more than 30 wt% can led to significant decrease in the overall values of thermal stability. These results for samples A1A4 shows that increase in the EVA content until 20 wt% can led to significant increase in the overall amount of thermal stability, but increasing in the EVA content more than 20 wt% can led to significant decrease in the thermal stability that is lower than all of Polymers from Renewable Resources, Vol. 7, No. 4, 2016 143
S.M. Mousavi, A. Aghili, S.A. Hashemi, N. Goudarzian, Z. Bakhoda, and S. Baseri samples (A1A4). Moreover, as can be seen in Figure 6, EB irradiation with 7KGy dosage can led to decrease in the overall thermal stability for samples B2 and B4 in comparison with sample B1. But it seems that sample B3 with 20 wt% EVA content has the highest values for thermal stability. This results indicate that optimum content of EVA with EB irradiation (7KGy) can led to significant increase in the overall values of thermal stability. But increase in the EB irradiation dosage from 7KGy to 10KGy can led to significant decrease in the overall amount of thermal stability for samples containing EVA. But the thermal stability for samples C3 is higher than samples C2 and C4. This result shows that the best EVA content for production of composite samples containing LLDPE/EVA/clay nanoparticles is 20 wt%. Figure. TGA results for samples A1A4 Figure 6. TGA results for samples B1B4 144 Polymers from Renewable Resources, Vol. 7, No. 4, 2016
Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam Figure 7. TGA results for samples C1C4 Differential Scanning Calorimetric Analysis (DSC) LLDPE/EVA/Clay nanocomposites were subjected to differential scanning calorimetry (DSC) test using Mettler Toledo DSC1/00 analyzer. In this stage, composite samples were heated up from 2 C to 20 C and then cooled from 20 C to 2 C, under nitrogen flow at rate of 10 ml per minutes. The samples were cut and weighted before placing into the aluminum sealed pan. The melting and crystallization temperature was determined through the graph that was obtained from the instrument. Isothermal kinetics crystallization of composite samples were accompanied by a significant heat release. By assuming that the evolution of crystallinity is linearly proportional in comparison to the evolution of the released heat during the crystallization, thus the relative degree of crystallinity can be measured by DSC. In addition, The quantitative data extracted from both heating and cooling thermograms, including melting point and crystallization temperatures, were summarized in the Figures 813 that representing the melting temperature of their crystalline phase. Besides, for samples containing lower EVA content, no distinctive peak corresponding to the EVA phase is detectable. Furthermore, for the samples containing higher EVA weight percentages, very small peak relevant to the EVA phase was observed. In Figures 8 and 9, crystallization and heat flow rates of different samples were represented. Besides, in Figures 10 and 11, crystallization and melting point rates of different samples were represented. Moreover EB irradiation boost in here was led to degradation in the polymeric structure of composite samples. Besides, in Figures 12 and 13 crystallization and heat flow rates of samples A, B and C with respect to EVA Polymers from Renewable Resources, Vol. 7, No. 4, 2016 14
S.M. Mousavi, A. Aghili, S.A. Hashemi, N. Goudarzian, Z. Bakhoda, and S. Baseri content were presented. Moreover in Figure 14 crystallization and melting of samples B and C with respect to the EVA content can be seen. Figure 8. Crystallization and heat flow rates for samples A1, B1and C1 (left side) and for samples A2, B2 and C2 (right side) due to the EB irradiation Figure 9. Crystallization and heat flow rates for samples A3, B3 and C3 (left side) and for samples A4, B4 and C4 (right side) due to the EB irradiation Figure 10. Crystallization and melting point rates for samples A1, B1 and C1 (left side) and for samples A2, B2 and C3 (right side) 146 Polymers from Renewable Resources, Vol. 7, No. 4, 2016
Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam Figure 11. Crystallization and melting point rates for samples A3, B3 and C3 (left side) and for samples A4, B4 and C4 (right side) Figure 12. Crystallization and heat flow rates for samples A1, A2, A3 and A4 (left side) that containing 0, 10, 20 and 30 wt% EVA and for samples B1, B2, B3 and B4 (right side) that containing 0, 10, 20 and 30 wt% EVA respectively Figure 13. Crystallization and heat flow rates for samples C1, C2, C3 and C4 (left side) and crystallization and melting point rates for samples C1, C2, C3 and C4 (right side) that containing 0, 10, 20 and 30 wt% EVA respectively Polymers from Renewable Resources, Vol. 7, No. 4, 2016 147
S.M. Mousavi, A. Aghili, S.A. Hashemi, N. Goudarzian, Z. Bakhoda, and S. Baseri Figure 14. Crystallization and melting point rates for samples B1, B2, B3 and B4 (left side) and for samples C1, C2, C3 and C4 (right side) that containing 0, 10, 20 and 30 wt% EVA respectively Optical Microscopy (OM) For better evaluation of composite samples and effect of EB irradiation on the composite samples surface, digital optical microscope was used. Optical images of samples A, B and C can be seen in Figures 1, 16 and 17 respectively. As can be seen in Figure 1, samples A have some voids and defect on their surface. In addition, optical images shows non smooth surface of the samples and also crack growth in some areas. Moreover Figure 16 shows the Figure 1. Optical images from surface of samples A1A4, number 1 shows the clay dispersant inside the polymeric substrate and number 2 shows crack growth on the surface of the samples 148 Polymers from Renewable Resources, Vol. 7, No. 4, 2016
Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam optical images of samples B, as can be seen in this figure, samples B have smoother surface than samples A that is due to EB irradiation. Also there is very lower amount of voids and defect on these samples surface than samples A. Besides, as can be seen in Figure 17, by increase in the overall value of Figure 16. Optical images from surface of samples B1B4, number 1 shows the clay dispersant inside the polymeric substrate and number 2 shows crack growth on the surface of the samples Figure 17. Optical images from surface of samples C1C4, number 1 shows the clay dispersant inside the polymeric substrate and number 2 shows crack growth on the surface of the samples Polymers from Renewable Resources, Vol. 7, No. 4, 2016 149
S.M. Mousavi, A. Aghili, S.A. Hashemi, N. Goudarzian, Z. Bakhoda, and S. Baseri the EB irradiation from 7 to 10KGy, samples with smoother surface can be obtained. Optical micrograph of samples C indicate that increase in the EB irradiation dosage can led to creation of smoother surface and decrease in the overall voids and defects and also crack growth near the surface of samples. Scanning Electron Microscopy (SEM) For better evaluation of composite samples surface and also fillers dispersant near the surface, SEM analysis was taken from the samples. SEM images shows agglomerated bulks of clay nanoparticles throughout the composite samples surface. In addition effect of EB irradiation on the surface modification of samples can be seen in Figures 1820. As can be seen in Figure 18, untreated sample to EB irradiation has rougher surface than treated samples. In Figures 19 and 20 effect of 7 and 10KGy EB irradiation on the surface of samples can be seen, respectively. Increase in the dosage of EB from 7 to 10KGy can led to significant modification of composite samples surface that can be used in various industries such as marine industries. Figure 18. SEM images from surface of untreated sample to EB irradiation Figure 19. SEM images from surface of sample that was treated to 7KGy EB irradiation 10 Polymers from Renewable Resources, Vol. 7, No. 4, 2016
Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylenecovinyl Acetate and Nano Clay Particles by Electron Beam Figure 20. SEM images from surface of sample that was treated to 10KGy EB irradiation CONCLUSIONS In this study, with a multi stage manufacturing process composite samples containing LLDPE/EVA/clay nanoparticles were fabricated. Then, samples with various content of LLDPE and EVA and with constant content of clay nanoparticles were subjected to various oxidation and modification processes. Oxidation process was conducted by placing the samples in the KMnO4/HCl solution and then samples surface were modified by EB irradiation. Besides, effect of various additives on the mechanical and thermal properties was investigated. In addition by digital optical microscope and SEM images, effect of EB irradiation and oxidation process on the surface of the samples were evaluated. Results indicated that increase in the EVA content can led to increase in flexibility of composite samples that can led to increase in the elongation at break, but this filler can led to decrease in the tensile strength. Further, EB irradiation can lead to increase in the tensile strength but it will cause significant decrease in the elongation at break. By increase in the overall amount of EB irradiation dosage from 7 to 10KGy, the flexibility and thus elongation at break will decrease but the tensile strength will increase. Moreover, the increase in the EVA content more than 20 wt% can led to a decrease in the thermal stability of composite samples. Furthermore, increase in the EB irradiation dosage from 7 to 10KGy can lead to significant decrease in the overall value of thermal stability with the presence of EVA. Besides, SEM and optical images indicated that increase in the EB irradiation dosage from 7 to 10KGy can lead to significant modification of samples surface. In summary, optimum selection of additive and fillers with certain dosage of EB irradiation can lead to increase in the mechanical and thermal properties and also surface modification of composite samples. Polymers from Renewable Resources, Vol. 7, No. 4, 2016 11
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S.M. Mousavi, A. Aghili, S.A. Hashemi, N. Goudarzian, Z. Bakhoda, and S. Baseri 14 Polymers from Renewable Resources, Vol. 7, No. 4, 2016