Reinforced Ternary Blend Based Blown Films of LLDPE/LDPE/PLA/MA-g-PE

Transcription

1 Modified Nano-CaCO 3 Reinforced Ternary Blend Based Blown Films of LLDPE/LDPE/PLA/MA-g-PE Modified Nano-CaCO 3 Reinforced Ternary Blend Based Blown Films of LLDPE/LDPE/PLA/MA-g-PE Rahul Kumar 1, Pradeep Upadhyaya 1* and Navin Chand 2 1 Central Institute of Plastics Engineering and Technology (CIPET), Lucknow, India, Advanced Materials and Processes Research Institute (AMPRI), Bhopal, India, Received: 2 April 2014, Accepted: 28 June 2014 Summary Ternary blend system of linear low density polyethylene (LLDPE), low density polyethylene (LDPE) and poly lactic acid (PLA) compatibilized with maleic anhydride grafted polyethylene (MA-g-PE) has been reinforced by chemically modified nano calcium carbonate (nano-caco 3 ). The mechanical, optical, thermal and morphological properties of the reinforced ternary blend have been evaluated. Mechanical properties are superior at 1 phr of nano-caco 3 filler, except elongation at break and burst strength. Optical properties study indicates that haze and transmittance have been affected due to the nucleating effect of nano-caco 3 on the matrix. SEM micrographs show reasonably well bonding between the matrix and the reinforcement material. INTRODUCTION In spite of environmental problems, polyolefins and their reinforced and unreinforced blends are extensively used in packaging applications because of their low cost, low density, chemical inertness, and easy processibility [1, 2]. Biodegradable polymers, like poly lactic acid, may degrade in soil, sludge water, and by enzymatic or by microbial attack; and may not be used, on their own, because of their techno-economic limitations [3, 4]. * pradeepcipet@sify.com Smithers Information Ltd., 2014 Applied Polymer Composites, Vol. 2, No. 2,

2 Rahul Kumar, Pradeep Upadhyaya and Navin Chand Efforts are being made to blend polyolefins with bio polymers and also to reinforce the blend with nanoparticles. X-ray diffraction and transmission electron microscopy showed [5] that titanate layers were intercalated and nicely distributed in the pla matrix; and thus the properties of PLA improved upon formation of its nano-composite. Linear low density polyethylene (LLDPE) based composites [6], with micro and nanoparticles of amorphous silicon dioxide (SiO 2 ) as reinforcement, have been processed by melt blending and compounding. X-ray studies have indicated that 1% wt of organo-montmorillonite (OMMT) exhibits the exfoliated structure in polyethylene nano-composites [7]. Impact strength, elastic modulus and toughness of nano CaCO 3, nano TiO 2, and nano ZnO reinforced polyvinyl chloride (PVC) has been reported to be higher than that of PVC due to formation of the nano-composite [8]. CaCO 3 reinforced SF/PVA system has also been developed [9]. This study aims to investigate ternary blend system of linear low density polyethylene (LLDPE), low density polyethylene (LDPE) and poly lactic acid (PLA) compatibilized with maleic anhydride grafted polyethylene (MA-g-PE) and further reinforced by chemically modified nano calcium carbonate (nano- CaCO 3 ). MATERIALS AND THEIR TREATMENTS Materials Blown film grade Butene-linear low density polyethylene (trade name: Sabic LLDPE 118W; Density=918 kg/m 3, MFI=1.0 g/10 min at 190 C and 2.16 kg) was supplied by Saudi Basic Industries Corporation, Saudi Arabia. General purpose film grade low density polyethylene (trade name: Relene 24FS040; Density=922 kg/m 3, MFI=4.0 g/10 min at 190 C and 2.16 kg) was obtained from Reliance polymers, India. Sheet extrusion grade Poly lactic acid (trade name: Revode 101, Density=1250 kg/m 3, MFI=2-10 g/10 min at 190 C and 2.16 kg) was obtained from Zhejiang Hisun Biomaterials Co., Ltd., China. Maleic anhydride grafted polyethylene was obtained from Pluss Polymers, India. Nano calcium carbonate (trade name: Calcia-nano C) was supplied by Zirox Technologies, India. Titanate coupling agent (EB-1019A) was purchased by IPMC, Pune, India. 86 Applied Polymer Composites, Vol. 2, No. 2, 2014

3 Modified Nano-CaCO 3 Reinforced Ternary Blend Based Blown Films of LLDPE/LDPE/PLA/MA-g-PE Treatment of Nano Calcium Carbonate with Titanate Coupling Agent Calculated titanate coupling agent was mixed with calcium carbonate in a high speed mixer at motor speed rpm. After that the resin was mixed with modified nanofiller and the mixer was extruded and pelletized in the form of pellets. PROCESSING Processing of Nanocomposites LLDPE, LDPE, PLA and MA-g-PE were obtained in the form of pellets. To remove moisture, LLDPE, LDPE, and PLA were dried at 60 C for 5 hours in an air circulating oven before blending. To prepare the final material, the required amounts of LLDPE and LDPE were taken in weight percentage ratio (wt%); and those of the PLA and MA-g-PE were taken in parts per hundred resin (phr). Four different compositions of the blend of LLDPE/LDPE/PLA/ MA-g-PE [(85/15/10/4), amounts as described above)] were processed with titanate treated nano calcium carbonate loadings of 0.5, 1, 1.5, and 2 phr respectively. Details of the materials mixed to prepare the blends are listed in Table 1 along with the labels for the reinforced blends. Reinforced blends were processed by melt blending for 10 minutes in a co-rotating twin screw extruder; with the screw of 21 mm diameter, and 40:1 L/D ratio. Temperature zone in the extruder barrel to die ranged from 190 to 230 C and at screw speed was maintained 120 RPM. Table 1. Formulations for the nano-caco 3 reinforced blown films of LLDPE/LDPE/PLA/MA-g-PE Sample Sample Formulation LLDPE (Wt%) LDPE (Wt%) PLA (phr) MA-g-PE (phr) Nano- CaCO 3 (phr) A LLDPE/LDPE/PLA/MA-g-PE B LLDPE/LDPE/PLA/MA-g-PE / Nano-CaCO 3 C LLDPE/LDPE/PLA/MA-g-PE / Nano-CaCO 3 D LLDPE/LDPE/PLA/MA-g-PE / Nano-CaCO 3 E LLDPE/LDPE/PLA/MA-g-PE / Nano-CaCO Applied Polymer Composites, Vol. 2, No. 2,

4 Rahul Kumar, Pradeep Upadhyaya and Navin Chand Processing of the Blown Film After proper blending and pelletizing, the blend compositions (A to E) were dried at 70 C for 4 h in an oven before processing a blown film. Blown films were prepared by Konark blown film machine. The dried reinforced blend samples were taken in the hopper, one by one, and the reinforced blown films were processed in the temperature range of 180 C to 200 C at 8 rpm screw speed with take up roll speed maintained at 1 rpm. TESTING AND CHARACTERIZATION Mechanical Testing The tensile tests of the processed reinforced blend films were performed according to ASTM D 882 on a Universal Testing Machine (INSTRON) with the rectangular shaped samples of dimensions 2.5 cm in width and 15 cm in length. Tensile strength of the reinforced blend blown films was calculated in machine direction. Tear strength of the films was calculated as per ASTM D test on (Elmendorf) tear strength tester. The samples were slit down to 6.5x7.5 cm size. Burst strength of the processed films was evaluated according to ASTM D Morphological Studies Surface morphology of the processed reinforced blend films was evaluated by FE-SEM-Carl Zeiss, Supra 40 VP Instrument at 10 kv with gold coated samples at 30 KX resolutions. Optical Testing Haze and Transmittance were determined according to ASTM D Thermal Studies A Perkin Elmer Differential Scanning Calorimeter (DSC) was used to evaluate the thermal behavior of the reinforced blown films material. DSC analysis was carried out from 50 to 200 C at heating rate of 10 C/min, in nitrogen. 88 Applied Polymer Composites, Vol. 2, No. 2, 2014

5 Modified Nano-CaCO 3 Reinforced Ternary Blend Based Blown Films of LLDPE/LDPE/PLA/MA-g-PE RESULTS AND DISCUSSION Mechanical Properties Tensile Strength Table 2 and Figure 1 record the tensile strength of the reinforced blend based films. The addition of nanofillers improves the tensile strength up to 1 phr loadings, and for higher reinforcement amounts the tensile strength decreases. Best results are obtained for the films with 1 phr, that show the tensile strength of 25.4 MPa. Table 2. Mechanical properties of the nano-caco 3 reinforced blown films of LLDPE/LDPE/PLA/MA-g-PE Sample Code Tensile Strength (MPa) Elongation at Break (%) Tear Strength (N/m) Burst Strength (Psi) A B C D E Figure 1. Tensile strength of the nano-caco 3 reinforced blown films of LLDPE/LDPE/ PLA/MA-g-PE Applied Polymer Composites, Vol. 2, No. 2,

6 Rahul Kumar, Pradeep Upadhyaya and Navin Chand Elongation at Break Table 2 and Figure 2 record the elongation at break of the reinforced blend films. Although the elongation at break steadily decreases with increasing amounts of the nano reinforcement, but the film with 0.5 phr loading of nanoreinforcement material exhibits the highest elongation, of 522%. Figure 2. Elongation at break of the nano-caco 3 reinforced blown films of LLDPE/ LDPE/PLA/MA-g-PE Tear Strength Table 2 and Figure 3 record the tear strength of the reinforced blend films. The tear strength steadily decreases with increasing amounts of the nanoreinforcement. Burst Strength Table 2 and Figure 4 record the burst strength of the blend based nanocomposites films; and indicate that the burst strength increases up to 1 phr loadings of nanofiller, and was found to be maximum at 1 phr. Morphology Micrographs of the reinforced blend of LLDPE/LDPE/PLA/MA-g-PE (85/15/10/4) with 0.5, 1, 1.5 and 2 phr of nano calcium carbonate are shown in Figure 5a-d. The 0.5 phr based material (Figure 5a) shows the dispersion of nano-caco 3 in the film. SEM micrograph (Figure 5b) of the blend reinforced 90 Applied Polymer Composites, Vol. 2, No. 2, 2014

7 Modified Nano-CaCO 3 Reinforced Ternary Blend Based Blown Films of LLDPE/LDPE/PLA/MA-g-PE Figure 3. Tear strength of the nano-caco 3 reinforced blown films of LLDPE/LDPE/ PLA/MA-g-PE Figure 4. Burst strength of the nano-caco 3 reinforced blown films of LLDPE/LDPE/ PLA/MA-g-PE with 1 phr shows that the surface of the blown film is finer and the reinforcing nano filler is relatively well dispersed in the matrix. For the composites with 1.5 phr and 2 phr nano-caco 3 the SEM images (Figure 5c,d) show distorted surface and brittleness with improper filler dispersion as compared to the 1 phr Nano-CaCO 3. Applied Polymer Composites, Vol. 2, No. 2,

8 Rahul Kumar, Pradeep Upadhyaya and Navin Chand (a) (b) (c) (d) Figure 5. SEM images of the nano-caco 3 reinforced blown films of LLDPE/LDPE/ PLA/MA-g-PE with (a) 0.5 phr (b) 1.0 phr (c) 1.5 phr and (d) 2.0 phr treated nano- CaCO 3 Formation of Composites These morphology studies also indicate that the improved mechanical properties of the reinforced reinforced, as compared to those of the polymer matrix, are due to the successful reinforcement of the blend by the nanoreinforcement material. Optical Properties Haze Haze is an important optical property of polymeric films. Table 3 and Figure 6 indicate that due to the effect of the nano material used for reinforcement, the haze% of the films increased with increasing nano reinforcement, and minimum haze% of 32.4% has been exhibited by Film-B with 0.5 phr nano reinforcement. 92 Applied Polymer Composites, Vol. 2, No. 2, 2014

9 Modified Nano-CaCO 3 Reinforced Ternary Blend Based Blown Films of LLDPE/LDPE/PLA/MA-g-PE table 3. Optical properties of the nano-caco 3 reinforced blown films of LLDPE/LDPE/PLA/MA-g-PE Sample Code Haze (%) Transmittance (%) A B C D E Figure 6. Haze of the nano-caco 3 reinforced blown films of LLDPE/LDPE/PLA/MA-g-PE Transmittance Transmittance is also an important property of packaging blown films. Table 3 and Figure 7 indicate that due to the effect of the nano material used for reinforcement, and the increase in the haze, transmittance was decreased, also probably because of the nucleating effect of nano-caco 3 as the crystalline structure and the transmittance was blocked by the crystalline morphology of the developed blown film. For the film with the loading of 1 phr of nano- CaCO 3 the haze was found (54.7) and transmittance was (77.4). Applied Polymer Composites, Vol. 2, No. 2,

10 Rahul Kumar, Pradeep Upadhyaya and Navin Chand Figure 7. Transmittance of the nano-caco 3 reinforced blown films of LLDPE/LDPE/ PLA/MA-g-PE Melting Temperature DSC study of the blend based nano-composite films (Table 4) show melting peaks at around 123 to 127 C and also around 154 to 158 C indicating that the nano-reinforcement material does not influence the melting of the films to any great extent. Table 4. Melting of the nano-caco 3 reinforced blown films of LLDPE/LDPE/PLA/MA-g-PE Sample Code Melting Temperature T m ( C) Peak 1 st Peak 2 nd A B C D Conclusions Reinforced ternary blend system of linear low density polyethylene (LLDPE), low density polyethylene (LDPE) and poly lactic acid (PLA) compatibilized 94 Applied Polymer Composites, Vol. 2, No. 2, 2014

11 Modified Nano-CaCO 3 Reinforced Ternary Blend Based Blown Films of LLDPE/LDPE/PLA/MA-g-PE with maleic anhydride grafted polyethylene (MA-g-PE) with chemically modified nano calcium carbonate (Nano-CaCO 3 ) have been successfully processed by twin extrusion and melt blending with 0.5, 1, 1.5 and 2 phr nano reinforcement material. The reinforced blend films show reasonably well dispersed nano reinforcement in the matrix and the interfacial adhesion between the reinforcement and the blend matrix imparts better mechanical properties due to reinforcement. Various compositions show optimum thermal, mechanical and optical properties. References 1. Niknezhad Setareh, Isayev A.I., Journal of Applied Polymer Science, 129 (2013) Singh G., Bhunia H., Rajor A., Jana R.N., and Choudhary V., Journal of Applied Polymer Science, 118 (2010) Monika, Upadhyaya P., Chand N., and Kumar V., Composite Interfaces, 21 (2014) Jamshidian M., Tehrany E.A., Imran M., Jacquot M., and Desobry S., Comprehensive Reviews in Food Science and Food Safety, 9 (2010) Hiroi R., Ray S.S., Okamoto M., and Shiroi T., Macromolecular Rapid Communications, 25 (2004) Dorigato A., Pegoretti A., and Penati A., Express Polymer Letters, 4 (2010) Abdullah M.A.A., Mamat M., Awang M., Eny K., Mubin F.N.A., and Sudin N.H., International Journal of Technology, 4 (2013) Hajian M., Koohmareh G.A., and Mostaghasi A., International Journal of Polymer Science, (2011) Article ID doi: /2011/ Wang W. and Qi L., International Journal of Chemistry, 2 (2010) Applied Polymer Composites, Vol. 2, No. 2,

12 Rahul Kumar, Pradeep Upadhyaya and Navin Chand 96 Applied Polymer Composites, Vol. 2, No. 2, 2014