Thermoplastic elastomers are a special class of polymeric materials that combine the propertiesof thermo plasticity during processing and rubber-like behaviour in service. They can beprocessed in conventional plastic processing equipment, such as twin screw extruders, internalbatch mixers, extruders and injection moulding machine, but exhibit vulcanized rubber likeultimate properties (i.e. long-range reversible extensibility) immediately on cooling.Dynamically vulcanized thermoplastic fibrous composites based on melt processed hybridethylene-propylene diene rubber (EPDM)/maleic anhydride (MA) grafting and polypropylene(PP) with coir fibers were prepared. Coir fiber acts as a nucleating agent for polypropylenecrystallization; they also form physical interlocking between EPDM/Polypropylene blends whichserve the function of compatibalization along with EPDM – g – Maleic anhydride. Results fromRubber Process Analyzer, Mechanical Analysis, Scanning Electron Microscope, DifferentialScanning Calorimetery, reflect upon the microstructure developed during dynamic cross linking.The coir fiber forms well dispersed structures in the EPDM/PP / EPDM-g-MA thermoplasticvulcanizates. The EPDM/PP TPV fiber composites show a matrix-disperse type of morphologyin which the cross linked EPDM particles appear in the form of agglomerates covered by a layerof PP coir fiber composites. This has been assigned to the formation of a coir fiber networkstructure by the layer of coir fiber PP covered EPDM rubber particles

Abitha, V. K.

D, Chandresh

Rajkumar, K.

Vasudeo  Rane, A.

English

Revues Scientifiques Marocaines

V.K.Abitha & al. / Mor. J. Chem. 3 N°3 (2015) 573-581 573     STUDIES IN USE OF COIR FIBER IN BLEND OF ETHYLENE PROPYLENE DIENE RUBBER AND POLYPROPYLENE  V.K.Abitha (a), Ajay.V.Rane (b) *, K.Rajkumar(c), D.Chandresh (c)  (a) Cochin University of Science and Technology, Department of Polymer Science and Rubber Technology, Kerala, India  (b) Institute of Chemical Technology, Centre for Green Technology, Department of Polymer and Surface Engineering, Mumbai, Maharashtra, India (c) Indian Rubbers Manufacturers Research Association, Thane, India   *Corresponding author. E-mail : ajayrane2008@gmail.com  Received  03 April 2015, Revised 10 May 2015, Accepted 26 May 2015.  Abstract   Thermoplastic elastomers are a special class of polymeric materials that combine the properties of thermo plasticity during processing and rubber-like behaviour in service. They can be processed in conventional plastic processing equipment, such as twin screw extruders, internal batch mixers, extruders and injection moulding machine, but exhibit vulcanized rubber like ultimate properties (i.e. long-range reversible extensibility) immediately on cooling. Dynamically vulcanized thermoplastic fibrous composites based on melt processed hybrid ethylene-propylene diene rubber (EPDM)/maleic anhydride (MA) grafting and polypropylene (PP) with coir fibers were prepared. Coir fiber acts as a nucleating agent for polypropylene crystallization; they also form physical interlocking between EPDM/Polypropylene blends which serve the function of compatibalization along with EPDM – g – Maleic anhydride.  Results from Rubber Process Analyzer, Mechanical Analysis, Scanning Electron Microscope, Differential Scanning Calorimetery, reflect upon the microstructure developed during dynamic cross linking. The coir fiber forms well dispersed structures in the EPDM/PP / EPDM-g-MA thermoplastic vulcanizates. The EPDM/PP TPV  fiber composites show a matrix-disperse type of morphology in which the cross linked EPDM particles appear in the form of agglomerates covered by a layer of PP coir fiber composites. This has been assigned to the formation of a coir fiber network structure by the layer of coir fiber PP covered EPDM rubber particles.  Keywords: Composites, Coir fiber, Polypropylene, EPDM    V.K.Abitha & al. / Mor. J. Chem. 3 N°3 (2015) 573-581 574  1. Introduction  Generally any material consisting of two or more components with different properties and distinct boundaries between the components can be referred to as a composite material. Moreover, the idea of combining several components to produce a material with properties that are not attainable with the individual components has been used by man for thousands of years. There are two groups of composites the first group comprises composites that are known as “filled materials”. The main feature of these materials is the existence of some basic or matrix material whose properties are improved by filling it with some particles and second group involves composites that are called “reinforced materials”. The basic components of these materials are long and thin fibres possessing high strength and stiffness. Filler (particulate or thin fibers) is a solid material capable of changing the physical and chemical properties of materials by surface interaction or its lack thereof and by its own physical characteristics. Carbon fibres were a natural step aiming at a rise of fiber’s stiffness the proper level of which was not exhibited by glass fibres. Modern high-modulus carbon fibres demonstrate modulus that is by the factor of about four higher than the modulus of steel, while the fibre density is by the same factor lower. Though first carbon fibres had lower strength than glass fibres, modern high strength fibres demonstrate tensile strength that is 40% higher than the strength of the best glass fibres, while the density of carbon fibres is 30% less. High stiffness means that material exhibits low deformation under loading. However, saying that stiffness is an important property we do not mean that it should be necessarily high. Ability of structure to have controlled deformation can be also important. Shortage of material strength results in uncontrolled compliance, i.e., in failure after which a structure does not exist anymore. Usually, we need to have as high strength as possible. Thus, without controlled stiffness and strength the structure cannot exist [1]. Rubber when used to plasticize a thermoplastic is accomplished by dispersing microscopic particles of rubber, into thermoplastic which is a continuous phase, where dispersed rubber acts as a minute shock absorbers and enhances the toughness of the thermoplastic along with mechanical strength and offers a wide range of physical properties and applications [2]. EPDM and PP have similarity in structure due to presence of common polypropylene structure. In spite of structural similarity however EPDM is not compatible with PP. The EPDM phase exists as separate particles in PP matrix due to stratification, segregation and phase inversion. The incompatibility of the EPDM/PP blend is signified by poor interphase adhesion, to improve the compatibility of the EPDM/PP blend, various compatibilizers have been prepared and incorporated into the EPDM/PP blend [3]. Filler addition is the simplest way to modify the properties of the base materials. Addition of filler at an optimum level increases the physical properties of the blend but excess addition of filler acts as diluents and causes degradation in properties of the blend formed [4]. Filler increases the physical properties, but some of the properties of the filler, like particle size, shape, volume fraction and surface are to be considered while selecting filler for a particular application [5]. Increasing concern about global warming and depleting petroleum reserves have made scientists to focus more on the use of natural fibers such as bagasse, coir, sisal, jute etc. This has resulted in creation of more awareness about the use of natural fibers based materials mainly composites. Natural fibers have received much more attention than ever before from the research community all over the world. The advantages of natural fibers over traditional reinforcing materials such as glass fibers, talc, and mica are acceptable specific strength properties, low cost, low density, nonabrasivity, good thermal properties, enhanced energy recovery and biodegradability, and recyclable in nature [6]. Natural fibers have an outstanding potential as reinforcement V.K.Abitha & al. / Mor. J. Chem. 3 N°3 (2015) 573-581 575  in thermoplastic. Among various natural fibers, both coir and jute fibers are widely available, cheap, relatively water – proof and is resistant to damage by salt water. Coir fibers have an outstanding potential as reinforcement in thermoplastics. Commonly used thermoplastics are Polyethylene, Polypropylene, Polystyrene, Nylon etc [7]. These composites are used in automotive components, building materials. This work discusses the use of coir fiber and its current status of research.  2. Experimental Section   2.1. Materials The polypropylene (PP) used in this study was supplied by Reliance Industries Ltd. ethylene propylene diene monomer Rubber (EPDM) was obtained from DSM Elastomers, Netherlands. maleic anhydride (MA) was obtained from the Aldrich Chemical Company. Coir Fiber was procured from Rubber Park, Ernakulum. Dicumyl peroxide (DCP) and triallyl cyanurate (TAC) were obtained by Arkema Inc, EPDM grafted Maleic Anhydride was prepared by reactive process.   2.2. Preparation of EPDM-grafted-Maleic Anhydride Brabender was used for the reactive compatibalization i.e. grafting of Maleic Anhydride on EPDM. EPDM was charged in the chamber and heated at 130ºC for 5 minutes. Maleic anhydride and Dicumyl peroxide were added and mixed at the same temperature. After completing the reaction, the reaction mixture was dissolved in Xylene, and then the product was precipitated by pouring it into excess acetone with stirring. After removing unreacted Maleic Anhydride, the product was filtered. The purification procedure was repeated till removal of unreacted maleic anhydride and, the precipitate was finally dried in a vacuum at 80ºC for 24 hours [8].  2.3. Preparation of fiber composites  Polypropylene coir fiber master batch was prepared in a Brabender Plasti-corder, having a mixing chamber volume of 350 cm³ at a temperature of 180°C and rotor speed of 80 rpm. The fill factor of the chamber was maintained at 0.80.  Table 1: Formulation for 90/10(A) and 80/20(B) EPDM: Polypropylene with variable dosage of Coir fiber (‘C’ refers to Coir fiber and digit refers to loading of Coir fiber) BATCH NO  CA0 CA2 CA4 CA6 CB0 CB2 CB4 CB6 I N G R E D I E N T S  EPDM 90 90 90 90 80 80 80 80 PP 10 10 10 10 20 20 20 20 Maleic Anhydride 6 6 6 6 6 6 6 6 Coir Fiber 0 2 4 6 0 2 4 6 DCP 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 TAC 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 V.K.Abitha & al. / Mor. J. Chem. 3 N°3 (2015) 573-581 576  The prepared Polypropylene coir fiber masterbatch was then melt blended with prepared EPDM-g-MA at 180°C. At final stages of mixing cross-linking agent Triallyl Cyanurate was added to affect dynamic vulcanization.  Immediately after mixing, the molten mass was taken out from the mixer and while still hot, passed through the cold two-roll mill to chill it and sheet it to about 2 mm thick. The sheet was then cut and press moulded for 5 minutes in a hydraulic press at 190C, under 5 MPa pressure. The sheet was then cooled down to room temperature still under pressure. The test specimens were die-cut from the compression molded sheet and used for measuring mechanical properties after 24 hours of conditioning at room temperature. Similarly the other batches with varying comapatibilizer dosage were carried out to prepare coir fiber composites.  3. Results and Discussion  3.1. Rubber Process Analyzer (RPA) It is the most important characterization to be carried out to study melt viscosity behaviour and processability of the rubber compounds. Coir fiber composites were tested for its melt viscosity and processability, with RPA for dynamic moduli over a wide range of strain amplitude and frequency. It is true that a sinusoidal strain when imposed on a linear viscoelastic solid, a sinusoidal stress responses generates and depend only on temperature and frequency and are independent of all type of deformation. But it is not true for thermoplastic elastomeric composites and depends on dynamic strain amplitude.  Figure 1: RPA results for 90:10 Coir fiber composites  The graphical trend for G’ versus Frequency shows that the storage modulus G’ increases as the frequency increases, but it can also be observed that as the coir fiber concentration increases in the blend, the elastic modulus increases which is prominent at the lower frequencies, but at higher frequencies it remains same for all concentration of coir fiber. The graphical trend for G’ versus Strain shows that the elastic modulus does not change up to a certain strain level beyond which strain decreases at higher levels. The dependence of dynamic modulus G' of the fiber composites with 80:20 blend ratio, on the frequency and strain are depicted in the below graphs, V.K.Abitha & al. / Mor. J. Chem. 3 N°3 (2015) 573-581 577   Figure 2: RPA results for 80:20 Coir fiber composites Rubber Processing Analyzer study states that the storage modulus G’ increases with increase in coir fiber loading as well as frequency. In fact the storage modulus value does not change much at lower strain levels, but as the strain level increases the G’ decreases.   3.2. Mechanical Properties  The tensile strength, modulus, hardness, tear strength and elongation at break of fiber composites with polymer blend ratio of EPDM/Polypropylene 90:10 and 80:20 with change in the concentration of coir fiber – 0, 2, 4, 6 phr are depicted in the below table 2.   Table 2: Physical Properties of 90/10(A) and 80/20(B) EPDM: Polypropylene with variable dosage of Coir fiber (‘C’ refers to Coir fiber and digit refers to loading of Coir fiber) Sample code Tensile strength (MPa) Elongation at break (%) 100% modulus (MPa) 200% modulus (MPa) Tear strength (N/mm) Hardness (shore A) CA0 2.4 350 1.1 1.2 10.9 42 CA2 2.7 310 1.2 1.4 11.4 45 CA4 2.9 280 1.3 1.6 12 48 CA6 3.2 220 1.7 ---- 14 50 CB0 2.6 200 2.7 ---- 17.9 53 CB2 2.9 140 2.8 ---- 18.5 57 CB4 3.0 120 2.9 ---- 19.3 61 CB6 3.4 110 3.1 ---- 20.4 63  Table 2 reveals that the mechanical properties such as tensile strength tear strength and modulus shows rise with increasing dose of coir fiber in to the blend matrix. Hardness also increases proportionally with increasing dose of coir fiber in the blend vulcanizates. In Table 3, no deterioration in properties was found after hot air ageing at V.K.Abitha & al. / Mor. J. Chem. 3 N°3 (2015) 573-581 578  100°C for 24hrs for the fiber composites rather an increase in the tensile strength was observed in ‘A’ group (90:10) series was observed to impart higher tensile strength than that of ‘B’ group (80:20) series is due to more number of elastomeric chains getting cross linked. Table 3 reflects the change in the mechanical properties after accelerated ageing test, carried out at 100°C for 24 hours.  Table 3: Change in Physical properties after hot air oven ageing at 100° C for 24 hrs Sample code Change in Tensile strength (MPa) Change in Elongation at break (%) Change in hardness (Points) CA0 +29 +35 +3 CA2 +27 +15 +2 CA4 +14 +10 +3 CA6 +7 +10 +2 CB0 +23 +20 +2 CB2 +15 +10 +3 CB4 +18 +9 +2 CB6 +26 +5 +3  3.3. Morphological Analysis  The SEM images of fractured fiber composites samples based on EPDM/Polypropylene (90:10) thermoplastic elastomer with and without coir fiber are shown in Figure 3. It is visible that the rubber particles are dispersed throughout the polypropylene matrix in the form of aggregates and the size of rubber particles is less than 2 μm in the unfilled thermoplastic elastomer sample as shown in Figure 3 (a), because the size of the dispersed rubber phase in unfilled EPDM/Polypropylene blends depends on the interfacial interactions between two phases. It should also be noted that the cross linked rubber particles are enclosed by a layer of polypropylene Figure 3 (b) shows that the size of rubber particles has been increased to 10 μm by the introduction of the coir fibre. Initially, the coir fibre cannot penetrate into the rubber phase, but after adding curing agent DCP/TAC, the rubber phase become more polar. Therefore, it is possible that some coir fibre goes to EPDM phase before the curing cycle ends. Hence there is change in the viscosity ratio between the two phases, and consequently, the size of the rubber phase increases. The adhesion of coir fiber in polymeric phase of EPDM/PP can be clearly seen in the figure 3, (b) (c) and (d) due to presence of maleic anhydride.   V.K.Abitha & al. / Mor. J. Chem. 3 N°3 (2015) 573-581 579    (a) 0 phr (b) 2 phr   (c) 4 phr (d) 6 phr Figure 3: SEM images of ternary composites with 90/10 polymer blend ratio and 0,2,4,6 phr  3.4. Differential Scanning Calorimetery The DSC curve for different blend ratio of EPDM/Polypropylene thermoplastic elastomers without coir fiber and with 2, 4 & 6 phr coir fiber are shown in Figure 4 and 5 for blend ratios 90:10, 80:20 respectively. The area under peak is heat of fusion for the fiber composites.  Figure 4: DSC heating curve for EPDM/Polypropylene (90/10) Ternary composites  V.K.Abitha & al. / Mor. J. Chem. 3 N°3 (2015) 573-581 580   Figure 5: DSC heating curve for EPDM/Polypropylene (80/20) Ternary composites  Table 4: Melting temperature and % of crystallinity of ternary composites  CA0 CA2 CA4 CA6 CB0 CB2 CB4 CB6 Melting Temperature (°C) 162 162.26 162.76 163 162.10 163.87 163.99 164.10 Degree of Crystallinity (%) 1.66 2.67 3.43 3.72 4.36 6.11 6.42 6.93  The melting point of polypropylene in ternary composites is essentially same as that of polypropylene in the blend at different ratio of EPDM/Polypropylene (90/10), (80/20). However, increase of coir fiber loading from 0 to 6phr also increases melting temperature from 162°C to 163°C for EPDM/Polypropylene (90/10), 162.1°C to 164.10°C for EPDM/Polypropylene (80/20). The coir fiber appears to have prejudiced the spherulite structure of polypropylene. The presence of high coir fiber loading has completely introverted spherulite growth in polypropylene.   Conclusion The compatibility between coir fiber and EPDM/Polypropylene matrix is significantly improved by the addition of maleic anhydride as a compatibilizer. Existence of compatibilizer induced even more intercalation of coir fiber. Accordingly the tensile strength and modulus of coir fiber filled EPDM/Polypropylene composites with maleic anhydride is better than those of untreated composites. SEM studies indicate that the interfacial adhesion between coir fiber and EPDM/Polypropylene matrix is improved with the presence of maleic anhydride. Crystallinity of composites was relatively lower than the blend suggesting that coir fiber inhibits the growth of spherulite polypropylene, The EPDM/Polypropylene blend without coir fiber showed a two-phase morphology with EPDM as dispersed phase in irregular-shaped domains. The EPDM domains turned to more spherical shape and much smaller in size as well in presence of coir fiber. Rubber Process Analyzer study shows that storage modulus (G’) increases with frequency rise and is higher at higher concentration of coir fibres in composites. But, in strain (%), the storage modulus value is higher at low strain rate, decreasing rapidly at higher strain rates. Scanning Electron Microscopy shows that reinforcement in the interfacial interaction V.K.Abitha & al. / Mor. J. Chem. 3 N°3 (2015) 573-581 581  between the polypropylene matrix and cross linked rubber particles agglomerates was evidenced by the ternary composites compared with the similar but unfilled samples. This was observed that slightly reduction of cross linked rubber particle size with the presence of coir fiber concentration. Increase in coir fiber concentration significantly improves mechanical properties such as tensile strength, modulus, tear strength and hardness.  Acknowledgement    Authors wish to thank, Dr P Thavamani, Former Director and management staff of Indian Rubbers Manufacturers Research Association for their help in regards to technical information related to the current research work.  References [1] Valery V, Vasiliev & Evgeny V Morozov, Elsevier Sci Ltd, 1 (2001) 9-10 [2] A.V.Rane, V.K.Abitha, J Mater Env Sci, 6 (2015) 60-69 [3] Kim B. C., Hwang S. S., Lim K. Y., Yoon K. J. J. Appl. Polym. Sci. 78 (2000) 1267-1274 [4] Takahashi S., Goldberg H. A., Feeney C. A., Karim D .P., Farrell M., O’Leary K., Paul D. R., Polymer 47 (2006) 3083-3093 [5] Aroon V Shenoy, Kluwer Academic Publishers, Dordrecht/Boston/London, Rheology of Filled Polymer System, (1999) 1-53 [6] Avinash R Pai, R N Jagtap, J Mater Env Sci, 6 (2015) 902-917 [7] V.K.Abitha, A.V.Rane, Moro J Chem, 3 (2015) 298-305 [8] Doo Wan Kang, Bum Jin Kim, Dae Sup Shim, J Indus Engg Chem 6 (2000) 270 – 275  

Studies in use of coir fiber in blend of ethylene Propylene diene Rubber and Polypropylene

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Studies in use of coir fiber in blend of ethylene Propylene diene Rubber and Polypropylene

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