Bamboo Fibre-reinforced Self-compatibilizing Functionalized Polypropylene Composites by Palsule Process

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1 Bamboo Fibre-reinforced Self-compatibilizing Functionalized Polypropylene Composites by Palsule Process Bamboo Fibre-reinforced Self-compatibilizing Functionalized Polypropylene Composites by Palsule Process Kishor Biswas and Sanjay Palsule* Department of Polymer & Process Engineering, Indian Institute of Technology, IIT-R SRE Campus, Paper Mill Road, Saharanpur India Received: 4 June 2015, Accepted: 11 November 2015 SUMMARY Bamboo fibre (BMBF) reinforced chemically functionalized polypropylene (CF-PP) composites (BMBF/ CF-PP) with in-situ fibre/matrix interfacial adhesion have been processed by Palsule process without using any compatibilizer and without any fibre treatment by co-rotating twin screw extruder and injection moulding machine using raw, untreated bamboo fibres as reinforcement and chemically functionalized polypropylene (i.e., polypropylene grafted with 1.8% maleic anhydride) as the polymer matrix. Mechanical properties of the 10/90, 20/80 have been found to be higher than those of the CF-PP matrix and increase with increasing amounts of reinforcing BMBF in the composites. In-situ fibre/matrix interfacial adhesion resulting in the formation of BMBF/CFPP composites has been established by Field Emission Scanning Electron Micrograph (FE-SEM) and Fourier Transform Infra-Red (FTIR) spectroscopy. 1. Introduction Natural fibre reinforced polymeric composites are offering technological, economic and environmental advantages. Technological advantages of natural fibre / polymer composites include their acceptable specific strength and specific stiffness, and good thermal and physical properties. Environmental advantages of natural fibre / polymer composites include, enhanced energy recovery, use of renewable and biodegradable reinforcing natural fibres, reduction in dependence on non-renewable sources, and reduction in pollutants and greenhouse gas emissions. Low cost, promotion of farmers engaged in cultivating natural fibres and support to agricultural economy are the economic advantages of natural fibre / polymer composites. Several natural fibre reinforced polymer composites have been developed and the subject of natural fibre / polymer composites has been reviewed recently 1. Bamboo plants are giant, fast-growing grasses that have woody stems. Their characteristics depend on their growth and size; and on climate, soil, and moisture conditions in which the fibres are grown. Bamboo fibres are low cost and offer good mechanical, thermal and physical properties. The main constituents of plant based natural fibres are cellulose, hemicellulose and lignin which may vary from fibre to fibre. Literature reports that bamboo fibres also contain lignin and cellulose 2. Bamboo fibres have been used as reinforcement materials for polymer composites, and the subject has been reviewed 3. Fibre/matrix interfacial adhesion governs properties of natural fibre/polymer composites. This interfacial adhesion depends on the chemical nature and properties of the matrix polymer and of the reinforcing natural fibres constituting the composite. Hydrophilic natural fibres have poor interfacial adhesion with hydrophobic polymers in natural fibre / polymer composites and that limits load transfer from the matrix to the fibre and results in poor mechanical properties of natural fibre / polymer composites. The following three processes have been used to improve the fibre / matrix interfacial adhesion in natural fibre / polymer composites: (i) Fibre modification process based on chemical and/or physical treatment of natural fibres; (ii) Compatibilizer process that uses a compatibilizer or a coupling agent; and (iii) Palsule process based on functionalized self compatibilizing polymer as a matrix in place of a polyolefin 4-8. * macrofpt@gmail.com, macrofpt@iitr.ernet.in. Telephone no. (+91) Smithers Information Ltd., 2016 Several bamboo fibre reinforced polymer composites have been Polymers & Polymer Composites, Vol. 24, No. 8,

2 Kishor Biswas and Sanjay Palsule developed by the first process the fibre treatment process. For example, bamboo fibres have been treated with steam 9 ; silane coupling agents 10,11, alkali 12, urushiol-ferric 13 lauryl methacrylate grafting 14 or sodium metaperiodate 15 to develop treated bamboo fibre reinforced polymer composites. Following the second process - compatibilizers process - several bamboo fibre reinforced polypropylene composites have been developed using compatibilizers like, maleic anhydride grafted polypropylene Palsule et al. 4-8, for the first time, demonstrated that the use of a self compatibilizing chemically functionalized maleic anhydride grafted polyolefin as a matrix, in place of polyolefin, eliminates the need of any compatibilizer or any fibre treatment to develop natural fibre / functionalized polyolefin composites. A natural fibre reinforced chemically functionalized polyolefin composite, developed by Palsule process, has in-situ fibre/matrix interfacial adhesion and offers good overall properties. The in-situ fibre/ matrix interfacial adhesion in natural fibre / polymer composites developed by Palsule process results from esterification reaction and hydrogen bonding between components of natural fibres and maleic anhydride grafted polyolefin. No reports are available on bamboo fibre reinforced self compatibilizing functionalized polypropylene composites by Palsule process. Accordingly, this study aims to develop bamboo fibre reinforced functionalized self compatibilizing polypropylene composites by Palsule process, using 1.8% maleic anhydride grafted polypropylene as matrix. However, it has been noted that Qui et al have developed crystalline cellulose particles reinforced maleic anhydride grafted polypropylene (MAPP) based particulate (not fibrous) composites; but the report does not explain the mechanism of in-situ fibre/ matrix interfacial adhesion generated by interactions between functional groups of natural fibre (i.e. -OH of cellulose, hemicelluloses and lignin) and functional groups of maleic anhydride grafted functionalized polyolefin, as Qui et.al have not used natural fibre as reinforcement. A few bamboo fibre reinforced maleic anhydride grafted polypropylene composites have been reported in literature, however, none of these composites have been developed by Palsule process. For example, treated bamboo fibre reinforced maleic anhydride grafted polypropylene composites have been developed by fibre treatment process wherein bamboo fibres have been treated with water or ethanol 22 ; chitosan or detergent 23 ; or silane 24, or organo coupling agent or plasma 25. Thus, these treated bamboo fibre reinforced maleic anhydride grafted composites have been developed by fibre treatment process, and not Palsule process that uses untreated bamboo or any other untreated natural fibre to develop natural fibre / polymer composites. Unidirectional untreated bamboo fibre / maleic anhydride grafted polypropylene composites, prepared as reference for another composite, have been investigated 23 for longitudinal and transverse flexural properties. In these composites 23, fibres are unidirectional and aligned, whereas composites processed by Palsule process are a quasi-isotropic with fibres distributed across the matrix. Palsule process generates in-situ fibre/matrix interfacial adhesion in the composites, however, the study in reference 23 does not report tensile mechanical properties and in-situ fibre/matrix interfacial adhesion between untreated bamboo fibre and maleic anhydride grafted polypropylene in the composites. Another study 26 on mixtures of untreated bamboo fibre and maleic anhydride grafted polypropylene has been limited to the effect of bamboo fibre on morphology, melting temperature, crystallization temperature, and nucleation of MAPP. This study 26 does not investigate mechanical properties and the basic parameter of improved mechanical properties of composites relative to matrix, and therefore does not establish composite formation. Palsule process generates in-situ fibre/ matrix interfacial adhesion in the composites, however, the study under reference 26 also does not report in-situ fibre/matrix interfacial adhesion for the untreated bamboo fibre with maleic anhydride grafted polypropylene in the mixtures/composites. In view of above literature survey, this study develops 10/90, 20/80 and 30/70 untreated bamboo fibre (BMBF) reinforced functionalized self compatibilizing polypropylene (CF- PP) composites [i.e. 10/90, 20/80 and 30/70 BMBF/CF-PP composites] by Palsule process with in-situ fibre/matrix interfacial adhesion - without any compatibilizer and without any fibre treatment. In this study, formation of BMBF/CFPP composites is explained on the basis of higher mechanical properties of the 10/90, 20/80, 30/70 BMBF/CFPP composites, as compared to those of the CF-PP matrix, and increasing mechanical properties of the composites with increasing amounts of bamboo fibres in the BMBF/ CFPP composite compositions. The mechanism of in-situ fibre/matrix interfacial adhesion by esterification reaction and hydrogen bonding between functional groups of bamboo fibre and of maleic anhydride grafted functionalized polyolefin resulting in the formation of the BMBF/CFPP composites has been explained by SEM and FTIR studies. 2. Materials 2.1 Fibres Reinforcing bamboo fibres of mm average diameter were obtained from the local market in raw form and were chopped to 2-4 mm length. Bamboo fibres were used, as 664 Polymers & Polymer Composites, Vol. 24, No. 8, 2016

3 Bamboo Fibre-reinforced Self-compatibilizing Functionalized Polypropylene Composites by Palsule Process received, and no fibre treatment was performed. Bamboo fibres have been termed as BMBF. 2.2 Matrix Self compatibilizing chemically functionalized polypropylene, termed as CF-PP with 1.8% maleic anhydride grafted on it - used as matrix - has been obtained commercially from Pluss Polymer Pvt. Ltd., India as its product - OPTIM P-425, Series 400. CF-PP is available as off white to light yellow coloured free flowing granules of reported density of 0.91 gm/ml, melting temperature of 161 o C and MFI (190 o C, 2.16 kg) of 110 g/10 min. No compatibilizer has been used in this study. 2.3 Processing by Extrusion and Compounding Self compatibilizing chemically functionalized polypropylene, (CF-PP) matrix and 2-4 mm short reinforcing bamboo fibres (BMBF) were dried in hot air oven at 60 o C for one day, and then at 80 o C for 4 hours, prior to extrusion to remove moisture. Table 1 records the formulations of the BMBF/ CF-PP composites developed in this study. Calculated amounts of BMBF and CF-PP were mixed manually with a view to finally obtain 10/90, 20/80. Mixtures with appropriate amounts of BMBF and CF-PP were then feed into the hopper of the co-rotating twin screw extruder [Specific Engineering & Automats (Model ZV 20α)]. The screw speed of the co-rotating twin screw extruder was set at 145 rpm. The temperature profile for 6 different zones in the extruder was varied from 165 C to 195 C. In particular, the temperature profiles of the various zones of the extruder for processing BMBF/CF- PP composites were 165 o C 175 o C 185 o C 190 o C 195 o C 190 o C. 2.4 Sample Preparation by Injection Moulding The extruded composite compositions, termed as 10/90, 20/80 and 30/70 BMBF/CF-PP composites, were cooled in water and were then pelletized in a pelletizer to obtain granules that were dried in hot air oven at 70 o C for overnight, and were then used to mould test specimens. To process samples for testing and characterization as per ASTM standards, extruded and pelletized 10/90, 20/80, 30/70 BMBF/CF-PP composite granules were moulded by Injection Moulding Machine [Electronica Endura 90] with the feed zone temperature of 160 o C and nozzle temperature of 190 o C. 3. Testing and Characterization 3.1 Tensile Properties Tensile tests of the CF-PP and the processed 10/90, 20/80 and 30/70 BMBF/CF-PP composites have been performed as per ASTM D 638 standard at room temperature on a Universal Testing Machine, (Model 3365, INSTRON 5KN Capacity) with crosshead speed of 50 mm/min with five samples of CF-PP matrix, and five samples of each of the 10/90, 20/80, 30/70 BMBF/CF-PP composites. Table 1. Formulations of bamboo fibre reinforced functionalized polypropylene (BMBF/CF-PP) composites (in weight %) BMBF/CF-PP Composites Bamboo Fibre (BMBF) wt.% Chemically Functionalized Polypropylene (CF-PP) wt.% 0/ / / / Flexural Properties Flexural tests of the CF-PP and of the processed 10/90, 20/80 and 30/70 BMBF/CF-PP composites have been performed as per ASTM D 790 standard at room temperature on a Universal Testing Machine, (Model 3365, INSTRON 5KN Capacity) with speed of 1.36 mm/min with five samples of CF-PP matrix, and five samples of each of the 10/90, 20/80, 30/70 BMBF/CF- PP composites. 3.3 Impact Strength Charpy and Izod impact strengths of CFPP and the processed BMBF/CFPP composites have been measured at room temperature according to ASTM D 6110 and ASTM D 256 standards respectively at room temperature by an impact tester (Tinius Olsen, Model Impact 104. USA). 3.4 Morphology Morphology of raw bamboo fibre, CF-PP and 10/90, 20/80 and 30/70 BMBF/CF-PP composites has been investigated by Field Emission Scanning Electron Microscope (FE- SEM) [Model Mira3 Tescan] using an acceleration voltage of 7.5 kv. The samples coated with a thin layer of gold, were mounted on the Al stub. 3.5 Fourier Transform Infrared Spectroscopy for Fibre/Matrix Interfacial Interactions FTIR spectra of the PP (used as a reference) CF-PP, and of only one composite composition - the 20/80 BMBF/CF-PP composite have been obtained using Perkin Elmer Spectrum Two FTIR Spectrophotometer - as all other composite compositions are expected to give similar results. PP, CFPP and 20/80 BMBF/CF-PP composite samples were ground using Retsch -MM 400 mixer mill apparatus; and mixed with approximately 75 mg of dried potassium bromide (KBr) powder using mortar pestle and then were pressed in the hydraulic Polymers & Polymer Composites, Vol. 24, No. 8,

4 Kishor Biswas and Sanjay Palsule press to obtain thin transparent disc for recording the FTIR spectra. The scanning range of FTIR was between 4000 cm -1 and 400 cm -1 and a resolution of 4 cm Results and Discussion the tensile strength of 10/90, 20/80 are higher by 10%, 41% and 48% respectively. 4.2 Flexural Properties The flexural stress v/s strain curves of the CF-PP matrix and 10/90, 20/80 are shown in Figure 3. Table 3 and Figure 4 record the flexural modulus and flexural strength values, along with deviations in values. Table 3 and Figure 4 indicate that in absolute terms, the 10/90, 20/80 and 30/70 BMBF/CF-PP composites 4.1 Tensile Properties The tensile stress v/s strain curves of the CF-PP matrix and of the 10/90, 20/80 and 30/70 BMBF/CF-PP composites are shown in Figure 1. The tensile modulus and the tensile strength of CF-PP matrix, and of the 10/90, 20/80 and 30/70 BMBF/CF- PP composites and the deviations in their values have been recorded in the Table 2 and Figure 2. Table 2 and Figure 2 indicate that in absolute terms, the 10/90, 20/80 respectively have a tensile modulus of 1.89 GPa, 2.34 GPa and 2.82 GPa that are higher than the tensile modulus of 1.43 GPa of the CF-PP matrix. In relative terms, compared to the tensile modulus of the CF-PP matrix, the tensile modulus of 10/90, 20/80 are higher by 32%, 64% and 97% respectively. Figure 1. Tensile stress strain curve for CF-PP and BMBF/CFPP composites Figure 2. Tensile modulus and tensile strength of CFPP and BMBF/CFPP composites Similarly, Table 2 and Figure 2 indicate that in absolute terms, the 10/90, 20/80 and 30/70 BMBF/CF-PP composites respectively have tensile strength of MPa, MPa and MPa; that are higher than the tensile strength of MPa of the CF-PP. In relative terms, compared to the tensile strength of the CF-PP matrix, Table 2. Tensile properties of CF-PP and BMBF/CF-PP composites Sample Tensile Modulus (GPa) Standard Deviation % Increase in Tensile Modulus Tensile Strength (MPa) Standard Deviation % Increase in Tensile Strength CF-PP /90 BMBF/CF-PP % % 20/80 BMBF/CF-PP % % 30/70 BMBF/CF-PP % % 666 Polymers & Polymer Composites, Vol. 24, No. 8, 2016

5 Bamboo Fibre-reinforced Self-compatibilizing Functionalized Polypropylene Composites by Palsule Process respectively have a flexural modulus of 6.03 GPa, 8.59 and GPa; that are higher than the flexural modulus of 3.53 GPa of the CF-PP matrix. In relative terms, compared to the flexural modulus of CF-PP matrix, the flexural modulus of the 10/90, 20/80 are higher by 71%, 144% and 202% respectively. Similarly, Table 3 and Figure 4 indicate that in absolute terms, 10/90, 20/80 and 30/70 BMBF/ CF-PP composites respectively have a flexural strength of MPa, MPa and MPa; that are higher than the flexural strength of MPa of the CF-PP matrix. In relative terms, compared to the flexural strength of CF-PP matrix, the flexural strength of 10/90, 20/80 and 30/70 BMBF/ CF-PP composites are higher by 9%, 33% and 45% respectively. 4.4 Charpy Impact Strength Table 4 and Figure 5 record the Charpy impact strength of CF-PP and of the 10/90, 20/80 and 30/70 BMBF/CF-PP composites, with deviations in values. Table 4 and Figure 5 indicate that in absolute terms, 10/90, 20/80 and 30/70 BMBF/CF-PP composites respectively have Charpy impact strength of J/m, J/m and J/m; that are higher than the Charpy impact strength of J/m of the CF-PP. In relative terms, as the amount of bamboo fibres in the BMBF/CF-PP Figure 3. Flexural stress strain curve for CFPP and BMBF/CFPP composites 4.3 Izod Impact Strength Table 4 and Figure 5 record the Izod impact strength of CF-PP and of the 10/90, 20/80 and 30/70 BMBF/CF-PP composites with deviations in values. Table 4 and Figure 5 indicate that in absolute terms, the 10/90, 20/80 respectively have Izod impact strength of J/m, J/m and J/m; that are higher than the Izod impact strength of J/m of the CF-PP. In relative terms, as the amount of bamboo fibres in the BMBF/CF-PP composites increases to 10%, 20% and 30%, respectively, the Izod impact strength of the resulting 10/90, 20/80 increases by 31%, 68% and 124%, respectively, compared to that of the CF-PP matrix. Figure 4. Flexural modulus and flexural strength of CFPP and BMBF/CFPP composites Table 3. Flexural properties of CF-PP and BMBF/CF-PP composites Sample Flexural Modulus (GPa) Standard Deviation % Increase in Flexural Modulus Flexural Strength (MPa) Standard Deviation % Increase in Flexural Strength CF-PP /90 BMBF/CF-PP % % 20/80 BMBF/CF-PP % % 30/70 BMBF/CF-PP % % Polymers & Polymer Composites, Vol. 24, No. 8,

6 Kishor Biswas and Sanjay Palsule Table 4. Izod impact strength and Charpy impact strength of CF-PP and BMBF/CF-PP composites Sample Izod Impact Strength (J/m) Standard Deviation % Increase in Izod Impact Strength Charpy Impact Strength (J/m) Standard Deviation % Increase in Charpy Impact Strength CF-PP /90 BMBF/CF-PP % % 20/80 BMBF/CF-PP % % 30/70 BMBF/CF-PP % % composites increases to 10%, 20% and 30% the Charpy impact strength of the resulting 10/90, 20/80 and 30/70 BMBF/CF-PP composites increases by 35%, 82% and 129% respectively. 4.5 Formation of BMBF/CFPP Composites The improved tensile, flexural and impact mechanical properties of the BMBF/CFPP composites, and the increase in mechanical properties of 10/90, 20/80 and 30/70 BMBF/ CFPP composites with increasing fibre content in them confirms successful formation of the BMBF/ CFPP composites. This successful formation of the BMBF/CFPP composites appears to be due to fibre/matrix interfacial adhesion and interactions between BMBF and CFPP in BMBF/CFPP composites due to Palsule process. These fibre/matrix interactions between BMBF and CFPP in BMBF/CFPP composites have been investigated and established by SEM and FTIR analysis, as discussed below. 4.6 Morphology and Fibre/ Matrix Interface Field emission scanning electron micrograph of raw bamboo fibres, chemically functionalized polypropylene (CFPP), and of the 10/90, 20/80 and 30/70 BMBF/ CF-PP composites are shown in Figures 6a-e. FE-SEM images of tensile fractured specimen of the 10/90, 20/80 and 30/70 BMBF/ CF-PP composites (Figure 6c-e) show bamboo fibres deeply embedded in and covered with CF-PP matrix in the BMBF/CFPP composites with good bonding between bamboo fibre and CF-PP matrix in the BMBF/ CFPP composites, with no voids and no gaps. This indicates good fibre/matrix interfacial adhesion between BMBF and CFPP in BMBF/ CFPP composites. The reasons for these fibre/matrix interactions in BMBF/CFPP composites have been investigated by FTIR spectroscopy, as discussed below. 4.7 Fibre/Matrix Interactions in BMBF/CFPP Composites by FTIR FTIR spectra of polypropylene (PP - used as reference), self compatibilizing chemically functionalized polypropylene (CFPP) used as matrix and of only one composite - the 20/80 BMBF/CF-PP composite - have Figure 5. Izod impact strength and Charpy impact strength of CFPP and BMBF/ CFPP composites Figure 6a,b. Field emission scanning electron micrographs of (a) Raw bamboo fibre, (b) chemically functionalized polypropylene (CFPP) (a) (b) 668 Polymers & Polymer Composites, Vol. 24, No. 8, 2016

7 Bamboo Fibre-reinforced Self-compatibilizing Functionalized Polypropylene Composites by Palsule Process Figure 6c,d,e. Field emission scanning electron micrographs of (c) 10/90 (d) 20/80 and (e) 30/ 70 BMBF/CF-PP composites (c) (e) Figure 7. Chemical structures of (a) PP and (b) CF-PP been recorded in the wave range 400 cm -1 to 4000 cm -1 for analysis of fibre/matrix interfacial adhesion in the BMBF/CFPP composites, as all other composite compositions are chemically the same. The details are discussed below. 4.8 Maleic Anhydride Grafted Polypropylene Forming CF-PP Figure 7 shows chemical structures of PP and CFPP. Chemical (d) functionalization of PP by maleic anhydride grafting on to PP to form CF-PP has been investigated by FTIR analysis of PP and CF-PP. FTIR spectra of PP and CF-PP (Figure 8) (wave number from 400 cm -1 to 4000 cm -1 ) shows the bands at 2920 cm -1 that indicates saturated aliphatic hydrocarbons in PP and also in CF- PP. The presence of the -CH 2 - and -CH 3 - aliphatic groups is confirmed by the presence of spectral band at 1460 cm -1 and 1374 cm -1 in PP and CF-PP respectively, that originate due to δch 2 and δch 3 respectively. The similar bands for the C H group, and -CH 2 - and CH 3 - groups have been recorded in literature 27,28. The FTIR spectrum of the CF-PP (Figure 8) also shows characteristic bands at 1712 cm -1 and 1791 cm -1 (in between 1700 cm -1 and 1800 cm - 1 ) that are not present in the FTIR spectrum of PP. These bands of CFPP at 1712 cm -1 and 1791 cm -1 are due to the stretching vibrations of carbonyl (C=O) groups and therefore confirm the grafted maleic anhydride groups in the CF-PP. The band at 1791 cm -1 indicates asymmetric stretching of carbonyl (C=O) of maleic anhydride. The band at 1712 cm -1 shows symmetric stretching of carbonyl of (C=O) of maleic acid that is formed by reversible hydration reaction of grafted maleic anhydride group in CF-PP (Figure 9), because CF-PP is mildly hygroscopic and has the ability to absorb moisture from the environment. 4.9 Fibre/Matrix Interfacial Adhesion in BMBF / CF-PP Composite The FTIR spectrum of only one composite composition - the 20/80 BMBF/CFPP composite -has been recorded (Figure 8), as all other composite compositions would show similar interactions between BMBF and CFPP in BMBF/CFPP composite. The structure of cellulose and a part of lignin present in bamboo fibres is shown in Figure 10. Maleic anhydride of CF-PP reacts with hydroxyl (-OH) group of cellulose, hemicelluloses and lignin of bamboo fibres - at the interface of BBMBF and CFPP in the BMBF/CFPP composite - possibly forming covalent ester linkages and hydrogen bonds. FTIR spectrum of BMBF/CF-PP composite (Figure 8) clearly shows two new bands at 1739 cm -1 and Polymers & Polymer Composites, Vol. 24, No. 8,

8 Kishor Biswas and Sanjay Palsule Figure 8. FTIR of PP, CF-PP and 20/80 BMBF/CF-PP Figure 9. Reversible hydration reaction showing formation of maleic acid from maleic anhydride group in CFPP Figure 10. Chemical structures of (a) cellulose and (b) lignin 1114 cm -1 that have not been present in the spectrum of CF-PP matrix. These bands indicate esterification reaction between the hydroxyl groups of cellulose and lignin of bamboo fibre and anhydride group of CF-PP matrix in BMBF/CFPP composite (Figure 11). The peaks associated with the (C=O) and (C-O) stretch of esterification reaction product observed at 1739 cm -1 and 1114 cm -1 confirm the formation of ester groups. The new peak at 1739 cm -1 (in the region of 1734 cm -1 to 1750 cm -1 ), indicates the formation of esters in the BMBF/CFPP composite; and the other new peak at 1114 cm -1 (in between 1000 cm -1 and 1300 cm -1 ) indicates ester group. The presence of moisture on BMBF due to its hydrophilic nature is confirmed by the bending vibration of OH groups indicated by the presence of band at 1640 cm -1 present in the spectrum of BMBF/CF-PP composite (Figure 8). FTIR spectrum of BMBF/CF-PP composite also shows spectral band at 3431 cm -1 indicating formation of hydrogen bonds between hydrogen atom of hydroxyl group on BMBF with oxygen atom of a maleic anhydride group of one CFPP molecule; and an oxygen atom on the maleic anhydride group of another CFPP molecule (Figure 12). (a) (b) 5. Conclusions Bamboo fibre-reinforced chemically functionalized polypropylene (BMBF/CF-PP) composites have been successfully developed by Palsule process, by using self compatibilizing chemically functionalized maleic anhydride grafted polypropylene matrix (in place of polypropylene) without using any compatibilizer and without any fibre surface modification. Study of the mechanical properties of the composites indicate that with the increasing amounts of bamboo fibres in the BMBF/CF-PP composites, the tensile, flexural and Izod impact properties of the 670 Polymers & Polymer Composites, Vol. 24, No. 8, 2016

9 Bamboo Fibre-reinforced Self-compatibilizing Functionalized Polypropylene Composites by Palsule Process Figure 11. Esterification reaction between the hydroxyl groups of cellulose and lignin of bamboo fibre and anhydride group of CF-PP resulting 10/90, 20/80 and 30/70 BMBF/CF-PP composites increase relative to that of the CF-PP matrix. This establishes the successful formation of the BMBF/CF-PP composites that appear to have resulted from good in-situ fibre/ matrix interfacial adhesion in BMBF/ CF-PP composites due to the use of self compatibilizing chemically functionalized modified maleic anhydride grafted polypropylene (CFPP) matrix. Fibre / matrix interfacial adhesion generated, insitu, due to interactions between bamboo fibres (BMBF) and the maleic anhydride of the chemically functionalized polypropylene (CF- PP) matrix has been established by SEM and FTIR spectroscopy. FTIR spectra of the BMBF/CF-PP composites confirms that the maleic anhydride group present on the CF- PP matrix reacts with the hydroxyl (-OH) groups present on the lignin, cellulose, hemicellulose of bamboo fibres resulting in the formation of covalent ester linkage and secondary hydrogen bonds that impart in-situ fibre/matrix adhesion in the BMBF/ CFPP composites. Palsule process is performed using conventional extruders and injection moulding machines which is easy, convenient, simple, quick, time-saving and provides short natural fibrereinforced polymer composites with acceptable mechanical properties. Figure 12. Hydrogen bond formation between hydroxyl group of BMBF and C=O group of CF-PP Polymers & Polymer Composites, Vol. 24, No. 8,

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