DEVELOPMENT AND CHARACTERIZATION OF NATURAL FIBER REINFORCED POLYPROPYLENE COMPOSITES

Abstract

Natural fibers offer the potential to deliver greater added value, sustainability, renewability and lower costs. At present, automotive industries throughout the world have particularly displayed greater interest in initiating the design and engineering of new products with eco-friendly advantages. In addition to these advantages, easy availability, biodegradability, eco-friendliness, and light weight of natural fibers attracted our- fention in the application oriented research areas. Uttarakhand (Himalayan region) has got about 4121 sq. km. (32.43%) or 412100 hectare Pine (Chir) forest along with other coniferous forest. As per reportedestithid, about three tons of pine needles are generated during peak season in one re, thus total I736300 tons of pine needles may be generated from the pine forests every year, ' 'be pjpe idles are a fire hazard to the forest and a toxic irritant to the inhabitants of closer vicinity, as these do not allow the grass to grow underneath for the cattle and forest animals. Although several usage of pine needles have been reported such as fiber board, packing box, extracting essential oil, producing ligno-sulfonates and making pine wool etc. but still pine needles have not been fully utilized for any industrial purpose. The broad objective of the present work is to develop a low cost eco friendly and partially bio degradable reinforced thermoplastic composite utilizing the pine needles and secondary kraft pulp fibers as reinforcing materials. Pine needles and. secondary kraft pulp fibers are low cost and easily available natural fibers. Among thermoplastics, Polypropylene has been selected as a matrix resin for pine needles and secondary fiber reinforcement due to its low density, excellent processability, high mechanical properties, excellent electrical properties, good dimensional stability and high impact strength. Composites are prepared with varying load of fillers, varying dosages of compatibilizer namely Maleic Anhydride grafted Polypropylene (MA-g-PP) to improve the interface bonding between fiber and the matrix, and surface modifying reagent (Stearoyl chloride). Finally the composites were characterized for physical, mechanical, thermal, structural and surface properties Composite were prepared by using treated Pine Needle Filler (TPNF), Un-treated Pine Needle Filler (UPNF) and Short Pine Needle (SPN) prepared from the pine needles, and Secondary Kraft Pulp Filler (SKPF) procured from the paper mill. Glass fiber (GF) composites were made for comparison purpose. The TPNF, UPNF, and SKPF fillers were consisting of fibers having avg. length of 0.545 mm, 0.583 mm, 0.572 mm, and diameter 33.7 III gm, 34.5 pm, 24.8 pm respectively. All the composites materials were compounded by using co-rotating twin screw extruder (with 30 mm diameter and 33:1 LID ratio make: M/s Japan Steels works, Japan) for efficient mixing. Sample preparation was carried out in an injection molding machine (M/s ARBURG 500-210, Germany). TPNF/PP and SKPF/PP composites were prepared by varying filler loading (10, 20 and 30wt%) with 2 and 6wt% MA-g-PP. UPNF/PP and SPN/PP composites were prepared at 20wt% loading with 0, 2 and 6 MA-g-PP. Studies on Fiber surface modification of fillers were carried out by using Stearoyl chloride (Stcl) (10 and 20 wt% Stcl) with varying filler loading (10 and 20wt%),. The data. obtained for tensile strength, tensile modulus and elongation at break was fitted and tested on the Nicolais and Narkis model and Halpin Tsai models for relative tensile strength, Kerners's model and Halpin Tsai model for relative tensile modulus, and Nielson model for relative elongation at break. The findings of the study are considered as below. The tensile strength, tensile modulus, flexural strength and flexural modulus of TPNF/PP composites increased with increase in TPNF content but impact strength and elongation at break decreases. Incorporation of MA-g-PP enhanced the tensile strength and tensile modulus but has no significant effect on the impact strength and elongation at break of TPNF/PP composites. The highest tensile strength and flexural strength was found to be 39.15 MPa and 51.75 MPa respectively for 30% TPNF loading with 6% MA-g-PP. Deterioration in all strength properties except flexural strength is observed with the use of UPNF or SPN in composite making with PP. However, incorporation of MA-g-PP results in improvement in strength properties. Flexural strength of UPNF and SPN composites found to be comparable with that of TPNF/PP composites. The tensile strength, tensile modulus, flexural strength and flexural modulus of SKPF/PP composites increased with increase in SKPF content but impact strength and elongation at break decreases. Incorporation of MA-g-PP enhanced the tensile strength and tensile modulus but has no significant effect on the impact strength and elongation at break of SKPF/PP composites. The highest tensile strength and flexural strength found to be 45.87 MPa and 62.45 MPa respectively is for 30% SKPF loading with 6% MA-g-PP. Use of Stearoyl chloride (Stcl) modified pine needle filler leads to the decrease in tensile strength, impact strength and elongation at break of composites. However elongation at break is higher than that of TPNF/PP with MA-g-PP composites. The flexural strength of TPNF/PP composites increased with Stcl modified TPNF loading. The highest value obtained is 40.95 MPa for 20% TPNF/PP (20% Stcl modified) composite. The flexural strength of iv SKPF/PP composites increased with Stcl modified SKPF loading. The highest value obtained is 44.34 MPa for 20% SKPF/PP (20% Stcl modified) composite. Thermal stability of composites TPNF/PP composites were found to decrease with the increase of filler loading. Initial weight losses (5%) of composites were observed at lower temperatures with increase in MA-g-PP content. Char yield content increased with filler loading. Increased MA-g-PP content reduced the percentage of char yield. UPNF and SPN/PP composites showed even lower thermal stability. Initial weight-loss (5%) of-SPN-composites occurred at lower temperatures compared to UPNF composites. Char yield content decreased with increase in MA-g-PP content. Low Char yield content was observed in SPN/PP composites. Crystallinity decreased with increase in filler loading. Slight decrease in crystallinity was observed with MA-g-PP content. Thermal stability of composites SKPF/PP composites were decreased with increase in filler loading. Initial weight losses (5%) of composites were observed at lower temperatures with increase in MA-g-PP content. Char yield content increased with filler loading. Increased MA-g-PP content increased the percentage of char yield. Stcl modified composites showed initial weight losses at lower temperatures when compared to MA-g-PP content TPNF/PP composites. Increased percentage of Stcl reduced the percentage of char yield. Crystallinity decreased with increase in TPNF loading. Slight decrease in crystallinity was observed with Stcl modification. Stcl Modified composite- showed char yield content almost nil. Low percentage of crystallinity was found in UPNF/PP ' composites. However, slight improvement in crystallinity was observed in UPNF/PP and SPN/PP composites with increase in Stcl modification. Stcl modified composites showed initial weight losses at lower temperatures when compared to MA-g-PP content SKPF/PP composites. Increased percentage of Stel increased the percentage of char yield. The density of the composites decreased with increase in filler content. Least value was observed at 30% TPNF/PP composites. No significant change was observed by MA-g-PP content and Stcl modification in the density of the composites. The densities of composites were almost same in case of UPNF and SPN composite with MA-g-PP content and Stcl modification. Least value was observed at 30% SKPF/PP composites. No significant change. was observed by MA-g-PP content and Stcl modification in the density of the SKPF/PP composites. Melt flow Index value decreased with increase in TPNF loading. However, a slight improvement was observed with MA-g-PP content. The highest value i.e 8.96 g/min is obtained with 6% MA-g-PP content and 10% TPNF loading. Melt Flow Index of UPNF and V SPN composites were slightly increased with MA-g-PP content. Melt flow Index value decreased with increase in SKPF loading. However, a slight improvement was observed with MA-g-PP content. The highest value i.e 7.84 glmin is obtained with 6% MA-g-PP content and 10% SKPF loading.Decrease in MFI values of Stcl modified TPNF composites was observed when compared to TPNFIPP composites with MA-g-PP. such behavior was also found in UPNF/PP and SPNIPP composites with Stcl modification. However Stcl modified UPNF and SPN composites showed low MFI values than MA-g-PP content composites. Increase in MFI values of Stcl modified SKPF composites was observed when compared to SKPF/PP composites with MA-g-PP. Water absorption increased with increase in TPNF loading. 30% TPNF composites showed higher water absorption i.e 2.374 %. With increase in MA-g-PP content, the water absorption capacity was slightly reduced. UPNF and SPN composites without MA-g-PP showed higher water absorption compared to composite with MA-g-PP content. However UPNF composites showed higher water absorption compared to SPN composites. Water absorption increased with increase in SKPF loading. 30% SKPF composites showed higher water absorption i.e 2.804 %. With increase in MA-g-PP content, the water absorption capacity was slightly reduced. Reduction in water absorption was also found in Stcl modified TPNF/PP composites. No significant effect was observed by Stcl modification in water absorption characteristics. Reduction in water absorption was also found in Stcl modified SKPF/PP composites. Composites of TPNF/PP with or without MA-g-PP and Stcl modified filler showed high sensitivity to flame i.e no flame retardancy behaviour. UPNF/PP and SPNIPP composites showed high sensitivity to flame i.e no flame retardancy. Composites of SKPF/PP with or without MA-g-PP and Stcl modified filler showed lack of flame retardancy characteristics. Glass Fiber/Polypropylene composites were developed only for comparing the properties with pine needle and secondary kraft pulp filler reinforced polypropylene based composites. The mechanical properties of glass fiber composites are better than pine needles and secondary kraft pulp based PP composites. However, For low strength and load bearing applications the pine needles and secondary kraft pulp filler are suitable on the basis of the mechanical properties.