Studies on the Water Absorption Properties of Short Hemp—Glass Fiber Hybrid Polypropylene Composites

Abstract

Hemp fiber is one of the inexpensive and readily available bast natural fibers and hemp-fiber reinforced polymer composite products have gained considerable attraction for automotive interior products. Though extensive research has been made on the performance evaluation of these composite materials, not much data is available on the moisture absorption of the composites, which restricts their use in exterior applications. This study aims to investigate the moisture absorption of short hemp fiber and hemp-glass hybrid reinforced thermoplastic composites to study their suitability in outdoor applications. The water absorption properties and its effect on the tensile properties of hemp and hemp/glass fiber hybrid polypropylene (PP) composites prepared by an injection molding process were investigated. Effect of hybridization on the water uptake and the kinetics of moisture absorption of the hemp fiber composites were evaluated by immersing the hybrid composite samples in distilled water at different temperatures, of 40, 60 and 80^°C. The composites showed a Fickian mode of diffusion; however, a deviation was observed at higher temperature and may be attributed to the microcraks developed at the interface and dissolution of the lower molecular weight substances from the natural fibers. Equilibrium moisture content (M_m) showed that water up take of 40 wt% hemp fiber reinforced PP composites was highest and incorporation of glass fiber decreased the water uptake significantly (40%). Equilibrium moisture content was found to be independent of temperature, while diffusion coefficient (D) was increased with temperature. Effect of water absorption on the tensile properties of the composites showed that there is a significant reduction in strength and stiffness. It was observed that hybridization with glass fibers did not have any significant effect on the strength properties of the aged samples. The tensile properties of the re-dried aged samples showed an increased retention of strength properties after drying; however a complete recovery of the properties has not been achieved. This indicated that water absorption is not a physical process and permanent damage occurred to the composite after aging.

Keywords

natural fiber composites hemp fiber water absorption tensile properties.

References

Woodhams, R.T. , Thomas, G. and Rodgers, D.K. (1984). Wood Fibres as Reinforcing Fillers for Polyoefins, Poly. Eng. Sci., 24: 1166—1171.

Bledzki, A.K. , and Gassan, J. (1999). Composites Reinforced with Cellulose Based Fibers, Prog. Polym. Sci., 24(2): 221—274.

Sain, M. , Law, S. , Suhara, F. and Boullioux, A. (2005). Interface Modification and Mechanical Properties of Natural Fibre — Polyolefin Composite Products, J. Reinf. Plast. Comp., 24(2): 121—130.

Balatinecz, J.J. and Park, B.D. (1997). The Effects of Temperature and Moisture on the Properties of Wood Fiber Thermoplastic Composites, J. Thermoplast. Comp. Mater., 10: 476—487.

George, J. , Bhagawan, S.S. and Thomas, S. (1998). Effect of Environment on the Properties of Low-density Polyethylene Composites Reinforced with Pineapple Leaf Fiber, Comp. Sci. Technol., 58: 1471—1485.

Marcovich, N.E. , Reboredo, M.M. and Aranguren , M.I. (1999). Moisture Diffusion in Polyester Wood Fiber Composites, Polymer , 40: 7313—7320.

Singh, B. , Gupta, M. and Verma. A. (2000). The Durability of Jute Fiber Reinforced Phenolic Composites, Comp. Sci. Technol., 60(4): 581—589.

Stamboulis, A. , Baillie, C.A. , Garkhail, S.K. , Van Melick, H.G.H., and Peijs, T. (2000). Environmental Durability of Flax Fibers and their Composites Based on PP Matrix, Appl. Comp. Mater., 7: 273—294.

Joseph, P.V. , Rabello, M.S. , Mattoso, L.H.C. , Joseph, K. and Thomas, S. (2002). Environmental Effects on the Degradation Behaviour of Sisal Fiber Reinforced Polypropylene Composites , Comp. Sci. Techol., 62: 1357—1372.

10.

Lin, Q. , Zhou, X. and Dai G. (2002). Effect of Hydrothermal Aging and Environment on Moisture Absorption and Mechanical Properties of Wood Flour Filled Polypropylene Composites, J Appl. Polym. Sci., 85(14): 2824—2832.

11.

Manikandan Nair, K.C. and Thomas, S. (2003). Effect of Aging on the Mechanical Properties of Short Sisal Fiber Reinforced Polystyrene Composites , J. Thermoplast. Comp. Mater., 15: 249—271.

12.

Tajvidi, M. and Ebrahimi, G. (2003). Water Uptake and Mechanical Characteristics of Natural Filler Polypropylene Composites, J. Appl. Polym. Sci., 88: 941—946.

13.

Espert, A. , Vilaplana, F. and Karlsson, S. (2004). Comparison of Water Absorption in Natural Cellulosic Fibers from Wood and One Year Crops in Polypropylene Composites and its Influence on their Mechanical Properties, Comp. Part A, 35: 1267—1276.

14.

Arbelaiz, A. , Fernandez, B. , Ramos, J.A. , Retegi, A. , Liano-Ponte, R. and Mondragon, I. (2005). Mechanical Properties of Short Flax Fiber Bundle Polypropylene Composites: Influence of Fiber Matrix Modification, Fiber Content, Water Uptake and Recycling, Comp. Sci. Technol., 65: 1582—1592.

15.

Rozman, H.D. , Tay, G.S. , Kumar, R.N. , Abusamah, A. , Ismail, H. and Mohd.Ishak, Z.A. (2001). Polypropylene Oil Palm Empty Fruit Bunch — Glass Fiber Hybrid Composites: a Preliminary Study on the Flexural and Tensile Properties, Europ. Polym. J., 37: 1283—1291.

16.

Thwe, M.M. and Liao, K. (2002). Effects of Environmental Aging on the Mechanical Properties of Bamboo—Glass Fiber Reinforced Polymer Matrix Hybrid Composites , Comp. Part. A, 33: 43—52.

17.

Sreekala, M.S. , George, J. , Kumaran, M.G. and Thomas, S. (2002). The Mechanical Performance of Hybrid Phenol—Formaldehyde Based Composites Reinforced with Glass and Oil Palm Fibers, Comp. Sci. Technol., 62: 339—353.

18.

Mishra, S. , Mohanty, A.K. , Drzal, L.T. , Misra, M. , Parija, S. , Nayak, S.K. and Tripathy, S.S. (2003). Studies on Mechanical Performance of Biofiber/Glass Reinforced Polyester Hybrid Composites, Comp. Sci. Technol. , 63: 1377—1385.

19.

Williams, G.I. and Wool, R.P. (2000). Composites from Natural Fibers and Soy Oil Resins, Appl. Comp. Mater., 7: 421—432.

20.

Sèbe, G. , Cetin, N.S. , Hill, C.A.S. and Hughes, M. (2000). RTM Hemp Fibre-reinforced Polyester Composites , Appl. Comp. Mater., 7: 341—349.

21.

Pervaiz, M. and Sain, M.M. (2003). Sheet Molded Polyolefin Natural Fiber Composites for Automotive Applications, Macromol. Mater. Eng., 288: 553—557.

22.

Bledzki, A.K. , Fink, H.P. and Speecht, K. (2004). Unidirectional Hemp and Flax EP- and PP-Composites: Influence of Defined Fiber Treatments, J. Appl. Polym. Sci., 93: 2150—2156.

23.

Rouison, D. , Sain, M. and Couturier, M. (2004). The Effect of Surface Modification on the Mechanical Properties of Hemp Fiber/Polyester Composites, SAE World Congress and Exposition, SAE Paper No. 2004-01-0728.

24.

Mohanty, A.K. , Wibowo, A. , Misra, M. and Drzal, L.T. (2004). Effect of Process Engineering on the Performance of Natural Fiber reinforced cellulose acetate biocomposites , Comp. Part A, 35: 363—370.

25.

Behzad, T. and Sain, M. (2005). Cure Simulation of Hemp Fiber Acrylic Based Composites During Sheet Molding Process, Polym. Polym. Comp., 13(3): 235—244.

26.

Mehta, G. , Drzal, L.T. , Mohanty, A.K. and Misra, M. (2006). Effect of Fiber Surface Treatment on the Properties of Biocomposites from Nonwoven Industrial Hemp Fiber Mats and Unsaturated Polyester Resin, J. Appl. Polym. Sci., 99: 1055—1068.

27.

Mishra, S. and Naik, J.B. (1998). Absorption of Water at Ambient Temperature and Steam in Wood—Polymer Composites Prepared from Agrowaste and Polystyrene , J. Appl. Polym. Sci., 68: 681—686.

28.

Mishra, S. , Naik, J.B. and Patil, Y.P. (2004). Studies on Swelling Properties of Wood/Polymer Composites Based on Agro-waste and Novolac, Advances in Polym. Technol., 23: 46—50.

29.

Rouison, D. , Couturier, M. , Sain, M. , MacMillan, B. and Balcom, B.J. (2005). Water Absorption of Hemp Fiber/Unsaturated Polyester Composites, Polym. Comp. , 26: 509—525.

30.

Panthapulakkal, S. and Sain, M. (In Press). Injection Molded Short Hemp Fiber/Glass Fiber Reinforced Polypropylene Composites—Mechanical, Water Absorption, and Thermal Properties, J. Appl. Polym. Sci.

31.

Zhou, J. and Lucas, J.P. (1995). The Effects of Water Environment on Anomalous Absorption Behaviour in Graphite/Epoxy Composites, Comp. Sci. Technol., 53: 57—64.

32.

Loos, A.C. and Springer, G.S. (1981). Moisture Absorption of Polyester — E —glass Composites, Environmental Effects on Composite Materials. 51—62, Technomic Publishing Co. Inc., CT, USA.

33.

Crank, J. (1956). Mathematics of Diffusion, p-347, Oxford University Press, Oxford.

34.

Comyn, J. (1985). Polymer Permeability, p-383, Elsevier Applied Science Publishers .

35.

Metcalfe, AG and Schmitz, G.K. (1972). Mechanism of Stress Corrosion in E-glass Filaments, Glass Technol., 12(1): 15—23.

36.

Mohd Ishak, Z.A. and Lim, N.C. (1994). Effect of Moisture Absorption on Tensile Properties of Short Glass Fiber Reinforced (Polybutylene Terephthalate), Polym. Eng. Sci., 34: 1645—1655.