Applied Mechanics and Materials Vol. 315 (2013) pp 905-908 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.315.905
Melt Flow and Mechanical Properties of Polypropylene/Recycled Plaster of Paris S.S. Jikan1, a, I. Mat Arshat2, b and N.A. Badarulzaman2, c 1
Faculty of Science, Technology and Human Development, UTHM 2
Faculty of Mechanical and Manufacturing Engineering, UTHM
a
[email protected],
[email protected],
[email protected],
Keywords: Polypropylene, recycled plaster of paris, melt density, melt flow index, mechanical properties
Astract. The fabrication and characterisation of polypropylene filled with recycled plaster of paris as filler had been carried out. Six different percentage levels of filler content were designed with PP/virgin plaster of paris composite and unfilled PP as reference samples. The sample characterisations were conducted by using melt density, melt flow index, tensile test and hardness test. The results demonstrate that the weight percent of filler content greatly influence the tensile property with decreasing values of maximum load and elongation at break as well as the melt flow index. However, the increase in melt density with increasing filler content leads to improve of hardness values of all samples. Introduction Polypropylene (PP) composites have better material properties such as good strength, better stiffness, improve of ductility; good stability and thermal expansion; and low cost of production. Nevertheless, these properties depend on the matrix phase, the phase dispersion of fillers and strengthening mechanism, shapes and arrangements of filler particles and the bonding interface between filler and matrix [1]. Plaster of paris (POP) has been chosen as filler in this composite system because it is used in many ceramic manufacturing and construction sectors which produce lots of POP wastes. It becomes one of the environmental issues due to the amount of used POP that has been disposed without recycling. Therefore, it is crucial to develop new composite material which consists of recycled POP as filler in order to assist the government in addressing the environmental issue. In the literature there are some published studies relating to PP/ceramic or PP/clay composites. Most researches agreed that PP is suitable as matrix composite reinforced with ceramic materials and other materials such as kaolin [2], paper sludge [3], waste paper [4], talc and magnetite [5], clay [6], wood [7] and mica powder [8]. Nonetheless, only a few studies on POP and gypsum were found. One of the studies is on polymeric plaster composite using virgin POP and esters as fillers [9]. Another study is on the gypsum with 100 µm and 300 µm particle sizes as fillers in PP composite [10]. The effects of recycled POP (rPOP) on the properties of PP/rPOP composite have not been systematically studied. Therefore, in the present study PP/rPOP composites containing 5, 10, 15, 20, 25 and 30 wt% of rPOP, have been produced and the effect of rPOP content on melt density, melt flow index and the mechanical properties of PP/rPOP were investigated. Methodology The raw materials used in this study are PP Copolymer SM240 produced by Titan Chemical Groups from production lot SM240 A121B 10021, virgin POP (Siam Gypsium supplied by Erat Mesra Sdn. Bhd.) and recycled POP obtained from POP mould used in ceramic (slip casting) production. Both of these POP (virgin and recycled POP) were milled with planetary mono mill (Pulverisette 6, Germany) by using sintered corundum mill (99.7% Al2O3) at a speed rate of 230 rpm for 10 minutes. Next, these POP were sieved and graded by Fritsch sieve shakers. Only POP particles which are in the range of 36 to 44 µm are used as fillers with filler contents of 5, 10, 15, All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 183.171.168.72, Department of Materials and Design, Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, Malaysia, Parit Raja, Malaysia-05/03/13,07:21:50)
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20, 25 and 30 wt%. The sample was compounded using heated two roll-mill at the processing temperature of 185oC for 30 minutes. Upon completion of the compounding process, all samples were crushed by using granulator (Plastic Granulator SLM50FY, Taiwan) prior to injection moulding process. The barrel temperatures used for injection moulding process would be different from one zone to another. They are feeding, rear, middle, front and nozzle zones at processing temperatures of 70°C, 135–145°C, 165°C, 175°C and 170°C, respectively. The melt flow indices (MFI) of samples were evaluated according to ASTM D1238 via Plastometer (CEAST type 6841). Whereas for tensile test, a Universal Testing Machine (Shimadzu Autograph, Japan) was used and the results were analysed according to ISO 527-5A (MS). Lastly, Durometer hardness test has been selected because it is suitable for plastic materials. The reading for hardness test was taken 1-2 seconds after the notch tip was embedded into the samples. The hardness test is measured according to ASTM D2240. Result and Discussion Melt Density and Melt Flow Index. As shown in Fig. 1(a), The results obtained from the melt density tests of PP/virgin POP (PP/vPOP) and PP/recycled POP (PP/rPOP) exhibit great difference in the values of the composites melt density by the addition of fillers either virgin or recycled POP. The melt density values of both composites; PP/vPOP and PP/rPOP increased with higher filler contents. The density of POP is larger than PP. Therefore, by introducing more PP (as filler) into the system, it leads to the increase in melt density values of all samples. This finding is supported by the results demonstrated in Fig. 1(b) which shows an opposite trend of the flow curves. The MFI of all composites reduced with the increase in the addition of fillers in the system. The use of higher density materials as fillers could effect the melt flowability of the system. The results demonstrate large contribution of filler content in the composites melt flow. This scenario delivers agreeable results with the one obtained by Eroglu [11] which shows that the MFI values were decreased to lower value when fillers were added in the PP composite.
PP/vPOP PP/rPOP
(a)
PP/vPOP PP/rPOP
(b)
Fig. 1: (a) The relationship between melt density values and filler (POP) contents of PP/vPOP and PP/rPOP composites (b) The relationship between MFI values and filler (POP) contents of PP/vPOP and PP/rPOP composites Mechanical Properties: Tensile Analysis. Tensile tests were carried out to obtain the mechanical properties of all samples such as maximum load and elongation at break. Figures 2(a) and 2(b) show comparisons of maximum load and elongation at break versus POP content for both PP/vPOP and PP/rPOP composites. Unfilled PP exhibits the highest value of maximum load and elongation at break if compared to that of all composites. The incorporation of 5 wt% of either vPOP or rPOP into PP matrix decreases the maximum load and elongation at break values by approximately 1 2.5% and 5- 10%, respectively. Subsequent increase of vPOP and rPOP wt% in PP matrix decreases higher percentage of the maximum load and elongation at break values due to the changes in the mechanical properties whereby the composites are believed to be more brittle. The results obtained are similar with previous study done by Sharma & Mahanwar [12] which discovered that the maximum load and elongation at break decreasing when the filler content or reinforcing agent in the matrix increases.
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PP/vPOP Maximum Load, N
PP/rPOP
POP content, %
Fig. 2 (a): Effect of filler (POP) content on the maximum load of PP/vPOP and PP/rPOP composites
Elongation At Break, %
PP/vPOP PP/rPOP
POP content, %
Fig. 2 (b): Effect of filler (POP) content on the elongation at break of PP/vPOP and PP/rPOP composites Mechanical Properties: Hardness Test. Figure 3(a) and 3(b) show the relation of the hardness values versus vPOP and rPOP contents for both composites and comparison of the increasing percentage of the hardness (Hs) values for both composites, respectively. The range of the hardness values lies between 66.1 to 71.0 Hs for PPv/POP composites whereas PP/rPOP composites exhibit the range of hardness values between 65.5 to 70 Hs. It is obvious from Fig. 3(a) that pure PP shows the lowest hardness value which is 63.6 Hs. The hardness values of all composites increase with the increase of either vPOP or rPOP content. Subsequent addition of either vPOP or rPOP up to the highest amount of 30 wt% in PP matrix demonstrates gradual increase in hardness values. Nevertheless, the increases of these hardness values are relatively small.
(a)
PP/vPOP
PP/vPOP
PP/rPOP
PP/rPOP
(b)
Fig. 3 (a): Comparison of hardness (Hs) values of PP/vPOP and PP/rPOP composites (b) Comparison of the increasing percentage of the hardness (Hs) values for both composites
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Conclusion A new, PP/rPOP composite material has been developed and characterised. The obtained results show significant reduction in the melt flow index, maximum load and elongation at break with increasing of filler content up to 30 wt%. Nevertheless, the values of melt density and hardness values are inversely proportional to the wt% of filler content. Acknowledgment This work is supported by Short Term Grant (Vot 1010) from Universiti Tun Hussein Onn Malaysia. References [1]
H. Ismail, Komposit Polimer Diperkuat Pengisi dan Gentian Pendek Semulajadi. Pulau Pinang: Penerbit Universiti Sains Malaysia. (2004) 1-18. [2] S.N. Maiti & B.H. Lopez, Tensile Properties of Polypropylene/Kaolin Composites, Journal of Applied Polymer Science. 44:2 (1993) 353-360. [3] A.R. Sanadi & R.A. Young, Analysis of Tensile and Impact Properties in the Recycled Newspaper Fibers as Reinforcing in Polypropylene, Journal of Reinforced Plastic and Composites. 13 (1994) 54-67. [4] Suryadiansyah, H. Ismail & B. Azhari, Waste Paper Filled Polypropylene Composites: the Comparison Effect of Ethylene Diamine Dilaurate as a New Compatibilizer with Maleic Anhydride Polypropylene, Journal of Reinforced Plastics and Composites. 26 (2007) 51-67. [5] B. Weidenfeller, M. Höfer, Michael & F.R. Schilling, Thermal conductivity, thermal diffusivity, and specific heat capacity of particle filled polypropylene, Composites Part A: Applied Science and Manufacturing. 35:4 (2004) 423-429. [6] A.K. Chaudhary & K. Jayaraman, Extrusion of linear polypropylene–clay nanocomposite foams, Polymer Engineering & Science. 51:9 (2011) 1749–1756. [7] D.G Dikobe & A.S. Luyt, Comparative Study of the Morphology and Properties of PP/LLDPE/Wood Powder and MAPP/LLDPE/Wood Powder Polymer Blend Composites. Express Polymer Letter. 4:11 (2010) 729-741. [8] S. Farzaneh & A. Tcharkhtchi, Viscoelastic Properties of Polypropylene Reinforced with Mica in and Transition Zones, International Journal of Polymer Science, vol. 2011, Article ID 427095, 5 pages (2011) doi:10.1155/2011/427095 [9] J. Dweck, B.F. Andrade, E.E.C. Monteiro & R. Fischer, Thermal Characterization of Polymeric Plaster Composites, Journal of Thermal Analysis and Calorimetry, 67:2 (2004) 321-326. [10] C.J.R. Verbeek & B.G.J.W. Plessis, Density and Flexural Strength of PhosphogypsumPolymer Composites. Journal of Contruction and Building Materials. 19 (2005) 265-274. [11] M. Eroglu, Effect of Talc and Heat Treatment on the Properties of Polypropylene/EVA Composite. International Journal of Science & Technology. 2 (2007) 63-73. [12] Sharma, A.K. & Mahanwar, P.K., Effect of Particle Size of Fly Ash on Recycled Polyethylene Terephthalate/Fly Ash Composites. International Journal of Technology. 14 (2010) 53-64.
