Influence of kaolin filler on the mechanical properties of Luffa cylindrica/ polyester composite

doi:10.21203/rs.3.rs-270130/v1

PDF

Research Article

Influence of kaolin filler on the mechanical properties of Luffa cylindrica/ polyester composite

https://doi.org/10.21203/rs.3.rs-270130/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

Polymeric materials are used in different industrial applications because they retain good environmental properties, low-cost, and easy to produce compared to conventional materials. This study investigated the effect of adding kaolin micro-filler (KF) on the mechanical properties of Luffa Fiber (LCF) reinforced polyester resin. Luffa cylindrica fiber treated with 5% NaOH, varied in weight fraction (5, 10, and 15%wt) was used to reinforce unsaturated polyester resin using hand lay-up method, whereas for the hybrid composite kaolin filler were kept constant at 6wt% fraction while the fibers varied as in the mono-reinforced composite. The samples were machined for mechanical and microstructural analysis. Analysis of the result revealed that the addition of kaolin has enhanced greatly the mechanical properties of Luffa-fibre based composites. The result reveal of the microstructure analysis, shows that there is an improvement in fiber-matrix adhesion.

Materials Engineering

Luffa cylindrica fiber

Kaolin micro filler

Polymer matrix composite

The demand for polymer composites reinforced or filled with natural fibers and powders for various industrial applications (construction, automobiles, furniture, and sporting goods) is growing because they retain good environmental performance, low cost, and easy of production compared to traditional materials [1–3]. Low price, low weight and minimized impact on environmental pollution are the key reasons for the rapid development of polymer composite materials. Recent research efforts are aimed at finding alternative fillers to replace inorganic fillers [4]. In addition to inorganic fillers, the use of natural fibers (organic fillers) also has the following advantages: low-cost, low density, non-abrasive, biodegradable, availability from natural resources, they are recyclable, and they are renewable natural resources [5–6]. Natural fiber reinforced FRP can solve efficiency and environmental issues.

Luffa cylindrica is a naturally occurring cucumber vine in many countries. Luffa 's young cylindrical fruits are edible and contain a number of compounds, including ribosome-inactivating flavonoids, phenols, triterpenes, and proteins. For medicinal purposes, such as immunostimulants and anti-inflammatory agents, the Luffa fruit has been used effectively [7]. Luffa sponge has been successfully used in the biosorption process of heavy metals in waste water and is an essential natural fiber. This emerging cash crop has the full potential to improve the economies of developing nations [7–10]. There is 84% holocellulose, 66% cellulose, 17% hemi-cellulose, 15% legnine, 3.2% extractives, and 0.4% ashes in Luffa fiber physical properties. The physical properties of Luffa fiber are 820 kg / m3 mass, 25–60 µm diameter and 59.1 crystallinity index [11–13]. Oboh et al. Have given functions and applications of Luffa fiber in agriculture, medicine and science and technology. Msahli et al. Studies have shown that the bending strength and adhesion between Luffa fibers and the polyester matrix can be strengthened by acetylation and cyanoethylation of Luffa fibers.

In order to improve performance and reduce costs, fillers are used with different commodities and engineering polymers. The use of inorganic mineral fillers in plastic resins will increase the different physical properties of the material, such as mechanical strength and modulus. Generally, the mechanical properties of particle-filled polymer composites largely depend on the size, shape, distribution of filler particles in the polymer matrix, and degree of interfacial adhesion between filler and matrix [14–17]. Calcium carbonate, kaolin, mica and talc are most commonly used as fillers to minimize production costs and enhance thermoplastic properties such as crystallinity, stiffness, stiffness, flexural modulus, resilience, dimensional stability, electrical conductivity and thermal conductivity. In order to prepare particle composites, Al-Asade and Al-Murshdy studied the addition of kaolin into an unsaturated polyester matrix. The addition of 3–9% of kaolin to the unsaturated polyester resin indicates that the kaolin acts as a binder, and the resulting composite material acts as a particle strengthening agent, resulting in the improvement of the mechanical properties of the unsaturated polyester [18]. Ahmed et al. studied another study of kaolin composite polyester. In this study, a polymer composite made of diethylene glycol and untreated kaolin (based on PET waste derived from unsaturated polyester) was tested. Thermal and chemical methods have been carried out to process kaolin. These treatments affect the mechanical and electrical properties of kaolin filled polymer composites [19]. These reports motivated us to consider the inspiring possibility of incorporating the fine micron-sized kaolin particles in a composite comprising of luffa reinforced polyester to study their effects on the mechanical properties of the composites.

The hybridization of fibers with fillers has been utilized to enhance the properties of composites. A wise choice of matrix and reinforcing phase contribute to a composite with a combination of strength and modulus comparable to or even better than those of conventional metallic materials. Improving the properties of polymers and their composites by adding particulate filler materials in industrial and structural applications has shown great promise, and has recently attracted great attention. Sakthivel M et al., reseached on the feasibility of using luffa fibers/coir as reinforcement for a polymer such as polypropylene in particulate form. They found that the addition of both reinforcement materials based on lignocellulose, resulted in improved mechanical properties, and there was continuous proof of consistency between the two materials [20]. Srinivasan C. studied the effect of fiber treatment and addition of SiO2 nanoparticles on the properties of composite materials. Fiber treatment has been proven to improve the efficiency of the fiber/matrix interface, and the mechanical properties can be improved by adding SiO 2 nanoparticles [21]. Panneerdhass R. et al., used luffa fiber and peanut shell particles to reinforce epoxy resin. It was found that the tensile, compressive, flexural, and impact strength were observed at the reinforcement volume fraction [22]. Fayomi O. et al., the effect of fiber and particles of luffa cylindrica on the mechanical properties of epoxy resin was studied. The samples were machined for mechanical and microstructure analysis. The result is that the mechanical and morphological properties of epoxy resin are modified by the addition of luffa fiber and particulate matter. The composite material surface suggests that a higher weight can cause a brittle fracture [23].

Based on the literature reviews the use of kaolin and luffa cylindrica together so far has not been examined as reinforcing filler in the production of composite. The present work aims to investigate the effect of kaolin as filler in luffa fiber reinforced polyester hybrid composites. Tensile strength, flexural strength, impact strength, and hardness values were measured for both unfilled and kaolin filled luffa/polyester composites. The results of the mechanical properties are presented and discussed.

2.1. Materials and quipment

The reinforcement materials applied in this research are luffa fiber, kaolin filler, and the matrix is a polyester resin. They all come from local sourced. Equipment applied for characterization of composites are; Monsanto tensometer, Vickers hardness tester (model: MVI PC), and Charpy impact testing machine (model:412).

2.1. Reinforcement preparation

The Luffa cylindrical fiber was treated at 80oC with a 5% NaOH solution. It was washed with distilled water and dried at room temperature for 1 day from the outside surface after treatment to extract lignin, oil, and luffa fiber wax, and then dried at room temperature. After drying in the sun for a few days, a fibrous mat (130 mm by 120 mm) was cut out of the outer core of the luffa fruit shell, mounted further between two flat wooden plates and straightened to an even thickness by applying a uniform compressive load with the mechanical Bench Vices for a few hours. Kaolin was used as a microparticulate filler and pure unsaturated polyester was used as the matrix material. Micro particulate fi!Jer (kaolin) was procured from the department Chemical Engineering, Ahmadu Bello University, Zaria, Nigeria. Unsaturated polyester resin, hardener, sodium hydroxide pellets, acetone, and petroleum gel were obtained from Olasco Ltd, Zaria, Nigeria.

2.2. Composite fabrication

To create the composite, a conventional process called the hand lay-up process was used. The hand lay-up method has been a widely studied method of manufacturing natural fiber-based composites because of its flexibility, cost-effectiveness, and durability, which is economically feasible for developing countries and less financially supported universities and colleges. Fiber (luffa) was varied at weight fraction (5, 10, and 15%wt) for the fiber reinforced composite, whereas for the hybrid composite the filler (kaolin) was kept constant at 6wt% fraction while the fiber (luffa) was varied as in the mono-reinforced composite. The required quantity of polyester matrix and kaolin was weighed using an electronic weighing balance and put in a 200 ml glass beaker. In order to prevent aggregation and to achieve a faster and more accurate distribution of the filler in the polyester resin matrix, the composite mixture was thoroughly stirred for 10 minutes using a long glass rod. Subsequently, methyl-ethyl-ketone-peroxide (MEKP) catalytic converter was introduced using a disposable syringe at a ratio of 10 ml of polyester to 0.2 ml of catalytic converter and stirred for around two minutes, after which the cobalt naphthenate accelerator was applied at a rate of 10 ml of polyester to 0.1 ml of accelerator and stirred for another two minutes. The mold release layer was laid over the wooden molds prepared for the tensile, flexural, impact and hardness tests of specimens (120 x 5 x 15 mm, 100 x 30 x10 mm, 100 x 10 x 10 mm and 10 x 10 x 10 mm respectively) to extract the composite material quickly and easily, and the release spray was applied to the inner surface of the mold. A thin layer of the mixture was poured after keeping the mold on the plywood, followed by the distribution of the fiber laminate on to the mixture. The mixture was applied over the fiber laminate, and the process was repeated in order to achieve the desired thickness. Care was taken to ensure correct wetting between the matrix and reinforcement before a compressive load of 150 KN was applied to ensure proper bonding and to push out trapped gases. The samples were allowed to cure for 72 hours and the mold samples were taken for mechanical testing. The label and description of the composite samples are indicated in Table 1.

Table 1

Detailed designation and composition of composites.
Label	Composition
C1	Polyester + Luffa fiber(0 wt%)
C2	Polyester + Luffa fiber (5 wt%)
C3	Polyester + Luffa fiber (10wt%)
C4	Polyester + Luffa fiber (15 wt%)
C5	Polyester + Luffa fiber (5 wt%) + kaolin (6 wt%)
C6	Polyester + Luffa fiber (10 wt%) + kaolin (6 wt%)
C7	Polyester + Luffa fiber (15 wt%) + kaolin (6 wt%)

2.3 Mechanical Testing

2.3.1 Tensile strength result

Tensile test samples were machined to a dumb-bell shaped of dimension 100.0 × 15.0 × 5.0 mm according to ASTM D638 and claimed between the upper and lower jaws of the Monsanto tensometer (type 'W') and the machine was loaded. The samples were stretched in the device until the sample ruptured. The values of the breaking load and elongation were taken accordingly. The test was repeated three times for each sample of the composite and the average value was recorded.

2.3.2 Flexural strength result

The flexural test was carried out on specimens measuring 100.0 × 30.0 × 10.0 mm according to ASTM (D790) using a computerized Instron 3369 Universal Testing Machine with a load cell capacity of 50KN. The three-point bend flexural test method was used with a cross-head speed of 5 mm/min and a span length of 65mm. Samples were positioned on the support span and the load was applied to the center by the loading nose producing three-point bending. The test was stopped at 5% deflection.

2.3.3 Hardness Test

The hardness test was carried out on each specimen according to ASTM C1327 with a dimension of 10.0 x 10.0 x 60 mm. The indentation technique using a Vickers diamond pyramid indenter on the microhardness tester was used. The measurement was done on the surface by applying 0.3kg load for 15seconds. Three Vickers hardness readings were taken for each sample and the average values for the test samples were used as the illustrative values.

2.3.4 Impact strength

The impact test was carried out on samples with a Charpy impact testing system with a capacity of 15J for polymer composites and 25J for metal composites at room temperature of model number 412. Test samples with a dimension of 100.0 x 10.0 x 10.0 mm were produced in accordance with ASTM 2000. The sample was placed on the machine prior to the test and the pendulum was released to calibrate the machine. The test samples were then horizontally clenched in a vice and the freely swinging pendulum given the requisite force to crack the bar. The value of the angle at which the pendulum swung before the test sample was broken corresponded to the value of the energy that was consumed when the sample was broken and was read from the machine's calibrated scale.

3.1 Tensile Results

The effect of fiber loading in reinforced Luffa cylindrica fiber (LCF) composites on both with and without Kaolin filler(KF) was seen in Fig. 1. It was observed that the tensile strength of the composites decreases with the increase in fiber loading in both cases, i.e. with and without micro-filler. Tensile strength ranged from 9.17 to 12.11 MPa for the mono-reinforced composite whereas the hybrid composite shows values ranging from 11.46 to 15.32 MPa. It can also be observed that the maximum value of 12.11MPa was given for the mono-reinforced composites of C2 samples with 5wt of LCF with a 72.02% increase compared to the control sample C1 (0wt percent of reinforcement). While for the hybrid composite of sample C5 with 5wt% LCF and 6wt% KF gave an optimum value of 15.32 MPa compared to other filled composites with 117.61% improvement in compared to C1 and 26.51% to C5. This can be attributed to uniform particle distribution and effective adhesion of the polymer / filler interface for efficient transfer of stress. The general expression of the results indicates that the composite material developed from materials based on kaolin-luffa has a higher tensile strength than that developed from materials based on luffa. Fayomi O. et al., reported similar findings on the effect on the mechanical properties of the epoxy composite of luffa cylindrica fiber and particuJate.

3.2 Flexural strength

The flexural test measures the strength needed under three-point loading conditions for bending a beam. The data is also used to select materials for components that will carry loads without flexing. The results are as shown in Fig. 2 from which it can be seen that all the composites possess better flexural strengths than the control sample. It was also noticed that the composite of sample C7 with 15wt% LCF and 6wt% KF reinforcement displayed the best flexural strength of 120.34MPa comparing to other hybrid composites, with 183.62% and 90.7% improvement compared to control sample and sample C4 of mono-reinforce composites. Due to the uniform distribution of filler materials and improved effective bonding between filler materials and matrix and strong polymer / filler interface adhesion, the incorporation of kaolin filler into different fiber loadings of Luffa fiber composites affects the flexural strength of the composites.Similar observations have been studied in the literature of the influence of the addition of microfiller on luffa fiber-reinforced polymer composites

3.3 Impact strength

The impact test results shown in Fig. 3 indicates that in the Luffa fiber-reinforced composites materials, whether with or without Kaolin filler, fiber loading led to an improvement in the impact energy of the matrix material. It was observed that the impact energy of the composites increases with the increase in fiber loading in both cases, i.e. with and without micro-filler. Impact energy ranged from 0.15 to 0.23J/m for the mono-reinforced composite whereas the hybrid composite shows values ranging from 0.3 to 0.5 MPa. It was noted as well that for the mono-reinforced composites of samples C4 with 15wt% of LCF gave the maximum value of 0.23J/m with a 130% improvement compared to control sample C1 ( 0wt% of reinforcement). While for the hybrid composite of sample C7 with 15wt% LCF and 6wt% KF gave an optimum value of 0.5J/m compared to other filled composites with 400% improvement in compared to C1 and 117.4% to C5. The strong bonding strength between micro fillers, matrix and fiber, and stability of the molecular interface results in more energy being absorbed and distributed, and more effectively prevents cracks from initiating early. Similar observations have been studied in the literature of the influence of the addition of microfiller on luffa fiber-reinforced polymer composites.

3.4 Hardness test

Vickers hardness test has been performed on the composite samples. Figure 4 shows that compared to other filled and unfilled composites, the hardness value of hybrid composite of C7 sample with 15wt% LFC and 6wt% of KF reinforcement exhibited a maximum hardness number of 79.37 HVN. This may be attributed to the uniform dispersion of Kaolin particles and the decrease in the distance of interparticles in the matrix, which increases the indentation resistance of composites. It can be observed that with the rise in fiber filling, the hardness value of the composites increases in both cases, i.e. with and without micro-filler. Similar observations of the influence of the addition of microfiller on luffa fiber-reinforced polymer composites have been reported in the literature.

3.5 Morphological analysis

Figure 5, and Figure 6 shows the SEM micrographs of the composites material at different weight percentage composition fillers. Figure 5(A and B) indicates good compatibility between the two fillers and the matrix, good fillers dispersion within the structure and also, good interfacial bonding between the fillers and the matrix was observed. The good interaction between the fillers and the matrix observed in figure 5. confirmed the efficient stress transfer between the fillers and the matrix which resulted in the better stiffness and strength of the composite as observed in the results. Similar result were reported by Pracella et al.,(2006). Good mixing and distribution of particulate in polymer matrix at higher composition of particulate reinforcement is always associated with some difficulties which always leads to improper and poor wetting and thorough mixing of matrix and reinforcement as well as formation of air voids with the materials during and after casting. This effect can clearly be seen in the micrographs in figure 6 ( C and D). The air voids formed gave rise to the decrease in the properties of the material.

Luffa fiber reinforced polyester composites filled with or without kaolin filler were investigated. The following finding was observed;

The addition of kaolin filler in the luffa fiber matrix modifies the mechanical properties of polyester.

Hybridization of fiber and filler gives better performing composite with 5wt%LCF-2wt%KF hybrid composite showcasing the best combination for tensile strength while 15wt%LCF- 6wt%KF hybrid composite showcasing the best combination for impact energy, flexural strength, and hardness test properties.

The current study reveals the promising potential of kaolin-luffa reinforced composites for industrial lightweight engineering and outdoor applications, including automotive parts and constructional panels

Funding: self-sponsored

Conflicts of interest/ Competing interests: No conflict of interest.

Availability of data and materials: Materials are commercially available at a reasonable cost and quality result was obtained

Code availability: Not applicable

Authors’ contributions: All authors contributed significantly to the work in accordance with the order provided

Ethics approval: Not applicable

Consent to participate: Approved

Consent for publication: Approved

Aldousiri B, Shalwan A, Chin CW (2018) A review on tribological behaviour of natural reinforced composites. J Reinf Plast Compos 37:349–353. https://doi.org/10.1177/0731684417747742
Ibrahim RA (2016) Influence of natural fillers on tribological and mechanical performance of polyester composites. Int J Adv Mater Res 2:27–32
Vedrtnam A (2018) Fabrication and characterization of cow dung- Polyvinyl Alcohol composite film. Compos Commun 8:31–35. https://doi.org/10.1016/j.coco.2018.03.004
Nishino T, Hirao K, Kotera M, Nakamae K, Inagaki H (2003) Kenaf reinforced biodegradable composite. Compos Sci Technol 63:1281–1286
Senatov FS, Gorshenkov MV, Kaloshkin SD (2014) Biocompatible polymer composites based on ultrahigh molecular weight polyethylene perspective for cartilage defects replacement. J Alloy Compd 586(1):S544–S547
Harish V, Nagaiah N, Prabhu TN, Varughese KT (2009) Preparation and characterization of lead monoxide filled unsaturated polyester based polymer composites for gamma radiation shielding applications. J Appl Polym Sci 112(3):1503–1508
Azeez MA, Bello OS, Adedeji AO (2013) Traditional and medicinal uses of Luffa cylindrica: a review. J Med Plants Stud 1:102–111
Oboh IO, Aluyur EO (2001) Luffa cylindrical–an emerging cash crop. Afr J Agric Res 98:684–688
Guimaraes JL, Frollini E, Da Silva CG, Wypych F, Satyanarayana KG (2009) Characterization of banana, sugarcane bagasse and sponge gourd fibre of Brazil. J Ind Crop Prod 30:407–415
Dittenber DB, Gangarao HVS (2012) Critical review of recent publications on use of natural composites in infrastructure. Compos A 43:1419–1429
Anbukarasi K, Kalaiselvam S (2015) Study of effect of fibre volume and dimension on mechanical, thermal, and water absorption behaviour of luffa reinforced epoxy composites. Mat Des 66:321–330
Ghali L, Msahli S, Zidi M (2009) Effect of pre-treatment of Luffa fibres on the structural properties. Mater Lett 63:61–63
Tanoe VOA, Sydenstricker THD, Munaro M, Amico SC (2005) A comprehensive characterization of chemically treated Brazilian sponge-gourds (Luffa cylindrica). Polym Test 5:474–482
Thio YS, Argon AS, Cohen RE, Weinberg M (2002) Toughening of isotactic polypropylene with CaCO3 particles. Polymer 43(13):3661–3674
Baker AMM, Mead J (2000) Thermoplastics, in Modern Plastics Handbook, McGraw-Hill, Inc., 2000
Ha MH, Kim BK (2004) Effects of the viscosity ratio on polyolefin ternary blends. J Appl Polym Sci 91(6):4027–4036
Da Silva ALN, Rocha MCG, Moraes MAR, Valente CAR, Coutinho FMB (2002) Mechanical and rheological properties of composites based on polyolefin and mineral additives. Polym Testing 21(1):57–60
Al-Asade JZ, Al-Murshdy MJ (2008) An Investigation of Kaolin Influences on Mechanical properties of Unsaturated polyester composites. journal of Kerbala University 5:1–6
Ahmed NM, Tawfik ME, Ward AA (2013) Characterization of a polymer composite from treated kaolin and unsaturated polyester based on PET waste. Polymer composites 34(8):1223–1234
Sakthivel M, Vijayakumar S, Ramesh S (2014) Production and characterization of Luffa/coir reinforced polypropylene composite. Procedia Mater Sci 5:739–745
Srinivasan C, Sathish S, Vignesh K (2014) Mechanical propertiesmof chemically treated Luffa Aegyptiaca fiber reinforced epoxy matrix composites. Int J Sci Res Manag (IJSRM) 2(10):1515–1524
Panneerdhass R, Gnanavelbabu A, Rajkumar K (2014) Mechanical properties of Luffa Fiber and ground nut reinforced epoxy polymer hybrid composites. Procedia Eng 97:2042–2051. https://doi.org/10.1016/j.proeng.2014.12.447
Daniel-Mkpume CC, Ugochukwu C, Okonkwo EG, Fayomi OSI, Obiorah SM (2019) Effect of Luffa cylindrica fiber and particulate on the mechanical properties of epoxy. Int J Adv Manuf Technol 17(19):3422

PDF

Reviews received at journal
31 Mar, 2021
Reviewers invited by journal
16 Mar, 2021
Editor assigned by journal
16 Mar, 2021
First submitted to journal
16 Mar, 2021

You are reading this latest preprint version

Influence of kaolin filler on the mechanical properties of Luffa cylindrica/ polyester composite

Status:

Version 1

Abstract

Figures

1. Introduction

2. Experimental Detail

2.1. Materials and quipment

2.1. Reinforcement preparation

2.2. Composite fabrication

2.3 Mechanical Testing

2.3.1 Tensile strength result

2.3.2 Flexural strength result

2.3.3 Hardness Test

2.3.4 Impact strength

3. Results And Discussion

3.1 Tensile Results

3.2 Flexural strength

3.3 Impact strength

3.4 Hardness test

3.5 Morphological analysis

4. Conclusions

Declarations

References

Status:

Version 1