The use of bentonite of Bener Meriah Aceh to improve the mechanical properties of Polypropylene-Montmorillonite Nanocomposite

The research on application of bentonite Bener Meriah of Aceh to improve the mechanical properties of polypropylene-montmorillonite nanocomposite has been conducted. Bentonite was isolated into the nano-sized montmorillonite and was used as a filler of polypropylene-montmorillonite nanocomposites with the addition of PP-g-MA as a compatibilizer and octadecylamine as a modifier of MMT. The results showed that bentonite of Bener Meriah Aceh contained montmorillonite with 70.6% content. Based on the result of mechanical properties test, it was ddiscovered that montmorillonite isolated from Bentonite of Bener Meriah could improve the mechanical properties of PP-MMT nanocomposite in composition ratio of PP/PP-g-MA/MMT is 85/10/5.


Introduction
Bentonite is an abundant natural resource in Indonesia, such as in Java, Sumatra, and Sulawesi, which contain more than 380 million tons but has not been optimally utilized. In Aceh, natural bentonite can be found in the districts of North Aceh, Bener Meriah, Sabang, Central Aceh, and Simeulue [1,2,3] which reaches the amount of 2,618,224,030.20 tons [4]. To date, research on Aceh bentonite has been conducted only on several studies [5] and the bentonite that has been used only the one that found in North Aceh. Therefore, bentonite processing from other districts in Aceh is required. Bentonite that will be used in this research is bentonite from Bener Meriah, which is one of the areas in the Province of Aceh which has bentonite with a thickness of 1 m width of 20 Ha and its content reaches 520,000 tons [4] which has not been utilized. Bentonite is natural clay whose main component is the mineral montmorillonite (85%), with the chemical formula of Mx(Al4-xMgx)Si8O20(OH)4.nH2O. Montmorillonite (MMT) is a filo-silicate mineral that has the ability to expand and can be intercalated and exfoliated, thus it is widely used as filler of nanocomposite to enhance the properties of the nanocomposite [6]. When an exfoliation occurs, the mechanical and rheological properties of the nanocomposite increase dramatically when compared with the pure polymer [7]. Several researches on the addition of MMT in polypropylene (PP) nanocomposites has been conducted and indicated that MMT can improve some of these nanocomposite properties such as mechanical properties [8,9,10,11,12], thermal properties [13], fire retardancy properties [14], and increased degrees of degradation [16]. It is expected that MMT from Bener Meriah can also be used to improve the mechanical properties of nanocomposites.
Nanocomposites can be obtained by mixing the silicate layers of MMT with PP by melting intercalation method. Mixing of silicate layers from MMT in PP can be increased by using functional oligomers as compatibilizers. Several studies have reported using polypropylene-graft-maleic anhydride (PP-g-MA) as a compatibilizer [15].MMT is also modified using a long organic alkyl chain, which is called a modified organo-silicate layer (OMLS) or organo-clay.The organic clay will change the hydrophilic into hydrophobicproperties of MMT, which is allowing the MMT interface to interact with several different polymer matric.The Organic compounds commonly used to modify MMT are alkynammonium. The research was conducted several stages are characterizing of bentonite, isolationof the MMT nanoparticle, preparation and characterize of PP-MMT nanocomposites.

Methods 2.2.1. Isolation nano montmorillonite from natural bentonite Bener Meriah.
Montmorillonite nanoparticles can be obtained by preparing 1 kg of bentonite sample and filtered with a 100 mesh sieves, then it was dried in oven at the temperature of 105 °C for 4 hours. Subsequently, the sample was fractionated. Fractionation was done with sedimentation by weighing 40 grams of 100 mesh bentonite and added with 2L aquades to form the suspension. Bentonite suspension was given ultrasonic waves for 15 minutes at 750 watts at room temperature. Furthermore, the suspension is left in a flat place and kept away from all vibrations. Precipitation that occur within 15 minutes are taken by pouring the suspension into another container and leaving the filtrate again.The precipitate formed in the next 3 days is filtered back and taken its filtrate. The floating fraction in the filtrate is stirred again, then the filtrate is left for a week and collected of precipitate is formed. This precipitate was dried in an oven at 105 °C for 3 hours, then crushed and sieved using 200 mesh sieve. This fraction is stored in a desiccator. The identification of the fraction (montmorillonite) was carried out using FT-IR, X-RD diffraction and SEM [16].

Preparation of polypropylene-montmorillonite nanocomposite (PP-MMT).
Variation of the composition materials of PP, PP-g-MA, and montmorillonite for preparing PP-MMT nanocomposite can be seen in Table 1. Materials of various compositions of PP, PP-g-MA and montmorillonite were coumpounded respectively in a Haake Rheomix 3000 internal laboratory mixer with high rotor intensity, operating at 180 °C at 65 rpm for 10 minutes. Samples for mechanical tests were made from the nanocomposite produced.

Characterization
Samples of bentonite and nano montmorillonite were characterized by X-Ray Flourencense (XRF) PANalytical, Axios Advance. The percentage of montmorillonite be calculated using the Meyer equation [17]. The functional group of bentonite, nano montmorillonite and nanocomposite speciment were analyzed by using FTIR of Perkin Elmer type spectrum 100 at wave numbers 400 to 4000 cm -1 . The X-Ray Diffraction scattering patterns of bentonite, nano montmorillonite and nanocomposite were recorded using XRD Shimadzu 6000, operating at Cu Kα radiation generated at 40kV and 30 mA. The sample were scanned in range of 3° to 50° with scan rate 5°(2θ)/minute. Surfaces morfologies of nano montmorillonite and nanocomposite was analyzed by Scanning Electron Microscopy (SEM) Merck Zeiss type EVO MA 10 at 20 kV. Mechanical tests was done using the equipment a Lloyd LR/10KN Universal, operation at room temperature and a speed of 50 mm min -1 , according to ASTM D638 and ASTM D256 standard. Nanoparticle was analyzed by Particle Size Analyzer (PSA) of LS 100 Q Coulter.

Result and discussion
3.1. XRF analysis XRF analysis was chosen asa method for the assessment of the quantitative results. The result of characterization of bentonite of Bener Meriah Aceh by XRF can be seen in Table 2. Table 2 shows the chemical composition of bentonite from Bener Meriah, the amount of Na2O is greater than CaO, this indicates that the bentonite from Bener Meriah is Na-Bentonite as described in [18].

3.2.Meyer test
The content of montmorillonite in Bener Meriah bentonite was analyzed using the Meyer equation, (1972) and the result was 70.6%. The percentage of montmorillonite is different for each region, it is also suspected to be influenced by the process of bentonite formation refer to [18]

XRD analysis
The characterization of sample by X-Ray Diffraction (XRD) aimed to verify the existence minerals of Bentonite Bener Meriah and about exfoliation and intercalation of PP-MMT nanocomposite. The XRD patterns of bentonite Bener Meriah can be seen in Figure 2.  [16,21]. In addition, the peak of 2θ at 5.86 o and 16.29 o in the Figure 2 showed that bentonite of Bener Meriah is Na-bentonite [22]. The XRD patterns of montmorillonite show only peak of 2θ : 5.47°; 14.54°; 25.25°, 35.04°, which is the result of isolation from bentonite of Bener Meriah [23]. The pattern XRD of the PP-MMT nanocomposite in the composition ratio of PP/ PP-g-MA/ MMT is 85/ 10/ 5 showed peak of 2θ at 2.4 to 2.7 o , that indicates that PP chains insert into the interlayers of MMT and hence the polymer intercalated or exfoliated structure is achieved [24].
In addition, angular shifts from the top of MMT also explain the occurrence of intercalation and exfoliation in the silicate layer.

SEM analysis
The Scanning Electron Microscopic (SEM) technique was used to explore the surface morphologies of the sample. Figure 3(A) shows the surface morphologies of montmorillonite which isolated from bentonite Bener Meriah.The figure showed that structure of MMT Bener Meriah has layered pores which randomly distributed with different sizes [25,26]. The existence of these layered pores causes MMT to be used as a nanocomposite filler to enhance the properties of the nanocomposite. Figure 3

PSA analysis
Montmorillonite which has isolated from bentonite was processed into nanoparticles by precipitation [16]. To analyze particle size of montmorillonite was used Particle Size Analyzer. The average result of particle size of montmorillonite Bener Meriah was 67,8 nm, can be seen in Figure 4. Then, this montmorillonite was used to preparation of nanocomposite.

Conclusion
It can be concluded that bentonite is Na-bentonit and has percentage of montmorillonite of 70.6%. Bentonite Bener Meriah was isolated into nano-sized montmorillonite and used as a filler of polypropylene-montmorillonite nanocomposites by the addition of PP-g-MA as a compatibilizer and octadecylamine as a modifier of MMT. The result indicates that exfoliation and intercalation of PP in MMT may occur to produce compatible nanocomposites. Based on mechanical properties test, it showed