Effect Addition of Octadecylamine Modified Clay (ODA-MMT) to

Polylactide/Polycaprolactone (PLA/PCL) blend

SITI ZULAIHA Hairaldin1,a, WAN MD ZIN Wan Yunus2,b

and NORAZOWA Ibrahim2,c

1Malaysian Nuclear Agency, Bangi, 43000 Kajang, Malaysia

2Department of Chemistry, Faculty of Science, Universiti Putra Malaysia,

43400 UPM Serdang, Selangor, Malaysia

asitizulaiha@nuclearmalaysia.gov.my, bwanzin@science.upm.edu.my,

cnorazowa@science.upm.edu.my

Keywords: Nanocomposites, Polylactide, Polycaprolactone, Organoclay, Octadecylamine, Melt

Blending, SEM Analysis

Abstract. In this study, Octadecylamine Modified montmorillonites (ODAMMT) were used to prepare polylactide/polycaprolactone (PLA/PCL) clay nanocomposites. PLA and PCL were blend using an internal mixer by melt blending method. The other sample was blend with natrium monmorillonite (NaMMT) and Octadecylamine modified monmorillonite to produce PLA/PCL-NaMMT and PLA/PCL-ODAMMT. To characterize the polymer nanocomposite, X-ray diffraction (XRD), FTIR and SEM analysis were conducted. Comparison of morphology were made up between neat PLA/PCL, PLA/PCL with presence of of montmorillonite and octadecylamine modified monmorillonite respectively based on SEM micrograph. The number-average diameter was calculated for PLA/PCL, PLA/PCL-NaMMT, and PLA/PCL-ODAMMT.

Introduction.

Nanocomposites are materials that are created by introducing particulates into a macroscopic sample material or the matrix. Clay are widely use as a filler for polymer consumption and reduce cost. One of the types is Monmorillonite (NaMMT). NaMMT is a hydrophobic compound so it must be modified to an exchange of inorganic cations [1]. It has been known that PLA and PCL is a biodegradable polymer. Combination of PLA/PCL is successfully exhibited higher fracture properties than neat PLA. Several research has been done on PLA/PCL blend, however based on previous study, 90:10 ratio of PLA:PLA show a great mechanical property [2] when compared to other ratio [3,4,5]. However immiscibility of PLA and PCL prevents the blend from further improvement of the fracture properties. ODA-MMT is one of commercial surfactant widely used in producing nanocomposite. In this study, ODA-MMT was chosen and introduced to PLA/PCL blend to improve the immicibility. The fracture properties were evaluated by calculating the average number diameter (dn) spherulites based on scanning electron Microscopy (SEM) micrograph. The dn was calculated from an average minimum of 50 particles as studied by Jiang, 2007 [6].

Experimental Method.

Preparation of ODA-MMT. MMT suspend in distilled water (80 0C, 1 hr), ODA was added and stirred. The mixture filtered and washed with hot distilled water then undergo for Chloride test with AgNO3. The step repeated until no chlorine detected. The mixture dry in oven, grind and sieved at 200 micrometer to produce modified clay (ODAMMT).

Preparation of (PLA/PCL) nanocomposites. Preparations of PLA/PCL nanocomposites were carried out by melt blending using a Haake internal mixer at 1800C and a speed rate of 60 rpm. PLA were dried overnight at 600C under vacuum to remove residual water. PLA was first transferred into

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the mixer and heated at the blending temperature for 5 minutes. PCL was then added the melt PLA and allowed to mix for 5.0 minutes. This was then followed by the addition of the ODA-MMT to the blend. To prepare the sample sheets, the composites were compressed molded in a hot press at 1650C for 10 minutes.

Characterization of PLA/PCL-ODAMMT nanocomposite. X-ray diffraction (XRD) analysis of samples was performed to evaluate the d-spacing of clay layers, by using Powder X-ray Diffraction (PXRD-6000, Shimadzu. Japan. FTIR 1650 Spectrum BX (Perkin-Elmer, England) was used to determine the functional groups in compounds. Scanning Electron Microscopy (SEM, JSM-6360LA. JEOL, Japan) was used to observe the tensile fractured surface morphology of nanocomposites. The microstructure of nanocomposites was observed using Transmission Electron Micrograph (TEM, Hitachi H-7100).

Fig.1: The XRD pattern of Na-MMT and ODA-MMT

318 Nanomaterials

0

100

200

300

1000200030004000

464

5263626

463

522

1469

2921

34303627

1467

2850

2919

3432

Na-MMT

ODA

ODA-MMT

Fig.2: FTIR spectrum of (a) ODA (b) Na-MMT and ODA-MMT

Results & Discussion.

XRD Analysis. The XRD pattern of Na-MMT and ODA-MMT are shown in Figure 1. The Na-MMT diffractrogram shows a clear peak at 2θ of 7.26θ corresponding to the characteristic peak of Na-MMT. After modification, interlayer galleries spacing of ODA-MMT is increases from 11.62 Å to 29.90 Å and the basal peak position in XRD shifts to smaller position from 7.26θ to 2.94θ. Increment of d-spacing can be explained by intercalation of ODA into the interlayer galleries of Na-MMT forming ODA-MMT. The intercalation agent increase interlayer spacing leading shift toward lower angle.

FTIR Analysis. The Fourier Transform Infra Red (FTIR) spectra of Na-MMT, ODA and ODA-MMT are shown in Figure 2. The 3432 cm-1 for N-H stretching, 2919 cm-1 and 2850 cm-1 for C-H stretching, 1467 cm-1 attributed to N-H stretching. After modification of Na-MMT and ODA, the absorption peak becomes 2918 cm-1 attributed to C-H stretching from Na-MMT. The absorption peaks at 2921 cm-1 and 2851 cm-1 attributed to C-H stretching and NH4 at 1469 cm-1 because presence of ODA.

Morphology. Figure 3 shows SEM micrograph of the fracture surfaces of PLA/PCL, PLA/PCL-Na-MMT, and PLA/PCL-ODAMMT. In Figure 3(a) which is neat PLA/PCL show a blend which have non-uniform PCL spherulites and many voids are observed. The dispersed suggested as spherulites with a average number diameter (dn) is about 3.2 µm. While for PLA/PCL-NaMMT (Figure (3(b)), the spherulites size is decrease with addition of Na-MMT become about 1.4 µm. The small particle size should relate to presence of Na-MMT. However after the addition of ODAMMT in PLA/PCL, the spherulites are almost disappeared. This is considered due to decrease of the size of the PCL sperulites by ODA-MMT addition. ODA-

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Fig.3: Morphology of (a) PLA/PCL (b) PLA/PCL-NaMMT (c) PLA/PCL-ODAMMT at 150,000X

magnifications

MMT tends to relax local stress concentrations in the crack-tip region to decrease void formation [7]. This suggested that the PLA/PCL-ODAMMT nanocomposite is more compatible compared to PLA/PCL and PLA/PCL containing Na-MMT. ODA-MMT clay can also plays a role like a compatibilizer. This phenomenon may mainly be due to the intercalation of polymer molecules in nanocomposites which increases the viscosity ratio and results in the retardation of dispersed phase-separated [8].

TEM Analysis. The Transmission Electron Microscopy (TEM) micrographs of PLA/PCL-

ODAMMT at 150,000x magnifications were shown in Figure 4. Figure marked intercalated as

white arrows and exfoliated as black arrows of nanocomposite. The dark lines represent the silicate

layers and the gray bases are the PLA/PCL polymer matrix.

(a) (b)

(c)

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Fig.4: TEM micrograph PLA/PCL-ODAMMT composite at 150,000X magnifications

Conclusion

PLA/PCL-NaMMT and PLA/PCL-ODAMMT was successfully prepared. After modification of clay basal spacing of ODA-MMT increase from 11.62 A to 29.90 A. Presence of modified clays was confirmed by FTIR spectrums. SEM micrograph show that size of spherulites reduced in sample PLA/PCL>PLA/PCL-NaMMT>PLA/PCL-ODAMMT. PLA/PCL has better compability with presence of ODA-MMT. The results show that introducing the ODA-MMT into PLA/PCL system will enhance morphology of nanocomposites and ODA-MMT can also play a role like a compatibilizer.

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