Tham, Wei Ling (2015) Preparation And Properties Of Poly (Lactic Acid) Halloysite Nanotube Nanocomposites. PhD thesis, Universiti Sains Malaysia.
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Abstract
Dalam penyelidikan ini, nanotiub haloisit (HNT) telah digunakan untuk meningkatkan sifat-sifat poli(asid laktik) (PLA). Nanokomposit PLA/HNT telah disediakan dengan kaedah penyebatian leburan diikuti oleh pengacuan mampatan. Tiga jenis pengubahsuai hentaman, iaitu kopolimer stirena-etilena/butilena-stirena tercantum maleik anhidrida (SEBS-g-MA), N,N’-etilenabis(stearamida) (EBS), dan getah asli terepoksida (ENR) telah digunakan untuk memperliat nanokomposit PLA. Sifat-sifat nanokomposit PLA/HNT telah dicirikan oleh ujian mekanik (ujian tegangan, lenturan, hentaman), analisis termal (kalorimetri pengimbasan pembezaan (DSC) dan analisis termogravimetri (TGA)), analisis morfologi (iaitu ujian mikroskopi elektron imbasan pancaran medan (FESEM) dan mikroskopi elektron pemancaran (TEM)), dan spektroskopi inframerah jelmaan Fourier (FTIR). Kekuatan hentaman bagi nanokomposit PLA/HNT telah meningkat sebanyak 300% dengan penambahan 15 wt% ENR. Dengan penambahan EBS dan ENR, HNT yang terserak halus dapat meningkatkan kesan penukleusan dan membantu dalam proses penghabluran bagi PLA. Walau bagaimanapun, penambahan SEBS-g-MA dan HNT melambatkan pembentukan kumin hablur yang bersaiz besar di dalam PLA. Kinetik penyerapan air bagi nanokomposit PLA/HNT adalah mengikut kelakuan hukum resapan Fickian pada suhu rendaman 30oC dan 40oC. Bagi sampel terdedah kepada 50oC, penyerapan air mematuhi hukum Fick di peringkat awal. Namun, semakin lama direndam, sampel tersebut didapati tidak lagi mematuhi hukum Fick dan kehilangan berat berlaku. Hal ini disebabkan oleh hidrolisis PLA pada suhu rendaman yang tinggi yang telah disahkan melalui perubahan pH, pengurangan berat molekul, peningkatan nilai-nilai indeks karbonil (CI), dan perubahan sifat termal. Daripada keputusan TGA, didapati bahawa penguraian tunggal berlaku ketika keadaan nitrogen, manakala proses penguraian dua-peringkat telah berlaku dalam keadaan oksigen. Penambahan EBS dan ENR dapat meningkatkan kestabilan termal bagi PLA/HNT di bawah keadaan oksigen. Nanokomposit PLA/HNT6/ENR5 mempunyai kestabilan termo-beroksida yang tinggi di bawah atmosfera oksigen. Selain itu, penambahan 5 wt% ENR dalam nanokomposit PLA/HNT6 menganjakkan suhu permulaan pengoksidaan (OOT) kepada suhu yang lebih tinggi (dari 239.5oC kepada 296.5oC). Nanokomposit PLA/HNT6/ENR5 telah menunjukkan nilai pekali kebolehtelapan oksigen ( O2 P ) yang terendah (1.567x10-4 cm3.m.m-2.day-1.kPa-1). Walau bagaimanapun, penambahan SEBS-g-MA tidak dapat meningkatkan sifatsifat halangan gas oksigen bagi nanokomposit PLA/HNT. Daripada analisis spektroskopi UV-Vis, penambahan pengubahsuai hentaman di dalam nanokomposit PLA/HNT telah mengurangkan penembusan cahaya dan hampir tiada cahaya UV dihantar melalui filem pada 300 nm. Namun, kesemua nanokomposit PLA/HNT kekal lutsinar melalui pengamatan visual. Kesimpulannya, penambahan ENR dalam nanokomposit PLA/HNT dapat meningkatkan sifat-sifat nanokomposit polimer secara efektif dari segi kekuatan hentaman, tenaga pengaktifan resapan air (Ea), OOT, dan ciri-ciri halangan gas oksigen. ________________________________________________________________________________________________________________________ In this research, halloysite nanotube (HNT) was used to improve the properties of poly(lactic acid) (PLA). The PLA/HNT nanocomposites were prepared using melt compounding followed by compression molding. Three types of impact modifiers i.e., maleic anhydride grafted styrene-ethylene/butylene-styrene copolymer (SEBS-g- MA), N,N’-ethylenebis(stearamide) (EBS), and epoxidized natural rubber (ENR), were used to toughen the PLA nanocomposites. The properties of PLA/HNT nanocomposites were characterized by mechanical tests (i.e., tensile, flexural, and impact tests), thermal analysis (i.e., differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)), morphological analysis (i.e., field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM)), and Fourier transform infrared spectroscopy (FTIR). The impact strength of PLA/HNT nanocomposites was increased significantly to approximately 300% by the addition of 15 wt% ENR. A finely dispersed HNT could eventually increase its nucleation effect and assist in the crystallization process of PLA whilst in the presence of EBS and ENR. Nevertheless, the presence of SEBS-g-MA and HNT retard the formation of large crystallites of PLA. The kinetics of water absorption of PLA/HNT nanocomposite fitted Fickian diffusion behaviour at immersion temperatures of 30oC and 40oC. For the samples exposed to 50oC, the water uptake followed Fick's law during the initial stages, but at longer time periods, deviations and weight loss were observed. This may have been due to the hydrolysis of PLA at higher immersion temperatures, which was confirmed by the pH change, reduction of molecular weight, increase in carbonyl index (CI) values, and thermal property changes. From the TGA results, it was found that single decomposition took place in the nitrogen atmosphere, while a double-stage decomposition process occurred in the oxygen atmosphere. The incorporation of EBS and ENR could improve the thermal stability of PLA/HNT under oxygen atmosphere. The PLA/HNT6/ENR5 nanocomposites exhibited high thermo-oxidative stability under oxygen atmosphere. Furthermore, the addition of 5 wt% of ENR in PLA/HNT6 nanocomposites increased the oxidation onset temperature (OOT) (from 239.5oC to 296.5oC). The PLA/HNT6/ENR5 showed the lowest oxygen permeability coefficient ( O2 P ) value of approximately 1.567x10-4 cm3.m.m-2.day-1.kPa-1. However, the incorporation of SEBS-g-MA could not improve the oxygen gas barrier properties of PLA/HNT nanocomposites. From the UV-Vis spectroscopy analysis, the incorporation of impact modifiers in PLA/HNT nanocomposites decreases light transmittance and nearly no UV light can be transmitted through thin film at 300 nm. Nevertheless, all PLA/HNT nanocomposites remain transparent from visual view. In summary, the addition of ENR in PLA/HNT nanocomposites can effectively improve the properties of polymer nanocomposites in term of impact strength, activation energy of water diffusion (Ea), OOT, and oxygen gas barrier properties among the others impact modifiers.
| Item Type: | Thesis (PhD) |
|---|---|
| Additional Information: | Full text is available at http://irplus.eng.usm.my:8080/ir_plus/institutionalPublicationPublicView.action?institutionalItemId=2865 |
| Subjects: | T Technology T Technology > TN Mining Engineering. Metallurgy > TN263-271 Mineral deposits. Metallic ore deposits. Prospecting |
| Divisions: | Kampus Kejuruteraan (Engineering Campus) > Pusat Pengajian Kejuruteraan Bahan & Sumber Mineral (School of Material & Mineral Resource Engineering) > Thesis |
| Depositing User: | Mr Mohd Jasnizam Mohd Salleh |
| Date Deposited: | 12 Jul 2018 07:28 |
| Last Modified: | 16 Aug 2018 08:06 |
| URI: | http://eprints.usm.my/id/eprint/41014 |
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