Dispersion-Controlled Thermal Degradation Kinetics of PMMA/NiFe₂O₄ Nanocomposites Prepared with Different Mixing Times

Öz

The thermal degradation behavior of polymer nanocomposites is strongly governed by nanoparticle dispersion; however, the relationship between dispersion homogeneity and degradation kinetics remains unclear. In this study, PMMA/NiFe₂O₄ nanocomposites were prepared using controlled melt mixing with different mixing times in order to systematically investigate the role of dispersion state on thermal degradation kinetics. Structural and morphological characterization was carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM), while non-isothermal differential thermal analysis (DTA) was employed at multiple heating rates to evaluate degradation behavior. XRD results confirmed that the incorporation of NiFe₂O₄ nanoparticles did not alter the amorphous structure of the PMMA matrix. SEM analysis revealed that prolonged mixing significantly improved nanoparticle dispersion, whereas shorter mixing resulted in partial agglomeration. Despite comparable degradation peak temperatures for all samples, pronounced differences were observed in degradation kinetics. Activation energies calculated using Kissinger, Ozawa, and Augis–Bennett methods demonstrated that the PMMA-6 nanocomposite exhibited the highest activation energy (~270 kJ/mol), representing an increase of approximately 30% compared to neat PMMA and ~25% compared to the more homogeneously dispersed PMMA-12 sample. These results indicate that maximum nanoparticle dispersion does not necessarily correspond to maximum thermal resistance. Instead, an optimum dispersion state characterized by partial agglomeration and enhanced interfacial constraint governs the thermal degradation kinetics of PMMA/NiFe₂O₄ nanocomposites. This study highlights the critical role of processing-controlled dispersion in tailoring the thermal performance of polymer nanocomposites without inducing structural changes.

Anahtar Kelimeler

• Poly(methyl methacrylate)
• Thermal analysis
• NiFe2O4
• Activation energy
• Kissinger
• Takhor
• Augis-Bennett

Farklı Karıştırma Süreleriyle Hazırlanan PMMA/NiFe₂O₄ Nanokompozitlerinde Dağılım Kontrollü Termal Bozunma Kinetiği

Öz

Polimer nanokompozitlerin termal bozunma davranışı büyük ölçüde nanoparçacık dağılımı tarafından belirlenmektedir; ancak dağılım homojenliği ile bozunma kinetiği arasındaki ilişki henüz tam olarak açıklığa kavuşmamıştır. Bu çalışmada, farklı karıştırma süreleri kullanılarak kontrollü ergiyik karıştırma yöntemiyle hazırlanan PMMA/NiFe₂O₄ nanokompozitlerinde dağılım durumunun termal bozunma kinetiği üzerindeki etkisi sistematik olarak incelenmiştir. Yapısal ve morfolojik karakterizasyon X-ışını kırınımı (XRD) ve taramalı elektron mikroskobu (SEM) ile gerçekleştirilmiş; bozunma davranışının değerlendirilmesi için farklı ısıtma hızlarında izotermal olmayan diferansiyel termal analiz (DTA) uygulanmıştır. XRD sonuçları, NiFe₂O₄ nanoparçacık ilavesinin PMMA matrisinin amorf yapısını değiştirmediğini göstermiştir. SEM analizleri, uzun karıştırma sürelerinin nanoparçacık dağılımını belirgin şekilde iyileştirdiğini, daha kısa karıştırma sürelerinin ise kısmi aglomerasyona yol açtığını ortaya koymuştur. Tüm numunelerde bozunma pik sıcaklıkları benzer olmasına rağmen, bozunma kinetiğinde belirgin farklılıklar gözlenmiştir. Kissinger, Ozawa ve Augis–Bennett yöntemleri kullanılarak hesaplanan aktivasyon enerjileri, PMMA-6 nanokompozitinin en yüksek aktivasyon enerjisine (~270 kJ/mol) sahip olduğunu ve bu değerin saf PMMA’ya kıyasla yaklaşık %30, daha homojen dağılıma sahip PMMA-12 numunesine kıyasla ise yaklaşık %25 daha yüksek olduğunu göstermiştir. Elde edilen sonuçlar, maksimum nanoparçacık dağılımının her zaman maksimum termal dayanım anlamına gelmediğini ortaya koymaktadır. Bunun yerine, kısmi aglomerasyon ve artmış arayüzeysel kısıtlamalarla karakterize edilen optimum bir dağılım durumunun PMMA/NiFe₂O₄ nanokompozitlerinin termal bozunma kinetiğini belirlediği görülmüştür. Bu çalışma, yapısal değişime neden olmaksızın polimer nanokompozitlerin termal performansının ayarlanmasında işlem koşullarıyla kontrol edilen dağılımın kritik rolünü vurgulamaktadır.

Anahtar Kelimeler

• Poly(methyl methacrylate)
• Thermal analysis
• NiFe₂O₄
• Activation energy
• Kissinger
• Takhor
• Augis-Bennett

Kaynakça

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