Vollastonit ve Manyetit Katkılı Rijit Poliüretan Köpüklerin Isıl Geçiş ve Mekanik Özellikleri

Öz

Poliüretan (PU) köpüklerin sahip olduğu düşük mekanik ve termal iletkenlik özelliklerine karşın işleme kolaylığı ve sert/esnek olarak üretilebildiklerinden dolayı otomotiv, yalıtım ve yapıştırıcı gibi uygulamalarda tercih edilen malzemelerdir. Sert poliüretan köpükler ise sahip oldukları düşük yoğunluk ve kapalı hücre yapısı özelliklerinden dolayı otomotiv, gemi ve inşaat sektörlerinde kullanılan malzemelerdir. Son yıllarda, farklı katkılarla takviye edilmiş olan poliüretan köpüklerin morfolojik, mekanik ve iletkenlik özellikleri gibi çeşitli özellikleri yoğun bir şekilde araştırılmaktadır. Ancak manyetit/vollastonit hibrit sistemlerin sert PU köpük kompozitlerin termal geçiş ve mekanik özellikleri üzerindeki etkisi henüz araştırılmamıştır. Bu çalışmanın amacı vollastonit (W) ve manyetit (M) takviyeli sert poliüretan köpüklerin termal geçiş sıcaklıkları ve mekanik özelliklerinin incelenmesidir. Köpüklerin mekanik ve termal geçiş özellikleri arasındaki ilişkiler ve özellikle manyetit/vollastonit (1:3, 1:1 ve 3:1) hibrit sistemlerin ağırlık oranlarının PU köpük özelliklerine etkisi incelenmiştir. Üretilen köpükler Fourier dönüşümlü kızılötesi spektrometre, diferansiyel taramalı kalorimetre ve çekme testi cihazı ile karakterize edilmiştir. Yapılan çalışmalar sonucunda, poliüretan köpüklerin kimyasal yapısının katkılardan (manyetit ve vollastonit) etkilenmediği tespit edilmiştir. Termal geçiş sonuçları iki ana davranışın varlığını ortaya çıkarmıştır. İlk durumda, sert segmentlerin camsı geçiş sıcaklığında genel bir artış gözlemlenmiştir ve bu davranış, polimer zincirleri arasında manyetit ve vollastonit partiküllerinin eklenmesinden dolayı poliüretan zincirlerinin hareketliliğinin azalması ile açıklanabilir. İkinci durumda, yumuşak segmentlerin camsı geçiş sıcaklığında gözlemlenen genel bir düşüş eğilimi, muhtemelen polimer matrisinde manyetit veya vollastonitin varlığından dolayı, polimer zincirleri arasında düğüm oluşumunun engellenmesinden kaynaklanmaktadır. Sert PU köpüklerde, vollastonitin manyetite göre çekme dayanımı özelliklerine daha belirgin bir olumsuz etkisinin olduğu görülmektedir.

Anahtar Kelimeler

• Rijit Poliüretan Köpük
• Vollastonit
• Manyetit
• Termal Geçiş
• Mekanik Özellikler

Thermal Transition and Mechanical Properties of Magnetite and Wollastonite Filled Rigid Polyurethane Foams

Abstract

Polyurethane (PU) foams, despite their low mechanical and thermal conductivity properties, are preferred materials in applications such as automotive, insulation and adhesives because of their ease of processing and their possibility to be produced as rigid/flexible materials. Rigid polyurethane foams are materials used in the automotive, ship and construction industries due to their low density and closed cell structure. In recent years, various properties of polyurethane foams reinforced with different additives, such as morphological, mechanical and conductive properties, have been extensively investigated. However, the effect of magnetite/wollastonite hybrid systems on thermal transition and mechanical properties of rigid PU foam composites was not studied yet. The aim of this work is to explore thermal transition temperatures and mechanical properties of wollastonite (W) and magnetite (M) filled rigid polyurethane foams. The relationships between mechanical and thermal transition properties of the foams and in particular, the effect of the weight ratio of magnetite/wollastonite (1:3, 1:1 and 3:1) hybrid systems on the PU foam properties were studied. The foams produced were characterized by a Fourier transform infrared spectrometer, differential scanning calorimeter and tensile test device. As a result of the studies, it has been determined that the chemical structure of polyurethane foams is not affected by additives (magnetite and wollastonite). Thermal transition results revealed the presence of two main behaviors. In the first case an overall increase of the glass transition temperature of hard segments is observed and this behavior can be explained by the diminution of the mobility of polyurethane chains with the inclusion of magnetite and wollastonite particles between polymer chains. In the second case a general decrease tendency of the glass transition temperature of soft segments is obtained probably due to the presence of magnetite or wollastonite into the polymer matrix which hinders the formation of entanglements of polymer chains. A more important negative impact of wollastonite is observed in tensile properties of rigid PU foams compared to magnetite.

Keywords

• Rigid Polyurethane Foam
• Wollastonite
• Magnetite
• Thermal Transition
• Mechanical Properties

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