The role of thermal treatment on themorphology and phase behaviour ofhigh hard block content thermoplastic polyurethanes
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- Tez No: 715413
- Danışmanlar: Belirtilmemiş.
- Tez Türü: Yüksek Lisans
- Konular: Metalurji Mühendisliği, Metallurgical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2017
- Dil: İngilizce
- Üniversite: The Unıversıty Of Manchester
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
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Özet (Çeviri)
Thermoplastic polyurethanes (TPUs) are defined as linear di-block copolymers consisting of statistically-alternating hard segments (HS) and soft segments (SS). Due to their various application areas, considerable attention has been aroused to these materials. The excellent properties of TPUs are generally ascribed to their microphase-separated nature resulting from the thermodynamic incompatibility between hard segments and soft segments. The effect of different thermal treatments (melt-quenched, isothermally annealed) on the micro phase separation, crystallinity and mechanical properties of the 70 % HS (w/w) TPUs has been investigated. The SS was based on poly(propylene oxide), end capped with ethylene oxide (EO-PPO-EO), and the HS on a 4,4'-methylene diphenyldiisocyanate (MDI) chain extended by 1,5-pentanediol (15PD). By correlating the TGA results with GPC results, it has been concluded that no considerable degradation was presented by our samples. Two high temperature melting endotherms were observed on the DSC thermographs of the meltquenched samples. Lower temperature endotherm was attributed to melting of the crystallites residing on the HS, while higher temperature endotherm was considered to belong to the microphase mixing of the two segments. High temperature endotherms of the melt-quenched samples shifted to higher temperatures upon annealing suggesting increased phase separation due to annealing process. DMTA experiments provided further support to this interpretation by indicating that young modulus and HS glass transition temperature (𝑇𝑔𝐻𝑆) of the melt quenched samples was increased by annealing due to better phase separation. Increased mechanical properties by annealing were also observed on the tensile testing. FTIR measurements provide evidence that the increase in the 𝑇𝑔𝐻𝑆 of the melt quenched sample due to annealing was not caused by the increase in the strength of the hydrogen bonding. WAXS spectrum of the melt-quenched sample revealed that these materials were amorphous. Crystallinity of these materials was seen to have increased by annealing and positive correlation was found between the annealing time and the extent of crystallinity.
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