Photooxidative Stability of Polyurethane/Polycarbonate Blends

E Govorčin Bajsić

doi:10.15255/cabeq.2017.1196

Abstract

In this work the photooxidative stability of polyurethane/polycarbonate (PU/PC) blends was studied. Poly (ester–urethane) elastomers based on poly (caprolactone) glycol and an aromatic type of diisocyanate (MDI) were synthesized by a prepolymer procedure. Blends of PU and PC with different weight ratios were prepared using a Brabender mixer. Thermal and mechanical properties were evaluated after UV irradiation (200 hours) performing DSC, DMA, TGA and tensile tests. DMA results indicated partial miscibility of PC and PU in the PU/PC blends with higher hard segment content, attributed to favourable interactions between the ester groups from the soft segments and urethane groups from the hard segments. The photochemical degradation of the polyurethane is associated with the scission of the urethane group and photooxidation of the central CH2 group between the aromatic rings. The processes of photooxidative degradation are less pronounced in PU/PC blends with higher hard segment content in the polyurethane.

Highlights

Polyurethanes (PUs) and their blends have found applications in many fields, due to their excellent mechanical properties and resistance to oil, grease, and abrasion, as well as good processability
With the increase in the hard segment content in PU4 elastomer, the Tm1 of the hard segment was obtained at 165.4 °C
After UV irradiation in the PU4 elastomer, two melting temperatures of the hard segment appear (Tm1 = 152.2 °C and Tm2 = 184.3 °C), meaning that the hard segment is present in two different morphological structures (Table 2)

Summary

Introduction

Polyurethanes (PUs) and their blends have found applications in many fields, due to their excellent mechanical properties and resistance to oil, grease, and abrasion, as well as good processability. The use of PU is in the field of automotive, civil engineering and architecture, medical equipment, electronics, textile industry, etc. The urethane bridge oxidizes to a quinone-imide structure. This structure is a strong chromophore, resulting in the yellowing of urethanes. Polycarbonate (PC) is one of the most widely used engineering thermoplastics due to its excellent properties, such as transparency, high mechanical strength, good thermal stability, and flame retardancy[3]. PC has applications in architecture (e.g. window glass, corrosion protection, floors), medicine (medical equipment, Further decomposition and recombination of the primary radicals results in the formation of amino (IV) and carbodiimide (VI) structures with the polycondensation of isocyanates. In the presence of oxygen, the quinoid structure is formed (II), which

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