Investigation of the Ultraviolet Irradiation on Blend Films of PS/PCL

Abstract

In this work, an investigation was carried out on the effect of ultraviolet light on different films. Polystyrene (PS), poly (caprolactone) (PCL), and blended films of PS/PCL were produced. Ethyl acetate (AE) was used as a solvent, and PS and PCL solutions were prepared by dissolving 250 mg in 2.5mL of AE under mechanical stirring at room temperature. The blended solutions of PS/PCL (PS:PCL) were prepared with different mass proportions, such as 90:10, 80:20, 70:30, and 60:40 into 2.5 mL of EA. The solutions were dripped with 500 µL on a glass substrate, and the films were produced with mechanical rotation of N=2000 RPM for 15 seconds using a Spin coater. The films were submitted to ultraviolet light for t=60 minutes and morphologically analyzed by optical microscopy, chemically by IR spectroscopy, and superficially by contact angle and wettability; this last analysis also investigated the effect of ultraviolet light at t=0, t=30, and t=60 minutes. The exposure of ultraviolet light on the films affected its morphologies. IR spectra showed that the photodegradation increased for larger PCL amounts into the blend. The contact angle measurements showed that after exposure to ultraviolet light, the hydrophobicity of the films increased. Therefore, the presence of PCL in the polymer mixture promoted the photodegradation of the PS/PCL films, making it attractive for developing new packaging.

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“…This is probably due to two concomitant factors: (1) the presence of bonds with maximum dissociation wavelength (342 nm for C-O) close to the maximum of the UV-A lamps (340 nm) of the QUV instrument and (2) the molecular structure with low characteristic glass transition ( T g ) and melting temperatures ( T m ). This combination favors primary and secondary deterioration processes with rapid matrix and pigment degradation, leading to PCL test failure after 14 days of QUV aging. , Albeit with less intensity, analogous degradative behavior occurs for PBS_0.1LWP. In this case, higher characteristic temperatures and more stable to near-UV radiation molecular structure allowed the QUV test to be completed; however, evident deterioration and color fading effects are noted on the samples. , No relevant color variations are instead observed for the aged PLA_0.1LWP sample.…”