Degradation of Some Polymeric Materials of Bioreactors for Growing Algae

Transparent polymeric materials such as poly(methyl methacrylate) (PMMA), polycarbonate (PC), and polyethylene terephthalate (PET) are widely used as glass alternatives in algal bioreactors, where optical clarity and mechanical stability are crucial. However, their long-term use is limited by surface degradation processes. Photodegradation, hydrolysis, and biofilm accumulation can reduce light transmission in the 400-700 nm range essential for photosynthesis. This study examined the aging of PMMA, PC, and PET under bioreactor conditions. Samples were exposed for 70 days to illumination, culture medium, and aquatic environments. Changes in their optical transmittance, surface roughness, and wettability were analyzed. All polymers exhibited measurable surface degradation, characterized by an average 15% loss in transparency, significant increases in surface roughness, and reduced contact angles. PMMA demonstrated the highest optical stability, maintaining strong transmission in key blue and red spectral regions, while PET performed the worst, showing low initial clarity and the steepest decline. The most severe surface degradation occurred in areas exposed to the receding liquid interface, highlighting the need for targeted cleaning and/or a reduction in the size of the liquid-vapor transition zone. Overall, the results identify PMMA and recycled PMMA (PMMA_R) as durable, cost-effective materials for transparent bioreactor walls.