# Degradation of Some Polymeric Materials of Bioreactors for Growing Algae

## TL;DR

This study compares how different plastics used in algae bioreactors degrade over time, finding that PMMA is the most durable and suitable for long-term use.

## Contribution

The study identifies PMMA and PMMAR as the most stable materials for bioreactors under real-world conditions.

## Key findings

- PMMA and PMMAR showed the highest light transmission and surface stability.
- PET performed the worst with low initial clarity and rapid degradation.
- Vapor-exposed zones degraded more severely than fully immersed areas.

## Abstract

What are the main findings?
PMMA and PMMAR exhibited the highest light transmission and surface stability.PC and PET showed moderate degradation, while PC2UV suffered severe optical losses.Vapor-exposed zones were more prone to degradation than fully immersed ones.

PMMA and PMMAR exhibited the highest light transmission and surface stability.

PC and PET showed moderate degradation, while PC2UV suffered severe optical losses.

Vapor-exposed zones were more prone to degradation than fully immersed ones.

What are the implications of the main findings?
Both types of PMMA are recommended for long-term use in bioreactors.Reduced transmittance lowers cultivation intensity and should be minimized in bioreactor use.Contact of the material with the vapor inside the bioreactor should be as little as possible.

Both types of PMMA are recommended for long-term use in bioreactors.

Reduced transmittance lowers cultivation intensity and should be minimized in bioreactor use.

Contact of the material with the vapor inside the bioreactor should be as little as possible.

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 (PMMAR) as durable, cost-effective materials for transparent bioreactor walls.