# Mitigating UV‑C Degradation in Polypropylene Using Hybrid TiO2/Few-Layer Graphene/Photostabilizer Systems

## TL;DR

This paper explores how combining graphene and a photostabilizer with titanium dioxide can protect polypropylene from UV-C damage, improving its durability in medical applications.

## Contribution

The study introduces a hybrid system of TiO2, few-layer graphene, and Irganox B215 to mitigate UV-C-induced degradation in polypropylene.

## Key findings

- Combining FLG and TiO2 reduced hydroxyl radical formation by about 30%.
- The hybrid system improved PP's resistance to UV-C by reducing chain scission and scavenging ROS.
- FLG showed synergistic effects with TiO2 at higher concentrations.

## Abstract

Polypropylene (PP)
is a versatile thermoplastic widely used in
industrial fields. In medical devices, PP is preferred for applications
that involve storing or coming into contact with biological fluids.
However, when exposed to UV-C, commonly used as a cleansing tool in
hospitals, PP undergoes a photodegradation process, resulting in chain
scissions and branching reactions that impact the material properties
and lifespan. Different photostabilizers can be used to enhance polymer
resistance against UV, such as UV screeners like titanium dioxide
rutile (TiO2), radical scavengers like Irganox B215, a
commercial H-donor and peroxide scavenger, and, more recently, graphene
and its derivatives like few-layer graphene (FLG). Graphene has gained
attention as an alternative photostabilizer in polymers for having
different types of UV photoprotection mechanisms, such as UV absorbers/screeners
and radical scavengers. In this context, this study aimed to evaluate
the effectiveness of FLG and Irganox B215 as radical scavengers in
combination with TiO2 to minimize the effect of parallel
radical formation (ROS) from TiO2 electron–hole
reactions and from the PP photodegradation autocatalytic cycle. A
Design of Experiments (DoE) approach was employed to identify the
optimal UV-C photostabilization mixture. Infrared spectroscopy and
rheological measurements were used to assess the effects of UV-C photodegradation
on PP. Scanning electron microscopy and energy-dispersive X-ray spectroscopy
were used to analyze the stabilizer distribution and dispersion, and
electron paramagnetic resonance evaluate the effectiveness of FLG
and Irganox B215 as radical scavengers. EPR results showed that mixing
radical scavengers with TiO2 reduced OH formation by ∼30%
for the FLG and ∼25% for the B215 mixture. Although the stabilizers
exhibited poor dispersion but good distribution, the addition of FLG
had a synergistic effect with TiO2. At the highest level
(+1), i.e., TiO2 3% and FLG 2% m/m, PP UV–C photoprotection
was enhanced by diminishing chain scission and scavenging ROS from
TiO2.