Improve Biodegradability

Delivering sustainable and highperforming sunscreens is a major challenge faced by the global sun care industry. For the past few years, sun care brands have been searching diligently for biodegradable alternatives, but until this point hardly any sustainable materials have also succeeded in meeting performance targets. A highly efficient and eco-friendly solution that addresses the key need of the global sun care industry for better skin protection against harmful Ultraviolet (UV) exposure is the innovative booster microcrystalline cellulose¹. UV exposure is the primary root cause for non-biological skin ageing and cancer, and increased awareness of sun/UV damage has driven the rapid growth of this market, projecting to reach $24.9 billion by 2029. UV filters and Sun Protection Factor (SPF) boosters are essential for UV protection. However, these ingredients are facing heightened regulatory scrutiny due to health and environmental concerns, resulting in bans and deselection by brand owners and regulatory agencies like the FDA. Finding sunscreen ingredients that are both sustainable and high performing is a challenge the industry continues to face.^2,3

The challenge with UV filters

SPF boosters are traditionally utilised to improve UV blocking efficacy of UV filters, thereby enabling high SPF products with lower dosage of UV filters. Fewer UV filters leads to improved sensory experience and can contribute to reduced greasiness/tackiness, which is important for consumer adoption. But some of those ingredients are not biodegradable and some are considered microplastics. For the past few years, global sun care brands have been searching diligently for biodegradable alternatives that still meet performance targets. An innovative microcrystalline cellulose was introduced to the market to close this gap with strong performance while meeting demands for sustainability and biodegradability. The SPF booster offers a high efficiency to enable enhanced sun protection with fewer UV filters, and a strong sustainability profile, including

• 100% renewable carbon
• Natural origin index of 0.97 based on ISO16128 norm
• Readily biodegradable according to OECD 301F
• Bio-derived from PEFC-certified wood pulp to allow responsible sourcing of raw materials.

How the booster works

The booster is utilising a light scattering mechanism with UV scattering attributed to its particle size and refractive index (1.51-1.56). Scattering of the harmful UV light can increase the optical path length inside the sunscreen film, resulting in a higher probability for the UV light to be absorbed or strongly backscattered by the UV filters. To enable the optimal performance, it is recommended to add this specific microcrystalline cellulose to the continuous phase of the formulation and apply homogenisation to ensure uniform and continuous coverage of the booster in the sunscreen film. Additionally, it provides multifunctional benefits such as thickening and superior shear thinning, further reducing usage of nonbiodegradable rheology modifiers.

The rheological behaviour of sunscreens containing this specific microcrystalline cellulose was analysed using flow curves. As shown in figure 1, the data points were fitted to the Power-Law Fluid equation with R2 values close to 1: η=K·γ n-1

Where η is the viscosity, K is the flow consistency index, γ is the shear rate, and n is the flow behaviour index. For a shear thinning fluid, n is < 1. Smaller n indicates higher degree of shear thinning. The n value of a sunscreen made

with 4.5% microcrystalline cellulose and no other thickeners was only 0.02, which was ten times less than the traditional acrylate copolymer thickener, “Aculyn 38”. When used in a sunscreen with the presence of 3% “Acu-lyn 38”, the booster lowered the n value by 50%, outperforming the benchmark. The superior

shear thinning enables good spreadability and sprayability within consumer products.