Science
Mechanism of Action
This modified terephthalate polymer forms a durable, continuous film on the skin, hair, or nails upon application, which aids in product adherence and longevity. Its polymeric structure also acts as a bulking agent, contributing to the body and texture of formulations. Additionally, it can serve as a non-aqueous viscosity-increasing agent, and when presented as small flakes, it functions as a gentle abrasive or exfoliant.
Research
Clinical Evidence
Medium confidenceN/A
Key findings
- 01 Reported cosmetic uses for Polyethylene Isoterephthalate (in flake form) include concentrations up to 0.5% in eye shadow, 0.12% in lipstick, 0.35% in nail polish and enamel, and 0.04% in hair grooming aids, demonstrating its utility across diverse product types.
- 02 Safety assessments for the chemically analogous Polyethylene Terephthalate (PET) in eye products, even at concentrations up to 46.272%, consistently demonstrated non-irritating and non-sensitizing effects, including in individuals wearing contact lenses. An eyeliner containing 1.5% PET also showed no irritation or sensitization in repeated insult patch tests.
Transparency
Dusting Analysis
Given its primary roles as a functional film-former, bulking agent, and physical abrasive, Polyethylene Isoterephthalate is typically incorporated at concentrations where its physical properties contribute meaningfully to the product, making it unlikely to be 'dusted' for superficial claims.
The Formula
Formulation
Stability
Polyethylene Isoterephthalate is considered practically insoluble in water. While generally resistant to weak acids and many organic solvents (e.g., acetone, benzene, oils), its ester bonds are vulnerable to degradation. It is not resistant to hot water immersion, strong acids, or strong alkalis, particularly under conditions of high temperature and steam. This ingredient is hygroscopic and must be dried to a moisture content of 0.05% or less during processing to prevent thermal decomposition and maintain mechanical integrity.
Conflicts
- strong acids (especially at high temperatures)
- strong alkalis (especially at high temperatures)
- hot water immersion
Safety
Safety Profile
The Cosmetic Ingredient Review (CIR) Expert Panel concluded that Polyethylene Isoterephthalate, along with other modified terephthalate polymers, is safe for use in cosmetics under current practices and concentrations. For safety evaluation, it is considered chemically equivalent to Polyethylene Terephthalate (PET), which has FDA approval for indirect food contact and medical device applications, supporting its safety profile for topical use.
Your Skin
Skin Compatibility
Our Assessment
Verdict
Polyethylene Isoterephthalate is a safe and versatile polymeric ingredient, highly valuable for its functional contributions as a film-former, bulking agent, and mild abrasive across a wide range of cosmetic formulations.
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