Polyester-1: properties, uses, pros, cons, safety
Polyester-1 is a synthetic polymer of the polyester/copolymer type used in cosmetics mainly as a film former and performance modifier. In practical terms, it helps form a continuous film on skin/hair/nails, improving uniformity, sensoriality, and—in some product categories—wear/hold and resistance to humidity or transfer (depending on the base and use level).
Definition
Polyester-1 is produced via a polycondensation process that uses the following production substances: isophthalic acid, acrylic acid, methacrylic acid, t-butylacrylamide, cyclohexane dimethanol, diethylene glycol.
From a chemical–functional standpoint:
the diols (cyclohexane dimethanol, diethylene glycol) build the “alcohol” portion of the polymer chain;
the acids (isophthalic acid, acrylic acid, methacrylic acid) provide acidic units that form ester bonds and introduce segments with different rigidity/polarity;
t-butylacrylamide can increase cohesion and film properties (hardness, adhesion, humidity resistance), in a grade-dependent way.
Overall, the polymer is designed to balance film adhesion, flexibility, and resistance.
Main uses
Cosmetics
Typical use as a film-forming polymer in:
hair styling products (gels, creams, sprays) to improve hold and definition;
make-up (some bases) to increase adhesion and deposit uniformity;
selected skincare, when a smoother skin feel and a light film that improves slip are desired (when compatible).
INCI functions
Film-forming agent. It produces a continuous ultra-thin film with an optimal balance of cohesion, adhesion and stickiness on the skin or hair to counteract or limit damage from external phenomena such as chemicals, UV rays and pollution.
Industrial use
Primarily cosmetic (personal care) as a performance polymer to modulate surface properties (film, cohesion, transfer resistance) in compatible matrices.
Identification data and specifications
| Characteristic | Value | Note |
|---|---|---|
| INCI name | Polyester-1 | Cosmetic denomination |
| Origin | synthetic | Man-made polymer |
| Class | polyester/copolymer | Structure depends on grade |
| Main function | film forming | Cosmetic function |
| Synthesis method (description) | polycondensation | With the precursors listed below |
| Substances used in the production method | isophthalic acid; acrylic acid; methacrylic acid; t-butylacrylamide; cyclohexane dimethanol; diethylene glycol | Useful for QC and traceability |
| CAS number | to be verified in SDS/supplier documentation | Often not unique across commercial grades |
| EC number (EINECS) | to be verified in SDS/supplier documentation | Depends on classification |
Chemical-physical properties (indicative)
| Characteristic | Indicative value | Note |
|---|---|---|
| Physical state | resin/solid polymer or dispersion/solution form | Depends on grade and carrier |
| Color | light to slightly amber | Batch-dependent |
| Odor | mild / neutral | Usually not dominant in the finished product |
| Water solubility | low / variable | Often more dispersible than soluble |
| Solubility in cosmetic solvents | variable | Often better in hydroalcoholic systems or dedicated carriers |
| Film properties | from flexible to more rigid | Depends on composition and plasticization |
| Chemical stability | generally good | Criticalities more often tied to compatibility and sensoriality |
Functional role and mechanism of action
The action is mainly physical: after application and drying, Polyester-1 forms a continuous film that can:
increase cohesion and product “anchoring” on the surface;
improve deposit uniformity and reduce visual defects (in some bases);
on hair, contribute to hold and shape control, with response varying with humidity and the presence of plasticizers/humectants.
Formulation compatibility
Performance depends significantly on:
solvent system and carrier (water, alcohols, glycols, blends);
presence of surfactants and electrolytes;
synergies or competition with other film formers (acrylates, polyurethanes, resins) and plasticizers;
processing (order of addition, wetting/solubilization time, shear).
During development it is recommended to verify hot/cold stability, thermal cycles, and targeted application tests (feel, hold, humidity resistance).
Production process
A scheme consistent with polycondensation:
preparation of the reactive mixture with the diols (cyclohexane dimethanol, diethylene glycol) and the acids (isophthalic acid, acrylic acid, methacrylic acid);
reaction progression with formation of ester bonds and removal of condensation by-products;
introduction/integration of t-butylacrylamide to modulate cohesion and film properties;
finishing and standardization (solids, viscosity, color, residuals) depending on the commercial grade.
Pros and cons
Pros
Strong film-forming contribution for uniformity and performance (hold/adhesion) in compatible systems.
Possible improvement in humidity resistance and perceived durability if correctly balanced.
Versatile as a “structuring” polymer across different categories (haircare, make-up, some skincare).
Cons
Overly rigid film: risk of dry feel, tightness, or flaking if the system is not plasticized.
Non-universal compatibility: possible haze, instability, or non-uniform performance if carrier and process are not adequate.
Possible build-up on hair in high-deposition formulas and repeated use, affecting volume and feel.
Safety, regulatory, and environmental aspects
High-molecular-weight polymers generally show low dermal bioavailability, but safety assessment must always be based on the finished product (use level, application area, frequency).
Allergen.
It is not typically a classic “fragrance allergen”; reactions are more often related to the overall formula and individual sensitivity.
Contraindications (brief).
For spray formats, consider incidental inhalation exposure based on aerosol profile and formulation strategy.
Formulation troubleshooting
Film flaking or poor flexibility.
Action: introduce or re-tune a compatible plasticizer; reduce dosage; balance with a more flexible film former.
Haze or long-term instability.
Action: optimize carrier and order of addition; verify compatibility with surfactants/electrolytes; consider an alternative carrier.
Insufficient hold under humidity.
Action: review polymer/plasticizer ratio; evaluate synergies with other film formers; test on real substrate under controlled conditions.
Conclusion
Polyester-1 is a film-forming polyester produced by polycondensation from isophthalic acid, (meth)acrylic acids, diols, and t-butylacrylamide. Its technical value lies in forming a continuous film that supports uniformity and performance (especially in styling and some make-up bases). Results depend mainly on carrier, plasticization, system compatibility, and process control.
