Introduction
Cyclopentasiloxane (D5) has long been the chemist’s shortcut to effortless spreadability, fast evaporation, and a signature silky finish in serums, primers, and hair treatments. However, due to mounting environmental restrictions—especially in the EU and Canada—formulators are now being challenged to redesign volatility profiles from the ground up. Consequently, creating a D5 replacement system is no longer optional but a necessary evolution for sustainable formulation. This D5 Replacement Playbook explains how to engineer volatile profiles without cyclopentasiloxane by blending biodegradable emollients such as Hemisqualane, Isododecane, C13-15 Alkane, and Polydecene. In doing so, you can achieve comparable sensorial performance while ensuring regulatory and environmental compliance.
Why D5 Replacement Matters
D5 belongs to a family of volatile silicones known as cyclomethicones. Although they are chemically stable and cosmetically elegant, these molecules are not readily biodegradable and tend to accumulate in aquatic environments. Therefore, the European Chemicals Agency (ECHA) classified D5 as vPvB—very persistent and very bioaccumulative—under REACH. As a result, most rinse-off and leave-on formulas in Europe must now either eliminate D5 or maintain concentrations below 0.1%. Because of this shift, clean beauty brands and chemists alike are actively investing in volatile design technologies that deliver similar sensory experiences without silicone residues. Ultimately, this transition is driving innovation toward safer, greener emollients.
Volatility and Sensorial Fundamentals
Volatility is what defines how a product spreads, dries, and feels after application. It depends not only on molecular weight but also on vapor pressure and polarity. To replicate D5’s sensorial signature, chemists must design for three performance phases: spreadability, dry-down, and after-feel. Moreover, understanding volatility curves—rather than viscosity values alone—allows for precise tuning of texture and evaporation rates. Consequently, mastering this balance ensures both high performance and sensorial sophistication.
- Spread phase (0–10 s): rapid slip without drag or stickiness.
- Dry-down (10–60 s): smooth evaporation that leaves no residue.
- After-feel (>1 min): soft, powdery finish with a non-greasy touch.
Therefore, replacing D5 successfully means crafting systems that reproduce these three sensorial stages with sustainable chemistry.
Volatility Comparison Table
To make informed formulation decisions, it helps to compare volatility and tactile profiles across candidate materials. The following table summarizes the most relevant clean emollients and their evaporation characteristics relative to D5.
| Material | Type | Boiling Point (°C) | Evaporation Rate vs D5 | Film Residue / Finish |
|---|---|---|---|---|
| Cyclopentasiloxane (D5) | Volatile silicone | 210 °C | 1.0 (reference) | Dry, silky, fast-break |
| Isododecane | Hydrocarbon solvent | 165 °C | 1.3 (faster) | Very dry, weightless |
| Hemisqualane | Plant-derived hydrocarbon | 240 °C | 0.9 (similar) | Silky, biodegradable |
| C13-15 Alkane | Hydrogenated plant alkane | 250 °C | 0.7 (slower) | Soft, cushiony |
| Polydecene | Hydrogenated oligomer | >300 °C | 0.4 (long-lasting) | Rich, emollient finish |
Sensorial Mapping and Volatility Curve
When these materials are plotted on a volatility curve, they form a continuum from ultra-light to long-lasting. For instance, Isododecane flashes off more quickly than D5, giving an exceptionally dry finish. Meanwhile, Hemisqualane matches D5’s tactile performance nearly one-to-one, offering both slip and smooth dry-down. In contrast, C13-15 Alkane and Polydecene extend the after-feel, enhancing cushion and moisturization. Thus, formulators can design complete volatility waves by layering fast and slow components to emulate silicone performance naturally.
Building a D5-Like Blend
Since no single material exactly matches D5’s volatility, blending is the key to success. Moreover, multi-component systems provide greater control over sensory pacing and film residue. The examples below illustrate how different ratios yield tailored experiences.
- 60 % Hemisqualane + 40 % Isododecane → replicates D5’s slip and dry-down in light emulsions.
- 50 % Hemisqualane + 30 % C13-15 Alkane + 20 % Polydecene → enhances cushion and gloss for primers or BB creams.
- 70 % Isododecane + 30 % Hemisqualane → ideal for sprays or fast-drying textures.
Formulation Engineering Strategies
1. Adjusting Evaporation Kinetics
Evaporation behavior depends on both molecular polarity and phase composition. Non-polar volatiles like Isododecane spread rapidly, while polar ones such as Hemisqualane anchor sensorial balance. Consequently, combining them produces wave-like evaporation curves that mimic D5’s iconic feel. In practice, this method ensures a smooth application and consistent finish.
2. Maintaining System Stability
Because D5 was an excellent pigment dispersant, its removal often affects suspension stability. To counter this, increase dispersant loading or use small amounts of stabilizers such as polyhydroxystearic acid. Additionally, low-HLB emulsifiers and hydrogenated lecithin can improve interfacial stability. As a result, the product retains both its texture and sensorial uniformity over time.
3. Controlling After-Feel
D5’s soft powdery after-feel came from its rapid flash-off and low surface tension. Therefore, pairing fast volatiles with light film-formers such as polyesters or polyglyceryl esters restores the same dry-touch profile. Moreover, adding a small percentage of Polydecene provides slip continuity, creating a luxurious finish without greasiness.
Formulation Examples
Silicone-Free Primer (D5-Alternative System)
- Hemisqualane – 45 %
- Isododecane – 35 %
- C13-15 Alkane – 10 %
- Dimethyl Isosorbide – 5 %
- Silica Microspheres – 3 %
- Polyester-5 – 2 %
This formulation provides a fast-dry, cushiony texture comparable to D5-based primers. Moreover, it remains fully biodegradable and compatible with natural pigments.
Lightweight Hair Serum
- Isododecane – 60 %
- Hemisqualane – 25 %
- Polydecene – 10 %
- Caprylyl Methicone (volatile blend) – 5 %
The combination offers excellent shine, slip, and rapid absorption. In addition, it meets silicone-free claims while maintaining professional-grade performance.
Regulatory and Sustainability Outlook
The EU and UK list D5 under REACH Annex XVII, limiting rinse-off use to <0.1%. Similarly, Canada and South Korea have announced comparable actions. Consequently, chemists must proactively transition to biodegradable alternatives. Fortunately, materials such as Hemisqualane (biobased) and C13-15 Alkane (derived from renewable feedstocks) already comply with environmental standards. Therefore, replacing D5 not only aligns with regulations but also enhances a brand’s sustainability credentials.
Testing and Documentation
To validate claims, perform and record the following tests:
- Evaporation Profile – Thermogravimetric or gravimetric analysis
- Flash Point – ASTM D93
- Biodegradability – OECD 301 / 310
- Safety Data Sheets and IFRA Compliance
Furthermore, store all data within your MoCRA Safety Dossier for complete audit readiness.
Compliant Claim Examples
- “Provides silicone-like slip with 100 % biodegradable emollients.” ✅
- “Cyclopentasiloxane-free system with identical sensory feel.” ✅
- “Eco-designed volatility replacement engineered for clean beauty.” ✅
- “Medical-grade volatility replacement.” ❌ (Avoid therapeutic claims)
Summary & Key Takeaways
- Environmental pressure on D5 has accelerated the shift toward biodegradable volatility systems.
- Hemisqualane best replicates D5’s smooth slip; Isododecane enhances flash-off speed.
- C13-15 Alkane and Polydecene extend playtime for richer sensorial effects.
- Blending is essential to fine-tune evaporation and film formation.
- Proper testing and documentation guarantee compliance and product credibility.
Next Steps for Chemists
In conclusion, replacing D5 is not merely about eliminating a silicone—it is about re-engineering sensorial chemistry for a cleaner, modern era. Begin by analyzing your existing formulation’s volatility profile. Then, rebuild it using complementary hydrocarbons to design a multi-phase evaporation wave. For in-depth specifications, visit the Product Center for Hemisqualane, Isododecane, C13-15 Alkane, and Polydecene. Finally, to test sensorial behavior and volatility data, connect with our Formulation Engineering Hub or Request a Sample today.
References
- ECHA (2023). Restriction on cyclic siloxanes D4/D5/D6 – Annex XVII of REACH.
- Rieger, M.M. (2024). “Volatile Emollients in Silicone-Free Systems,” *Int. J. Cosmetic Sci.* 46 (2): 145–158.
- Supplier Data Sheets – Hemisqualane, Isododecane, C13-15 Alkane, Polydecene (2025).
