油硬脂

油硬脂 (Stearic Acid) 专业成分报告

1. 基础信息 & 来源

INCI名称

Stearic Acid

化学描述与来源

油硬脂通常指硬脂酸（Stearic Acid），是一种饱和长链脂肪酸，化学式为C₁₇H₃₅COOH。它广泛存在于动植物油脂中，商业生产主要来源包括：

• 植物来源：棕榈油、椰子油、大豆油等 (依据：常见化妆品原料供应链数据)
• 动物来源：牛脂、羊脂等，但现代化妆品倾向于植物来源 due to sustainability and ethical concerns (参考：ISO 22716 化妆品良好生产规范)

提取与纯化方法

硬脂酸通常通过油脂的水解和分馏过程提取，例如：

• 高压水解植物油脂， followed by distillation to isolate stearic acid from other fatty acids like palmitic acid.
• 纯度等级 vary, with cosmetic-grade stearic acid often being triple-pressed for higher purity (来源：工业标准生产流程).

2. 皮肤作用机制与宣称功效 (科学依据为重点)

硬脂酸 primarily functions as a formulation aid rather than a direct active ingredient. Its effects are largely indirect, through its role in product structure and delivery.

宣称功效表格

宣称功效	作用机制	科学证据强度	关键研究发现简述	起效浓度范围 (典型)
乳化稳定剂	作为油相成分，降低油水界面张力，形成稳定乳液结构；分子中的羧基与乳化剂（如三乙醇胺）反应形成皂，增强乳化 (机制基于胶体化学原理)	强 (广泛证实)	多项研究显示 stearic acid 在 O/W 乳液中提供稳定性，防止相分离 (参考：J. Soc. Cosmet. Chem. 相关研究)	1-10% (在乳霜/乳液中)
增稠剂与质感改良	在配方中结晶形成网络结构，增加产品粘度，提供 creamy 质地；改善铺展性和使用感	强 (实证应用)	工业配方测试中， stearic acid 显著增加 viscosity 和 stability (依据：化妆品配方手册)	2-15% (取决于配方)
清洁剂 (在皂类中)	作为脂肪酸组分，与碱（如氢氧化钠）皂化生成皂，提供发泡和去污能力；通过乳化作用移除皮脂和杂质	强 (化学原理明确)	皂化反应是基础化学，硬脂酸钠是传统肥皂的核心成分 (参考：化学教科书)	10-50% (在皂基产品中)
皮肤屏障支持与保湿	理论推测：作为脂肪酸，可能 integrate into stratum corneum lipids, enhancing barrier function and reducing transepidermal water loss (TEWL) (注：此机制基于脂肪酸类物质的普遍行为，但直接证据有限)	中等 (部分体外/离体证据)	离体皮肤模型显示 exogenous fatty acids can improve barrier properties, but stearic acid-specific data is sparse (来源：有限皮肤学研究)	未知 (可能 low concentrations in leave-on products)
抗刺激或舒缓	厂商宣称：有时 marketed as soothing, but mechanism is unclear; may be due to product's occlusive properties reducing irritation	弱 (缺乏直接证据)	无 robust clinical trials support anti-irritant effects; primarily anecdotal (注：此宣称缺乏强有力的人体临床试验证据支持)	不适用

详细作用机制与证据：乳化稳定剂

硬脂酸在乳液中 acts as a co-emulsifier. Its carboxylic acid group can react with alkaline substances to form soaps (e.g., stearate salts), which lower interfacial tension and stabilize oil-in-water emulsions. This is well-documented in cosmetic science literature, with studies showing improved emulsion stability against coalescence and Ostwald ripening (依据：多项体外研究及离体皮肤模型).

详细作用机制与证据：皮肤屏障支持

While all fatty acids play a role in skin lipid composition, stearic acid's long chain length (C18) may help reinforce the lipid bilayer in the stratum corneum. However, most evidence comes from studies on essential fatty acids like linoleic acid; stearic acid's specific efficacy is less proven. In vitro models suggest it can enhance barrier repair, but human studies are needed (参考：初步体外研究，需进一步验证).

3. 核心化学成分剖析

硬脂酸是一种单一化合物，但商业产品 often contain mixtures with other fatty acids like palmitic acid. Key chemical aspects:

化合物类别	代表物质	基本性质
饱和脂肪酸	Stearic Acid (C18:0)	白色固体或 flakes, melting point ~69°C, insoluble in water, soluble in organic solvents like ethanol and ether; pH-dependent behavior (acidic form vs. salt form)
常见杂质/同系物	Palmitic Acid (C16:0), Oleic Acid (C18:1)	Commercial stearic acid may contain up to 45% palmitic acid; purity affects functionality (e.g., higher stearic content gives harder textures) (依据：原料规格表)
化学衍生物	Glyceryl Stearate, Stearyl Alcohol, Stearate Salts (e.g., Sodium Stearate)	Derivatives are common in cosmetics for modified properties (e.g., glyceryl stearate as an emulsifier); stearate salts are ionic and water-soluble

分子结构特性

Stearic acid has a linear hydrocarbon chain with a carboxylic acid group, making it amphiphilic. This structure allows it to act as a surfactant at interfaces. Its high melting point contributes to solid-like behavior in formulations.

4. 配方应用与协同效应

常见应用类型

• 乳霜和乳液: 作为 primary thickener and emulsifier; often used in concentrations of 2-10%.
• 皂类和清洁产品: 关键成分 in soap bases for its hardening and cleansing properties.
• 彩妆产品: 用于 lipsticks and foundations to provide structure and emolliency.
• 护发产品: 在某些 conditioners and styling products as a conditioning agent.

协同成分

硬脂酸 often works synergistically with other ingredients to enhance formulation performance:

• 与碱剂协同: 如 triethanolamine or sodium hydroxide, to form soaps that improve emulsification and cleaning.
• 与其他乳化剂: 如 cetearyl alcohol or polysorbates, to stabilize emulsions and modify texture.
• 与油脂和润肤剂: 如 mineral oil or shea butter, to enhance spreadability and moisturization.

配方注意事项

Due to its insolubility in water, stearic acid is typically heated and incorporated into the oil phase. pH adjustments can convert it to soluble stearates, altering functionality. Overuse may lead to graininess or stability issues in emulsions.

5. 安全性与适用性

安全性概况

硬脂酸 is generally considered safe for cosmetic use. Key points:

• Regulatory Status: Approved by FDA for food and cosmetic use, listed in FDA's GRAS (Generally Recognized As Safe) list; also approved by EFSA and other agencies (参考：CIR安全评估报告).
• 皮肤刺激性: Low irritation potential; however, undiluted acid may cause mild irritation in sensitive individuals. Salt forms (e.g., sodium stearate) can be more irritating due to alkalinity.
• 致痘性: Rated as moderately comedogenic in rabbit ear assays, but human data is limited; may clog pores for acne-prone skin in high concentrations (依据：历史动物研究，人类相关性不确定).
• 过敏反应: Rare; patch tests show low sensitization potential.

适用肤质与人群

• 适用: Normal to dry skin; generally safe for all ages when formulated properly.
• 谨慎使用: Acne-prone or very oily skin due to potential comedogenicity; sensitive skin should patch-test due to possible irritation from impurities or derivatives.
• 孕妇与儿童: Considered safe, but always check full formulation for other ingredients.

环境与伦理考虑

Plant-derived stearic acid is preferred for sustainability. Animal-derived versions may raise ethical concerns; consumers should look for "vegetable-based" labels.

6. 市场定位与消费者认知

市场常见定位

• 基础成分: Often marketed as a natural or traditional ingredient in creams and soaps.
• "天然"宣称: Frequently used in "natural" or "organic" products, though it is processed; greenwashing may occur.
• 经济型产品: Due to low cost, it is common in mass-market cosmetics.

消费者认知与误解

• 正面认知: Viewed as effective for thickening and moisturizing; associated with luxury in some contexts (e.g., traditional soap-making).
• 误解: Some consumers confuse it with "stearates" or think it is always animal-derived, leading to avoidance; education on plant sources is needed.
• 营销趋势: Increasing demand for vegan and sustainable options drives use of plant-based stearic acid.

7. 总结与展望

总结

硬脂酸 (Stearic Acid) is a versatile, well-established cosmetic ingredient primarily valued for its emulsifying, thickening, and cleansing properties. While it has some theoretical benefits for skin barrier function, its direct biological effects are less proven. Safety is high, but formulation context matters for comedogenicity and irritation.

未来展望

• 研究方向: More human studies on its barrier repair potential and comedogenicity in modern formulations.
• 创新应用: Development of derivatives and blends for enhanced functionality (e.g., nanoemulsions or sustainable alternatives).
• 市场趋势: Growth in plant-based and ethically sourced stearic acid to meet consumer demands for transparency and sustainability.