What is CAPB?

CAPB is produced from coconut fatty acids (or corresponding esters) reacted with dimethylaminopropylamine, then quaternized with sodium chloroacetate. The result is a zwitterionic molecule: quaternary nitrogen + carboxylate. At rinse-off pH (~5–7) CAPB exists mainly as a zwitterion, forming mixed micelles with anionics that feel milder than anionic-only bases.

Why formulators choose CAPB

  • Foam density and creaminess at lower primary anionic levels
  • Irritation reduction vs SLES/LAS-only systems
  • Salt-curve viscosity build with NaCl
  • Compatibility with polyquaterniums in 2-in-1 shampoos
  • Broad raw-material availability and cost position

Worked shampoo chassis

See also SLES + CAPB blend and SLES + cocamide MEA + CAPB.

  • 10–14% SLES (primary)
  • 3–5% CAPB (amphoteric co-surfactant)
  • 0–2% cocamide MEA or FAE for foam / viscosity
  • NaCl for salt curve
  • Citric acid to pH 5.0–5.5
  • Preservative, fragrance, dye

Specification and impurity control

CAPB quality varies by route and residuals. Skin-sensitizer concerns focus on residual amidoamine and dimethylaminopropylamine (DMAPA). Specify low-impurity grades and review COA targets (many brands push amidoamine as low as practical, often <50 ppm where available). Also check active %, NaCl, colour, and microbiological limits for personal care.

CAPB vs hydroxysultaine

Choose CAPB for mass-market shampoo foam aesthetics and cost. Choose hydroxysultaine when salt/builder load is high (dish, HI&I). Do not assume 1:1 substitution without rebuilding rheology.

Troubleshooting

  • Thin viscosity: Adjust salt curve; verify CAPB active and SLES grade
  • Haze at low temperature: Check electrolyte and fragrance oil; add mild hydrotrope or FAE
  • Eye sting: Lower anionic; raise CAPB or shift to amphoacetate-rich mild systems
  • Polyquat incompatibility: Order of addition and charge balance — amphoterics help bridge

Related: amphoteric guide, personal care surfactants, LAS / SLES / AOS. Contact Venus for formulation discussion.