MARC ARDERIU GIRAME
Thor Especialidades, S.A.
Pol. Ind. El Pla – Avga. de la Indústria 1,
Castellgalí, Barcelona, 08297 Spain

Abstract

Quaternary ammonium compounds (Quats) are cost-effective conditioning actives for personal care providing a variety of benefits to hair: reducing combing force, conferring smoothness and antistatic properties. Their deposition on hair is explained by a combination of electrostatic and van der Waals interactions. A methodology aimed at mimicking the interaction of Quats with hair by using anionic textiles (wipes) has been developed. Parameters such as the nature of wipe, the influence of the Quat concentration and the rinsing method are examined to finally disclose retention and build up effects. The method also predicts which Quats are more appropriate for treated/damaged hair and others for natural hair and explains their efficiency when applied in repetitive and low doses or high doses in one application.

INTRODUCTION

Hair structure

The human hair is a “complex tissue” formed by proteins, water, lipids, trace elements and pigments, being rich in keratin (cysteine-rich protein) which provides its high strength, flexibility, durability and functionality (1,2). Natural hair, not chemically modified, is mostly hydrophobic as a result of the layer of fatty acids covalently bound via thioester linkages to the outermost surface of the cuticle (3).

As a result of its protein structure, the hair surface presents positively and negatively charged groups, rendering an isoelectric point near 3.67. Hence, for pHs < 3.67 the negative groups will be neutralised and the hair will become more positive. On the other hand, for pHs > 3.67, hair will become more negative as the positive groups lose their charge. This is the predominant situation found when a hair care product (such as a conditioner) is applied, since the pH of these products is between 4.0 – 5.0.

By the use of treatments such as perming, bleaching or dyeing as well weathering conditions (UV radiation ...