The Effects of Cationic/hydrophobic-modified Hydroxyethyl Cellulose Polymers on Heat-Styling Damage
Podium 26
Presented by: Cindy Delvalle
Introduction
Cationic/hydrophobic-modified hydroxyethyl cellulose (cat-hmHEC) polymers exhibit a variety of unique characteristics that strongly distinguish them from other cationic polymers. Previous studies showed that cat-hmHEC polymer can be used as alternatives for silicones in conditioner applications. The hydrophobe chain contributes to softness/smoothness while the cationic moiety increases the polymer deposition onto the hair surface. In this study, cat-hmHEC polymer was evaluated as a thermal protectant and applied to the hair in a leave-in format. Current technologies use polyvinylpyrrolidone /dimethylaminopropylamine acrylates copolymer or amodimethicone polymers as a heat protectant due to their low thermal conductivity and film forming ability. Unlike some of the incumbent products, cat-hmHEC polymer improves the sustainability profile (~50% biobased/inherent-primary biodegradable) in addition to the thermal protection benefits. The hair tresses were treated using a flat iron, and the keratin degradation and thermal properties of the polymer-treated hair fibers were analyzed using differential scanning calorimetry (DSC). Surface properties of hair was evaluated using scanning electron microscopy. To better understand the thermal protection mechanism, the polymer was compared to different variations of cellulosic polymer, including hydroxyethyl cellulose (HEC) and polyquaternium-10 (PQ-10) polymer. The polymer pretreatment significantly increases the denaturation temperature, Td, and denaturation enthalpy (ΔH) in comparison to the thermally-treated hair without a protectant. Among all the polymers that were screened, cat-hmHEC provided the highest level of thermal protection, while HEC and PQ-10 polymers provided the least level of protection at the same use level (1 w/w %). Results suggested that hydrophobicity plays a crucial role in reducing hair damage upon exposure to heat. In addition, mechanical properties of the hair were evaluated via tensile testing, revealing an improvement in elastic modulus and mechanical work of the thermally-treated hair with cat-hmHEC polymer.
Methods
A series of cat-hmHEC polymers with cationic-hydrophobic variations were evaluated at 0.1 and 1% active level in a leave-in conditioner and compared to cationic celluloses and aminosilicone polymers. The hair tresses were treated using a flat iron at 232 °C for 10 times, 10 seconds each. The treated tresses were washed with 9% SLS (0.2 g/g of hair) for 30 s, rinsed with water for 1 min, and dried at room temperature, 50% RH for at least 12 hours prior to the analyses. The thermal evaluation was performed using DSC, and the surface of the hair cuticle was analyzed using SEM. The enhanced mechanical properties were tested using a mechanical tensile test on single hair fibers. The testing was performed in the wet state.
Results
The polymer pretreatment provided significant reduction in Td and ΔH loss in comparison to the thermally treated hair without a protectant. Among all the polymers that were screened in this study, cat-hmHEC provided the highest level of thermal protection, while HEC and PQ-10 polymers provided the least level of protection at the same use level (1 w/w %). Initial results suggested that hydroxy functionality on amodimethicones significantly impacts thermal protection. It was hypothesized that cellulose, which contains higher hydroxyl contents, and hydrophobic functionality, would also improve thermal protection on hair. According to the structure-property-performance analysis, cationic charge provides no significant impact on reducing damage from thermal treatment. However, the level of hydrophobicity plays a chief role in improved thermal protection on hair. It is hypothesized that the polymer was able to form a film-like structure on the surface of the hair fiber, preventing excessive water loss caused by the heat treatment while protecting the hair fiber from direct contact with heat. The long-alkyl chain together with an adequate degree of substitution may provide another layer of thermal protection. In addition, thermally-treated hair with cat-hmHEC polymer has shown improved mechanical properties of the hair fiber in comparison to that without a polymer treatment. The results reveal insight into structure-property relationship between polymer and hair that both hydroxy and hydrophobic functionalities play a role in thermal protection.
Discussion and Conclusion
Modification of these polymers has enabled different features that provide unique benefits to hair applications. Varying structural parameters such as hydroxy/hydrophobic substitution significantly impact not only sensorial properties but also thermal properties. This learning can be leveraged and applied to other types of polymer backbone to achieve similar thermal properties. It is therefore very crucial to understand the structure-property-performance relationship to achieve performance.
Cationic/hydrophobic-modified hydroxyethyl cellulose (cat-hmHEC) polymers exhibit a variety of unique characteristics that strongly distinguish them from other cationic polymers. Previous studies showed that cat-hmHEC polymer can be used as alternatives for silicones in conditioner applications. The hydrophobe chain contributes to softness/smoothness while the cationic moiety increases the polymer deposition onto the hair surface. In this study, cat-hmHEC polymer was evaluated as a thermal protectant and applied to the hair in a leave-in format. Current technologies use polyvinylpyrrolidone /dimethylaminopropylamine acrylates copolymer or amodimethicone polymers as a heat protectant due to their low thermal conductivity and film forming ability. Unlike some of the incumbent products, cat-hmHEC polymer improves the sustainability profile (~50% biobased/inherent-primary biodegradable) in addition to the thermal protection benefits. The hair tresses were treated using a flat iron, and the keratin degradation and thermal properties of the polymer-treated hair fibers were analyzed using differential scanning calorimetry (DSC). Surface properties of hair was evaluated using scanning electron microscopy. To better understand the thermal protection mechanism, the polymer was compared to different variations of cellulosic polymer, including hydroxyethyl cellulose (HEC) and polyquaternium-10 (PQ-10) polymer. The polymer pretreatment significantly increases the denaturation temperature, Td, and denaturation enthalpy (ΔH) in comparison to the thermally-treated hair without a protectant. Among all the polymers that were screened, cat-hmHEC provided the highest level of thermal protection, while HEC and PQ-10 polymers provided the least level of protection at the same use level (1 w/w %). Results suggested that hydrophobicity plays a crucial role in reducing hair damage upon exposure to heat. In addition, mechanical properties of the hair were evaluated via tensile testing, revealing an improvement in elastic modulus and mechanical work of the thermally-treated hair with cat-hmHEC polymer.
Methods
A series of cat-hmHEC polymers with cationic-hydrophobic variations were evaluated at 0.1 and 1% active level in a leave-in conditioner and compared to cationic celluloses and aminosilicone polymers. The hair tresses were treated using a flat iron at 232 °C for 10 times, 10 seconds each. The treated tresses were washed with 9% SLS (0.2 g/g of hair) for 30 s, rinsed with water for 1 min, and dried at room temperature, 50% RH for at least 12 hours prior to the analyses. The thermal evaluation was performed using DSC, and the surface of the hair cuticle was analyzed using SEM. The enhanced mechanical properties were tested using a mechanical tensile test on single hair fibers. The testing was performed in the wet state.
Results
The polymer pretreatment provided significant reduction in Td and ΔH loss in comparison to the thermally treated hair without a protectant. Among all the polymers that were screened in this study, cat-hmHEC provided the highest level of thermal protection, while HEC and PQ-10 polymers provided the least level of protection at the same use level (1 w/w %). Initial results suggested that hydroxy functionality on amodimethicones significantly impacts thermal protection. It was hypothesized that cellulose, which contains higher hydroxyl contents, and hydrophobic functionality, would also improve thermal protection on hair. According to the structure-property-performance analysis, cationic charge provides no significant impact on reducing damage from thermal treatment. However, the level of hydrophobicity plays a chief role in improved thermal protection on hair. It is hypothesized that the polymer was able to form a film-like structure on the surface of the hair fiber, preventing excessive water loss caused by the heat treatment while protecting the hair fiber from direct contact with heat. The long-alkyl chain together with an adequate degree of substitution may provide another layer of thermal protection. In addition, thermally-treated hair with cat-hmHEC polymer has shown improved mechanical properties of the hair fiber in comparison to that without a polymer treatment. The results reveal insight into structure-property relationship between polymer and hair that both hydroxy and hydrophobic functionalities play a role in thermal protection.
Discussion and Conclusion
Modification of these polymers has enabled different features that provide unique benefits to hair applications. Varying structural parameters such as hydroxy/hydrophobic substitution significantly impact not only sensorial properties but also thermal properties. This learning can be leveraged and applied to other types of polymer backbone to achieve similar thermal properties. It is therefore very crucial to understand the structure-property-performance relationship to achieve performance.