Emily Bazemore, Ciba Specialty Chemicals Corporation, USA
Abstract
Chemical treatment of hair fibers enable endless fashion statements through variations of the color, appearance and style of their hair. Examples of such treatment include coloration, relaxing, bleaching, straightening etc.
On the other hand, hair that has been chemically treated will tend to be dry, brittle and fragile and will easily break during combing so that special considerations are needed for conditioning. This presentation will review the current status of chemical treatment of hair, investigate the scope of damage that such treatments cause, and discuss the strategies and progress in developing conditioning polymers designed to reduce the damage, and improve the feel and texture and overall appearance of the hair.
Introduction
Ciba® TINOCARE® PQ6H is a new conditioning polymer from Ciba Specialty Chemicals, specifically designed to be used in relaxer straightening applications. It is a structured, high molecular weight, water soluble DADMAC polymer that is supplied as an aqueous solution having an active content of 20% and an average molecular weight of > 700,000 g/mol.
It provides excellent conditioning and softness to hair. It has been developed to meet the following needs:
- Condition the hair with a high molecular weight polymer to add softness to the hair.
- Reduce grooming friction to hair that has previously been chemically treated and may experience cuticular damage. If the scales are broken, chipped or uplifted, hair fibers when rubbed together or combed will have a tendency to break.
- Helps maintain straight style during relaxer process by not interfering with the chemical processing.
- Helps minimize breakage by forming a film on the hair. This allows hair to retain some strength relative to the hair that has nothing on it. It will also help with elasticity. In the wet stage, hair that is combed will not tend to be pulled as hard because the comb glides over the film on the hair protecting the cuticles.
- Provides lubricity to the hair fiber by enveloping a film on the hair to make the hair feel much smoother.
The relaxing process
Relaxing is very damaging to the hair as the process is performed at a pH between 11 and 13. The relaxer treatment swells the hair, opening up the cuticles, exposing the cortex to the relaxer. The alkaline agent penetrates the hair fiber, and diffuses into the endocuticle. Inside the cortex the relaxer reacts with the keratin protein, breaking the structural bonds. Breakage of the disulfide bonds denatures the hair so that the fiber can be extended to a straight configuration. The hair is shampooed and a neutralizing product is used to remove the alkaline agent. This initiates the formation of lanthionine cross-links. This locks in the new shape of the hair and closes down the cuticle. Extensive cuticular damage occurs and there is an increased level of cysteic acid with a negative charge (1).
To minimize the damage caused by this chemical treatment, Tinocare PQ6H should be added to the relaxer base to provide conditioning to the hair fibers. It can also be added to the normalizer to condition and lubricate the hair by making it easier to comb. Lastly, it can be added to the after treatment conditioner product to lubricate and condition the hair to reduce grooming friction and minimize breakage.
We performed the following experiments using Kinky hair sourced from DeMeo Brothers and International Hair Importers, Inc. in order for us to look at the damage caused by Relaxers and how incorporating Tinocare PQ6H into the product can improve the condition of the hair and not impede the relaxing process.
Straightening
Procedure
To test whether Tinocare PQ6H interfered with the relaxing process, three commercial relaxer products were compared with the Ciba Prototype containing Tinocare PQ6H and a relaxer formula with no Tinocare PQ6H which was used as the control. The process used was as follows:
- l Kinky Hair Tresses were treated with the relaxers.
- l Each commercial relaxer and the test relaxer was mixed according to the standard instructions.
- l Each of the relaxers was applied to three African (kinky) hair tresses from International Hair Importers and three from DeMeo Bros. and massaged with a relaxer brush.
- l The relaxer treatment was applied and smoothed until the hair was straightened.
- l The relaxer was rinsed thoroughly for 3 minutes or until all traces of relaxer was gone. Each tress was shampooed with a non- conditioning shampoo (Pantene Pro- V Clarifying Shampoo) to remove all traces of relaxer.
- l Samples were laid flat and observed visually for straightness.
Conditioning improvement
To test whether Tinocare PQ6H improved the condition of the hair, the following experiment was performed. A basic sodium hydroxide relaxer formulation was developed incorporating Tinocare PQ6H at 2% use level or 0.4% active. A basic relaxer formulation was developed without Tinocare PQ6H and served as the control sample. The relaxer was applied to African (Kinky) hair tresses with a relaxer brush and allowed to straighten for (15-20 minutes). The relaxer was rinsed thoroughly from the hair for 3 minutes or until all trace of relaxer was gone. All hair samples were analyzed by scanning electron microscope (SEM) by Textile Research Institute.
The SEM results of the relaxed hair with and without the use of Tinocare PQ6H as the conditioning agent are illustrated in Figures 2A, 2B, 3A and 3B. As can be seen in the pictures, the SEM results of the relaxed hair fiber relaxed without Tinocare PQ6H illustrated that the cuticle scales were extremely damaged. The cuticles were uplifted, cracked and very uneven. The hair fiber also exhibited longitudinal cracks along the hair shaft. Relaxing was seen to be very detrimental to the hair fiber. This leads to the hair being fragile and easily broken.
The SEM picture of the hair fiber which was relaxed with the incorporation of Tinocare PQ6H at 2% use level into the relaxer formula was visually seen as less damaged. The high molecular weight of the Tinocare PQ6H helps to 'cement' the cuticles as it forms a layer of film on the hair.
In Figures 4A-C, the SEM pictures shows hair fiber treated with a relaxer containing (0.4% active) Tinocare PQ6H and neutralized with a normalizing reconstructor lotion containing (0.4% active) Tinocare PQ6H and SALCARE® SC96. Again, we noticed the cuticles having a thin film and the edges of the cuticle scales are cemented down and therefore protected.
Diastron analysis
Our next step was to look at the reduction of combing force by Diastron analysis. In this study, the hair fibers which were relaxed with the top three commercial market samples were tested versus a prototype relaxer incorporating 2% Tinocare PQ6H.
Combability can be defined as the subjective perception of the relative ease or difficulty with which human hair can be combed. It depends on the magnitude and on the fluctuations of the forces that oppose combing. Combability is an important attribute when judging the ‘condition’ of human hair. Improved combability is perceived as the hair being in better condition. Other concepts closely associated with combability are manageability and mechanical damage, which is done to the hair with the combing process. This is accelerated if the hair is hard to comb or untangle. Therefore, combability is an important factor when judging the performance of hair care products.
Test protocol
- l The top three no-lye commercial relaxers were used in this study.
- l A no-lye relaxer prototype was formulated with 2% Tinocare PQ6H.
- l Each relaxer was mixed with liquid activator in accordance with manufacturer instructions.
- l The relaxer was applied to three African (kinky) hair tresses and massaged with a relaxer brush.
- l The relaxer treatment was applied until straightened. l l The relaxer was rinsed thoroughly for 3 minutes or until all traces of relaxer was gone.
- l All samples were analyzed by the Dia-Stron Miniature Tensile Tester Mtt170 and evaluated for hair sensory.
- l Each of the triplicate tresses were run five times and averaged. The lowest number average indicates the most reduction in combing force or the most conditioned hair tress. Results are shown in Table 1.
To determine if a consumer is able to notice the difference, a five person expert panel evaluated and scored the hair tresses based on a 5 point scale with 1 being soft and 5 being harsh. The results are listed in the Table 1. The Commercial relaxer #1 scored 4, the Commercial #2 relaxer scored 3, the Commercial #3 relaxer scored 5, and the prototype relaxer containing Tinocare PQ-6H scored 2. The hair tresses conditioned with Tinocare PQ6H were felt as the softest. These results were consistent with the Diastron analysis results.
pH Stability
Stability of the conditioning polymers is very important as they must remain intact in either acidic or alkaline mediums and still preserve the efficacy of the polymer. This experiment was conducted in order to check for pH stability of the Tinocare PQ6H polymer in both high and low pH but also during heated storage.
Procedure
Various conditioning polymers were evaluated at low pH (2) and high pH (13). They were visually evaluated for precipitation and odor. The polymers were re-evaluated after one week in the oven at 45ºC. 1% active solutions were prepared using the following conditioning agents: Polymer A, Polymer B, Polymer C, Polymer D, Tinocare PQ6H, Experimental Polymer # 1203-03, and Polymer E.
A 1% active solution was prepared and the pH of each solution was measured and then lowered to 2 using a 10% phosphoric acid solution. The samples were then evaluated for precipitation and odor.
Another 1% active solution was prepared and the pH was measured and then raised to 13 using sodium hydroxide pellets. The samples were evaluated for precipitation and odor.
Stability results concluded that no precipitation occurred and Tinocare PQ6H maintained stability in both low and high pH medium initially and during 45ºC stability storage.
In the final two experiments, samples were measured with relaxed hair containing 2% Tinocare PQ6H in a sodium hydroxide base relaxer and with a test relaxer containing no conditioning polymers. The following protocol was followed for treatment of the hair fibers:
- l A basic sodium hydroxide base relaxer formulation was developed incorporating Tinocare PQ6H at 2% use level or 0.4% active.
- l A second basic relaxer formulation was developed without Tinocare PQ6H and served as the control sample.
- l The relaxer was applied to African (kinky) hair tresses with a relaxer brush and allowed to straightened (15-20 minutes).
- l The relaxer was rinsed thoroughly for 3 minutes or until all traces of relaxer was gone.
- l Samples were left to air dry and then analyzed.
Low load friction
The load friction method was developed by TRI and is designed to measure the friction between fibers as they slide past each other. During combing or brushing, the fibers must slide past each other as the hair is groomed; lower friction makes this easier. In this study, all the fiber samples were measured against a piece of stainless steel wire approximately the thickness of human hair (diameter=0.002 inch). This wire provided a constant surface against which all fiber samples were evaluated for comparison.
Low load friction is basically measuring the surface roughness of a particular fiber.
The objective of this phase of the project was to measure the low load friction of single fibers taken from twelve samples of relaxed African Hair.
Test protocol
- l Friction measurements were performed on a minimum of 7 single fiber specimens from each of the samples of relaxed African hair in the dry condition at 22°C and 65% RH.
- l Low load friction was measured using the TRI/Scan™. This apparatus measures small forces with a Cahn® microbalance and features a computer controlled stage. Each fiber specimen was secured by the root end to a small wire hook in order to measure the friction in the with-scale direction.
- l The hook was attached to the microbalance and a weight W secured onto the other end of the fiber. All friction measurements were measured against a 50 mm diameter stainless steel wire which was attached to a small U-shaped bow which was connected to a micrometer gauge.
- l The hair fiber and the stainless steel wire were brought into contact at length L below the attachment point of the hang down wire on the balance and the micrometer gauge was used to move the horizontal fiber over a specified distance d so that the desired angle q (theta)was formed. The following formula was used to calculate the normal force (FN) between the fiber and the wire from angle q and weight W:
^
FN = Wsinq
The weight clipped to the fiber had a mass of 512 mg and distance d was adjusted to provide a normal force of approximately 8 mg. The force of friction was recorded as the horizontal wire slides down the vertical fiber at a speed of approximately 1 mm/minute for approximately 20 mm of the fiber surface.
Measurements were performed on at least 7 specimens from each of the samples.
The static friction, which is determined by the force necessary to initiate movement of the fiber and the wire past each other, seems to be more meaningful in characterizing the surface roughness.
Friction is characterized by a coefficient of friction (COF) which is the ratio of the frictional force to the normal force. Because relaxed hair is damaged, the cuticular surface is rough or damaged. The lower the number, the smoother or less damaged the hair is. The higher the number, the more damaged the fiber is.
The results concluded in the overall average Frictional Forces show that the lowest COF was exhibited by the sample containing Tinocare PQ6H, which reduced the surface damage roughness of the cuticles. The highest COF was exhibited by the control sample which did not contain Tinocare PQ6H. The hair tress exhibited greater cuticular surface damage and roughness.
Bending rigidity
Bending rigidity is measured as being proportional to the force required to deflect the fiber a certain distance. Samples with lower values indicated stiffer fibers. Bending rigidity is dependent on the cross-section area and shape which was not measured in this study since the subjective ‘feel’ of the fiber or assembly of fibers does not take cross-sectional area and shape into consideration.
Test protocol
- l Bending measurements were performed on twelve samples of relaxed African hair in the dry condition (22°C and 65% RH=Relative humidity.
- l Bending rigidity was measured using the TRI/Scan apparatus and the cantilever bending method.
- l For each fiber sample, single fibers were selected which had straight sections approximately 1 cm in length.
- Six specimens were prepared which best met the selection criteria.
- l Each specimen was mounted on a positioning device with one end rigidly secured and the remainder of the fiber protruding horizontally. Using the micrometer on the positioning device, the sample was maneuvered both horizontally and vertically so that the microbalance hook would contact the fiber at a precise displacement from the secured end once the stage was lowered.
- l The horizontal displacement is called the bending length L and for this study, the bending L length was 3.0 mm for all specimens.
- l The test was run by moving the stage at a slow downward speed of 0.01 mm/sec and concurrently measuring the force detected by the microbalance. As the hook makes contact and bends the fiber, the force/position responses is the ratio F/D where F is the bending force (in mg) and D is the bending distance (in mm). Once bending length L (3.0 mm) and F/D are known, bending rigidity R (in mg/mm2) can be easily calculated using the following equation:
R = FL3
3D
The results for the bending rigidity data for the samples were generally high, however, the relaxed hair sample containing Tinocare PQ6H showed more bending or softness than the control sample. Bending rigidity, as used in reporting the results, is proportional to the force required to deflect the fiber a certain distance. Samples with lower values flexed easier and could be considered ‘softer’ while higher values indicated stiffer fibers. Data from previous studies at TRI/Princeton using untreated hair has yielded lower values of bending rigidity but these studies have used Caucasian hair which is generally thinner than African hair.
Conclusion
Chemical treatments which include coloration, relaxing, bleaching, and straightening cause extreme damage by introducing alkaline or acidic agents onto the hair fibers. It would be beneficial for a conditioning polymer like Tinocare PQ6H be used in the end products to protect the hair. Studies have shown that Tinocare PQ6H reduces the damage caused by chemical treatments as well as improve the feel and texture and overall appearance of the hair fiber.
Acknowledgements
I wish to acknowledge Claire Schwenker, Bernice Ridley, Jianwen Mao, Colleen Rocafort and Yolanda Davis for supplying specific information for this paper. I would also like to acknowledge Yash Kamath, Ph.D. and Donald Harper, Staff Research Scientist from Textile Research Institute (TRI), Princeton, NJ for useful discussions on Low Load Friction Method, Bending Rigidity Method and for conducting Studies of African hair utilizing Scanning Electron Microscopy (SEM) for this research.