Biology HL's Sample Internal Assessment
Investigation on the effect of natural & synthetic shampoos on the tensile strength of hair
Table of content
Research question
How does the tensile strength of hair depends on the percentage concentration and the type of shampoo (natural- Khadi Herbal Amla and Khadi Herbal Henna; synthetic – Tresemme and Sunsilk) it is exposed to, determined using a force sensor?
Rationale
Use of cosmetics and the science behind them has always been a major topic of interest for me. Hair care and dermatology are one of the major sectors of the cosmetic industry across the globe and are also one of the major applications of chemical and biological science. When investigating hair products and shampoos, one comes across numerous conflicting researches and concepts, recent researches have debated the use of herbal alternatives instead of commercial synthetic products to be more conducive for the growth an strength of hair. Not only shampoo, but several other synthetic cosmetic products has been replaced by herbal formulations. These conflicting concepts have led me to conduct an experiment to investigate the effect on natural and synthetic shampoos on hair.
Background information
Hair
Hair comprised of natural oils and Keratin, which is a fibrous protein and the major constituent of hair shaft. It is synthesised by the cells in the cuticle of the germinal layer and has an alpha helix secondary structure. The ternary structure and quaternary structure of Keratin is mainly held in place by interactions such as the Hydrogen bonds, ionic interactions and disulphide linkages.
Apart from keratin, hair also contains elements like Ca, Cd, Cr and more along with some lipids. The minerals reach the hair follicles through blood circulation while the lipids are produced from the cells in the cortex. The minerals provide nutrition to hair while lipids make the hair fibre impermeable in nature and help in maintaining the force of cohesion between them. Sebaceous glands play a major role to maintain the quality of hair, they secrete mevalonic acid which condenses with fatty acids to produce sterols. The sterol and cholesterol together make a lipid film which is hydrophilic in nature. This lipid mixture helps to keep the hair shiny and silky. Excess of this lipid layer can give a greasy and dull appearance to hair while the lack of it makes it look dirty.
The quality of hair can be measured in terms of physical parameters like strength, tensile strength, elasticity and opaqueness. The tensile strength of hair is a major contributor to determine whether the hair is healthy and nourished or not. Since hair fibre has the property of elasticity, i.e the property of a material to return to its original shape or position after being stretched, it has naturally high tensile strength. However this strength can be affected by numerous factors such as nutrition, ageing, diet, applicants, conditioning and more.
Role of shampoo
Shampoo was first launched in the year 1930 under the name of the first shampoo product – ‘Drene’. History reveals that women in South Asian countries had a tradition to keep long hair. Soaps and in some cases even mud was used to cleanse dirt from hair. The problem detected was that soap can produce scum in the scalp especially if the water used is hard which is tough to rinse off.
The basic general composition of a shampoo contains:
- Synthetic detergents – both cationic and anionic. These are used to remove dirt from hair.
- Sequestering agents – Complexing reagents like EDTA, Vitamin-C which complexes with heavy metal ions in hair to remove them.
- Opacifiers – These compounds alter the physical texture and optical shine of hair. Thickeners are also added to control the viscosity of hair.
- pH adjusters – Hair shaft needs an optimum pH of 3.67. Shampoos are designed to maintain this pH. The pH of a shampoo must not exceed 5.5 as that would be harmful for scalp.
Apart from the above, conditioners, foaming agents and preservatives are also used.
Composition of the shampoo used
Khadi Herbal Amla is a herbal shampoo which is composed of Amla, Reetha, Jatamansi, Bhringraj, Almond oil, and some essential oils. While the Khadi Herbal Henna shampoo contains Henna, Neem, Basil, Rosemary and Thorn apple. Tresemme is composed of surfactants like Dodecylsulfonate, sodium lauryl sulphate, Titanium oxide and EDTA along with other inorganic sequestering and odouring agents. Sunsilk is a product of Unilever mainly made of Sodium dodecyl sulphate, EDTA, dodecyl benzene sulphonate and amidopropyl betaine along with many other inorganic supplements.
Aim
This research’s aim was determining how natural (Khadi Amla & Khadi Henna) and synthetic shampoos (Tresemme & Sunsilk) effect the tensile strength of hair, along with investigating whether the concentration of shampoo also plays a role in affecting the tensile strength, and if there is a particular tolerance limit for shampoo or what the ideal recommended dose would be. This investigation will be carried out with the help of a force sensor to determine the breaking points of hair strands, In order to to determine the difference in tensile strength.
Hypothesis
Research hypothesis
As synthetic shampoos contain a high number of artificial and damaging detergents which are not present in natural shampoos, it can be predicted that natural shampoos will improve the tensile strength of hair and hence hair strands exposed to natural shampoos will have higher tensile strength and higher breakage points.
Alternate hypothesis
As synthetic shampoos contain a high number of detergents which are not present in natural shampoos, it can be predicted that synthetic shampoos improve the tensile strength of hair due to the presence of such components. And so, the hair strands exposed to synthetic shampoos will have higher tensile strength and higher breakage points.
Null hypothesis
Results will show no or very little difference in the tensile strengths of hair strands, indicating that there is no difference between the effect of natural and synthetic shampoos on the tensile strength of hair strand.
Variables
Independent variables
Type of Shampoo (Natural and Synthetic) -
To be precise, the term natural here indicates that the shampoo claims to made out of ‘Ayurvedic’ or ‘Herbal’ formulations. Synthetic ones indicate that the shampoos are mainly based on synthetic detergents with inorganic components as sequestering or pacifying agents.
The natural shampoos chosen are Khadi Herbal Amla shampoo and Khadi Herbal Henna shampoo while the synthetic shampoos chosen are Tresemme & Sunsilk.
Percentage concentration of shampoo used -
The concentration of shampoos is varied to determine if there is a correlation between the quantity of shampoo and the resulted tensile strength of the hair strands. This will also address the common concept of “using more shampoo for gaining better hair results” to determine whether it is true or a myth. The concentrations are 10.00%, 20.00%, 30.00%, 40.00% and 50.00%. All these concentrations were achieved by adding requisite amount of shampoo to tap water in a test tube. For example, to make a 10.00% shampoo solution, 1.00 cm3 of shampoo was added to 9.00 cm3 of tap water.
Dependent Variable
Tensile strength (measured using a force sensor)
The difference in the tensile strength of the hair strands, after being exposed to natural and synthetic shampoos of different concentration is measured to determine the effect of these shampoos and concentrations on hair.
| Variable | Why is it controlled? | How is it controlled? |
|---|---|---|
| Time | Longer the duration, the hair strand is in contact with the shampoo solution, more the effect of the shampoo on hair. | All hair strands under study were in contact with the shampoo solution for 24 hours (1 day). |
| Length of hair strands | The length of the hair strand will have an effect on the extent to which the shampoo changes the properties of it. | All the hair strands used were of 10 cm length. |
| Type of hair samples used | Variations in the type of hair samples used will introduce sampling error and make it an unfair comparison. | All the hair strands used were of 10 cm length.All hair strands used were of the same length and of the same origin. |
Fgure 1 - Table On Controlled Variable
| Apparatus | Capacity | Quantity |
|---|---|---|
| Graduated measuring cylinder | 100 cm3 | 1 |
| Test tube | ---- | 20 |
| Test tube stand | ---- | 1 |
| Force sensor | Max: 500 g | 1 |
| Ruler | 15 cm | 1 |
| Scissor | ---- | 1 |
| Forceps | ---- | 1 |
| Filter paper | ---- | 1box |
| Rubber band | ---- | 20 |
Fiure 2 - Table On Chemicals And Apparatus Required
Safety precautions
- Protective clothing like lab coats, safety masks and safety gloves were used.
- Any consumable eateries were not allowed inside the laboratory.
Procedure
Preparation of hair strands
- Hair samples were obtained from the same area of scalp and of the same source.
- All the hair strands were cut to a length of 10 cm. A ruler and a scissor were used for this.
- 80 such hair strands were made.
Determination of tensile strength of hair strands:
20 test tubes were taken. These test tubes were divided into five groups- 10%, 20%,30%,40% and 50% - each group having 4 test tubes. The composition of the test tubes are described in the table below:
| Test tube label | Shampoo added | Volume of shampoo added in cm3 | Volume of water added in cm3 | Percent strength |
|---|---|---|---|---|
| A-1 | Khadi Amla | 1.00 | 9.00 | 10.00 |
| A-2 | Khadi Henna | 1.00 | 9.00 | 10.00 |
| A-3 | Tresemme | 1.00 | 9.00 | 10.00 |
| A-4 | Sunsilk | 1.00 | 9.00 | 10.00 |
| B-1 | Khadi Amla | 2.00 | 8.00 | 20.00 |
| B-2 | Khadi Henna | 2.00 | 8.00 | 20.00 |
| B-3 | Tresemme | 2.00 | 8.00 | 20.00 |
| B-4 | Sunsilk | 2.00 | 8.00 | 20.00 |
| C-1 | Khadi Amla | 3.00 | 7.00 | 30.00 |
| C-2 | Khadi Henna | 3.00 | 7.00 | 30.00 |
| C-3 | Tresemme | 3.00 | 7.00 | 30.00 |
| C-4 | Sunsilk | 3.00 | 7.00 | 30.00 |
| D-1 | Khadi Amla | 4.00 | 6.00 | 40.00 |
| D-2 | Khadi Henna | 4.00 | 6.00 | 40.00 |
| D-3 | Tresemme | 4.00 | 6.00 | 40.00 |
| D-4 | Sunsilk | 4.00 | 6.00 | 40.00 |
| E-1 | Khadi Amla | 5.00 | 5.00 | 50.00 |
| E-2 | Khadi Henna | 5.00 | 5.00 | 50.00 |
| E-3 | Tresemme | 5.00 | 5.00 | 50.00 |
| E-4 | Sunsilk | 5.00 | 5.00 | 50.00 |
Figure 4 - Table On Determination Of Tensile Strength Of Hair Strands
In each of the test tube, five hair strands were transferred using a forcep. The test tube was covered with a filter paper and tied with a rubber band. After 24 hours, (same time on the next day), the hair strands were taken out. All the hair strands were then washed under a stream of running tap water. After washing, the hair strands were dried using a hair dryer. Then the hair strand was tied with a force sensor and the force sensor was secured at a wall. The force applied through the sensor was increased gradually using the screw and the force at which the hair strand breaks was recorded. The same process was performed for each and every hair strand.
