1. INTRODUCTION:

Consumer prefers the hair care products which will make their hair look shiny, silky, clean, soft, manageable and healthy; a greater emphasis is led on cleansing, conditioning and the treatment of hair. This has resulted into the creation of a market for hair care products each suited for particular type of hair. The global hair care market is estimated to be more than $ 50 billion according to Euromonitor^[1]. Large numbers of multinational players are offering customized formulations accordingly to meet the consumer demand of a particular demography and ethnicity .They a are devising the new and improved delivery systems to give superior products.

Today both men and women are conscious regarding their beauty, appearancewhich is no longer a feminine thought. Personal care companies are offering product range for both men and women, thereby increasing the wide scope for ingredient suppliers, who are coming up with more multifunctional ingredients in the market.

One of the major personal care ingredient suppliers in the world is Dow chemicals. According to Erik Gyzen, Dow Chemical’s major market strategy is to offer new silicone-based formulation for Leave-in type hair conditioners^[1]. This Product being a new concept has wide scope in the hair care market. Considering the scope, we have formulated Leave-in hair conditioners and its technical evaluation was carried out. The formulation has been designed by keeping a constant percentage of ingredients capable of forming a film on the substrate, commonly used in the hair care as reported in the literature. A comparative study of their product characteristics has been done, which will help to arrive at the best combination of the raw materials to give to good working formulation and highlight the importance of the instrumental data obtained for characterizing the product. The data can serve as a good reference for designing the leave in type formulations.

The conditioners have been in use from a long time. Recent advances used in the field of the hair conditioning applications increasingly focus on the use of multifunctional ingredients in the formulation. Earlier the formulators used fatty amides, polyols, quaternary derivatives, sterols and protein derivatives. The incompatibility of these materials with the anionic surfactants has led to the use of the silicones as conditioners. The shampoos being marketed as 2 in 1 shampoos. These shampoos based on the dimethicone or related products provide much greater conditioning and performance. This has led to many companies coming up with customized silicone micro emulsion blends that are added to the shampoo formulations^[1].

Now-a-days there has been an increasing trend of using polymeric conditioners which actually increase the deposition of the conditioning aid on the hair surface. Godard and co -workers studied the nature of interaction of the cationic polymer with anionic surfactants^[2]. They showed that below the critical micelle concentration the (CMC), an insoluble coacervate phase is formed. This basically forms the principle basis for the working of cationic surfactants as conditioning agents

Researchers at Johnson and Johnson have suggested that the use of the Polyquarternium series of polymers gives better deposition when used in combination with each other^[3].Scientists at the Kao Corporation have also used nonionic surfactants to emulsify the silicone based polymeric conditioners and obtain a transparent micro emulsion of silicones^[4]. Thus it can be said that polymers invariably play great role while designing the formulations.

Polymers play important role in developing a Leave-in type formulation also. There are some polymers recently launched in the ingredient market that act as rheology modifier and also give superior sensory feel such as non-oily and non-greasy while in use. They also help in improving the deposition of the conditioner because of their film forming ability. Some of them presently in the market are the Carbopol series from Lubrizol, Leviquat series from BASF,Salcare series from Ciba chemicals and the Versagel from Ashland chemicals^[5].The role of the polymers in the present work is of rheologyand sensory modifier.

The present work has been carried out by using the Carbopol ultrez -20 water soluble polymer. Other main components of the formulations are the hydrophobic film forming materials and essentially PDMS. The PDMS has the lowest co efficient of friction and critical surface tension for the dry hair.Both these qualities point at its ability to form smooth film over the hair follicle surface and their ease of combing. Thus it ratifies the wide spread use of the silicones in the hair care formulary. Tim Morris et al.^[6] from Cognis Corporation have studied the benefits of using the fatty acid based esters as hair care ingredients. They concluded that the shampoo formulations based with these esters and fatty alcohols showed greater moisture absorption on the hair.Their deposition on the hair provided hair moisturization, ease of combing and hair gloss. In a consumer test according to panelist Sensorial evaluation of the shampoos with fatty acid esters was better than those which did not have fatty acid esters.

2. EXPERIMENTAL:

2.1 Chemicals and Auxiliaries

Cetyl alcohol, lauryl alcohol, Stearyl alcohol, Olyl alcohol and Myricetylalcohol were procured from Ms. VVF Ltd, Mumbai. Carbopol Ultrez-20 fromLubrizol Corporation, Mumbai. Polyquarternium-7 was procured from Galaxy surfactants Ltd, Mumbai. Mineral Oil, Isopropyl Myristate, Glyceryl monoleate, Glycerol monostearate, Polyethylene glycol 4000, Polyethylene glycol 6000, butylene glycol, Butylated Hydroxy toluene, citric acid, Triethanolamine and PDMS were supplied by Rarco Chemicals, Mumbai. All chemicals were used as such without any further modifications.

2.2 Method

Ten Leave-in type hair conditioners formulations were prepared. The composition was kept as follows.

Table 1 Experimental Formulation Chassis.

S. No.	Formulation
	Component	% Composition
1	Water	75-84
2	Film Forming component(mentioned in group A)	4-8
3	Polydimethylsiloxane	3-7
4	Glyceryl monoleate or Glyceryl Monostearate	1-4
5	Carbopol Ultrez-20	0.5-1
6	L-Arginine	0.1-0.5
7	Triethanolamine (30 %)	1-3
8	Polyethylene glycol 4000 or 6000	2-6
9	Antioxidant	0.05-0.5
10	Perfume	0.05-0.8
11	Ethanol	0.1-1
12	Preservative	0.1-2
13	citric acid	q.s

The formulated prototypes were made using a selected % of component from amongst those given in range mentioned in the table 1. Ten prototype formulations were made by changing the principal component (mentioned in 2^nd row of table 1) along with Glycerol monostearate or Glycerol monoleate in the formulation and named successively as LC-1 to LC-10. Rest of the formulation was kept constant throughout the study and hereto will be referred as the formulation chassis. Carbopol Ultrez 20 was used as a thickening agent and Triethanolamine (30%) was used as a neutralizer.

The combinations stated earlier have been mentioned in the table 2.

Table 2 Combinations of Principal components with Glyceryl monostearate and Glyceryl monoleate

Formulation	Major Components
LC-1	Butylene Glycol, Glycerol Monostearate
LC-2	Olyl alcohol, Glycerol monoleate
LC-3	Isopropyl Myristate ,Glycerol monoleate
LC-4	Cetyl alcohol, Glycerol monoleate
LC-5	Cetyl alcohol, Glycerol monostearate
LC-6	Stearyl alcohol, Glycerol monoleate
LC-7	Myricetyl alcohol, Glycerol monoleate
LC-8	Lauryl alcohol, Glycerol monoleate
LC-9	Mineral Oil, Glycerol monoleate
LC-10	Polyquarternium -7,Glycerol monostearate

2.3 Batch making procedure

The formulation was made in a bench top homogenizer .The first step involves the additionof CarbopolUltrez-20 into the required amount of water and dispersed at 900-1200 rpm. Triethanolamine was slowly added to above dispersion and stirred until a thick homogenous gel is formed. This is followed by the addition of the film formers component in liquid form (in case the component is solid, it’s separately melted and added) and emulsified, homogenized at 1500 rpm. Antioxidant, preservative are predissolved in the ethanol and then added to final mixture. Perfume was added in q.s. and citric acid to adjust the pH of the final formulation below 7. The formulation was homogenized at 4000-5000 rpm for about fifteen minutes, till a white colored opaque homogenized emulsion was formed.

3. TECHNICAL EVALUATION:

Since the application of the formulation is leave-in type, it is expected that the interaction of the formulation with the solid surface of the hair fiber should occur. Hence, it becomes imperative to explore possibilities of evaluating the formulation on the basis of surface parameters. In the past Jachowicz and Smewing^[7] have used texture analyzer to substantiate hair care product claims. The formulations were evaluated for following parameters using instruments as:

1) Firmness and stickiness values: TAXT-2I texture analyzer,

2) Viscosity : Rheotec R3 Rotational viscometer using L2 probe,

3) Contact angle: Goniometer,

4) Surface tension: KRUSS K100 tensiometer.

1) Firmness and stickiness values:

TAXT-2I texture analyzer with P45C 45° CONE Perspex probe, with load cell of 50 kg and test speed of 2mm/ sec was used. The texture analyzer gives values of the force (unit g) applied by the probe while penetrating inside the sample and coming out of the sample. The results are recorded as graph which shows a plot of force vs time. The values of stickiness and firmness were obtained for the ten formulations.

2) Viscosity: Rheotec R3 Rotational viscometer using L2 probe,

3) Contact angle: Contact angle was measured on the Teflon surface by using Goniometer (G-10 Contact angle meter). Three successive drops were put on the Teflon plate. The angle between the baseline of the drop and the tangent at the drop boundary was measured. An average value was calculated for each formulation.

4) Surface tension:Surface tension measurements were done using the Wilhelm/Du Nouy ring apparatus on Kruss K100 tensiometer. The values were obtained as a plot of surface tension vs. the time.

The other parameters evaluated are work of adhesion, adhesion tension and the spreading –coefficient.

Work of adhesion [8] is defined as direct measure of free energy between solid and liquid surface. It is denoted by Wa. It is calculated using the following equation.

W_a = g_LV(cos (q) + 1)…………………………….…(1)

Gibbs[8] defined adhesion tension is difference between the surface pressures of solid/liquid interface and liquid/vapor interface. It is denoted by t. It is given by

t = g_LV (cos (q)) ……………………………….……(2)

Spreading coefficient was term proposed by Harkins^[8] to predict the wettability of the solid surface by the liquid. Based on the value of spreading coefficient the efficiency of the formulation can be predicted. This value can be either positive or negative depending upon the contact angle q.

Spreading coefficient is denoted by S. The expression for calculating it is :

S = g_LV(cos (q) - 1)………………………….………(3)

In the equation (1) and (3), g denotes surface tension.

4. RESULTS AND DISCUSSION:

As Leave-in type formulation is direct application type,it’s important that it should stick to the surface of hair fibre and stay on it for longer time.It should be capable of forming a smooth film on the hair surface without much application of force and thus help in keeping the hair detangled and smooth. Table 3 shows the measured values of firmness and stickiness of the prototype formulations. The unit of force measured is g.

Table 3 Results of the Texture Analysis

Formulation	Firmness(g)	Stickiness(g)
LC1	17.02	0.18
LC2	51.47	6.22
LC3	61.98	5.72
LC4	73.38	6.63
LC5	183.35	7.17
LC6	138.79	4.94
LC7	160.19	4.75
LC8	79.94	4.24
LC9	50.12	3.26
LC10	63.37	0.21

Comparing the firmness values for formulated prototypes as shown in Table 3, it was observed that, the formulation LC-5 with combination of cetyl alcohol and glyceryl monostearate shows the highest value of firmness. Similar trend were followed with formulations LC-6 and LC-7 with higher melting fatty alcohols.Formulations LC-2, LC-3, LC-8, LC-9 and LC-10 showed a firmness valuewhich is less than 80 with LC-1showing the lowest value. Formulation LC-4 shows exceptional decrease in firmness value as compared to its counterpart LC-5.There is difference of 115 units between the firmness value of LC-5 and LC-4. The reason is the combination of the cetyl alcohol and glyceryl monoleate which has reduced the firmness of the formulation with Glyceryl monoleate being a fatty acid ester with low melting point.

Thus from a formulator’s point of view it is recommended that Leave-in type hair care formulations should incorporate the fatty alcohols with a lower melting point. Firmness value comparison, confirms that lauryl alcohol and Olyl alcohol are better than Stearyl, Cetyl and Myricetyl alcohols for Leave-in type formulations. A formulation with higher firmness will also develop problems while withdrawing the sample from packaged container.

The evaluation of the stickiness values of the developed prototype formulations showed that the formulation LC-9, LC-8 and LC-10 performed better than the others. The formulations have Lauryl alcohol, mineral oil and Polyquarternium-7 as main components respectively. From a User point of view a non-sticky formulation is better. Also as reported in the table 4, since their contact angle is also less than 90’ these formulations will wet the surface more effectively.

Although the other formulations LC-2 to LC-7 have high value of stickiness, it can be concluded that there surface adhesion on the hair fiber will be better, but since their contact angles were more than that of LC-8 and LC-10 there spreading will be low and will require more energy to spread. Logically the thickness of the film formed by these formulations will be more but then the film will be unevenly distributed on the hair.

Even after having high values of stickiness, the formulation does not give any kind of oily and greasy feeling while using it on the hair. This is because of the Carbopol polymer which helps in delivering a superior sensorial feeling.

By measuring the contact angle, the wettability of the liquid can be predicted. Wettability is of prime importance in these types of formulations, as predicts behavior conditioner on the hair surface. Table 5 shows a comparison of the contact angle recorded for the formulation prototypes.

From the spreadibilty point of view, theoretically the contact angle of water should be less than 90.From the data presented in table 5 it is observed that formulations LC-4, LC-5, LC-6 have a contact angle of more than 90.That makes them difficult to spread as compared to other formulations. This is due to their viscosity which is preventing their complete contact with the surface. Applying these formulations on the hair surface will require a higher degree of force as compared to the other formulations.. The contact angle is indirect measurement of the surface tension. Here all the formulations contain 4 % dimethicone and citric acid. The addition of the dimethicone causes drop in surface tension and the addition of citric acid causes increase in surface tension. The resultant surface tension can be indirectly predicted by measuring the contact angle. So from consumer point of view, for easy application the contact angle should be less than 90degree.

Table no 4.Surface Properties of formulations

Formulation	Contact angle	Cosine values of contact angle	Surface tension (Dynes/cm)	Adhesion tension (Dyne/cm)	Work of adhesion	Spreading coefficient
LC-1	64.0	0.43	24.57	10.57	35.14	-14.00
LC-2	75.1	0.25	32.41	8.10	40.51	-24.31
LC-3	74.4	0.27	29.59	7.99	37.58	-21.60
LC-4	96.4	-0.11	26.43	-2.91	23.52	-29.33
LC-5	99.2	-0.15	24.74	-3.71	21.03	-28.45
LC-6	90.7	-0.012	23.43	-0.28	23.15	-23.71
LC-7	81.7	0.14	24.87	3.48	28.35	-21.39
LC-8	72.7	0.29	28.90	8.38	37.28	-20.52
LC-9	75.2	0.88	27.76	24.42	52.18	-3.33
LC-10	60.5	0.4924	26.09	12.85	38.93	-13.24

Table 5 % Drop in the contact angle of water for prototype formulations

Formulation	Contact angle	Contact angle of pure water on Teflon	% drop in contact angle of water
LC 1	64	112	54.86
LC2	75.1	112	44.98
LC3	74.4	112	45.57
LC4	96.4	112	25.90
LC5	99.2	112	23.40
LC6	90.7	112	31.02
LC7	81.7	112	39.02
LC8	72.7	112	47.12
LC9	75.2	112	44.89
LC10	60.5	112	57.95

Formulation LC-10,LC-9,LC-2 and LC-3 will have good wetting of the hair surface as there contact angles are less than 90.The appreciable thing is that formulation LC-9 which contains the mineral oil shows very good spread ability on a hydrophobic surface.

Rather than relying on sensorial data and characterizing the formulation it will be good to have a look into fundamental properties and compare them to see the variation caused because of the change in the key component in the formulation chassis. All the recorded surface tension values fall in the range of the 20-33 dynes/cm. The measured values of surface tension are less than the surface tension of pure water which is 72 dynes/cm. This can be attributed to the presence of polydimethylsiloxane (PDMS) in water resulting in drop in surface tension .The surface tension of pure polydimethylsiloxane is 20 mN/m. All the recorded values of the formulation are very close to that of pure polydimethylsiloxane which indicates that the spreadibilty will be satisfactory.

From table 5 It can be concluded that formulations LC-4. LC-5 and LC-6 and LC-7 have a low value of adhesion tension, work of adhesion and surface tension values as compared to formulation LC-2, LC-3, LC-8, LC-9 and LC-10. That gives an indication that spreadibilty of LC-4, 5, 6 and 7 will be better than LC- 2, 3, 8, 9 and 10 on the hydrophobic hair surface, but this ability was offset by the high values of spreading – coefficients and viscosity. As mentioned previously in formulations LC -4, 5, 6 and 7 had higher melting fatty alcohols which resulted in the high viscosities. Also the combination of cetyl alchohol with Glyceryl monostearate resulted in a very high viscosity and the formulation in spite of having low surface tension will not spread evenly. A higher value of spreading coefficients in LC-4, 5, 6 and 7 indicates that these formulations will require a high energy input to spread as compared to other formulations.

5. CONCLUSION:

It can be concluded that for leave-in type conditioners fatty alcohols with lower melting pints are better suited. Same is evident is case of fatty acid esters of glycerin. Glyceryl monoleate is better suited than glyceryl monostearate from the formulation technical evaluation, it can be concluded that the measured values related to surface behavior can serve as a good indicator of the formulation performance. It will also help the formulator to correlate the data obtained from instruments with that of the sensorial panel thus making it realistic. This will help in getting a good insight into the consumer preference from a technical point of view.

From a formulators point of view the formulation presented in this work can serve as a reference formulation and help him to choose the most appropriate raw materials and techniques to design a consumer relevant formulation.

6. REFERENCES:

1) Nancy Jeffries. Global Hair Care Report: a feel for Innovation. In Hair Care :From Physiology to Formulation, Edited by Angela Kozlowski,Allured Publishing,Carol Stream, Illinois 2008;pp 23-28.

2) ED Goddard,Polymer surfactant interaction, Parts I and II ,chapters 4 and 5 in Interactions of Surfactants with Polymers and Proteins ,ED Goddard and KP Ananthpadmanabhan,Boca Raton,Florida;CRC Press (1993)

3) US Pat application 20030176303AI,SM Neimec, H Yeh, R Gallagher and KL Hoe, filed by Johnson and Johnson(Sep 18,2003)

4) US Pat 6,803,050,H Denzer, H Abe ,M Pytlik, R Jansen and A Buhmann ,assigned to Kao(Oct 12 , 2004)

5) Robert Y. Lochhead and Lisa R.Huisinga, Advances in Polymers in Hair styling. In Hair Care :From Physiology to Formulation, Edited by Angela Kozlowski,Allured Publishing,Carol Stream, Illinois 2008;pp 283-294

6) Morris et al. Esters from Vegetable sources with Care Effects for Hair. In Hair Care :From Physiology to Formulation, Edited by Angela Kozlowski,Allured Publishing,Carol Stream, Illinois 2008;pp 155-167

7) J Jachowicz and J Smewing ,Using texture analysis to substantiate hair care claims, Cosmetics and Toiletries 121(9) 69-76( 2006)

8) TharwatJTadros, Surfactants as Dispersants and Stabilization of Suspensions, Applied Surfactants :Principles and Applications; WILEY VCH Verlag Gmbh and Co.KGaA.Wienhiem (2005)

Received on 04.03.2013 Modified on 29.03.2013

Asian J. Research Chem. 6(4): April 2013; Page 398-402