Water Soluble Polymers in Hair Care

18

WATER-SOLUBLE POLYMERS IN HAIR CARE

Prevention and Repair of Damage during Hair Relaxing

Ali N. Syed, Wagdi W. Habib, and Anna M. Kuhajda

Avlon Industries

5401 W. 65th Street

Bedford Park, Illinois 60638

1. ABSTRACT

Alkaline hair relaxers used to straighten excessively curly hair, usually African-

American hair, often cause considerable hair damage. One of the effects of straightening

the hair with relaxers is a loss in tensile strength due mainly to breakage of disulfide and

hydrogen bonds. This loss in tensile strength leaves the hair more susceptible to breakage

and cuticle erosion from subsequent grooming. The damaging effects of relaxer treatment

are not limited to disulfide bond breakage alone. Another cause of hair damage during re-

laxing is swelling of hair fibers during the highly alkaline treatment. During a conven-

tional hair relaxer treatment, the hair swells by 50% or higher, and another 20% upon

rinsing. When hair swelling is not controlled, the hair develops radial and longitudinal

cracks again rendering the hair susceptible to breakage from combing and brushing. This

study presents results on the application of cationic polymers to strengthen hair during re-

laxing, and non-ionic polymers which control hair swelling.

2. INTRODUCTION

Water-soluble and water-dispersible polymers are widely used in the cosmetics in-

dustry in general, and in hair-care products in particular. Natural water-soluble polymers

such as starches and gums have been used in hairstyling products for thousands of years.1

Early formulations used for setting and styling hair were generally aqueous solutions or

hydroalcoholic gels of polymers such as Gum Arabic, Karaya gum, shellac, and alginates.

These early mucilage-based concoctions were heavy and became tacky when exposed to

humidity in the atmosphere.

Water Soluble Polymers, edited by Amjad

Plenum Press, New York, 1998 231

232 A. N. Syed et al.

Today, chemists in the cosmetic industry have a large number of new, synthetic

polymers to select from. Modern hair care formulations utilize polymers, copolymers, and

terpolymers made from a large variety of functional groups. Polymers in the hair care in-

dustry are broadly classified based on their ionic charge into cationic, anionic, non-ionic,

and amphoteric categories. Utilization of these polymers in combination with other addi-

tives in the cosmetic industry provides almost unlimited possibilities of conditioning, re-

pairing, strengthening, forming, and overall enhancing the properties of the hair. Hair

products containing conditioning polymers help prevent mechanical damage, and thus

maintain the strength and integrity of hair by reducing the force required to comb through

the hair.2

In addition to preventing damage from combing, attempts have been made to re-

duce damage during chemical treatment.3 We have found applications and uses of a class

of cationic polymers which strengthen the hair during relaxing, and non-ionic polymers

which reduce the swelling that the hair undergoes during a highly alkaline chemical treat-

ment. Before discussing the cationic and non-ionic polymers of particular interest, the fol-

lowing are examples and applications of anionic and amphoteric polymers.

3. LITERATURE REVIEW

3.1. Examples of Anionic Polymers

Figure 1 shows an example of an anionic polymer, polyacrylic acid. B.F. Goodrich

(Cleveland, OH) manufactures a series of carbomers (molecular weight approximately

450,000 to 4,000,000 daltons) sold under the trade name Carbopol.4 These polymers are

used as thickeners and emulsifiers in cosmetic preparations as well as for styling and hold-

ing the hair. Table 1 shows a prototype formulation of a hair styling gel utilizing polyacrylic

acid.5 CTFA is the acronym for the Cosmetic, Toiletry, and Fragrance Association.

Another example of a commonly used anionic polymer includes copolymer of vinyl

acetate and crotonic acid. Figure 2 shows the chemical structure vinyl acetate (VA)/Cro-

tonates copolymer. In cosmetic formulations, it is a partially or completely neutralized co-

polymer used as a hair fixative in hair sprays. An example of a formulation containing this

polymer is shown in Table 2.6

3.2. Examples of Amphoterics

An example of an amphoteric polymer is shown in Figure 3 (Amphomer®, National

Starch). This polymer is used as a hair conditioner and fixative to provide more body,

style, and manageability.7 An example of a formulation containing this polymer is shown

in Table 3.8

Figure 1. Homopolymer of acrylic acid (CTFA name: Carbomer).

Water-Soluble Polymers in Hair Care 233

Table 1. Prototype hair styling gel with

poly(acrylic acid)

Ingredient Percentage

Water 94.6

Methylparaben 0.2

Imidazolidinyl urea 0.3

Carbomer 1 .0

Triethanolamine 1.3

Hydrolyzed animal protein 0.5

Fragrance 0.1

Figure 2. Copolymer of vinyl acetate and crotonic acid (CTFA name: VA/Crotonates copolymer).

3.3. Examples of Cationic Polymers

Figures 4 and 5 illustrate examples of a class of cationic polymers, quaternary am-

monium polymers, commonly used in hair care formulations. Polyquaternium-6 is a

highly substantive polymer for conditioners, while Polyquaternium-7 possesses film-form-

ing and conditioning properties.9 Both polymers have been utilized for their mildness in

shampoos as well as for their conditioning properties.10 An example of a patented condi-

tioning relaxer formula is shown in Table 4.11

Figure 6 shows another example of a commonly used cationic polymer called

Polyquaternium- 10. This polymer is a substantive conditioner for personal care products

which is compatible in a wide range of anionic, amphoteric, nonionic, or cationic systems.12

This polymer, when incorporated into conditioners, has been shown to significantly reduce

combing force, thus reducing the mechanical damage to the hair from grooming.13 A patented

formula of a detangling shampoo with Polyquaternium-10 is shown in Table 5.14

The following examples of cationic and non-ionic water-soluble polymers have been

the focus of our study. Figure 7 illustrates a cationic polyamine, which is a secondary

amine polymerized with epihalohydrin and further cross-linked with the addition of a

small amount of ethylenediamine to form a polymer of the structure shown below (mo-

Table 2. Pump hair spray with VA / Crotonates copolymer


VA/Crotonates copolymer 5.00

AMP 0.40

Quatemium-6 0.15

SDA 40 94.45

Fragrance q.s.


Where R1 & R2 = (hydroxyl) alkyl

Figure 3. Acrylic resins with both cationic and carboxylic groups (CTFA name: Octylacrylamide/acrylates /buty-

laminoethyl methacrylate polymer).

Table 3. Non-aerosol styling spritz with amphomer


AmphomerR

8.00

AMP 1.38

Dimethicone 0.20

Ethanol 90.42

Fragrance qs.

lecular weight approximately 1,000,000 daltons). In our study, this cationic polyamine is

shown to enhance the elasticity and strength of the hair.15

3.4. Examples of Nonionic Polymers

reduces damage during relaxing by reducing hair swelling.16

Figure 8 shows an example of a hydrogenated starch hydrolysate that we have found

Figure 4. Dimethyl diallyl ammonium chloride homopolymer (CTFA name: Polyquatemium-6).


Figure 5. Dimethyl diallyl ammonium chloride with propanamide copolymer (CTFA name: Polyquaternium-7).

Table 4. Conditioning relaxer containing

Polyquaternium 6 or 7

Ingredients Percentage

Petrolatum 23.0

Mineral oil 14.0

Fatty alcohol 7.0

Ceteth 20 2.0

PEG 60 lanolin 1.5

Simethicone 0.1

Deionized water 44.4

1 .0

Calcium hydroxide 5.0

Propylene glycol 2.0

Polyquaternium 6 or 7

3.5. Simplified Illustration of the Physical Structure of the Hair

Human hair consists of highly organized, keratinized cells. A cross-section of a hair

fiber shows three main sections: cuticle, cortex, and medulla as shown in Figure 9. Scan-

ning electron micrographs are shown illustrating cuticle and cortex in Figures 10 and 11,

respectively (Reproduced with permission from Avlon Industries).

Hair can be damaged from chemical, environmental, or mechanical forces. The fo-

cus of our study is prevention of chemical damage from a commonly used procedure to

straighten excessively curly hair called lanthionization. Damaged hair can be “repaired”

by application of cationic polymers which attach to negatively charged damaged sites re-

storing the hair’s sheen, feel, and appearance.18 However, this procedure is temporary and

does not address the problem of preventing tensile strength loss and breakdown of the in-

ternal structure of the hair.

Figure 6. Hydroxyethyl cellulose with trimethyl ammonium substituted epoxide (CTFA name: Polyquaternium-

10).


Table 5. Detangling shampoo with Polyquatemium- 10

Ingredients Percentage

Deionized water 75.00

Methylparaben 0.20

Imidazolidinyl urea 0.30

Disodium EDTA 0.20

Polyquatemium- 10 1.50

Sodium lauryl sulfate 3.50

Disodium cocoamphodipropionate 8.00

Trideceth-7 carboxylic acid 7.00

Lauramide DEA 3.00

Glycol stearate 1.00

Fragrance 0.30

Figure 7. Cationic polyamine.

Hair relaxers change one-third of the disulfide bonds to lanthionine bonds using 2.0

to 2.4 percent sodium hydroxide in oil-in-water emulsion.19 The chemical changes that

take place in the hair lead to a decrease in tensile strength by approximately 50% in the

wet state.20 Hair damage during relaxing is not restricted to disulfide bond breakage alone.

The alkaline hair relaxer leads to an increase in hair swelling intensified by concurrent

Figure 8. Hydrogenated starch hydrolysate.


Figure 9. Cross section of hair fiber.

breakdown of disulfide bonds.21 Rinsing with water produces additional swelling due to

osmotic forces, because there is a lower salt concentration outside the fibers at this stage

of a chemical process.22 It has been the objective of our study to utilize water-soluble

polymers to prevent or repair damage in relaxed hair by increasing the tensile strength and

reducing swelling during relaxing.

4. EXPERIMENTAL AND RESULTS

4.1. Increasing the Strength of Relaxed Hair with a Cationic Polymer

The tensile strength loss of hair fibers treated with a hair straightening formula con-

taining a cationic polyamine, such as the polyamine shown in Figure 7, versus a control


Figure 10. Cuticles of the hair.

Figure 11. Cortex of the hair.


relaxer without polymer was tested. Twelve inch long, dark brown European hair was ob-

tained from DeMeo Brothers, New York. The hair fibers were washed with a 10% solution

of ammonium lauryl sulfate, rinsed thoroughly, and allowed to dry overnight. Fibers of

close diameter (71–80 microns) were selected for this study. Each fiber was cut in half and

crimped into 30 mm sections using a Dia-Stron Crimp Press. The hair section closest to

the root was designated as the control, and the section downstream was used for the ex-

perimental relaxer. The tensile strength of the untreated hair fibers under wet conditions

was measured utilizing a Dia-Stron Miniature Tensile Tester, Dia-Stron, Ltd., U.K. The

strength was determined by the amount of work required to extend the fibers 20% of their

original length at a rate of 10.0 mm/min. The hair fibers were then allowed to restore over-

night in water. The following day, the fibers were dried at 65% relative humidity and 21°C

prior to treating with relaxers.

The control group was treated with hair relaxer without polymer, and the experimen-

tal group was treated with relaxer containing a cationic polyamine. Both sets were proc-

essed identically for 18 minutes, followed by rinsing, and then shampooing with a mild,

acidic shampoo. The following day, the tensile strength of treated fibers was determined

same as above using Dia-Stron MTT. The F20 index loss was then calculated.

Table 6 shows that hair treated with Control Relaxer without Polymers exhibited an

F20 index loss of 50.94%, whereas, hair treated with Relaxer containing cationic

Polyamine exhibited an F20 index loss of 45.11 %.-a statistically significant difference.

Table 7 shows a prototype formulation of a hair relaxer containing cationic strength-

ening ingredients.

4.2. Minimizing Swelling during Hair Relaxing

In addition to strengthening the hair while relaxing by forming a complex in the

hair, we have discovered that water-soluble polymers, especially non-ionic polymers such

as starch hydrolysates, reduce the swelling of the hair during relaxing. During the process

of relaxing, the hair swells up to 50% or more of its original diameter. Upon rinsing with

water, the hair suddenly swells another 20 to 30% because of a sudden surge of osmotic

pressure inside the hair fibers. Much of the damage from swelling occurs during rinsing

because the swelling is very rapid. The hair fibers develop radial and longitudinal cracks

when swelling is not controlled. Figure 12 shows radial cracks and Figure 13 shows longi-

tudinal cracks in hair fibers caused by swelling in an alkaline solution.

The swelling studies were performed using a LaserMike laser micrometer which

measures the major and minor axis of the fiber simultaneously. LaserMike laser microme-

ter was purchased from LaserMike in Dayton, Ohio. European hair, available from DeMeo

Brothers, with a uniform diameter of 71–80 microns was selected for this study. The origi-

nal diameter of dry hair was measured under controlled conditions of 65% relative humid-

ity and 21°C. Fibers were then immersed in relaxer for 18 minutes. After 18 minutes,

excess relaxer was gently removed and the diameter again measured. The diameter meas-

urements were continued through the rinsing phase. Figure 14 shows a graph comparing

hair fiber swelling in relaxer without polymer versus with non-ionic polymer starch hydro-

lysate. Hair fibers treated with the control relaxer exhibited swelling of 45.21% at 18 min-

utes in relaxer, and peaked at 80.82% when rinsed with water.

Hair fibers using cream relaxer with polymer swelled to 19.78% before rinsing, and

38.46% upon rinsing. Therefore, hair fibers treated with relaxer containing non-ionic poly-

mer exhibit significantly less swelling compared to relaxers without polymers.

An example of a relaxer with deswelling ingredients is shown in Table 8.


Table 6. Effect of cationic polymers in hair relaxer

Control fibers treated with relaxer without Experimental fibers treated with relaxer

Hair fiber # Initial work* Work* after F20 loss % Hair fiber # Initial work* Work* after F20 loss %

I 1.15 0.54 53.04 1 1.04 0.51 50.67

2 1.39 0.69 50.58 2 1.64 0.95 42.07

3 1.50 0.71 52.40 3 1.44 0.82 43.13

4 1.47 0.66 54.97 4 1.19 0.67 43.87

5 1.47 0.79 46.12 5 1.43 0.84 41.12

6 1.37 0.61 55.69 6 1.29 0.64 50.70

9 1.27 0.60 53.15 9 1.27 0.71 44.41

10 1.40 0.77 45.00 10 1.25 0.76 39.44

11 0.94 0.43 53.99 11 0.82 0.43 47.43

12 1.18 0.46 60.93 12 1.11 0.56 49.37

13 1.09 0.52 52.39 13 1.01 0.59 41.68

14 I .43 0.69 51.47 14 1.37 0.77 44.01

15 1.17 0.61 47.61 15 1.07 0.68 36.92

16 1.30 0.73 43.62 16 1.16 0.65 44.3 1

17 0.92 0.41 55.05 17 0.96 0.45 52.51

18 0.99 0.50 49.50 18 0.99 0.62 38.00

19 1.29 0.68 47.52 19 1.21 0.66 45.54

20 1.22 0.63 48.20 20 1.24 0.69 44.52

22 1.17 0.61 48.29 22 1.10 0.62 43.91

23 1.41 0.73 48.58 23 1.09 0.5 1 52.94

25 1.12 0.54 51.61 25 1.05 0.52 50.76

Average 50.94 45.1 1

Standard deviation 4.10 4.64

Coeff. of variance 8.05 10.28

polymer containing polyamine

*Work done is in millijoules

When used in combinations, relaxers containing combinations of deswelling and

strengthening polymers leave the hair visibly and measurably healthier. Table 9 shows ten-

sile strength results of hair treated with relaxer containing polymers versus a control re-

laxer without polymer. Figure 15 shows a scanning electron micrograph of a hair fiber

treated with relaxer containing strengthening and deswelling polymers (reproduced with

permission from Avlon Industries). The cuticles lay flat, and there are no visible cracks in

the structure.

Table 7. Hair relaxer formulation containing cationic strengthening polymers


Petrolatum and/or mineral oil 30.0 to 35.0

Fatty alcohols and/or emulsifying wax 6.0 to 10.0

Emulsifiers 2.5 to 4.0

Simethicone 0.1

Lanolin 0.5

Deionized water 46.4 to 56.9


Cationic polyamine (50%) 2.0

Sodium hydroxide 2.2


Figure 12. Radial cracks in hair fiber. (Reproduced with permission from Avlon Industries. All rights reserved.)

Figure 13. Longitudinal cracks in hair fiber. (Reproduced with permission from Avlon Industries. All rights re-

served.)


Figure 14. Hair swelling by relaxer with nonionic polymer.

5. CONCLUSIONS

A series of cationic polyamines and starch hydrolysates, when used at certain levels

separately and in combinations, control the swelling and enhance the strength of relaxed

hair. The theory is that during the relaxing process, hair is swollen to a maximum degree

and the cuticle layers are widely open at this stage. The cationic polyamines are able to

penetrate into the cortex. Upon rinsing the hair with water, as the hair deswells, the cat-

ionic polyamines are trapped in the cortex of the hair, as well as ionically bonded to the

negative sites on the surface of the hair. Since cationic polyamines are very elastic, they

improve the elasticity and tensile strength of the relaxed hair fibers. While cationic

polyamines are penetrating inside the hair, the polymeric starch hydrolysates present in

high concentration around and outside the hair fiber are able to reduce the osmotic pres-

sure inside the hair, thereby reducing the swelling of hair fibers significantly. This reduc-

tion in swelling helps to prevent longitudinal and radial cracks in the hair fibers. The

combination of deswelling and strengthening polymers results in healthier relaxed hair.

Table 8. Relaxer formulation with polymeric deswelling agent


Petrolatum and/or mineral oil 30.0 to 35.0

Fatty alcohols and/or emulsifying wax 6.0 to 10.0

Emulsifiers 2.5 to 4.0

Simethicone 0.1

Lanolin 0.5

Deionized water 46.4 to 56.9


Hydrogenated starch hydrolysate 2.0

Sodium hydroxide 2.2


Table 9. Tensile strength of hair treated with relaxers containing polymers

Experimental no-base relaxer with polyamine

and starch hydrolysate Control no-base relaxer without polymers

Hair Initial work* Work* after %F20 loss Hair Initial work* Work* after %F20 loss

2 1.24 0.65 47.82 2 1.24 0.66 46.45

5 1.16 0.61 47.59 5 1.18 0.68 42.80

6 1.33 0.70 47.22 6 1.24 0.69 44.19

7 0.87 0.37 58.05 7 0.77 0.41 46.36

8 1.10 0.60 45.82 8 0.99 0.6 1 38.38

9 0.80 0.41 48.25 9 0.81 0.49 39.83

12 1.27 0.73 42.91 12 1.23 0.83 32.85

15 1.36 0.68 49.85 15 1.40 0.81 42.43

16 1.33 0.64 51.58 16 1.39 0.80 42.45

20 1 .08 0.54 50.37 20 1.13 0.68 40.00

21 0.98 0.57 41.78 21 0.97 0.55 43.45

22 1.03 0.46 55.34 22 0.98 0.64 34.55

23 1.29 0.58 55.43 23 1.16 0.69 40.52

25 1.07 0.44 59.07 25 0.93 0.47 49.84

Average 50.08 41.72

Standard deviation 5.29 4.56

Coeff. of variance 10.57 10.93

*Work done is in millijoules

Figure 15. Hair fiber treated with relaxer containing deswelling and stregthening polymers.


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9. Zviak C. The Science of Hair Care Marcel Dekker, Inc., New York, 1986.

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Documents

Water Soluble Polymers in Hair Care