Split ends are a concern for many consumers. The hair care market abounds with products that claim to address hair damage. According to Mintel, nearly 950 products have been launched within the past three years, comprising 25% of all new hair care launches in the United States. Upon further analysis, one will find that the vast majority of these products have technology and claims aimed at preventing damage, not repairing it, which leaves many consumers disappointed with the performance of their current products designed to solve a highly important consumer need.
In 2011, Alberto-Culver Co., now a part of the Unilever Group, launched a split end repairing linea to its Nexxus Salon Hair Care brand that is believed to be the first line of products fully dedicated to split end repair. This article reviews new discoveries around the formation of split ends, compositions designed to repair them and advanced microscopy techniques for claims communication as discovered by the R&D team behind the line.
Split End Formation
The technical term for split ends is trichoptilosis, which occurs when weakened ends split apart creating a “y” shape. This particular type of hair damage predominantly occurs on the ends for two reasons—the ends are the oldest and thus the weakest; and combing forces are at their highest.
Since hair grows from root to tip, the ends are the oldest and have experienced the most damage. Hair grows at an average rate of 0.5 inches per month, so hair that is only 6-inches long has already experienced one year of damage. Some hair fibers are naturally prone to splitting, even if consumers take good care of their hair. Other hair fibers can become weaker over time through chemical processing, heat styling and combing—making them more prone to splitting. The actual instant that a split occurs happens when the surface of the comb rubs against the surface of a weakened hair fiber. This shear force is at its highest at the ends because hair tends to orient itself perpendicularly to the comb, forcing the consumer to pull harder. This induces hair fibers to fracture at a weak point within the protein subassemblies in the cortex, by a mechanism proposed by Swift.1 There are a number of publications in the industry that can be referenced for more information on hair breakage and split ends.2–8
A Theoretical Life Cycle of Split Ends
To understand split ends, samples must be collected. While collecting samples from friends and co-workers is plausible, the research team in this paper decided that creating them in the laboratory was more practical and beneficial. This allowed for substrate consistency across numerous studies and the high volume of samples that were needed.
In order to create the split ends, the research team started with twice bleached platinum blonde hairb. The hair samples were combed 3,000 times (1,500 strokes/side) with a robotic arm while a blow dryer was pointed at the ends. During sample collection, the research team was surprised to find a high amount of morphological diversity. Figure 1 displays this diversity, and further categorizes split ends into 10 different sub-types including: baby, primary, deep, incomplete, double Y, triple, tree, feather, long and taper. Images were taken with a light microscopec with a 100W halogen lamp using reflected light and brightfield contrast method, an objective lens for a total of 50X magnificationd, and a 1.5 megapixel camerae.
Based on these split end sub-types, it can further be theorized that split ends can evolve to exhibit more than one of these morphological sub-types. Figure 2 proposes such a life cycle. The life cycle starts with a healthy end. A split end starts off small, creating a baby split end. As more damage accumulates, the baby split end travels further up the hair shaft, creating the primary split end. This is the “classic” example of a split end and most likely the predominant type that consumers notice.
Deep split ends have the same life cycle as baby and primary split ends to this point, the difference being that it has occurred further up the hair shaft. Most split ends occur at the ends since they are the oldest and weakest part of the hair, but there can be weak points along the mid shaft as well. Hair ties and ponytails could contribute to this type of split end. Incomplete split ends are similar to the primary split and deep split. In this case, the weak point was not directly on the end of the hair. It can be seen that the split has not traveled to the end, which is why it is termed “incomplete.” Consumers describe these as “white dots,” and they typically can be seen about 1 inch away from the end. With a slight tug, the fiber will break at the white dot. If this occurs, the consumer will likely be left with a baby split, and the life cycle of a split end can start again from the beginning.
Double Y is an example of a primary split end that has become more damaged. Specifically, a split end has occurred on one side of the primary split. Another term for this is a “secondary” split. A “tertiary” split is also possible and can be seen as a tree split. Most likely the tree split started as a double Y and as more damage accumulated, the fiber started to further bifurcate like branches on a tree.
A triple split end is similar to the double Y. It is theorized that the double Y took more time to form, whereas the triple split probably occurred within the same time frame together (multiple weak spots that split together). The feather split end is similar to the triple split but with more damage. Similarly, it is hypothesized that this damage occurred on a faster time frame than the tree split.
After split ends have formed, they are susceptible to breakage. In this case, one side of the split has most likely broken off, creating one side that is longer than the other and forming the long split end. A taper split end is another example of further breakage after a small amount of fiber is left at the end. After all remnants of fiber at the site of the split have broken off, the end of the life cycle can be considered complete. However, the life cycle can perpetually begin again and agin since the fiber is significantly weakened.
A Differentiated Technical Approach
Many conditioners and treatments on the market claim to repair damaged hair. However, most of these products borrow from the technological approach of most standard moisturizing conditioners. That is, using positively charged quaternium compounds to stick to and smooth surface cuticles in addition to silicones to give a lubricious effect. While this approach may give a smooth appearance and sensory feel, it is unable to give a meaningful amount of true split end repair.
In contrast, compositions containing a polyelectrolyte complex (PEC) comprised of PVM/MA copolymerf and polyquaternium-28g have been shown extensively to bind split ends.9, 10 Figure 3 shows a visual representation of such a complex. These PECs are formed by ionically combining the anion PVM/MA Copolymer and the cation Polyquaternium-28. This new species therefore has both positive and negative charges, which gives it the ability to attach to negatively charged damaged hair and each other.
Figure 4 shows a theoretical mechanism of the PEC technology binding split ends. When the PECs flow into the site of a split end during application, they stick to the hair fiber because they are positively charged (like ordinary conditioners). However, because they also have negative charge, they can stick to themselves and form a network within the split end. As the PECs dry, they contract, binding the split end from within.
Formulating with these PECs can be counterintuitive to most formulators, which is why they are not frequently found in the cosmetics market. Most cosmetic chemists are taught to never add two ingredients with opposite charges on top of each other, as that will typically ruin the batch. Additionally, overcoming the change in hair feel when adding a high amount of styling polymers to a conditioning formulation can be a challenge. Moreover, the high amount of electrolytes will alter typical emulsion structure, forcing the formulator to find new solutions for attaining acceptable initial viscosities, freeze/thaw stability and long-term viscosity control. Finally, offering a rinse-out application of the technology is crucial for a sustainable innovation because of the format’s high consumer penetration in market.
However, these challenges prove valuable when it gives the ability to enter the crowded hair care market with differentiated claims. Since most conditioning compositions can only prevent split ends, an opportunity was presented to show the consumer a breakthrough in hair damage repair. The researchers applied a drop of 2% PEC solution on a split end that was mounted on a glass slide and placed under 50X magnification. A video was then recorded (see Video 1) using high speed recorder softwareh as a blow-dryer was aimed at the sample. As the mechanism in Figure 4suggests, when the polymer film dried, it contracted, binding the split end back together.
Additionally, one can also show the consumer the end of the split end life cycle. Figure 5 shows before-and-after pictures of the 10 categories of split ends when treated with compositions containing the PEC. It is important to note that one cannot ever fully prevent the occurrence of split ends and their evolution of further damage. However, with conditioning compositions that can repair split ends, no matter what the type, the consumer promise of true damage repair can finally be realized.
The research team behind the split end repair linea believes that it has changed the hair care market by approaching split ends with a novel approach. Through extensive research, the product development team has brought new insight into the formation of split ends, advanced the formulation design of compositions and showcased the technological benefit with new techniques in microscopy. This success has paved the way for even more products to be launched by the brand in 2012.
The authors would like to thank Sam Byerly from Carl Zeiss MicroImaging LLC, and UIC Medical School for their help in this research.
Send e-mail to [email protected].
1. JA Swift, Mechanism of split end formation in human head hair, J Soc Cosmet Chem, 48 123–126 (March/April 1997)
2. The mechanics of fracture of human hair, J. A. Swift, Intl J Cosmet Sci 21, 227–239 (1999)
3. HM Haake, S Marten, W Seipel and W Eisfeld, Hair breakage–How to measure and counteract, J Cosmet Sci 60 143–151 (March/April 2009)
4. GH Henderson, GM Karg and JJ O’Neill, Fractography of human hair, J Soc Cosmet Chem 29 449–467 (August 1978)
5. AC Brown and JA Swift, Hair breakage: the scanning electron microscope as a diagnostic tool, J Soc Cosmet Chem 26 289–297 (1975)
6. RD Sinclair, Healthy Hair: What is it?, J Invest Dermatol Symposium Proceedings, 12(2–5) (2007)
7. CG Burkhart, JJ Hunter and J Bruner, Central trichoptilosis, J Am Acad Dermatol 5(6) 703–705 (Dec 1981)
8. M Arai, K Morita, K Yahagi and S Naito, Studies on the split end formation of hair by brushing, J Soc Cosmet Chem Japan 29(2) 125 (1995)
9. R Rigoletto, Y Zhou and L Foltis, Semi-permanent split end mending with a polyelectrolyte complex, J Cosmet Sci 58 451–476 (July/August 2007)
10. R Rigoletto and Y Zhou, Polyelectrolyte Complex for Mending Damaged Hair, Cosm & Toil 124(3) (2009)