News Release
September 13, 2024
Original Japanese Publication Date︓July 2, 2024

Milbon Finds Curly Hair Has Weak Cuticle Adhesion andLow Hair Strength-Microscopic Observation of Hair Structure for Hair Types Around the Worldby Inborn Curl Shape-Milbon Co., Ltd. (head office: Chuo-ku, Tokyo; President and CEO: Hidenori Sakashita), a
manufacturer of salon-exclusive haircare products and cosmetics, observed at the microscopic
level the hair microstructure of different hair types around the world, classified according to theirinborn curl shape. As a result, we found that curly hair has weaker cuticle adhesion and lower hairstrength than straight hair. We also confirmed that the amount of glycoprotein*1, which is believed
to contribute to cuticle adhesion, was low. The results of this study were presented at the following
academic conference.
[Presentation]
Academic conference: 21st IUPAB Congress
Title of presentation: Differences in microstructural changes during tensile deformation between
hair shapes
Date of presentation: June 27, 2024
[Research Background]
There are many different hair shapes in the world, including straight and strongly curled hair.
Hair types can be classified according to their inborn curl shape and are referred to as straight hair,wavy hair, curly hair, and coily hair, in order from weakly curled to strongly curled hair (Figure 1).
Straight and wavy hair is common in Japan and other Asian regions, while many people in North
America and Africa have curly and coily hair. It is known empirically that these strongly curled hairs
are more susceptible to physical stresses such as tangling and pulling due to their shape, and are
more prone to damage phenomena such as hair breakage and split ends.
In this study, we investigated the differences in hair microstructure between straight and curly
hair in order to grasp the causes of damage in curly hair, with the aim of establishing effective
damage care methods for a wider range of hair types around the world.

- 1 -Figure 1. Hair types[Study Findings]
1. Curly hair found to have weak cuticle adhesion and low resistance to physical stress
We investigated the resistance of curly hair to stretching, noting that curly hair is susceptible tophysical stresses such as tangling and pulling. The investigation revealed that curly hair is lessresistant than straight hair (Figure 2). To determine what features of the hair microstructure areresponsible for this low resistance, we observed both the surface and interior of stretched hairusing laser scanning microscopy*2 and X-ray CT measurements*3 at SPring-8*4. This revealed that
curly hair tends to have gaps between cuticles on the outermost surface and between the cuticle
and the hair interior as it is stretched (Figure 3). This indicates that cuticle adhesion is weaker incurly hair than in straight hair, leading to the low resistance to stretching.

Figure 2. Resistance to stretching
Curly hair was less resistant than straight hairin the resistance evaluation based on the force

Figure 3. Microstructure of stretched hair (upperrequired to stretch the hair lengthwise.

row: hair surface, lower row: hair interior)
Red marks indicate areas of cuticle lifting.

- 2 -2. Curly hair found to have less glycoprotein that contributes to cuticle adhesion
A structure called cell membrane complex (CMC) exists between cuticles and between thecuticle and the hair interior, and glycoprotein contained in CMC is thought to contribute to theadhesion of cuticles and other structures (Figure 4). We measured the amount of glycoprotein inhair and found that curly hair contains less glycoprotein than straight hair (Figure 5).

Figure 4. Image of adhesion between hair

Figure 5. Difference in glycoprotein content

microstructures

between hair types[Future vision]
We will use this study toward the development of hair care products that effectively repair curlyand coily hair that is prone to damage and allow people to continue to enjoy their ideal hair in theirown way. Milbon will continue to research various hair types and beauty behaviors around theworld to develop products for the global market.

≪Terminology≫*1 Glycoprotein
Proteins with glycans attached to some amino acid residues.
*2 Laser scanning microscopy
Technology that can capture the surface structure of an object in a non-destructive manner.
Microscopic observation using a single-wavelength laser beam and confocal optics enables detailed
three-dimensional observation of an object's surface profile.
*3 X-ray CT measurement
Technology that can capture the internal state of an object in a non-destructive manner. In thisstudy, X-ray CT measurement using the world's most powerful synchrotron radiation at the- 3 -BL24XU beamline of SPring-8 have enabled us to precisely capture the internal microstructure ofhairs. Part of this study was conducted as part of the General Proposal for Industrial Applications
2023B3264 at the Japan Synchrotron Radiation Research Institute (JASRI).
Milbon has captured the internal microstructure of hair with this measurement technique in thepast.
*4 SPring-8SPring-8 is a large synchrotron radiation facility which delivers the most powerful synchrotron
radiation currently available. Consisting of narrow, powerful beams of electromagnetic radiation,synchrotron radiation is produced when electron beams, accelerated to nearly the speed of light,
are forced to travel in a curved path by a magnetic field. The research conducted at SPring-8,located in Harima Science Park City, Hyogo Prefecture, Japan, includes nanotechnology,biotechnology and industrial applications. The name "SPring-8" is derived from "Super Photon
ring-8 GeV" (8 GeV, or 8 giga electron volts, being the energy of electron beam circulating in thestorage ring).
Reference: SPring-8 website（http://www.spring8.or.jp/en/about_us/whats_sp8/）■For inquiries relating to this news release:
Public Relations, Kyobashi Edogrand, 2-2-1 Kyobashi, Chuo-ku, Tokyo, Japan

Phone: +81-3-3517-3915- 4 -Fax: +81-3-3273-3211