Method for evaluating hair fibers

Abstract

Hair fiber evaluation method: A hair fiber evaluation method comprising: a) Performing a first measurement of a first value representative of the mechanical resistance of the hair fibers, b) Performing a second measurement of a second value representative of the combability of the hair fibers, c) Generating a score representative of the risk of breakage of the hair fibers during combing, based at least on said first and second measurements. Figure for the abbreviation: Figure 1

Description

Title of the invention: Method for evaluating hair fibers

[0001] The present invention relates to a method for evaluating hair fibers and comparing the effects of compositions on hair fibers. CONTEXT

[0002] Textured hair, particularly very curly and twisted hair such as the natural or non-chemically modified hair of people of African descent, is prone to breakage due to its morphological and physiological properties. These properties include low scalp sebum levels, poor sebum distribution due to a high degree of fiber curvature, hair shafts with fewer cuticle scales, and a longer interscale distance between cuticle cells.

[0003] Chemical treatments such as straightening or perming and physical treatments such as brushing and braiding are often considered to damage hair fibers.

[0004] However, the maintenance regimens of women with natural African hair have also been shown to damage the hair fibers, with daily combing causing significant damage and surface breakage, leading to a 'steady state' length where the hair grows but noticeable growth is not achieved due to breakage. Frequent braiding also causes significant surface and mechanical damage to the hair.

[0005] Currently, the assessment of the integrity of African hair is based on processes developed for Caucasian or Asian hair.

[0006] In particular, the integrity of the hair is assessed through the chemical damage done to the hair and this damage is assessed by measuring the strength of the fibers. Such a method is useful for assessing the impact of bleaching or perming on Caucasian hair. However, it is not sufficient to fully assess the risk of breakage on African hair.

[0007] It is desirable to have available a method of evaluating hair which avoids all or part of the above-mentioned disadvantage and which represents well what happens in the real life of consumers, in particular when it comes to African hair of the textured hair type. Summary of the invention

[0008] Exemplary embodiments of the invention aim to satisfy this need and relate to a method of evaluating hair fibers, comprising:

[0009] a) Carrying out a first measurement of a first value representative of a mechanical resistance of hair fibers,

[0010] b) Carrying out a second measurement of a second value representative of the combing ability of the hair fibers,

[0011] c) Generating a score representative of a risk of breakage of hair fibers during combing based at least on said first and second measurements.

[0012] The term "textured hair" refers to wavy hair, curly hair, very curly hair such as kinky hair, or kinky hair.

[0013] The term "chemical modification" refers to a modification caused by a hair treatment such as bleaching / lightening, straightening, permanent coloring and / or permanent waving.

[0014] The term "physical modification" means a modification caused by a physical process such as brushing, straightening, braiding and general manipulation of the hair.

[0015] The term "hair fiber strength" reflects how easy or difficult it is to break a hair fiber. It is based on the force required to break the fiber.

[0016] The term "combability" is defined as the perception of how easy or difficult it is to comb the hair. It is directly related to the maximum combing force which is opposite to the action of combing the hair. A lower force relative to the movement of the comb through the hair means that it is easier to comb the hair.

[0017] In steps a) and b), the hair fibers subjected to these steps are preferably textured hair fibers, such as African hair fibers. The hair fibers may be identical or different but belong to the same hair or to a plurality of hairs belonging to the same category, for example the category of African hair. The hair fibers may belong to certain locks of hair, preferably taken from the same person or from different people having the same type of hair. Although it is preferable to carry out the measurements on locks of hair that have been detached from the head, it is also possible to carry out the measurement to assess the integrity of the hair at a point of sale or in a hair salon using certain suitable measuring devices.

[0018] The method according to the invention is better suited to characterizing the breakage of hair fibers, in particular textured hair fibers such as African hair.

[0019] For example, a relaxer treatment on naturally textured hair can chemically damage the hair, but consumers' hair doesn't break as much in real life. This is because a relaxer makes it much easier to comb through textured hair fibers by making the hair fibers straight.

[0020] The introduction of combability allows to take into account the damage that combing can cause to hair fibers. In fact, for textured hair, especially for very curly or kinky hair, such as African hair, the chance of having knots is high. Therefore, the hair fibers are more likely to break. Therefore, it is important to take this probability P2 into account when evaluating hair fibers, especially textured ones.

[0021] The score generated in step c) takes into account most of the factors that could lead to breakage of hair fibers. A lower score, especially relative to a threshold, indicates a lower risk of breakage during combing. In general, the higher the score, the higher and more significant the risk of breakage.

[0022] Preferably, the method consists in determining a first quantity PI representative of a probability (or likelihood) of breakage of the hair fibers due to one or more chemical and / or physical modifications of the hair fibers, based at least on said first value and a second quantity P2 representative of a probability of having a strong fiber elongation during the combing of the hair fibers, based at least on the second value.

[0023] The probability of having a high fiber elongation characterizes the ability of the hairs to expand. For textured hair fibers, especially for very curly hair and kinky hair, especially for African hair fibers, this probability is higher than for straight hair fibers such as Caucasian or Asian hair fibers. The more curly the fiber, the more it is subject to elongation.

[0024] Preferably, the method comprises outputting said score of step c) as a probability PB of hair fiber breakage, based on the first and second quantities. This probability PB may correspond to the product of PI and P2: PB=P1*P2. Step a)

[0025] In step a), the first measurement may assess the tensile strength value(s). The first value may correspond to the tensile strength value.

[0026] In some embodiments, step a) comprises measuring the tensile strength of the hair fibers. The measurement may be performed using a static uniaxial tensile test. A suitable testing machine for measuring tensile strength is, for example, the miniature tensile testing machine (MTT) provided by Diastron.

[0027] In some embodiments, the mechanical strength of the hair fibers is characterized by a fatigue test. In such embodiments, step a) advantageously comprises measuring the fatigue fracture. This measurement may be carried out by performing a cyclic fatigue tensile test on the hair fibers.

[0028] Cyclic fatigue testing subjects the capillary fibers to repeated loading conditions as opposed to a single load, as is the case with static uniaxial tensile testing. Cyclic fatigue testing provides information on the evolution of the fibers over repeated loading cycles. During fatigue testing, the fibers may be subjected to constant strain, constant force, or constant stress, preferably constant stress.

[0029] Preferably, the cyclic fatigue test is carried out by: - submission of hair fibers to low amplitude elongation cycles, and - measurement of fiber lifespan, lifespan corresponding to the number of load cycles that a fiber can withstand before breaking.

[0030] Preferably, the first value corresponds to the lifespan of the hair fibers. Step b)

[0031] The combability of the fibers can be characterized by the value(s) of the combing force. The second value can correspond to the maximum combing of the hair fibers.

[0032] Therefore, step b) may comprise measuring the maximum combing force of the hair fibers, in particular with an extensometer.

[0033] Preferably, the measurement of the combing force is carried out by following a combing method similar to that described in (ML Garcia and J. Diaz, Combability measurements on human hair, J, Soc, Cosmet. Chem,, 27, 379 (1976)) in which the combing tool is modified. Instead of a multi-toothed comb, a tool with a single tooth is advantageously used. Such a tool with a single tooth makes it possible to accurately quantify fiber-to-fiber interactions.

[0034] The method may comprise treating the hair fibers before carrying out the measurements of steps a) and b).

[0035] The hair treatment may comprise the application of a cosmetic composition to said hair fibers.

[0036] The method may comprise generating information representative of the impact of said composition on hair breakage based on said score generated in step c).

[0037] Information representative of the score may be printed or displayed on an information medium, in particular a notice, packaging of a hair composition, an information or advertising panel, a commercial brochure, a television screen or a mobile phone screen.

[0038] The score can be compared to a threshold or to a score associated with another cosmetic composition.

[0039] Preferably, the first quantity PI is determined by comparing the first value measured for treated hair fibers to the first value measured for natural hair fibers.

[0040] The first quantity may depend on a ratio of the first value of the treated hair fibers to the first value of the natural hair fibers. For example, the first quantity corresponds to the rounding down or up of the ratio of the life of the treated hair fibers to the life of the natural hair fibers.

[0041] According to another aspect of the invention, a method for comparing the effects on hair breakage of at least two cosmetic treatments is provided, comprising:

[0042] - Carrying out a first treatment on hair fibers,

[0043] - The generation of a score representative of a risk of breakage of hair fibers by implementing the method according to the invention,

[0044] - Carrying out a second treatment on the hair fibers,

[0045] - The generation of a score representative of a risk of breakage of hair fibers by implementing the method according to the invention,

[0046] - Comparison of scores.

[0047] Preferably, the first and second treatments comprise the application to the hair fibers of the respective first and second compositions.

[0048] The composition may be a relaxer or a straightener.

[0049] The second quantity P2 can be determined by taking as reference hair treated with a given composition (for example, the composition having the greatest effect on straightening the hair).

[0050] Other embodiments of the invention relate to a method of manufacturing a hair composition, wherein several candidate compositions are proposed, the candidates are compared by applying the above comparison method, the best candidate is selected based at least on the result of the comparison and the selected candidate is mass produced.

[0051] The manufacturing method may comprise comparing the scores of the candidate composition and selecting the candidate having the lowest score. Advantageously, the manufacturing method makes it possible to select the candidate which causes the least breakage of hair fibers. Brief description of the drawings

[0052] The accompanying drawings, which are incorporated in and form a part of the specification, illustrate presently preferred embodiments of the invention, and together with the description, serve to explain the principles of the invention. In the drawings:

[0053] [Fig.l] [Fig.l] is a diagram of an embodiment of a method according to the invention,

[0054] [Fig.2] [Fig.2] is an example of a combing tool,

[0055] [Fig.3] [Fig.3] shows images of hair fibers after application of different compositions and control hair fibers, on the left side: hair fibers treated with a relaxer, in the middle; hair fibers treated with 2.5% cysteine ​​and on the right side: natural hair fibers,

[0056] [Fig.4] [Fig.4] is a graph showing the probability of breakage due to one or more chemical and / or physical modification(s) of the hair fibers of [Fig.3],

[0057] [Fig.5] [Fig.5] is a graph comparing the maximum combing force for hair fibers of [Fig.3], and

[0058] [Fig.6] [Fig.6] is a graph comparing the mass of hair fibers broken during styling to the hair fibers in [Fig.3].

[0059] In accordance with the invention, and as generally implemented, a method according to the present invention is provided, aimed at evaluating hair fibers.

[0060] First, in step 101, a first measurement of a first value representative of a mechanical resistance of the hair fibers is carried out. In this embodiment, the first value relates to fatigue fracture.

[0061] Step 101 comprises subjecting the hair fibers to a cyclic fatigue tensile test. In particular, step 101 comprises: - Subjecting hair fibers to repeated low-amplitude elongation cycles, and - The measurement of the life of the fibers, the life corresponding to the number of elongation cycles that the fiber has resisted without breaking.

[0062] In step 103, the first measured value characterizing the resistance of the hair fibers is provided for processing.

[0063] Based on this measurement, a first quantity PI representative of a probability of breakage due to one or more chemical and / or physical modifications of the hair fibers is calculated in step 105. The shorter the lifetime, the higher the probability of breakage.

[0064] In step 107, a second measurement of a second value representative of the combability of the hair fibers is carried out. This measurement corresponds to the maximum combing force, that is to say to the force which is opposed to the action of combing the hair fibers. The weaker the force, the easier it is to comb the hair fibers.

[0065] In the illustrated embodiment, the combing force is measured using a Llyod extensometer. The combing method used corresponds to that described in (ML Garcia and J. Diaz, Combability measurements on human hair, J, Soc, Cosmet. Chem, 27, 379 (1976)). Unlike the aforementioned article, a different combing tool is used. Instead of a comb with several teeth, a tool 10 with a single tooth 15 is used. The combing tool is shown in [Fig.3].

[0066] In step 109, the combing force of the hair fibers is provided for processing.

[0067] Depending on the combing force, a second quantity of P2 representative of a probability of having a high fiber elongation is calculated in step 111. The greater the combing force, the higher the probability.

[0068] A very high probability may be indicative of a high risk of knots in the hair fibers and therefore breakage during combing.

[0069] In step 113, a score representative of a risk of breakage of the hair fibers during combing is calculated on the basis of at least said first and second measurements.

[0070] In this embodiment, said score is delivered as a probability PB of breakage when combing the hair fibers and is calculated by multiplying PI and P2: PB = PlxP2

[0071] The method described above may be useful for evaluating the impact of hair composition on hair fibers.

[0072] To this end, the method comprises, before step 101, a step 100 in which the hairs are treated by applying a cosmetic composition to these hairs. Essay

[0073] Subsequently, a comparative test will be described. Two hair compositions, composition 1 and composition 2, are evaluated.

[0074] [Table 1]

[0075] Table 1 describes composition 1 which corresponds to a hair straightening product. Ingredient % WATER 51.495 MINERAL OIL 22 CETEARYL ALCOHOL (and) POLYSORBATE 60 10.5 PETROLATUM 10 SODIUM HYDROXIDE 2,2 PROPYLENE GLYCOL 2 LANOLIN PEG-75 0.65 COCAMIDOPROPYL BETAINE 0.53 CETYL ALCOHOL 0.5 PERFUME 0.125

[0076] [Table 2]

[0077] Table 2 describes a composition of cysteine. Ingredient % WATER 76.80800000 CETEARYL ALCOHOL 6.30000000 CETEARYL ALCOHOL (and) CETETH-10 PHOSPHATE 4.50000000 MINERAL OIL 2.70000000 PPG-5-CETETH-20 2.70000000 POLYQUATERNIUM-6 2.50000000 CYSTEINE 2.50000000 ETHANOLAMINE 1.40000000 FRAGRANCE 0.50000000 EDTA 0.09200000

[0078] Routine (step 100)

[0079] - For composition 1:

[0080] 1. Application of the composition (4 g of composition per gram of fibers ca pillars)

[0081] 2. Exposure time: 22 minutes

[0082] 3. Rinsing

[0083] 4. Shampoo twice (0.4 g of shampoo per gram of hair fibers)

[0084] - For composition 2:

[0085] 1. Hair shampoo (0.4 g of shampoo per gram of hair)

[0086] 2. Application of the composition to damp hair (4 g of composition per gram of hair)

[0087] 3. Exposure time: 15 minutes

[0088] 4. Rinsing

[0089] [Fig.3] shows the appearance of the fibers after applying the compositions to the textured hair fibers. The left image corresponds to hair treated with composition 1; the center image corresponds to hair fibers treated with composition 2; while the right image corresponds to natural (untreated) hair fibers, which corresponds to textured hair (African hair) in this example. The natural hair fibers are used as a control. As we As you can see, treatment with composition 1 makes textured hair straighter. Composition 2 slightly opens the curls of the hair fibers, but less than composition 1.

[0090] The method for evaluating hair fibers according to the invention is then carried out to evaluate the hair fibers in each of the three cases above.

[0091] The cyclic fatigue tests (step 101) were carried out at a constant stress of 144 MPa, using a Diastron CYC 901 cyclic fatigue testing machine. Cross-sectional area measurements are carried out using a fiber dimensional analysis system (FDAS, Diastron) and are used to arrive at the correct target stress.

[0092] A comparison regarding the number of cycles before breakage for hair fibers treated with composition 1, hair fibers treated with composition 2 and the control corresponding to natural hair fibers without any treatment is illustrated in [Fig.4]. As shown, composition 1 corresponding to a relaxer is the most chemically damaging to the hair while composition 2 is less damaging. Therefore, the probability of breakage due to one or more chemical and / or physical modification(s) of the hair is higher for composition 1 than for composition 2.

[0093] To carry out the combing test (step 109) using the Lloyd extensometer, a strand (1 g) is inserted into the center of the comb and the strand is clamped onto the extensometer sensor. The strand is moved by the extensometer gantry in linear translation and the maximum combing force is measured. This movement is repeated four times and the average of the maximum combing forces is used to assess the effectiveness of the compositions under test.

[0094] A comparison of the combing force for hair fibers treated with composition 1, hairs treated with composition 2 and the control corresponding to natural hair fibers without any treatment is illustrated in [Fig.5].

[0095] The control sample (naturally textured hair) has the highest combing force, which translates into a high elongation capacity. With respect to the tested compositions, as illustrated, the combing force is considerably reduced by the use of the relaxer. Composition 2 reduces this force by slightly opening the curls, but not as much as Composition 1. In other words, hair fibers treated with Composition 2 can elongate more than those treated with Composition 1. The lower the combing force, the lower the risk of fiber elongation.

[0096] Based on the measured combing force, composition 1 therefore has a P2 lower than composition 2, which is itself lower than the control.

[0097] The PB= Plx P2 score is calculated for each of the three cases: treated hair fibers with composition 1, hair fibers treated with composition 2 and the control (natural hair fibers).

[0098] Table 3 summarizes the values ​​of PI, P2 and PB obtained for each of the three cases (composition 1, composition 2 and control) by implementing the evaluation method according to the invention.

[0099] Real-life breakage (in the last column) was measured by consumer evaluation, i.e., the consumer evaluated the breakage of their hair during combing.

[0100] “+” quantifies the PI and P2 values, a higher number of “+” means that the probability is higher; PB corresponds to the number of “+” of PI times the number of “+” for P2.

[0101] For PI, natural hair fibers are taken as reference, a single “+” is associated with the PI value for natural hair fibers.

[0102] The PI value for compositions 1 and 2 corresponds to the ratio of the cyclic fatigue value for the corresponding composition compared to natural hair fibers. For example, for natural hair, the median cycles to failure are 383, for composition 1, they are 89. So, 383 / 89 = 4.3. PI for composition 1 is therefore 4 "+" or "++++".

[0103] For P2, the hair fibers treated with composition 1 are taken as a reference with a single “+”. The value of P2 for composition 2 and for the control corresponds to the ratio between the value of the combing force in each case in comparison with the hair fibers treated with composition 1. For example, for composition 1, the combing force is 1.5 N, for composition 2, it is 5.4. Then, 5.4 / 1.5 = 3.6. P2 for composition 2 then corresponds to 4 “+” or “++++”.

[0104] [Tables3] Pi P2 Pb Real-life breakage during combing Control (natural hair) + ++++++ 6 Moderate Composition 1 (relaxed hair) ++++ + 4 Low Composition 2 (2.5% cysteine ​​treatment) ++ ++++ 8 High

[0105] An assessment based solely on the value of the probability of breakage due to a or several chemical and / or physical modifications of the hair PI would allow to conclude that the hair fibers treated with composition 1 would break more than the natural hair and than the hair fibers treated with composition 2. One could think that composition 1 would make the hair more fragile than composition 2. However, this assessment is contradicted by the experimentation and the evaluation by the consumer of these compositions, illustrated in the right column.

[0106] In fact, although the relaxer treatment (composition 1) on textured hair chemically damages the hair, consumers' hair does not break as much in real life as shown in the last column. This is because composition 1, i.e. the relaxer, greatly facilitates combing on textured hair by making the hair straighter, thus improving fiber alignment and reducing the risk of fiber tangling and / or knotting, as shown in the third column where the probability of having high fiber elongation is kept at a low value.

[0107] The calculation of the PB for both compositions 1 and 2 leads to the conclusion that composition 2 can cause significantly more hair breakage than composition 1, in agreement with the consumer evaluation.

[0108] For the control (textured hair), the chance of having knots on the hair is high. Therefore, the control breaks more than in the case of treatment with composition 1.

[0109] Therefore, PB provides information consistent with consumer appreciation. Knowledge of PB provides a valuable tool for comparing hair compositions and predicting the impact of hair compositions on hair fibers, especially textured hair fibers.

[0110] In addition to consumer evaluation, hair fiber breakage during combing was also assessed according to the steps below:

[0111] 1. The lock of hair (1 g) is first washed

[0112] 2. The hair is then dried with cold air

[0113] 3. 120 comb passes are made over the hair and the broken hair is collected

[0114] 4. Steps 1 to 3 are repeated 2 more times (3 in total)

[0115] 5. The total number of broken hair fibers is weighed.

[0116] [Fig.6] illustrates the mass of broken hair fibers for each case. As illustrated, the same results in terms of breakage are obtained as in real-life consumer feedback. The mass of broken hair fibers is lower for hair fibers treated with composition 1. The mass of broken hair is higher in the case of hair fibers treated with composition 2.

[0117] This experiment confirms the assessment carried out with the method according to the invention in which the PB value is higher for composition 2 than for composition 1.

[0118] It is understood that the general description and the detailed description above are both given by way of example and do not restrict the scope of the invention.

[0119] Steps a) and b) can be performed in any order, a) before b) or b) before a).

Claims

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2.

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5.

6. Claims A method of evaluating hair fibers, comprising a. Carrying out an initial measurement of a first representative value of the mechanical resistance of the hair fibers, then b. determining a first quantity PI representative of a probability of breakage of the hair fibers due to one or more chemical and / or physical modifications of the hair, based at least on said first value, then c) Carrying out a second measurement of a second value representative of the combing ability of the hair fibers, said measurement comprising the following steps: - insertion of a strand of hair fibers into the center of the combing tool (10) and clamping of the strand onto the sensor of an extensometer, then - linear transition displacement of the extensometer relative to the combing tool (10), then - measurement of the maximum combing force, then d) determining a second quantity P2 representative of a probability of having a strong fiber elongation during hair combing, based at least on the second value, then e) The generation of a probability PB of hair fiber breakage, based on the first and second quantities. The method of claim 1, wherein the hair fibers are textured hair, such as African hair. Method according to any one of claims 1 to 2, in which PB = Plx P2. A method according to any one of claims 1 to 3, wherein step a) comprises measuring the tensile strength by performing a tensile test on the hair fibers. A method according to any one of claims 1 to 4, wherein step a) comprises measuring fatigue failure by performing a cyclic fatigue tensile test on the capillary fibers. A method according to any one of claims 1 to 5, comprising treating the hair fibers before carrying out the measurements of steps a) and c).

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