FT Rheology (LAOS) Application in Cosmetics

Seher Ozkan, Tim Gillece, Hani Fares, Germain Pucetti, Larry Senak and Karen Winkowski

Ashland Specialty Ingredients, Corporate Research Center, Wayne, NJ

INTRODUCTION

METHODS

CONCLUSIONS

RESULTS Sensory properties of personal care products contribute substantially to the overall consumer acceptance.

Sensory Evaluation Primary skin feel parameter, such as initial spreadability, and secondary skin feel parameters, such as rub-out spreadability, slipperiness/lubrication were rated. A randomized complete-block experimental design was carried out for evaluation of the samples, where panelists are the “blocks” and the samples are the “treatments”. Each panelist evaluated all three samples to form a “complete block”. Data was analyzed by linear regression.

Performance evaluation of surface smoothness of active gels Frictiometer FR700 (Courage-Khazaka) with flat teflon probe end was used to test the samples on 3 subjects. 100 l of benchmark or test gel was applied to the clean skin of volar forearm of subjects. One product tested per arm (left and right). RF device is pressed on gel deposit and lightly spread to cover device front end. Friction measured for one minute while slowly moving over 5cm* 4cm surface .

FT Rheology (LAOS) ARES-G2 rheometer (TA Instruments) with 25 mm smooth stainless steel parallel plates was used to apply Fourier transform analysis on the Large Amplitude Oscillatory Shear (LAOS) flow data collected at room temperature and 50°C. The sinusoidal stress response signal collected from the sample was analyzed by the FT transform module of the instrument software. The sinusoidal signal was deconvoluted into odd and even harmonic components having physical interpretations. Multiple steady-state wave forms were used for data analysis (typically three cycles of data were collected and the last two cycles, where the data had equilibrated were

used). (*)

Using FT analysis on LAOS data can be an easy and effective method in characterizing rheological behavior and their correlations with sensory ratings of cosmetic formulations. (*)This data has been published in “Ozkan S, Gillece TW, Senak L and

Moore DJ. Characterization of yield stress and slip behavior of skin/hair care gels using steady flow and LAOS measurements and their correlation with sensorial attributes. Int J Cosmet Sci. 2012 “

Tomato ketchup Mayonnaise

Hair gel Honey

Our results show that slip, shear banding and thixotropy behavior are linked to sensorial perception. Literature reports that slip can be detected in LAOS analysis using the even harmonic intensities. The results in our study also confirmed this conclusion.

0

2

4

6

8Cushion

Easiness of

Initial Spreadability

Easiness of

Rub-out Spreadability

Tack

Break

Pick-Up

PAA/VP-XL

PAA-XL

Friction results

Smoother

Higher intensity of even harmonics indicate higher slip behavior. These results show that higher slip is linked to lower friction forces.

R² = 1

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0 2 4 6 8

Re

lati

ve

In

ten

sit

y, I

2/I

1

Initial Spreadibility Rating

R² = 0.95

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0 2 4 6

Re

lati

ve

In

ten

sit

y,

I 2/I

1

Rub-Out Spreadibility Rating

(b) (c)

(a)

Correlation of LAOS data with conventional rheology data and sensory ratings: Linear regression fit for relative intensity (I2/I1) versus slip velocity coefficient , s, collected with smooth surfaces at 400% strain (a) and sensory ratings versus relative intensity (I2/I1) data collected with smooth surfaces at 400% strain (b and c).(*)

PAA/VP-XL PAA-XL

Case Study 1

Case Study 2

Lissajous plots for benchmark and our formulation in comparison. Left side is 25°C and right side is 50°C. Red is Formulation A and blue is benchmark conductive gel.

0

0.001

0.002

0.003

25°C 50°C

Inte

nsi

ty o

f se

con

d h

arm

on

ic, I

2 Benchmark

Fla12283-071Formulation A

0

50

100

150

200

250

300

350

400

450

Clean skin Fresh app Post 1 min RF Post 3min RF

Surf

ace

fric

tio

n fo

rce

Steps

Benchmark

Fla12283-071Smo

oth

ne

ss

Formulation A

Comparison of LAOS analysis results with friction test results

Correlation of quantitative instrumental parameters, such as rheological and tribological measurements, to subjective sensorial ratings may help better understanding of consumer perception. Recently, Large Amplitude Oscillatory Flow (LAOS) experiments coupled with Fourier Transform Analysis have been utilized to study the correlation between sensorial ratings of cosmetic formulations and their rheological properties. In addition to FT analysis of LAOS data, the sinusoidal signal of stress and strain data collected from Large Amplitude Oscillatory Flow (LAOS) can be plotted as a function of each other. This representation is referred to as Lissajous figure and represents an excellent visual aid for qualitative analysis.