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Texture Analysisin the Nailcare Industry
Texture Analysisin the Nailcare Industry
Stable Micro Systems
Cosmetic Nail Products
and the varietyof methodsavailable fortheir physical
propertymeasurement
Cosmetic Nail Products
and the varietyof methodsavailable fortheir physical
propertymeasurement
2 | Texture Analysis in the Nailcare Industry
The way we look and feel is moreimportant than ever in the age ofconstant selfie-taking and the
abundance of cameras at every socialgathering.
This is not to mention the impossible beautystandards set by photo-shopped billboards andmagazine shoots that ordinary people feel theyhave to live up to. It is no surprise thatcosmetics are more popular than ever, with theglobal cosmetic market estimated to reach 675billion USD by 2020. This growth comes withconstant changes in market regulationsincluding new product registrations andingredient restrictions – keeping track is adaunting task for both big and small brands.
A large proportion of this market is taken upby nail products, which have come on a longway since their origins in Ancient Babylon.Thanks to makeup artist Michelle Menard,inspired by the new innovations in automobilepaint in 1920, we no longer need to embellishour fingers with henna, egg whites or gelatin.Instead, we have widespread access to anenormous range of glossy paints, and morerecently spray paint nail polish, four-week gel
manicures and ready-decorated nail wraps.
$8.51 billion was spent in salons alone in 2015.In a 2015 study, nail professionals were askedabout their biggest challenges – the greatestbusiness challenge was voted “building andretaining clientele” and the number onetechnical spot was taken up by “stayingcurrent on trends and products”. The first pointrelies on consistently high product quality andthe second on ensuring new products are up tothe standard expected of the brand.
Why is the nail industry growingso rapidly?There are a number of powerful factors. Manypeople have taken up nail technicianqualifications in hope of a second income in adifficult economy. Social media has alsopushed the trend, encouraging nail decorationas it has become extremely popular to sharephotos of nail art.
Perhaps most importantly, however, nail care isno longer restricted to grooming. Standing outfrom the crowd is now paramount, bringingwith it a wealth of nail art options and newexciting colours and effects, with the possibility
Texture Analysis in the Nailcare Industry
“Social mediahas also
pushed thetrend...”
The Stable Micro SystemsTA.XTplus Texture Analyser
Cosmetic Nail Products and the variety of methods available for their physicalproperty measurement.
INTRODUCTION
Texture Analysis in the Nailcare Industry | 3
“... looking for reliableways ofquantifyingtheproperties of their newproducts...”
of sending off for nail wraps printed with adesign or photo of your own or have an imagedirectly printed onto your fingernails using aprinter not unlike the traditional laserjet.
Growth is driven by these new nail technologyproducts, most significantly gel polish, whichhas been a massive hit with salons andconsumers alike. Salons are attracted by aquick and easy application, consumers byexcellent durability of up to four weeks that isnot possible with ordinary polish. The drivehas until now pushed consumers into salonsor to buy their own UV setting lamps for homeuse, but gel polishes are becoming availablethat do not require a UV lamp, offering a goodcompromise between salon gel services andtraditional at-home polish, lasting aroundseven days.
Changing marketTo keep up with this rapidly changing andcrowded market, nail product manufacturersare looking for reliable ways of quantifyingthe properties of their new products. This keepsthem up to date with the explosion of noveltrends, helps compare these to the old popularproducts, or simply keeps brand qualityconsistent to fight off the competition.
Nail product quality and appeal is put to thecritical test of the consumer. Appearance is ofutmost importance, with durability and easeand texture of application also essential. Theseproperties must be analysed accurately andconsistently by nail product manufacturers,simultaneously studying the optimumformulation and manufacturing methods toachieve the best results while keepingingredient and manufacturing costs as low aspossible.
“Free-from” products have their own struggle.Some consumers are worried about thepresence of harsh solvents on their nails andthe possibility that they are causing damage,or negative effects on environment, while stilllooking for top quality and to keep up with thelatest trends.
Now some companies are looking at waterbased polishes. Without acetone and similarsolvents to carry heavy polymers and toevaporate quickly for a speedy drying time,high quality is an even greater challenge thanbefore. This has been picked up by thepremium end of the market and brands suchas The Body Shop and Zoya are becomingmore active in natural nail colour withproducts that promote a message of skin andnail health and natural ingredients.
Challenges in testing: Nail ProductAssessment MethodsStable Micro Systems has developed a range oftests to meet these needs, quantifying thetextural or physical properties of both wet anddry polish, nail wraps and self-adhesive nails.These employ the Texture Analyser and can becustomised to cover nail products at any stageof the production process to assess the optimumparameters required for a perfect end product.
Traditional ASTM or ISO methodology isdifficult to apply to nail products as there arelimitations on sample preparation and testmethods. Instead, custom innovative testsmust be developed to closely imitate the useand application of nail products, and putproperties to the test in this way.
4 | Texture Analysis in the Nailcare Industry
Texture Analysis in the Nailcare Industry
NAIL POLISH DRYING TIMENail polish has been developed to have a fasterdrying time with brands claiming “dry in 60seconds” or “quickdry”. However, smudging amanicure is still a common complaint. Thereare also difficulties accelerating the dryingtime of more natural polishes containing fewervolatile solvents. New products must be testedfor this in a consistent way.
A Nail Polish Adhesion Rig* [1] and methodhave been developed to provide the solutionto this assessment requirement. During thepolish drying time test, a channel 20cm longis filled with polish to a specific depth andwiped level using a glass rod. At this point atimer within the Exponent software testsequence is started.
The channel is seated on top of the AdhesiveIndexing System that has ten detents and soten test sites are available by simply slidingthe platform along. A 1 inch detented ballprobe is used for the tests, which can be turnedto allow a clean test site without replacing theprobe or the requirement to clean and dry thetest probe between tests. This is used toperform an adhesive test at the first test site.
A specific force is held for 5 seconds to allowa bond to form. The probe is then quicklywithdrawn, breaking the nail polish bonds,and the force to do this is measured.
The channel is moved along to the next siteand the test repeated. A set of ten tests areperformed in this way with pre-set time delaysbetween the tests [2a]. Tests are performedover the whole drying period of the polish.
Several measurements can be made from theforce-time graph overleaf [2b]:
i) The maximum force needed to withdrawthe probe from the sample is a measure ofthe strength of the bond or theadhesiveness/ stickiness of the polish. Theinitial wet polish has a very low adhesiveforce. As time passes the stickinessincreases until it peaks, then drops off.After the highest adhesive force cycle isobtained the polish is usually ‘touch dry’.
ii) Softness is defined as the time the probetakes to sink into the surface of the polishbefore the force reaches 5g. The softnessdecreases with drying time until it reaches aplateau, at which point the polish is touchdry.
iii)Stringiness is the time period over whichthe probe remains adhered to the polish. Ifthe polish and probe immediately losecontact after the probe has withdrawn, thepolish is not stringy. A stringy sample willleave a force on the probe for a longertime.
“... smudginga manicure
is still acommon
complaint.”
Nail Polish Adhesion RIg
1
Ten adhesive tests of a polish sample changing from liquid to solid as it cures over a period of 40 minutes
2a
*Community Registered Design
Texture Analysis in the Nailcare Industry | 5
The series of adhesion tests is automated by aunique test sequence developed in Exponentsoftware, with parameters such as the delaybetween tests, the number of repeats, appliedforce and holding time adjusted by the user ifnecessary. Additionally, an analysis macro isavailable to measure the above three propertiesacross all repeats at the press of a button.
Figure [3] shows graphs of these properties fortwo samples. The purple gel sample is moredesirable than the pink polish in every case asit dries more quickly and with less tack force.It is also initially harder and so will be lessprone to initial film damage when a wet layerof polish remains underneath the touch drysurface. This method is also suitable for otherliquid curing materials such as nail adhesive.
MECHANICAL PROPERTIESOF DRY POLISHA manicure is subject to a lot of abuse as thewearer goes about their daily life (opening jars,cooking, typing on a keyboard). For repeatpurchase of a nail polish, it must be able tostand up to this type of use. As well as theadhesion properties mentioned above, thestiffness and toughness of a polish are allextremely important. An overly stiff, brittlepolish would be undesirable as it would breakwhen a nail is bent when opening a soda can,for example. The low stiffness is important forthe polish to follow the nail as it bends. A highstrain to failure is also crucial, or the polish filmwould break under the slightest deformation.
“... theadhesionproperties... stiffness and toughness of a polish areall extremelyimportant...”
Comparison of softness, stickiness and stringiness of two polish samples
Zoomed in section of one adhesion cycle explaining parameters of interest
3
2b
6 | Texture Analysis in the Nailcare Industry
Texture Analysis in the Nailcare Industry
All of these properties can be examined usinga biaxial tension method. A 3cm by 3cm filmspecimen is cut from a 21cm strip set in apurpose-built PVC vacuum formed mould. Itis then tested in the Film Support Rig [4],with a circular clamp surrounding a 1cmdiameter circular aperture.
A 5mm stainless steel ball probe is drivendown into the sample, applying force untilrupture. Stress and strain are recorded, fromwhich the mechanical properties of the drynail polish can be easily determined using theready-made analysis macro.
Using this method, manufacturers can identifyweaknesses and adjust nail polish formulationsaccordingly. Figure [5] shows puncture testson two samples. The red curve shows astronger, stiffer polish compared to the othersample. Their toughness values are similar,with toughness given by the area under thecurve.
In addition, by cutting the samples and testingthe same batch daily over the course of a weekor fortnight, the change in character of thepolish can be assessed over the timescale of amanicure. A polish with desirable properties isonly a high quality product if those propertiesare retained day after day. The customer wouldbe disappointed if their manicure degradedquickly and started chipping after three days.
Figure [6] shows tests on three samples of thesame polish carried out two, five and ten daysafter the polish was poured from the bottle.
Figure [7] shows best fit line graphs oftoughness, stiffness and failure strain of threedifferent samples over the course of 11 days.The blue sample is the most desirable as itstoughness remains constant, it is the least stiffand its failure strain is always greatest.
“... thechange in
character ofthe polish
can beassessed...”
Pink quickdry polish two days, five days and ten days
after initial pour into mould.
6
Two different polish samples tested two days after initial pour into mould: a gel polish and a quickdry polish
5
The comparison of toughness, stiffness and failurestrain of three polish samples
7
4
Film Support Rig
Texture Analysis in the Nailcare Industry | 7
ADHESIVE PROPERTIES OF NAIL WRAPSNail wraps are flexible adhesive films that aresmoothed onto the nail’s surface and trimmed.They provide an opportunity for intricatedesigns that can be printed by themanufacturer that would otherwise be difficultto paint by hand. The design will be consistentacross all nails and removes the difficulty ofusing the non-dominant hand to paint.
Nail wraps must have high initial adhesion tothe nail to provide a manicure that will last. Ifthere are weak spots in the adhesive, an edgemay peel and the finish will not last. Theadhesive strength of the wraps can be testedusing the TA.XTplus Texture Analyser. Ahigher adhesive strength and work of adhesionare generally desirable.
A simple test has been developed to measurethe adhesive force, the work of adhesion andthe stringiness of the adhesive on the reverseside of the wraps. To test for variation betweenor within samples, a large number of tests isrecommended. The multi-hole indexing plate[8] by Stable Micro Systems enables ten teststo be made in quick succession. Ten nail wraps
are applied to the underside of the plate, whichis attached to an Adhesive Indexing Systemsecured on the instrument bed. A 7mmdomical probe is brought into contact with thewrap. A specific load is applied for 3 seconds.The probe is quickly pulled away from thewrap during which time the adhesion forcesare measured. Graphs showing the adhesiveforce of two different nail wrap samples areshown in Figure [9]. The higher adhesive forceof the black sample than the pink shows it ismore suitable for this application.
“Nail wrapsmust have highinitial adhesionto the nail...”
Multi-hole indexing plate for the Adhesive Indexing System
Adhesive tests of two different nail wrap samples
8
9
8 | Texture Analysis in the Nailcare Industry
Texture Analysis in the Nailcare Industry
TENSILE PROPERTIES OF NAIL WRAPSSelf-adhesive nail wraps can be tricky to fit tothe nail. To avoid ripples in the surface, thefilm must be flexible enough to be smoothedinto small corners but also taut across thesurface of the nail. The wrap must also betough enough to avoid tearing duringapplication and have a reasonable strength.
All these properties can be assessed using atensile test. There is usually limited samplepreparation that can be carried out with nailwraps as they come in specific lengths, shapesand widths, unless the film is tested in thefactory before strips are cut. Specimengeometry greatly effects the forces reached intensile testing and so must be carefullyrecorded.
Rubber faced tensile grips attached to theTA.XTplus Texture Analyser provide a surfacewith a good grip to prevent slippage during atest. Using this test, manufacturers can identifyweaknesses and adjust formulationsaccordingly.
A wrap is cut to a 10mm width and loadedinto the grips [10] with a 5mm spacing. Thegrips pull apart, initially stretching the wrapand then breaking it. The force-time graph ofa wrap being stretched and broken is shownin Figure [11].
This test can also be used to measurerelaxation properties. The film is stretched asmall amount and released. By comparing thework of tension and relaxation a measure ofspring recovery can be calculated.
“Specimengeometry
greatly effectsthe forces
reached...”
Tensile grips fitted to the TA.XTplus Texture Analyser
Tensile test of a nail wrap sample
10
11
CONCLUSIONThe nail product market is vast, competitiveand constantly changing. As a manufacturer,in order to beat off your competition when anew trend becomes popular, or simply tomaintain the high standards of product qualityyour brand stands for, texture analysis isparamount.
Stable Micro Systems has developed a widerange of tests that can be applied to a largebracket of nail care products to ensure yourquality never falters and you will remain thecustomer favourite.
“The nailproductmarket is vast,competitiveand constantlychanging.”
Original text© 2017 Stable Micro Systems
Stable Micro SystemsVienna Court, Lammas Road, Godalming, Surrey GU7 1YL, UK
Tel: *44 1483 427345
Fax: *44 1483 427600
Email: [email protected]
Web: www.stablemicrosystems.com
Texture Analysis in the Nailcare Industry | 9
