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Cosmetics and Personal - Capability Statements

Lipstick bullet bend flexure testing

Lipstick bullet breakage by cantilever bend flexure

The important attributes for cosmetic products are related primarily to aesthetics and texture. Colour depth, choice of lustrous shine or matte finish and the feel of the product upon application to the skin, for example, are key selling points for lipsticks. Of equal importance (but less obvious to the consumer) is the durability of the cosmetic through repeated application – influenced by composition. The bullet-style dispenser for lipstick must perform reliably under cantilever-type flexure loading through forces applied by the lip at the tip of the bullet, and resisted at the end of the barrel container. The test system must replicate the conditions under which the lipstick will be stressed – holding the dispenser firmly and applying the force with a special fixture to ensure the sample will break due to bending force rather than being cut. The lipstick may fail either in shear or by the classic pure bending compression/tension force distribution: this test will determine either characteristic in the sample. By repeatability and accurately measuring the peak force at break, the manufacturer is able to evaluate the effect of formulation changes upon the performance of the product, either for aesthetic reasons: improving colour, finish and texture, or for manufacturing changes such as using different raw materials. This bend test is also applicable to differing designs of the lipstick tip – bullet, bullnose or chisel – due to the design of the fixture.

Mecmesin Systems: MultiTest motorised test system

Case Study: Lipstick bullet breakage test

Toothbrush bristle pull-out testing

Toothbrush bristle cantilever bend and pull-out testing

The action of brush bristles in any in-service situation is quite a complex system. Many forces are applied, often in multiple directions and the action of frictional forces also has an impact on the durability of the product. In addition the retention of the bristles (filament shedding performance) is an important consideration. A simple manual toothbrush is subjected to these conditions, as well as industry test methods applicable to cosmetics and personal health – specifically dental equipment standards. A versatile and complete testing solution should be able to perform the bristle stiffness test, in which the complete brush tufted area is rubbed against a metal grid at constant speed – subjecting the bristles to a cantilever bend force. The forces recorded then categorise the toothbrush into consumer categories from soft, through medium, to hard. Shedding performance can be measured by pull-of/pull-out for individual filaments or a ‘tuft’ of bristles with a surgical clamp and a pin chuck fixture, respectively. Location of the toothbrush head should be secure in order to eliminate flexure in the plastic (polypropylene) housing itself. A robust console-operated system would allow testing in a mass manufacturing environment, with simple operation for production staff, giving the confidence to meet stringent quality standards.

Mecmesin Systems: MultiTest console-controlled force test system

Case Study: Toothbrush Stiffness Tester

Cone penetration of food or cosmetics

Spreadability texture analysis of cosmetics or food by cone penetration

The mechanical properties of food and most cosmetics are more readily termed texture (also mouthfeel in the case of foodstuffs). The way these products are acted upon by forces determines the exact texture attribute, such as firmness, stickiness (adhesiveness) and spreadability. As such these items may be mechanically tested and the results used to quantifiably compare the effect of relevant production and manufacturing factors - for food: cooking time, relative mix of ingredients – on the consumer’s sensory perception of texture. The engineering concept of penetration resistance has direct correlation to the texture attribute of spreadability and the use of a cone-shaped penetration probe for a force test will allow repeatable and accurate texture analysis of a product judged by this quality. The matching container fixture for the sample is influential in the results as its degree of resistance to allowing the product to spread freely, but enables consistent comparative testing. Typically this fixture is shaped as an internal cone corresponding to the same dimensions (90 degree vertex angle) as the probe.

Mecmesin Systems: MultiTest force test systems, compression fixtures

Case Study: Margarine Spreadability

Alumina sphere crush test and size comparison to a penny

Single pellet crush of alumina petrochemical catalytic carrier

Crush strength is the peak compressive force required to take a sample to its [ultimate] compressive strength at which the onset of failure occurs. A single pellet crush test could be applicable to products such as pharmaceutical tablets (or similarly shaped confectionary), ceramics and industrial catalysts formed of solid material. The implications of failure in these industries is of varying degrees of impact – the industrial catalyst may result in plant shutdown and thus stringent testing is required. The physical shape of the pellet affects the exact test standard method: tablets and spheres being crushed by a different method to extrudates, granular or irregular shaped products. To accurately measure the mechanical properties of a single sphere under load, the use of self-levelling compression plates should be employed. A computer-controlled test stand will enable the first peak load to be captured as the sphere fractures and provision to avoid overloading of the loadcell as the fixture attempts to move beyond this point should be considered. Some examples of the spherical carrier are less than 1mm in diameter and control of the crosshead’s displacement is essential – either physically or by means of the software.

Mecmesin Systems: MultiTest computer-controlled force test system, self-levelling compression plates

Case Study: Alumina Sphere Crush Test

Cosmetics brush pull-out testing

Cosmetics brush pull-out testing

Our client manufactures cosmetics brushes for all applications, and so has a very diverse set for bristle integrity testing. Gripping the shaped handles and bristle tips in a repeatable way demanded more than a single standard vice grip.

Mecmesin designed a system of overlapping plates with cutouts for each brush head profile, to gather and trap the bristles uniformly in a vice action, axially aligned under the loadcell. Barracuda grips hold the handles securely for reliable and accurate repeat testing.

 
Cylinder paper peel test

90 degree cylindrical peel testing

Floating roller peel jigs are available for security card lamination testing, but our client was testing the adhesion of the paper around cigarrette filters. To accommodate the small cylindrical shape required smaller and closer rollers, and a better sample loading design.

Mecmesin responded with customised fixtures for different sizes of filter, employing four roller bars instead of two. Loading samples for repeatable 90 degree peel testing is quick and easy, saving time and cost.

Container cap removal torque test system

Hygienic disposal bin closure testing

A manufacturer of hygienic disposal bins came to us with a nappy (diaper) disposal unit with a rotary intake mechanism. The bin was 30 cm wide and the opening at 45 degrees, making holding of the bin for proper axial rotation somewhat difficult.

Mecmesin designed a rotating platform at 45 degrees to rotate the bin about the axis of the rotating mechanism, but the width required an additional modification of our standard Vortex torque tester for increased column separation. The result was a tester for rapid and effective, repeatable testing to ensure consistent quality of the manufactured units.

Cosmetics product pull-out testing

Cosmetics packaging performance

Sometimes a client approaches us with a range of requirements for a number of their products. Using their universal testers for a variety of testing, they also need custom and versatile fixtures. Cosmetics packaging, for example, frequently combines design-led profiling with light handling, as in mascara tubes and brushes, attractively-curved lotion containers, and lipsticks. Some of these imply very light rotational torque, others maximum strength in lightweight design, for daily use.

Mecmesin custom grips assure axial alignment, secure holding and minimal deformation that might adversely influence test results and repeatability. In this example, compression, tensile strength and torsion strength were addressed in a suite of fixtures for a variety of popular products.

 
Cosmetics container release torque and pull-off test

Cosmetics container caps, lids and closures release torque and pull-off force

A consumer packaging manufacturer may produce a variety of containers for the cosmetics industry, which in addition to their functional requirement, may have strong design influences. The range of shapes and sizes that result need a versatile quality testing solution to evaluation the effectiveness in sealing plus ease of opening for the container caps. An adjustable clamp, able to securely grip different bottles and jars (possibly made from glass) is needed to measure the torque required to release the lid of the jar. A simple, light and portable digital desktop instrument, measuring the peak value as the lid is released by hand can quickly assess the quality of the screw top closure. For flexible plastic containers, with plastic caps, there could be a danger of the lid being pulled off. A tensile tester with appropriate grips and fixtures will provide repeatable pull-off resistance appraisal.

Mecmesin Systems: MultiTest motorised test system, CAPTEST

Case Study: Cosmetic Packaging Pull-Off Test