HAIR CARE 55


illustrated by SEM images of the single hair fiber treated with polymeric solutions (Fig 5). 2 wt. % active polymer aqueous solution was sprayed on a hair fiber which was knotted after drying to induce mechanical strain. Polyurethane-34 forms a smooth


continuous film that withstands mechanical strain without breaking or flaking.


High humidity resistance Consumers expect hair styling product efficacy to be expressed in long lasting style retention even under challenging conditions. Typically, the High Humidity Curl Retention (HHCR) method is used to characterize styling polymer performance. Figure 6 shows HHCR results of conventional polymers versus Polyurethane-34. The comparison can also be viewed as performance versus biodegradability. The test was performed with polymeric


(2 wt. % active) aqueous solutions on undamaged Caucasian hair tresses (5 tresses per polymer). Approximately 0.02 g of solution was applied per 1g of hair. Hair tresses were subject to harsh conditions: 90% relative humidity at 30°C for 6 hours. Curl retention curves show that Polyurethane-34 outperformed PVP K90 and VP/VA copolymers in humidity resistance. When biodegradability comes into focus, Polyurethane-34 takes preference over acrylate copolymer even if their humidity resistance profile closely matches one another. When acrylate copolymer was tested along with Polyurethane-34 by OECD 301 B and 302 methods respectively, acrylate copolymer


Acrylate Copolymer Polyurethane-34


Figure 5: SEM images of the hair fiber coated with the polymeric film.


100 90 80 70 60 50 40 30 20 10 0


0 50 100 150


n Polyurethane-34, 60% degradation in 28 days n Acrylate copolymer, no degradation in 28 days n PVP k-90, persistant according literature n VP/VA copolymer, no biodegradation data available


200 Time (min) Figure 6: High humidity curl retention vs biodegradation.


250


300


350


400


May 2020


PERSONAL CARE NORTH AMERICA


Curl Retention %


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