HAIR CARE 53


Multifunctional film-former for sustainable hair care


n Yuliya Berezkin - Covestro LLC, US Dr Sophie Viala - Covestro AG, Germany


Protecting our environment is a common goal of many industries, consumers and regulators. In the last five years, Personal Care manufacturers truly became global leaders in the concerted efforts to reduce the environmental footprint of cosmetic products. As part of this effort, regulatory agencies in the US and Europe are responding to the consumer pressure to address the issue of microplastics. This trend has prompted cosmetic manufacturers and their suppliers to innovate. Their research focuses on finding ingredients that minimize an impact on the environment, while still satisfying consumers’ tough performance criteria as they demand multifunctional products that are convenient and effective. To address this demand from the market,


Covestro offers a portfolio of sustainable film-formers based on polyurethane chemistry (PUR) for the cosmetic industry, sold under the trade name Baycusan®


. The


polymer structure was optimized to achieve strong performance and to offer better biodegradable polymers than state-of-the- art film formers.


R


C O


ester


multifunctional performance of the film former Baycusan®


In this article we will describe the C 1001 (INCI-name:


Polyurethane-34) that satisfies strict performance and sustainability requirements in hair care applications: The efficacy of this unique-to-Covestro product has been investigated and compared to currently used polymer film-formers.


Sustainable nature of the unique (PUR) chemistry The biodegradability of polymers depends on their nature and the presence of heteroatoms in the backbone. It is well known that substances composed of Carbon-Carbon bonds are hard to break, and C-C links are not susceptible to biodegradation either. In contrast, chemical bonds in the PUR polymeric backbone are relatively easy to cleave. These chemical bonds can degrade by


hydrolysis which is promoted by external physical parameters, such as temperature, pH, and/or UV light. These cleavable bonds can also be processed by enzymes. Examples of typical links in the


O R O ether R


N H


O C


polyurethane polymer backbone are shown in Figure 1. Another distinct feature of PUR film


formers is their segmented structure consisting of alternating soft and hard segments, imparting on them unique mechanical properties on hair fibers, as it will be shown later in the article. The kinetics of the biodegradation


greatly depends on the soft block nature and content in the polymer. Biodegradation beaks high molecular weight polymer into lower molecular weight species which are being further metabolized. Our data showed that a highly biodegradable soft segment in PUR polymer can promote ultimate degradation of both soft and rigid segments up to 95% within 28 days.1,2 Key facts of biodegradability of PURs:


l High density of cleavable bonds promotes enzymatic degradation


l Structure of the polymer will dictate the kinetics of degradation


l The polymer is ultimately degraded into CO2


, H2 O and mineral salts


In a test for ready biodegradability (OECD 301, 28 days) the 60% pass level


N H


urea


N C O O


H urethane


Figure 1: Structure of polyurethane film-former. May 2020 PERSONAL CARE NORTH AMERICA


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