SUN CARE
63
Naturally derived film former for water resistance
Thomas O’Lenick – SurfaTech ABSTRACT
For a long time now, sunscreen formulations have utilized polymeric film formers to provide water resistance. In recent years, the concern about the film former impacting the environment has pushed the personal care industry for natural water resistance. Bis-octyldodecyl Dimer Dilinoleate/Propanediol Copolymer (BODP) is a naturally derived film former utilized in inorganic sunscreen formulations to provide water resistance. BODP also provides dispersant properties for ZnO and TiO2
thus reducing whiteness and provides the ability to apply inorganic particles onto wet skin.
Sun care products are under a magnifying glass. American activists Environmental Working Group reported that the majority of sunscreens sold in the US contain chemicals that are deemed harmful to the environment.1
This has led to the
banning of specific sunscreen actives in Hawaii.2 In more recent times, the film formers in these
sun care products have also been targeted. These film formers are traditionally high molecular weight polymers that are incorporated into products to impart water-resistance.3 Common film formers include acrylate and
vinyl polymers like acrylates/octylacrylamide copolymer,4
acrylate copolymer.5
and VA/butyl maleate/isobrynyl These polymers help hold
the sunscreen actives on the skin, which prevents wash off when a consumer is swimming or sweating.
Thomson et al utilized scanning electron
microscopy (SEM) imaging to show how sunscreen formulations were deposited onto pig skin. This study showed the introduction of polymeric additives to the formulation allowed for the formation of separate films.6 These films have different film structure based
on the polymer used. When utilized in sun care, it is important to consider the fact that these film formers will be washed off of the skin and into the surrounding environment. Recent studies have shown that debris from
high molecular weight polymers or plastics have been found on shorelines globally.7
Wilske
et al showed that poly(acylates) have very poor biodegradablilty and will persist in the environment for a long period of time.8
www.personalcaremagazine.com Over time, these plastic particles can be
worn down by the environment into smaller and smaller pieces of plastic. Once these plastics reach the size of 5mm in size it is considered to be a microplastic.9,10 These microplastics are present in personal Microplastics, when introduced
care products.11
into the environment, can harm wildlife. Rotjan et al showed that Astrangia poculate, coral polyps consume microplastics beads preferentially over brine shrimp eggs,12
while Rochman Lab at the
Ontario Ministry of the Environment in Canada found microplastics in a wide number of fish fillets and livers of all seven spices studied.13 Microplastics are clearly accumulating in
wildlife and humans around the world. Thiele et al concluded that more work is needed to understand the relationship of microplastics in capture fish and fishmeal.14
It is easy to focus on
the bad side of plastics, but we cannot forget the good side of plastics. One such example of the good side of
plastics is how implantable medical devices have prolonged lives of many people around the world.15
Daily life as we know it could not exist
without plastics and until now, people could not enjoy a day at the beach without being sunburned without the incorporation of a high molecular weight polymer into their sunscreen. In this article, I describe a novel,
biodegradable polyester bis-octyldodecyl dimer dilinoleate/propanediol copolymer (BODP). This copolymer is synthesized by reactants from rapeseed oil. Rapeseed oil has been eaten in limited
quantities due to the high levels of erucic acid,16 so utilizing the oil for cosmetics will not affect the food chain. It has also been previously reported that BODP has been shown to be inherently biodegradable in an OECD 301B study.17 BODP is evaluated as a replacement for
conventional film formers in sun care. Several techniques will be utilized in the evaluation of this material including optical microscope to test the agglomeration size of ZnO and TiO2
particles
in solution, in vivo SPF, and an application to wet skin test.
Polymer performance BODP has been studied extensively for its ability to provide a water resistance in sun care formulations that utilize organic filters.17
This
study will focus on BODP’s ability to provide film forming in formulations with inorganic actives. Providing water resistance to zinc oxide (ZnO) and titanium dioxide (TiO2
) formulations become
more difficult due to the agglomeration and lack of compatibility of these particles with commonly used rheology modifiers.18 Furthermore, in order to avoid the clumping
of solid particles used in broad spectrum mineral sunscreens with titanium dioxide and zinc oxide the correct combination of film formers is needed.19
with ZnO and TiO2
In order to test BODP’s compatibility , dispersions were created in
several solvents. As seen in Figure 1, TiO2
in both solvents
had a large amount of agglomeration. When 10% wt/wt BODP is added to the solution, the agglomeration was drastically decreased. The
May 2023 PERSONAL CARE ,
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