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Polymers in Personal Care
By: Eric Abrutyn, TPC2 Advisors Ltd., Inc.
Posted: June 28, 2010, from the July 2010 issue of Cosmetics & Toiletries.
page 2 of 7
Polymers also can be amorphous, lacking a positional order on a molecular scale and therefore softening over a temperature range known as the glass transition; e.g., polystyrene or poly- methyl methacrylate. Or, they can be semi-crystalline, having a true melting point at which the molecule becomes disordered. In addition, they can have both amorphous and semi-crystalline regions within the same polymer. A sampling of the various polymers and functions they serve in formulations is described later in this article.
Further, polymers can be characterized by the arrangement of the atoms in the chain, e.g. repeated olefin groups or polyolefin; through their physical attributes such as tensile strength or density, e.g. high density polyethylene; based on the dominant backbone, e.g. polyester, the reaction of a multifunctional hydroxyl- and/or carboxyl-functional group with other possible side reactions; or how they are produced—esterification, amidation, etc. Since there is a limited and uniform system of classifying polymers, the terminology has evolved based on historic terms or trade names, such as nylon, as well as the industry that is utilizing the polymer, in conjunction with the growing complexity of polymer science.
For personal care, it is important first to understand the critical departure from the IUPAC and CAS naming: INCI assignments for polymers typically are based on starting monomers3 as opposed to the final resultant polymer. This is because not all polymers are easily defined; they are actually a complex mixture of reactants and by-products. Thus, basing a polymer’s name on the starting monomer is easier than trying to determine the final composition. In addition, a generic naming protocol is used if the assigned name includes four or more monomers; in this case, the name assignment would be based on its predominant chemical class; e.g., polyacrylate. Molecular weight, physical form and branching do not typically play roles in the nomenclature assignment. Finally, polymers can be differentiated as being either natural-derived (or sourced) or synthetically produced. INCI assignments normally fall within specific categories. Examples are as follows.
Homopolymers: Consisting of a chain extended by one type of monomer, e.g., polyisobutene or polystyrene.
Copolymers: Consisting of at least two monomers, with the slash symbol “/” used between each monomer, which are listed in alphabetical order; e.g., acrylates/aminoacrylates/C10-30 alkyl PEG-20 itaconate copolymer. Other examples include:
- Acrylamides copolymer, a copolymer of two or more monomers consisting of acrylamide or simple alkyl derivatives of acrylamide;
- Acrylates copolymer, a copolymer of two or more monomers consisting of acrylic acid, methacrylic acid or their simple esters;
- Simple vinyl polymers, designated by attaching the prefix poly to the monomer name, e.g., polyalkylenes; these are carbon chain polymers with double bonds along the monomer chain, e.g., polystyrene, polyethylene and polypropylene, polyolefin, etc. (designated as -C=C-); and
- Hetero-chain polymers, containing more than one atom type in their backbone. These polymers are grouped according to the types of atoms and chemical groups, e.g., carbonyl, amide or ester, located along the backbone. Another important class of hetero-chain polymers includes polysiloxanes, which have a -Si-O- backbone with methyl or other substituent groups attached to silicon.