Additive (adhesives, paints, and plastic)

Description

In terms of polymers or paints, an additive is a chemical substance, usually in small quantities, that is added to a base material for the purpose of modifying the properties of the end product. Additives change the performance (flexibility, UV resistance, etc.) or appearance (color, opacity, etc.) of the pure polymer. Plastics, adhesives, and paints often contain around 20 additives, most of which are unlisted components because they are considered trade secrets. This in effect conceals any and all toxicity interactions to humans and the environment. A secondary complication is that some of the additives are weakly bound to the polymeric matrix which can lead to separation and/or degradation. The combination of these factors means that additives have to potential to create problems in all stages of a plastics lifecycle, including preparation, handling, lifetime use, and waste disposal.

Examples of additives include:

Additive Type	Typical concentration (%)	Description	Example compounds	Comments
Accelerant	0-50	Increases the reaction rate of polymerization and decrease storage life, working life, gel time, etc.	Used for polyesters (Styrene), rubbers (sulfur compounds) along with some activators (peroxide, Zinc oxide, amines, Stearic acid, etc.); also called Curing agent, Hardener, promoter, accelerator, and vulcanizer (for rubber)	Incorrect proportions and poor mixing will weaken the polymer structure
Adhesion promoter		Increase the strength of an adhesive bond	Silanes, maleic acid, bis(trimethylsilyl)amine, copper naphthenate, vinyltriethoxysilane, ethylene/acrylic acid; also called tackifiers, primers	May be applied to the substrate or added to the uncured matrix
Antioxidant	0.5-3.0	Inhibits oxidation in order to protect against degradation, especially during processing; major groups are free-radical scavenger or peroxide decomposer	Phenols (Bisphenol A), phosphite esters, some thioethers, aromatic amines, Hindered amine light stabilizer, sulfides; also called stabilizer	Almost all plastics contain some type of stabilizer
Antistatic agent	0.1-1	Minimize development of, or dissipate accumulation of, static charge on surfaces; most are applied as coatings	Quaternary ammonium salts, aliphatic amines, phosphate esters, and ethylene glycols	Most types are hydrophilic and may attract moisture or migrate to water
Biocide	0.001-1	Designed to destroy, deter, or control degradation from harmful organisms; also called antimicrobial	Generally poisonous substances including Preservatives, Insecticide, Fungicide, Herbicide, Bactericide and Disinfectant; such as arsenic compounds, Phenylmercuric acetate (discontinued), organic tin compounds (Tributyl tin oxide), Formalin, Alcohol, phenolics, isothiazolinones; triclosan; chlorinated nitrogen sulfur heterocycles and 10,10' oxybisphenoarsine	Present in small amounts but quite toxic
Blowing agent		Used to create open spaces in polymers and metals, such as for foams	Carbon dioxide, Nitrogen, Pentane, azodicarbonamide, isocyanate, benzene disulphonyl hydrazide, Microballoon; also called foaming agent	The foaming process in irreversible in most solids
Colorant	0.001- 10	Used to give color or opacity	Any Dye or Pigment including azocolorants, cobalt diacetate, Cd, Cr and Pb compounds, zinc sulfide, Zinc oxide, iron oxide, Ultramarine, Titanium dioxide, Al and Cu metallic powders	Fluorescent materials and dyes may migrate whereas inorganic compounds usually do not
Dispersant		Aids in the separation and suspension of small particles in a bulk medium	Paints may include borates, silicates, polyphosphates, and polyacrylates; anionic Surfactants used in soaps and detergents include organic sulfates and phosphates and salt of carboxylic acids; nonionic surfactants (Emulsifiers) used in latex paints are ethoxylated alkyl alcohols and alkyl phenols.	Some have a tendency to produce foam
Filler	0-50	Change the mechanical and optical properties, while producing a less expensive product; also called bulking agents	Talc, Kaolin, Chalk, Barium sulfate, Glass bead, Glass fiber, Carbon black, Carbon fiber, metal powder, wood powder, silicious earth	Most polymers contain fillers. High levels can protect against UV rays
Flame retardant	1-30	Used to minimize burning	Most commonly used are brominated and chlorinated paraffins, then Aluminum hydroxide, Antimony trioxide and various Organophosphates	Non-chlorinated organophosphates are safer but do not work as well
Heat stabilizer	0.3-5	Minimizes degradation due to heat exposure; also called thermal stabilizer	Formerly derivatives of Lead, Tin and Cadmium were used. Alternatives are barium/zinc mixtures and Calcium stearates	Primarily used in PVC which is prone to thermal degradation
Impact modifier	10-40	Improved toughness and resistance to damage	Usually an elastomeric copolymer such as Butadiene, Styrene, etc.	Chlorinated polyethylene is used for PVC
Light stabilizer	0.05-3	Protects against UV damage by absorbing or quenching UV rays; also called UV stabilizer	HALS (of ten used n polyolefins, polyethylene, polyurethane), UV blockers (such as benzotriazoles) and quenchers (usually a dye)	Normally only used in products designed for outdoor use
Lubricant	0.1-3	Used to assist in the process of forming/molding plastic; also called Release agents and slip agents	PFASs (hazardous), Paraffin wax, wax ester, metal stearates (Zinc stearate, etc.), fatty acid amides (oleamide, erucamide, etc.)
Plasticizer	10-70	Provide flexibility, durability and stretchability while reducing melt flow	Phthalates are most common, followed by adipate ester, citrate ester, and chlorinated paraffins	PVCs use the most plasticizers followed by cellulose acetate. Phthalates leach out with time and are considered carcinogenic
Siccative			also called drier or drying agent
Size
Thickener		Used to prevent the sagging of a coating	Also called anti-sag agent

Synonyms and Related Terms

additives (pl.); modifier; admixture; Additive (Deut.); additif (Fr.); aditivo (Port.)

Resources and Citations

• John N. Hahladakis, Costas A. Velis, Roland Weber, Eleni Iacovidou, Phil Purnell, 'An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling, Journal of Hazardous Materials, V.344 (2018). link
• Monona Rossol, 'Water-Based Latex Paints' in handout for NYCOSH webinar on paints, 2019.
• Theodore J. Reinhart, 'Glossary of Terms', '2019 NYCOSH webinar on paints handout, Engineered Plastics, ASM International, 1988
• ASTM, "Standard Terminology Relating to Paint, Varnish, Lacquer and Related Products", Annual Book of ASTM Standards, Section 6, Paints, Related Coatings and Aromatics, ASTM, D16, 7-Jan, Jul-96
• Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982
• Art and Architecture Thesaurus Online, http://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000
• Wikipedia: http://en.wikipedia.org/wiki/Additive (Accessed Feb. 2, 2006)
• Wikipedia: |Plastic Additives (Accessed June 2023)