The antistatic additive market is served by fewer than 50 suppliers. The major suppliers include Akzo, Witco, Henkel, Elf Atochem, Kao, and Clariant. Table 4.5 lists some of the more prominent suppliers and the types of antistatic agents offered.
TABLE 4.5 Selected Suppliers of Antistatic Agents
Supplier Quats* Amines Fatty acid esters Other†
Bayer — — — ×
Ciba Specialty Chemicals — — — ×
Clariant — × × —
Cytec Industries × — — —
Elf Atochem — — — ×
Henkel Corporation — — × —
ICI Americas — × — —
Kao Corporation — × × —
Lion Akzo × — — —
Lonza × — × —
NOF Corp. — — × —
Sanyo Chemical × — — —
Witco × × × —
*Quaternary ammonium compounds.
†”Other” category includes aliphatic sulfonates, fatty amides, and polymeric antistats.
4.5.3 Trends and forecasts
Continuing increases are expected in the markets for electronic compo- nents, devices, and equipment. Plant modernization activities will increase requirements for automated production machinery. Improvement in communication will continue to promote sales of items such as facsimile machines, personal computers, and cellular telephones. This will provide more opportunities for antistatic agents for static and electromagnetic interference control. Globally antistatic agents are expected to grow at a rate of 5 to 6%/year over the next 5 years.
Biocides are additives that impart protection against mold, mildew, fungi, and bacterial growth to materials. Without biocides, polymeric materials in the proper conditions can experience surface growth, development of spores causing allergic reactions, unpleasant odors, staining, embrittlement, and premature product failure. It is impor- tant to note that the biocide protects the material, not the user of the final product.
In general, in order for mold, mildew, and bacterial growth to devel- op, the end product must be in an environment that includes warmth, moisture, and food. Specifically, if the environment includes soil where microbes and bacteria abound, protection against bacterial
growth is needed. If the end product has a water or moist environ- ment, protection from fungi may be the most important feature. Environmental conditions overlap and many biocides are effective over a broad range.
Biocides, also referred to as antimicrobials, preservatives, fungicides, mildewcides, or bactericides, include several types of materials that dif- fer in toxicity. OBPA (10, 10′-oxybisphenoxarsine) is the most active preservative of those commonly used for plastics. Amine-neutralized phosphate and zinc-OMADINE (zinc 2-pyridinethianol-1-oxide) have a lower activity level but are also effective. In the United States all bio- cides are considered pesticides and must be registered for specific appli- cations with the U.S. Environmental Protection Agency (EPA).
The effectiveness of a biocide depends on its ability to migrate to the surface of the product where microbial attack first occurs. Most bio- cides are carried in plasticizers, commonly epoxidized soybean oil or diisodecyl phthalate, which are highly mobile and migrate throughout the end product. This mobility results in the gradual leaching of the additive. If significant leaching occurs, the product will be left unpro- tected. The proper balance between the rates of migration and leach- ing determines the durability of protection.
The majority of biocide additives are used in flexible PVC. The remaining portion is used in polyurethane foam and other resins. PVC applications using biocides include flooring, garden hoses, pool liners, and wall coverings, among others.
The use level of biocide additives depends on the efficacy of the active ingredient. OBPA, the most active, requires approximately
0.04% concentration in the final product. Less active ingredients, such as n-(trichloro-methylthio) phthalimide, require a loading of 1.0% in the final compound to achieve a similar level of protection.
Biocides are generally formulated with a carrier into concentrations of 2 to 10% active ingredient. They are available to plastics converters, processors, and other users in powder, liquid, or solid pellet form. The carrier, as noted previously, is usually a plasticizer, but it can also be a resin concentrate such as PVC/PVA (polyvinyl acetate) copolymer or polystyrene. For example, OBPA, the most common biocide active ingredient, is typically purchased as a dispersion in a plasticizer at a concentration of 2% active ingredient.
Of the hundreds of chemicals that are effective as biocides, only a few are used in plastic applications. After OBPA, the most common group of active ingredients are 2-n-octyl-4-isothiazolin-3-one, 4,
5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), zinc OMADINE, trichlorophenoxyphenol (TCPP or TRICLOSAN), N trichloromethylthio-
4-cyclohexene-1,2-dicarboximide (CAPTAN), and N-(trichloromethylthio)
There are two tiers of biocide suppliers to the plastics industry: those who sell active ingredients and those who provide formulated prod- ucts, both of which are shown in Table 4.6. The active ingredient man- ufacturer typically does not produce formulated biocides and formulators do not typically synthesize active materials.
The major formulated plastic biocide suppliers are Akcros Chemicals (owned by Akzo) and Morton International. Other suppliers of formu- lated biocide products include Ferro, Huels, Olin, and Microban. Akzo- Nobel, Ciba, and Rohm and Haas are the major suppliers of active ingredients.
Among the industry leaders, Morton International offers one of the broadest ranges of formulated OBPA, TCPP, and isothiazole products.
4.6.3 Trends and forecasts
Biocides for plastics are growing at about 7%/year. OBPA, which cur- rently holds the largest market share of all the biocides, is a mature market, growing at half that rate. Other biocides, such as isothiazolin and TCPP, will grow at a much faster rate than OBPA.
Most of this growth in biocides is attributed to increased consumer awareness. The end-use customers are now demanding that nontradi- tional biocide applications, like door handles, hospital chair rails, gar- den hoses, and blue ice packs, incorporate biocides to “protect” them from germs. Consumers seem, in some cases, to be misinformed about the true function of a biocide since it is intended to protect the plastic,
TABLE 4.6 Selected Suppliers of Active Ingredients and Formulated Biocides for
Plastics not the consumer. Suppliers need to be cautious regarding product claims to avoid misinformation. However, this increased awareness does appear to be a long-term trend and not solely a fad.
4.7 Chemical Blowing Agents
The term blowing agent in the broadest sense denotes an inorganic or organic substance used in polymeric materials to produce a foam structure. There are two major types of blowing agents: physical and chemical.
Physical blowing agents. Physical blowing agents are volatile liquids or compressed gases that change state during processing to form a cel- lular structure within the plastic matrix. The gases or low-boiling liq- uids that are dissolved in the resin, evaporate through the release of pressure or the heat of processing. The compounds themselves do not experience any chemical changes. Cell size is influenced by the pres- sure of the gas, the efficiency of dispersion, melt temperature, and the presence of nucleating agents. The most common gases used are car- bon dioxide, nitrogen, and air. The liquid blowing agents are typically solvents with low boiling points, primarily aliphatic hydrocarbons and their chloro- and fluoro- analogs.
The blowing agents should be soluble in the polymer under reason- ably achievable conditions but excessive solubility is not desirable. The permeability of the gas within the polymer is also significant, as is the volume of gas released per unit weight of agent. This latter measure is called the blowing agent efficiency, and is an important yardstick for all types of materials. Effective blowing agents should yield at least
150 to 200 cm3 of gas (measured at standard temperature and pres- sure) per gram of agent.
Physical blowing agents comprise over 90% of the market. They are heavily used in thermoset foams, especially polyurethanes, polyesters, and epoxies. These additives also have some application in such low- density thermoplastics as polystyrene. Until recently, fluorocarbons had the highest consumption among the liquid physical blowing agents. Because of environmental concerns, the market is shifting to alternative blowing agents, primarily partially halogenated chloroflu- orocarbons.
Chemical blowing agents. Chemical blowing agents (CBAs) are prod- ucts that decompose at high temperature. At least one of the decom- position products is a gas, which expands the plastics material to give a foam structure. The amount and type of the blowing agent influence the density of the finished product and its pore structure. Two types of pore structures are possible: open and closed cell. Closed-cell plastics have discrete, self-contained pores which are roughly spherical. Open- celled plastics contain interconnected pores, allowing gases to pass through voids in the plastic.
Factors that determine the formation of a fine-celled plastic foam with a regular cell structure are the particle size of the blowing agent, disper- sion properties of the plastics processing machine used, decomposition rate of the blowing agent, and the melt viscosity of the resin processed.
CBAs are mainly solid hydrazine derivatives. The gas formation must take place in a temperature range close to the processing tem- perature range of the polymer. In addition, the decomposition products must be compatible with the polymer. Typically, these additives decompose over a relatively narrow temperature range. CBAs can be mixed with the polymer at room temperature, requiring no special pro- cessing equipment. In most operations, they are self-nucleating and are stable under normal storage conditions. In addition, CBAs may be reformulated with such other additives as blowing agent catalysts or nucleating agents. Blowing agent catalysts lower the temperature of decomposition for the CBAs while nucleating agents provide sites for formation of a cell in the foamed plastic.
Blowing agents are used in plastics for several reasons: weight reduction, savings in cost and material, and achievement of new prop- erties. The new properties include insulation against heat or noise, dif- ferent surface appearance, improved stiffness, better quality (removal of sink marks in injection molded parts), and/or improved electrical properties.
CBAs may also be subdivided into two major categories, endother- mic and exothermic. Exothermic blowing agents release energy during decomposition, while endothermic blowing agents require energy dur- ing decomposition. In general, endothermic CBAs generate carbon dioxide as the major gas. Commercially available exothermic types primarily evolve nitrogen gas, sometimes in combination with other gases. Nitrogen is a more efficient expanding gas because of its slower rate of diffusion through polymers compared to carbon dioxide.
Exothermic blowing agents. Once the decomposition of exothermic blowing agents has started, it continues spontaneously until the mate- rial has been exhausted. As a result, parts that are being foamed with this type of agent must be cooled intensely for long periods of time to avoid postexpansion.
Azodicarbonamide (AZ). The most widely used exothermic CBA is azodi- carbonamide. In its pure state, this material is a yellow-orange pow- der, which will decompose at about 390°F. Its decomposition yields 220
cm3/g of gas, which is composed mostly of nitrogen and carbon monox- ide with lesser amounts of carbon dioxide and, under some conditions, ammonia. The solid decomposition products are off-white, which not only serves as an indicator of complete decomposition but also does not normally adversely affect the color of the foamed plastic. Unlike many other CBAs, AZ is not flammable. In addition, it is approved by the FDA for a number of food-packaging uses. AZ can be used in all processes and with most polymers, including PVC, PE, PP, PS, ABS, and modified polyphenylene oxide (PPO).
Modified AZ. Modified AZ systems have been developed which offer improved performance and increase versatility in a wide variety of applications. Each system has a formulated cell nucleation system (usually silica) and gas yield is approximately the same as unmodified AZ. Modified types are also available in several particle size grades.
The simplest form of modified AZ is a paste. It is composed of a plas- ticizer, which forms the liquid phase, and may also contain dispersing agents and catalysts. Its principal field of application is the expansion of PVC plastisols. The agents facilitate the dispersion of the blowing agent when it is stirred into the PVC plastisol, while catalysts lower the decomposition temperature.
Other modified AZs have been developed for the manufacture of integral-skin foams by extrusion and injection molding. These contain additives that modify the usual decomposition process of AZ and sup- press the formation of cyanuric acid, which causes plateout on the sur- faces of molds, dies, and screws. The additives used include zinc oxide and/or silicic acid (a colloidal silica) with a very low water content. The additives also act as nucleating agents, producing a cell structure that is both uniform and fine-celled.
There are also grades that have been flow-treated. This type con- tains an additive to enhance the flowability and dispersability of the powder. These grades are very useful in vinyl plastisols, where com- plete dispersion of the foaming agent is critical to the quality of the final foamed product.
Another method of modifying AZ is to mix it with such other CBAs as those from the sulfonyl hydrazide group. These “auxiliary” blowing agents decompose at lower temperatures than AZ, broadening the decomposition range.
Sulfonyl hydrazides. Sulfonyl hydrazides have been in use as CBAs longer than any other type. The most important sulfonyl hydrazide is
4,4′-oxybis (benzenesulfonyl hydrazide) (OBSH). OBSH is the pre-
ferred CBA for low-temperature applications. It is an ideal choice for the production of LDPE and PVC foamed insulation for wire where it does not interfere with electrical properties. In addition, it is capable
of cross-linking such unsaturated monomers as dienes. Additional applications include PVC plastisols, epoxies, phenolics, and other ther- mosetting resins. Like AZ, it is approved by the FDA for food-packag- ing applications and is odorless, nonstaining, and nontoxic.
Sulfonyl semicarbazides. Sulfonyl semicarbazides are important CBAs for use in high-temperature applications. TSS (p-toluene sulfonyl semicarbazide) is in the form of a cream colored crystalline powder. Its decomposition range is approximately 440 to 450°F with a gas yield of
140 cm3/g, composed mostly of nitrogen and water. TSS is flammable, burning rapidly when ignited and producing a large amount of residue. TSS is used in polymers processed at higher temperatures such as ABS, PPO, polyamide (PA), and HIPS.
Dinitropentamethylene tetramine (DNPT). Dinitropentamethylene tetramine is one of the most widely used CBAs for foamed rubber. Its use is lim- ited in plastics because of its high decomposition temperature and the unpleasant odor of its residue. DNPT is a fine yellow powder that decomposes between 266 and 374°F, producing mainly nitrogen and a solid white residue.
Endothermic blowing agents. Endothermic CBAs are used primarily in the injection molding of foam where the rapid diffusion rate of carbon dioxide gas through the polymers is essential. This allows postfinish- ing of foamed parts right out of the mold without the need for a degassing period. Nucleation of physically foamed materials, especial- ly those used for food packaging, has become a well-established appli- cation area for endothermic CBAs.
Sodium borohydride (NaBH4). Sodium borohydride is an effective endothermic blowing agent because its reaction with water produces
10 to 20 times the amount of gas produced by other CBAs that give off nitrogen. Sodium borohydride must be blended with the polymer to be foamed to prevent reaction with water during storage.
Sodium bicarbonate (NaHCO3). Sodium bicarbonate decomposes between
212 and 284°F giving off CO2 and H2O and forming a sodium carbonate
residue. Its gas yield is 267 cm3/g. At 287°F or higher, decomposition
becomes more rapid, facilitating its use as a blowing agent for such higher-temperature thermoplastics as styrenic polymers.
Polycarbonic acid. Polycarbonic acid decomposes endothermically at approximately 320°F and gives off about 100 cm3/g of carbon dioxide. Further heating will release even more gas. In addition to being used as the primary source of gas for foaming in some applications, this class of materials is frequently used as a nucleating agent for physical foaming agents.
There are fewer than 50 suppliers of primary chemical blowing agents worldwide. Most of the leading companies have built their chemical blowing agent business over at least 20 years of experience.
Many of the chemical blowing agents suppliers sell their complete product line in a single region and export only selected products. There are no suppliers of chemical blowing agent that have a leading position in all three major regions of the world. Many of the major chemical blowing agents producers are located in the Asia/Pacific region. There are a few dozen chemical blowing agent producers in China alone. Due to the poor logistics in China, the shipment of the chemicals is rather costly, so most of the companies there supply locally.
The leading supplier of chemical blowing agents in North America is Uniroyal Chemical. Bayer is the leading supplier of chemical blowing agents in Europe followed by Dong Jin. Asia/Pacific, the largest con- suming region, has numerous suppliers, many selling only in that area of the world. The leading suppliers in this region typically manufac- ture in more than one country. For example, Dong Jin Chemical and Otsuka Chemical have primary manufacturing locations in Korea and Japan, respectively, but also produce in Indonesia through joint ven- ture partnerships. A list of selected major suppliers of chemical blow- ing agents globally by type is shown in Table 4.7.
4.7.3 Trends and forecasts
A major concern for producers of AZ type blowing agents is the short- age of the raw material hydrazine. There are few companies globally that manufacture hydrazine and there is currently an insufficient sup- ply to satisfy market demand. However, many leading suppliers like Bayer, Otsuka, and Dong Jin are planning to expand globally. For example, Bayer is doubling its capacity by the year 2000. Its big advantage over most of the leading suppliers, with the exception of Elf Atochem and Otsuka, is that it is backward integrated into hydrazine. Long term, the global expansion of backward integrated CBA suppli- ers should resolve the hydrazine supply issue.
The annual growth rate globally for chemical blowing agents over the next 5 years is in the 5%/year range.
4.8 Coupling Agents
Coupling agents are additives used in reinforced and filled plastic com- posites to enhance the plastic–filler-reinforcement interface to meet
TABLE 4.7 Selected Suppliers of Chemical Blowing Agents
Supplier AZ* TSS† OBSH‡ DNPT§ Other
Boehringer Ingelheim — — — — —
Dong Jin Chemical × × × × ×
Eiwa Chemical Industry × × × × ×
Elf Atochem × — — — —
Jiangmen Chemical Factory × — — — —
Juhua Group × — — — —
Kum Yang × × × — —
Otsuka Chemical × — — — —
Sankyo Kasei × × × × —
Shanghai Xiangyang Chemical
Industry Factory × — — × —
Toyo Hydrazine Industry × — — — ×
Uniroyal Chemical (Crompton
& Knowles) × × × × —
Yonhua Taiwan Chemical × — — — —
Zhenjiang Chemical Industry
Factory × — — — —
Zhuxixian Chemical Industry
Factory × — — — —
†TSS—p-toluene sulfonyl semicarbazide.
‡OBSH—4,4′-oxybis (benzenesulfonyl hydrazide).
increasingly demanding performance requirements. In general, there is little affinity between inorganic materials used as reinforcements and fillers and the organic matrices in which they are blended. With silicate reinforcements (glass fiber or wollastonite), silane coupling agents act by changing the interface between the dissimilar phases. This results in improved bonding and upgraded mechanical proper- ties. By chemically reacting with the resin and the filler or reinforce- ment components, coupling agents form strong and durable composites. Coupling agents significantly improve mechanical and electrical properties for a wide variety of resins, fillers, and reinforce- ments. In addition, they act to lower composite cost by achieving high- er mineral loading.
Fiberglass reinforcement for plastics is the major end use of coupling agents. Thermoset resins, such as polyester and epoxy, account for approximately 90% of coupling agent consumption. Kaolin clay, wollas- tonite, and glass fiber are the leading fillers or reinforcements chemi- cally treated with coupling agents. Coupling agents are either purchased and applied by the glass fiber or inorganic filler manufactur- er or by the compounder for incorporation into the composite system.
Another important market for silane coupling agents is in the cross- linking of polyolefins. In this market silanes are growing at the expense of organic peroxides. Silanes and titanates, along with several minor product types, make up the coupling agent market.
Silanes. Silanes comprise more than 90% of the plastic coupling agent market. They can be represented chemically by the formula Y—Si(X)3 where X represents a hydrolyzable group such as ethoxy or methoxy and Y is a functional organic group which provides covalent attach- ment to the organic matrix. The coupling agent is initially bonded to the surface hydroxy groups of the inorganic component by the Si(X)3 moiety—either directly or more commonly via its hydrolysis product, Si(OH)3. The Y functional group (amino, methoxy, epoxy, etc.) attaches to the matrix when the silane-treated filler or reinforcement is com- pounded into the plastic, resulting in improved bonding and upgraded mechanical and electrical properties.
Table 4.8 lists four different silane chemistries and their related composite systems.
Titanates. Titanates are used primarily as dispersing aids for fillers in polyolefins to prevent agglomeration. Titanium-based coupling agents react with free protons at the surface of the inorganic material, result- ing in the formation of organic monomolecular layers on the surface. Typically, titanate-treated inorganic fillers or reinforcements are hydrophobic, organophilic, and organofunctional and, therefore, exhib- it enhanced dispersibility and bonding with the polymer matrix. When used in filled polymer systems, titanates claim to improve impact strength, exhibit melt viscosity lower than that of virgin polymer at loadings above 50%, and enhance the maintenance of mechanical properties during aging.
TABLE 4.8 Silane Chemistries and Related Composites
Silane type Resin Filler or reinforcement
Amino Phenolic Alumina
Phenolic Silicon carbide
Epoxy Epoxy Alumina trihydrate
Methacrylate Polyester Mica
Vinyl PVC Clay
Table 4.9 presents a list of selected suppliers of coupling agents. The two leading suppliers in North America are Witco and Dow Corning. Worldwide, Witco is the leading supplier with a strong presence in Europe, in Asia/Pacific (through a distribution agreement), as well as in North America.
4.8.3 Trends and forecasts
The coupling agent market follows the growth of its three major uses: fiberglass reinforced plastics, plastics compounding, and mineral filler pretreatment. The latter two markets, although smaller than the rein- forced polyester area, are leading the growth, which is running at about 6%/year globally.