Polystyrene heat stabilizers

Nickel dialkyldithiocarbamates stabili2e vulcani2ates of epichlorhydrinethylene oxide against heat aging (178). Nickel dibutyldithiocarbamate [56377-13-0] is used as an oxidation inhibitor in synthetic elastomers. Nickel chelates of substituted acetylacetonates are flame retardants for epoxy resins (179). Nickel dicycloalkyldithiophosphinates have been proposed as flame-retardant additives for polystyrene (180—182) (see Flame retardants Heat stabilizers). 

A high-impact polystyrene (polystyrene SBR blend) may have seven times the impact strength of ordinary polystyrene, but about half the tensile strength, a lower hardness and a softening point some 15°C lower. Because of the rubber content there may be a reduction in light and heat stability and stabilisers are normally incorporated. 

P.Y.17 is also frequently used in polyolefins, sometimes in the form of pigment preparations. Its heat stability in these media was said to be about 220 to 240°C, but must now, as a result of the detected thermal decomposition of diarylide yellow pigments in plastics, be limited to 200°C. This tendency to decompose excludes P.Y.17 from recommendation for use in polystyrene, in which the pigment largely dissolves under the processing conditions. The same is true for ABS. 

In polystyrene, polymethacrylate, unsaturated polyester resins, or similar media, P.R.31 affords highly transparent colorations of medium red shades, which are used as automobile tail lights and for other signalling purposes. Its heat stability in... 

P.O.72 is as well suitable for the application in polystyrene and ABS. Colorations of PS in 1/3 SD, requiring only 0.15% pigment, exhibit a heat stability of 280°C, colorations of ABS are stable up to 290°C. In these media the lightfastness equals step 8 on the Blue Scale. Pigment concentration of less than 0.1% in poly-oxymethylen (POM, polyacetales) may lead to coating of the manufacturing equipment (see plate out, Sec. 1.6.4.1). 

In plasticized PVC, P.R.242 shows good fastness to bleeding and provides average tinctorial strength. 1/3 SD colorations containing 5% TiOz require 1.1% pigment. Good heat stability makes P.R.242 a suitable candidate for use in polystyrene, ABS, PMMA, and polyester. 

A second example is the yellow pyrazolone salt, Pigment Yellow 191 [129423-54-7]. It is the calcium salt of diazotized 2-amino-4-chloro-5-methyl-benzenesulfonic acid coupled with 3-methyl-1-[3 —sulfophenyl]-5-pyrazolone and provides a reddish yellow pigment for use in plastics applications. It shows very good heat stability and excellent resistance to nonpolar solvents and commonly used plasticizers (qv). It finds applications in high density polyethylene, polystyrene, and ABS, and shows satisfactory lightfastness. 

Other Plastics Uses. The plasticizer range alcohols have a number of other uses in plastics liexanol and 2-ethylliexanol are used as part of the catalyst system in the polymerization of acrylates, ethylene, and propylene (55) the peroxydicarbonate of 2-ethylliexanol is utilized as a polymerization initiator for vinyl chloride various trialkyl phosphites find usage as heat and light stabilizers for plastics organotin derivatives are used as heat stabilizers for PVC octanol improves the compatibility of calcium carbonate filler in various plastics 2-ethylliexanol is used to make expanded polystyrene beads (56) and acrylate esters serve as pressure sensitive adhesives. 

Organophosphites are secondary antioxidants which reduce hydroperoxides to alcohols. They inhibit the discolouration reaction experienced by phenolics. Tris-nonyl phenyl phosphite (TNPP) is the most commonly used. The disadvantage of phosphates is their high hygroscopicity. Thioesters act as secondary antioxidants by destroying hydroperoxides to form stable sulphur derivatives. In addition, thioesters impart high heat stability to polyolefins, polystyrene and its copolymers. The m or disadvantage of thioesters is their unpleasant odour which is transferred to the host polymer. 

The optical properties, clarity and gloss, are also improved and biaxially oriented polystyrene and polypropylene films are used for envelope windows and overwraps. Biaxially oriented polyvinylidene chloride film is also used for food packaging in view of its good mechanical and optical properties, but for economic reasons it is only used if its low permeability to gases, especially oxygen, is required. The electrical properties are improved by biaxial orientation and the applications of polyester, polycarbonate and polypropylene films in capacitors are expected to show a rapid growth. In these electrical applications crystalline films are always annealed in order to improve the dimensional heat stability. 

Diatomaceous earth heat resistance enhancer, polystyrene Lead phosphate, dibasic heat resistance modifier, ABS resins N-Phenylmaleimide heat stabilizer, PVC Dimethyltin dichloride heat storage medium Sodium sulfate heat transfer agent... 

Recently, impact modifiers have been developed for plastics other than PVC. Polybutylene and other olefinic thermoplastic elastomers, for example, are being used to enhance the processability, toughness, and heat stability of polypropylene film. Hydroxy-terminated polyethers are being used to increase the impact resistance of polystyrene. Other conunon applications are polycarbonate, polyurethane, thermoplastic polyester, epoxy, and polysulfone. 

Metallic soaps and salts of stearic acid and other organic acids are used both as lubricants and as auxiliary heat stabilizers. Metallic stearates are the most widely used lubricants. They are predominantly used in PVC, but also find use in polyolefins, ABS, polyesters, and phenolics. The primary disadvantage of metallic stearates is their lack of clarity. Calcium stearate, the most common metallic stearate, is primarily used as an internal lubricant, but in PVC applications it provides external lubrication and mold-release characteristics while also acting as a heat stabilizer. In addition to PVC, the calcium sterarates go into polypropylene, polystyrene, and ABS. Zinc stearates are used in crystal and impact polystyrene, ABS, and phenolics. 

Quinacridone pigments are available in orange, red, and violet. They have good light fastness, excellent bleed and chemical resistance, and adequate heat stability for most plastics. However, they are high in cost. They perform best in polystyrene and acrylic at lower temperatures. They are not recommended for nylon. 

Recent developments include systems with better colour fidelity and handling properties. Dover s Doverphos HiPure 4 and 4-HR are high-purity tris-nonylphenyl phosphite (TNPP) processing and heat stabilizers, claimed to reduce overall costs. With 0.1% residual nonyl phenol, they are FDA-approved for food-contact applications and also used in medicals, colour-critical polyolefins, and styrenic block copolymers. They are effective also in acrylics, elastomers, nylon, polycarbonate, polyurethanes, polystyrene. PVC. ABS, and PET. 

P.Y. 181 represents a reddish yellow pigment with excellent heat stability and lightfastness. It is especially suitable for polymers that are processed at higher temperatures. P.Y. 181 plays a role in the coloration of such plastics as polyacetals, polystyrene or polyester, as well as in spin dyed viscose rayon and viscose cellulose. 

Zuev and co-workers [16] also studied the isothermal degradation at 600 °C of a series of parasubstituted polystyrenes with electron donating (CH, NH ) and electron attracting (NO, Cl, Br) substituents. The temperature ranges over which degradation occurred were determined and the heat stability of these polymers compared with those of conventional PS. Thermal degradation was found to involve random chain scission and depolymerisation and heat stability was found to depend on the electronic nature of the substituents and the possible stabilisation of macroradicals formed upon chain scission. 

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