Stabilization of Plastics

Polymeric films used in greenhouse and mulch film applications have been a subject of great interest to additive manufacturers, film processors, and researchers for over 25 years [29-34]. 

Ni quenchers first compounds used for greenhouse stabilization in combination with UV absorbers 

Polymeric HALS have superior UV stability have disadvantage of possibility of deactivation with acidic pesticides 

In Florida the performance of Ni quenchers may vary depending on their chemical structure and their combinations with UV absorbers, as well as their level of additions in the formnlations. Table 5.5 shows some Ni quenchers, such as Ni2, that have superior performance even when the others are combined with benzophenone-type UV absorbers. 

Light Stability of Greenhouse Films Exposed in Near-Equatorial Regions 

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Table 5-5 Effects of elevated temperature and chemical agents on stability of plastics...

Henninghausen G, Lange P. 1980. Immunotoxic effects of dialkyltins used for stabilization of plastics. Pol J Pharmacol Pharm 32 119-124. 

Philo M R, Jickells S M, Damant A P and Castle L, 1994, Stability of plastics monomers in food-simulating liquids under European Union migration test conditions. J. Agric. Food. Chem. 42,1497-1501. 

ASTM D 4674-89 (1989) Accelerated testing for color stability of plastics exposed to indoor fluorescent lighting and window-filtered daylight. 

STORAGE STABILITY OF PLASTIC-DERIVED DIESEL FUEL... 

Standard Practice for Accelerated Testing for Color Stability of Plastics Exposed to Indoor Fluorescent Lighting and Widow-Filtered Daylight, ASTM Designation D 4674-A689. 

Argon, A. S. Stability of Plastic Deformation, in The Inhomogeneity of Plastic Deformation, Metals Park, Ohio, ASM, 1973, p. 161... 

Table 3 Stability of plasticizers in hot-melt extruded HPC films processed at 180°C as a function of storage conditions (n — 6)...

Recommended Cycling Temperatures for Testing P Stability of Plastic Fat Products... 

Gugumus, F. Stabilization of plastics against thermal oxidation. In Oxidation Inhibition of Organic Materials, Klemchuk, P., Pospisil, J., Eds. CRC Press Boca Raton, 1990 Vol. 1, 61-172. 

Stabilisers increase the stability of plastic either during processing or during the moulded life of the material. Heat stabilisers are essential to PVC, taking up any released hydrochloric acid from product decomposition. The broad categories of stabiliser used are found under Polyvinyl chloride above. Stabilisers are frequently used to combat the combined effects of heat and light. 

Fortunately, no such conflict of interests arises with diphenylamines 9 and phenylenediamines lla-d. Various DPA were tested and approved as AO not only in rubbers, their traditional application field the physically persistent 9b and 9a have also been approved for stabilization of plastics in contact with nonfatty food [307]. Derivatives of PD are the most versatile nowadays as mbber antidegradants. Oral administration to experimental animals indicated some danger of necrosis of skeletal and/or cardiac muscles [311]. This has been explained by in vivo oxidation of PD lid into quinone imine by muscle mitochondria and establishing an alternative pathway for electron transport in the physiological respiratory chain. 

This standard considers the stability of plastics when they are exposed outdoors. The relative durability of plastics in outdoor use can be very different depending on the location of the exposure because of the differences in UV radiation, wetness, temperature, pollutants (acid rains, for example), and many other factors. Hence, exposure in several locations with different climates that represent a broad range of anticipated service conditions are recommended by this ASTM. Still, because of year-to-year climatological variations, resnlts of exposure in 1 year cannot be used to predict the absolute rate at which a material degrades. Therefore, several years of repeated exposure to get an average test result for a given location is recommended. 

Glass Filler - Glass fillers are a widely used family of fillers in the form of beads, hollow spheres, flakes, or milled particles. They increase dimensional stability, chemical resistance, moisture resistance, and thermal stability of plastics. 

Antioxidants improve the stability of plastics to oxygen. Such substances as oxygen acceptors (fine-dispersed metals and oxides of transient metals of lower valence) break the chains of radical reactions on thermo-oxidative destruction of pol miers or destroy intermediate products of these reactions. 

FIGURE 1.34 Time-temperature zones indicating thermal stability of plastics (see Table 1.13). (Adapted from Anon. 1968. Plastics World, 26(3), 30.)... 

Development of electrically conducting polymers that can be processed as thermoplastics and possess the advantageous mechanical behavior and corrosion stability of plastics would open up entirely new fields of applications. Some of the many applications in which electrically conducting polymers would find a large market are cables and conducting electricity, wall papers that allow electrical heating, materials for antistatic equipment, and conducting fabrics. 

Fay JJ. Additives for the stabilization of plastics building and construction applications. ANTEC 2008, conference presentation. Ciba Corp. 2008. 

On the other hand, when a part is subjected to a permanent deformation (Figure 2.12 b), a gradual decrease of stress is observed due to stress relaxation. Creep and stress relaxation often act together and strongly influence the dimensional stability of plastics-based products they are of interest to engineers in any application where the material must sustain stress or strain over a long period of time. 

The dimensional stability of plastic structural components - especially when integrated with other parts to make up components or a system, and in particular in combination with different materials (steel, aluminum, magnesium, ceramic, fiber composites) - is often a factor of central importance in technical applications (Fig. 75) [16]. 

The parameters that influence the dimensional stability of plastic parts include mass distributions, grain structure, reirtforcing materials, processing conditions, moisture content (swelling) and temperature variations during operation. 

Argon, A. S. (1973) Stability of plastic deformation, in The Homogeneity of Plastic Deformation, edited by Reed-Hill, R. E., Metals Park, OH ASM, pp. 161-189. 

Table 10-1. Effects of Elevated Temperature and Chemical Agents on Stability of Plastics (a Rating of "1" Equals Greatest Stability). 

Polyvinylchloride is the prime example of a polymer whieh produces the degradation product, HCl, which is potentially dangerous to the stability of plasticizers. Sinee plasticizers are esters they may undergo hydrolysis assisted by acids. Figure 10.41 shows acid number of plasticizers in simple PVC formulation heated at 170°C for 90 min. The rate of hydrolysis depends on plasticizer type (both acid and alcohol seem important). 

The loss of plasticizer may be accelerated by the decomposition of cellulose nitrate which produces nitrous oxides that then combine with water to form nitrous and nitric acids. Acids affect the stability of plasticizers and their interaction with the polymer. 

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