The structure of lead stabilizers. 3: Reaction products with HCl

The reaction of HCl with stabilizers such as dibasic lead phthalate, tribasic lead sulfate, and dibasic lead phosphite leads to a series of previously uncharacterized chlorinated derivatives. These compounds exhibit an interesting and hitherto unknown chemistry. Some are heat stabilizers in their own regard.     

The NMR spectra of lead stabilizers

High resolution proton and ¹³C NMR spectra of lead-based heat stabilizers and their reaction products, obtained using the magic angle spinning technique, support structural assignments inferred from IR spectra. These demonstrate that lead stabilizers are unique compounds, rather than the double salts of lead oxide found in textbooks.     

稀土化合物作为高分子材料热稳定剂的研究进展

稀土化合物作为高分子热稳定剂具有优良的长期热稳定性,无毒环保,与其它热稳定剂具有协同作用。本文主要介绍了稀土热稳定剂在聚氯乙烯、硅橡胶和天然橡胶上的应用,概述了稀土与其它热稳定剂的协同作用与机理,并对稀土热稳定剂的应用和研究前景进行了展望。     

Low extractable lead stabilizers

Although lead stabilizers are less soluble and form less soluble reaction products than other types, because of the nature of the U.S. EPA Toxic Characteristic Leaching Procedure extraction, it is often difficult to certify lead-stabilized scrap as nonhazardous waste. It has been found that lead stabilizers can be blended with additives that lead to reaction products that appear to be extremely insoluble complex phosphates. The results are lead-stabilized compositions with significantly reduced lead extractability.     

The structure of lead stabilizers. 2: Basic salts of inorganic acids

FTIR and NMR measurements were used to infer structural formulas for the heat stabilizers dibasic lead phosphite, tribasic and tetrabasic lead sulfates, and basic lead carbonate. These compounds are not the customarily written double salts of lead oxide or hydroxide, but distinct species capable of rapid HCI neutralization.     

Photooxidative Destruction and Stabilization of Polycaproamide by Bis-Aroilenbenzimidazole Derivatives

Abstract

Some derivatives of bis-naphthoylenebenzimidazoles have been studied as light stabilizers of polyamide-6 and polyethylene terephtalate. These stabilizers are stable in the melts of these polymers for long times at 260–280°.

The light-stabilizing effect of compounds studied is discussed.     

True stabilization: A mechanism for the behavior of lead compounds and other primary stabilizers against PVC thermal dehydrochlorination

A free-radical mechanism by which lead compounds are thought to inhibit thermal dehydrochlorination of polyvinyl chloride (PVC) is described. This mechanism is called “true stabilization” in order to distinguish it from simple hydrogen chloride (HCl) scavenging, which is a well-known and sometimes important function of all primary stabilizers used in PVC. In true stabilization, it is thought that stearate or other aliphatic carboxylate groups (initially from lubricants) react with reservoirs of basic lead compound such as the carbonates, dibasic lead phosphite, the phthalates, or the sulfates, to give mobile carboxylates of lead. These latter salts then react with chlorine atoms released by the hot PVC, giving chlorides of lead and aliphatic carboxylate free-radicals. Hence the chlorine atoms are trapped and unable to propagate free-radical dehydrochlorination. Also it is thought that the aliphatic carboxylate free-radicals esterify PVC molecules at methylenic carbon atoms (from which hydrogen atoms have been removed by chlorine atoms giving HCl and free-radical sites in the polymer chain). Thus, unpaired electrons on the carboxylate free-radicals and on these methylenic carbon atoms in the PVC molecules are paired, so that the neighboring chlorine atoms in polymer chloromethylenic groups are stabilized. Hence loss of chlorine atoms in the free-radical dehydrochlorination of PVC is prevented. The pendant aliphatic carboxylate groups dissociate from the PVC molecules taking chloromethylenic hydrogen atoms to form acid molecules, and leaving chlorine atoms in relatively stable vinyl type groups. The aliphatic carboxylic acids react with more of the basic lead compound reservoir, giving mobile carboxylates of lead which can enter further reactions as just described. Thus, the true stabilizing mechanism is continuous and cyclic, while the reservoir of basic lead is available, and the PVC thermal dehydrochlorination will be retarded to almost negligible rates in favorable circumstances. It is thought that the behaviors of metal soaps and of organo-tin stabilizers may be encompassed within the general true stabilization concepts of free-radical exchanges and PVC esterifications described above. In these ways they also would retard PVC thermal dehydrochlorination. However, they are neutral compounds and have no basic reservoir which can react with carboxylic acids in the manner described above for lead stabilizers. Hence they are not able to confer long term stability on PVC in the way that basic lead stabilizing regimes do.     

The importance of lead and cadmium stabilizers to the vinyl compounder

The inorganic salts of lead were the first materials proposed for use as vinyl stabilizers, and even though newer families of materials have been developed, lead salts continue to fill an important role in vinyl stabilization. They are irreplaceable in the manufacture of electrical insulation for high-temperature use and are still considered among the most powerful of stabilizer types. Cadmium organic salts, as part of complex barium-cadmium-zinc systems, have proven indispensible in the manufacture of vinyl compounds requiring a combination of outstanding heat and light stability. The move in Detroit towards the manufacture of lighter, more fuel-efficient automobiles would be difficult without the use of plastics, including some of the more sophisticated vinyl compounds stabilized with barium cadmium-zinc combinations.     

Recent Advances in Amphiphilic Polymers as the Stabilizers of Colloidal Gold Nanoparticles

Gold nanoparticles (AuNPs) exhibit high catalytic activity as catalysts and have potential applications in biomedicine. To prevent the aggregation of colloidal AuNPs, the stabilizers including organic small molecules, organic ligands, inorganic ligands, and polymers, are necessary to be added in the synthesis of colloidal AuNPs. Among these stabilizers, amphiphilic polymers have attracted significant attention from scientists in the development of polymerization and modification methods. To date, numerous efforts are employed to develop amphiphilic polymers as the stabilizers of colloidal AuNPs but are not well‐summarized yet. In this review, four parts (amphiphilic linear polymers, amphiphilic graft polymers, amphiphilic hyperbranched polymers, and amphiphilic dendrimers) according to the polymer architectures will be discussed. Comprehensive understanding of amphiphilic polymers that are used for stabilizing colloidal AuNPs is provided.     

Recent Advances in Organotin Polymers

The science and technology of organotin polymers are based on the properties of organotin compounds which have surprisingly diverse applications, including use as stabilizers for vinyl chloride and other olefm polymers, as industrial catalysts, as industrial and agricultural biocides, and as antifouling and wood-preserving agents. In keeping with the expanding use of organotin compounds, the worldwide production of organotin compounds has risen dramatically from less than 50 tons/yr in 1950 to over 25,000 tonslyr in 1975 [1]. The chemis-try of organotin compounds, including the preparative methods, properties, chemical reactions, and uses, has been reviewed in several recent monographs and symposia proceedings [1–5]     

Stabilization of ABS with bound synergistic stabilizers added as masterbatches

ABS masterbatch concentrates in antioxidants and UV stabilizers were added as conventional additives for normal ABS. The thermal and photo-oxidative performance of these polymers were compared with that of the commercial ABS and additives by measurement of carbonyl index and embrittlement times. From the result obtained, it is concluded that the addition of these additives in the form of masterbatches appears to be a better practical way of incorporating antioxidants and UV stabilizers into ABS simply by dilution of ABS, as these give thermal and light-stabilizing effects that cannot be achieved by stabilizers added in a conventional way. The bound stabilizers are resistant to leaching and chemical extraction.     

PVC新型热稳定剂的研究现状

随着环保意识的逐渐加强，传统的PVC热稳定剂如铅盐类稳定剂已受到了一定的限制，相应地开发出了一系列新型的PVC热稳定剂，包括稀土类、有机锑类(Ca／Zn)复合类和水滑石类热稳定剂。这些热稳定剂大多无毒，热稳定效果良好，价格适中，越来越受到人们的重视，将逐渐代替传统的热稳定剂，成为PVC热稳定剂中的重要组成部分。     

Macromolecular stabilizers for polymers

Inherent chemical activity, physical persistence and good compatibility are factors determining the efficiency of a stabilizer observed during the degradation of amorphous and crystalline synthetic polymers. Synthesis of macromolecular stabilizers is one of the ways used to solve the problem of physical persistency of stabilizers under severe aggressive environmental attacks on polymers. General types of macromolecular stabilizers, routes to their synthesis and characteristic examples of macromolecular antioxidants, UV absorbers, hindered amine light stabilizers, flame retarders and biostabilizers, as well as of polyfunctional systems are given. Problems connected with the use of macromolecular stabilizers are mentioned.     

Update: lead stabilizers

As it stands today, the outlook for the lead stabilizer industry couldn't be better. There are several reasons why we feel this is so. One reason is that governmental regulations have been known to the industry for several years. Because of this, suppliers have been very successful in helping consumers meet existing regulations through education, training, and improved handling technology. Also, we are aware of no new or pending legislation that would place additional restrictions on lead. Other reasons for optimism include increased cost advantages when compared to other types of stabilizers available and the potential from new application areas. My intent is to review what the industry has done to promote customer compliance regarding governmental regulations and to elaborate on reasons for our optimistic outlook concerning the future of the lead stabilizer industry.     

无铅无乙基硫脲氯醚橡胶硫化体系的开发

由于健康和环境方面的原因,在欧洲,氯醚橡胶是不允许使用含铅和乙基硫脲的硫化体系的。因此,研发无铅无乙基硫脲的硫化体系迫在眉睫。通过使用特殊的商业化的材料,可使氯醚混炼胶的物理机械性能、耐热老化性、耐燃油性能、贮存稳定性及成本均达到或超过含铅硫化体系的氯醚混炼胶。新研发的无铅无乙基硫脲硫化体系氯醚胶的贮存期至少可以达到7周。同时,这些无铅无乙基硫脲硫化体系氯醚胶的材料成本与含铅硫化体系的相当。     

Lead stabilizer dispersion in PVC

As a major consumer of lead stabilizers used in PVC wire and cable compounds, Western Electric raw material inspection personnel have seen a decline of lead stabilizer dispersion quality. For this reason, the dispersion of lead stabilizer is of major concern to us. Marginally dispersed stabilizers cause an excessive collection of lead compound on the extruder screen pack and eventual rupture of the screen. Marginal dispersion detracts from extrusion smoothness of high-speed, thin-wall wire insulation. Stabilizer manufacturers have acknowledged that dustless versions of their products are more difficult to disperse. Lead suppliers must meet OSHA regulations that limit employees' exposure to inorganic lead compounds. They are using different approaches that are producing a proliferation of packages as well as stabilizer surface treatments. Dispersion quality has varied from supplier to supplier and from lot to lot. Obviously, compounders find it difficult to agree on a solution to the problem. The use of bulk returnable air pallets and standard non-treated stabilizer would satisfy dust-level requirements, eliminate the need for additive treatment, and solve potential bag disposal restrictions.     

Stabilization of vinyl chloride/vinylidene chloride copolymers using N‐substituted maleimides

As a consequence of their excellent barrier properties, vinyl chloride/vinylidene chloride copolymers have long been prominent in the flexible packaging market. While these polymers possess a number of superior characteristics, they tend to undergo thermally induced degradative dehydrochlorination at process temperatures. This degradation must be controlled to permit processing of the polymers. Three series of N‐substituted maleimides (N‐alkyl‐, N‐aralkyl‐, and N‐aryl‐) have been synthesized, characterized spectroscopically, and evaluated as potential stabilizers for a standard vinyl chloride/vinylidene chloride (85 wt%) copolymer. As surface blends with the polymer, these compounds are ineffective as stabilizers. However, significant stabilization may be achieved by pretreatment of the polymer with N‐substituted maleimides. The most effective stabilization of the polymer is afforded by N‐aralkyl‐ or N‐arylmaleimides, most notably, N‐benzylmaleimide and N‐(p‐methoxyphenyl)maleimide. J. VINYL. ADDIT. TECHNOL. 12:88–97, 2006. © 2006 Society of Plastics Engineers.     

Gamma-radiation stabilization of polypropylene

Especially synthesized compounds, together with conventional antioxi-dants, were evaluated as radiation stabilizers of isotactic polypropylene. Electron spin resonance (ESR) determinations of free radical populations in stabilized and unstabilized samples were carried out after irradiation and at periods of up to 460 h. The same samples were mechanically tested and a correlation was found to exist between the concentration of trapped peroxy radicals and the radiation deterioration in the polymer. Post-irradiation effects were evaluated using accelerated aging at 70°C and carbonyl index determinations at periods of up to 110 days indicated that some of the stabilizers examined are efficient inhibitors of post-irradiation oxidation. The results are discussed in the light of the free radical mechanism of the radiation-induced auto-oxidative degradation of polymers.     

New developments in speciality polymers: polymeric stabilizers

Many new speciality polymers have been developed in the last few years. In this paper polymeric stabilizers (antioxidants, flame retardants and ultraviolet stabilizers) will be discussed. Polymeric antioxidants of the hindered-phenol type, copolymers of 2,6-ditertiarybutyl-4-vinyl(or isopropenyl)phenol with styrene, methyl methacrylate, or more importantly butadiene or isoprene have been prepared; hydrogenation of the latter copolymers gave copolymers of the two polymerizable phenolic antioxidants with ethylene or ethylene/propylene. The polymeric antioxidants have been blended with diene polymers and selected polyolefins and have improved the long-term oxidative stability of these polymers. Polymeric flame retardants have been prepared by copolymerizing styrene and/or acrylonitrile with acrylates and methacrylates of aliphatic bromine-containing alcohols or bromine-containing phenols. Polymers with polymer-bound flame retardants have a higher limiting oxygen index compared with the original polymer. A new class of polymerizable ultraviolet stabilizers has also been developed; these stabilizers are styryl, α-methylstyryl, acryloyl and methacryloyl derivatives of 2(2-hydroxyphenyl)2H-benzotriazoles. These monomers have been copolymerized with styrene, acrylates and methacrylates. 2(2-Hydroxyphenyl)2H-benzotriazoles substituted in the 4 position of the benzotriazole ring with hydroxyl, acetoxy or carboxyl groups suitable for incorporation into polyesters, polycarbonates, polyamides and epoxy resins have also been synthesized. All 2(2-hydroxyphenyl)2H-benzotriazole ultraviolet absorbers and the polymers into which they are incorporated have high light absorbency with γ_max between 330 and 350 nm and extinction coefficients in some cases as high as 4.5 × 10⁴ 1 mol^?1 cm^?1.     

反应型聚合物稳定剂的研究进展

研究反应型稳定剂是提高聚合物耐热性和耐萃取性的一种发展趋势。按反应性基团的不同,反应型稳定剂可分为乙烯基类、丙烯酰基和其他类型等几种。本文分别对上述几类稳定剂的合成和应用进行了概述,并详细介绍了其中的一些商业化品种。