Processing stabilizers for polyolefins

Selected Novel Trivalent Organophosphorus Processing Stabilizers for Polyolefins... 

Hindered phenols and dialkylhydroxylamines protect plastics against thermal oxidation. Alkylated benzo[b]furane-2(3H)-ones was introduced very recently as a processing stabilizer for polyolefins. 

Ethylidene bis(4,6-di-t-butylphenol), 2,2 -Ethylidenebis(4,6-di-t-butylphenol)i EINECS 252-816-3 Phenol, 2,2 -ethylidenebis(4,6-bis(1,1-dimethyl-ethyl)- Vanox 1290, Antioxidant oxidative inhibitor for polymers process stabilizer for polyolefins stabilizer for PU and PS, Crystals mp 162-164°, Vanderbilt R.T. Co. Inc. 

Sterically hindered phenols are effective long-term and processing stabilizers for polyolefins. 

Poly(hydrosilane)s have been successfully applied as processing stabilizers for organic polymeric materials subject to oxidative degradation. The degradation of polyolefins during processing takes place by a widely accepted... 

Photostabilization processes have not received much attention in the last year other than a multitude of review and specialist industrial articles. These include stabilization of polypropylene fibres, new stabilizer developments, sorting of stabilizers for polyethylene, trends in UV absorbers, hindered piperidines (hindered amine stabilizers (HAS)) for polyacrylics and urethanes, new stabilizers for polyolefins, enhanced service life applications, stabilizer mas-terbatches for polyester, stabilizers for UV cured acrylic overcoats for PVC, ° stabilization of clearcoats and various commercial packages. ... 

Chem. Descrip. Trisnonylphenyl phosphite CAS 26523-78-4 EINECS/ELINCS 247-759-6 Uses Processing stabilizer, heat stabilizer for polyolefins, acrylics, adhesives, elastomers, nylon, PC, PU, PS, PVC, coatings, ABS, and PET, food-contact pkg., m lcal devices, color-critical polyolefins, sfyrene block copolymers... 

Uses Antioxidant, stabilizer for plastics (polyamide, ABS, PP, POM, PU, PVC, PS), food-grade polymers, rubber, latex, adhesives, sol n. and emulsion polymers, cellulosics, fats, oils, and paraffin wax polymerization Inhibitor In chemical processes antidegradant for polyolefins and coatings antioxidant in food-contact rubber articles for repeated use in food-pkg. adhesives... 

Uses Color and m.w. stabilizer, antioxidant, melt flow aid for polymer processing (polyolefins, polyesters, elastomers, styrenics, engineering thermoplastics), adhesives, coatings antioxidant, UV stabilizer for polyolefins, food-grade polymers Regulatory FDA 21CFR 178.2010 Manuf./Distrib. Aldrich http //www.sigma-aidrich.com, GE Spec. http //www.ge.com/speciaitychemicais Trade Name Synonyms AO-2 f[Ciba Spec. Chems./Plastic Addit. http //www.cibasc.com]-, Doverphos S-680 [Dover http //www.doverchem.com]-, Doverphos S-686, S-687 t[Dover... 

Another example showing the influence of pair interactions in complex polymer systems concerns the effectiveness of thermal stabilizers for polyolefins, when these are pigmented with a variety of rutiles. In the example, we chose polypropylene (PP) and linear low-density polyethylene (LLDPE) as hosts. These are materials without acid/base interaction potential. In order to stabilize them against thermally-initiated changes during processing, a variety of substituted phenolic substances is usually added. In the current example we have chosen two... 

There are compositional differences between polymers, especially between polyvinyl chloride and chlorinated polyvinyl chloride, which are more susceptible to degradation in processing and require higher levels of processing stabilizers, and polyolefins, which must be stabilized for processing stability as well as for protection into the service environments. There are also differences in material handling as PVC is converted from reactor flake product, whereas CPVC, PE, PP, and other materials are converted from pelletized compounds. 

Despite the promising results presented by other antioxidants, the main oxidation stabilizers of choice are sterically hindered phenols, among which Vitamin E and Irganox (1010, 1035, 1076) stand out. These antioxidants have been shown to be more effective in radiative processes [80, 81]. Also, advances on the mechanisms of stabilization in polymer processing have shown that vitamin E is more efficient compared to other commercial additives [82,83]. Tocopherol compounds were proposed as stabilizers for polyolefins in the 1980s [84] and currently, they are the best alternative for the oxidative stabilization of highly cross-linked UHMWPEs. 

Processing and long-term thermal stabilization for polyolefins and mixed plastics... 

Plastomers represent a major advancement for polyolefins. Their success allows polyolefins to have a continuum of products from amorphous EPR to thermoplastic PE and iPP. This development coincides with the advent of single-site catalysts these are necessary for copolymers of components of widely different reactivity such as ethylene and octene. Their rapid introduction into the mainstream polymer use indicates that this spectrum of properties and the inherent economy, stability and processibility of polyolefins are finding new applications to enter. 

Among the processes used for the formation of polyolefins, the longest-known but least selective one is free radical polymerization. A free radical species X produced e.g. by thermolysis of benzoyl peroxide or by photolysis of azabisisobutyronitrile (AIBN) - can react with the double bond of a vinyl derivative H2C=CHR to form a new radical of the type XCH2-CHR which can then add another H2C=CHR unit repetition of this process leads to polyolefin formation (Figure 2, top). This process works best for vinyl derivatives with unsaturated side groups, which provide resonance stabilization for an adjacent radical centre, e.g. with vinyl and acrylic esters, vinyl cyanides and vinyl chloride and with styrene and 1,3-dienes. It is extensively used in the emulsion polymerization of vinylic and acrylic derivatives and in the light-induced formation of photoresists for the nanofabrication of semiconductor chips and integrated electronic circuits. 

Hydroperoxides are potent photoinitiators and their decomposition into inactive products is an important method of stabilization in polyolefins for it prevents generation of radicals by reactions such as (4), (5), (14), and (15). Decomposition of hydroperoxides can be achieved by a reaction with phosphite esters or nickel chelates or by a catalytic action by a range of compounds including dithiocarbamates and mercaptoben-zothiazoles. Decomposition of hydroperoxides formed during processing is important for the stabilization ofPVC. 

Since UV absorbers cannot completely prevent the initiation reactions above, we felt that better antioxidants were necessary to obtain improved long-term photo-oxidative stability of polyolefins. We reasoned that stable radicals which scavenge radicals formed in the oxidative process might compensate for the imperfections of the absorbers. On the basis of the assumption that the diaryl nitroxyl radicals, rather than their parent diarylamines, are the active antifatigue species in rubber protection, we first attempted to obtain new stable nitroxyl radicals. 

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