Stabilisers antioxidants

There are a number of occasions where a transparent plastics material which can be used at temperatures of up to 150°C is required and in spite of its relatively high cost, low impact strength and poor aging properties poly-(4-methylpent-1 -ene) is often the answer. Like poly(vinyl chloride) and polypropylene, P4MP1 is useless without stabilisation and as with the other two materials it may be expected that continuous improvement in stabilising antioxidant systems can be expected. 

In addition to stabilisers, antioxidants and ultra-violent absorbers may also be added to PVC compounds. Amongst antioxidants, trisnonyl phenyl phosphite, mentioned previously, is interesting in that it appears to have additional functions such as a solubiliser or chelator for PVC insoluble metal chlorides formed by reaction of PVC degradation products with metal stabilisers. Since oxidation is both a degradation reaction in its own right and may also accelerate the rate of dehydrochlorination, the use of antioxidants can be beneficial. In addition to the phenyl phosphites, hindered phenols such as octadecyl 3-(3,5-di-tcrt-butyl-4-hydroxyphenyI)propionate and 2,4,6-tris (2,5-di-rcrt-butyl-4-hydroxybenzyl)-1,3,5-trimethylbenzene may be used. 

The use of stabilisers (antioxidants) may, however, have adverse effects in that they inhibit cross-linking of the rubber. The influence of phenolic antioxidants on polystyrene-SBR alloys blended in an internal mixer at 180°C has been studied. It was found that alloys containing 1% of certain phenolic antioxidants were gel-deficient in the rubber phase.The gel-deficient blends were blotchy in appearance, and had lower flow rates compared with the normal materials, and mouldings were somewhat brittle. Substantial improvements in the impact properties were achieved when the antioxidant was added later in the mixing cycle after the rubber had reached a moderate degree of cross-linking. 

It is also important to bear in mind that, for end use, polymers may be mixed with a number of additives such as plasticisers, stabilisers, antioxidants, fillers, hre-retardants, pigments and so on, and thit this may well... 

It is of interest to examine the development of the analytical toolbox for rubber deformulation over the last two decades and the role of emerging technologies (Table 2.9). Bayer technology (1981) for the qualitative and quantitative analysis of rubbers and elastomers consisted of a multitechnique approach comprising extraction (Soxhlet, DIN 53 553), wet chemistry (colour reactions, photometry), electrochemistry (polarography, conductometry), various forms of chromatography (PC, GC, off-line PyGC, TLC), spectroscopy (UV, IR, off-line PylR), and microscopy (OM, SEM, TEM, fluorescence) [10]. Reported applications concerned the identification of plasticisers, fatty acids, stabilisers, antioxidants, vulcanisation accelerators, free/total/bound sulfur, minerals and CB. Monsanto (1983) used direct-probe MS for in situ quantitative analysis of additives and rubber and made use of 31P NMR [69]. 

David et al. [184] have shown that cool on-column injection and the use of deactivated thermally stable columns in CGC-FID and CGC-F1D-MS for quantitative determination of additives (antistatics, antifogging agents, UV and light stabilisers, antioxidants, etc.) in mixtures prevents thermal degradation of high-MW compounds. Perkins et al. [101] have reported development of an analysis method for 100 ppm polymer additives in a 500 p,L SEC fraction in DCM by means of at-column GC (total elution time 27 min repeatability 3-7 %). Requirements for the method were (i) on-line (ii) use of whole fraction (LVI) and (iii) determination of high-MW compounds (1200 Da) at low concentrations. Difficult matrix introduction (DMI) and selective extraction can be used for GC analysis of silicone oil contamination in paints and other complex analytical problems. 

Light fastness is mainly determined by the nature of polymer and dyestuff and by the interaction between the two. Additives like pigments and stabilisers (antioxidants) are important. The better the light fastness of the polymer, the greater the chance that it will have a good colour fastness. 

These constituents may include additives antistatic additives, UV absorbers, antislip additives, slip additives, colourants, opacifiers, plasticisers, stabilisers, antioxidants, etc., which may be added at the compounding stage to provide specific or modified properties. However, other constituents may be present from the polymerisation and/or the converting processes. The polymerisation process may involve residues and processing aids. Residues (constituents which may remain from the polymerisation process) may include monomer(s), solvents, accelerators, catalysts, initiators, etc. Processing aids are additional substances to aid processing or restrain undesirable effects, e.g. antioxidants. 

VI.I.2.2.3. pages 1-5 Covers homopolymer and copolymer. Limit of not more than three stabilisers (antioxidants) from a list of nine. Polypropylene for containers for preparations for parenteral use. (1990)... 

Limit of not more than three stabilisers (antioxidants) from a list of five. 

Stabilisers/Antioxidants Phosphite/phosphonites are generally regarded as the most effective stabilisers during processing, protecting both the polymer and the primary antioxidant. The most expensive stabilisers are organotin stabilisers, while lead compounds are the cheapest. 

It should be pointed out that a jet-type tubular turbulent reactor of similar design, instead of stirred tank reactors with mechanical stirrers, can and should be used at other stages of the process of chlorinated BR production, in particular, for the neutralisation of the modified polymer solution (the rate constant of the interaction between mineral acids and alkalis is k 10 1/mols), removal of salts and other substances from the chlorinated BR solution by water washing (extraction), removal of back solvent (extraction), and introduction of the stabiliser-antioxidant and adhesion reducing powder (mixing) into the polymer solution. 

Clariant businesses are organised into five divisions pigments and additives masterbatches textile, leather and paper chemicals functional chemicals, and finally life science and electronic chemicals. Several polymer additive products have been mentioned already in Chapter 5. They include waxes, UV and light stabilisers, antioxidants, antistatic agents, flame retardants and phosphorus flame retardants. Some additives are targeted at other industries besides plastics. The company claims to be the world leader in pigments. 

Plastics contain additives such as heat and light stabilisers, antioxidants, UV-absorbers, lubricants and plasticisers, which cannot be used in any device/item to be placed inside the body. However, these additives are absolutely necessary for the processing and... 

Schroder [38] has reviewed work [25, 78, 127-137] carried out on the applications of TLC to plastics additives such as plasticisers [127-129, 135], stabilisers, antioxidants, UV absorbers, lubricants, antistatic agents and optical brighteners. 

DPC provides a means of characterising polymers supplementing information obtainable by traditional thermal methods, e.g., the physical properties of the photopolymer can be measured before and after exposure to light. The combined physical and light-sensitive properties provide information on rate of cure, as well as the effect of cure on the physical properties of the material, e.g., time-heat flow plots with different pigments, stabilisers, antioxidants, and plasticisers. 

Kawaguchi et al [839] have reviewed the application of ESR for studies of reaction mechanisms of polymer additives (light stabilisers, antioxidants, carbon-black/rubber coupling agent), and of molecular motions of polymers. More recently, more general ESR applications have been reviewed [840]. Various books deal with applications of ESR [841], in particular also in relation to polymer research [842]. 

Plastics additives may be divided into two main categories —those which modify polymer properties by physical means, such as plasticisers, lubricants, impact modifiers, fillers, pigments, etc, and additives which achieve their effect by chemical reactions such as PVC heat stabilisers, antioxidants, ultraviolet absorbers and flame retardants. In selecting them, however, care must be taken to match the additives to the polymer they are intended to protect, taking into account such factors as compatibility, efficiency and possible synergism of two or more additives in the particular polymer under consideration. 

Polymer stabiliser, antioxidant sunscreen agent. Used as 0.006% soln. in cone. H2SO4 for fluorimetric detn. of B (2max 503 nm). Needles (H2O). Sol. cone. H2SO4. Mp 142.6-144.6°. 

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