Polyethylene colour

Since acetal resins are degraded by ultra violet light, additives may be included to improve the resistance of the polymer. Carbon black is effective but as in the case of polyethylene it must be well dispersed in the polymer. The finer the particle size the better the ultra violet stability of the polymer but the poorer the heat stability. About 1.5% is generally recommended. For white compounds and those with pastel colours titanium dioxide is as good in polyacetals as most transparent ultraviolet absorbers, such as the benzophenone derivatives and other materials discussed in Chapter 7. Such ultraviolet absorbers may be used for compounds that are neither black, white nor pastel shade in colour. 

Weathering. This generally occurs as a result of the combined effect of water absorption and exposure to ultra-violet radiation (u-v). Absorption of water can have a plasticizing action on plastics which increases flexibility but ultimately (on elimination of the water) results in embrittlement, while u-v causes breakdown of the bonds in the polymer chain. The result is general deterioration of physical properties. A loss of colour or clarity (or both) may also occur. Absorption of water reduces dimensional stability of moulded articles. Most thermoplastics, in particular cellulose derivatives, are affected, and also polyethylene, PVC, and nylons. 

The earliest polymeric cationic aftertreatments stemmed from the development of crease-resist finishes for cellulosic fibres. One such, promoted specifically for its colour fastness improvements when applied as an aftertreatment to direct dyeings, was a condensation product of formaldehyde with dicyandiamide (Scheme 10.82). Many similar compounds followed, such as condensation products of formaldehyde with melamine (10.212), polyethylene imine) with cyanuric chloride (10.213) and alkyl chlorides with polyethylene imine) (10.214 R = alkyl). 

The production of light coloured products with a requirement for low build-up of static electricity requires the addition of an ingredient which is capable of providing the rubber with a low electrical resistance. Quartemary ammonium salts and ethylene oxide condensates provide one route. Of the common plasticisers, phosphate types have the lowest electrical resistance conferring properties in rubbers. Special antistatic plasticisers, such as polyethylene glycol fatty alcohol ethers, are designed to give rubbers with low surface resistivity. 

In addition to these regulatory issues there are some homemade limitations to common quality documentation (e.g. normally, pharmaceutical companies prefer to market tablets in polyethylene bottles in the United States, in contrast to blister packs for the European market and different trade names, colours or pack sizes are also unavoidable in certain cases). The consequence of these differences is the fact that a common Module 3 (Quality) and therefore a common Quality Summary in Module 2 cannot be compiled. 

Figure 7.4 Classification and image processing results of a typical situation in polymer waste recycling (a) digital image (b) initial classification result (c) calculation of separation data based on the initial classification result (d) classification result after real-time image processing. A, B Polyethylene terephthalate (PET) bottles with paper labels, C PE bottle with paper label, D PE bottle with PE film label, E PP cup, F PS cup. Classification colour code red high-density PE green PS dark blue PET yellow PP light blue paper.

Meuzelaar and co-workers [90] have described an on-line high pressure TG-GC-MS system which requires only very small amounts (10-100 mg) of sample and can be operated at high pressure under different atmospheres (N2, He, H2, etc.). The system has been used in recycling lower grade post-consumer polymers, as coloured polyethylene and polystyrene or used rubber tyres, by co-processing with coal. The main characteristics of non-simultaneous methods, TG-GC and techniques requiring a cold trap, are given in Table 1.2. 

The addition of MAPP at around 1-2% ensures perfect coverage of the wood fibres by polypropylene or polyethylene. The micrographs in Figure 5.25 clearly show the lack of adhesion between the fibres (in dark colour) and the PP matrix (in light colour). The mechanical properties are increased by at least 30% when a coupling agent is used. 

The (dichloroiodo)arene (40 mmol) and finely ground yellow mercuric oxide (10.8 g, 50 mmol) were shaken in a polyethylene bottle with dichloromethane (100 ml). Hydrofluoric acid (48%, 10 ml) was added and the bottle shaken vigorously for about 1 min. The colour of the solution turned from bright yellow to nearly colourless. Then the solvent phase was carefully decanted. The residue was shaken with dichloromethane (50 ml) which was combined with the original solution. The reagent formed was used in this solution for fluorination. In order to find its titre, a portion (1 ml) was analysed by titration of the iodine liberated by reaction with aqueous potassium iodide. The yield was calculated to be in the range 60-90%. 

Figure 97 Containers blow-moulded or extruded for a variety of household goods and toiletries. The Sqezy (centre) was made by Cascelloid, Leicester, from flexible plastic tube with metal ends, and it is understood to have been the first developed in Britain. Most of the others were made wholly from plastics, particularly polyethylenes of various densities. The containers demonstrate the use of silk-screen printing in a variety of colours for work of this kind.

Equilibrium relative humidity studies have shown that cardamom dried and maintained at or below 10% moisture retains its original colour and avoids mould growth (Govindarajan et al., 1982). If black polyethylene is used, the effect of light is further minimized and safe storage is possible for... 

One way in which most polymers do decay is by the action of oxygen in the air and of light You will be familiar with the way that some polymers go yellow after a time and some become brittle. Coloured plastics, in particular, absorb light and oxygen-induced radical reactions follow. The polymer becomes too cross-linked and loses flexibility. One ingenious application of this natural process helps to degrade the polythene rings that hold cans of beer in packs. These are often discarded and decay quite quickly because some carbon monoxide has been incorporated into the polyethylene to make it more sensitive to photolysis. 

Alpha Packaging manufactures botdes and jars made from polyethylene terephthalate (PET) and high-density polyethylene (HDPE) for the pharmaceutical, nutritional and personal care markets. Technologies used include injection blow moulding, injection stretch blow moulding, and extrusion blow moulding. Alpha manufactures stock and custom containers in a variety of styles and colours. 

An additive system was developed for poly(vinyl chloride) for medical applications. The additives include primary stabilisers (Ca-Zn stearate and Zn stearate), secondary stabilisers (epoxides) and lubricants (ethylene bisamide and high density polyethylene), to improve melt processing and heat stability. The use of the stabilisers resulted in reduced equipment down-time, increased the level of recycled material which could be incorporated, and enhanced the product characteristics, including colour, clarity, blush, aqueous extractables and particle generation. 5 refs. 

Fig. 7a-c. Phase contrast microscope pictures of a blend of ethylene-vinyl acetate copolymer (40% vinyl acetate) with chlorinated polyethylene (43 % chlorine) before and after phase separation. Since both polymers are elastomers the mobility is quite high. The original pictures are coloured red and green. These black and white pictures have enhanced contrast to make the phase separation clear... 

Polyethylene glycol in the synthesis of materials. PEG has been used as a solvent in polymerization reactions. It was found to facilitate easy removal of the metal catalyst in transition metal mediated living radical polymerization (Figure 8.10). Products from this type of polymerization are usually heavily contaminated with intensely coloured copper impurities. In the case of methyl methacrylate polymerization the reaction rate was higher than in conventional organic solvents, but for styrene the reaction was slower than in xylene. 

Industrial or synthetic polymers find extensive use in modern day society. They are many in number, polyvinyl chloride (PVC) polyamides (Nylon), polyethylene teraphthalate (PET), polystyrene and polyolefins, to name but a few. Polymers are without exception very complex compounds, capable of manifesting themselves in many shapes and forms. They can exist as viscous liquids, powders, coloured granules, cast or extruded sheet, transparent or translucent film, formulated (in some cases in excess of ten different additives may be added) or unformulated. Hence they can present a very daunting task to the analyst or polymer chemist wishing to fully characterise such materials. 

They arc made of a laminated melaminealkyd core encapsulated in polyethylene wax. The core is colour coded by the inclusion of pigments. One of the layers contains iron particles to make the taggant magnet-sensitive and one or both exterior layers contain fluorescent compounds which respond to ultraviolet radiation. 

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