Translucent polymers

In contrast to the commercial a/-PS, which is amorphous and transparent, //-PS is a very brittle crystalline translucent polymer which exists as a helix with three repeating units per turn. The crystalline polymer has a high specific gravity (1.12) and a high melting point Tm (230 C). 

One can assume that blends of polymers will be more difficult to color than any single component by itself. Diffuse reflection can increase due to internal light reflection or scattering at phase interfaces if the polymers are at least partially immiscible or their refractive indices are significantly different. Blends of translucent polymers are typically more opaque than either resin alone. Furthermore, colorant stability (thermal or chemical) can be adversely affected by the presence of the other polymer(s). As in the case of neat polymers, both circumstances will result in a restricted achievable color gamut for the polymer blend. An example of a prominent polymer blend is GE s Noryl (PS/PPO), which certainly colors much differently than the polystyrene component by itself. 

Mica-Lyte, Dekorflake, Microfibers, Specular - selected natural, colored, and shaped materials designed as special-effect colorants to impart granite-hke, sparkling, and textured appearances to transparent and translucent polymers... 

Homopolymer PP this is a translucent polymer, with high Heat Distortion Temperature (HDT), with a lower impact strength (particularly at low temperatures) and is used for applications such as closures and soup pots ... 

Br 9.1% P - 65-72 - Translucent polymers (e.g. cast PMMA), plasticized PVC, unsaturated polyester, flexible PUR foam, CA fibre... 

See color measurement and control for a discussion on applying color quality standards (color evaluation, comparison, matching, and specification). However, a case of special interest is assoicated with the tendency for many initial colorless or white, transparent, or translucent polymers to develop undesirable yellowish color, with aging in particular. A standard method (ASTM D1925), based on the use of a recording spectrophotometer for transmittance and reflectance measurement, permits the determination of a yellowness index (YI). 

It is important to distinguish between surface and bulk scattering for testing purposes the former is minimized by wetting the surface with a liquid of similar refractive index. That way the two effects (surface vs bulk) can be decoupled. The milk-like appearance of translucent polymer samples viewed from the side on which light is incident is due to back scattering. 

Smeets NMB, Moraes RP, Jeffery A, McKenna TFL. A new method for the preparation of concentrated translucent polymer nanolatexes from emulsion polymerization. Langmuir 2011 27 575-581. 

It has been found, by the authors, that monochromatic emissive power relationships for different radiation sources are not easily obtained in the literature. For that reason, the various plots of intensity vs. wavelength are included for general information as well as provide a data source for those requiring emissive power information for different radiation systems. Further, Figures 13-30 indicate the relationship of spectral reflectance and spectral transmittance for several transparent or translucent polymers. 

Table lA tabulates the average reflectivity for serveral transparent /translucent polymers for solar, benzene flame and the radiant panel radiation. 

Synthetic Marble. Synthetic marble-like resin products are prepared by casting or molding a highly filled monomer mixture or monomer—polymer symp. When only one smooth surface is required, a continuous casting process using only one endless stainless steel belt can be used (52,53). Typically on the order of 60 wt % inorganic filler is used. The inorganic fillers, such as aluminum hydroxide, calcium carbonate, etc, are selected on the basis of cost, and such properties as the translucence, chemical and water resistance, and ease of subsequent fabrication (54,55). 

Polyamides, often also lefeiied to as nylons, are liigli polymers which contain the amide repeat linkage in the polymer backbone. They are generally characterized as tough, translucent, semicrystalline polymers that ate moderately low cost and easily manipulated commercially by melt processing. 

Natural resins are generally described as solid or semisolid amorphous, fusible, organic substances that are formed in plant secretions. They are usually transparent or translucent yeUow-to-brown colored, and are soluble in organic solvents but not in water. The principal uses for natural resins are in varnishes, printing inks, adhesives, paper size, and polymer compositions. The term natural resins includes tree and plant exudates, fossil resins, mined resins, and shellac. They often have been altered from their original state during isolation and processing. For some appHcations, the resins have been chemically modified to increase their industrial utiUty. 

In the crystalline region isotactic polystyrene molecules take a helical form with three monomer residues per turn and an identity period of 6.65 A. One hundred percent crystalline polymer has a density of 1.12 compared with 1.05 for amorphous polymer and is also translucent. The melting point of the polymer is as high as 230°C. Below the glass transition temperature of 97°C the polymer is rather brittle. 

The self-extinguishing characteristics of the chlorine-containing resins are improved by incorporation of antimony oxide but this approach is not possible where translucent sheet is required. As an alternative to chlorine-based systems a number of bromine-containing resins have been prepared and, whilst claimed to be more effective, are not currently widely used. It is probably true to say that fire-retarding additives are used more commonly than polymers containing halogen groupings. 

It is suggested that the first material to be considered is polypropylene. The polymer has a number of desirable properties, as discussed in Chapter 11. These include low density, reasonable toughness, flexibility and strength at normal room temperatures, good resistance to hot water for a moderate period, low water absorption, translucency and good surface finish. Furthermore, it is one of the cheapest materials currently available. 

There is bound to be one problem with resin glass polyalkenoate cement. Because the matrix is a mixture of hydrogel salt and polymer, lightscattering is bound to be greater than in the conventional material. Moreover, the zinc oxide-containing glass of class II materials is bound to be opaque. This makes it difficult to formulate a translucent material and is the reason why their use is restricted to that of a liner or base. However, the class II material cited will be radio-opaque because it uses strontium and zinc, rather than calcium, in the glass. 

First, oligo(ethylene oxide) monomethylether was treated with excess BH3-THF complex in THF. After solvent and borane-THF were removed under reduced pressure, the resulting hydroborane with an oligo(ethylene oxide) tail was polymerized with triethyleneglycol in THF at room temperature (r.t.). The polymers obtained were purified by reprecipitation into //-hexane or by washing with diethylether to give colorless or translucent gums in 61—76% yield. 

Low Tinting Strength - The zinc borate has a refractive index similar to most organic polymers, which results in the retention of considerable translucency. This provides for easy visual inspection of the finished products and allows the use of lower pigment loadings in formulations requiring deep shades. 

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