Transparent Types

An empirical rule has been proposed that predicts whether a co-poly(am-ide) is amorphous or crystalline. This rule is based on the stereochemical contributions of the constituent monomers to the overall polymer ehain structure. It turns out that PAs with high melting points are crystalline if more than 80% of the monomer units are S5mimetrical. Thus dissymmetry favors amorphous polymers. 

Crystallinity is related to the optical properties of a polymer. In general, crystalline PAs are not transparent. If a transparent PA is desired, the PA must be amorphous rather than crystalline. Crystallinity can be determined by observing a melting point in the polymer. The amorphous character is indicated by the lack of a melting point. 

Amorphous PPA based on IPA and HMD have a low dimensional stability at elevated temperatures. To overcome this drawback, the partial replacement of HMD with an isomer mixture of 2,2,4-trimethylhexameth-ylenediamine and 2,4,4-trimethylhexamethylenediamine, respectively, has been proposed. PAs composed from adipic acid, TPA and 4,4-dimethyl-1,7-heptanediamine are transparent. In addition, 2-methyIpentameth-ylenediamine, 2-ethyItetramethyIenediamine, and 3,3 -dimethyl-4,4 -di-aminodicyclohexylmethane are diamines for transparent PAs. Also, the combination of MXDA and IPA results in transparent types. 

Glass transition temperatures of some amorphous partially aromatic PAs are shown in Table 12.8. Increasing the proportion of neopentyldi- 

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It is used in high grade industrial paints and, in combination with high performance pigments, in automotive finishes. The transparent type which is tinctoriaHy strong finds appHcations in a variety of printing inks. 

A number of diarylide yellow pigments are also available in the form of very opaque products with small specific surface areas. These are used to an appreciable extent in Chrome Yellow free paints, in packaging printing inks, and other media. Fastness to light and weather are much improved in opaque varieties, compared to the corresponding transparent types their rheological characteristics are superior. Opaque pigments are not resinated. 

At equal depth of shade, the lightfastness of P.Y.13 exceeds that of similarly transparent types of P.Y.12 by one to two steps on the Blue Scale. 

P.Y.83 shows good to very good resistance to most solvents which are typically found in application media. Recrystallization is therefore rare under common processing conditions, even in highly transparent types. Resistance to clear lacquers, calandering, and sterilization are consequently excellent. 

The commercially available, highly transparent type is primarily applied in offset printing inks. In this field, P.Y.188 matches the CIE 12-66 standard yellow shade for process printing (Sec. 1.8.1.1). The commercially available type of P.Y.188 is highly resinated and shows very good tinctorial strength. It displays good flow behavior. 

P.O.34 is supplied in a variety of types, which differ considerably in their particle size distributions. Specific surface areas range from 15 m2/g in highly opaque versions to about 75 m2/g in transparent types. It is these physical characteristics that determine the coloristic and fastness properties of each type. Even varieties of P.O.34 with fine particle sizes are generally not resinated. 

In the paint industry, transparent types are used only to a limited extent. In air drying systems, P.O.34 equals step 6-7 on the Blue Scale in full shades, while opaque colorations with TiOz (1 5) only reach step 3 for lightfastness. In baking enamels, the pigment is not fast to overpainting. 

A very opaque version has recently been introduced to the market in the USA. This type, which is also yellower than traditional varieties, demonstrates not only excellent rheological behavior but also high flocculation stability and therefore high gloss. It is slightly more weatherfast than more transparent types. The main application is in lead-free automotive finishes for full shades. 

Qualitatively, the most transparent type of model, as ever, would be a one-electron model that is capable of rendering both the ground state and, to a high degree, its excitation properties. However, in the present case, accommodations are called for, on both aspects, that are not trivial. These we will try to pursue and represent within the present one-electron-type framework as closely as possible. In seeking to develop the present model, we base it as firmly as possible on the available data, optical, photoemission, electrical, structural, etc. Much of this data is still open to interpretation, and many of the interpretations to follow are made in the light of experience gained with transition metal compounds (2). 

Depending on particle size, brilliant opaque grades with lower color strength and transparent types with higher color strength can be produced. 

Most contact adhesives contain a solvent and have a formulation tiiat combines a base of synthetic rubber such as polychloroprene or polystyrene-butadiene with reactive phenolic resins and metal oxides. In addition, there are also transparent types based on polyurethane which provide excellent bonding results for soft plastics such as plasticized PVC (used in many household articles). Recently, a solvent-fi-ee generation of contact adhesives, e.g, based on acrylate, has entered the market. This type can be used to bond solvent-sensitive materials such as polystyrene foam. 

Polystyrene (PS) 1000 Very resistant because of ring-shaped molecular structure discoloration possible in transparent types impact modified types less resistant... 

While the first type have their place in routine analysis, mostly required in the industry, the transparent-type piece of equipment (substituting once popular, laboratory self-made instruments, where each piece was intimately known in its operative functioning) should become more appreciated in the scientific and industrial research. 

W-type Acrylic weatherable impact modifier W-300A (High transparent type)... 

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