Additives Dimensional stability

An additional dimensional stability evaluation was done with a shrinkage template apparatus (Figure 1.2). 

As Carfagna et al. [61] suggested, the addition of a mesophasic polymer to an amorphous matrix can lead to different results depending on the properties of the liquid crystalline polymer and its amount. If a small amount of the filler compatible with the matrix is added, only plasticization effect can be expected and the dimensional stability of the blend would be reduced. Addition of PET-PHB60 to polycarbonate reduced the dimensionality of the composite, i.e., it increased the shrinkage [42]. This behavior was ascribed to the very low... 

Materials with totally new property combinations may be achieved by blending two or more polymers together. Through blending of thermotropic main-chain LCPs with engineering thermoplastics, the highly ordered fibrous structure and good properties of LCPs can be transferred to the more flexible matrix polymer. LCPs are blended with thermoplastics mainly in order to reinforce the matrix polymer or to improve its dimensional stability, but LCP addition may modify several... 

To be successful, molded optical elements of plastics must be produced with careful control of the fabricating process. In the case of these optical products it is particularly important that the molding conditions be carefully controlled to minimize molded-in stress. In addition to these stresses reducing the dimensional stability of the products leading to distorted images, the stresses themselves affect the quality of the image. This is a result of the fact that the stresses/strained areas have a different refractive index from that of the... 

For applications having only moderate thermal requirements, thermal decomposition may not be an important consideration. However, if the product requires dimensional stability at high temperatures, it is possible that its service temperature or processing temperature may approach its temperature of decomposition (Tj) (Table 7-12). A plastic s decomposition temperature is largely determined by the elements and their bonding within the molecular structures as well as the characteristics of additives, fillers, and reinforcements that may be in them. 

These characteristics can be further enhanced and their applications widened by fillers, additives, and reinforcements. Compounding properly will yield an almost limitless combination of an increased loadcarrying capacity, a reduced coefficient of friction, improved wear resistance, higher mechanical strengths, improved thermal properties, greater fatigue endurance and creep resistance, excellent dimensional stability and reproducibility, and the like. 

In addition to the above chemical reactivity and dimensional stability problems, Minol 11 exhibits borderline initiatability at —65°F with small boosters, but initiates reliably at low temps with standard larger boosters (Ref 43)... 

As discussed in Chapter 10, a wide variety of additives is used in the polymer industry. Stabilizers, waxes, and processing aids reduce degradation of the polymer during processing and use. Dyes and pigments provide the many hues that we observe in synthetic fabrics and molded articles, such as household containers and toys. Functional additives, such as glass fibers, carbon black, and metakaolins can improve dimensional stability, modulus, conductivity, or electrical resistivity of the polymer. Fillers can reduce the cost of the final part by replacing expensive resins with inexpensive materials such as wood flour and calcium carbonate. The additives chosen will depend on the properties desired. 

The particular requirements of shrink-resist processes in relation to wool fabric printing have been described [312]. In addition to dimensional stability, there is a need for ease of... 

Pettifor s structure maps additional remarks. We have seen that in a phenomenological approach to the systematics of the crystal structures (and of other phase properties) several types of coordinates, derived from physical atomic properties, have been used for the preparation of (two-, three-dimensional) stability maps. Differences, sums, ratios of properties such as electronegativities, atomic radii and valence-electron numbers have been used. These variables, however, as stressed, for instance, by Villars et al. (1989) do not always clearly differentiate between chemically different atoms. 

Wood modification can improve the dimensional stabilization of wood by two mechanisms. Where the cell wall is filled in some way by the reagent (whether covalently bound or not), the cell wall is swollen. When the dimensional stability of the modified wood is subsequently determined, the wood can then only swell by an additional amount, which is dependent upon the bulking of the cell wall due to the volume occupied by the modifying agent. This is illustrated in Figures 2.8 and 2.9b. 

Matsuda, H., Ueda, M. and Murakami, K. (1988e). Oligoesterifed woods based upon anhydride and epoxide I. Preparation and dimensional stability of ohgoesterified woods by stepwise addition reactions. Mokuzai Gakkaishi, 34(2), 140-148. 

Yasuda, R. and Minato, K. (1995). Chemical modification of wood by non-formaldehyde cross-linking agents. Part 3. Mechanism of dimensional stabilization by glyoxal treatment and effect of the addition of glycol. Wood Science and Technology, 29(4), 243-251. 

With the advent of the soluble stereoregulating catalysts, so-called older polymers have been synthesized with additional control over the structure giving products with enhanced strength and dimensional stability. Amorphous PS is relatively brittle, requiring a plasticizer to allow it to be flexible. The use of soluble stereoregulating catalysts allowed the synthesis of sPS with a I m of about 270°C and a Tg of about 100°C with good solvent and chemical resistance. DOW commercialized sPS under the trade name Questra in 1997. It is used in specialty electrical and under-the-hood automotive applications. 

The most important characteristic of cement is its pore structure and aqueous phase hence, the microstructure of the hardened cement paste via the pore system. It is highly alkaline (pH >13) due to rapid and almost quantitative dissolution of Na and K salts from the cement clinker. The porosity of the paste comprises interconnected and isolated pores, the pore sizes of which are important to the strength and dimensional stability of cement products. Different types of cement are used to meet different performance criteria. Properties can be estimated from compositions and fineness (i.e., particle size and size distribution). In the past, additives... 

When an expl is pressed in a die by means of a ram, the friction of the walls tends to cause press and density gradients. In addition, the one-dimensional compression can result in an anisotropic structure and produce pellets with residual strains. Where dimensional stability, uniformity and high density are essential to performance, hydrostatic pressing and isostatic pressing have been used. In both of these processes, the expl is compressed by the action of a fluid, from which it is separated by a rubber (or other elastomer) film... 

Addition copolymers of cycloolefin compounds with a polar substituents in the side chain exhibit excellent heat resistance and transparency. They are also capable of crosslinking to improve the adhesion properties, the dimensional stability and the chemical resistance (35). 

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