Product structure amorphous

The above description of the process is tentative because it is based on limited data. If it is correct, the predominate structures in the PHBA-modified products have amorphous PA/AA/NPG center sections end-capped with single units or short blocks of oligomeric PHBA. Random distribution of the PHBA cannot be ruled out, but the hetero-geneiety of the products suggests that a substantial fraction of PHBA is incorporated into short blocks. The FT-IR and GPC data are consistent with the proposal that short, phenolic-tipped oligomers are the predominant structure present. The possibility that the materials are physical mixtures of oligo-PHBA and amorphous diols can be virtually ruled out on the basis of the extreme insolubility of oligo-PHBA (IJ) and of the model PHBA-benzoic acid adduct synthesized in this study. These materials separate readily from solutions and dispersions of PHBA copolymers. 

The presented results show that tin can be introduced into the framework positions of the AIPO4-5 structure. An increase in tin content above 3% always results in amorphous products. The amorphous products still show some porosity. Due to the framework position of... 

Product structure. Dehydration may result in relatively minor changes in structure such as decreases in some or all unit cell dimensions in topotactic processes. Alternatively, reaction may result in fundamental reorganization through recrystallization, or conversion to an amorphous or zeolitic material. Dehydration. Dehydration mechanisms encompass a wide variety of routes, summarized in Figure 7.4. The following features require comment. 

Although inclusion bodies are generally amo hous, expression of insecticidal proteins in E, coli has been shown to result in the formation of crystalline, bipyramidal inclusion bodies in the cytoplasm when the cells were grown at 30°C (65). Growth at at 37 C induced the production of amorphous, spherical structures. The foreign protein corresponded to 70% of the total protein of these aggregates compared to 9()% in the bipyramidal inclusion bodies formed at 30 C. 

Product Structure A feature frequently observed in the decomposition of crystalline hydrates, which has not yet been given a convincing interpretation in the framework of universally accepted ideas, is the formation of solid products in either an amorphous or a crystalline state, depending on the actual water vapour pressure in the reactor. This phenomenon was observed by Kohlschiitter and Nitschmann in 1931 [35] and has been the subject of numerous publications, including the study of Volmer and Seydel [36], who used it as a basis for explaining the Topley-Smith (T-S) effect, and a series of articles by Frost et al. [37-39]. Dehydration of many crystalline hydrates in vacuum entails formation of an X-ray amorphous (finely dispersed) residue and, in the presence of water vapour, formation of a crystalline product. The highest H2O pressure at which an amorphous product can still form varies for different hydrates from a few tenths to a few Torr (Table 2.4). As the decomposition temperature increases, the boundary of formation of the crystalline product shifts towards higher H2O pressures. 

These include the qualitative or quantitative interpretation of phenomena, effects, and regular trends observed in the course of thermal decomposition. The most significant achievements are the explanation of the mechanism of the nucleation and growth of nuclei and the interpretation of such effects as localization of the decomposition process, the T-S effect, a decrease in the decomposition rate upon melting of the reactant, differences in the structure (amorphous or crystalline) of the solid product, and the effect of gaseous products and foreign gases on the decomposition rate. 

For the various POY yams textured at constant tension to a fixed tenacity and elongation target (3.3 grams per denier tenacity 18% elongation), the number of broken filaments generated by the texturing operation decreases with Increased yam stmcture (Table 1). Interestingly, the best POY structure versus PTY broken filament number correlation Is achieved with the reciprocal product of amorphous orientation (fa) and crystalline content (x) ... 

Atomizers nozzle (air, pressure position, number) rotary, etc. Shape/size, size distribution of drops Trajectory of drops Flow rate/pressure drying air Temperature air inlet/outlet Flow rate/temperature product Powder yield (TS), sticking Water content, aw composition, retention, degradation,% surface structure (amorphous, crystallized) Size, density, wettability, flowabiUty, surface state Temperature, Tg, MP... 

Most stereoselective coordination catalysts polymerize propylene oxide to yield polymers that contain high ratios of isotactic to syndiotactic sequences. Laige portions of amorphous materials, however, are also present in these same products. These amorphous portions contain head-to-head units that are imperfections in the structures. For every head-to-head placement, one (R) monomer is converted to an (S) unit in the polymer. This shows that at the coordination sites abnormal ring openings occur at the secondary carbon with an inversion of the configuration and result in head-to-head placements. Also, erythro and threo isomers units are present. The isotactic portion consists almost exclusively of the erythro isomer while the amorphous fraction contains 40-45% erythro and 55-60% threo ... 

Attempts had been made to synthesise polyesters based on phthalic acid as the diacid component, but these products were amorphous, had low softening points, and were rapidly attacked by organic solvents and acids and bases. Research into polyesters made by the reaction of terephthalic acid (or esters thereof) with aliphatic diols, led to the discovery of polyesters of high commercial value poly(alkylene terephthalate)s [4]. This pairing of diols with terephthalic acid eventually led to the most commercially successful aromatic polyesters, but other synthetic pathways were also investigated towards such products in the early days of polyester development. These included the self-condensation of hydroxy acids of the structure -H0-R-Ph-C02H, where R-OH is para to the acid group and R is -(CH2)- or -(CH2)2- [5], and reactions of aliphatic diacids with 1,4-dihydroxy benzene and similar aromatic diols [6, 7]. Also synthesised about the same time were polyesters based on C2-Cg aliphatic diols and any of the isomeric naphthalene dicarboxylic acids [8]. 

The fourth example shows that some amorphous HP-LCVD fibers having binary silicon-nitrogen compositions [17] were silicon rich, others were near stoichiometric Si-N compositions, and only a few were representative of stoichiometric silicon nitride. Thus, the process offers wide latitude in the design of fibers with amorphous or glassy structures. These design options facilitate the production of amorphous fibers from equilibrium and nonequilibrium melt compositions and of amorphous fibers having stoichiometric or non-stoichiometric, binary compositions. 

Since the hydroxyl of carbon 6 is not methylated, it is probably involved in ring formation. Inasmuch as the methylation of the osazones proceeds with difficulty and most of the products are amorphous, this evidence cannot be considered as final, although the analogous behavior of the osazones, hydra-zones, and other nitrogenous derivatives makes a ring structure seem probable. Similar methylation evidence indicates a ring structure for galactosa-zone 237). 

The synthesis of crystalline, syndiotactic 1,2-polybutadiene is also successful with compounds of titanium, cobalt, vanadium, and chromium [194,206-210]. Alcoholates [e.g., cobalt(II) 2-ethylhexanoate or titanium(III) butanolate] with triethylamine as cocatalyst, are especially well suited for this purpose. They are capable of producing polymers with up to 98% 1,2 structure. Amorphous 1,2-polybutadiene is produced with molybdenum(V) chloride and diethylmethoxyaluminum [211]. Addition of esters of carboxylic acids raises the vinyl content of the products [212]. The influence of the coordination at the center atom is remarkable. Trisallylchromium polymerizes 1,3-butadiene to 1,2-polybutadiene, while bisallylchromchloride gives 1,4-poly butadiene. 

The retention or loss of aroma compounds is also influenced by the structure (amorphous or crystallized) of the dried product Structural changes can be used for spray drying encapsulation processes (Bhandari et al., 1992 Re, 1998). Crystallization tends to increase the loss of aroma, because it rejects impurities, including volatiles. Senoussi et al. (1995) measured the loss of diacetyl as a function of the rate of crystallization of lactose during storage. They found that when the lactose was stored at 20 °C above the glass transition temperature Tg, the amorphous product immediately crystallized and practically all diacetyl was lost after 6 days. Levi and Karel (1995) also found increased rates of loss of volatile (1-n-propanol) as a result of crystallization in an initially amorphous sucrose system. 

Solid-state chemistry is less widely used than solution chemistry but the particular molecular configuration and interaction imposed by the crystal lattice leads to a well defined reaction product. The very specific nature of the lattice packing required for reaction, however, makes the solid-state route less predictable than solution chemistry. Solid-state polymerization has been observed to occur by bulk, topotactic and topochemical reactions. In bulk reactions the product is amorphous because the crystal lattice is destroyed during the reaction. Topotactic reactions produce a product phase which has a small number of orientations, possibly only one, with respect to the initial crystal. Topochemical reactions are those in which the reaction path is determined by the crystal structure and may lead to a topotactic product. 

For particulate materials, the product properties depend on the chemical composition and on the dispersity of the material. The dispersity is characterized by the particle size distribution (PSD), the particles shape, their morphology in terms of internal structure (amorphous, crystalline, internal pore size distributions and their defects), and their interfacial properties. This relation was called by Rumpf already in the 1960s of the last century the property function (Rumpf, 1967). Control of the property function is the core of product engineering or product design. 

Tubercles are much more than amorphous lumps of corrosion product and deposit. They are highly structured. Structure and growth are interrelated in complex ways. 

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