Melting Range

First,/)-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) are acetylated to produce the low melting acetate esters which are molten at 200°C. In an inert gas, the two monomers are melted together at 200°C. The temperature is raised to 250—280°C and acetic acid is coUected for 0.5 to 3 h. The temperature is raised to 280—340°C and additional acetic acid is removed in vacuum for a period of 10 to 60 min. The opalescent polymer melt produced is extmded through a spinning jet, foUowed by melt drawdown. The use of the paraUel offset monomer, acetylated HNA, results in the formation of a series of random copolyesters of different compositions, many of which faU within the commercially acceptable melting range of... 

The sohdus temperature (lower limit of alloy melting range). ... 

Alloy selection depends on several factors, including electrical properties, alloy melting range, wetting characteristics, resistance to oxidation, mechanical and thermomechanical properties, formation of intermetaUics, and ionic migration characteristics (26). These properties determine whether a particular solder joint can meet the mechanical, thermal, chemical, and electrical demands placed on it. 

Substituted amides CAS Registry Molecular formula Melting range. Flash Gardner color... 

AHoy content, wt % Melting range, °C Typical tensile strength Uses... 

Commeicial grades of diorganotin carboxylates frequendy have wider melting ranges because of the use of less pure grades of carboxylic acids in their manufacture which, for many apphcations, permits mote facile handling of the hquids. 

AUoy Constituents, wt % Be Co Density, g/mL Elastic modulus GPa Thermal expansion coefficient, ppm/°C Thermal conductivity, W/(m-K) Melting range, °C... 

Alio/ Other Density, g/mL Elastic Thermal Thermal Melting range. 

The crystallisation process for concentrating bismuth ia lead by squeesiag the eutectic (high ia bismuth) Hquid out of the solidified high lead portion at a temperature within the melting range of the alloy is seldom used. 

Table 8. Melting Ranges for Typical Neutral Polyamides...

Dimer trimer mol ratio Diamine Polyamide melting range, °C... 

Type Composition (wt%j Melting range (°Cj Typical uses... 

The melt viscosity of a polymer at a given temperature is a measure of the rate at which chains can move relative to each other. This will be controlled by the ease of rotation about the backbone bonds, i.e. the chain flexibility, and on the degree of entanglement. Because of their low chain flexibility, polymers such as polytetrafluoroethylene, the aromatic polyimides, the aromatic polycarbonates and to a less extent poly(vinyl chloride) and poly(methyl methacrylate) are highly viscous in their melting range as compared with polyethylene and polystyrene. 

In the case of crystalline polymers such as types E and F the situation is somewhat more complicated. There is some change in modulus around the which decreases with increasing crystallinity and a catastrophic change around the. Furthermore there are many polymers that soften progressively between the Tg and the due to the wide melting range of the crystalline structures, and the value determined for the softening point can depend very considerably on the test method used. 

The melting ranges and glass transition temperatures of a number of polycarbonates from di-(4-hydroxyphenyl)methane derivatives are given in Table 20.10. 

Polycarbonates have also been prepared from diphenyl compounds where the benzene rings are separated by more than one carbon atom. In the absence of bulky side groups such polymer molecules are more flexible and crystallise very rapidly. As is to be expected, the more the separating carbon atoms the lower the melting range. This effect is shown in data supplied by Sehnell" Table 20.11). 

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