Cure temperatures

The process known as transimidization has been employed to functionalize polyimide oligomers, which were subsequentiy used to produce polyimide—titania hybrids (59). This technique resulted in the successhil synthesis of transparent hybrids composed of 18, 37, and 54% titania. The effect of metal alkoxide quantity, as well as the oligomer molecular weight and cure temperature, were evaluated using differential scanning calorimetry (dsc), thermogravimetric analysis (tga) and saxs. 

Eig. 2. Cure rate of PPS as a function of soHd-state cure temperature. 

Process Viscosity, mPa-s(=cP) Cure temperature, °C Thixotropy Filler, % Glass, %... 

Early recommendations for cross-linking CSM involved the use of divalent metal oxides to form metal sulfonate cross-links (24). The mechanism involves the hydrolysis of the sulfonyl chloride group with a carboxyHc acid, ie, stearic acid, which produces water at curing temperatures. 

Preparation of paint, its viscosity, solvent, thickness of one coat, air pressure, curing temperature and time of curing will remain the same as for the primer (Table A13.4). 

The viscosity should quickly reach a suitable value on heating in the barrel. It should not be too high since it may be difficult to fill the mould. At the same time it should not be so low that little heat is generated by friction. At the injection melt temperature of 100-130°C the compound should have a good stability but should cure rapidly at the high curing temperatures as exist within the mould. 

Figure 24.9. Effect of cure time on some properties of M-F mouldings. Cure temperature cellulose filled 295-308°F mineral filled 300-320°F O glass-filled material, asbestos-filled material, A cellulose-filled material (a) Cross-breaking strength (b) tensile strength (c) impact strength (d) impact strength (e) water absorption (rag), boiling water 30 min (f) cold water 24 h, 23°C ...

The ebonite compound before cure is a rather soft plastic mass which may be extruded, calendered and moulded on the simple equipment of the type that has been in use in the rubber industry for the last century. In the case of extruded and calendered products vulcanisation is carried out in an air or steam pan. There has been a progressive reduction in the cure times for ebonite mixes over the years from 4-5 hours down to 7-8 minutes. This has been brought about by considerable dilution of the reactive rubber and sulphur by inert fillers, by use of accelerators and an increase in cure temperatures up to 170-180°C. The valuable effect of ebonite dust in reducing the exotherm is shown graphically in Figure 30.3. 

Fig. 42. AES depth profiles of copper and sulfur (top) and zinc and oxygen (bottom) for the brass-on-glass adhesion specimens as a function of curing temperature. Reproduced by permission of Gordon and Breach Science Publishers from Ref. [46].

Radiation cure system. Other addition reaction cure systems that have emerged in recent years are the ultra-violet (UV) and electron beam (EB) radiation cure systems. The development of these systems has been prompted by the ever-increasing need for fast cure rates and low cure temperatures. The U V cure system... 

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