Shrinkage diying

Bricks %Diying shrinkage %Firing shrinkage Bulk density (g/cm ) Apparent density (g/cm ) %Water absorption Thermal conductivity (W/mK) at 40°C... 

Although direc t contactive heat transfer can provide high temperatures and heat concentrations and at the same time be small in size, its use may not always be preferable because of undesired side effec ts such as diying, contamination, case hardening, shrinkage, off color, and dusting. 

Mortar samples (under the same conditions and sand/cement proportions as for the mechanical tests) were made to determine the linear retraction in the red gypsum cements that occurs due to their progressive diyness. The mortars were tested in accordance with regulation ASTM C 596-89 Standard Test Method for Drying Shrinkage of Mortar Containing Portland Cement . Special moulds were filled with the mortar samples for this purpose, as described in this protocol. 

Prediylng at 90-100°C for 2-4 hours is necessary before injection molding because insuflELdently diy material may cause appearance of silver streaks. Molding conditions of TB are suggested as follows Cylinder temperatm e nozzle - 230-260, front - 230-260, middle - 230-250, rear -210-230°C Injection pressm-e - 80-100 MPa Mold temperature 40-60°C. The mold shrinkage of TB is 0.5-0.8% compared with ABS 0.4-0.6% which indicates that a mold must be carefully designed. 

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