Abstract: Capacitance is measured using a system including a high voltage ramp monitor. A signal net is connected to ground by probes while a constant charging current is applied to the internal planes. A pure capacitive net will have a linear voltage rise proportional to capacitance, therefore its capacitance can be represented by ramp time. Leakage shorts will be detected by residual charge current measurements. The stimulus voltage is maintained for a fixed time after ramping to provide net to internal plane stress testing. Measured net capacitance is compared to nominal net capacitance for short/open detection.

Abstract: This invention relates to a process for utilizing the sediments in pure MDI which comprises(a) heating the sediments at temperatures of 180.degree. C. to 250.degree. C. for 0.25 hour to 6 hours in the presence of crude MDI; and(b) cooling the product to a temperature of 60.degree. C. or less within 5 minutes.The sediment-free crude MDI which results can then be used for the preparation of polyurethane products.

Abstract: Highly stable liquid 4,4'-diphenylmethane diisocyanate (MDI) containing MDI-carbodiimide adducts are prepared by heating MDI at a temperature of from 180.degree. C. to 250.degree. C. for a period of from one hour to ten hours in the presence of tris(chloromethyl)phosphine oxide and thereafter equilibrating the adduct formation. Equilibration can occur by any of several methods, i.e., by cooling the composition to a temperature of from 60.degree. C. to 90.degree. C. within twenty minutes, maintaining the composition at this temperature for a period of from one hour to four hours and thereafter cooling the composition to room temperature or by cooling the composition to a temperature less than 100.degree. C. within twenty minutes, further cooling to room temperature, and maintaining the composition at room temperature for one week to two weeks. The resulting compositions have very low sediment contents and are particularly useful in the preparation of microcellular polyurethane foams.

Abstract: Polyurethane foams are prepared employing as the polyisocyanate ingredient a highly stable liquid 4,4'-diphenylmethane diisocyanate (MDI) containing MDI-carbodiimide adducts prepared by heating MDI at a temperature of from 180.degree. C. to 250.degree. C. for a period of from one hour to ten hours in the presence of tris(chloromethyl)phosphine oxide and thereafter equilibrating the adduct formation. Equilibration can occur by any of several methods, i.e., by cooling the composition to a temperature of from 60.degree. C. to 90.degree. C. within twenty minutes, maintaining the composition at this temperature for a period of from one hour to four hours and thereafter cooling the composition to room temperature or by cooling the composition to a temperature less than 100.degree. C. within twenty minutes, further cooling to room temperature, and maintaining the composition at room temperature for one week to two weeks.

Abstract: Highly stable liquid 4,4'-diphenylmethane diisocyanate (MDI) containing MDI-carbodiimide adducts are prepared by (a) heating MDI at a temperature of from 60.degree. C. to 120.degree. C. for a period of from one hour to ten hours in the presence of tris(chloromethyl)phosphine oxide, (b) stopping the carbodiimide formation by adding thereto a quenchant selected from the group consisting of magnesium chloride hydrate, stannous chloride and trichlorosilane, (c) heating the reaction mixture at a temperature between 60.degree. C. and 120.degree. C. for a period of from 0.5 hour to 6.0 hours, and (d) cooling to room temperature. The resulting compositions are highly stable and may be advantageously employed in the preparation of polyurethane compositions.

Abstract: A high voltage/high current circuitry includes a push-pull voltage amplification stage connected in tandem with a parallel connected push-pull current amplification stage. For the voltage amplification stage a pair of bipolar operational amplifiers are connected in parallel and operate in a push-pull manner. A pair of switching means are positioned at the output of each of the bipolar operational amplifiers while the outputs of the amplifiers are connected to the inputs through a current gain regulating means, an isolation means and a voltage divider means.