CB/WPU导电复合材料在有机蒸汽中的气敏响应特性初探

采用乳液共混法制得了炭黑／水溶性聚氨酯（CB／WPU）气敏导电复合材料。复合材料在饱和溶剂蒸汽中的最大响应随着溶剂的介电常数的增大而减小。在非极性饱和溶剂蒸汽中，没有观察到负蒸汽系数（NVC）效应，其最大电阻响应达到106倍以上；而在极性饱和溶剂蒸汽中，经过一段时间之后，复合材料的电阻将接近于一个平衡值，该平衡值的大小随着溶剂的介电常数的增加而减小，溶剂本身的导电件是导致CB／WPU复合材料在极性饱和溶剂蒸汽中出现NVC效应的主要原因。而在非饱和蒸汽中，复合材料在低压纯蒸汽条件下的最大响应高于在低压蒸汽和空气？昆合气氛条件下的最大响应，复合材料存低压纯蒸汽下没有NVC效应；然而在低压蒸汽和空气混合气氛中，复合材料在极性和非极性溶剂蒸汽中均存存NVC效应．这主要是由于复合材料吸收溶剂蒸汽后，环境压力诱导聚氨酯链段结构松弛引起的。

Sensing Characteristics of Carbon Black/Waterborne Polyurethane Composites in Organic Solvent Vapors

Conducting composites from waterborne polyurethane(WPU) and carbon black(CB) were prepared by latex blending.When the composites were exposed to saturated vapor,maximal responsivity of the composites decreased with increasing dielectric constant of solvent.In addition,the maximal responsivity of the composites against non-polar saturated vapors were higher than 10~6,and the negative vapor coefficient(NVC) phenomenon was not observed.When the composites were exposed to polar saturated solvent vapor for a period of time,the electrical resistance approached to an equilibrium value that decreased with a rise in the dielectric constant of the solvent.It is believed that NVC phenomena in polar saturated vapor mainly result from the conductivity of solvent.When the composites were exposed to unsaturated solvent vapor,the maximal responsivity in low pressure pure vapor was higher than that in the mixture of low pressure vapor and air.No NVC phenomenon was observed when the composites were exposed to low pressure pure vapor.Meanwhile,NVC phenomenon would appear as exposing to the mixture of low pressure vapor and air,both for polar vapor and non-polar vapor.The NVC phenomena of the CB/WPU composites in unsaturated solvent vapors may be due to the relaxation of the matrix segments.