1. Electrical property.

I have googled and done some reading various paper and found out that either a single walled carbon nanotube or bundles possess lower resistivity.

(SWCNT (semiconducting and metallic mixed) having as low as 10-6 ohm.cm , and MWCNT having 3 x 10-5 ohm.cm)

However, MWCNT is always (most of the time) metallic when SWCNT is only metallic if tubes are set to arm chair direction.

can someone give me explanation for this question?

2. Mechanical property

I think MWCNT having more walls than SWCNT should have higher resistance to bending. However, some paper disagree. I think the main reason may be related to defects. Does MWCNT tend to have more structural defects than SWCNT since the diameter of the wall is larger than SWCNT? Does this also relates to a dispersion issue?

Thanks!