if the place that my ex-husband is employed goes on strike is he still required to pay me child support?

So long as there is a standing order, he is required. However, if you would seek to enforce payment and he can show non-payment based on the strike, then he will probably be excused from support payment until his employment begins again.  This is because he did nothing voluntarily to cease his employment and thus avoid payment.  Whether or not he is responsible for the arrearage that would accrue is another question entirely.