Finding frictional force on a particle on an turntable with constant angular acceleration

Question

A flat button of mass m lies on a horizontal turntable (of negligible mass) at a distance r from the centre of the turntable. The turntable rotates at constant angular speed ω and the button does not slip. The coefficient of the static friction between the turntable and the button is µ.

The turntable then experiences constant angular acceleration of α i.e. no longer spinning at a constant rate. If the button is a distance r from the centre of the turntable and doesn't slip off, how would we find the total force of static friction acting on the button?

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