Union workers at the CSL Behring plant in Bradley are expected to rally at about 7 a.m.
More than 700 workers walked off the job at 11 p.m. Wednesday.
CSL Behring is a global pharmaceutical company. They manufacture, in part, medications for bleeding disorders and immune deficiencies.
The plant in Bradley is the second largest employer in Kankakee County with a total workforce of 1,500.
Union members said the key point of deep concern regards the outsourcing of jobs from CSL union workers to third party contractors.
The president of Local 498C said this is about job security.
The timing of the strike marks the official end of a three-year contact.
Meanwhile CSL Behring company officials said they offered workers pay hikes and other competitive benefits.