Compositions and processes for preparing extrudable powder blends containing at least one vinyl chloride resin and a cellulosic material are provided. More specifically, compositions and processes for preparing extrudable free-flowing powder blends containing PVC and wood flour (WF) are also provided for preparing foamed or nonfoamed extrudates. The processes provided herein incorporate components which may contain up to a total of 25 weight percent water. Processes for preparing foamed extrudates are also provided wherein a cooling fluid is used to increase the expansion ratio of the foam. Finally provided are composites having an extrudable thermoplastic substrate and at least one capstock layer disposed thereon containing a PVC/WF composition.