Smart manufacturing is the next industrial revolution. The requirements from the manufacturing sector, and more generally, the Industrial Internet of Things (IIoT) has been one of the driving verticals for the design and development of new concepts and technologies. Time Slotted Channel Hopping (TSCH) is one such technology which provides ultra-low power and reliable communication in industrial scenarios. The heart of TSCH is the scheduling algorithm that creates a communication schedule for each node. This paper proposes a fuzzy based priority aware (FPAS) TSCH scheduling technique for scalable industrial IoT networks. The proposed technique supports service differentiation, to improve battery life and reduce latency. The algorithm uses fuzzy logic to determine the priority of a node. The allocation module allocates the required number of slots based on the priority and the amount of traffic generated. The proposed FPAS algorithm is compared with two existing state of the art scheduling functions (SF), scheduling function-zero (SF0) and low latency scheduling function (LLSF). The result shows that FPAS is more scalable than SF0 and LLSF, provides collision free communication and improves duty cycle by 7%, battery life by 28.26%, packet loss ratio by 94% and reduces latency by 74.63% and collisions by 89% respectively.