The same method as used for water absorption could not be used for oil absorption, as oil cannot be efficiently wiped off prior to weighing. Instead, oil absorption was determined by using 24-ply all-PP laminates consolidated at 145 °C at 4 MPa pressure in a hot press, with and without PP copolymer sheets on the laminate faces. The oil absorption was determined by measuring the change in buoyant force. According to the Archimedes principle, the buoyant force of a solid less dense than the fluid in which it is immersed, is equal to the weight of the volume of fluid it displaces when submerged, less the dry weight of the object. Fluid absorbed by the solid lowers the buoyant force by reducing the volume of fluid actually displaced. Hence as the buoyant force decreases, the apparent weight of the solid in the oil, moil, increases and this variation of weight of the immersed solid is equal to the weight of the oil absorbed. The weight of oil absorbed can be practically determined by using a standard density measuring apparatus attached to a microbalance. The oil absorbed in weight percent is derived from the following expression
The same method as used for water absorption could not be used for oil absorption, as oil cannot be efficiently wiped off prior to weighing. Instead, oil absorption was determined by using 24-ply all-PP laminates consolidated at 145 °C at 4 MPa pressure in a hot press, with and without PP copolymer sheets on the laminate faces. The oil absorption was determined by measuring the change in buoyant force. According to the Archimedes principle, the buoyant force of a solid less dense than the fluid in which it is immersed, is equal to the weight of the volume of fluid it displaces when submerged, less the dry weight of the object. Fluid absorbed by the solid lowers the buoyant force by reducing the volume of fluid actually displaced. Hence as the buoyant force decreases, the apparent weight of the solid in the oil, moil, increases and this variation of weight of the immersed solid is equal to the weight of the oil absorbed. The weight of oil absorbed can be practically determined by using a standard density measuring apparatus attached to a microbalance. The oil absorbed in weight percent is derived from the following expression
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