A polymeric substrate is disclosed that comprises a plastic matrix and an inorganic filler dispersed in the plastic matrix, wherein the polymeric substrate exhibits improved OTR and WVTR. The disclosed polymeric substrate may be used in manufacturing of plastic containers, such as plastic bags for containing food products. Preferably, the improved OTR and WVTR of the polymeric substrate contribute to better storage performance of the plastic bags, eg. keeping the food products within the plastic bags from degradation and/or dehydration