A dispenser (10) for dispensing flowable materials has a container assembly (12) having a dividing wall (19). A first chamber (18) and a second chamber (20) are defined in the container assembly (12). The first chamber (18) is configured to contain a first flowable material (M1) (140) and the second chamber (20) is configured to contain a second flowable material (M2) (142). A membrane (34) is positioned in the container and cooperates with the dividing wall (19) to enclose the first and second chambers (18, 20). The membrane (34) has a first section (132) having a first weld seam (148) and a second section (134) having a second weld seam (150). The first section (132) is separated from the second section (134) by a non-rupturable member (33). Rupture of the membrane (34) allows the flowable materials into a third chamber (42) in which the flowable materials mix to form a mixture, and from which the mixture is dispensed.