A hollow fiber membrane is formed by embedding a braid having a spiral open weave of monofilaments only, to avoid a whiskering problem. The open weave is characterized by contiguous, circumferential, rhomboid-shaped areas of polymer film separated by monofilaments. When the braid is supported on a plasticized PVA cable having a scalloped periphery, the braid can be infiltrated with membrane polymer which, when coagulated, embeds the braid positioning it around the lumen. The embedded spiral weave, free of any circumferentially constricting monofilament, allows the membrane to be biaxially distensible. The membrane has give not only in the axial or longitudinal direction but also in the radial direction. Give in the radial direction permits soiled membranes to be backwashed under higher pressure than in a comparable braid which is not radially distensible.

Polymer composition comprising a thermoplastic polyester having at least one 1,4:3,6-dianhydrohexitol unit (A), at least one alicyclic diol unit (B) other than the 1,4:3,6-dianhydrohexitol units (A), at least one terephthalic acid unit (C), wherein the ratio (A)/[(A)+(B)] is at least 0.05 and at most 0.75, said polyester being free of non-cyclic aliphatic diol units or comprising a molar amount of non-cyclic aliphatic diol units, relative to the totality of monomeric units in the polyester, of less than 5%, and with a reduced viscosity in solution (25? C.; phenol (50 wt. %):ortho-dichlorobenzene (50 wt. %); 5 g/L of polyester) greater than 70 mL/g; as well as an additional polymer selected from aromatic polyesters, aliphatic polyesters, polyester ethers, polyamides, polycarbonates, polyether block amides and polyurethanes.

A hollow fiber membrane is formed by embedding a braid having a spiral open weave of monofilaments only, to avoid a whiskering problem. The open weave is characterized by contiguous, circumferential, rhomboid-shaped areas of polymer film separated by monofilaments. When the braid is supported on a plasticized PVA cable having a scalloped periphery, the braid can be infiltrated with membrane polymer which, when coagulated, embeds the braid positioning it around the lumen. The embedded spiral weave, free of any circumferentially constricting monofilament, allows the membrane to be biaxially distensible. The membrane has give not only in the axial or longitudinal direction but also in the radial direction. Give in the radial direction permits soiled membranes to be backwashed under higher pressure than in a comparable braid which is not radially distensible.

A hollow fiber membrane is formed by embedding a braid having a spiral open weave of monofilaments only, to avoid a whiskering problem. The open weave is characterized by contiguous, circumferential, rhomboid-shaped areas of polymer film separated by monofilament. When the braid is supported on a plasticized PVA cable having a scalloped periphery, the braid can be infiltrated with membrane polymer which, when coagulated, embeds the braid positioning it around the lumen. The embedded spiral weave, free of any circumferentially constricting monofilament, allows the membrane to be biaxially distensible. The membrane has give not only in the axial or longitudinal direction but also in the radial direction. Give in the radial direction permits soiled membranes to be backwashed under higher pressure than in a comparable braid which is not radially distensible.

A hollow fiber membrane is formed by embedding a braid having a spiral open weave of monofilaments only, to avoid a whiskering problem common in prior art multifilament braid-supported tubular membranes. The open weave is characterized by contiguous, circumferential, rhomboid-shaped areas of polymer film separated by monofilaments. When the braid is supported on a plasticized PVA cable it can be infiltrated with membrane polymer which, when coagulated embeds the braid positioning it around the lumen. The spiral weave, free of any circumferentially constricting monofilament, when embedded in film, allows the membrane to be biaxially distensible. In other words, the membrane has give not only in the axial or longitudinal direction but also in the radial direction. Give in the radial direction permits soiled membranes to be backwashed under higher pressure than in a comparable braid which is not radially distensible.