Abstract: This invention relates to a process for forming a single-layer, durably wettable polymeric web having a plurality of apertures. This process comprises melting a mixture of at least one thermoplastic polymer and at least one migratable surfactant and extruding the mixture to form a single-layer, substantially continuous polymeric film. The film is then apertured using high pressure fluid flows. Aperture formation is conducted when the single-layer polymeric film has a contact angle of at least about 30.degree., to minimize wash-off of the surfactant impregnated in the polymer web. The invention also relates to durably-wettable apertured webs.

Abstract: This invention relates to a process for forming a single-layer, durably wettable polymeric web having a plurality of apertures. This process comprises melting a mixture of at least one thermoplastic polymer and at least one migratable surfactant and extruding the mixture to form a single-layer, substantially continuous polymeric film. The film is then apertured using high pressure fluid flows. Aperture formation is conducted when the single-layer polymeric film has a contact angle of at least about 30.degree., to minimize wash-off of the surfactant impregnated in the polymer web. The invention also relates to durably-wettable apertured webs.

Abstract: A polytetrafluoroethylene (PTFE) porous film is formed from a PTFE resin molding powder obtained by suspension polymerization. The film has a porosity of 40 to 80% and a removal ratio of uniform particles having a diameter of 0.2 .mu.m less than 99%, or has a porosity of 40 to 80% and a bubble point of not less than 3 kg/cm.sup.2. This PTFE porous film is obtained by a process of compression-molding a PTFE resin molding powder to prepare a preform, sintering the preform at a temperature not lower than the melting point of the unsintered PTFE, processing the preform into films, then laminating at least two of the obtained films, fusing the films to unite them, and subjecting the obtained film to uniaxial or biaxial stretching at a temperature not higher than a melting point of the sintered PTFE. If desired, the finally obtained film may be subjected to heat setting. In the PTFE porous film of the invention, pores are nearly round and the diameters of the pores are almost uniform.

Abstract: A fluid mixture separation membrane element (10) includes elongated hollow pressure-resistant nonpermeable transport arteries (12) and a plurality of flexible hollow fibers (14) of semipermeable material having internal flow channels (20). The hollow tubular transport arteries (12) have exteriors (18) and interior flow passages (16). Each hollow fiber (14) has spaced opposite end portions (22, 24) and an elongated tubular portion (26) extending between and interconnecting the opposite end portions (22, 24). The opposite end portions (22, 24) of each hollow fiber (14) are attached by either an adhesive (28) or another suitable mechanism to the tubular transport artery or arteries (12) so as to provide flow communication between the internal flow channels (20) of the hollow fibers (14) and one of the interior flow passages (16) or the exteriors (18) of the hollow transport arteries (12).

Abstract: Objects of the present invention are to provide a membrane filter for liquids which is used in microfiltration or ultrafiltration of liquids such as chemicals, water, and the like and to provide a filtering device using the membrane. The membrane is a membrane filter for liquids which has been rendered hydrophilic, in which the decrease of the pure water permeation flux of the membrane filter after being subjected to wetting treatment with a liquid having a low surface tension, subjected to replacement with pure water, and then exposed to an atmosphere of 25.degree. C. and 60% for 8 hours, to the pure water permeation flux of the membrane filter before the exposure is 20% or less. Such a membrane filter which has been rendered hydrophilic can be obtained by, for example, rendering the surface of a PTFE porous membrane hydrophilic by treating the surface with a low temperature plasma under conditions that a product of high frequency output density and treatment time is from 0.5 to 50 W.multidot.sec/cm.sup.

Abstract: A sandwich of a permeate fabric material within a folded sheet of semipermeable membrane is spirally wound together with a sheet of porous feed pathway material about a mandrel which, upon its removal, provides a central hollow region in the wound element. A single band of adhesive seals the outer end of the envelope, and once wrapping is completed, a thin layer of porous tape holds the winding tight. A porous small diameter tube is inserted into a pocket adjacent the fold in the semipermeable membrane material near the center of the winding and serves as a permeate discharge conduit. Axial ends of the spirally wound subassembly are sequentially potted in resin to complete the basic fabrication of the element. Communication with the feed pathway material is provided by drilling through the resin into the center hollow region.

Abstract: A filtration medium especially useful in cross-flow type filtration systems comprising a length of porous strong substrate, preferably woven, and a thin porous membrane, such membrane being bonded to the strands of the substrate by islands of resin uniformly spaced apart and disposed generally between the substrate and the membrane. The islands of resin enhance the integrity of the composite during its use in a filtration system. A method and apparatus for the manufacture of the filtration medium is disclosed.

Abstract: This invention relates to an improved thermite coated molten metal filter. According to the invention, a molten metal filter is coated with an aqueous thermite coating slurry containing oleic acid, water-miscible surfactants, water-soluble binders, and water-soluble dispersants.

Abstract: A synthetic hydrophilic membrane, and method for manufacturing thereof, in the form of hollow fibers or flat membranes for dialysis and/or ultrafiltration, containing a mixture of polysulfone and sulfonated polysulfone, the mixture containing 65 to 95 wt.% sulfonated polysulfone, possibly as a salt of sulfonic acid, and 35 to 5 wt.% unsulfonated polysulfone. Preferably, up to 12 wt.% water-soluble polymers, based on the total mixture, are added to the mixture of polysulfone and sulfonated polysulfone before formation of the membrane.

Abstract: A membrane for a filter device or a device for gas or liquid separation, the membrane being constituted by a porous structure made of at least one material selected from sintered ceramic, sintered metals, microporous carbon, microporous glass, and polymers, said structure including at least one microporous layer, wherein the entire outside surface and inside surface of the pores of said structure is covered by a thin and continuous film of a polyphosphazene, the thickness of said film lying in the range 0.01% to 10% of the mean diameter of the pores of said microporous layer.

Abstract: A fluid mixture separation membrane element (10) includes elongated hollow pressure-resistant non-permeable transport arteries (12) and a plurality of flexible hollow fibers (14) of semipermeable material having internal flow channels (20). The hollow tubular transport arteries (12) have exteriors (18) and interior flow passages (16). Each hollow fiber (14) has spaced opposite end portions (22, 24) and an elongated tubular portion (26) extending between and interconnecting the opposite end portions (22, 24). The opposite end portions (22, 24) of each hollow fiber (14) are attached by either an adhesive (28) or another suitable mechanism to the tubular transport artery or arteries (12) so as to provide flow communication between the internal flow channels (20) of the hollow fibers (14) and one of the interior flow passages (16) or the exteriors (18) of the hollow transport arteries (12).

Abstract: An asymmetric polymer membrane is disclosed characterized by being formed by irradiating a monomer and/or an oligomer polymerizable with an energy ray and having a pore diameter distribution in the thickness direction of the membrane, a ratio of a permeability flux of oxygen to nitrogen of 0.9-1.1, and communicating pores.

Abstract: Halogen-substitutable hydrogen atoms are linked to nitrogen atoms of a polymer, with ethylenically-unsaturated monomers. By using inorganic or organic hypohalogenites and/or organic N-halogen derivatives as halogenation means, hydrogen atoms on the nitrogen atoms of the polymer membranes or polymer formed materials are replaced by halogen atoms and part of these are removed by reducing agents in the presence of ethylenically unsaturated monomers, with radical grafting of these on to the nitrogen atoms, after which the remaining halogen atoms are removed by reducing agents in the absence of monomers.

Abstract: Normally hydrophobic fluoropolymer porous membranes having continuous pores are rendered hydrophilic by coating the pore interior with a mixture of at least one fluoroaliphatic surfactant and at least one hydrophilic but substantially water-insoluble polyurethane.

Abstract: Semi-permeable microporous polymer bodies, such as porous plates or membranes for separation processes, are provided, these being made of durable high-temperature thermoplastics, e.g., a liquid crystal polymer, by a process comprising melt-mixing the polymer with high loadings of leachable glass and then leaching the glass from the polymer to leave a continuous relict polymer network, the network typically demonstrating pore volumes of 50 percent or more and average pore diameters in the 0.1-10 micron range.

Abstract: The process of making a multilayer membrane composed of a carrier layer, a porous supporting layer and a separating layer includes making a modified polyvinyl alcohol by decomposing a polyvinyl ester or ether until the proportion of the vinyl alcohol monomer units in the modified polyvinyl alcohol corresponds to that in a material consisting of 80 to 95% of the polyvinyl ester or ether and 20 to 5% of a polyvinyl alcohol obtained by completely decomposing the polyvinyl ester or ether; preparing a composite material consisting of the carrier layer and the porous supporting layer, preparing a dilute aqueous solution containing 1 to 10% by weight of the modified polyvinyl alcohol; preferably storing the dilute solution at temperatures from -10.degree. to +10.degree. C., preferably from 0.degree. to 5.degree. C.

Abstract: A composite reverse osmosis membrane composed of a microporous support layer and a thin layer supported thereon, characterized in that the thin layer is made of a crosslinked polyamide which comprises a polyamine component having two or more amino groups in the molecule and an acid component containing a linear aliphatic polyacid halide having two or more halogenated carbonyl groups in the molecule.

Abstract: A process is provided for modifying the properties of a hydrophobic microporous membrane which includes the steps of first providing a hydrophobic microporous membrane, treating it with a surfactant to render the membrane hydrophilic, wetting the membrane with an aqueous solution of a polyol such as polyvinyl alcohol (PVA) and divinyl sulfone (DVS) or a precursor thereof, washing the membrane with water to displace the polyol/DVA from the exterior of the membrane while retaining it in the pores of the membrane, and crosslinking the polyol/DVS into an aqueous gel to yield a hydrophilic microporous membrane having pores filled with an aqueous polyol/DVS gel, the exterior of the membrane being unobstructed by gel. The modified membranes produced according to the process are useful in carrying out chromatographic separations.

Abstract: Improved polymeric membranes and their method of manufacture are disclosed. The improved membranes are produced by increasing the draw ratio employed during the manufacture of the membrane. The membranes show at least substantially constant or increased selectivity and mechanical properties as the draw ratio is increased.

Abstract: A composite membrane and process utilizing the membrane which is capable of selectively removing particles such as viral particles from a solution such as a protein solution is provided. The membrane comprises a porous membrane substrate, a surface skin having ultrafiltration separation properties and an intermediate porous zone between the substrate and the skin which intermediate zone has an average pore size smaller than that of the substrate. The intermediate zone is free of voids which break the skin and which directly fluid communicate with the substrate. The composite is capable of a log reduction value of at least 3 (99.9% removal) of particles selectively from solution.

Abstract: Dopable, fully dense polymer membranes are used to form membranes having selective permeabilities. To improve selectivity, the membranes may be subjected to chemical or electrochemical treatment with electron donors or acceptors to alter the doping level of the polymer membrane, generally in a reversible fashion. This leads to significant changes in gas permeation rates relative to what is observed for the non-doped, fully dense polymers. This change in doping level of the polymer films can be precisely controlled by varying the concentration and nature of chemical dopants used. Desirable changes in permeation rates are achieved by a treatment which comprises a reversal doping of the polymeric material, followed by removal of the dopants (to provide an "undoped" polymer).

Abstract: The present invention is directed to an improved reverse osmosis membrane that shows surprisingly improved solute rejection and permeation properties. The membrane includes a separating layer of a polyamideurethane formed in situ by reaction of a haloformyloxy-substituted acyl haldide with a diamine-treated substrate.

Abstract: In the method of making a filtration unit, envelope-shaped membrane units (62) are placed in a stack, a curable liquid binder (101) is introduced between the membrane units from at least one surface of the filtration unit to a predetermined depth (a), and upon curing of the binder a layer of the binder together with the marginal portions of the edges of the membrane units embedded therein is removed, such as by surface cutting or machining, up to a depth (b) smaller than the depth (a).

Abstract: A porous waterproof film having a superior gas-permeability and waterproofness, capable of being produced under simple processing conditions, by means of simple processing equipments and at cheap cost, having superior mechanical strengths and also suitable for disposable use applications and a process for producing the film are provided, which film is obtained by subjecting a thermoplastic resin composition film comprising a thermoplastic resin and a specified quantity of a filler based on the thermoplastic resin to calender processing.

Abstract: Filter cartridge, in particular with a block-like construction, comprising a plurality of fold walls created by folding in a zig-zag fashion for a medium to be filtered to pass through from one edge area of the zig-zag folding in the direction of the edge area of the folding on the opposite side made of a material which can be permeated by the medium to be filtered provided with offsets formed by roll forming, with those offsets which lie in contact with each other acting as spacers and stiffeners between adjacent fold walls, wherein the offsets of adjacent fold walls which face one another are stuck together.

Abstract: A filter element which is improved in filter performance and suitable for use in various types of filters, and a manufacturing method thereof. In the filter element, a multiplicity of tubes each formed of a filtering material and having a substantially circular shape in cross-section are arranged side by side into a tubular assembly with the axes of the tubes lying parallel to one another; inter-tube openings are closed at one end of the tubular assembly which end serves as the inlet side for a fluid to be filtered, whereas intra-tube openings are closed on the opposite end of the tubular assembly; and the total cross-sectional area of all the inter-tube openings is set smaller than the total cross-sectional area of all the intra-tube openings, but larger than the minimum cross-sectional area of a path through which the fluid is supplied to the tubular assembly.

Abstract: Polymeric affinity membranes comprise a precursor filtration membrane and a plurality of reaction sites provided on the surface of the membrane selective to binding a specific biological material. A process for the preparation of such affinity membranes includes the steps of providing a copolymer compatible with a water insoluble polymer matrix and having a plurality of hydroxyl groups, activating the hydroxyl groups with a compound selected from the group consisting of organic compounds reactive with a hydroxyl group in the presence of a water miscible solvent to provide a derivatized copolymer containing active adducts, forming a solution of the derivatized copolymer and the polymer matrix to form a polymer blend solution, casting the polymer blend solution and, quenching the cast polymer blend solution in water.

Abstract: A method for designing and making composite membranes having a microporous support membrane coated with a permselective layer. The method involves calculating the minimum thickness of the permselective layer such that the selectivity of the composite membrane is close to the intrinsic selectivity of the permselective layer. The invention also provides high performance membranes with optimized properties.

Abstract: A composite chromatographic sheet-like article is prepared by the steps comprising blending one or more non-swellable sorptive hydrophobic particulate materials in the presence of an amount of polar organic masking agent sufficient to allow rapid wetting of the surface of the particulate and in the presence of sufficient lubricant water to exceed the sorptive capacity of the particulate, provided that the volume ratio of water to masking agent does not exceed 3:1, adding with stirring an aqueous emulsion of polytetrafluoroethylene so that the resulting mass has a dough-like consistency, mixing the mass in an intensive mixer at a temperature between 50 C. and 100 C. for a time sufficient to cause fibrillation of the polytetrafluoroethylene particles, biaxially calendering the mass, while maintaining water at a level near the absorptive capacity of the particulate, between a gap in the calendering rolls maintained at about 50 C. to about 100 C.

Abstract: A method for preparation of macroporous polymeric membranes consisting in placing a mixture of monomers and a radical initiator, dissolved in a porogenic inert organic solvent selected from the group comprising alcohols, estes of carboxylic acids, ketones, and their mixtures, into a space of an adapted shape formed by two temperature-controlled plates and a distance insert having the thickness corresponding to the required thickness of membrane and heating up to 80.degree. C. for 24 hours at utmost in order to carry out the radical polymerization. Azo-bis-isobutyronitrile is advantageously used as an initiator in the amount 0.05-2 wt. % related to monomers in the polymerization mixture. Cyclohexanol or its mixture containing up to 20 vol. % dodecanol are advantageously used as a porogenic solvent in the amount 40-60 vol. % in the polymerization batch.

Abstract: Composite breathable film comprising a breathable polyolefin film heat laminated to a nonwoven HDPE fabric. Preferably, the breathable film is prepared by melt embossing a highly filled polyolefin film to impose a pattern of different film thickness therein, and stretching the embossed film. The nonwoven fabric is made by cross-laminating HDPE fibers at the crossing points to form a thin open mesh fabric, and coextruding a heat seal layer thereon. The composite is made by heat laminating the breathable film to the heat seal layer of the fabric. The resulting laminate has excellent water vapor transmissibility, air resistance and strength and is particularly adapted for use as a housewrap.

Abstract: A method of producing a filter for separating solid particles, whose diameters are generally smaller than 5 .mu.m, from flowing gases or liquids. A covering layer with columnar and/or platelet-shaped oxides is formed on a body consisting of porous steel foil at least in and around the pores.

Abstract: Composite membranes are disclosed having a separation layer comprised of a mixture of poly(methy methacrylate) or a copolymer thereof and at least one cellulosic derivative resulting in enhanced separation and permeating characteristics of the overall composite membrane. Processes for making these composite membranes and the methods of using them are also disclosed. The membranes are particularly useful in gas separation applications and are most suited for the separation of hydrogen from a hydrogen containing stream.

Abstract: A crosslinked composite membrane having high permeation velocity and sepaion factor and a process for producing the same. The membrane comprises a skin layer comprising a crosslinking reaction product of a water-soluble polysaccharide having a sulfonate group and/or a sulfonic acid group and a polyfunctional melamine compound the crosslinked composite membrane can be formed on a porous base such as an ultrafilter.

Abstract: An improved composite polyamide membrane and methods of making the membrane are described. This improved membrane is prepared using a cationic polymeric wetting agent in an aqueous solution containing a polyfunctional amine reactant which is interfacially polymerized with an acyl halide to form a thin film polyamide discriminating layer on a microporous support. Alternatively, the wetting agent can be applied directly to the substrate and the interfacial polymerization can occur on said treated substrate. The resulting membrane exhibits an unexpected combination of high water flux, high rejection of divalent anion salts, variable sodium chloride rejection and good caustic resistance at low operating pressures. In one embodiment of this invention, a porous substrate is first treated with an aqueous piperazine solution containing a copolymer of vinylbenzyl dimethyl sulfonium chloride and methacrylic acid and then the coated microporous support is contacted with trimesoyl chloride in an organic solvent.

Abstract: An anisotropic elastomeric membrane preferably made from polyurea/urethane has been prepared. These anisotropic membranes are made from the corresponding polymeric material by preparing the polymeric material in a good solvent containing less than 5 vol % non-solvent, producing a film of the polymer solution on a support with a maximum pore size less than 20 microns, subjecting the film to conditions such that the solvent vapor pressure-time factor is 1000 mm Hg-min. or less, preferably 200 mm Hg-min or less, most preferably approaching 0 mm Hg-min and quenching the membrane film in a non-solvent yielding a three-layered anisotropic membrane.

Abstract: A supported microporous membrane comprising a composite of a microporous membrane and a synthetic thermoplastic web of microfibers secured to the membrane without the use of added adhesive components and having an ASTM D903 peel strength of at least about 2 grams per centimeter, the composite having a modulus of flexure at leasts 10 percent greater than that of the membrane, and the method of manufacturing such supported membranes by contacting thermplastic microfibers with the membrane while the microfibers are at an elevated temperature.

Abstract: A method of manufacturing an integral asymmetrical membrane for the separation of liquid or gaseous mixtures. A membrane-forming agent in the form of a polyetherimide is mixed with a solvent that is miscible with water. The resulting mixture is introduced into or accommodated in a geometrical form. The form is then brought into contact with a precipitating agent and is post-treated.

Abstract: There is provided a method of manufacturing cellulose membranes with pore radii less than 30.times.10.sup.-10 m, suitable for reverse osmosis applications. The method comprises dissolving a cellulosic material in a DMSO/PF solvent at a temperature about 125.degree. C. for about 90 min., cooling and casting the solution at room temperature, evaporating the solvent at a temperature of 140.degree.-180.degree. C. and gelling the resulting membrane in a protic solvent, e.g. ethanol or water.

Abstract: A separation membrane having cell sizes in the range of 0.1 to 10 microns, prepared by:mixing at least one linear alternating polymer of carbon monoxide and at least one ethylenically unsaturated hydrogen in a solvent forming a solution;casting said solution on a substance, andremoving at least a portion of said solvent.

Abstract: The present invention provides for a process for transforming a substantially continuous web of substantially planar, deformable material having an indefinite length, a first surface, and a second surface into a formed material. The material has a transformation temperature range. The process comprises the following steps:(a) The web of material is provided on a forming structure with the first surface of the web of material proximate a forming surface of the forming structure. The forming surface moves in a direction of the length of the web of material and carries the web of material in that direction.(b) A liquid stream is applied to the second surface of the web of material. The liquid stream has sufficient force and mass flux to cause the web of material to be deformed toward the forming surface, such that the material acquires a substantial three-dimensional conformation.

Abstract: A microfiltration membrane is made up dissolving m-phenylenediamine-isophthalic acid copolymer, a high temperature aromatic polyamide, in one or more solvents selected from the group which consists of N-methylpyrrolidone, dimethylformamide and dimethylacetamide, and the resulting solution in the presence of two or more of these solvents, a structure-loosening agent such as water or a polyhydric alcohol, is cast. After gel formation in the film, the latter is washed free from solvents and dried. The microfiltration membrane has high bursting strength and a pore point of 0.05 to 10 microns and a high permeability.

Abstract: An aromatic polyimide separating membrane is produced by a process comprising the steps of:forming a thin film of a dope solution containing an aromatic polyamic acid dissolved in a polar organic solvent at a temperature of approximately 100.degree. C. or less;coagulating the thin dope solution film in a coagulating liquid containing at least 60% by volume of at least one member selected from water and lower aliphatic alcohols at a temperature of 60.degree. C. or less;drying the resultant coagulated aromatic polyamic acid membrane; andheating the dried aromatic polyamic acid membrane at a temperature of 100.degree. C. to 300.degree. C. to convert it to an aromatic polyimide membrane.

Abstract: A polyimide semipermeable membrane is prepared by the process comprising the steps of:preparing a solution of a polyimide material consisting essentially of at least one aromatic polyimide comprising at least 90 molar % of at least one recurring unit of the formula (I): ##STR1## wherein R represents a divalent aromatic radical, in a solvent consisting of at least one phenol compound in the state of a liquid or melt;forming a thin layer of the polyimide solution, and;coagulating the thin layer of the polyimide solution by bringing the thin layer into contact with a coagulating liquid to form a semipermeable membrane.

Abstract: An expandable vinyl chloride resin composition for foaming under atmospheric pressure which comprises a resin ingredient comprising (A) a vinyl chloride homopolymer or copolymer having substantially no active hydrogens, (B) a vinyl chloride copolymer having active hydrogens and (C) a thermoplastic polyurethane resin, and a crosslinking agent, a foaming agent, a thermal stabilizer and a plasticizer, the ratio of the components (A), (B) and (C) being 30 to 90:5 to 40:5 to 40 by weight. The composition is expanded under atmospheric pressure to give a foam of a high expansion ratio which has uniform and fine cells and shows an excellent rubber-like elasticity.

Abstract: Ethylene-vinyl alcohol copolymer membranes characterized by constituent particles having an average diameter within the range of from 100 to 10,000 Angstrom units, determined under an electron microscope for the dry membrane, bonded to each other, wherein the membrane is substantially free from pores in excess of from 2 microns in diameter.Such a membrane has a permeability to water of 10 to 200 .times. 10.sup.-16 cm.sup.2 and to vitamin B.sub.12 of not less than 0.8 .times. 10.sup.-7 cm.sup.2 per second, and being of particular value as a membrane for the dialysis of blood.The membrane is obtained by dissolving an ethylenevinyl alcohol copolymer in a solvent consisting essentially of dimethylsulfoxide or dimethylacetamide and causing the resulting solution to coagulate from an aqueous coagulation bath under mild conditions such that the coagulation time as defined in the specification is not less than 3 seconds.

Abstract: There is described the preparation of hydrophilic, semi-permeable film membranes having an increase in pores and containing complex-forming metals. The films can be formed from solutions having film-forming material and pore-forming material dissolved in a solvent. The films can be useful for separating a component, e.g. an aliphatically-unsaturated hydrocarbon, from mixtures by the combined use of liquid barrier permeation and metal complexing techniques. The liquid barrier is at least partially within the hydrophilic film membrane during use, and the barrier contains complex-forming metal ions in aqueous solution. The metal ions may be, for example, noble metal, nickel, mercurous, cuprous or other metal ions, and mixtures of these metal ions, and the aqueous solution may contain other cations. The separation of ethylene from ethane and methane is of particular interest.

Abstract: A dimensionally stabilized microporous polyamide membrane having enhanced flow characteristics comprised of a film forming organic polymeric material of low shrinkage prepared by drying the membrane, under conditions of restraint in the plane of the membrane to minimize the shrinkage until the membrane is essentially in a dried condition. A process is also described for preparing a microporous membrane designed to enhance incorporation and retention of a charge modifying resin for use as a charge modified filter media. The process comprises preparing a dope solution of a film forming polymer in a solvent system, directly casting the solution under the surface of a quenching medium comprising a non-solvent system for the polymer for a time sufficient to form micropores in the film, and drying the film while controlling the planar dimensions of the film during the drying.