Abstract: This invention relates to preparation of polyamide-imide foam by extruding foamable composition comprising polyamide-imide and volatiles into a confined expansion zone, expanding the composition therein and cooling the result. The resulting foams are essentially open-celled and exhibit good strength, insulating properties and other desirable features.

Abstract: A sealing gasket of foamed plastic is formed at the edge of a filter element of reticulated foam by placing the filter element on a surface adjacent to an open receptacle contoured as a mold for the desired shape of the gasket, filling the receptacle with a foam-forming liquid and avoiding contact between the liquid and the filter element until the liquid begins to froth. The liquid is then permitted to froth and overflow the receptacle on the side facing the filter element. As the froth contacts the filter element and proceeds to cure, it bonds to the edge of the elements without substantially penetrating its open pore network. The result upon curing is a gasket along the edge of a filter element fully bonded thereto without gaps or bypass, yet leaving substantially all of the surface area of the filter element exposed for use as a filter.

Abstract: Continuous molding apparatus includes a raw material supplying portion, a molding portion, a supporting portion, a mixing portion and a control portion. Each reservoir of the raw material supplying portion is connected independently with the mixing portion. The molding portion includes a plurality of spaced mold assemblies each with at least two separable mold sections. The supporting portion includes a plurality of the spaced mold assemblies each supported for independent rotation about more than one axis. The mixing portion includes an elongated mixing chamber disposed adjacent each mold assembly each with a plurality of deflector sections. A continuous method of molding a foamed product includes providing a plurality of raw material reservoirs and continuously moving raw material from each reservoir independently to a plurality of spaced mixing chambers each of which is located adjacent to an individual mold assembly including separable mold sections.

Abstract: A process for producing a foamable thermoplastic resin article having a relatively thin non-foamed outer shell with a smooth surface and a foamed core portion, which has excellent dimensional stability, by pressurizing a mold cavity under a pressure of gas less than the foaming pressure and not less than the surface smoothing pressure of the foamable resin and permitting the pressure of the gas simultaneously with completion of the injection to be communicated to an atmospheric pressure or lower.

Abstract: High flux semipermeable membranes which comprise a polymerized reaction product within and/or on a porous support may be prepared by contacting the porous support such as a polysulfone sheet with an aqueous solution of an polyamine, said aqueous solution containing a polar aprotic solvent not reactive with amines and optionally an acid acceptor. The surface of the coated support is dried to the touch and then contacted with an organic solution of an polycarboxylic acid halide for a period of time sufficient to form a polymerized reaction product within and/or on the surface of the support material. The resulting composite may be post treated by washing with an alkaline compound. The resultant membrane composite may be used in separation processes such as the desalination of brackish or seawater, or the softening of domestic hard water.

Abstract: The present invention relates to an interfacially synthesized reverse osmosis membrane useful for the separation of fluid mixtures and solutions. In particular, the present invention relates to a polyamide water permeable membrane containing a monomeric amine salt therein, which is useful for desalination of an aqueous solution. The present invention also relates to processes for preparing the membrane.

Abstract: Fiber reinforced thermoplastic integral skin foams of density 50-500 kg/m.sup.3 have an outer skin 0.05 to 1.5 mm in thickness and contain from 2 to 60% by weight of reinforcing fibers.

Abstract: A multilayer inorganic porous membrane consisting of a monolayer or multilayer porous support having at least one surface integrally formed thereon with a porous thin layer having an average pore size less than that of the porous support, wherein a maximum pore size in the support surface is defined to be from 1 to 250 times an average pore size of the thin layer. The multilayer porous membrane is superior in preventing the occurrence of pin holes and cracks therein thereby to enhancing precision of the filtration and separation.

Abstract: A modified microporous membrane comprising an organic polymeric microporous membrane having microporous surfaces and having hydroxyl, mercapto, carboxyl, or amino functionality on the surfaces modified by a reactive modifying polymer having a polymer chain and having along the polymer chain epoxy or epithio functional groups capable of reacting with the functionality on the surface of the membrane and terminal neutral chemical functionality. The preferred reactive modifying polymer is made from a free radical polymerization of:(a) a polymerizable compound containing an epoxy or epithio group capable of direct covalent coupling to the surface functionalities of the microporous membrane and a vinyl group capable of free radical polymerization; and(b) ##STR1## wherein R.sub.1 is an alpha, beta ethylenically unsaturated polymerizable radical of two or three carbon atoms;R.sub.2 is an alkyl substituent of two to five carbon atoms having a terminal hydroxyl functionality or (R.sub.3 O).sub.n H,wherein R.sub.

Abstract: A process for the production of optionally foamed moldings having a compact surface by the reaction in closed molds of a mixture of(a) organic polyisocyanates,(b) compounds containing isocyanate-reactive groups and having a molecular weight of 62 to about 10,000 and(c) mold release agents based on salts of (i) saturated or unsaturated aliphatic or cycloaliphatic carboxylic acids or carboxylic acid mixtures containing (on a statistical average) at least 8 carbon atoms per molecule and (ii) tertiary amines,characterized in that the release agents (c) used are salts in which the amine component (ii) is based on tertiary monoamines or mixtures of tertiary monoamines corresponding to the following formula ##STR1## in which R.sub.1 represents a saturated or unsaturated aliphatic hydrocarbon radical containing at least 12 carbon atoms and R.sub.2 and R.sub.

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: A film having a porous core layer and nonporous outer layers is made from a composition of certain polymers, particularly ethylene polymers, a particulate filler which has little affinity for the polymer, and optionally an organic compound which decreases the tendency for affinity of the particulate for the polymer. The film is produced by extruding the composition through a die gap of at least 250 .mu.m, and subsequently stretching the film after cooling to a temperature below the melting temperature of the polymer.

Abstract: A method of making a solid core locatable between a wheel rim and a tire fitted to the rim, includes introducing a foamable composition into a mould cavity having a substantially inflexible mould surface. The cavity is suitably shaped so that a core locatable between a wheel rim and a tire fitted to the rim can be moulded therein. The composition is allowed to foam, thereby to fill the mould cavity. Air and excess composition is allowed to vent from the cavity via an elongate vent slit extending along a major portion of the cavity. The foamed core thus moulded in the cavity is removed from the cavity on the composition having set at least partially.

Abstract: Seamless hollow-bodied objects of expanded polystyrene are made by a method in which polystyrene material in bead form is agglomerated about a solid removable core in a split mold. The mold halves are opened and the solid core is removed, leaving at least two preliminary sections in contact with the mold halves. The mold is reclosed, and an inflatable core is inserted and inflated to desired dimensions. The inflatable core is supplied with steam for its inflation and the polystyrene heating is completed. After deflation and removal of the inflatable core and opening of the mold halves, there is obtained a desired seamless hollow article having smooth surfaces inside and out.

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: The present invention relates to an interfacially synthesized reverse osmosis membrane useful for the separation of fluid mixtures and solutions. In particular, the present invention relates to an aromatic polyamide water permeable membrane containing an amine salt therein, which is useful for desalination of an aqueous solution. The present invention also relates to processes for preparing the membrane.

Abstract: A method for producing articles of polyurethane or the like wherein a mold of the article shape is positioned to centrifugally receive a polyurethane composition comprising polyisocyanates, polyol, water and fluorocarbons such that the polyurethane molecules striking the wall of the mold are broken to provide a resulting smooth non-porous outer skin for the article and wherein additional polyurethane materials provide a foamed interior for the article. The water serves as a reactive polyol and reacts with the polyisocyanate to create carbon dioxide gas which yields increased expansion pressure which causes the foaming polymer to produce a uniform skin around a cellular inner core.

Abstract: There is disclosed a one-piece short distance golf ball which is formed by foam molding a thermoplastic polymer and a filler. The resulting golf ball has a dense outer skin and a cellular core structure. The golf ball is approximately half the weight of and plays approximately half as far as a conventional golf ball, but its performance characteristics are otherwise comparable to a conventional golf ball. In addition a bramble surface pattern is provided on the ball to reduce the effects of wind on the ball's flight.

Abstract: According to a method of manufacturing a foamed polypropylene resin sheet of this invention, a composition comprising as a resin component a mixture of 80 to 20 wt % of a crystalline propylene-ethylene block copolymer containing 20 wt % or less of ethylene and having a melt index (MI) of 2 or less and 20 to 80 wt % of a crystalline propylene-ethylene block or random copolymer containing 5 wt % or less of ethylene and having an MI of 6 to 20 or a polypropylene homopolymer having an MI of 6 to 20 is used. A pair of molding roll dies is horizontally arranged at a point separated from the center of an apex of an extrusion foaming die when a foamed sheet is to be extrusion-molded. A distance between the center of the roll and the apex of a base lip is set to fall within a range of (R.sup.2 +25).sup.1/2 to (R.sup.2 +144).sup.1/2 where R is a radius of the molding roll die.

Abstract: A hollow fibre of polyester-amide, useful in the process of dialysis and in ultra-filtration processes in general, is formed by a polyester-amide with repetitive units (TATE).sub.n (wherein T is the terephthalic acid radical; A is the ethylenediamine radical; and E is the hexanediol radical).Such a fibre is obtained by a process which comprises the following steps, carried out sequentially:preparation of a solution of polyesteramide (TATE).sub.n in a solvent constituted by formic acid at a concentration higher than about 99%, or constituted by a solution of lithium chloride in dimethylformamide or dimethylacetamide;extrusion of said solution through a spinnerette having a cross section of annular shape and coagulation of the fibre in an aqueous coagulation bath, with the possible introduction of an aqueous coagulating liquid to the interior of the annular opening of the spinnerette;washing with water and recovery of the so-obtained hollow fibre.

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 method for manufacturing a plastic foam, wherein a plastic compound with chemical foaming agent is charged in molding cavity which is defined by a pair of upper and lower die cavities and wherein the plastic compound is subject to a dielectric heating, so that the chemical foaming agent decomposes. One of the cavity surfaces is movable to vary the volume of the molding cavity in accordance with the expansion of the plastic compound, so that the movable cavity surface is kept in contact with the plastic compound which expands during heating.

Abstract: The invention provides a process and apparatus for producing an injection moulding of plastics material.

Abstract: The invention relates to polyolefin foams consisting of polyolefins of ultrahigh molecular weight, i.e. weight-average molecular weight from about 4.times.10.sup.5 to 6.times.10.sup.6 g/mol and higher, and to a novel process for producing these foams by foaming a solution of a polyolefin of ultrahigh molecular weight in a solvent with the use of a physical or chemical blowing agent or of an inert gas blown into the solution, and cooling of the resulting foam to a temperature below the gelling temperature of the polyolefin. If appropriate, these foams can be provided wholly or partially with a smooth skin on their surface by superficial cooling, if appropriate under the action of pressure.

Abstract: A method of making a foam pig having a highly textured and tough surface for use in cleaning the interior wall of a pipe line, the pig being formed by heating a metallic mold which defines the exterior configuration of the pig, injecting urethane base foam mixture into the heated mold, and curing the injected urethane foam before removing the cured pig from the mold. The mold should be heated to a temperature sufficient to produce a tough surface texture on the completed pig defined by closely spaced indentations of about one-half to three millimeters in depth, the indentations being formed by bubbles in the urethane foam base mixture on the surface of the mold.

Abstract: A process for producing polyurethane foam articles is described, in which the article is produced in the conventional manner by foaming in a mould and a release agent is applied to the mould surface prior to filling with the foam-producing components. According to the invention, a solvent-free, aqueous release agent is used in combination with one or more alkali metal and/or ammonium salts of higher fatty acids and one or more higher alcohols and the combination is applied in the hot state, preferably at a temperature of at least 75.degree. C. to the mould surface. In addition, an additive is described, which is suitable for performing the process according to the invention and contains one or more alkali metal and/or ammonium salts of higher fatty acids, one or more higher alcohols and otherwise water.

Abstract: This invention concerns cosmetic applicators for low-viscosity liquid cosmetics. In particular, it relates to an applicator surface consisting of a latex foam having a combined structure including closed cells and open cells. The structure has a porosity for the open cell portion increasing from the area adjacent the closed cells toward the other side of the latex foam applicator. The latex foam can be natural or acrylonitrile-butadiene latex foam.

Abstract: A plastic pipe with a hard outer shell lined with an inner shell of soft resilient plastic foam with a smooth central axial passageway adapted to be a conduit for liquid. A method of manufacturing this pipe which comprises simultaneously extruding the material for the outer shell and the foamable material for the inner shell into a pipe forming die.

Abstract: Elastic molded articles having a closed surface layer are made from polyurea elastomers by the reaction injection molding technique. These polyurea elastomers are prepared from a polyisocyanate in which all of the isocyanate groups are aromatically bound, a polyether and a diamine. The polyether has at least two isocyanate-reactive groups and a molecular weight from 1800 to 12,000. At least 50% of the isocyanate-reactive groups in the polyether are pjrimary and/or secondary amino groups. The diamine has a molecular weight from 108 to 400 and primary and/or secondary aromatically bound amino groups. Known auxiliary agents and additives may also be employed.

Abstract: Method for obtaining a plastic water-heater body, wherein(1) a plastic shell is used which is intended to form the interior of the water heater and also serves as an internal molding wall, the said shell having at least one orifice,(2) the said shell is positioned inside a mold consisting of two parts, while providing a space between the outside of the shell and the inside of the mold, the mold having an opening,(3) water is introduced into the internal shell via the said orifice,(4) a liquid mixture consisting essentially of a polyester resin composition capable of foaming and polymerizing is cast via the said opening of the mold, by cooling the outside of the mold to a temperature of approximately 10.degree. to 15.degree. C. during casting of the resin, so as to obtain a skin effect on the surface of the foam which comes into contact with the mold during polymerization of the said foam, by controlling the temperature of the expanding and polymerizing resin so that it does not exceed approximately 40.degree.

Abstract: A method of making a foam injection molded article is disclosed wherein corrosion of the mold element is significantly reduced or substantially eliminated. The method comprises dispersing effective amounts of a primary chemical blowing agent of sodium borohydride and an activation system of sodium bicarbonate/citric acid mix into a polymer resin to form a mixture. The mixture is then heated whereby the activation system releases water and the sodium borohydride reacts with the water to produce hydrogen gas. The mixture is subsequently injected into a mold to obtain expansion of the polymer resin to form the foam article. The invention also comprehends a corresponding chemical blowing agent composition.

Abstract: A process for preparing a polyurethane foam handle having a woodgrain finish is disclosed, which comprises injecting a composition comprising a polyol, a polyisocyanate, a crosslinking agent, a catalyst, a foam stabilizer and a blowing agent into a mold having a shape of a handle, blowing and curing the composition and applying a woodgrain finish coating on the formed handle. In this process, a polyol comprising 50 to 100 parts by weight of a polyether polyol having at least two OH groups in the molecule and having a molecular weight of 1,000 to 10,000 and 0 to 50 parts by weight of a polymer polyol having a hydroxyl number of 20 to 50, which is formed by graft-polymerizing a vinyl compound onto a polyether polyol, is used as the polyol, and 10 to 30 parts by weight of a polyol having 2 to 4 OH groups in the molecule and having a hydroxyl number of 800 to 2,000 is used as the crosslinking agent.

Abstract: An integral foam body has a body part composed of an extruded hard thermoplastic material with a plurality of staple fibers of high tensile strength embedded in the thermoplastic material.

Abstract: The present invention is directed to the continuous production of microcellular plastic web material having integral unmodified laminar skin. In accordance with the invention a web of plastic material impregnated with an inert gas is delivered continuously to a degassing device in which the degree to which gas diffuses out of the surfaces of the web can be selectively and continuously controlled, whereupon the web enters a foaming station where it is reheated to induce foaming. The temperature of the reheated web and the duration of the foaming process prior to quenching are also selectively controllable to produce the desired web characteristics.

Abstract: The present invention is directed to a process for the production of optionally foamed polyurethanes which are combined or fabricated with another material, comprising reacting compounds with molecular weights from 400 to 10,000 containing at least 2 isocyanate reactive hydrogen atoms with polyisocyanates in the presence of catalysts containing tertiary amino groups and combining or fabricating the resulting polyurethane with another material, characterized in that the catalysts used are diffusion resistant aminoalkanols corresponding to the general formula ##STR1## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 may be identical or different and represent hydrogen or a C.sub.1 -C.sub.6 alkyl group,R.sup.5, R.sup.6, R.sup.7 and R.sup.8 may be identical or different and represent a C.sub.1 -C.sub.6 alkyl group or together form a C.sub.2 -C.sub.6 alkylene group which may contain hetero atoms such as O or NR (R=C.sub.1 -C.sub.4 alkyl), and n and m may be identical or different and represent integers from 1 to 6.

Abstract: A molded structural panel with substantially parallel major surfaces includes integrally formed thin thermosetting resin high density outer sections. Less dense thermosetting resin foam intermediate sections extend inwardly from the outer sections with the density of the intermediate sections decreasing substantially uniformly with increased spacing from the outer sections. A thin thermosetting resin high density central section is located between the intermediate sections. The high density outer sections are in a stressed state from the pressure of the foam intermediate sections thereon. Also, a method for molding the panel.Rotational molding apparatus includes a chemical supplying portion, a chemical mixing portion, a mold portion, a mold supporting portion, a mixture delivery portion and a control portion. The chemical mixing portion includes a tubular member disposed in a substantially horizontal orientation with a plurality of spaced angled deflector sections.

Abstract: A foamed thermoplastic article having an integral outer unfoamed skin layer is formed from a mixture of thermoplastic resin containing a blowing agent by removing at least a portion of the blowing agent in the die of the extruder. The blowing agent is removed, e.g., by modifying the die so that it incorporates a porous section whcih allows the blowing agent to be removed from the mixture.

Abstract: In a method of extruding a plastic product having a foamed core layer and at least one unfoamed skin layer by forcing contiguous flows of a resin through a coextrusion die, one of the flows containing a blowing agent and a nucleating agent for forming the core layer and the second of the flows containing only the blowing agent, for forming the skin layer, the steps of establishing a fluent stream of resin containing the blowing agent, dividing the stream into separate streams which are separately conducted to the coextrusion die to constitute the core-forming and skin-forming flows, respectively, and selectively adding the nucleating agent only to that one of the separate streams which constitutes the core-forming flow. The nucleating agent used can be one which is effectively completely expended when the core layer foams, so that the foamed product is essentially free of active nucleating agent.

Abstract: The process for the extrusion of an expandable plastic composition comprising extruding the composition to an at least partially expanded state through a cross section of die with an area essentially the same as that of the entrance to the cooling fixture which defines the shape and dimensions in the final profile to be produced and essentially having the shape of the latter, by leaving a space empty of material within the profile in the course of extrusion through said cross section and then confining the composition thus extruded immediately at the exit from said die cross section and essentially along the extension of the extrusion axis, within a cooled and elongated shaping space, open at both ends along said extrusion axis and having an exit cross section identical to that of the profile to be obtained, the improvement comprising separating said cooled and elongated shaping space into at least two parts separated from one another by a free space, with the first said part not exceeding a few centimeters i

Abstract: A method of manufacturing a plastic molding of a foamable thermoplastic raw material blank or preform which contains a foaming agent by high frequency voltage heating in a molding die assembly defining a molding cavity, wherein gas discharging openings which extend through the thickness of the blank or preform are preformed in the raw material blank or preform.

Abstract: A microporous biocompatible material is formed by preparing a segmented polyether urethane urea solution containing 25%.+-.1.5% solids dissolved in a solvent. The solution has sufficient viscosity to be preshaped and formed into the desired thickness of the finished article, then immediately immersed into a precipitation bath in which the solvent in the solution is miscible for a time interval sufficient to cause the solution to set up into an opaque elastomeric article. The article is immediately removed from the bath, any excess solvent extracted and then dried at a temperature on the order of 35.degree. C. to 70.degree. C. followed by heat treating by annealing for approximately sixty minutes at a temperature at 100.degree. C. to 130.degree. C. The void volume of the membrane solution is controlled to within the 50% to 80% range and the pore size from ca <0.1 to several mms.

Abstract: A ball batting aid consisting of a spherical ball made of an expandable elastomeric material having a finite length of braided rope secured thereto, the ball being formed so that there is no air pocket within the confines thereof. An enlargement is placed on one end of the rope located in the central portion of the ball and when the ball is formed, the elastomeric material is expanded into the space between the braids of the rope to effect a securement of the material to the rope.

Abstract: Amine catalysts useful for producing polyurethane foams coated with skin by reaction of an organic polyisocyanate with a polyol. The catalysts comprise 4-methyl-1-(2-hydroxyalkyl)-piperazine, and emit no bad odor, give excellent moldability and are free from deterioration of skin and discoloration of covering materials.

Abstract: Expandible synthetic resinous particles are molded by injecting heated air generally centrally into the mold cavity by means of a probe, withdrawing the probe and heating the surface of the mold. Low densities and rapid cycle times are obtained.

Abstract: The dual extrusion and fusion of cellular and non-cellular resin extrudates produces an integral composite profile having a tongue and groove interlock. The resins are extruded through a common die having overlapping orifices. A bulbous tongue of one extrudate is encapsulated by finger-like projections of a second extrudate and the mated profiles are pulled through a vacuumized sizing box adapted to sealingly receive the cellular portion and to freely receive the non-cellular portion.

Abstract: Foamable thermoplastic compositions are described which are based on pre-compounded concentrated blends of an inorganic non-fibrous particulate foaming agent and a carrier polymer. The foamable thermoplastic polymer is selected from among aromatic polycarbonates alone or with acrylonitrile-butadiene-styrene copolymers polyesters, poly(ester-carbonates), and polyetherimides. The foaming agent may optionally be added as part of the concentrate.

Abstract: A homogeneous composite material comprising at least one external layer of thermosetting polymer, a layer of lightened thermoplastic polymer, and intermediate between the two layers, a homogeneous layer formed by polymerizing a monomer which is a diluent for the said lightened polymer; such that the monomer polymerizes to form an intimate blend at the interface of said polymers. The invention also comprises a process for producing the above said composite material.

Abstract: A method for making a ball having a cover and a core, which core has a spherical center and a winding, is disclosed. The ball is made by foam injection molding a thermoplastic resin comprising a mixture of at least about 45% of a copolymer of at least one olefin with at least one unsaturated monocarboxylic acid to form a spherical partially blown center. The center is then wound to form a wound core which is immersed in an adhesive which impregnates the yarn. The wound core is then dried and ironed the melt the surface of the center so as to fuse the windings to the center. A cover is then applied to the core to form the completed ball.

Abstract: A process of producing ICMUs (insulated concrete masonry units) having an inner load-bearing portion and one or two outer insulating portions are disclosed. Disregarding the insulation cores, heat flows from the outer side wall or walls to the inner portion through outer end walls and, in some embodiments, webs. These outer side walls and webs are heat bridges and are thinner and of significantly lower density than the other walls of the ICMU, thereby providing improved thermal insulation.Also disclosed are ICMUs with a vertical or horizontal recess in one outer insulating portion. Electrical conduit and/or plumbing can be placed into these recesses. In addition, corner ICMUs are disclosed which provide increased structural strength when used to construct a 90.degree. corner between two structural walls because of a special mid-wall in the corner ICMU.

Abstract: A method for providing anisotropic polymer membranes from a binary polymer/solvent solution using a thermal inversion process. A homogeneous binary solution is cast onto a support and cooled in such a way as to provide a differential in cooling rate across the thickness of the resulting membrane sheet. Isotropic or anisotropic structures of selected porosities can be produced, depending on the initial concentration of polymer in the selected solvent and on the extent of the differential in cooling rate. This differential results in a corresponding gradation in pore size. The method may be modified to provide a working skin by applying a rapid, high-temperature pulse to redissolve a predetermined thickness of the membrane at one of its faces and then freezing the entire structure.