Abstract: An object of the present invention is to provide a polyolefin microporous film that can sufficiently reduce the occurrence of raised edges at a slitting step such as a slitting step at the time of producing the polyolefin microporous film and a slitting step at the time of processing the polyolefin microporous film into a roll. The present invention provides a polyolefin microporous film formed from a polyolefin composition comprising a polyethylene, a first polypropylene having a viscosity average molecular weight of not less than 50,000 and less than 300,000, and a second polypropylene having a viscosity average molecular weight of not less than 300,000.

Abstract: An extruded polypropylene type resin foam having a high expansion ratio of at least 15 times and a closed cell ratio of at least 70% and excellent in the heat insulation property, and its production process, are provided. An extruded polypropylene type resin foam, which is produced by extrusion-foaming a polypropylene type resin composition containing a linear polypropylene type resin having a melt tension at 230° C. of from 5 to 30 g, by using a blowing agent containing at least a hydrocarbon type gas, and which has an expansion ratio of at least 15 times and a closed cell ratio of at least 70%.

Abstract: The present disclosure provides propylene-based polymers which exhibit a strain hardening distribution factor that is less than zero and/or a strain hardening factor greater than 1.5. The propylene-based polymers are rheology-modified by way of silane coupling to improve melt strength.

Abstract: The invention relates to an agent for sanitary facilities, said agent being applied directly on the sanitary object and adhering there, and being flushable only after a large number of flushes, wherein the agent comprises fillers and a bonding agent, wherein the bonding agent is selected from the group of polyalkylene derivatives, hydrogenated polystyrol derivatives, silicone systems, copolymers from the group of monoalkyl esters of poly(methyl vinyl ether/carbonic acid anhydrides, olefin homopolymers, and copolymers of two or more olefins, wherein the olefin homopolymers and copolymers can also be partially hydrogenated, partially oxidized, or further functionalized by means of graft molecules, and from the group of polyalkyleninmines, including in alkoxylized form, the polyetheramines (alkoxylized amines) and the polyglycerin polyether alkyl carbonic acids or polymers or derivatives comprising said polymer groups, and the viscosity of the agent is at least 30 Pa s, measured using a Haake viscosometer, plate

Abstract: To provide a foam board of a polyolefin resin which has an excellent heat insulating property and sound absorption property, of which a product can be material-recycled and which can continuously be produced at a low cost. A method for producing a foam board, which comprises extrusion-foaming by ejecting a mixture of a polyolefin resin composition containing a linear polypropylene resin having a melt tension of from 5 to 30 g at 230° C. and a foaming agent containing at least carbon dioxide in the supercritical state, by means of an extruder which has a multi-hole type die having an opening diameter of from 0.1 to 1.0 mm and the number of openings of from 50 to 5,000 at an ejection amount (V) of from 0.05 to 0.45 kg/hr per one opening in the die at a melt-extrusion temperature of from 160 to 250° C., under atmosphere at a proximal resin pressure of from 7 to 20 MPa at the openings of the die.

Abstract: Process for preparation of ethylene homopolymers or copolymers, comprising the steps of a) polymerization of ethylene or of ethylene with one or more other 1-olefins in the presence of a chromium catalyst at temperatures of from 20 to 200° C. and at pressures of from 0.1 to 20 MPa, where the chromium catalyst can be prepared via application of one or more chromium compounds to a silicate support and subsequent thermal activation under oxidative conditions at temperatures of from 620 to 900° C.; b) mixing of the polyethylene in the melt in the presence of from 1000 to 2000 ppm of an antioxidant comprising at least one sterically hindered phenol and comprising at least one phosphite in a mixing ratio of from 1:5 to 5:1, with specific energy input of at least 0.17 kWh/kg.

Abstract: A porous film for a heat-sealable bag-constituting member is prepared by stretching an unstretched film to be porous. The unstretched film includes an ultrahigh-molecular-weight polyethylene having a weight-average molecular weight of 30×104 to 250×104, a polyolefin component other than the ultrahigh-molecular-weight polyethylene, and an inorganic filler as essential components, and the content of the ultrahigh-molecular-weight polyethylene is 1 percent by weight or more based on the total amount of polymer components constituting the porous film. Even when produced by stretching at a low draw ratio, the film does not suffer from uneven stretching and shows high productivity. When the film is heat-sealed into a bag, the bag has a high seal strength and does not suffer from edge tear. The film is therefore useful particularly as a bag-constituting member to be heat-sealed into a bag typically as a disposable body warmer.

Abstract: A foam comprising a nanocomposite comprising a bulk linear semi-crystalline polyolefin containing no cross-links or branched polymers; an organoclay; and a polymeric compatibilizer for enhancing physical interactions between the bulk linear semi-crystalline polyolefin and the organoclay, wherein the linear semi-crystalline polyolefin combines with the organoclay to form the nanocomposite is provided. Novel nanocomposites and methods of producing the nanocomposites and foams, such as flexible foams, are also provided. The resulting products are useful in a variety of applications, including thermoplastic flexible foam seals, thermoplastic foamed panels in vehicles, and thin-walled blow molded bottles.

Abstract: A process for preparing functionalised microporous polymers (which are also known as micro-cellular polymers or polyHIPE polymers (PHPs)) using intensified internal heating (for example by microwave irradiation).

Abstract: A coalescing agent for facilitating the separation of a non-aqueous phase from an aqueous phase of an aqueous medium, said agent consisting of particles of a polymeric foam material having: an IFD no. of 40 or higher (i.e. at least 40); a BR no. of 35 or higher (at least 35); a SF no. of 1.8 or higher (i.e. at least 1.8) and a density of 42 kg/m3 or less.

Abstract: A thermoplastic resin for foam molding wherein the number of fish eyes (FE) having a maximum length of 0.5 mm or more is 50/m2 or more when made into a film having a thickness of 30 ?m, and a thermoplastic resin composition for foam molding containing the above-described resin and a foaming agent.

Abstract: The present technology relates to a foam comprising a polypropylene material. The polypropylene material is produced in the presence of a metallocene catalyst, and the foam and/or the polypropylene has a branching index g? of less than 1.00 and a strain hardening index (SHI@1 s?1) of at least 0.30 measured by a deformation rate d?/dt of 1.00 s?1 at a temperature of 180° C., where the strain hardening index (SHI) is defined as the slope of the logarithm to the basis 10 of the tensile stress growth function (log(?E+)) as a function of the logarithm to the basis 10 of the Hencky strain (log(?)) in the range of Hencky strains between 1 and 3.

Abstract: A process for the preparation of bitumen foam, wherein a gas is dispersed into the bitumen with a temperature of less than 200° C. and with a viscosity van 100-10.000 mPas measured at the temperature using EN 12596, wherein the process includes bringing the gas tangentially into contact with a bitumen stream, to obtain a bitumen foam that is not dehydrogenated, oxidised or otherwise chemically modified, and in which at least 10 vol % gas is distributed substantially homogeneously. This process can be applied simply and safely, and results in bitumen foam without additions being necessary for this. In this way bitumen can be processed at lower temperatures, even below 100° C., to asphalt or wearing course.

Abstract: Rheology modification of an ethylene/?-olefin interpolymer is achieved by blending the interpolymer with at least one branched polyolefin. The polyolefins can be homopolymers or interpolymers and have a branching index of less than 1. The ethylene/?-olefin interpolymer is a block copolymer having at least a hard block and at least a soft block. The soft block comprises a higher amount of comonomers than the hard block. The block interpolymer has a number of unique characteristics disclosed here. Rheology-modified ethylene/?-olefin interpolymer, i.e., the resulting polymer blends, can be extruded or molded into many useful articles, such as films, sheets, profiles, gaskets, foams, etc.

Abstract: The present invention describes a process and respective installation for continuous production of foamed polymeric sheets by extrusion, another object of the invention being the development and use of polypropylene-based formulations comprising linear polypropylenes and branched polypropylenes. The installation includes four stages: a first stage of extrusion foaming, in which a foaming agent, either of a chemical or physical nature, in the latter case introduced in supercritical conditions, is mixed with the polymeric mass melted previously in the first stages of the extruder, the material expanding exactly at the outlet of the lips of the planar extrusion head; a second stage of calibration and cooling of the foamed sheet, in which the expanded plastic material is cooled by contact in a system of vacuum calibrators and by contact with water in a cooling bath; a stage of collection of the foamed panel; and a final stage of cutting of the foamed sheet, defining the final dimensions thereof.

Abstract: Disclosed are new compositions consisting of polyphosphonates and specific additive compositions that exhibit superior resistance to degradation due to exposure to air, high temperature and air, moisture or combinations thereof. Also disclosed are polymer mixtures or blends comprising these polyphosphonates/additive compositions and commodity and engineering plastics and articles produced therefrom. Further disclosed are articles of manufacture produced from these materials, such as fibers, films, coated substrates, moldings, foams, fiber-reinforced articles, or any combination thereof.

Abstract: Foam a polymer blend of (a) a high melt strength polypropylene (HMS PP); (b) a linear or substantially linear polypropylene that has a melting point within ten degrees Celsius of (a), a melt flow rate that is significantly different than (a) and that is miscible with (a); and, optionally, (c) a polyethylene that is immiscible with (a) produces a polymeric foam having an average cell size of at least four millimeters and that has an inherent open-celled content of at least 40 percent. The HMS PP makes up 60 weight percent (wt %) or more and 90 wt % or less of the total combined weight of (a) and (b). Component (c) makes up 60 wt % or less of the total polymer blend weight.

Abstract: To provide porous monodispersed particles obtained by preparing, as seed particles, poly(methyl methacrylate) particles or acrylic resin particles comprising 70% by mass or more of methyl methacrylate as a copolymerization component, swelling the seed particles 20 to 80 times the size of the original seed particles by mass using a swelling solution comprising an oil-soluble polymerization initiator and a monomer mixture containing 70% by mass or more of methyl methacrylate and 3 to 8% by mass of divinylbenzene, and polymerizing the monomers. The particles are porous particles with a diameter of the order of micrometers and a narrow particle-size distribution and are monodispersed. Colored monodispersed particles obtained by agglomerating a pigment in the porous monodispersed particles are monodispersed and spherical, and contain a large amount of pigment therein.

Abstract: Improved polypropylene resin foamed beads that without detriment to the excellence in properties, such as compression properties and heat resistance, characterizing the polypropylene resin foamed beads, can provide a polypropylene resin foamed bead molded article with equal properties by an molding conducted at low heating temperature. There are disclosed polypropylene resin foamed beads composed of a polypropylene resin of 115 to 135° C. melting point and 500 MPa or higher Olsen flexural modulus. The amount of ash at the surface of the foamed beads is 3000 wt. ppm or less (including 0). With respect to the foamed beads, in the first DSC curve obtained by heating 1 to 3 mg of polypropylene resin foamed beads from room temperature to 200° C. at a temperature elevation rate of 10° C.

Abstract: The present invention relates to a light-reflecting member including a polyolefin resin foam as a light-reflecting layer, the polyolefin resin foam being obtained by foam molding a resin composition containing a polyolefin resin. According to the light-reflecting member of the invention, since it has the above-mentioned constitution, the light-reflecting member is excellent in light reflection, impact-absorbing property, and lightness in weight. Moreover, the process for producing a light-reflecting member of the invention can provide a light-reflecting member excellent in light reflection, impact-absorbing property, and lightness in weight by using a polyolefin resin foam.

Abstract: The present subject matter relates generally to polymer compositions, and more particularly to irradiated polymer compositions comprising at least one non-phenolic stabilizer. The present polymer compositions comprise an unexpected balance of properties after being subjected to irradiation treatments, including an unexpected combination of a lower melt flow rate ratio (MFRr) and high melt tension after being irradiated, while minimizing negative yellowing effects.

Abstract: A co-sintered porous polymer includes at least one molecule specific powder for adsorbing at least one target molecule from a complex liquid mixture when the liquid is passed through the porous co-sintered polymer. The co-sintered polymer can include a sintered porous polyethylene substrate. The or each molecule specific powder can be an immobilising adsorbent powder, for example a molecularly imprinted polymer or a rationally designed polymer.

Abstract: The present invention refers to an apparatus and a method for the manufacture of a three-dimensional scaffold at low temperatures and the respective use of this method and apparatus.

Abstract: The present invention relates to cross-linked polyolefin aerogels in simple and fiber-reinforced composite form. Of particular interest are polybutadiene aerogels. Especially aerogels derived from polybutadienes functionalized with anhydrides, amines, hydroxyls, thiols, epoxies, isocyanates or combinations thereof.

Abstract: A pre-expanded beads of olefin-modified polystyrene-based resin comprising a pie-expanded beads of a polystyrene-based resin modified with a polyolefin-based resin, wherein a styrene-based monomer forming a polystyrene-based resin in the beads is used in the range of 100 to 1,000 parts by weight relative to 100 parts by weight of a polyolefin-based resin, a bulk density of each bead is 0.012 to 0.20 g/cm3, and an absorbance ratio at 698 cm?1 and 2850 cm?1 (D698/D2850) obtained from an infrared absorption spectrum of each bead surface measured by ATR method infrared spectroscopy is in the range of 0.1 to 2.5.

Abstract: The invention provides a preparation method of super-macroporous polymeric microspheres and a product thereof. The method is characterized in that adding high content of surfactant into an oil phase containing a monomer and dispersing the oil phase containing the monomer and the surfactant into an aqueous phase. Super-macroporous microspheres are obtained by means of suspension polymerization. In the interior of the microspheres, 10-60% of the pores are distributed in a range of 500-900 nm. The microspheres have a particle diameter of 1-200 ?m and a porosity of 30%-90%. The product is suitable for being used as a stationary phase matrix in liquid chromatography, a carrier for high performance catalysts and a high performance adsorbent, and especially, being used as a separation medium for separating biomacromolecules.

Abstract: Disclosed herein are methods for making expanded foamed polymeric panels from solid monolithic semi-crystalline thermoplastic material sheets having a first thickness, density, and volume. In one embodiment, the method comprises: absorbing an effective amount of a plasticizing gas into the semi-crystalline thermoplastic material sheet to yield a reversibly plasticized semi-crystalline thermoplastic material sheet that is differentially impregnated with the plasticizing gas to define a non-uniform gas concentration gradient across the initial first thickness; and heating the plasticized semi-crystalline thermoplastic sheet to yield the foamed polymeric panel, wherein the foamed polymeric panel comprises (1) a second thickness that is at least about three and half times greater than the first initial thickness, and (2) a non-uniform second density level that is less than the first density level.

Abstract: A process of forming an integral hydrophilic membrane from a porous hydrophobic membrane includes exposing a porous hydrophobic polymer membrane to a plasma, wherein the plasma contains reactive carbon dioxide species configured to covalently bond carboxylic functional groups to a surface of the polymer membrane and form the integral hydrophilic membrane.

Abstract: In an exemplary embodiment, the present method includes the stops of providing a polymer resin to be processed: blending particulate boron nitride (BN) and a fluorine-containing polymer with said polymer resin to provide a resin blend: heating said resin blend to obtain a desired flowability value: and processing said resin blend into a desired shape.

Abstract: A molecularly imprinted polymer and production process therefor and a process for selective treatment of poorly degradable and/or toxic compounds in liquids using the molecularly imprinted polymers. Such polymers and processes are required for selective removal and/or degradation of biological, poorly degradable pollutants or toxic compounds, for example from wastewaters. Consequently, a molecularly imprinted polymer suitable for the selective treatment of at least one poorly degradable and/or toxic compound is provided having a polymeric network which is made up of monomers and has cavities of predetermined size, wherein the cavities are arranged at predetermined spacings and have specific binding sites and/or patterns for the poorly degradable and/or toxic compounds.

Abstract: A process for the preparation of thermoplastic auxetic foams comprising the steps of: a) taking conventional thermoplastic foam; b) subjecting said foam to at least one process cycle wherein the foam is biaxially compressed and heated; c) optionally subjecting the foam to at least one process cycle wherein the biaxial compression is removed and the foam mechanically agitated prior to reapplying biaxial compression and heating; d) cooling said foam to a temperature below the softening temperature of said foam; and e) removing said compression and heat.

Abstract: The disclosure is directed to a framed device. The framed device includes a substrate, a frame, and a seal. The substrate has a first length, a first width, and a peripheral edge. The frame has a second length, a second width, and a groove that runs along the second length and the second width of the frame. The groove is substantially engaged with the peripheral edge of the substrate. The seal is disposed within the groove of the frame, wherein the seal runs contiguously from the substrate to the frame and the seal includes a foamed polymer.

Abstract: The invention relates to a polyolefin composition. The polyolefin composition can be in the form of a multi-layer, microporous polyolefin membrane comprising a first microporous layer containing 7% or less by mass of ultra-high-molecular-weight polyethylene having a weight-average molecular weight of 1×106 or more, and having a structure in which a pore size distribution curve obtained by mercury intrusion porosimetry has at least two peaks, and a second microporous layer containing 8% or more by mass of the ultra-high-molecular-weight polyethylene.

Abstract: An organic damping material which by itself has excellent damping properties without being combined with other material(s), need not have a certain thickness or volume for ensuring sufficient damping performance, and is easy to process. It is characterized by comprising a polymer matrix phase and a phase dispersed therein comprising one or two or more compounds selected among-(p-toluenesulfonylamido)diphenylamine, 4,4?-bis(?,?-dimethylbenzyl)diphenylamine, octylated diphenylamine, 2,2?-methylenebis(4-ethyl-6-tert-butylphenol, 4,4?-thiobis(3-methyl-6-tert-butylphenol.

Abstract: Foamable polymer preparation comprising (a) 19.9 to 89.9% by weight of a polymer, (b) 10 to 80% by weight of a desiccant, (c) 0.1 to 5.0% by weight of a foaming agent comprising a hydrogen carbonate metal salt and a component selected from the group consisting of a polycarboxylic acid containing 2 to 10 carbon atoms and at least 2 carboxyl groups, a metal salt thereof and an ester of said polycarboxylic acid in which at least one of the carboxyl groups have been esterified with an alcohol containing 1 to 6 carbon atoms; wherein the weight percentages relate to the weight of the foamable polymer preparation.

Abstract: A process of producing a foamed molding, wherein expanded, substantially non-crosslinked polypropylene-based resin beads are heated in a mold to fuse-bond the beads together into a unitary body. Each of the expanded beads has been surface-modified with an organic peroxide.

Abstract: The present technology relates to a foam comprising a polypropylene material. The polypropylene material is produced in the presence of a metallocene catalyst, and the foam and/or the polypropylene has a branching index g? of less than 1.00 and a strain hardening index (SHI@1 s?1) of at least 0.30 measured by a deformation rate d?/dt of 1.00 s?1 at a temperature of 180° C., where the strain hardening index (SHI) is defined as the slope of the logarithm to the basis 10 of the tensile stress growth function (log(?E+)) as a function of the logarithm to the basis 10 of the Hencky strain (log(?)) in the range of Hencky strains between 1 and 3.

Abstract: Foamable compositions and soft foams comprise at least an ethylene/?-olefin interpolymer. The soft foam has a density from about 10 to 150 kg/m3. The foamable compositions further comprise a blowing agent. The ethylene/?-olefin interpolymers are a multi-block copolymer comprising at least one soft block and at least one hard block. Methods of making the foamable compositions and soft foams; and foam articles made from the soft foams are also described.

Abstract: Expanded polypropylene resin beads having a melting point of not less than 120° C. but less than 140° C., the melting point being determined from a DSC curve obtained by heat flux differential scanning calorimetry in accordance with JIS K7121-1987 in which a sample of 1 to 3 mg of the expanded polypropylene resin beads is heated to 200° C. at a heating rate of 10° C./minute, then cooled to 30° C. at a rate of 10° C./minute, and again heated from 30° C. to 200° C. at a heating rate of 10° C./minute to obtain the DSC curve. The expanded polypropylene resin beads has an apparent density ?1 before heating and an apparent density ?2 after being heated for 10 seconds with steam at a temperature higher by 5° C. than the melting point thereof, wherein a ratio of ?1 to ?2 is not greater than 1.5.

Abstract: [Objects] It is an object to provide a foam having a low specific gravity and a small compression set, more preferably a foam having a low specific gravity, a small compression set and uniform quality, a foaming composition, and applications of the foam. [Means for Solution] The foam is obtained by foaming an olefin polymer, wherein the foam has a specific gravity (d) in the range of 0.03 to 0.30, and a compression set (CS, %) and the specific gravity (d) satisfy the formula of CS??279×(d)+95. The foam is preferably obtained from a foaming composition that includes an ethylene polymer (A) including a specific ethylene/?-olefin copolymer (A1) and an ethylene/polar monomer copolymer (A2) in a specific mass ratio, and a specific ethylene/C3-20 ?-olefin/non-conjugated polyene copolymer (B).

Abstract: A structural foam material comprising that contains a volatile corrosion inhibitor homogenized in the pre-thermoformed resin. The foam can be of a reticulated or open-cell type. The foam can also be of a closed-cell type that has a sufficient number of cells opened so as to permit migration of the volatilzed corrosion inhibitor.

Abstract: Disclosed is a die plate for a die block having a coat-hanger-shaped flow path for extruding a molten foamable thermoplastic resin in a form of a sheet. The die plate is for arrangement on a downstream side of the coat-hanger-shaped flow path to make a flow rate of the molten foamable thermoplastic resin uniform in a width direction. The die plate is provided with a multiplicity of delivery apertures. In the delivery apertures, the delivery apertures in opposite side regions have a diameter greater than a diameter which the delivery apertures in a center region have. A die unit composed of a die block, which has a multiple bifurcated manifold terminating in plural coat-hanger-shaped flow paths at downward ends thereof, and a like plural number of similar die plates as described above; a process for producing a wide thermoplastic resin foam by using the die unit; and the wide thermoplastic resin foam are also disclosed.

Abstract: The invention relates to a microporous membrane which comprises polyethylene, the microporous membrane having a differential pore volume curve with an area under the curve over the range of pore diameters of from about 100 nm to about 1,000 nm that is 25% or more of a total area under the curve over the range of pore diameters of from about 10 nm to about 1,000 nm.

Abstract: A microporous polyolefin membrane having a structure in which its pore size distribution curve obtained by mercury intrusion porosimetry has at least two peaks, which is produced by extruding a melt-blend of a polyolefin composition comprising (a) high density polyethylene resin having a weight average molecular weight of from about 2.5×105 to about 5×105 and a molecular weight distribution of from about 5 to about 100, (b) polypropylene resin having a weight average molecular weight of from about 3×105 to about 1.

Abstract: A process and article for use as a substitute for natural cork. The article has a cork substitute material comprising an expanded polyolefin foam having a density of about between 6.6 lb/ft3 and 12.5 lb/ft3 and a compressive strength of about between 126 Psi and 406 Psi (0.86 MPa and 2.8 MPa) at 25% Strain.

Abstract: The present invention concerns method of preparing shape memory materials starting from standard thermoplastic polymers. The present invention further is concerned with products obtained by the methods in accordance with the present invention and the use of these products over a wide variety of applications.

Abstract: An earplug comprising a foam composition containing a polyvinyl chloride resin and less than about 5 wt % monomeric phthalate, based on the total weight of the foam composition, is described. The foam composition may include a plasticizer containing less than or equal to about 2 wt % monomeric phthalate, based on the total weight of the plasticizer. The earplugs have slow recovery times from 60 percent compression to 10 percent compression of about 10 to about 60 seconds.

Abstract: Extruded propylene-based resin foam according to the present invention is formed by extrusion-foaming a propylene-based resin, and the extruded propylene-based resin foam has a closed cell content of less than 40% and an expansion ratio of 10 or more. Since the extruded propylene-based resin foam has an open-cell structure in which a cell-broken state is formed at a desired level and has a high expansion ratio, each cell in the foam has a sound absorption performance, such that the extruded foam is excellent in sound absorption performance.

Abstract: Copolymers, especially multi-block copolymer containing therein two or more segments or blocks differing in chemical or physical properties, are prepared by polymerizing propylene, 4-methyl-1-pentene, or other C4-8?-olefin and one or more copolymerizable comonomers, especially ethylene in the presence of a composition comprising the admixture or reaction product resulting from combining: (A) a first metal complex olefin polymerization catalyst, (B) a second metal complex olefin polymerization catalyst capable of preparing polymers differing in chemical or physical properties from the polymer prepared by catalyst (A) under equivalent polymerization conditions, and (C) a chain shuttling agent.

Abstract: A method for producing a microporous material comprising the steps of: providing an ultrahigh molecular weight polyethylene (UHMWPE); providing a filler; providing a processing plasticizer; adding the filler to the UHMWPE in a mixture being in the range of from about 1:9 to about 15:1 filler to UHMWPE by weight; adding the processing plasticizer to the mixture; extruding the mixture to form a sheet from the mixture; calendering the sheet; extracting the processing plasticizer from the sheet to produce a matrix comprising UHMWPE and the filler distributed throughout the matrix; stretching the microporous material in at least one direction to a stretch ratio of at least about 1.5 to produce a stretched microporous matrix; and subsequently calendering the stretched microporous matrix to produce a microporous material which exhibits improved physical and dimensional stability properties over the stretched microporous matrix.