Reinforced Highly Microporous Polymers

A method of producing a microporous polymer comprising:

• forming an approximately saturated solution from a polymer by adding a high surface tension liquid, having a surface tension equal to or in excess of the polymer surface free energy, to the polymer previously dissolved in a low surface tension liquid, the low surface tension liquid being miscible in the high surface tension liquid to form a solvent, the high and low surface tension liquids being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid;
• the forming being conducted at a temperature less than or equal to a forming temperature, the forming temperature being the lower of a boiling temperature of the approximately saturated solution or a melt temperature of the polymer, wherein the approximately saturated solution comprises a solvent and a polymer material that is dissolved in the solvent,
• placing the polymer solution in a layer at the forming temperature;
• adding a fiber material to the polymer solution;
• urging the solvent into a non-wetting relation to the polymer by increasing the surface tension of the solvent to form a gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, causing the solvent to tend to bead within the gelled polymer;
• and
• evaporating, at a temperature not to exceed the forming temperature, the solvent from the gelled polymer to form a film defining a plurality of pores, such that sufficient solvent is removed from the gelled polymer to form the film defining the plurality of pores at a temperature near or below the forming temperature, the remaining solvent is removed at temperatures not to exceed the melt temperature of the polymer.

A method of forming a polymer film defining a plurality of micropores, the method comprising:

• forming a gelled polymer, wherein the polymer comprises at least about 80% polyvinylidene fluoride, at a forming temperature, by precipitating semicrystaline polymer from a saturated solution of polymer and a solvent wherein the solvent includes:
• a high surface tension liquid having a surface tension not less than the surface free energy of the polymer;
• and
• a low surface tension liquid that is miscible in the high surface tension liquid, the low surface tension liquid having a surface tension that is lower than the surface tension of the solvent, and being selected such that:
• the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid;
• and
• the low surface tension liquid has a higher vapor pressure than the higher surface tension liquid;
• placing the gelled polymer in a layer on a substrate;
• adding fiber material;
• urging the solvent into non-wetting relation to the polymer by increasing the surface tension of solvent in the gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, thereby causing the solvent to tend to bead within the gelled polymer.

A gelled polymer comprising:

• a gelled polymer matrix having a generally planar surface and a solvent surface tension, the gelled polymer including a semicrystalline polymer comprising a halogen, having a surface free energy;
• and
• a solvent in non-wetting relationship to the semicrystalline polymer having at least 70% of a total liquid content of a saturated solution of the polymer, the solvent comprising:
• a high surface tension liquid, having a surface tension equal to or in excess of the polymer surface free energy mixed with a low surface tension liquid being miscible in the high surface tension liquid, the high and low surface tension liquids being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid;
• and
• the polymer being maintained at a temperature less than or equal to a forming temperature, the forming temperature being the lower of a boiling temperature of the approximately saturated solution or a melt temperature of the polymer;
• fiber material;
• and
• a generally planar substrate having a substrate surface free energy at least equal to the solvent surface tension, the generally planar substrate supporting the gelled polymer matrix at the generally planar surface.

A method of producing a microporous polymer comprising:

• forming, at a temperature less than or equal to a forming temperature, the forming temperature being the lower of a boiling temperature of an approximately saturated solution or a melt temperature of the polymer, wherein the approximately saturated solution comprises a solvent and a polymer material that is dissolved in the solvent, an approximately saturated solution from a polymer by adding a high surface tension liquid, having a surface tension equal to or in excess of the polymer surface free energy, to the polymer previously dissolved in a low surface tension liquid, the low surface tension liquid being miscible in the high surface tension liquid to form a solvent, the high and low surface tension liquids being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid;
• adding a fiber material;
• urging the solvent into non-wetting relationship with the polymer includes evaporating the low surface tension liquid;
• urging the solvent into a non-wetting relation to the polymer by increasing the surface tension of the solvent to form a gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, causing the solvent to tend to bead within the gelled polymer;
• and
• evaporating, at a temperature not to exceed the forming temperature, the solvent from the gelled polymer to form a film defining a plurality of pores.

A method of forming a polymer film defining a plurality of micropores, the method comprising:

• forming a gelled polymer, wherein the polymer comprises at least about 80% polyvinylidene fluoride, at a forming temperature, by precipitating semicrystaline polymer from a saturated solution of polymer and a solvent;
• placing the gelled polymer in a layer on a substrate;
• adding a fiber material;
• urging the solvent into non-wetting relation to the polymer by increasing the surface tension of solvent in the gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, causing the solvent to tend to bead within the gelled polymer precipitating the polymer by mechanical removal of the solvent from the gelled polymer.

A method of producing a microporous polymer comprising:

• forming an approximately saturated solution from a polymer by adding a high surface tension liquid, having a surface tension equal to or in excess of the polymer surface free energy, to the polymer previously dissolved in a low surface tension liquid, the low surface tension liquid being miscible in the high surface tension liquid to form a solvent, the high and low surface tension liquids being selected such that the polymer material has a higher solubility in the low surface tension liquid than in the high surface tension liquid;
• the forming being conducted at a temperature less than or equal to a forming temperature, the forming temperature being the lower of a boiling temperature of the approximately saturated solution or a melt temperature of the polymer, wherein the approximately saturated solution comprises a solvent and a polymer material that is dissolved in the solvent, the low surface tension liquid being selected to have a higher vapor pressure than the high surface tension liquid, thereby allowing the low surface tension liquid to evaporate at a faster rate than the high surface tension liquid from the gelled polymer;
• adding a fiber material;
• placing the polymer solution in a layer at the forming temperature;
• urging the solvent into a non-wetting relation to the polymer by increasing the surface tension of the solvent to form a gelled polymer such that the surface tension exceeds the surface free energy of the polymer material, causing the solvent to tend to bead within the gelled polymer, the urging including evaporating the low surface tension liquid;
• and
• evaporating, at a temperature not to exceed the forming temperature, the solvent from the gelled polymer to form a film defining a plurality of pores.