Abstract: A process is disclosed for producing high grade synthetic paper containing at least 97 wt. % polyethylene on conventional continuous wet-lay paper-making equipment. In particular, the process comprises preparing a pulp furnish of 97-99.5 wt. % oriented polyethylene fibers and 0.5-3.0 wt. % polyvinyl alcohol fibers and depositing the fibers on the forming screen of a conventional wet-lay paper machine. The resulting waterleaf sheet is then dried on heated PTFE-coated drying cans, using a particular drying profile to reduce sticking and elongation, and then thermally bonded to provide a polyethylene paper having high strength, low defects and excellent uniformity. A process for producing the pulp fibers used in the paper-making process is also disclosed.

Abstract: Disclosed is an elongate, nonwoven flexible sheet structure and a method for its manufacture. The sheet structure consists essentially of a commingled mixture of about 45 to about 70% by weight short fibers of aromatic polyamide and about 30 to about 55% by weight fibrids of poly(meta-phenylene isophthalamide). The sheet structure has an interior thickness remote from the edges of between about 75 and about 150 microns with a thickened area along and adjacent each of the side edges having a maximum thickness which is at least about 5% greater in average thickness than the interior thickness of the sheet along and adjacent the thickened areas.

Abstract: An aramid paper which has high porosity while exhibiting the usual tensile properties is disclosed. The paper has good saturability and a smooth surface while retaining high break strength.

Abstract: A nonwoven fibrous web material that contains cellulose ester fibers, cellulose ester fibrets and a minor amount of activated fusible fibers uniformly dispersed throughout is particularly well suited as a filter media. The activated fusible fibers are effective for retaining within the filter web any particulate material resulting from corrugation without adversely affecting the filtration efficiency of the cellulose ester fibers and fibrets. Alternatively, the fibrous web material may include an effective amount of natural cellulosic fibers.

Abstract: A process for producing a fibrous gel composition of poly(paraphenylene terephthalamide) comprising the steps of placing terephthaloyl chloride in reactive contact with paraphenylene diamine in a solution of at least one amide-type polar solvent (e.g. N-methylpyrrolidone), an alkaline earth metal salt and the aliphatic tertiary amine, N-methylpyrrolidine or its hydrochloride. Poly(paraphenylene terephthalamide) papers are prepared by diluting the composition in an amide diluent, blending in a slurry of poly(paraphenylene terephthalamide) fibers in a precipitating medium, filtering, washing, pressing and drying the mixture.

Abstract: Temperature-sensitive bicomponent synthetic fibers that curl when heated are useful for making creped tissue webs with substantially increased bulk and absorbency with relatively low loss of strength.

Abstract: The present invention provides a method of producing a gas-permeable parcelling film for use in a container for isolating a product to be preserved from a freshness keeping agent placed within the container. The parcelling film has a gas-permeable formed member which is obtained by subjecting plastic fibers to a paper-making process and a drying process to obtain a dried sheet of plastic fibers, and then subjecting the dried sheet to a forming process into the formed member. The parcelling film is impregnated with fluororesin, before being subjected to the forming process.

Abstract: A filler composition that is suitable for use in the manufacture of paper, board, wet-laid non-wovens or other fibrous sheet materials comprises (preferably flocculated) filler particles (e.g. mineral fillers such as clay, talc or calcium carbonate) attached to fibres (e.g. synthetic organic fibres such as polyester or aramid fibres) by means of a coupling agent. These fibres generally have an average fibre length of 4 mm or more. Suitable coupling agents include oligomeric and other polymeric materials such as modified starch, cellulose ethers and derivatives thereof, modified natural gums, ketene dimers or poly(vinyl alcohol). Colloidal silica or colloidal bentonite clay may also be included. The filler composition is preferably added to the stock before the latter reaches the flowbox of the sheet-making machine. The invention allows high levels of filler to be achieved while maintaining satisfactory strength properties, in particular tear strength, in the sheet.

Abstract: A method for hydroentangling nonwoven fibrous sheet material to significantly increase the strength thereof at low latex add-on values employs small diameter jets of high-pressure water in the form of coherent streams that concentrate the hydraulic energy over a distance equal to approximately the diameter of the fibers being entangled. While fiber entangling water jets have been utilized heretofore, the present invention employs a relatively lower pressure for the fiber rearrangement along with a synergistic effect of wood pulp and long polyester fibers coupled with small amounts of latex to achieve the unexpectedly high strengths within these light weight materials. The resultant sheet material possesses excellent uniformity of fiber distribution and improved strength characteristics over those typically obtained from prior art water jet enganglement processes requiring 300-2000% the enganglement input energy employed in this process.

Abstract: A nonwoven, flexible sheet and process for making same consisting essentially of a comingled mixture of about 55 to about 75% by weight short fibers of poly(meta-phenylene isophthalamide) and about 25 to about 45% by weight fibrids of poly(meta-phenylene isophthalamide). The sheet has a basis weight of between about 10 and about 25 g/m.sup.2 and a thickness of between about 25 and about 45 microns and is impregnatable with resins or silicone oils.

Abstract: Processes are described for making highly absorbent tissues and towels by wet-laying pulps comprising particular polycarboxylate polymer-modified fibrous pulps such as mildly hydrolyzed methyl acrylate-grafted softwood kraft pulps; these pulps have distinct protonated and alkali-metal-cation-exchanged states. The wet-laying processes are adapted to exploit the very different behavior of the polymer-modified fibrous pulps in function of the two states. The preferred wet-laying processes described herein are continuous processes embodying one or more on-line chemical treatment steps which chemically switch state of the polymer-modified fibrous pulp component in a wet web on the papermaking machine to improve the processing thereof by averting or minimizing tendencies to mechanically or thermally degrade.

Abstract: The present invention relates to a process for producing fiber aggregate which comprises a dispersion step of dispersing fibers in the form of short fiber, whisker, or a mixture thereof into a dielectric fluid; an orientation step of placing the dielectric fluid containing said fibers dispersed therein in a space between a positive electrode and a negative electrode across which a high voltage is applied, whereby causing individual fibers in the dielectric fluid to electrostatically orient, with one end pointing to the positive electrode and the other end pointing to the negative electrode; and an aggregating step of aggregating the statically oriented fibers while keeping the oriented step, whereby producing fiber aggregate in which said fibers are mostly one-dimensionally oriented. Small amounts of surface active agent in the dielectric liquid promote fiber orientation in addition to dispersing the fibers.

Abstract: A nonwoven filtration fabric is composed of a plurality of fiber components of dissimilar denier and length which are evenly intermingled and bonded together in a sheet, including a first fiber component of staple polyester fibers of high denier and a textile length, a second fiber component of staple polyester fibers of low denier and shorter length than the first fiber component, a third fiber component of wood pulp fibers of shorter length than the first fiber components, and a suitable binder. The fabric is formed by a wet laid process in which the dissimilar fiber components are evenly mixed and distributed in a homogeneous slurry. A filter media made of the fabric has a high tensile strength, even pore size and distribution, low pressure drop, and is suitable for macrofiltration applications, such as filtering milk.

Abstract: A novel composite board of mineral wool, perlite, and cellulosic newsprint fibers for use primarily as a ceiling tile is disclosed. The board displays virtually no sag (less than 200 mils) when exposed to high temperature and high humidity while displaying quite acceptable strength. The board, or product without mineral wool or perlite, is manufactured by selective deposition of a latex composition on the cellulosic newsprint fibers.

Abstract: Disclosed herein is agricultural paper to be made into pots for raising seedlings. It is made up of a first layer made chiefly of natural pulp and a second layer made of synthetic fibers having a basis weight of 3-15 g/m.sup.2, said first layer and second layer being joined to each other by the wet papermaking process which intertwines the fibers of the two layers at their joining interface. The second layer is formed by fusion bonding composite synthetic fibers of polymers having different plasticizing temperatures.

Abstract: Elastic, heat-insulating shapes of ceramic, refractory or fireproof fibers and, where needed, further refractory or fireproof substances, and temporary or inorganic binders, as well as a process for the preparation thereof. The heat-insulating shapes are characterized by the fact that they contain 5 to 40 weight % of fibrids comprised of organic polymers, as a result of which they have elastic properties and can be formed with ease at moderate temperatures. In preparing these shapes, a customary aqueous dispersion containing the fibers and binder is mixed with the fibrids of the organic polymer, and water is removed therefrom and the shapes are otherwise produced in a known manner.

Abstract: A process for making a wet-laid, elongate, nonwoven flexible sheet having an additive distributed in a predetermined cross-directional pattern includes providing two synthetic fibrous stocks containing the additive in a concentration higher in one stock than in the other stock. The stocks are supplied to a paper machine having a headbox for depositing the stocks on a wire to form a wet sheet with the stocks being introduced into the headbox from a plurality of cross-directional positions equally spaced-apart along the headbox with a generally equal amount of solids being introduced at each position and with the stock with the higher concentration being introduced in higher quantity than the other stock at least at one cross-directional position so that the additive is distributed in the predetermined cross-directional pattern.

Abstract: The process for producing a tridimensional piece from an aqueous suspension containing at least a thermoplastic resin and reinforcing fibers, comprises the following steps:(a) the elements of the suspension are wet-molded into a preform in a mold, said preform having, in the three dimensions, the general outline of the final piece;(b) the preform is then at least partly de-watered;(c) then the preform is pre-heated to a temperature higher than the melting point of the thermoplastic resin;(d) the preform is then molded under pressure into its final shape in a press heated to a temperature below the melting point of the thermoplastic resin.

Abstract: A method for forming a fabric web by wet-laying fibers on paper-making equipment, the web comprising staple length natural or synthetic fibers and optionally wood cellulose papermaking fibers and an adsorbed polymeric surface active agent. The method comprises making up an aqueous fiber furnish with a polymeric surfactant having a plurality of both hydrophilic and hydrophobic groupings per molecule. The polymeric surfactant is adsorbed by the fibers and may be added to the fibers or it may be included in the aqueous carrier medium. In either case, the finished web contains and is improved by the inclusion of the polymeric surfactant.

Abstract: The present invention is a method of bonding a fibrous wet laid nonwoven fabric-like product using bacterial cellulose as a binder. The bacterial cellulose most useful for the invention is the type formed in an agitated culture. Microorganisms of the genus Acetobacter which are genetically adapted to be good cellulose producers under agitated conditions are preferred cellulose producers. From 1-30% of the bacterial cellulose may be added to a water slurry of other sheet forming fibers as a binder. Preferably 20% or less bacterial cellulose is used since higher amounts retard drainage rates significantly. Bacterial cellulose conveys many desirable properties such as excellent hydrophilicity with low air porosity and high tensile index. It may be used in many cases as a total replacement for the latex binders now used for manufacture of nonwoven fabrics. Bacterial cellulose is especially well adapted for the manufacture of pattern bonded sheets.

Abstract: A carbonaceous cylindrical body including a composite body of a carbonized material of a thin paper-like supporting body having a strength ratio of lengthwise direction to widthwise direction of 2 to 10 and obtained by manufacturing a paper-like body so that its carbonizable fibers are oriented and a carbonaceous matrix having an optically isotropic structure under a polarizing microscope and which shows a carbon content of at least 85% by weight, an oxygen gas permeation coefficient of 10.sup.-2 to 10.sup.-7 cm.sup.2 /sec. under a partial pressure of oxygen of 1 atmosphere and a bulk density of from 1.4 to 1.9 g/cm.sup.3. A process for producing the carbonaceous cylindrical body is also provided.

Abstract: Provided is a strong, flexible filter element comprising a wet laid non-woven element of glass fibers, synthetic short fibers, and polymer fibrids having a softening point below the softening point of the short fibers. In the filter element, the glass fibers are bound to the synthetic short fibers, e.g., aromatic polyamide short fibers such as poly(m-phenylene isophthalamide) short fibers, by the polymer fibrids, e.g., cellulose acetate fibrids, which act as a binder. The filter element exhibits excellent chemical resistance and a usefulness in removing particulates from gases at temperatures below 400.degree. F.

Abstract: The present invention provides a multilayer fibrous material suitable for use as an EMI and RFI shielding packaging material and a process for producing the same comprising first and second outer layers formed of paper or paperboard and an inner layer formed of paper or paperboard containing conductive carbon. The invention also provides a method of providing antistatic properties to the packaging material.

Abstract: A non-woven fibre product in which the fibre material consists, totally or in part, of fibres which are able to form bonds with natural or artificial fibres of the same or different type, and in which said fibres capable of forming bonds are cellulose carbamate fibres.

Abstract: Disclosed is a liquid-impermeable, gas-permeable nonwoven material comprising a thermally consolidated blend of (1) 5% to 30% of a first polyolefin pulp, (2) 15% to 90% of a second polyolefin pulp having a melting point at least 20.degree. C. higher than the first polyolefin pulp, and (3) 5% to 55% of a staple fiber. Also disclosed is a wet forming method for making such a nonwoven material without the use of surfactants.

Abstract: Articles are formed of materials which have at least one layer comprising a mixture of thermoplastic and other fibers. This latter layer may be thermobonded together and then densified along at least a section of the eventual peripheral edge margin of an article to be formed from the material. Thermoplastic material containing cover sheets may also be secured to the core and densified in this manner. The entire eventual peripheral edge margin of the article is typically densified. The material is cut within the densified region or slightly outside the densified region to provide a soft peripheral edge. Absorbent materials may be thermobonded within the layer and surrounded by a densified edge to fix them within the article. The composite materials are used in manufacturing infant car seat liners and other articles. In addition, sections of the material may be densified and provided with weakened areas, such as perforations, to enable users to selectively separate the articles along the perforations.

Abstract: A composition is described which is prepared so that it has a low electrical resistivity so that it can be used in electrostatic discharge operations. The composition includes carbon-coated fibers. The fiber is characterized in that it is a Lewis base while the carbon powder is a Lewis acid. The carbon-coated fiber is held together with a binder (such as a latex or resin). The binder may be either neutral or acidic. A resin can also be used to prepare rigid electrostatic discharge objects. When a resin is used, the resin should also be neutral and preferably, is acidic.

Abstract: Less porous, more abrasion-resistant nonwoven aramid sheets are made by expanding a smooth-surface, dried, wet-laid sheet of fibrids and fibers, which has fused, nonexpandable, densified regions, segmented by spaced interruptions of nonfused regions of the sheet structure, in a pattern which encloses expandable portions of the sheet structure. The re-wet sheet is heated dielectrically to expand the interior of the nondensified portions without substantially roughening or disrupting their surface skin.

Abstract: A process for making a high heat resistant oil-impregnatable insulating board, having a dielectric constant less than 2.7, made from bleached polytetrafluoroethylene floc and aromatic polyamide fibrids and the resulting insulating board are disclosed.

Abstract: Inorganic paper, which is made through paper-making process from a mixture consisting essentially of:(a) fibrous inorganic compound, as the principal component, having a fiber diameter of 100 microns or smaller and a fiber length which is ten times or more as long as the fiber diameter; and(b) fiber material in a microfibrillar form as a binding agent.

Abstract: Disclosed are flocced mineral materials which may be utilized to prepare high temperature resistant, water resistant articles. These materials are prepared by utilizing, as a starting material, a gellable layered swelled silicate that has an average charge per structural unit that ranges from about -0.4 to -1 and which contains interstitial cations which promote swelling with a source of at least one species of multi-amine derived cations.

Abstract: A process for producing a fiber reinforced polymer sheet by paper-making technology starting from an aqueous dispersion of thermoplastic polymer particles and fibers having a minimum length of 2.0 mm, characterized in that the polymer is an alternating copolymer of ethylene and carbon monoxide with an average weight molecular weight of at least 6000 and the fibers are used in an amount of from 5 to 450 pbw per 100 pbw of polymer.

Abstract: Method of forming a beater-saturated non-woven sheet by treating a slurry of papermaking fibers with alum and either sodium carbonate or a mixture of sodium bicarbonate and sodium hydroxide to achieve a pH in the range of about 7-9 followed by adding a binder latex which deposits on the fibers, and finally forming a sheet from the resulting slurry.

Abstract: A synthetic pulp comprising a pulp fiber of a thermoplastic resin and, adhering to the surface thereof, a polypropylene glycol having a molecular weight of 200 to 10,000, preferably together with a phenolic antioxidant and/or a phosphorous acid ester type antioxidant, has an excellent hydrophilic property even in the dry state and a good wettability or rewettability. This pulp forms a good slurry without bubbling when thrown in water. When a mixture of this synthetic pulp and other hydrophilic short fiber is subjected to a heat-fusion treatment, a fibrous molded articles having an excellent hydrophilic property, a good wettability or rewettability and a high wet strength is obtained, and this fibrous molded article is especially valuable as an absorbent.

Abstract: A method for forming a fibrous web by wet-laying fibers on paper-making equipment, the web comprising staple length natural or synthetic fibers and wood cellulose paper-making fibers wherein a water furnish of the fibers is made up with an associative thickener in the absence of a conventional surfactant. A preferred associative thickener for use with hydrophobic fibers is a urethane block copolymer having a polyethylene glycol backbone, the associative thickener acting as both surfactant and thickener. With predominately cellulosic fibers, i.e. conventional wood cellulose fibers, or a mixture of conventional and contorted wood fibers, and synthetic cellulosic fibers, such as rayon, a hydroxyethyl cellulose having a long alkyl side chain is preferred. Excellent consistency of the water and fiber dispersion is obtained at relatively low viscosity with rapid drainage of water from the wire and uniform formation of the web.

Abstract: The present invention resides in an envelope type separator for a storage battery and the manufacturing process thereof. The separator sheet is comprised of a first, microporous paper layer made of an inorganic powder material, a synthetic organic fiber material and an organic binder, and a second, coarse paper layer made of a synthetic organic fiber material and an organic binder, but no inorganic powder material, these layers being bound together by heating. The resultant separator sheet of combination paper type is then formed so that the mutually inward surfaces of the coarse paper layer are brought into contact with each other and are made to adhere to each other, preferably at the edges, by thermal fusion, so that the separator sheet is formed into the shape of an envelope process for making an envelope type separator sheet is also described.

Abstract: In an alkaline dry cell battery separator being a laid mat of non-dissolvable polyvinyl alcohol fibers held together by a matrix of dissolved or partially dissolved dissolvable polyvinyl alcohol fibers, the improvement comprising the mat having up to 85% of cellulosic fibers relatively uniformly distributed in and among the non-dissolvable polyvinyl alcohol fibers and held therein by said matrix.

Abstract: The present invention is a composite flooring felt for vinyl flooring containing a blend of latexes and an activator. Also included is a process for preparing the flooring felt composite. The process can additionally contain a wet strength resin and a flocculant.

Abstract: The filter paper according to the invention is characterised in that it contains electrically conductive fibers which render it electrically conductive and able to allow the heating of the fluid to be filtered by the Joule effect. According to a particularly advantageous application, this paper may be used in filters for fuel supply circuits in diesel engines, in order to prevent the blockage of such filters at low temperatures as a result of the freezing of paraffin contained in the fuel.

Abstract: A nonflammable paper having a sufficient yield at the time of paper-making and a sufficient non-combustibility and strength even in a basis weight as low as 100 g/m.sup.2 or less is provided, which paper is obtained by dispersing in water a composition comprising 40 to 95% by weight of calcium silicate in the form of needle, plate, thin film or a secondary aggregate thereof, and aluminum hydroxide powder, in a specified ratio by weight, 5 to 30% by weight of cellulose fibers and 0 to 30% by weight of other additives, the total weight of these components being 100% by weight, followed by subjecting the dispersion to paper-making.

Abstract: A relatively inexpensive mat is provided which through the application of heat and pressure readily can be densified to form rigid shaped articles having a reduced overall density. The mat is substantially free of a binder (e.g., a latex binder) and consists essentially of a substantially radom array of (a) relatively coarse cellulosic fibers, (b) thermoplastic synthetic polymer fibrils, (c) non-fibrous thermoplastic synthetic polymer particles, (d) substantially void-free substantially water-insoluble particulate inorganic material (e.g., talc), and (e) particulate void-containing substantially water-insoluble inorganic material (e.g., expanded volcanic glass) having a lesser density than component (d) in the specified quantities. A plurality of the mats while stacked together with similar mats of greater density on at least the upper and lower surfaces may be subjected to heat and pressure to accomplish densification and thermal bonding within and between adjoining mats to form a laminate.

Abstract: A relatively inexpensive mat is provided which through the application of heat and pressure readily can be densified to form rigid shaped articles. The mat is substantially free of a binder (e.g., a latex binder) and consists essentially of a substantially random array of (a) relatively coarse cellulosic fibers, (b) thermoplastic synthetic polymer fibrils, (c) non-fibrous thermoplastic synthetic polymer particles, and (d) substantially void-free substantially water-insoluble particulate inorganic material (e.g., talc) in the specified quantities. The mat preferably is formed by wet-laying from an aqueous dispersion wherein the (c) and (d) components are dispersed among and physically retained by the (a) and (b) components. A plurality of the mats while stacked may be subjected to heat and pressure to accomplish densification and thermal bonding within and between adjoining sheets to form a laminate.

Abstract: High temperature resistant pressboard having a desirable combination of compression set values and oil absorption is prepared by a process whereby a low density pressboard is first prepared by forming a wet lap of multiple layers of a waterleaf containing 50-95% by weight water and pressing the wet lap at 100-200.degree. C. under a pressure of 10-60 kg/cm.sup.2, drying, ultimately at 270.degree.-320.degree. C. until substantially no further moisture is evolved and finally pressing at 270.degree.-320.degree. C. under a pressure of 8-350 kg/cm.sup.2 and optionally cooling under restraint.

Abstract: An air permeable sheet-like structure comprising 20% to 60% by weight of reinforcing fibers having a high modulus of elasticity (as herein defined), and being between about 7 and about 50 millimeters long, and 40% to 80% by weight of wholly or substantially unconsolidated particulate plastics material, and in which the fibrous and plastics components are bonded into an air permeable structure.

Abstract: High density para-aramid papers comprising 5 to 25 percent, by weight, binder and an amount of para-aramid fibers selected from the group consisting of para-aramid pulp, para-aramid floc and mixtures thereof, compacted to provide a volume percent para-aramid fiber of at least 53 minus 0.13 times the volume percent floc in the paper are useful in the preparation of circuit board substrates having a low coefficient of thermal expansion.

Abstract: Disclosed is a semipermeable membrane support and a process for making the same. The support is formed of a non-woven fabric of a laminated structure having a low density layer with an air permeability of 5 to 50 cc/cm.sup.2 /sec and a high density layer with an air permeability of 0.1 cc/cm.sup.2 /sec to 5 cc/cm.sup.2 /sec, the non-woven fabric having an overall air permeability of 01 to 4.5 cc/cm.sup.2 /sec. The process for preparing such a support consists of laminating a dry processes web, which comprises entirely polyester fibers containing 20 to 80% of undrawn polyester fiber or conjugate polyester fibers having an average fiber denier of 1 to 3 denier formed through a dry process, and an un-press-treated wet processed web, which comprises entirely polyester fibers containing 30 to 90% of undrawn polyester fibers or conjugate polyester fibers having fiber denier of 0.1 to 1.

Abstract: A method of manufacturing controlled electrical resistivity carbon fiber sheet products employing a carbonizable starting material, heating and drawing the starting material (if required,) oxidizing the starting material at an elevated temperature of the order of 220 degrees Centigrade to effect molecular aromatic rearrangement of the starting material, carbonizing the oxidized starting material at an elevated temperature in an oxygen free atmosphere within a furnace having an elevated temperature extending over a temperature range to about 1400 degrees Centigrade by soaking the starting material at an elevated temperature for a predetermined period of time to provide a preselected electrical resistivity to the carbonized material. The carbonized material thus treated is formed into end carbon fiber sheet products having the form of paper, woven fabric and the like having a desired electrical resistivity. The starting carbonizable material consists essentially of PAN.

Abstract: A method of continuously manufacturing thin porous conductive strips, the strips including at least one layer based on a substance which contains carbon and a binder, the method comprising the successive steps of:preparing a very dilute aqueous dispersion of carbon or graphite fibers;adding an aqueous binder emulsion to the dispersion;initiating precipitation of a part of the binder onto the fibers;spreading the mixture in the form of a layer (1,2);removing at least some of the water from the mixture (3);drying the mixture (4,5,6,7); andsetting the layer to the required thickness (8) which may be less than a few tens of microns.

Abstract: A culvert having a corrosion resistant composite coating and a method of producing the corrosion resistant composite coating. The coating method is for use in a conventional hot dip coating line of the type wherein a steel strip, having been appropriately pretreated so as to be at or above the coating temperature and have its surface free of oxides, is caused to pass through a bath of molten coating metal. A fibrous aramid paper is bonded to the surface of the steel strip by pressing the fibers into the molten coating layer immediately after the steel strip exits the coating bath. The steel strip may be fabricted into construction products such as culvert which may be further protected with bituminous type coatings.

Abstract: High density para-aramid papers comprising 5 to 25 percent, by weight, binder and an amount of para-aramid fibers selected from the group consisting of para-aramid pulp, para-aramid floc and mixtures thereof, compacted to provide a volume percent para-aramid fiber of at least 53 minus 0.13 times the volume percent floc in the paper are useful in the preparation of circuit board substrates having a low coefficient of thermal expansion.