Provided is a porous polytetrafluoroethylene membrane in which an absolute value of a difference in lightness between one principal surface and the other principal surface is 1.0 or more, where the lightness is lightness L* of CIE 1976 (L*, a*, b*) color space specified in JIS Z8781-4: 2013. The porous polytetrafluoroethylene membrane may be colored black or gray. The porous polytetrafluoroethylene membrane provided can have properties with a reduced coloring-induced deterioration.

A heat-resistant release sheet is configured to be disposed, when a resin or a target including a resin is used in a step involving heating and melting of the resin, between the resin or the target and a member to be brought into contact with the resin or the target to prevent direct contact between the resin or the target and the member. The sheet includes a skived sheet including polytetrafluoroethylene (PTFE) or a modified PTFE. A content of a tetrafluoroethylene (TFE) unit in the modified PTFE is 99 mass % or more. In each of two directions being in-plane directions of the heat-resistant release sheet and being perpendicular to each other, a rate of dimensional shrinkage induced by heating at 175° C. for 30 minutes is more than 0%. The sheet includes the skived sheet including the heat-resistant resin but prevents occurrence of problems attributable to inclusion of the skived sheet.

The invention relates to a process for the production of a non-fibrous drawn polymer tape, said process comprising the steps: a) compacting a polymer powder in a press to form a compacted polymer bed; b) calendering said compacted polymer bed to form an oriented polymer tape; and c) drawing said oriented polymer tape to form a highly oriented polymer tape; characterized in that step a) comprises compacting the polymer powder at a temperature and pressure such that from 0.1 to 20 wt. % of the polymer powder as measured by DSC is melted. The invention also relates to a tape obtainable by the above process, and a monolayer, multilayered material sheet and ballistic resistant article comprising such a tape.

A mechanically and piezoelectrically anisotropic polymer thin film may be formed by gel casting a solution that includes a crystallizable polymer and a liquid solvent. The solvent may be configured to interact with the polymer to facilitate chain alignment and, in some examples, create a higher crystalline content within the cast thin film. The thin film may also include up to approximately 90 wt. % of an additive and may be characterized by a bimodal molecular weight distribution of a crystallizable polymer where the molecular weight of the additive may be less than the molecular weight of the crystallizable polymer. In some examples, the polymer(s) and the additive(s) may be independently selected from vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, hexafluoropropene, vinyl fluoride, etc. The anisotropic polymer thin film may be characterized by an electromechanical coupling factor (k.sub.31) of at least 0.1.

Soft point bonded nonwoven webs, and methods of making the same, are described that utilize a pattern of small, discrete bond points in a sequent pattern that together form macro-elements. The macro-elements are themselves positioned and aligned within a pattern such that mechanical stretching operations on the point bonded nonwoven webs yields soft and bulky fabrics but with reduced incidence of tearing or rupturing of the individual bond points.

The present patent application relates to a method of manufacturing a multilayered composite film comprising a step of co-extruding at least three layers (a), (b) and (c), of which the layer (a) forms an outward surface of the composite film; the layer (c) forms a surface of the composite film facing or coming in contact with a good to be packaged; and the layer (b) is disposed between the layer (a) and the layer (c). Further, the method includes a step of biaxial orientation of the composite film thus co-extruded. Therein, the layer (a) contains or consists of a thermoplastic resin. The layer (b) contains or consists of a polyvinylidene chloride (PVdC) resin. The layer (c) contains or consists of a resin, preferably sealable, in particular heat-sealable resin. Therein, any crosslinking of the composite film by means of radioactive radiation, in particular by means of beta, gamma, X-ray and/or electron irradiation, is omitted during the manufacturing of the composite film and/or thereafter.

A heat shrinkable film shows a heat shrinkage rate in the direction perpendicular to the main shrinkage direction that is not high even at high temperature and is printable thereon. The heat shrinkable film includes a polyester resin, wherein the heat shrinkage characteristics in the direction perpendicular to the main shrinkage direction satisfy the following Relationships 1 and 2:
−15≤ΔT.sub.70-65≤0  Relationship 1
0≤ΔT.sub.100-95≤5  Relationship 2 wherein ΔT.sub.X-Y is a value obtained by subtracting heat shrinkage rate of the heat shrinkable film in the direction perpendicular to the main shrinkage direction after the heat shrinkable film is immersed in water bath for 10 seconds at Y° C. from heat shrinkage rate of the heat shrinkable film in the direction perpendicular to the main shrinkage direction after the heat shrinkable film is immersed in water bath for 10 seconds at X° C.

Provided are a white polyester film including a polyester and white particles, in which, at an equivalent of a thickness of 250 μm, a machine stretching direction tear strength F.sub.MD is 2.5 to 6.0 N, a transverse stretching direction tear strength F.sub.TD is 2.0 to 5.0 N, a ratio of the machine stretching direction tear strength F.sub.MD to the transverse stretching direction tear strength F.sub.TD is 1.05 to 4.00, and a concentration of terminal carboxyl groups is 5 to 25 equivalents/ton, a method for manufacturing the same, a solar cell back sheet and a solar cell module in which the same white polyester film is used.

The present invention relates to a process for the formation of a structured film, a structured film as such, an article comprising the structured film, a device for the continuous formation of such a structured film and a composite comprising the structured film.

Provided are a white polyester film including a polyester and white particles having an average primary particle diameter of 0.20 to 0.40 μm, in which a content of the white particles is 1.0% to 5.0% by mass with respect to the total mass of the film, a ratio of agglomerated particles having particle diameters of 0.40 to 0.80 μm in a direction parallel to a surface direction of the film on the cross-section of the film to the total number of primary particles and agglomerated particles of the white particles dispersed in the film is 10% to 20% by number, and a concentration of terminal carboxyl groups is 6 to 30 equivalents/ton, a method for manufacturing the same, a solar cell back sheet, and a solar cell module.