There is provided a polyolefin resin foam sheet formed by foaming a polyolefin resin, wherein the expansion ratio of the foam sheet is 1.5 to 20 cm.sup.3/g, the average cell sizes in the MD direction and the TD direction of the foam sheet are 130 μm or less, and the following formulas (1) and (2) are satisfied:
T.sub.M/D≥6  (1); and
T.sub.T/D≥5  (2), where T.sub.M denotes the tensile strength at 90° C. in the MD direction, T.sub.T denotes the tensile strength at 90° C. in the TD direction, and D denotes the density (g/cm.sup.3) of the foam sheet.

A method of fabricating a polymer composite material by mixing a polymer material with a planar material, depositing the mixture on a substrate, and stretching the resulting thin film, is described. Polymer composite materials produced using said method and ballistic resistant materials comprising said polymer composite materials are also described.

Example methods include depositing a precursor layer onto a substrate where the precursor layer includes droplets comprising a polymerizable material, inducing a phase inversion in the precursor layer to obtain a modified precursor layer including droplets of a non-polymerizable liquid within a polymerizable liquid mixture, and polymerizing the polymerizable liquid mixture to obtain a nanovoided polymer element. Examples include devices fabricated using nanovoided polymer elements fabricated using such methods, including electroactive devices such as actuators and sensors.

An optical element includes a nanovoided polymer layer having a first refractive index in an unactuated state and a second refractive index different than the first refractive index in an actuated state. Compression or expansion of the nanovoided polymer layer, for instance, can be used to reversibly control the size and shape of the nanovoids within the polymer layer and hence tune its refractive index over a range of values, e.g., during operation of the optical element. Various other apparatuses, systems, materials, and methods are also disclosed.

A polymer thin film is characterized by a first in-plane refractive index (n.sub.x) along a first direction of the polymer thin film, a second in-plane refractive index (n.sub.y) along a second direction of the polymer thin film orthogonal to the first direction, and a third refractive index (n.sub.z) along a thickness direction substantially orthogonal to both the first direction and the second direction, where n.sub.x>n.sub.z>n.sub.y. Such a polymer thin film may exhibit one or more of (a) an in-plane birefringence of at least approximately 0.05, and (b) n.sub.x greater than approximately 1.7.

A microporous membrane is made by a dry-stretch process and has substantially round shaped pores and a ratio of machine direction tensile strength to transverse direction tensile strength in the range of 0.5 to 5.0. The method of making the foregoing microporous membrane includes the steps of: extruding a polymer into a nonporous precursor, and biaxially stretching the nonporous precursor, the biaxial stretching including a machine direction stretching and a transverse direction stretching, the transverse direction stretching including a simultaneous controlled machine direction relax.

An absorbent article containing a polyolefin film is provided. The polyolefin film is formed by a thermoplastic composition containing a continuous phase that includes a polyolefin matrix polymer and nanoinclusion additive is provided. The nanoinclusion additive is dispersed within the continuous phase as discrete nano-scale phase domains. When drawn, the nano-scale phase domains are able to interact with the matrix in a unique manner to create a network of nanopores.

Porous air permeable expanded PTFE composite with enhanced mechanical and thermal properties are described. The node and fibril microstructure of expanded PTFE is coated on and within the node and fibril microstructure with a suitably chosen polymer to impart property enhancement while maintaining porosity. The coating polymer content of the composite is maintained between 3 and 25 weight percent of the composite and the areal mass of the composite is less than 75 gm/m.sup.2. Exemplary enhancement to properties may include, among others, Average Tensile Strength (ATS) (in MPa)×Z strength (in MPa) of 50 MPa.sup.2 or greater, preferably 100 MPa.sup.2 or greater, with air flow less than 500 Gurley seconds. Coating polymers with appropriate temperature resistance provides composites which further exhibit shrinkage of less than 10% at temperatures up to 300° C. with air flow of less than 500 Gurley seconds.

It is provided that a polyester film excellent in heat resistant dimension stability, impact-resistant strength properties, easy-slipping properties, mechanical properties, transparency, and gas barrier performance, and a film roll obtained by winding up this polyester film. A polyester film includes at least one layer mainly including a polyester resin containing a dicarboxylic acid component including furandicarboxylic acid as a main component and a glycol component including ethylene glycol as a main component; and the polyester film has a plane orientation coefficient ΔP of not less than 0.005 and not more than 0.200, a thickness of not less than 1 μm and not more than 300 μm, a heat shrinkage rate of 3.2% or less in each of the MD direction and the TD direction at 150° C. for 30 minutes, and a layer containing at least one additive.

Optical films comprising a polyester resin comprising a structural unit (A) of the following formula (1) wherein the content of the structural unit (A) based on the total structural units of the polyester resin is 76 mol % or greater: ##STR00001## wherein R.sub.1 is a hydrogen atom, CH.sub.3, or C.sub.2H.sub.5; R.sub.2 and R.sub.3 is each independently a hydrogen atom or CH.sub.3; and n is 1, for example, Decahydro-1,4:5,8-dimethanonaphthalene-2-methoxycarbonyl-6(7)-methanol. Retardation films and circularly or elliptically polarizing plates comprising the optical films are also provided.