A foam includes a cellular structure and having a density of at most 0.50 g/cm.sup.3, where the cellular structure is provided by a solid material that includes humins. Such a foam is prepared in a process, which includes: providing a starting material containing humins; and heating the starting material to a temperature in the range of 150 to 450 C. The foam can be used in articles for a variety of applications such as substrate for plant growth, as adsorbent for treating waste water or waste gases, as support for solid catalysts, as insulation material, or packaging material.

There is provided a porous polyimide film in which the pore distribution width A represented by the following formula is 1.15 or less, the average pore diameter is within a range of 0.50 m to 3.0 m, and the air permeation speed is 30 seconds or less:

A=(D.sub.84/D.sub.16).sup.1/2 wherein D.sub.16 is the pore diameter at 16% cumulation from the small diameter side of pores, and D.sub.84 is the pore diameter at 84% cumulation from the small diameter side of pores.

Polymer foams based on polyetherimides (PEIs) fulfill the legal specifications demanded by the aviation industry for aircraft interiors. Specifically, the demands on fire characteristics, stability to media and mechanical properties constitute a great challenge here. According to related art, suitable polymer foams are produced as semi-finished products. Reprocessing to give shaped articles is uneconomic in terms of time and material exploitation, for example by virtue of large amounts of cutting waste. The material is suitable in principle and can be processed to give particle foam mouldings. These mouldings can be produced without reprocessing in short cycle times and, hence, economically. Furthermore, this gives rise to new means of functional integration, for example by direct incorporation of inserts etc. in the foam, and with regard to freedom in terms of design.

The present invention aims to provide a porous polyvinyl acetal object and a nonwoven polyvinyl acetal fabric each capable of exhibiting significantly high shock absorption. Provided is a porous polyvinyl acetal object having a large number of cells, including: a polyvinyl acetal; and a plasticizer, the porous object having an open cell ratio of 10% or higher, the porous object in the form of a sample with a size of 10 cm in length, 10 cm in width, and 4 mm in thickness having a coefficient of rebound (rebounding height/drop height) of 0.1 or lower in measurement of a rebounding height of a -inch SUS ball in conformity with JIS B 1501 dropped from a given drop height to the center of the sample placed on an iron plate with a size of 10 cm or more in length, 10 cm or more in width, and 1 cm in thickness.

An example device includes a nanovoided polymer element, a first electrode, and a second electrode. The nanovoided polymer element may be located at least in part between the first electrode and the second electrode. In some examples, the nanovoided polymer element may include anisotropic voids. In some examples, anisotropic voids may be elongated along one or more directions. In some examples, the anisotropic voids are configured so that a polymer wall thickness between neighboring voids is generally uniform. Example devices may include a spatially addressable electroactive device, such as an actuator or a sensor, and/or may include an optical element. A nanovoided polymer layer may include one or more polymer components, such as an electroactive polymer.

A form birefringent optical element includes a structured layer and a dielectric environment disposed over the structured layer. At least one of the structured layer and the dielectric environment includes a nanovoided polymer, the nanovoided polymer having a first refractive index in an unactuated state and a second refractive index different than the first refractive index in an actuated state. Actuation of the nanovoided polymer can be used to reversibly control the form birefringence of the optical element. Various other apparatuses, systems, materials, and methods are also disclosed.

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.

Examples include a device including a nanovoided polymer element having a first surface and a second surface, a first plurality of electrodes disposed on the first surface, a second plurality of electrodes disposed on the second surface, and a control circuit configured to apply an electrical potential between one or more of the first plurality of electrodes and one or more of the second plurality of electrodes to induce a physical deformation of the nanovoided polymer element.

An example device includes a nanovoided polymer element, which may be located at least in part between the electrodes. In some examples, the nanovoided polymer element may include anisotropic voids, including a gas, and separated from each other by polymer walls. The device may be an electroactive device, such as an actuator having a response time for a transition between actuation states. The gas may have a characteristic diffusion time (e.g., to diffuse half the mean wall thickness through the polymer walls) that is less than the response time. The nanovoids may be sufficiently small (e.g., below 1 micron in diameter or an analogous dimension), and/or the polymer walls may be sufficiently thin, such that the gas interchange between gas in the voids and gas absorbed by the polymer walls may occur faster than the response time, and in some examples, effectively instantaneously.

Provided is a unique class of foam materials characterized by regions of material unidirectionality. The foam materials are configured for a great variety of end-use applications as core materials or as materials in construction of multilayered structures. The novel and ingenious process for making the composite materials of the invention, permits modifying the foam materials to suite any specific end use.