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A new L-shell output allows simulation of multilayer systems. An improved harmonic solver has been added, which allows modes up to second stiffness ( harmonic ) to be accurately simulated. ) and sixth order with lower-order approximation) In addition, an improved implicit solution (polynomial.
March 18, 2020 - Explicit analysis has been improved in three key areas, both for . A new L-shell output allows simulation of multilayer systems. An improved harmonic solver has been added, which allows modes up to second stiffness ( harmonic ) to be accurately simulated. ) and sixth order with lower-order approximation) In addition, an improved implicit solution (polynomial.This invention relates to polyetherimide resin compositions. More particularly, this invention relates to polyetherimide resin compositions which contain polyethylene glycols and which, when molded, are transparent and self-supporting.
Polyetherimides having recurring imide groups are well known in the art. They are characterized by excellent heat resistance, toughness and good mechanical strength. A particularly desirable property is the ability of such polymers to be molded at temperatures of at least 300.degree. F.
The conventional polyetherimides are provided in the form of powders or pellets which may be formed into shaped articles by such techniques as extrusion, compression molding or injection molding. However, the molded articles produced from the polyetherimides typically contain voids or are opaque due to the high crystallinity of these polymers.
U.S. Pat. No. 3,842,111 and U.S. Pat. No. 3,879,365 describe the preparation of polyetherimides having low degrees of crystallinity by first reacting an aromatic tetracarboxylic acid anhydride with a diamine in the presence of a catalyst to form a polyimide, and then reacting the polyimide with a glycol or a mixture of glycols to form the corresponding polyetherimide.
U.S. Pat. No. 3,857,822 describes a process for preparing polyetherimide resins having a weight average molecular weight of from about 4,000 to about 100,000 and a content of the imide groups of from about 50 to 100 percent by weight of the polymer. This patent discloses the use of glycols having molecular weights in the range of from 400 to about 1, 3125841983

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