Inserts encapsulated with a thermoplastic sheet material via compression molding
AssigneeE. I. Du Pont de Nemours and Company
InventorsM. Lana Sheer, Lloyd Fox, John Carl Solenberger
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Abstract
This invention relates to metal-containing inserts, such as transformers, that are encapsulated, via compression molding processes, with at least one wet lay thermoplastic sheet material and that do not experience significant visible cracking during heat cycling.
Claims13
A metal-containing insert which is encapsulated with at least one layer of a thermoplastic sheet material, said thermoplastic sheet material comprising a thermoplastic polymer and a glass fiber material selected from glass fibers having a length greater than 3.175 mm (1/8 inch) or a mixture of said glass fibers having a length greater than 3.175 mm (1/8 inch) with flakes or spheres and wherein said thermoplastic sheet material is prepared by:
- (a) co-dispersing said thermoplastic polymer and said glass fiber material into water to form an aqueous slurry;
- (b) depositing said slurry on a forming wire;
- (c) de-watering said slurry to form a fibrous mat;
- and
- (d) drying said mat;
- said encapsulation being accomplished by a compression molding process which includes the steps of:
- (i) heating said thermoplastic sheet material to a temperature which is above the melting point but below the degradation point of the polymer;
- (ii) exposing a portion of the insert to be encapsulated;
- (iii) placing said sheet material over the exposed portion of said insert;
- (iv) forcing the heated thermoplastic sheet material around the exposed portion of said insert;
- and
- (v) repeating the process until all exposed portions of said insert have been encapsulated with at least one layer of said thermoplastic sheet material.
The encapsulated electrically functional device in which the encapsulant comprises at least one layer of a wet lay thermoplastic sheet material in which said wet lay thermoplastic sheet material, before encapsulation, comprises a fibrous mat comprising a thermoplastic polymer selected from the group consisting of polyesters, polyamides, acrylics, thermoplastic elastomers, rubbers, partially cross-linked halogenated polyolefin alloys compounded with plasticizers and stabilizers, polyolefins and mixtures thereof, and a glass fiber material selected from glass fibers having a length greater than 3.175 mm (1/8 inch) or a mixture of said glass fibers having a length greater than 3.175 mm(1/8 inch) with flakes or spheres, and said glass fiber material comprises greater than 70 weight percent glass fibers.
Dependencies are inferred from the claim text.