Composite article and related methods
A composite article comprises an article presenting a surface and a thermally expandable composition disposed on the surface of the article. The thermally expandable composition comprises (a) from about 35 to about 65 percent by weight of a polyolefin resin; (b) from about 2 to about 15 percent by weight of a thermoplastic resin; (c) from about 1 to about 6 percent by weight of a curing agent suitable for cross-linking the polyolefin resin (a); (d) from about 15 to about 45 percent by weight of filler; and (e) from about 1 to about 10 percent by weight of a chemical blowing agent which is activated at an activation temperature, each based on the total weight of the thermally expandable composition. Methods of preparing and using the composite article, and an assembly formed from the composite article, are also disclosed.
1. A composite article, comprising:
a fastener comprising: an elongated body presenting a surface;
a head joined with the elongated body and
a thermally expandable composition disposed at least partially circumferentially about the elongated body, the thermally expandable composition comprising:
(a) from about 45 to about 65 percent by weight of a copolymer of ethylene and methacrylic acid and an acid-modified ethylene acrylate resin;
(b) from about 2 to about 15 percent by weight of a thermoplastic resin;
(c) from about 1 to about 6 percent by weight of a curing agent comprising peroxyester for cross-linking the (a) polyolefin resin;
(d) from about 30 to about 35 percent by weight of filler;
(e) from about 1 to about 10 percent by weight of a chemical blowing agent comprising 4,4′-oxybis(benzensulfonyl hydrazide), which is activated at activation temperature;
(f) a processing oil; and
(g) m-phenylenedimaleimide accelerator; each based on the total weight of the thermally expandable composition.
2. The composite article of claim 1 , wherein the thermally expandable composition is disposed circumferentially about the elongated body.
3. The composite article of claim 1 , wherein the (a) polyolefin resin has a processing temperature within a range of from about 130 to about 285° C.
4. The composite article of claim 1 , wherein the (b) thermoplastic resin: (i) comprises a hydrocarbon resin; (ii) has a softening point within a range of from about 95 to about 120° C. according to ASTM E28: (iii) is nonreactive with components (a) and (c)-(g); or (iv) a combination of (i)-(iii).
5. The composite article of claim 4 , wherein the (b) thermoplastic resin comprises the hydrocarbon resin, and the hydrocarbon resin comprises an aromatic hydrocarbon resin.
6. The composite article of claim 1 , wherein the (d) filler comprises (i) an organic filler; (ii) an inorganic filler, or (iii) both (i) and (ii).
7. The composite article of claim 6 , wherein the (d) filler comprises the organic filler, and the organic filler comprises carbon black.
8. A method of preparing the composite article of claim 1 , said method comprising;
providing the fastener comprising an elongated body presenting a surface, and a head joined with the elongated body;
thermoforming the thermally expandable composition at a first elevated temperature less than the activation temperature of the chemical blowing agent;
extruding the thermally expandable composition over a mandrel such that the thermally expandable composition is a tube extending between first and second ends and defining a cavity also extending between the first and second ends;
disposing the elongated body of the fastener through the cavity such that the thermally expandable composition is disposed at least partially circumferentially about the elongated body.