THERMOFORMABLE POLYMERIC SHEETS BASED ON PSEUDO-AMORPHOUS POLYARYLETHER KETONE
Sheets having thicknesses of from 1000 to 10,000 microns which are useful for the production of thermoformed semi-crystalline articles are based on polyaryletherketones having viscosities at 360° C. of at least about 400 Pas at 100 s −1 as measured by parallel plate rheometer. The polyaryletherketones are in a pseudo-amorphous state in the thermoformable sheets.
1 . A semi-crystalline molded article consisting of a polymer sheet and, optionally, one or more non-nucleating additives,
wherein the sheet has a thickness of from 1000 microns to 10,000 microns and is formed from a polyaryletherketone (PAEK) polymer in a pseudo-amorphous state which has a viscosity at 360° C. of at least 400 Pa·s at 100 s −1 as measured by parallel plate rheometer.
2 . The semi-crystalline molded article of claim 1 , wherein the polymer has a viscosity at 360° C. of at least 600 Pa·s at 100 s −1 as measured by parallel plate rheometer.
3 . The semi-crystalline molded article of claim 1 , wherein the polymer has a viscosity at 360° C. of at least 800 Pa·s at 100 s −1 as measured by parallel plate rheometer.
4 . The semi-crystalline molded article of claim 1 , wherein the polymer has a viscosity at 360° C. of not more than 5000 Pa·s at 100 s −1 as measured by parallel plate rheometer.
5 . The semi-crystalline molded article of claim 1 , wherein the polyaryletherketone (PAEK) is selected from the group consisting of polyetherketoneketone (PEKK), polyetherketone (PEK), polyetherketoneetherketoneketone (PEKEKK) and combinations thereof.
6 . The semi-crystalline molded article of claim 1 , wherein the polyaryletherketone (PAEK) is polyetherketoneketone (PEKK).
7 . The semi-crystalline molded article of claim 6 , wherein the polyetherketoneketone (PEKK) has a T:I isomer ratio of from 50:50 to 90:10.
8 . The semi-crystalline molded article of claim 6 , wherein the polyetherketoneketone (PEKK) has a T:I isomer ratio of from 65:35 to 75:25.
9 . The semi-crystalline molded article of claim 6 , wherein the polyetherketoneketone (PEKK) has a T:I isomer ratio of from 68:32 to 72:28.
10 . The semi-crystalline molded article of claim 6 , wherein the polyetherketoneketone (PEKK) has a T:I isomer ratio of about 70:30.
11 . The semi-crystalline molded article of claim 1 , wherein the sheet contains of one or more non-nucleating additives.
12 . The semi-crystalline molded article of claim 1 , wherein the one or more non-nucleating additives are selected from the group consisting of fillers, reinforcement fibers, pigments, thermal stabilizers, antioxidants, glass spheres, silica, and talc.
13 . The semi-crystalline molded article of claim 1 , wherein the sheet is transparent.
14 . A method of manufacturing the semi-crystalline article of claim 1 , wherein the method comprises thermoforming the polymer sheet in a mold.
15 . A method of manufacturing the semi-crystalline article of claim 1 , the method comprising:
a) as a softening step, heating the polymer sheet to a temperature above the glass transition temperature of the PAEK polymer to soften the PAEK polymer;
b) as a crystallization step, heating the polymer sheet to a temperature above the glass transition temperature of the PAEK polymer and below the melting temperature of the PAEK polymer for a time sufficient to allow the PAEK polymer to crystallize;
c) placing the polymer sheet on a mold during either the softening step or the crystallization step before crystallization takes place; and
d) forming the semi-crystalline molded article.
16 . The semi-crystalline article of claim 1 , wherein the semi-crystalline article exhibits less than 3% dimensional change compared to the mold.
17 . A method of making the polymer sheet in accordance with claim 1 , wherein the method comprises:
a) heating a resin composition comprised of the PAEK polymer to a suitable processing temperature above the melting point of the PAEK polymer to provide a molten resin composition;
b) forming the molten resin composition into a sheet; and
c) quenching the sheet at a rate effective to obtain the PAEK polymer in a pseudo-amorphous state.
18 . A method of forming a semi-crystalline article, wherein the method comprises:
selecting a polyaryletherketone (PAEK) in a pseudo-amorphous state which has a viscosity at 360° C. of at least 400 Pa·s at 100 s −1 as measured by parallel plate rheometer;
extruding the PAEK into a polymer sheet with a thickness of from 1,000 microns to 10,000 microns;
thermoforming the PAEK polymer sheet into the semi-crystalline article, wherein the thermoforming includes:
a) as a softening step, heating the PAEK polymer sheet to a temperature above the glass transition temperature of the PAEK to soften the polymer sheet;
b) as a crystallization step, heating the PAEK polymer sheet to a temperature above the glass transition temperature of the PAEK and below the melting temperature of the PAEK for a time sufficient to allow the polymer sheet to crystallize;
c) placing the PAEK polymer sheet on a mold during either the softening step or the crystallization step before crystallization takes place; and
d) forming the semi-crystalline article,
wherein the crystallization step occurs at 210 to 280° C.