Process of forming polymeric material
A method for forming an article includes providing a sheet of material, optionally conditioning the sheet with a surface of a roller, forming the sheet to provide a web, and separating an article from the web to provide the article. An apparatus adapted to form the article from a sheet is provided.
1. A method of providing an article, the method comprising
providing a sheet comprising polymeric materials,
conditioning the sheet with a surface of a rotating roller and the surface of the rotating roller has a surface roughness of greater than about 80 Ra (microinches) and less than about 380 Ra (microinches),
rotary thermoforming the sheet onto a mold to provide an article-blank web,
cutting the article-blank web to form a carrier web and an article preform coupled with the carrier web after molding the sheet, and
separating the article preform from the carrier web to provide the article,
wherein the polymeric materials comprise polypropylene and the article has a thickness of between about 0.010 inches and about 0.012 inches and is within three sigma of a gram weight standard deviation of 0.050 grams or more and 0.110 grams or less.
2. The method of claim 1 , wherein the surface roughness of the surface of the rotating roller is equal to or greater than about 100 Ra (microinches) and less than about 380 Ra (microinches).
3. The method of claim 1 , wherein the rotary thermoforming stage includes applying the sheet to a single-sided tool without positive pressure being applied to the sheet opposite the mold and wherein the mold protrudes outwardly away from the single-sided tool to engage the sheet.
4. The method of claim 1 , wherein the article has the thickness of about 0.012 inches and is within three sigma of the gram weight standard deviation of 0.06 grams.
5. The method of claim 1 , wherein the article has the thickness of about 0.010 inches and is within three sigma of the gram weight standard deviation of 0.1 grams.
6. The method of claim 1 , wherein the article has a clarity of about or greater than about 40% as measured using ASTM D 1746 and a haze of about or less than about 70% as measured using ASTM D 1003 procedure B.
7. The method of claim 1 , wherein the polymeric materials have a shrinkage rate of about or greater than about 0.008 inches per inch.
8. The method of claim 1 , wherein the cutting the article-blank web to form the carrier web includes making incisions in the article-blank web to cause the article preforms to be coupled with the carrier web at one or more discrete joints and wherein separating the article preform from the carrier web to provide the article includes applying a force to the discrete joints to separate the article preforms from the carrier web.
9. The method of claim 1 , wherein the surface roughness of the surface of the rotating roller is greater than a surface roughness of the article.
10. The method of claim 9 , wherein a surface roughness of the mold is greater than the surface roughness of the article and the surface roughness of the mold is less than the surface roughness of the surface of the rotating roller.
11. A method of providing a thermoformed article, the method comprising
providing a single-layer sheet comprising polymeric materials comprising a polypropylene impact copolymer,
conditioning the single-layer sheet with a surface of a rotating roller having a surface roughness of greater than about 100 Ra (microinches) and less than about 400 Ra (microinches),
thermoforming the single-layer sheet onto a mold to provide an article-blank web having a plurality of article blanks formed therein after conditioning the single-layer sheet, and
cutting the article-blank web after thermoforming the single-layer sheet to provide the thermoformed article, and
wherein the thermoformed article has a surface roughness that is less than the surface roughness of the surface of the rotating roller.
12. The method of claim 11 , wherein the thermoforming stage is performed using a rotary thermoformer and the cutting stage is performed using a rotary cutter.
13. The method of claim 11 , wherein the cutting the article-blank web includes rotating a rotor die included in a rotary cutter about an axis, measuring a distance between the rotor die and a first article blank included in the plurality of article blanks located upstream of the rotor die, varying a rotational speed of the rotor die based on the distance, and applying pressure to the article-blank web with the rotor die.
14. The method of claim 11 , wherein the surface roughness of the surface of the rotating roller is between about 100 Ra (microinches) and about 240 Ra (microinches).
15. The method of claim 11 , wherein the thermoforming stage includes applying the single-layer sheet to a rotary thermoformer, the rotary thermoformer including a rotor mounted to rotate about a rotation axis of the rotary thermoformer, the mold which is coupled to the rotor for rotation therewith, and a curl-blocking strip coupled to the rotor and including a plurality of protrusions that extend radially outward away from the rotor toward the single-layer sheet to engage and block the single-layer sheet from curling away from the rotor during the rotary thermoforming stage.
16. The method of claim 11 , wherein the surface roughness of the surface of the rotating roller is at least 2 times greater than the surface roughness of the article.
17. The method of claim 16 , wherein the surface roughness of the surface of the rotating roller is equal to or greater than about 100 Ra (microinches) and less than about 400 (microinches).
18. A method of providing a thermoformed article, the method comprising
extruding a sheet comprising polymeric materials,
conditioning the sheet with a surface of a rotating roller having a surface roughness of between about 100 Ra (microinches) and about 400 Ra (microinches) to block axial and circumferential movements of the sheet relative to a longitudinal axis of the rotating roller,
rotary thermoforming the sheet onto a mold to provide an article-blank web after conditioning the sheet without applying a positive pressure to the sheet opposite the mold during the rotary thermoforming stage, and cutting the article-blank web after rotary thermoforming the sheet to provide the thermoformed article,
wherein the thermoformed article has a surface roughness that is less than the surface roughness of the surface of the rotating roller.
19. The method of claim 18 , wherein the polymeric materials include only non-aromatic polymeric materials.
20. The method of claim 18 , wherein the surface roughness of the surface of the rotating roller is at least 2 times greater than the surface roughness of the thermoformed article.