Sealing diaphragm and methods of manufacturing said diaphragm
Described is a method for manufacturing a diaphragm assembly through the use of injection molding. The method can avoid the use of PTFE as a chemically resistant coating. Further, the method can increase overall adherence of a polymer diaphragm to an insert through the use of an interference surface on at least the surface of a head of the insert.
1. A method for manufacturing a diaphragm assembly comprising:
forming an insert having a head and a body, wherein the head is located at one end of the body;
forming at least one interference surface on the insert;
disposing the insert within a cavity configured for injection molding, wherein at least the head is completely disposed within the cavity; and
injection molding a polymer onto the insert, wherein the polymer is configured to adhere to the head and the at least one interference surface of the insert;
wherein the polymer is a PVDF polymer comprising 0.5% by weight natural PVDF and 99.5% by weight of a PVDF polymer having a density of 1.77 grams per cubic centimeter, a water absorption of 0.030%, a tensile yield strength of 6.50 MPa, an elongation at break of greater than 50%, an elongation at yield of 20%, a tensile modulus of 0.0800 GPa, a melting point of 101° C., a deflection temperature at 1.8 MPa of 46.0°, an oxygen index of 40%, and a melt viscosity in a range between 12.0 and 20.0 kilopoise when said melt viscosity is tested at 232° C. according to American Standard Test Method D3835.
2. The method of claim 1 , wherein the head has a diameter greater than the diameter of the body.
3. The method of claim 1 , wherein forming the at least one interference surface comprises forming the at least one interference surface at approximately the center of the head of the insert.
4. The method of claim 1 , wherein forming at least one interference surface comprising forming a plurality of interference surfaces on the head of the insert.
5. The method of claim 1 , wherein PTFE is not used.
6. The method of claim 1 , wherein forming the at least one interference surface comprises tapping at least one hole into the head of the insert to form a blind tapped hole.
7. The method of claim 3 , wherein the forming the at least one interference surface further comprising forming at least four pairs of interference surfaces.
8. The method of claim 1 , wherein the at least one interference surface is located on the outside of the head.
9. The method of claim 8 , wherein the at least one interference surface comprises threads or grooves.
10. A two part diaphragm assembly comprising:
an insert having a head and a body, wherein the head is located at one end of the body;
at least one interference surface formed on the insert; and
an injection-molded polymer diaphragm configured to at least partially surround the head of the insert and interfere with the at least one interference surface, wherein the polymer is a PVDF polymer comprising 0.5% by weight natural PVDF and 99.5% by weight of a PVDF polymer having a density of 1.77 grams per cubic centimeter, a water absorption of 0.030%, a tensile yield strength of 6.50 MPa, an elongation at break of greater than 50%, an elongation at yield of 20%, a tensile modulus of 0.0800 GPa, a melting point of 101° C., a deflection temperature at 1.8 MPa of 46.0°, an oxygen index of 40%, and a melt viscosity in a range between 12.0 and 20.0 kilopoise when said melt viscosity is tested at 232° C. according to American Standard Test Method D3835.
11. The assembly of claim 10 , wherein the polymer is semi-transparent.
12. The assembly of claim 10 , wherein the polymer is transparent.
13. The assembly of claim 10 , wherein the at least one interference surface is located approximately at the center of the insert.
14. The assembly of claim 10 , wherein PTFE is not used.
15. The assembly of claim 10 , wherein the insert is metal.
16. The assembly of claim 10 , wherein the body of the insert comprises a thread.
17. The assembly of claim 10 , wherein the at least one interference surface is a blind tapped hole.
18. The assembly of claim 10 , wherein the insert further comprises at least one additional interference surface.
19. The assembly of claim 18 , wherein the at least one additional interference surface is configured as a through hole through the head.
20. The assembly of claim 10 , wherein the at least one interference surface comprises at least four pairs of interference surfaces.
21. The assembly of claim 20 , wherein the at least one interference surface comprises four holes approximately equally spaced around the center of the insert and a fifth hole located at the center of the insert.
22. The assembly of claim 10 , wherein the at least one interference surface extends into the body.
23. The assembly of claim 10 , wherein the polymer diaphragm forms an air tight seal around the insert.
24. The assembly of claim 10 , wherein the at least one interference surface has a rounded end.
25. The assembly of claim 10 , wherein the at least one interference surface is located on the outside of the head.
26. The assembly of claim 25 , wherein the at least one interference surface comprises threads or grooves.
27. A positive displacement pump comprising:
an input channel;
an output channel; and
a diaphragm assembly located between the input and output channel and configured to translate liquid from the input channel to the output channel, the assembly comprising:
an insert having a head and a body, wherein the head is located at one end of the body;
at least one interference surface formed on the insert; and
an injection-molded polymer diaphragm configured to at least partially surround the head of the insert and interfere with the at least one interference surface, wherein the polymer is a PVDF polymer comprising 0.5% by weight natural PVDF and 99.5% by weight of a PVDF polymer having a density of 1.77 grams per cubic centimeter, a water absorption of 0.030%, a tensile yield strength of 6.50 MPa, an elongation at break of greater than 50%, an elongation at yield of 20%, a tensile modulus of 0.0800 GPa, a melting point of 101° C., a deflection temperature at 1.8 MPa of 46.0°, an oxygen index of 40%, and a melt viscosity in a range between 12.0 and 20.0 kilopoise when said melt viscosity is tested at 232° C. according to American Standard Test Method D3835.