Molding corners and end caps to EPDM weatherseals. (Tech Service).Santoprene thermoplastic A polymer material that turns to liquid when heated and becomes solid when cooled. There are more than 40 types of thermoplastics, including acrylic, polypropylene, polycarbonate and polyethylene. rubbers 121-65W233 (65 durometer A) and 121-79W233 (79 durometer A) are specially formulated thermoplastic vulcanizates (TPVs) which bond to vulcanized vul·ca·nize tr.v. vul·ca·nized, vul·ca·niz·ing, vul·ca·niz·es To improve the strength, resiliency, and freedom from stickiness and odor of (rubber, for example) by combining with sulfur or other additives in the presence of heat thermoset A polymer-based liquid or powder that becomes solid when heated, placed under pressure, treated with a chemical or via radiation. The curing process creates a chemical bond that, unlike a thermoplastic, prevents the material from being remelted. See thermoplastic. EPDM EPDM Ethylene-Propylene-Diene-Monomer EPDM Enterprise Product Data Management EPDM Ethylene Propylene Dimonomer (industrial/commercial piping/plumbing components) EPDM Engineering Product Data Management (sulfur and peroxide peroxide (pərŏk`sīd), chemical compound containing two oxygen atoms, each of which is bonded to the other and to a radical or some element other than oxygen; e.g. cured) through physical interaction at elevated temperatures. Typical applications are: * Hard corner molding for glass-run channels; * end caps for beltline seals and hood seals; and * fixation fixation: see psychoanalysis. parts for any type of complex weatherseals. Data are available in the literature (ref. 1). Additional heat aging data and adhesion adhesion /ad·he·sion/ (ad-he´zhun) 1. the property of remaining in close proximity. 2. the stable joining of parts to one another, which may occur abnormally. 3. properties at different temperatures are shown in tables 1 and 2. Part design Part design of corners and end caps is very important. The highest bond strength will be developed and maintained by following a few guidelines guidelines, n.pl a set of standards, criteria, or specifications to be used or followed in the performance of certain tasks. : * Avoid severe undercuts--demolding of thermoplastic rubber parts is more critical than for thermoset rubber parts; * always create the largest surface area to yield the strongest bond; * maximize overlaps on shear-joints in non-visible areas to increase overall bond strength. Mold design The extrusion profile must be clamped to stop it from being pushed out of the tool under injection pressures. This can be achieved by adding stopper/grip pins of 2.0-2.5 mm (0.079 to 0.098") diameter. The height of the stopper pins should be 50 to 60% of the profile thickness. If the stopper pins are too high, they can be ground to the required size. The pins should be located 2-3 mm (0.079 to 0.118") away from the EPDM/ 121-65/79 W233 interface. A schematic A graphical representation of a system. It often refers to electronic circuits on a printed circuit board or in an integrated circuit (chip). See logic gate and HDL. is shown in figure 1. [FIGURE 1 OMITTED] Design efficient cooling channels in the mold to obtain a short cooling time (Law) such a lapse of time as ought, taking all the circumstances of the case in view, to produce a subsiding of passion previously provoked. - Wharton. See also: Cooling . Use a well-designed venting venting, n an exit passage constructed in a casting mold to allow gases to escape during the casting process. venting Ventilation Psychology The verbalization* of one's 'emotional baggage' to another person; qvetching system with a maximum channel depth up to 0.038 mm (0.0015"). Since high injection speed is required to achieve high bond strength, adequate venting is critical for this application to reduce gas trapping trapping, most broadly, the use of mechanical or deceptive devices to capture, kill, or injure animals. It may be applied to the practice of using birdlime to capture birds, lobster pots to trap lobsters, and seines to catch fish. . Trapped gas can reduce the bond strength at the EPDM and 121-65/79W233 interface. If there are blind areas, such as the bottom of a hole or at the interface, it is suggested to place a flattened flat·ten v. flat·tened, flat·ten·ing, flat·tens v.tr. 1. To make flat or flatter. 2. To knock down; lay low: The boxer was flattened with one punch. ejector ejector (ijekt  r),n by common usage, a device used to remove debris and fluids by negative pressure. Another term is aspirator. See also aspirator. pin in that area. Venting of the runner system is also recommended. A core that is thick, sintered/porous metal is effective in eliminating air entrapment entrapment, in law, the instigation of a crime in the attempt to obtain cause for a criminal prosecution. Situations in which a government operative merely provides the occasion for the commission of a criminal act (e.g. . The porous porous /por·ous/ (por´us) penetrated by pores and open spaces. po·rous adj. 1. Full of or having pores. 2. Admitting the passage of gas or liquid through pores. metal should be located at the EPDM/12165/79W233 interface (ref. 2). Use a runner system that is as short as possible to fill the corner or end cap. This will ensure low flow resistance. Full round runners are recommended since they have the smallest surface-to-volume ratio and most efficient cross-section for pressure transmission and heat retention. If full round runner systems cannot be used, it is recommended to use modified trapezoidal runners, which consist of a round bottom with a 5[degrees] taper on the walls. This type of geometry has been proven to provide more efficient melt flow. Half-round runners are not recommended. Shrinkage Shrinkage The amount by which inventory on hand is shorter than the amount of inventory recorded. Notes: The missing inventory could be due to theft, damage, or book keeping errors. information for the TPVs is provided in table 3. In most cases, shrinkage is minimum for these grades over EPDM. The TPVs will create a fusion bond to the EPDM, which will constrain con·strain tr.v. con·strained, con·strain·ing, con·strains 1. To compel by physical, moral, or circumstantial force; oblige: felt constrained to object. See Synonyms at force. 2. the rubber so it cannot shrink. Preparation of extrusion profiles To achieve good bond strength between the EPDM and the TPV TPV Temporary Protection Visa (Australia) TPV Terminal Punto Venta TPV Third-Party Verification TPV Thermophotovoltaic TPV Thermoplastic Vulcanizate (thermoplastic elastomer) TPV Total Payment Volume interface, the following guidelines should be followed: * Use freshly cut extrusion profiles (1-2 hours maximum) prior to molding. Longer periods will increase the chance of contamination and thus minimize bond strength. * Extrusion cut should be uniform and not ragged rag·ged adj. 1. Tattered, frayed, or torn: ragged clothes. 2. Dressed in tattered or threadbare clothes: a ragged scarecrow. 3. . It is recommended to keep the cutting device sharp, so that the top layer of the extrusion does not curve in and provide a fault-prone point. * Silicone-based mold release is not recommended since silicone silicone, polymer in which atoms of silicon and oxygen alternate in a chain; various organic radicals, such as the methyl group, CH3, are bound to the silicon atoms. inhibits adhesion. Airborne silicone is detrimental det·ri·men·tal adj. Causing damage or harm; injurious. det  ri·men to adhesion, and
silicone-based slip coating is also not recommended.* Vertical miter miter bishop’s headdress signifying his authority. [Christian Symbolism: EB VI] See : Authority cuts (perpendicular to the extrusion) have been found to provide more consistent parts than straight cut profiles. Processing These TPVs are shear shear: see strength of materials. Shear A straining action wherein applied forces produce a sliding or skewing type of deformation. dependent materials that can be processed on conventional thermoplastic equipment for injection molding injection molding n. A manufacturing process for forming objects, as of plastic or metal, by heating the molding material to a fluid state and injecting it into a mold. . The molding equipment should have adequate injection pressure/speed and holding pressure/time control combined with accurate temperature control. Good, solid packing of the part will contribute to maximum bond strength. These two grades should be dried at 82[degrees]C (180[degrees]F) for four hours prior to processing. Recommended melt temperature for the TPVs is between 220-260[degrees]C (430-500[degrees]F). Using these elevated melt temperatures, polymer degradation Polymer degradation is a change in the properties - tensile strength, colour, shape, etc - of a polymer or polymer based product under the influence of one or more environmental factors such as heat, light or chemicals. may occur if the molding machine (Woodworking) A planing machine for making moldings (Founding) A machine to assist in making molds for castings. See also: Molding Molding is left standing idle for longer than 10-15 minutes. A melt temperature over 230[degrees]C (450[degrees]F) may cause drooling drooling the discharge of saliva from the mouth. A normal feature in some breeds of dogs such as St. Bernard, Newfoundland and English bulldog, presumably because of their loose, pendulous lips. from the nozzle An orifice in an inkjet print head through which ink is sprayed onto the paper. Print heads with six thousand or more nozzles are common in today's printers. Nozzle . To compensate for a large barrel, use a lower temperature in the rear zone so the material is not subject to high heat settings during its long residence time. The recommended processing conditions for start up are shown in table 4. An increase in cooling time increases the bond strength between the EPDM and the TPV interface. Discussion Processing these TPVS at their highest melt temperature (260[degrees]C [500[degrees]F]) and using a mold temperature of 40[degrees]C (105[degrees]F) will yield a strong bond to the EPDM profile. Cooler temperatures may provide a faster cycle time, but bond strength will be sacrificed. If bond strength of corners or end caps needs to be increased, the following process modifications can be implemented (these do not apply to profiles less than 5 mm [0.20"] thick): * If the EPDM profile cross-section thickness is above 5 mm (0.195"), preheat pre·heat tr.v. pre·heat·ed, pre·heat·ing, pre·heats To heat (an oven, for example) beforehand. pre·heat  er n. EPDM profile ends in an oven to 80 to
110[degrees]C (175-230[degrees]F), place into the mold at
20-60[degrees]C (70-140[degrees]F) and process immediately. One
disadvantage may be that the profile ends are more difficult to insert
into the mold. Prewarmed profiles will have expanded dimensions so that
insertion insertion n. the addition of language at a place within an existing typed or written document, which is always suspect unless initialled by all parties. may be more difficult and time-consuming* Place EPDM profile ends into the mold and use an external heat source (quartz spots or heat metal wedges) to only preheat the end parts to 80-110[degrees]C (175-230[degrees]F) and process immediately. This processing system may function well using a rotary table A rotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed (usually horizontal or vertical) axis. or shuttle press. * Place EPDM profile ends into a warm mold at 80-110[degrees]C (175-230[degrees]F) and allow 30 seconds to warm up. This method can only be used when corners or end caps are simple, because demolding at 93[degrees]C (200[degrees]F) could easily deform the part. The preceding recommendations on preheating the EPDM profiles are not ranked as to priority.
Table 1--adhesion properties on compression molded EPDM aging
performance after one week
Test temperature, Hot air
[degrees]C ([degrees]F) 70 (158) 100 (212) 120 (248)
Property
Santoprene rubber 121-65W233
Modulus 20%, MPa (psi) 0.6 0.8 0.9
(87) (116) (131)
Modulus 50%, MPa (psi) 1.1 1.4 1.4
(160) (203) (203)
(73) (160) (276)
Modulus 100%, MPa (psi) 2.1 2.3 2.3
(305) (334) (334)
Elongation, % 360 335 470
Ultimate tensile, MPa (psi) 2.8 2.9 3.4
(406) (421) (493)
Santoprene rubber 121-79W233
Modulus 20%, MPa (psi) 1.1 1.5 1.8
(160) (218) (261)
Modulus 50%, MPa (psi) 2.1 2.5 2.8
(305) (363) (406)
Modulus 100%, MPa (psi) 2.8 3.1 3.3
(406) (450) (479)
Elongation, % 150 210 205
Ultimate tensile, MPa (psi) 3.1 3.6 3.9
(450) (522) (566)
Test temperature, Cataplasm Fuel B Motor oil
[degrees]C ([degrees]F) 70 (158) 120 (248) 120 (248)
Property
Santoprene rubber 121-65W233
Modulus 20%, MPa (psi) 0.7 1.0 0.9
(102) (145) (131)
Modulus 50%, MPa (psi) 1.3 1.4 1.4
(189) (203) (203)
(870)
Modulus 100%, MPa (psi) 2.2 1.8 1.7
(319) (261) (247)
Elongation, % 253 315 250
Ultimate tensile, MPa (psi) 2.4 2.7 2.3
(348) (392) (334)
Santoprene rubber 121-79W233
Modulus 20%, MPa (psi) 0.9 1.5 1.6
(131) (218) (232)
Modulus 50%, MPa (psi) 1.9 2.3 2.5
(267) (334) (363)
Modulus 100%, MPa (psi) 2.7 2.8 3.0
(392) (406) (435)
Elongation, % 115 270 180
Ultimate tensile, MPa (psi) 2.8 3.6 3.4
(406) (522) (493)
Notes:
(1.) Testing was performed by overmolding 121-65W233 and 121-79W233
over an EPDM strip. S2 dumbbell-shaped samples were cut from
overmolded plaques (60 mm x 60 mm x 3 mm [2.35" x 2.35" x 0.120"])
and tested per ISO 37. The direction of pull was perpendicular to the
EPDM and 121-65/79W233 interface.
(2.) For Fuel B and motor oil testing, the S2 dumbbell-shaped samples
were exposed per ISO 1817 prior to testing per ISO 37.
Table 2--adhesion properties on compression molded
EPDM at different temperatures
Test temperature,
[degrees]C ([degrees]F)
Property 70 (158) 23 (73)
Santoprene rubber 121-65W233 0.3
Modulus 20%, MPa (psi) (44) 0.6
0.5 (87)
Modulus 50%, MPa (psi) (73) 1.1
(160)
--
Modulus 100%, MPa (psi) 1.6
96 (232)
Elongation, % 0.6 280
Ultimate tensile, MPa (psi) (87) 2.4
(348)
Santoprene rubber 121-79W233 0.4
Modulus 20%, MPa (psi) (58) 0.7
0.9 (102)
Modulus 50%, MPa (psi) (131) 1.4
1.3 (203)
Modulus 100%, MPa (psi) (189) 2.3
153 (334)
Elongation, % 1.5 170
Ultimate tensile, MPa (psi) (218) 2.9
(421)
Test temperature,
[degrees]C ([degrees]F)
Property -20 (-4) -40 (-40)
Santoprene rubber 121-65W233
Modulus 20%, MPa (psi) 1.0 3.7
(145) (537)
Modulus 50%, MPa (psi) 1.9 6.0
(276) (870)
Modulus 100%, MPa (psi) 4.0 8.2
(580) (1,189)
Elongation, % 560 202
Ultimate tensile, MPa (psi) 8.9 9.1
(1,291) (1,320)
Santoprene rubber 121-79W233
Modulus 20%, MPa (psi) 1.0 4.7
(145) (682)
Modulus 50%, MPa (psi) 2.3 7.7
(334) (1,117)
Modulus 100%, MPa (psi) 4.1 10.3
(595) (1,494)
Elongation, % 283 123
Ultimate tensile, MPa (psi) 6.8 10.5
(986) (1,523)
Note: Testing was performed by overmolding 121-65W233 and
121-79W233 over an EPDM strip. S2 dumbbell-shaped samples
were cut from overmolded plaques (60 mm x 60 mm x 3 mm [2.35"
x 2.35" x 0.120"]) and tested per ISO 37. The direction of pull was
perpendicular to the EPDM and 121-65/79W233 interface.
Table 3--shrinkage for Santoprene rubber 121-65W233
and 121-79W233
Santoprene Shrinkage Post Shrinkage
rubber grade 24 hrs. 48 hrs.
23[degrees]C 110[degrees]C
(73[degrees]F) (230[degrees]F)
121-65W233
Parallel to flow 1.35% 1.86%
Perpendicular to flow 1.39% 0.86%
121-79W233
Parallel to flow 1.45% 1.67%
Perpendicular to flow 1.38% 1.10%
Notes:
(1.) Shrinkage measurements were taken on a 60 mm x
60 mm x 3 mm (2.35" x 2.35" x 0.120") plaque with a
fan gate.
(2.) Process conditions were fixed according to grade
following our standard recommended conditions as
shown in table 4.
(3.) Test method ISO 2577.
Table 4--recommended processing conditions
for start up
Description Condition
Melt temperature 220 to 260[degrees]C
(430 to 500[degrees]F)
Injection pressure 4.8 to 6.9 MPa
(700 to 1,000 psi)
(as high as possible without
moving the profile)
Injection time Less than 2 seconds
Holding pressure 2.1 to 4.1 MPa
300 to 600 psi
(50% of injection pressure)
Holding time 4 to 10 seconds
Cooling time 25 to 35 seconds
(wall thickness dependent)
Mold temperature 40 to 55[degrees]C
(104 to 131[degrees]F)
Drying 82[degrees]C (180[degrees]F)
3 to 4 hours
References (1.) Product data sheet 121-65W233 and 121-79W233. (2.) Venting section of the Injection Molding Guide (AES-31-02). Shaival Mehta works as a Senior Engineer At Advanced Elastomer elastomer (ĭlăs`təmər), substance having to some extent the elastic properties of natural rubber. The term is sometimes used technically to distinguish synthetic rubbers and rubberlike plastics from natural rubber. Systems. Mehta has been with AES for five years, where his focus areas include design and processing TPVs. Prior to joining AES, he worked for T&M Antennas. |
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