Primerless waterborne flock adhesive for bonding to TPE/TPV for weatherstrip.Currently, the majority of automotive weatherstrip applications use EPDM rubber EPDM rubber (ethylene propylene diene monomer rubber) is an elastomer which is characterized by wide range of applications. EPDM rubber is used in vibrators and seals; glass-run channel; radiator, garden and appliance hose; tubing; washers; belts; and electrical insulation. . But with the push to make more parts recyclable re·cy·cle tr.v. re·cy·cled, re·cy·cling, re·cy·cles 1. To put or pass through a cycle again, as for further treatment. 2. To start a different cycle in. 3. a. , there is serious consideration being taken to convert to thermoplastic elastomers Thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both thermoplastic and elastomeric properties. (TPE TPE Thermoplastic Elastomer TPE Terminal de Paiement Electronique (French) TPE Total Power Exchange TPE Twisted Pair Ethernet TPE Tampines Expressway (Singapore) TPE Therapeutic Plasma Exchange ) or 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. vulcanizates (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 ). Not only does the use of TPVs allow for recycling recycling, the process of recovering and reusing waste products—from household use, manufacturing, agriculture, and business—and thereby reducing their burden on the environment. , but it will allow manufacturing to switch to an ecologically friendlier aqueous aqueous /aque·ous/ (a´kwe-us) 1. watery; prepared with water. 2. see under humor. a·que·ous adj. flock adhesive adhesive, substance capable of sticking to surfaces of other substances and bonding them to one another. The term adhesive cement is sometimes used in place of adhesive, especially when referring to a synthetic adhesive. . With this new materials change, the processing of the extrusions will change and allow aqueous adhesives to be implemented. This article will review the current 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 process and adhesives technologies. Then, the new TPV process will be described and compared to an EPDM extrusion line. Finally, the performance of the newly developed aqueous adhesive will be compared to the EPDM flock specifications. Current process for EPDM flocking The current process of making an EPDM extrusion can take either of two routes. The first route is a "green line," where the flock adhesive and rubber are cured together and require a single set of ovens for processing (figure 1). The other process is called a "split line." In this set-up the rubber is partially cured (60-80%), cooled and the flock adhesive is applied (figure 2). The extrusion is then run through another set of ovens where the flock adhesive is cured. Both processes have advantages and disadvantages. In the green line process, the adhesive is applied to a substrate The base layer of a structure such as a chip, multichip module (MCM), printed circuit board or disk platter. Silicon is the most widely used substrate for chips. Fiberglass (FR4) is mostly used for printed circuit boards, and ceramic is used for MCMs. that can have temperatures from 93-149 [degrees]C, which means that the adhesive system needs to remain fluid long enough for the flock fiber to penetrate into the adhesive film. The maximum temperature of the extrusion is limited to the temperature at which the flock fibers will melt, which extends the dwell time The time cargo remains in a terminal's in-transit storage area while awaiting shipment by clearance transportation. See also storage. in the cure ovens. Since the adhesive is being applied to an uncured surface, the use of pre-treatment is generally not required. On the split line, the adhesive is applied after the initial curing of the EPDM compound. Since there are no flock fibers or adhesive on the part, the initial rubber cure can be accomplished at higher temperature. This leads to higher line speeds and shorter oven sections. Unfortunately, the extrusion needs to be cooled, followed by a surface pre-treatment (corona Corona, city, United States Corona (kərō`nə), city (1990 pop. 76,095), Riverside co., S Calif.; inc. 1896. The city developed as a primary citrus fruit producer and shipping center. There is also light manufacturing. , plasma, primed, abraded, etc.). Following the pretreatment pretreatment, n the protocols required before beginning therapy, usually of a diagnostic nature; before treatment. pretreatment estimate, n See predetermination. , the adhesive is applied and the flock fiber embedded Inserted into. See embedded system. into the wet adhesive. Finally, the flocked extrusion is cured in the next set of ovens. Fortunately, since you are only trying to cure the adhesive, the cure time can be very short. Process changes and advantages of flocking TPV compounds TPV processing is much simpler than EPDM in that there is no need to cure the material to achieve the desired profile dimensions. Instead of cure ovens, all that is required is a water quench quench, v to cool a hot object rapidly by plunging it into water or oil. quench to put out, extinguish, or suppress; to cool (as hot metal) by immersing in water. to reduce the TPV's temperature to be-low its softening softening /sof·ten·ing/ (sof´en-ing) malacia. softening a change of consistency, with loss of firmness or hardness. point (figure 3). However, when it comes to flocking TPV, this is where the process gets more complex. The majority of TPVs commonly used in the automotive weatherstrip industry are based upon a polypropylene polypropylene (pŏl'ēprō`pəlēn), plastic noted for its light weight, being less dense than water; it is a polymer of propylene. It resists moisture, oils, and solvents. (PP) continuous phase and the use of cured EPDM (to give the material its flexibility). Therefore, PP is the surface that is being bonded. PP is very difficult to bond, and that is the reason that special processes must be implemented in order to achieve acceptable flock performance. The reasons that PP substrates are difficult to bond are two-fold. One is the fact that the surface energy of the PP is very low, which does not allow higher surface energy liquids to wet the substrate. This results in coating imperfections such as fish eyes, orange peel, as well as leveling problems. The second reason that it is difficult to bond to PP is that it is an inert inert /in·ert/ (in-ert´) inactive. in·ert adj. 1. Sluggish in action or motion; lethargic. 2. polymer with few available active sites for the adhesive to react. In order to achieve good 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. to the TPV with standard adhesives, the surface must be modified with a plasma treatment or a primer prim·er n. A segment of DNA or RNA that is complementary to a given DNA sequence and that is needed to initiate replication by DNA polymerase. . Other techniques used to adhere to adhere to verb 1. follow, keep, maintain, respect, observe, be true, fulfil, obey, heed, keep to, abide by, be loyal, mind, be constant, be faithful 2. EPDM have not been totally successful. Even the primers that are used for EPDM do not always work, so special primers for TPVs must be employed. Also, the use of corona treatments does not affect the TPV in the same way that they affect EPDM, so they also have not been successful in modifying the TPV surface. If primers are used to pre-treat the TPV surface, they need to be cured or dried, which will require a source of drying or a longer zone to allow air drying. Another issue that needs to be considered when flocking TPV is that, unlike cured EPDM, if the TPV is taken above its softening point, the profile will deform. This limits the profile temperature to a maximum temperature of 116-138 [degrees]C. These temperatures are much lower than where a typical EPDM flock adhesive is cured. So, if an EPDM flock adhesive is dropped into a TPV application, the adhesive will have to be highly catalyzed, which may cause the adhesive to have a much shorter pot life and shorter brush life. Another approach to achieve adequate cure is to increase the oven length. After reviewing the above issues for flocking TPV extrusions, it could be concluded that the change would be more costly. But in fact, even with the changes needed to prepare the TPV surface for flocking, there are still significant cost savings in capital equipment, and possibly some cost savings in materials. The cost savings in materials comes from the ability to co-extrude TPV lips to a PP core, instead of using a metal core which is used in a number of weatherstrip profiles. This change allows the parts to be lighter, but still have the rigidity rigidity /ri·gid·i·ty/ (ri-jid´i-te) inflexibility or stiffness. clasp-knife rigidity of a part with a metal core. Targeted performance criteria for the new flock adhesive When looking at the process that is required to use TPV, there is one key change that allows the development of an aqueous adhesive system. In the EPDM processing, even in a split line process, the typical part temperatures are greater than 66 [degrees]C. At these temperatures, the water in an aqueous flock adhesive would evaporate e·vap·o·rate v. 1. To convert or change into a vapor; volatilize. 2. To produce vapor. 3. To draw or pass off in the form of vapor. 4. before the flock fibers could be imbedded imbedded, adj See embedded. into the adhesive film, resulting in poor (or no) flock coverage on the extrusion. However, on the TPV extrusion line, the substrate needs to be cooled to below the softening point of the TPV. This change results in substrate temperatures that are consistently below 38 [degrees]C, allowing the aqueous adhesive to remain liquid long enough for the flock fibers to be imbedded into the adhesive film. At this point, the desired characteristics of the new adhesive need to be specified. The following items were considered "must haves" for the adhesives to meet the rigorous application and performance requirements of the automotive weatherstrip market: * The adhesive system must be aqueous in order to comply with more stringent EPA EPA eicosapentaenoic acid. EPA abbr. eicosapentaenoic acid EPA, n.pr See acid, eicosapentaenoic. EPA, n. requirements. * The adhesive must cure at temperatures below the softening point of the TPV (<140 [degrees]C). * The cure time must be within typical cure times seen on EPDM extrusion lines (90-180 seconds). * The adhesive needs to be able to be applied using the techniques currently in use at automotive weather strip manufacturers. * The adhesive needs to meet adhesion requirements of the OEMs (> 10 N/cm). * The adhesive needs to display acceptable wear/abrasion characteristics. Because we were not certain of how this adhesive would perform on TPV, we also targeted a list of desirable properties that would make the adhesive more user-friendly to the weatherstrip manufacturers. This included: * Meet all of the current EPDM specifications; * be a single component adhesive; * require no primer or pre-treatment; * be able to adhere to EPDM rubber; and * have a wide cure time/temperature window. Upon reviewing the required performance criteria of the OEMs, certain tests were selected as the key tests to meet, including: * Chrysler peel strength test-1.0 KN/m or 10 N/cm; * Ford crock crock - [American scatologism "crock of shit"] 1. An awkward feature or programming technique that ought to be made cleaner. For example, using small integers to represent error codes without the program interpreting them to the user (as in, for example, Unix "make(1)", which test-1,000 soap and water cycles; and * Chrysler environmental testing-water immersion immersion /im·mer·sion/ (i-mer´zhun) 1. the plunging of a body into a liquid. 2. the use of the microscope with the object and object glass both covered with a liquid. , heat exposure and cycle test. Performance of MorFlock F-450/F-453 system The peel test consists of using a hot melt or an epoxy epoxy Any of a class of thermosetting polymers, polyethers built up from monomers with an ether group that takes the form of a three-membered epoxide ring. The familiar two-part epoxy adhesives consist of a resin with epoxide rings at the ends of its molecules and a curing to affix affix v. 1) to attach something to real estate in a permanent way, including planting trees and shrubs, constructing a building, or adding to existing improvements. the flock fibers, then peeling the TPV substrate away from the hot melt at an angle of 180 [degrees]. The following figure and tables represent peel results based upon coating weight (figure 4), various oven temperatures and residence times (table 1). As can be seen in figure 4, peel strength is not very sensitive to the wet film thickness (WFT WFT Weatherford International (stock symbol) WFT Waterfront (real estate) WFT World Family Tree (genealogy) WFT Wet Film Thickness ). Another area of critical importance for producing automotive weatherstrip extrusion is the manufacturing operating window at which acceptable performance can be achieved. As you can see from the table 1 peel strength results, there is a broad window to achieve acceptable performance (>10 N/cm). Since the F-450/F-453 system is waterborne and being used to keep the elements out, water sensitivity is another critical physical property that needs to be evaluated. The test that we used for this evaluation was water immersion at 35 [degree]C for 48 hours. As can be seen, the peel strength was reduced slightly (table 2), but the performance was still well above the industry requirements. The next requirement to be evaluated for performance was the abrasion abrasion /abra·sion/ (ah-bra´zhun) 1. a rubbing or scraping off through unusual or abnormal action; see also planing. 2. a rubbed or scraped area on skin or mucous membrane. or wear testing. The Ford crock test was chosen because it is one of the most severe. The Ford crock test consists of a 1,000 gram weight being applied to the abrasion surface that consists of a finger that is covered with a specific grade of cloth. The finger is then rubbed across the flocked surface for one thousand cycles. In addition to abrasion, the test calls for various fluids to be applied to the test specimen throughout the test to evaluate chemical resistance. The two fluids that are the most difficult to pass for EPDM extrusions are naphtha naphtha (năp`thə, năf`–), term usually restricted to a class of colorless, volatile, flammable liquid hydrocarbon mixtures. and a soap and water solution. When these fluids were tested on specimens of various wet film thickness (WFT), the results showed that the naphtha did not adversely affect the crock performance at any film thickness (figure 5). The soap and water solution proved to be more difficult to pass. A 225 micron micron: see micrometer. One micrometer, which is one millionth of a meter or approximately 1/25,000 of an inch. The tiny elements that make up a transistor on a chip are measured in micrometers and nanometers. See process technology. WFT was needed to impart acceptable performance in this test. When crock performance was evaluated at various time and temperature cure conditions, it became evident that, in order to pass the crock test, cure conditions become more critical. In order to pass the 1,000 cycles specified in the Ford crock test, higher temperatures or longer oven dwell times are required (table 3). When crock testing was performed on samples that were immersed im·merse tr.v. im·mersed, im·mers·ing, im·mers·es 1. To cover completely in a liquid; submerge. 2. To baptize by submerging in water. 3. in 38 [degrees]C water for 48 hours (table 4), an interesting phenomenon was observed. The oven cure time and temperature ranges that were required broadened dramatically, with time reductions of greater than 25%, depending on the oven setting. The improved results from the 38 [degrees]C water immersion test indicate that the F-450/F-453 system continues to cure when exposed to additional elevated thermal exposure The total normal component of thermal radiation striking a given surface throughout the course of a detonation; expressed in calories per square centimeter or megajoules per square meter. , imparting im·part tr.v. im·part·ed, im·part·ing, im·parts 1. To grant a share of; bestow: impart a subtle flavor; impart some advice. 2. more wear resistance. Because of these results, testing was done to see how the F-450/F-453 system would perform when exposed to a short high efficiency oven to set the adhesive and the flock fibers, followed by a secondary cure using a low efficiency oven to finish the cure to simulate a batch cure process. The results from this testing (table 5) show that the F450/F-453 system is capable of achieving acceptable peel strength (>10 N/cm), even without a secondary cure. However, to achieve passing the Ford crock test, additional cure was required. These results indicate that the F-450/F-453 system is capable of being used in a two-stage process where the parts could be accumulated and then put into a low temperature oven for a longer time, so the parts never reach the TPV's softening point temperature. The next area that was evaluated was the Chrysler environmental test. As can be seen in table 6, the F-450/F-453 system was able to meet the requirements of the Chrysler environmental exposures with no significant reduction in peel strength performance. Also, when the test pieces were tested against the Ford crock test, they passed the soap and water exposure after 1,000 cycles. It should be noted that typically the Ford crock testing does not specify any exposure test before performing the crock cycles. The last characteristic of the F450/F-453 system worth discussing is the adhesive system's volatile organic content (VOC (Vertical Online Community) See vertical portal. ). While a waterborne adhesive does not require the use of solvents as the principal carrier, it does require some solvents to allow the adhesive to coalesce co·a·lesce intr.v. co·a·lesced, co·a·lesc·ing, co·a·lesc·es 1. To grow together; fuse. 2. To come together so as to form one whole; unite: and form a continuous film. These solvents are called cosolvents. For a typical solvent-based flock adhesive, the VOCs can run from 3.2-4.1 lbs. of VOC/gallon of adhesive. The VOC in the F-450/F-453 system is 0.85 lbs. VOC/gallon of adhesive, which is a significant reduction in VOC of almost 400%. Conclusion An adhesive system has been developed that bonds to the targeted substrates without the need for primers or other surface treatments typically needed to flock a TPV extrusion material. This eliminates an additional process step. The adhesive system is able to pass the targeted OEM (Original Equipment Manufacturer) The rebranding of equipment and selling it. The term initially referred to the company that made the products (the "original" manufacturer), but eventually became widely used to refer to the organization that buys the products and requirements for EPDM while being tested on TPV. The tests that the F-450/F-453 system passed include the Ford crock test (using both naphtha and a soap & water solution to expose the flock areas during the crock testing), as well as the Chrysler environmental tests Environmental tests are used to verify a piece of equipment can withstand the rigors of harsh environments, for example:
In addition to performance testing Performance Testing covers a broad range of engineering or functional evaluations where a material, product, or system is not specified by detailed material or component specifications: Rather, emphasis is on the final measurable performance characteristics. , the adhesive system has a broad operation window. This will accommodate both a continuous operation, as seen on a typical EPDM extrusion line, as well as a two-stage process that could be used to accommodate the need for reduced cure temperature required by the TPV substrates. This adhesive system has also passed other fluid exposures and abrasion tests used by car manufacturers other than Ford, Chrysler and GM. James P. Weir, Rohm and Haas Rohm and Haas Company (NYSE: ROH), a Philadelphia, Pennsylvania based company, manufactures miscellaneous materials. A Fortune 500 Company, Rohm and Haas employs more than 17,000 people in 27 countries. The annual sales revenue of Rohm and Haas stands at about USD 8.2 billion.
Table 1--peel values at various cure conditions
Oven Residence Residence Residence
temperature time time time
([degrees]C) 1 min. 1.5 min. 2 min.
177[degrees]C 14.0 N/cm 20.5 N/cm 17.5 N/cm
163[degrees]C 11.1 N/cm 16.8 N/cm 19.3 N/cm
149[degrees]C 8.0 N/cm 12.3 N/cm 12.3 N/cm
135[degrees]C (sa) 11.1 N/cm 14.9 N/cm
Oven Residence Residence Residence
temperature time time time
([degrees]C) 2.5 min. 3 min. 3.5 min.
177[degrees]C 18.1 N/cm (sa) (sa)
163[degrees]C 19.1 N/cm 20.5 N/cm (sa)
149[degrees]C 14.0 N/cm 13.5 N/cm (sa)
135[degrees]C 16.7 N/cm 15.8 N/cm 18.8 N/cm
(sa) = (Shaded areas not tested)
Table 2--peel values after water immersion (48 hours at 35[degrees]C
Residence Residence Residence
Oven time time time
temperature 1 min. 1.5 min. 2 min.
177[degrees]C 16.0 N/cm 21.0 N/cm 16.7 N/cm
163[degrees]C 13.5 N/cm 18.9 N/cm 21.8 N/cm
149[degrees]C 6.7 N/cm 11.2 N/cm 14.7 N/cm
135[degrees]C (sa) 12.1 N/cm 17.2 N/cm
Residence Residence Residence
Oven time time time
temperature 2.5 min. 3 min. 3.5 min.
177[degrees]C 15.8 N/cm (sa) (sa)
163[degrees]C 16.3 N/cm 17.4 N/cm (sa)
149[degrees]C 13.5 N/cm 12.6 N/cm (sa)
135[degrees]C 17.4 N/cm 16.3 N/cm 17.2 N/cm
(sa) = (Shaded areas not tested)
Table 3--Ford crock cycles--with soap and water solution
Oven Residence Residence Residence
temperature time time time
([degrees]C) 1 min. 1.5 min. 2 min.
177[degrees]C 225 585 1,000
163[degrees]C 180 280 1,000
149[degrees]C 135 240 280
135[degrees]C (sa) 165 190
Oven Residence Residence Residence
temperature time time time
([degrees]C) 2.5 min. 3 min. 3.5 min.
177[degrees]C 1,000 (sa) (sa)
163[degrees]C 1,000 1,000 (sa)
149[degrees]C 1,000 1,000 (sa)
135[degrees]C 460 890 1,000
(sa) = (Shaded areas not tested)
Table 4--Ford crock cycles--with soap and water solution after
38[degrees]C water immersion
Residence Residence Residence
Oven time time time
temperature 1 min. 1.5 min. 2 min.
177[degrees]C 750 1,000 1,000
163[degrees]C 280 890 1,000
149[degrees]C 295 429 1,000
135[degrees]C (sa) 380 190
Oven Residence Residence Residence
temperature time time time
([degrees]C) 2.5 min. 3 min. 3.5 min.
177[degrees]C 1,000 (sa) (sa)
163[degrees]C 1,000 1,000 (sa)
149[degrees]C 1,000 1,000 (sa)
135[degrees]C 1,000 1,000 1,000
(sa) = (Shaded areas not tested)
Table 5--evaluation of dual oven cure performance
Time Cool Secondary
Primary in down oven
oven PST * oven time temperature
182[degrees]C 121[degrees]C 30" 5' Control
121[degrees]C
126[degrees]C
132[degrees]C
168[degrees]C 126[degrees]C 30" 5' Control
121[degrees]C
126[degrees]C
132[degrees]C
193[degrees]C 132[degrees]C 30" 5' Control
121[degrees]C
126[degrees]C
132[degrees]C
Time in Peel
Primary second strength S& IN
oven oven (N/cm) Crocks
182[degrees]C - 11 50
4'30" 17 385
" 16 620
" 14 1,000
168[degrees]C - 12 100
4'30" 20 490
" 15 570
" 19 1,000
193[degrees]C - 11 130
4'30" 14 420
" 16 590
" 14 1,000
* PST is peak surface temperature that the part reached during the
initial oven cure.
Table 6--Chrysler environmental testing
Ford crock
180 degree Standard test soap
Test peel requirements and water after
conditions (N/cm) (N/cm) exposure (cycles)
24 hrs. @ R.T. 24.3 10.0 1,000
24 hrs. @ 70[degrees]C 24.2 7.0 1,000
(water immersion)
8 hrs. @ 125[degrees]C 19.3 7.0 1,000
(heat age)
4 days @ 80[degrees]C 23.8 7.0 1,000
(water immersion)
7 days @ 82[degrees]C 20.3 7.0 1,000
(heat age)
|
|
||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion