Islam, Aminul

Jessen, Rikke L.

Ruby, Tobias M.

This project was carried out in co-operation with the company Sonion. Sonion specializes in manufacturing miniature components mainly for use in hearing aids or medical instruments. Recently Sonion has developed a hearing that calls for the need of a miniature sealing ring to protect the electronics inside from environmental hazards. The sealing ring is injection moulded in Santoprene-a thermoplastic vulcanizate consisting of Polypropelene and highly vulcanized EPDM rubber. The scope of the project was therefore to investigate the properties of Santoprene and make an immediate evaluation of whether Santoprene is appropriate for use under the conditions, to which it will be subjected being part of a hearing aid used on daily basis. The conditions tested are: sweat, acid corrosion, extreme temperatures. An evaluation of the maximum load before breakage in relation to manufacturing conditions has also been performed

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Downloaded from orbit.dtu.dk on: Dec 17, 2017Effects of moulding and environmental conditions on the mechanical and surfaceproperties of injection moulded santoprene rubberIslam, Aminul; Ruby, Tobias M.; Jessen, Rikke L.Publication date:2010Link back to DTU OrbitCitation (APA):Islam, A., Ruby, T. M., & Jessen, R. L. (2010). Effects of moulding and environmental conditions on themechanical and surface properties of injection moulded santoprene rubber. Poster session presented atPolymers in Process and Products, Lyngby, DTU, .Effects of moulding and environmental conditions on the mechanical and surface properties of injection moulded Santoprene rubberTobias Møller Ruby - s061992 Rikke Lichinger Jessen - s061995IntroductionResultsConclusionSources of errorsAcknowledgementsReferencesExperimental plan28811 Polymers in Processes and Products - DTU MEK and Danish Polymer Center, 3. Week period DTU 2010Advisor Aminul Islam - Course responsible Søren Hvilsted and Hans Nørgaard HansenThis project was carried out in cooperation with the company, Sonion. Sonion specializes in manufacturing miniature components mainly for use in hearing aids or medical instruments. Recently Sonion has devel-oped a hearing aid that calls for the need of a miniature sealing ring to protect the electronics inside from environmental hazards (Image 1 & 2). The sealing ring is injection moulded in Santoprene – a thermoplas-tic vulcanizate consisting of Polypropylene and highly vulcanized EPDM rubber (Ref 5). The scope of the project was therefore to investi-gate the properties of Santoprene and make an immediate evaluation of whether Santoprene is appropriate for use under the conditions, to which it will be subjected being a part of a hearing aid used on a daily basis. A number of sample specimens simulating the sealing ring were injec-tion moulded and needed to base the investigation of Santoprene upon. Changing dierent parameters from one specimen to another during the moulding process enabled a later determination of the in-uence of the manufacturing conditions on the mechanical character-istics of the specimen. The parameters that were changed from sample to sample was the followingEither a high mold temperature (50°) or a low mold temperature (32°)Either a high material mass temperature (300°) or a low material mass temperature (260°)Either a high injection speed (400 mm/s) or a low injection speed (200mm/s) (Ref 3 & 4)By combining each of these six parameter settings a total of eight dif-ferent specimens were molded. Each specimen was made in a batch of four, so later testing of the samples is not based on a single specimen but calculating the average of four is allowed. Additionally 21 sample specimens with the optimal settings of the described manufacturing parameters according to the producers of Santoprene were made. The manufacturing conditions of the nine dierent specimens are listed in Table 1.The optimal sample specimens were subjected to dierent environ-mental conditions the sealing ring might have to be able to withstand when used in a hearing aid to test if the strength of Santoprene is af-fected by these.  SweatWhen used in a hearing aid the sealing ring will be regularly be sub-jected to human sweat. To test whether human sweat had a negative eect on Santoprene, a chemical solution was created to simulate sweat and the specimens were placed in the solution for 24 hours before the strength was tested (Ref 1).CorrosionFive optimal specimens were also placed in an corrosive acid solution for 24 hours consisting of 10% H2SO4 and 90% H2O to test the resistance to acids of Santoprene material. Temperature CycleAnother batch of the optimal specimen was also subjected to an ex-treme temperature elevation followed by an extreme temperature low-ering. For 12 hours they were kept at a constant 60° followed by 12 hours at -18°.When weighed, the average mass of the nine dierent specimen types slightly diered, as shown by Chart 1. This is a direct result of the dier-ing moulding conditions and more precisely the Tme.Because of the higher temperature the material will experience more thermal expansion and there will then t less material in the cavity. For analysing a change in mechanical properties because of dierent mould and environmental conditions the following tests and measure-ments have been made. The results are as following.This project will analyse whether dierent moulding or environmental conditions will have an eect on the mechanical properties of the San-toprene rubber material.By tensile testing, in accordance to ISO 37, every specimen it could be determined how specic moulding or environmental conditions inu-ences the tensile strength of Santoprene (Image 6 and 7) (Ref 2). For each specimen type a visual presentation of the load and extension relationship was made. These show how elastomeric properties of the polymer relate to the load and are important in analyzing the mechani-cal properties. An example is Chart 4 which is the presentation on the six optimal specimens tested.  3D Surface ProlometerTo evaluate the quality of the specimens it is important to look at the surface roughness. This is an important parameter for both mechanical and visual properties. The roughness analysis was done with an advanced optical 3D measurement device, which is able to create a 3D representation of any surface area and determine the average roughness in that specic area. Measurements were done on the two extreme, I and VI, and the op-timal sample specimens and the results are presented in Chart 2 To evaluate the surface roughness of the dierent samples two tests were made. Microfocus measurement and Contact angle.below and are averages based on ve measurements. These results are dicult to explaing because there is no knowledge about the mould roughness. The VI looks to have a smoother surface when compared to the I but the dierence is very small and therefore it is impossible to destinguish between them.RoughnessMoulding conditionsTensile strenghtEnvironmental conditionsHardnessMassDuring the execution of this projects a numerous list of either equipment, environmental conditions or human related sources of errors have af-fected the results. To systematically state them all here would be irrelev-ent.When argumenting whether Santoprene is an appropriate material for use in the hearing aid, it is rstly important to realize that this project only is a guideline on the matter.  The results cannot directly be translated to the miniature sealing ring in reality, since the dimensions and mass of the used specimens will have severe signicance. In micro moulding many other parameters are crucial. Other than that many of the mechanical properties of Santoprene are satisfactory in relation to the desired and the material does not seem to be signicantly aected by sweat or corro-sive solutions. The manufactures should though be aware of the eect on the strength, when exposed to radical temperature changes over a longer period of time (Chart 6). The results retrieved from the tensile tests are the average maximum load before break, calculated on basis of four tensile tested specimens. See chart 5 for the moulding scenarios and chart 6 for the environment sce-narios. Specimens moulded at high material mass temperature are generally weaker because of the lesser material mass in the specimen caused by thermal expansion. This is consistent with the tendency in our results considering all the specimens with high material mass temperature (II, III, VI) except one (VII) are the weakest.  In general the eect of high injection speed is a stronger specimen, but in this project both the slow and fast injection speed would normally be re-garded as relatively high. Therefore it is dicult to conclude anything specic from the results regarding injection speed.Comparing the strength of the optimal specimen with the specimens ex-posed to sweat or corrosion nothing can be concluded, since the stand-ard deviations are overlapping. Considering the temperature cycle test a clear deterioration in the strength of the specimen is observed.Throughout this project many people have helped us along. Therefore we would hereby like to thank Sonion for entrusting us with this project. DTU MEK, DTU Chemistry, DTU Management and The Danish Polymer Center for lending us their equipment. Hans Nørgaard Hansen and Søren Hvilsted as our lectors. Aminul Muhammad Islam as our helpful and very capable advisor. Lastly Christian Ravn, Reinholdt Koch, Steen S. Munch and Kim Chi Szabo for helping us with conducting the dierent tests. www.nishing.com/310/79.shtmlUS Fuel Cell Counsil’s Recommended Standard Test Methods for Fuel Cell Gasket Material, Washinton DC, 2006Injection Molding of Santoprene Thermoplastic Vulcanizate B500 SeriesData Sheet on Santoprene 8291-60B500 Themoplastic VulcanizateWalker, Benjamin M et al.: “Handbook of thermoplastic Elastomers”, 2. ed. Van Nostrand Reinhold Company Inc, New York, 1988!"#$!!"$!!#$!%"$!%#$!&"$!&#$!'"$!"#$%&#'(%)*(+(',-%.'/01'I [32 C°,260 C°,200 mm/s]II [50 C°,300 C°,200 mm/s]III [32 C°,300 C°,200 mm/s]IV [50 C°,260 C°,200 mm/s]V [32 C°,260 C°,400 mm/s]VI [50 C°,300 C°,400 mm/s]VII [32 C°,300 C°,400 mm/s]VIII [50 C°,260 C°,400 mm/s]Opt [32 C°,280 C°,300 mm/s]Temperature cycleSweatCorrosionOpt [32 C°,280 C°,300 mm/s]!!!"!!#"!!$"!%&"!%'"!%("!%)"!"#$%&#'(%)*(+(',-%.'/01'!"#$%#$&#$'#$$#(%)#(%*#(%!#!"#$%&#'()*+%,+'%*&-#'./0'I [32 C°,260 C°,200 mm/s]VI [50 C°,300 C°,400 mm/s]Opt [32 C°,280 C°,300 mm/s]Chart 7 - The average maximum load of each moulding scenario. Chart 2 - The average roughness  of the extreme moulding scenarios compared with the optimal.Table 1 - The average weight compared to the melt temperature.Chart 6 - The average maximum load of each environmental scenario.Image 5 - A screenshot of a contact angle measurement.Chart 3 (Right) - The average contact angles of the extreme moulding scenarios compared to optimal.Chart 4 - The average hardness of the extrememoulding scenarios compared to optimal.Image 6 - The tensile test setup. Image 7 - The three gures show how the material behaves during a tensile test.Image 2 - The sealing ring which Sonion wish to mould in Santoprene rubber.Image 1 - The hearing aid in which the sealing ringis placed.Ø 1.25 mmØ 0.2 mmFF1. 2. 3.Chart 5 - Load vs. Extenstion graph of the optimal samples.Specimen [#]Mold Temperature (Tm) [°]Material Mass Temperature (Tme) [°]Material Mass Temperature (Vin) [mm/s]Opt32280300I32260200II50300200III32300200IV50260200V32260400VI50300400VII32300400VIII50260400!"#$%#$&#$!#$'#$"#'%#!"#$%&''()(*+,#&(-(I [32 C°,260 C°,200 mm/s]VI [50 C°,300 C°,400 mm/s]Opt [32 C°,280 C°,300 mm/s]The hardness of specimens was also investigated by conducting hardness tests in accordance with the relevant ISO standards. The test shows the specimen’s ability to withstand compression by an-other object. The results as listed in Chart 4 shows the hardest sample to be the Opt which is the closest to the suppliers 60 Shore A specication. Contact AngleThe surface properties were further analyzed by the Sessile drop tech-nique (Image 5). A known liquid droplet is placed on the tested speci-mens and the resulting contact angle is dened by the surface proper-ties of the material. Generally a larger contact angle occurs with greater roughness. The results as presented in Chart 3 also show us inexplainable results. The reasons for this are the same as for the Microfocus measurement. !"!#!$"!#%"!#%$"!#&"!#&$"! "#$%&'()*++#,-*."'*/012#I [32 C°,260 C°,200 mm/s]VI [50 C°,300 C°,400 mm/s]Opt [32 C°,280 C°,300 mm/s]Chart 1 - The average mass compared to the melt temperature.!"#$%!"#&%!"#'%!"#(%!)%$*"% $'"% $+"% $("% $,"% !""% !)"%!"##$%&'$()*$%+,'$-200204060801001201400 10 20 30 40 50 60 70 80 90 100 110Load (N)Extension (mm)Load [N] vs. Extension [mm]Specimen #1234561.2.3.4.5.

Effects of moulding and environmental conditions on the mechanical and surface properties of injection moulded santoprene rubber

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Effects of moulding and environmental conditions on the mechanical and surface properties of injection moulded santoprene rubber

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