Selective self-adhesive silicone for LIMS.Liquid injection molded silicone rubber Noun 1. silicone rubber - made from silicone elastomers; retains flexibility resilience and tensile strength over a wide temperature range synthetic rubber, rubber - any of various synthetic elastic materials whose properties resemble natural rubber is widely used because of its excellent performance. It requires fewer labor-costing steps, molding cycles are shorter and there is less potential for contamination. Besides that, it can be easily applied to insert molding with thermoplastics since the materials are cured through addition reactions, which proceed at lower temperatures compared with 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 silicones. It does not need a post-cure treatment because there are no reaction by-products. However, a priming process is necessary for insert molding in order to obtain adhesion between rubber and thermoplastics. This often causes adhesion problems due to uneven coating, incomplete drying, unclear life of primer, etc. The priming process itself is also time-consuming. In this article, a selective sell-adhesive 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. was developed to solve the problem by allowing the liquid 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. material to bond to the 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. insert but not to the metal surface of the mold. Adhesion takes place even after a very short curing time In the annealing procedure could be divided into 3 stages:heating to a particular temperature, keeping for a period of time and cooling to room temperature. The curing time is the hold time of the 2nd stage. so that a selective self adhesive silicone can be used in primerless insert molding or co-injection molding to make a firmly integrated composite with thermoplastics. Moreover, the composite made by this primerless insert molding shows outstanding adhesion durability in various kinds of severe conditions such as high temperature (120[degrees]C), high humidity (85[degrees]C/85%RH), heat cycle (-40[degrees]C6 [equivalence] 120 [degrees]C) and so on. Even after 300 hour's under the above conditions, more than 90% cohesive cohesive, n the capability to cohere or stick together to form a mass. failures within rubber are observed. Materials and methods Materials All selective self-adhesive silicone rubbers tested in this study were prepared by Shin-Etsu and their properties are shown in table 1. Thermoplastics used for the adhesive evaluation were commercial test pieces of polycarbonate A category of plastic materials used to make a myriad of products, including CDs and CD-ROMs. (PC), polybutyleneterephthalate (PBT PBT Provider Backbone Transport (networking technology adding determinism to ethernet) PBT Polybutylene Terephthalate PBT Profit Before Tax PBT Paper Based Test (education) ), polyphenylene oxide (PPO PPO abbr. preferred provider organization PPO Managed care Preferred provider organization, see there Infectious disease Pleuropneumonia-like organism, see there ), 6,6-nylon (PA66), 6-nylon (PA6) and polyphthalamide (PPA PPA 1. Palpation, Percussion & Ausculation 2. Pittsburgh pneumonia agent 3. Postpartum amenorrhea 4. Price per accession 5. Pure pulmonary atresia ): commercial test pieces of metals were made of chromium-galvanized iron, stainless steel stainless steel: see steel. stainless steel Any of a family of alloy steels usually containing 10–30% chromium. The presence of chromium, together with low carbon content, gives remarkable resistance to corrosion and heat. (SUS See Single UNIX Specification. ) and aluminum (A1). Adhesive strength Test samples for the adhesive strength were molded by using insert molding. To begin with, test pieces of thermoplastics and metals were degreased with ethanol, followed by silicone injection between plastic sheets. The mold conditions and methods are shown in figure 1. Two test pieces were inserted in the mold. The mold temperature for the standard grade was 120[degrees]C and for polyamide polyamide material used in the creation of nonabsorbable, synthetic, nylon sutures. was 165[degrees]C. After setting test pieces, a silicone sample was injected in·ject·ed adj. 1. Of or relating to a substance introduced into the body. 2. Of or relating to a blood vessel that is visibly distended with blood. injected 1. introduced by injection. 2. congested. and cured. Cured silicone rubber with lest pieces was taken out from the mold. [FIGURE 1 OMITTED] Adhesive strength between the silicone rubber and the thermoplastics and metals was evaluated by using the 180[degrees] peel adhesion test specified in JIS JIS Japanese Industrial Standard JIS Jamaica Information Service JIS Juggling Information Service JIS Just in Sequence (automotive industry) JIS Jakarta International School JIS Joint Information System K6249. The test consisted of exposing a cross sectional sec·tion·al adj. 1. Of, relating to, or characteristic of a particular district. 2. Composed of or divided into component sections. n. area measuring 25 mm x 10 mm to measure breaking point of three and cohesive failure rate in the rubber by appearance. Results and discussion Selective self-adhesive materials are listed and their physical properties are shown in table 1. There are two grades. One is a standard grade. The other is for a polyamide adhesion grade. X-34-1625A/B A/B Airborne A/B Afterburner (jet engines) A/B Air Blast A/B Answerback A/B Auto-brake A/B Air Bus A/B Afterburning was designed to bind with the polyamide. The adhesion strength data for selective self-adhesive material with various kinds of materials are shown in figure 2. These bars show shear strength For the shear strength of soil, see . Shear strength in engineering is a term used to describe the strength of a material or component against the type of yield or structural failure where the material or component fails in shear. , and the line shows cohesive failure rate. In this graph, a 100% cohesive failure sample is shown. In these data, X-34-1547A/B has strong adhesion with polycarbonate, polybutyleneterephthalate and polyphenylene oxide. On the other hand, it does not show any adhesion with the metals. This 0% CF (cohesive failure) means it was peeled off at the interface. [FIGURE 2 OMITTED] Usually, composites of silicone and engineering plastics are exposed to severe environments. Therefore, we examined adhesion durability as shown in figure 3. It shows the data from tests conducted on samples with polycarbonate inserts aged at high temperature and high humidity. In both conditions, very high bond strengths are exhibited even after 300 hours. Adhesion with primer occasionally breaks in high humidity conditions, but, as can be seen, our self-adhesive material is able to keep its initial strong adhesion. [FIGURE 3 OMITTED] Table 1 shows the line-ups of selective self-adhesive materials, from 40 duro. to 70 duro. You can see these tensile strength tensile strength Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its data are much higher than those of typical silicone room temperature vulcanization vulcanization (vŭl'kənəzā`shən), treatment of rubber to give it certain qualities, e.g., strength, elasticity, and resistance to solvents, and to render it impervious to moderate heat and cold. (RTV RTV Room Temperature Vulcanizing (elastomer sealant) RTV Radio Television (educational major) RTV ReplayTV (digital video recorder brand) RTV Real-Time Video RTV Return To Vendor ) adhesives, almost equal to standard millable high consistency rubber (HCR HCR High Commissioner for Refugees (UN) HCR Home Condition Report HCR Health Care Reform HCR Highway Contract Route (US Postal Service) HCR High Consistency Rubber HCR Human Cognitive Reliability ). So one can easily imagine how strong adhesion is when data shows 100% cohesive failure. Since, as the rubber hardness becomes higher, the interracial in·ter·ra·cial adj. Relating to, involving, or representing different races: interracial fellowship; an interracial neighborhood. stress between rubber and plastic becomes greater, it is not so easy to obtain good adhesion with high hardness rubber. Adhesion property data of X 34-1625A/B with 6,6-nylon, 6-nylon, polyphtalamide and chromiunm plated metals are shown in figure 4. These bars show very strong adhesion with major commercial types of polyamides. At the same time, it does not show any adhesion with chromium chromium (krō`mēəm) [Gr.,=color], metallic chemical element; symbol Cr; at. no. 24; at. wt. 51.996; m.p. about 1,857°C;; b.p. 2,672°C;; sp. gr. about 7.2 at 20°C;; valence +2, +3, +6. plated metal. Of course, the cohesive failure value indicates a clear difference between polyamides and metals. [FIGURE 4 OMITTED] Figure 5 shows adhesion durability data with 6,6-nylon. Figure 6 shows the data with 6 nylon at heat aging (120[degrees]C), low temperature aging (-35[degrees]C), high humidity resistance (85[degrees]C/85%RH) and temperature cycling (-40[degrees]C to 120[degrees]C). This material also keeps excellent adhesion even after 300 hours in those severe environments. This temperature cycle is also a severe test method owing to owing to prep. Because of; on account of: I couldn't attend, owing to illness. owing to prep → debido a, por causa de repeated interfacial stress caused by the thermal expansion thermal expansion Increase in volume of a material as its temperature is increased, usually expressed as a fractional change in dimensions per unit temperature change. rate difference between rubber and plastics. As can be seen, initial strength does not change during 300 hundred cycles of one hour each from below -40[degrees]C to 120[degrees]C. [FIGURES 5-6 OMITTED] The mechanism of selective adhesion is shown in figure 7. Silane silane or silicon hydride Any of a series of inorganic compounds of silicon and hydrogen with covalent bonds and the general chemical formula SinH(2n + 2). coupling agents were not used as adhesion promoters because they show stronger adhesion with inorganic inorganic /in·or·gan·ic/ (in?or-gan´ik) 1. having no organs. 2. not of organic origin. in·or·gan·ic n. 1. materials such as metal mold surfaces than with most of thermoplastics. So, instead of silane coupling agents, we use some other chemicals, which do not have either silyl alkoxy or silanol groups, as adhesion promoters. The important point is the interaction between rubber and plastics that results from the chemical bond or interracial miscibility miscibility (miˈ·s  ·biˑ·l between two layers. Of course, the
bonding agent should have a group reactive with silicone rubber,
otherwise it will only migrate to the thermoplastic when it comes into
contact with it.[FIGURE 7 OMITTED] Figure 8 shows the data of co-injection or two-shot injection molding. At first, melted polyamide is injected vertically into this cavity with both sides of the mold at a temperature of 120[degrees]C. Then the left mold is rotated rotated turned around; pivoted. rotated tibia see rotated tibia. , followed by silicone injection at the right mold at 120[degrees]C. The silicone side of the mold is heated at 130[degrees]C to 168[degrees]C. The sample shape is shown. It is a round coaster What a bad CD-R disc is often called. See CD-R and underrun. about 8 cm in diameter. [FIGURE 8 OMITTED] Adhesion results are shown figure 9. We cannot measure shear strength on the coaster shape, so we made a graph from 1-5 to indicate adhesion level. Five means excellent adhesion (100% cohesive failure). One means no adhesion. In figure 10, we changed mold temperature of injection side from 130[degrees]C to 168[degrees]C. One can see at the higher temperatures we can get better adhesion. At over 160[degrees]C, we can get 100% cohesive failure. In this figure we changed the molding time, between mold close and mold open, from 15 seconds to 60 seconds while the mold temperature was fixed at 168[degrees]C. The results are clear. Even after just 15 seconds, we can obtain enough adhesion level. [FIGURES 9-10 OMITTED] Even among the same thermoplastics shown in this study, some grades, because of their method of polymerization polymerization Any process in which monomers combine chemically to produce a polymer. The monomer molecules—which in the polymer usually number from at least 100 to many thousands—may or may not all be the same. , degree of refining and types of additives, are not suited to the addition reactions of silicone rubber or cannot sufficiently exhibit adhesion. These need to be checked on an individual basis. Data of shearing adhesion strength tests were obtained on standard materials for engineering plastics and a new material especially designed for polyamides. The results of shearing strength (MPa) are shown in table 2. In this table, different hardnesses of standard materials shows the same level of shearing adhesion strength with PC. PBT and PPO. Also, shearing strength with the metals is at a low level. From these data, a selective self-adhesive silicone enables a process engineer to take advantage of productivity and reliability in making a composite of silicone rubber with a thermoplastic by eliminating the priming process. Moreover, the composite made by this primerless insert molding shows outstanding adhesion durability in various kinds of severe conditions such as high temperature (120[degrees]C), high humidity (85[degrees]C/85%RH), heat cycle (-40[degrees]C+[equivalence]120[degrees]C) and so on. Even after 300 hours at the above conditions, more than 90% cohesive failures within rubber am observed. Conclusion Selective self-adhesive silicone was developed as the liquid injection molding material to bond to the thermoplastic insert but not to the metal surface of the mold. Adhesion takes place even after very short curing time so that it can be used in primerless insert molding or co-injection molding to make a firmly integrated composite with thermoplastics. Table 1--list of selective self-adhesive silicone rubbers Material Standard Nominal durometer, A 40 50 Formulation\identification no. X-34-1277 A/B X-34-1547 A/B Dimethylpolysiloxane (*1) 100 100 Fumed silica (*2) 33 38 Crosslinker (*3) 2.0 3.8 Platinum catalyst 0.3 0.3 Curing inhibitor (*4) 0.1 0.1 Adhesive promoter-1 (*5) 1.4 1.4 Adhesive promoter-2 (*5) Properties Viscosity (A) Pa.s 400 340 Viscosity (13) Pa.s 700 800 Cure speed (*6) T10 sec. 82 66 T90 sec. 105 102 Specific gravity 1.11 1.12 Hardness duro. A (*7) 40 52 Elongation % 630 420 Tensile strength, MPa 9.0 8.3 Material Standard Nominal durometer, A 60 70 Formulation\identification no. X-34-1427 A/B X-34-1534 A/B Dimethylpolysiloxane (*1) 100 100 Fumed silica (*2) 36 36 Crosslinker (*3) 5.7 7.2 Platinum catalyst 0.3 0.3 Curing inhibitor (*4) 0.1 0.1 Adhesive promoter-1 (*5) 1.4 1.4 Adhesive promoter-2 (*5) Properties Viscosity (A) Pa.s 450 600 Viscosity (13) Pa.s 700 600 Cure speed (*6) T10 sec. 94 69 T90 sec. 154 98 Specific gravity 1.12 1.13 Hardness duro. A (*7) 60 68 Elongation % 240 230 Tensile strength, MPa 7.3 7.7 Material For polyamide Nominal durometer, A 50 Formulation\identification no. X-34-1625 A/B Dimethylpolysiloxane (*1) 100 Fumed silica (*2) 28 Crosslinker (*3) 4.0 Platinum catalyst 0.3 Curing inhibitor (*4) 0.1 Adhesive promoter-1 (*5) 2.0 Adhesive promoter-2 (*5) Properties Viscosity (A) Pa.s 800 Viscosity (13) Pa.s 850 Cure speed (*6) T10 sec. 30 T90 sec. 55 Specific gravity 1.09 Hardness duro. A (*7) 49 Elongation % 450 Tensile strength, MPa 7.5 (*1)--dimethylpolysiloxane having both molecular terminals capped dimethylvinylsiloxy groups; (*2)--surface-treated with hexamethyldisilazane and having BET method specific surface area of 300 [m.sup.2]/g; (*3)--copolymer of dimethylsiloxane (50 mol %) and methylhydrogensiloxane (50 mol %) having both molecular terminals capped trimethylsiloxy groups, (*4)--3.5-dimethyl-1-hexyn-3-ol; (*5)--ODR: proprietary product; (*6)--ODR: 120[degrees]C (X-34-1625A/B: 150[degrees]C); (*7)--cure condition: 120[degrees]C/ 10min press cure Table 2--the results of shearing strength of selective self-adhesive silicone rubbers Material Standard Nominal durometer, A 40 50 \identification no. X-34-1277 A/B X-34-1547 A/B Injection pressure, kgf/cm2 200 200 Mold temperature, [degrees]C 120 120 Curing time, min 1.0 1.0 Shearing strength-PC, MPa 4.5 5.9 Shearing strength-PBT, MPa 3.8 4.0 Shearing strength-PPO, MPa 3.6 3.8 Shearing strength-Cr, MPa 0.4 0.7 Shearing strength-SUS, MPa 0.7 0.9 Shearing strength-AI, MPa 0.8 0.7 Shearing strength-PA66, MPa -- -- Shearing strength-PA6, MPa -- -- Shearing strength-PPA, MPa -- -- Material Standard Nominal durometer, A 60 70 \identification no. X-34-1427 A/B X-34-1534 A/B Injection pressure, kgf/cm2 200 200 Mold temperature, [degrees]C 120 120 Curing time, min 1.0 1.0 Shearing strength-PC, MPa 4.7 4.6 Shearing strength-PBT, MPa 4.1 3.7 Shearing strength-PPO, MPa 3.8 3.7 Shearing strength-Cr, MPa 0.6 0.2 Shearing strength-SUS, MPa 0.6 0.3 Shearing strength-AI, MPa 0.9 0.5 Shearing strength-PA66, MPa -- -- Shearing strength-PA6, MPa -- -- Shearing strength-PPA, MPa -- -- Material For polyamide Nominal durometer, A 50 \identification no. X-34-1625 A/B Injection pressure, kgf/cm2 200 Mold temperature, [degrees]C 165 Curing time, min 1.0 Shearing strength-PC, MPa 4.5 Shearing strength-PBT, MPa 4.0 Shearing strength-PPO, MPa -- Shearing strength-Cr, MPa 0.9 Shearing strength-SUS, MPa -- Shearing strength-AI, MPa -- Shearing strength-PA66, MPa 4.1 Shearing strength-PA6, MPa 4.6 Shearing strength-PPA, MPa 3.9 Acknowledgements "Selective self-adhesive silicone for LIMS LIMS Laboratory Information Management System LIMS Library Information Management System LIMS Limb Infrared Monitor of the Stratosphere LIMS Land Information Management System (Canada) LIMS Logistics Information Management System " is based on a paper given at the October, 2001 Rubber Division meeting. "Factors affecting silicone volatile levels in fabricated fab·ri·cate tr.v. fab·ri·cat·ed, fab·ri·cat·ing, fab·ri·cates 1. To make; create. 2. To construct by combining or assembling diverse, typically standardized parts: silicone elastomers" is based on a paper given at the September, 1999 Rubber Division meeting. |
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