GMNA-9984160-1990.pdf
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1、m 7006379 0000387 350 I GENERAL MOTORS ENGINEERING STANDARDS I Materials and Processes - Paint COATING, SPRAYABLE MASKING 9984160 1 SCOPE. This specification covers the requirements for sprayable coating materials which mask the substrate from subsequent applied coatings. It is generally intended th
2、at portions of the coating will be removed prior to topcoating to provide two-tone or accent effects. For this purpose, the mask coating must trim easily without lifting and have sufficient tensile strength to be removed without tearing. The coating must not harm the substrate or previously applied
3、coatings in any way, and in areas where the coating has been removed, there shall be no affect on the appearance, adhesion or durability of the subsequently applied topcoat. In areas where the masking material is subsequently coated, there shall be no affect on the cure of the topcoat, which would r
4、esult in tackiness or other effects detrimental to the process. These mask coatings are waterborne for reduced solvent emissions. 2 REFERENCED STANDARDS. GM950SP ASTM2697 ASTM D147S ASTM D3960 ASTM 02 196 ASTM D4212 ASTM D2369B ASTM E70 3 REQUIREMENTS. Documentation covering all mate- rial propertie
5、s and performance test results must be supplied in a form acceptable to the General Motors Engineering activity to which submission is made. Any significant change made to the material components or manufacturing process must be assessed to determine if requalification is required. 3.1 Material Requ
6、irements. The following requirements are for the masking material before application and drying: 3.1.1 Identification. All materials must have complete iden- tification by product code and manufactunng batch. All required safety/hygiene information per 5.1 must be fur- nished. Specific parameters re
7、quired are: 3.1.1.1 Physical Constants. Mass (ASTM D2369) and vol- ume (ASTM D2697) percent solids, VOC (ASTM D3960) and density (ASTM D147S). 3.1.1.2 Viscosity. Newtonian materials (ASTM D4212). For non-Newtcnian matenals use Brookfield (ASTM D2196i. or equivalent. 3.1.1.3 pH (ASTM E70). 3.1.1.4 Od
8、or. The matenal s odor shall be reviewed in comparison with current production materials, when evaluat- ed in laboratory and production tnals. Any changes in formulation must be reassessed for effect on odor. 3.1.1 .S Solvent Emissions Compliance. All coating materials must meet specific plant solve
9、nt emissions restrictions. Any change m formulation which affects VOC content or applica- tion tn-insfer efficiency must be evaluated for effect on compliance before production use. 3.2 Performance Requirements. The following requirements apply to the dry masking film, its ability to perform the int
10、ended masking function, and its effect on previous and subsequently applied coatings. Panel should be prepared using the intended substrate and primer(s), if applicable. Spray the masking material to a wet film build sufftcient to yield the specified dry film thickness. Allow to air dry or force dry
11、 per supplier recommendation. Prior to test, cut and remove one half of the masking material from test panel. Qualification of a masking material to these requirements allows its use only in the tested combination of substrate, primer and topcoat. Use in other combinations requires retesting to the
12、applicable performance requirements. 3.2.1 Appearance. The film shall be smooth and uniform, free of voids or other defects detrimental to its masking function. Color shall be per agreed Standard. 3.2.2 Film Thickness (ASTM D1186). Range 75 to 125 pm. All performance and processability requirements
13、must be met within entire film build range. 3.2.3 Adhesion. The coating must have sufficient adhesion to allow cutting and removal of portions of the film without lifting the remaining film. Tensile strength and elongation shall be sufficient to allow easy removal without tearing, both before and af
14、ter topcoating. 3.2.4 Effect On Substrate Prior To Topcoating. The masking material must have no effects on the substrate or prior coatings which impact performance or paintability. After the simulated aging tests below, the film must be cleanly removable from the substrate, leaving no residue or co
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