1、/= - MIL-C-24449A(SH) SUPERSEDING MIL-C-2 4449 (SHIPS) 1 March 1971 (See 6.5) M IL I TA RY S PE C 1-F IC AT ION CAST POLYMETHYL METHACRYLATE FOR . SHEET STOCK, CUSTOM CASTINGS, AND FINISHED WINDOWS This specification is approved for use by the Naval Sea Systems Command, Department of the Navy, and i
2、s available for use by all Departments and Agencies of the Depart-ment of Defense. 1. SCOPE 1.7 Scope, This specification covers polymerized methyl methacry- late sheet stock, custom castings, and windows of optical quality for service in pressure vessels for human occupancy. 2. APPLICABLE DOCUMENTS
3、 2.1 Issues of documents. The following documents, of the issue in effect on date of invitation for bids or request for proposal, form a part of this specification to the extent specified he-rein. requ STANDARD MILITARY MIL-STD-129 - Marking for Shipment and Storage. (Copies of specifications, stand
4、ards, drawings, and publications red by contractors in connection with specific acquisition functions should be obtained from the contracting activity or as directed by the contracting officer.) 2.2 Other publications. The following documents form a part of this specification to the extent specified
5、 herein. Unless otherwise indicated, the issue in effect on date of invitation for bids or request for proposal shall apply. r Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of use in improving this document should be addressed to: Commander, Naval Se
6、a Systems Command-, SEA 3112, Department of the Navy, Washington, DC 20362 by using the self-addressed Standardiza tion Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter. 1 FSG 9330 Provided by IHSNot for ResaleNo reproduction or networking permitted wit
7、hout license from IHS-,-,-. AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) D 256 - Impact Resistance of Plastics and Electrical D 542 - Index of Refraction of Transparent Organic Plastics, D 570 - Water Absorption of Plastics, Test for. D 621 - Deformation of Plastics Under Load, Test for. D 638
8、- Tensile Properties of Plastics, Test for. D 648 - Deflection Temperature of Plastics Under Flexural D 695 - Compressive Properties of Rigid Plastics, Test for. D 696 - Coefficient of Linear Thermal Expansion of Plastics, Test for. D 702 - Cast Methacrylate Plastic Sheets, Rods, Tubes, and Shapes,
9、Specification for. D 732 - Shear Strength of Plastics, Test for. D 785 - Rockwell Hardness of Plastics and Electrical Insulating Materials, Test for, D 790 - Flexural Properties of Plastics and Electrical Insulating Materials, Tests for. D 792 - Specific Gravity and Density of Plastics by Displaceme
10、nt, Tests for. D 1003 - Haze and Luminous Transmittance of Transparent E 308 - Spectrophotometry and Description of Color in CIE 1931 System, Recommended Practice for, Insulating Materials, Test for . Tests for. Load. Plastics, Test for. I (Application for copies should be addressed to the American
11、Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103.) AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) ANSI/ASME PVHO Safety Standard for Pressure Vessels for Human Occupancy, Appendix A-Design of Viewports. (Application for copies should be addressed to the American Society o
12、f Mechanical Engineers, 345 E, 47th Street, New York, NY 10017.) UNIFORM CLASSIFICATION COMMITTEE AGENT Uniform Freight Classification Ratings, Rules and Regulations (Application for copies should be addressed to the Uniform Classifica- tion Committee Agent, Tariff Publication Officer, Room 1106, 22
13、2 South Riverside Plaza, Chicago, IL 60606.) NATIONAL MOTOR FREIGHT TRAFFIC ASSOCIATION, INC. AGENT National Motor Freight Classification (Application for copies shouuld be addressed to the National Motor Freight Traffic Association, Inc. , ATA TRAFFIC Dept., 1616 itPii Street, N.W., Washington, DC
14、20036.) (Technical society and technical association specifications and standards are generally available for reference from libraries. They are also distributed among technical groups and using Federal agencies.) 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license
15、 from IHS-,-,-i MIL-C-24447A 73 9 777770b OLLB705 B 9 Value required I 3. REQUIREMENTS I 3.1 -First article. When specified (see 6.2.11, the contractor shall furnish sample unit(s) for first article inspection and approval (see 4.3 0 - 90 1.19 +0.01 1.49 TO.01 - 92 90 89 87 85 83 and 6.3). 3.2 Mater
16、ial. Material shall be premium quality, heat-rasistant, . optical grade, cast methyl methacrylate, hereinafter referred to as . acrylic. I 1 Must pass readability tests Minimum 3.2.1 Condit.ion. Material supplied shall be in a fully polymerized state and shall be a monolithic homogeneous solid, esse
17、ntially free of monomer (see table I). Cast sheets shall be cast oversize, or include prolingations for machining of test coupons. 3.2.2 -Recovered materials. Material and finished products covered by this specification may be fabricated using materials produced from recovered materials to the exten
18、t practicable without jeopardizing the properties specified in table I. The term “recovered materials“ means materials which have been collected or recovered from solid waste and reprocessed to become a source of raw materials, as opposed to virgin raw materials, None of the above shall be interpret
19、ed to mean that the use of used or rebuilt products is allowed under this specification unless otherwise specifically specified. 3.3 Properties. Physical and mechanical properties shall be as specified in table I. TABLE I. Physical and mechanical properties. I Property Optical uniformity Hardnes.s,
20、Rockwell M Specific gravity Refractive index Luminous transmittance, Inches 0.0 - 0.249 0.250 - 0.499 0,500 - 0.999 1.000 - 1.999 2.000 - 2.999 3.000 - 4,250 Heat distortion temperature 3.6OF/min at 264 lb/in: Thermal expansion at 20 F. Water absorption: 24 hours at 73OF To saturation Tensile streng
21、th I Unit of value - - Minimum, percent O Minimum, F Maximum, in/in/F Maximum, percent Maximum, percent Minimum, lb/in 2 185 33 x O. 25 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-C-ZLIVYSA 33 47777Ob OL1870b T MIL-C=2444gA(SH) TABLE I. mal
22、 and rnechanical_prp_perties. - Continued Property Tensile elongation Mod of elasticity, tension Compressive strength Mod of elasticity, compr e ssi on Flexural strength Shear strength Impact strength Compressive de f ormat ion2 undgr load, 4000 lb/in , 122 F, 24 hours Residual monomer, methyl metha
23、cr y1 at e and ethyl acrylate Ultraviolet (290-330 nm) transmittance (for 0.5 inch thickness) Unit of value Minimum, percent Minimum, lb/in2 2 Minimum, lb/in2 2 Minimum, lb/in2 Minimum, lb/in Minimum, lb/in Minimum, ft lb/in Maximum, percent notch Maximum, percent Maximum, percent Value required 2 4
24、00,000 15,000 400,000 14,000 8 * O00 0.25 1.0 1.6 5 3.3.1 Dimensions. Finished windows shall conform to the dimensions specified on the engineering drawing specified by the contracting activity (see 4.6.2 and 6.2.1). For custom castings or sheet stock* thickness shall be equal to or exceed the thick
25、ness of the window. specified (see 6.2.11, dimensions shall be measured at 73 F + 2 F. 3.3.2 optio_ uniforaand distortion. Sheets, custom castings, and finished windows shall have smooth and parallel optical surfaces. Fine print shall be legible through the material when placed 20 inches away as spe
26、cified in 4.7.6, Unles$ othegwise - 3.3.3 Visual defects (see 4.63. 3.3.3.1 Sheet stock. Sheet stock shall be colorless and free of visible cracks, checks and crazing. Inclusions (any imbedded particle or bubble) shall not exceed 0.125 inch. Total number of inclusions larger than 0.016, but smaller
27、than 0,125 inch shall be less than the limit determined by dividing the volume of the sheet stock in cubic inches by 641. For purposes of inspection, a 2-inch wide border around the edge of the sheet shall not be included in the evaluation of casting quality. 4 Provided by IHSNot for ResaleNo reprod
28、uction or networking permitted without license from IHS-,-,-MIL-C-24447A 73 9777706 0338707 3 W 3.3.3.2 Custom castings. Custom castings shall be colorless and free of visible internal cracks, checks and crazing. Inclusions shall not exceed 0.030 inch. Total number of inclusions larger than 0.016 bu
29、t smaller than 0.030 inch shall be less than the limit determined by dividing the volume of the custom casting in cubic inches by 641. For the purposes of inspection, the surplus material on the casting to be removed during machining of the window shall not be included in the evaluation of casting q
30、uality, free of visible cracks, checks, and crazing. Inclusions and surface scratches are acceptable only if the dimensions, location, density of population, size of population and spacing between adjacent flaws do not .exceed Che limits specified by ANSI/ASME PVHO Safety Standard. 3.3.3.3 Finished
31、windows. Finished windows shall be colorless and 3.3.4 Luminous transmittance. Sheets, custom castings, and win,dows shall have the optical clarity specified in table I (see 4.7.10). 3.3.5 Construction. The completed window shall be constructed of .one piece of custom cast material. 3.3.5.1 If machi
32、ned from a custom casting, pouring and polymerizing of the custom casting shall be done in one pour. 3.3.5.2 The window shall be annealed at least once during the fabrication process. The final mandatory annealing shall take place after the forming, machining, and machine polishing operations have b
33、een completed by the fabricator. The window shall be annealed for 24 hours at 175OF at a cooldown rate not to exceed 5OF/hour, 4. QUALITY ASSURANCE PROVISIONS 4.1 Responsibility. for in,spection. Unless otherwise specified in the contract, the contractor is responsible for the performance of all ins
34、pection requirements as specified herein. Except as otherwise specified in the contract, the contractor may use his own or any other facilities suitable for the performance of the inspection requirements specified herein, unless disapproved by the Government. The Government reserves the right to per
35、form any of the inspections set forth in the specification where suchinspections are deemed necessary to assure supplies and services conform to prescribed requirements. 4.2 Classification of inspection. The inspection requirements specified herein are classified as follows: (a) First article inspec
36、tion (see 4.3). (b) Quality conformance inspection (see 4.4). 4.3 First article inspection. First article inspection shall consist of the examination and tests specified in table II, First article inspection shall be performed on material coupons taken from a lot of material slated for fabrication o
37、f the windows and on the first window produced under this acquisition. If the acquisition is limited to acquisi- tion of material only, the first article inspection shall address itself only to material. 5 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-
38、,-,-MIt-C-24449A (SH) TABLE II. Examinations and tests. Examinations and tests Dimensions Optical uniformity and distortion Visual defects Hardness, Rockwell M Specific gravity Refractive index Luminous transmittance Heat distort article inspection report in accordance with the data ordering documen
39、t included in the contract (see 6.2.2). 4.4 Quality conformance insj,ection. Quality conformance inspection shall consist of the examination and tests of table II and shall be performed on individual lots of products (sheet stock castings, custom castings, and finished windows) submitted for accepta
40、nce. 6 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1 NIL-C-24447A 73 7777706 0338707 5 . 4.4.1 Quality conformance insp,ection report. The contractor shall prepare quality conformance inspection reports with each shipment in accordance with the d
41、ata ordering document included in the contract (see 6.2.2). The contractor shall furnish four copies of a report of the results of the tests for physical properties, mechanical properties, chemical properties, inclusion ratio, and other data for the material in the shipment to the extent required by
42、 this .specification, Reports shall include the purchase order number, manufacturer of materials, manufac- turers trade name, and manufacturers lot number of the polymerized castings. 4.5 Samp1,ing. 4.5.1 E. A lot of sheet stock or custom castings shall consist of material produced at one time from
43、the same batch of raw materials. A lot of windows shall consist of all windows fabricated from a single lot of material, 4.5.2 Sheet stock castins. From each lot of sheet stock produced, all the test coupons required by tests of table II shall be taken from a single- sheet chosen at random from the
44、lot. 4.5.3 Custom casting. All the test coupons shall be taken from a single custom casting selected at random from each lot and subjected to the examination and tests specified in table II. 4,5.4 In a case where a lot of windows is to be fabricated from several sheets or from custom castings belong
45、ing to different lots of castings, all the lots of material shall be inspected for conformance to the requirements of table II, 4.5.5 Individual sheets or custom castings belonging to different lots of material which have not been previously inspected for quality conformance to 4.4, shall be individ
46、ually inspected for quality conformance. 4.5.6 Regardless of the size of window lots, each finished window shall be examined individually for conformance to requirements of 3.3.1, 3.3.2, and 3.3.3. 4.5.7 Rejection, If any of the requirements of 3.3 are not met, the entire lot of material or windows
47、shall be rejected. 4.5.8 Retest. Rejected lots of windows may be resubmitted if the defect was not in the material and the subsequent rework brings the windows up to the requirements of 3.3. 4.6 Examination. 4.6.1 Visual defects. Defects such as cracks, checks, and crazing shall be determined visual
48、ly with the unaided eye, except what is necessary to correct for 20 - 20 vision. 7 I: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-C-24449A (SHI 4.6.2 =ensionS. Dimensions shall be determined by micrometer. 4.7 Test methods, Test methods shall
49、 be in accordance with the methods specified iP.7.1 through 4.7.16, Unless otherwise specified herein, test specimens shall be prepared and conditioned as described in the cited ASTM standard. I 4,7.1 Refractive index. Refractive index shall be determined in accordance with ASTM D 542, method A. Two specimens shall be tested. 4,7.2 Thermal expansion. Thermal expansion shall be measured in accordance with ASTM D 696. Two specimens shal
