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This specification replaces GJB 1251-1991 Specification for YB-3 aircraft acrylic plastic sheet.
The following technical changes have been made with respect to GJB 1251-1991:
a) The designations and requirements of YB-2 and YB-4 sheets have been supplemented, and the name was revised to Specification for cast acrylic plastic sheet of aircraft;
b) The thickness ranges of the sheet have been expanded from the original thickness of 3 mm, 4 mm, 5 mm, 8 mm and 10 mm to 0.8 mm ~ 120 mm;
c) Part of physical and chemical performance index has been modified, in which the impact strength of YB-3 sheets with thickness less than 6mm has been modified from 18.0 kJ/m2 to 16.0 kJ/m2;
d) Part of test condition has been modified, in which the annealing temperature of stress-solvent craze has been revised from 125°C to 135°C;
e) Some test items have been modified, such as canceling Brinell hardness test item, and changing the light resistance inspection from monthly inspection to appraisal inspection, etc.
Annex A of this specification is normative.
This specification was proposed by the China Petroleum and Chemical Industry Association.
This specification is under the jurisdiction of Liming Research & Design Institute of Chemical Industry.
This specification was issued in October 1991 for the first time.
Specification for cast acrylic plastic sheet
of aircraft
1 Scope
This specification specifies the requirements, quality assurance specification and delivery preparation of cast acrylic plastic sheet of aircraft.
This specification is applicable to the cast acrylic plastic sheet of aircraft prepared from the homopolymer of plasticized and unplasticized methyl methacrylate and the copolymer of methyl methacrylate and methacrylic acid.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this specification. For dated reference, subsequent amendments to (excluding any corrigendum), or revisions of, any of these publications do not apply. However, parties to agreements based on this specification are encouraged to investigate the possibility of applying the most recent editions of the documents indicated below. For undated references, the latest edition of the normative document referred to applies.
GB/T 191-2000 Packaging — Pictorial marking for handling of goods
GB/T 1040-1992 Plastics — Determination of tensile properties
GB/T 1043-1993 Plastics Determination of charpy impact strength of rigid materials
GB/T 1250-1989 Rules for expression and judgement of limiting values
GB/T 1634.2-2004 Plastics — Determination of temperature of deflection under load — Part 2: Plastics, ebonite and long-fibre-reinforced composites
GB/T 2410-1980 Transparent plastics — Transmissivity and haze test
GB/T 2918-1998 Plastics - Standard atmospheres for conditioning and testing
HB 6657-1992 Test method for craze of acrylic plastic sheet of aircraft
3 Requirements
3.1 Color
Colorless and transparent.
3.2 Appearance
The appearance of sheet with nominal size of 1400 mm × 1600 mm shall meet the requirements of Table 1. The requirements of other sizes shall be increased or decreased according to the area ratio, and the calculation results of the number of defects shall be rounded off. Defects within 50 mm from the positive tolerance and the edge shall not be counted.
Table 1
Item Index
Grade A Grade B Grade C
Impurity The diameter is not greater than 0.3mm A small amount of dispersion is allowed. The degree of dispersion shall not affect the visual clarity.
The diameter is greater than 0.3mm and not greater than 1.5 mm There are no more than 3 dispersions with a diameter of not more than 0.8 mm in the main visual area and the distance between dispersions are not less than 200 mm, and those larger than 0.8 mm are not allowed. There are no more than 8 dispersions with a diameter of not more than 1.5 mm in the non-main visual area and the distance between dispersions are not less than 200 mm. Defects outside the blanking area are not counted. There are no more than 15 dispersions, and the distance between dispersions are not less than 200 mm. There are no more than 15 dispersions with a diameter of not more than 1.0 mm and the distance between dispersions are not less than 200 mm, and those larger than 1.0 mm are not allowed.
The diameter is not greater than 1.5 mm Not allowed
Spot defects The diameter is not greater than 0.5 mm A small amount of dispersion is allowed. The degree of dispersion shall not affect the visual clarity.
The diameter is greater than 0.5 mm and not greater than 1.5 mm There are no more than 3 defect dispersions with a diameter of not more than 0.8 mm in the main visual area and the distance between defect dispersions are not less than 200 mm, and those larger than 0.8 mm are not allowed. There are no more than 8 defect dispersions with a diameter of not more than 1.5 mm in the non-main visual area and the distance between dispersions are not less than 200 mm. Defects outside the blanking area are not counted. There are no more than 15 dispersions, and the distance between dispersions are not less than 200 mm. There are no more than 15 dispersions with a diameter of not more than 1.0 mm and the distance between dispersions are not less than 200 mm, and those larger than 1.0 mm are not allowed.
The diameter is not greater than 1.5 mm Not allowed.
Water stains, mildew, alkali precipitation Defects easily removed with polishing paste are allowed. —
Bubbles, open bubbles, wind marks, indentations, heavy scratches, cracks, crazes, silicon sticking and silicon damage Not allowed.
Filamentous abrasion Dispersion is allowed, and the degree of dispersion shall not affect the visual clarity. —
Light scratch (width less than 0.4 mm and depth less than 0.1 mm) The length is less than 30 mm There are no more than 15 dispersions. There are no more than 25 dispersions. —
The length is between 30 mm and 60 mm There are no more than 8 dispersions. There are no more than 25 dispersions.
The length is greater than 60 mm Not allowed. There are no more than 13 dispersions.
Edge notch depth Not greater than 4 mm
Fluff There are no more than 8 fluffs with a length of not more than 3 mm, but they are not allowed to be exposed on the surface. There are no more than 8 fluffs with a length of not more than 3 mm.
3.3 Width and length
The board surface is generally rectangular, and its width and length shall meet the requirements of Table 2. If the user needs plates of other sizes, it shall be settled by both parties through negotiation.
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Table 2 In mm
Width Length
1550+100 -50 1750+100 -50
1400+100 -50 1600+100 -50
650+50 -50 650+50 -50
Plates with nominal dimensions of 650 mm in width and length are generally those with thickness less than 2 mm.
3.4 Thickness
They shall meet the thickness requirements specified in Table 3. YB-4 only refers to sheets with thickness less than 4 mm. If the user needs plates of other thickness, it shall be settled by both parties through negotiation.
Table 3 In mm
3.5 Optical distortion
3.5.1 When the optical distortion is checked by the visual method, there shall be no obvious deformation when sees through the sheet.
3.5.2 When the point light source method is used to inspect the optical distortion, it is required that the optical distortion in the main visual area shall meet the requirements of Table 4 after the next heating of the sheet under molding conditions, and the non-main visual area shall be relaxed by 10%. Defects outside the blanking area are not counted. Optical distortion within 100 mm from the edge of the sheet is not counted.
3.5.3 Grade B and C sheets are not required.
Foreword i
1 Scope
2 Normative references
3 Requirements
4 Quality assurance specification
5 Delivery preparation
6 Instructions
Annex A (Normative) Test method for optical distortion
