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British standards for composites
British standards for composites 4. Sheet materials based on glass fibre v. EDWARDS B r i t i s h Standards have been issued c o v e r i n g f l a t sheets c o n t a i n i n g d i f f e r e n t t y p e s o f resin, c o p p e r - c l a d versions f o r p r i n t e d c i r c u i t r y and c o r r u g a t e d sheeting.
The earlier articles in this series have been chiefly concerned with the raw materials used in the manufacture of composites; the resins and reinforcements. Mention has also been made of combinations of these materials which require moulding by a suitable method to produce the finished article. A considerably larger number of standards and specifications have been issued on the finished or semifinished products made from them. The British Standards Institution have published standards on composite materials based on most of the common types of thermosetting resin and reinforcements including fiat sheets for both industrial and decorative applications, corrugated sheeting, rods and tubes. A standard on the construction of vessels and tanks made in reinforced plastics is also available.
Epoxide resin: Grades EP1 and EP2 both have good elec. trical properties but EP2 has the better mechanical properties. Melamine resin: Grades MF1 and MF2. MF1 has improved electrical properties. Phenolic resin: Only one Grade, PF1. Polyesterresin:Grades PR1, PR2 and PR3. PR2 is classed as general purpose. PR1 has better electrical properties and PR3 has fire retardant properties. Silicone resin: Grades SILl, SIL2, SIL3 differ primarily in their electrical properties; SILl being the highest quality.
Sheet materials based on glass fibre reinforcement are the subject of three standards: BS 3953:1965 Synthetic resin bonded woven glass fabric laminated sheet;BS 4584:1970 Metal clad base materials for printed circuits; BS 4154:1967 Corrugated plastics translucent sheets made from thermosetting polyester resins (glass fibre reinforced).
The requirements of these materials are given in Table 1. These tests together with the water absorption (the allowable values of which vary with the laminate thickness) are those normally used for control testing. Impact strength, tensile strength and, where appropriate, electric strength in oil at 90°C are tested less frequently. In Part 2 of this standard, published in 1968, the British Government Services requirements are given for Types SILl and SIL2 sheet. It describes sampling and inspection procedures, defines the tests which must be carried out for type approval and those which must be carried out on each batch and on each sheet. The quality requirements are the same as those quoted in Part 1. BS 3953 is at present undergoing revision by Technical Committee PLC/41 of the British Standards Institution. A draft was published for comment
BS 3953:1965
This specification covers laminates made from E-glass fabric bonded with epoxide, melamine, phenolic, polyester or silicone resins. Within each combination of glass and resin there are several grades in which certain properties are enhanced. QMC Industrial Research Ltd, 229 Mile End Road, London E1 4AA
Table 1. Main property requirements for BS 3953:1965 laminates EP1
EP2
MF1
MF2
PF1
PR1
PR2
PR3
SILl
SIL2
SIL3
Flexural strength, MN/m 2
241
310
103
138
124
215
173
138
103
124
89
Electric strength (edgewise), KV
30
30
15
5
-
35
30
-
30
25
20
Power factor @ 1MHz
0.035
0.035
0.025
-
-
0.04
0.05
-
0.003
0.004
0.01
Permittivity @ 1MHz
5.5
5.5
7.5
-
-
4.5
4.9
-
4.0
4.3
4.8
0.1
-
-
-
1000
100
10
Insulation resistance, M£ 100 (after water immersion)
COMPOSITES. M A Y 1975
100
1
10
131
in 1974. Revision has become necessary because certain types of laminate have become obsolete and new types have been introduced. The opportunity has also been taken to align the standard with the ISO Recommendation R 1642 'Plastics. Basis for specification for industrial laminated sheets based on thermosetting resins'.
Table 2. Main property requirements for BS 4584:1970 copper-clad laminate EP-GC-Cu-2
Surface resistivity, M~ (minimum)
50 000
Changes proposed in the new draft include increasing the number of epoxide resin laminates from two to five and introducing a new grade of melamine laminate. Silicone laminate Grade SIL3 is deleted.
Volume resistivity, M~ (minimum)
20 000
The property requirements of the three polyester laminates and the remaining silicone laminates in the draft are generally similar to those in BS 3953:1965. Additional electrical strength and insulation resistance tests will be required to be carried out on the phenolic laminate. All the melamine and epoxide resin based materials will need to have better electrical properties and the new grades will be required to have self-extinguishing properties and/or be tested for their retention of strength after short term ageing at 150°C.
BS 4584:1970
This standard is published in several parts. Part 1 describes test methods and Parts 2 and 3 cover copper clad epoxide resin/glass laminates. Part 2 is entitled 'Epoxide woven glass fabric copper-clad laminated sheet, general purpose grade: EP-GC-Cu-2'. It defines a single grade of material which may be supplied having 305 or 610 g/m 2 copper foil bonded on the surface. The standard prescribes the allowable tolerances in laminate thickness and copper cladding. Performance requirements are generally confined to electrical properties and tests on the bond strength between the foil and the base laminate (see Table 2). Part 3 of this standard describes a flame retardant grade of laminate coded EP-GC-Cu-3. Performance should be similar to EP-GC-Cu-2 but must also undergo a flammability test carried out on the laminate with the foil removed.
BS 4154:1967
The corrugated translucent sheets covered by this standard are required to be made with a profile matching that specified in the British Standard for the particular material which will
132
Laminate properties
Surface resistivity @ 125°C, M ~ (minimum)
1 000
Volume resistivity @ 125°C, M~ (minimum)
100
Permittivity, (maximum)
5.5
Loss tangent, (maximum)
0.040
Foil adhesion properties
Pull-off strength, N (minimum)
90
Peel strength after 10 s @ 260°C, kN/m (minimum)
1.4
Peel strength after 500 h @ 125°C, kN/m (minimum)
1.4
Peel strength after exposure to solvent vapour, kN/m (minimum)
1.4
Peel strength after exposure to simulated plating conditions, kN/m (minimum)
1.2
surround it when it is installed. Details will be found in the following standards: BS 690. Corrugated asbestos cement sheets Type A, B or C BS 2855.Corrugated aluminium sheets BS 3428. Troughed atuminium sheets BS 3083.Galvanised corrugated steel sheets of 8/3 or 10/3 corrugations Unless otherwise specified a polyester resin meeting the physical property requirements of Table 1 in BS 3532 should be used in the manufacture of the sheet. On the finished material fire tests as described in BS 476 Parts 3 and 7 must be carried out. Although no level of performance is specified the designation achieved must be stated. Other tests required are a Bolt Shear Test, a Load Deflection Test, a Light Diffusion Test and a Light Transmission Test. The standard concludes with recommendations for fixing the sheets to supports and surrounding materials. Types of fixings are covered in BS 1496 Part 1.
COMPOSITES. MAY 1975
The earlier articles in this series have been chiefly concerned with the raw materials used in the manufacture of composites; the resins and reinforcements. Mention has also been made of combinations of these materials which require moulding by a suitable method to produce the finished article. A considerably larger number of standards and specifications have been issued on the finished or semifinished products made from them. The British Standards Institution have published standards on composite materials based on most of the common types of thermosetting resin and reinforcements including fiat sheets for both industrial and decorative applications, corrugated sheeting, rods and tubes. A standard on the construction of vessels and tanks made in reinforced plastics is also available.
Epoxide resin: Grades EP1 and EP2 both have good elec. trical properties but EP2 has the better mechanical properties. Melamine resin: Grades MF1 and MF2. MF1 has improved electrical properties. Phenolic resin: Only one Grade, PF1. Polyesterresin:Grades PR1, PR2 and PR3. PR2 is classed as general purpose. PR1 has better electrical properties and PR3 has fire retardant properties. Silicone resin: Grades SILl, SIL2, SIL3 differ primarily in their electrical properties; SILl being the highest quality.
Sheet materials based on glass fibre reinforcement are the subject of three standards: BS 3953:1965 Synthetic resin bonded woven glass fabric laminated sheet;BS 4584:1970 Metal clad base materials for printed circuits; BS 4154:1967 Corrugated plastics translucent sheets made from thermosetting polyester resins (glass fibre reinforced).
The requirements of these materials are given in Table 1. These tests together with the water absorption (the allowable values of which vary with the laminate thickness) are those normally used for control testing. Impact strength, tensile strength and, where appropriate, electric strength in oil at 90°C are tested less frequently. In Part 2 of this standard, published in 1968, the British Government Services requirements are given for Types SILl and SIL2 sheet. It describes sampling and inspection procedures, defines the tests which must be carried out for type approval and those which must be carried out on each batch and on each sheet. The quality requirements are the same as those quoted in Part 1. BS 3953 is at present undergoing revision by Technical Committee PLC/41 of the British Standards Institution. A draft was published for comment
BS 3953:1965
This specification covers laminates made from E-glass fabric bonded with epoxide, melamine, phenolic, polyester or silicone resins. Within each combination of glass and resin there are several grades in which certain properties are enhanced. QMC Industrial Research Ltd, 229 Mile End Road, London E1 4AA
Table 1. Main property requirements for BS 3953:1965 laminates EP1
EP2
MF1
MF2
PF1
PR1
PR2
PR3
SILl
SIL2
SIL3
Flexural strength, MN/m 2
241
310
103
138
124
215
173
138
103
124
89
Electric strength (edgewise), KV
30
30
15
5
-
35
30
-
30
25
20
Power factor @ 1MHz
0.035
0.035
0.025
-
-
0.04
0.05
-
0.003
0.004
0.01
Permittivity @ 1MHz
5.5
5.5
7.5
-
-
4.5
4.9
-
4.0
4.3
4.8
0.1
-
-
-
1000
100
10
Insulation resistance, M£ 100 (after water immersion)
COMPOSITES. M A Y 1975
100
1
10
131
in 1974. Revision has become necessary because certain types of laminate have become obsolete and new types have been introduced. The opportunity has also been taken to align the standard with the ISO Recommendation R 1642 'Plastics. Basis for specification for industrial laminated sheets based on thermosetting resins'.
Table 2. Main property requirements for BS 4584:1970 copper-clad laminate EP-GC-Cu-2
Surface resistivity, M~ (minimum)
50 000
Changes proposed in the new draft include increasing the number of epoxide resin laminates from two to five and introducing a new grade of melamine laminate. Silicone laminate Grade SIL3 is deleted.
Volume resistivity, M~ (minimum)
20 000
The property requirements of the three polyester laminates and the remaining silicone laminates in the draft are generally similar to those in BS 3953:1965. Additional electrical strength and insulation resistance tests will be required to be carried out on the phenolic laminate. All the melamine and epoxide resin based materials will need to have better electrical properties and the new grades will be required to have self-extinguishing properties and/or be tested for their retention of strength after short term ageing at 150°C.
BS 4584:1970
This standard is published in several parts. Part 1 describes test methods and Parts 2 and 3 cover copper clad epoxide resin/glass laminates. Part 2 is entitled 'Epoxide woven glass fabric copper-clad laminated sheet, general purpose grade: EP-GC-Cu-2'. It defines a single grade of material which may be supplied having 305 or 610 g/m 2 copper foil bonded on the surface. The standard prescribes the allowable tolerances in laminate thickness and copper cladding. Performance requirements are generally confined to electrical properties and tests on the bond strength between the foil and the base laminate (see Table 2). Part 3 of this standard describes a flame retardant grade of laminate coded EP-GC-Cu-3. Performance should be similar to EP-GC-Cu-2 but must also undergo a flammability test carried out on the laminate with the foil removed.
BS 4154:1967
The corrugated translucent sheets covered by this standard are required to be made with a profile matching that specified in the British Standard for the particular material which will
132
Laminate properties
Surface resistivity @ 125°C, M ~ (minimum)
1 000
Volume resistivity @ 125°C, M~ (minimum)
100
Permittivity, (maximum)
5.5
Loss tangent, (maximum)
0.040
Foil adhesion properties
Pull-off strength, N (minimum)
90
Peel strength after 10 s @ 260°C, kN/m (minimum)
1.4
Peel strength after 500 h @ 125°C, kN/m (minimum)
1.4
Peel strength after exposure to solvent vapour, kN/m (minimum)
1.4
Peel strength after exposure to simulated plating conditions, kN/m (minimum)
1.2
surround it when it is installed. Details will be found in the following standards: BS 690. Corrugated asbestos cement sheets Type A, B or C BS 2855.Corrugated aluminium sheets BS 3428. Troughed atuminium sheets BS 3083.Galvanised corrugated steel sheets of 8/3 or 10/3 corrugations Unless otherwise specified a polyester resin meeting the physical property requirements of Table 1 in BS 3532 should be used in the manufacture of the sheet. On the finished material fire tests as described in BS 476 Parts 3 and 7 must be carried out. Although no level of performance is specified the designation achieved must be stated. Other tests required are a Bolt Shear Test, a Load Deflection Test, a Light Diffusion Test and a Light Transmission Test. The standard concludes with recommendations for fixing the sheets to supports and surrounding materials. Types of fixings are covered in BS 1496 Part 1.
COMPOSITES. MAY 1975