plastic translucent sheets made from thermosetting polyester resin (glass fibre reinforced)

IS 12866: Scope - Key Specifications & Tables

Scope (Clause 4.2 & 4.5):
Covers dimensions and tolerances of Glassfibre Reinforced Corrugated Translucent Rooflight Sheets.

Table 1: Dimensions & Tolerances (All in mm)

Clause 6.8: Light Transmission (Table 4)

Notes:

• Length tolerance is ±0.5% of sheet length.
• Light transmission depends on sheet colour; tinted sheets require agreement on transmission values.
• Dimensions are critical for installation and performance.

flowchart LR
    A[IS 12866 Scope

IS 12866 - Referenced Standards & Key Tables

Referenced Indian Standards (Clause 2.1)

These are essential adjuncts to IS 12866 for materials and profiles:

• IS 277:1965 — Galvanized steel sheets (plain & corrugated)
• IS 459:1970 — Unreinforced corrugated asbestos cement sheets
• IS 1254:1975 — Corrugated aluminium sheets
• IS 6746:1972 — Unsaturated polyester resin systems
• IS 11551:1986 — Glass fibre chopped strand mat for polyester resin reinforcement

Table 1: Dimensions & Tolerances of Corrugated Sheets (Clause 4.5)

All dimensions in millimeters.

Notes:

• Tolerances are critical for fit and performance.
• Length tolerance is ±0.5% of sheet length.
• Refer to IS 12866 Table 1 for full profiles and dimensions.

flowchart LR
    A[IS 12866] --> B[Material Profiles]
    B --> C[Asbestos Cement Sheets]
    B --> D[Steel Corrugated

IS 12866: Materials and Resin Specifications Summary

Resin Specifications (Clause 3.3)

• Type: Special grade unsaturated polyester resin
• Refractive Index: 1.53 (matching glass fibre)
• Testing Standard: IS 6746:1972 (Physical data in liquid state)
• Key Properties:

  Property	Value	Test Method/Remarks
  Viscosity at 25°C	400 to 500 cps	Brooke-field LVF spindle 2 / 12 rpm
  Specific Gravity at 20°C	1.11
  Acid Number	25 to 30 mg KOH/g
  Solids Content	65%

Glass Fibre Specifications (Clause 3.2)

• Form: Chopped strand mat
• Binder: Highly soluble modified polyester (IS 11551:1986)
• Density: 450 g/m²
• Minimum Width: 500 mm

Profiles, Dimensions & Tolerances (Clause 4.5)

• Sheet Types: Corrugated asbestos cement, steel, aluminium sheets
• Typical Dimensions:

*(Refer to Clause 4.5 Table for

IS 12866: Profiles, Dimensions, and Tolerances for Glassfibre Reinforced Corrugated Translucent Rooflight Sheets

Key Specifications (from Table 1, Clause 4.1 & 4.2):

Notes:

• Depth of Corrugation (D) and Pitch (P) define the profile shape.
• Overall Width (B) and Effective Width (T) are critical for coverage and overlap.
• Minimum Thickness (T) ensures structural strength.
• Length tolerance is ±0.5% of the sheet length.
• Profiles conform to IS 277:1985 (Steel), IS 459:1970 (Asbestos Cement), IS 1254:1975 (Aluminium).

Summary of

IS 12866: Workmanship and Finish - Key Points

1. Workmanship (Clause 4.6 & 7.2.1)

• Pitch Measurement:
  Measure total length over 6 corrugation pitches.
  The length over 6 pitches must be within tolerances of:
  [ \text{Length over 6 pitches} = 6 \times \text{Specified pitch} \pm \text{Tolerance (Table 1)} ]

• Visual Inspection:
  Sheets must be free from visual defects and measured for dimensional accuracy.

2. Special Finishes (Clause 5.3)

• Fibreglass or polyester mats may be applied on weather-exposed surfaces for improved weather resistance.
• PVF or polyester cladding films can be bonded for enhanced weathering and chemical resistance.

3. Dimensional Tolerances (Table 1 excerpt)

Note: Values vary by sheet type (asbestos cement, steel, aluminium). Refer to full Table 1 for details.

flowchart TD
    A[Measure length over 6 pitches] --> B{Is length within tolerance?}
    B -- Yes --> C[Accept sheet]
    B -- No --> D[Reject sheet]
    C --> E[Check visual defects]
    E -- No defects --> F[Pass workmanship]
    E -- Defects --> D

Summary:
Ensure dimensional accuracy per Table 1, inspect for visual defects, and apply special finishes as needed for durability.

IS 12866: Performance Requirements Summary

1. Dimensions & Tolerances (Clause 4.5, Table 1)

• Depth of Corrugation (D): Varies by profile, e.g., 48 mm ±3 for asbestos cement sheets.
• Pitch of Corrugation (P): E.g., 146 mm ±6 for asbestos cement.
• Overall Width (B): E.g., 1050 mm ±10.
• Effective Width: Slightly less than overall width.
• Minimum Thickness (T): E.g., 1.1 mm ±0.15 for asbestos cement.
• Length of Sheet (A): Typically 750 mm to 3600 mm, tolerance ±0.5%.

2. Light Transmission (Clause 6.8, Table 4)

• Transmission tested per Annex G.
• Coloured sheets' transmission subject to agreement.

3. Surface Finishes (Clause 5.3)

• Fiberglass or polyester mats applied for weather resistance.
• PVF/polyester films bonded for enhanced durability.

Practical Use Formula:

Tolerance on Length (L):
[ \Delta L = \pm 0.5% \times L ]

flowchart LR
    A[Sheet Dimensions] --> B[Depth, Pitch, Width, Thickness]
    A --> C[Length with ±0.5% tolerance]
    D[Light Transmission] --> E[Class I-IV with min %]
    F[Surface Finishes] --> G[Fiberglass/Polyester Mats]
    F --> H[PVF/Polyester Films]

This concise summary covers key performance specs for translucent rooflight sheets per IS 12866.

IS 12866: Sampling and Testing - Key Points

Sampling (Clause 7.1.3 & Table 5)

• Sample size depends on lot size:

• Sheets are selected randomly from the lot.

Testing (Clause 1.1 & Annex G)

• Three test specimens are required per test.
• Transmission tests follow Annex G.
• Gradient constant must lie within limits of Table 4 (Minimum Total Light Transmission):

• For tinted sheets, minimum transmission is agreed upon between purchaser and manufacturer.

Dimensions & Tolerances (Clause 4.5 & Table 1)

• Corrugated sheets have specified depths, pitches, widths, thicknesses, and tolerances.
• Length tolerance is typically ±0.5% of length.

Summary Diagram: Sampling & Testing Flow

flowchart TD
    A[Lot of Sheets] --> B[Random Sampling]
    B --> C{Lot Size?}
    C -->|Up to 500| D[Select 3 Sheets]
    C -->|501-1000| E[Select 5 Sheets]
    C -->|1001-1500| F[Select 7 Sheets]
    C -->|1501+| G[Select 10 Sheets]
    D & E & F & G --> H[Prepare 3 Test Specimens Each]
    H --> I[Conduct Transmission Test (Annex G)]
    I --> J{Check Gradient Constant}
    J -->|Within Limits| K[Pass]
    J -->|Outside Limits| L[Fail]

This ensures quality control by statistically valid sampling and standardized testing per IS 12866.

IS 12866: Transport and Storage Key Points

Transport (Clause 6.8 & Table 4)

• Light Transmission Requirements for translucent sheets depend on diffusion classification:

• For tinted sheets, transmission values are agreed upon between purchaser and manufacturer.
• Gradient constant (Annex G) must comply with limits in Table 4.

Storage (Clause 8.1)

• Sheets must be stored flat on clean battens spaced at 1500 mm centers.
• Protect sheets from wind to avoid displacement.
• When stored outdoors, always cover with waterproof covers to prevent water entrapment, which causes discoloration under sunlight.

Summary Diagram: Storage Setup

graph LR
A[Flat Storage] --> B[Clean Battens @ 1500mm centers]
B --> C[Sheets Laid Flat]
C --> D[Waterproof Cover (if outdoors)]
D --> E[Prevents Water Entrapment & Discoloration]

This ensures longevity and maintains optical properties of translucent sheets during storage and transport.

IS 12866: Method of Test for Glass Content (Clause 6.2, Annex A)

Procedure Summary (Annex A, Clause 1.1)

• Weigh specimen + crucible (previously ignited and weighed).
• Place specimen in furnace; raise temperature gradually to 565 ± 28℃ (max 343℃ initially).
• Maintain at max temperature until constant weight (2-6 hours depending on thickness).
• Cool in desiccator and weigh residue.

Key Formula:

[ \text{Glass content, wt %} = \frac{W_2}{W_1} \times 100 ]

• (W_1) = Original weight of specimen
• (W_2) = Weight of residue after ignition (glass + inorganic filler)

Specification:

• Minimum glass content = 30% by weight in the laminate.

Notes:

• Temperature rise must be controlled to avoid blowing or loss of filler.
• Constant weight means repeated weighing until weight difference is negligible.

flowchart TD
    A[Weigh specimen + crucible] --> B[Place in furnace]
    B --> C[Raise temp to 565 ± 28℃ gradually]
    C --> D[Maintain temp until constant weight (2-6 hrs)]
    D --> E[Cool in desiccator]
    E --> F[Weigh residue]
    F --> G[Calculate glass content using formula]

This test ensures accurate quantification of glass fiber content in FRP laminates per IS 12866.

IS 12866: Method of Test for Water Absorption (Clause 6.3 & Annex B-1)

Test Procedure:

• Sample Size:
  • Square: 50 × 50 mm
  • Circular: Diameter 30 mm
• Preparation:
  • Coat edges with resin to prevent inter-laminar absorption.
  • Clean and dry in air bath at 50 ± 3°C for 24 h.
  • Cool in desiccator, weigh immediately (W₁).
• Immersion:
  • Immerse in distilled water at 27 ± 2°C for 24 h.
  • Remove, wipe surface dry, weigh immediately (W₂).

Formula for Water Absorption:

[ A = \frac{W_2 - W_1}{W_1} \times 100 ]

Where:

• A = absorption coefficient (%)
• W₁ = weight before immersion
• W₂ = weight after immersion

Specification:

• Water absorption shall not exceed 0.3%.

Summary Table:

flowchart TD
    A[Cut test piece] --> B[Coat edges with resin]
    B --> C[Clean and dry at 50±3°C for 24h]
    C --> D[Cool in desiccator]
    D --> E[Weigh immediately (W₁)]
    E --> F[Immerse in distilled water at 27±2°C for 24h]
    F --> G[Remove, wipe dry]
    G --> H[Weigh immediately (W₂)]
    H --> I[Calculate absorption: ((W₂-W₁)/W₁)*100]

This method ensures reliable measurement of water absorption for composite sheets per IS 12866.

IS 12866: Method of Test for Barcol Hardness (Annex C, Clause 6.4)

Key Specifications:

• Specimen size: 150 mm × 30 mm, flat, with long dimension along sheet's longitudinal direction.
• Holes: Two holes drilled on specimen centerline, 38 mm from each end, using 0.8 mm twist drill.
• Support: Specimen fully supported on wooden backing during drilling.

Test Procedure (Clause 1.1):

• Indentor held perpendicular to test surface.
• Apply light hand pressure to drive spring-loaded indentor.
• Take hardness reading after 10 seconds.
• Perform at least 5 tests and average the readings.

Acceptance Criteria (Clause 6.4):

• Barcol hardness shall not increase by more than 30% of initial value after testing.

Summary Table:

flowchart TD
    A[Prepare Specimen 150x30 mm] --> B[Drill 2 holes (0.8 mm dia, 38 mm from ends)]
    B --> C[Support specimen on wooden backing]
    C --> D[Place Barcol indentor perpendicular]
    D --> E[Apply light hand pressure]
    E --> F[Record hardness after 10 seconds]
    F --> G[Repeat 5 times and average]
    G --> H[Check hardness increase ≤ 30%]

This ensures consistent, reliable Barcol hardness measurement per IS 12866.

IS 12866 - Bolt Shear Test (Clause 6.5 & Annex D)

Key Specifications:

• Minimum average load at first tear: ≥ 375 N (arithmetic mean of all specimens)
• Minimum load at first tear for any specimen: ≥ 250 N

Test Setup (Clause E-1.2):

• Test rig with bearers and runners equal to sheet width.
• Bearers: 50 mm wide, level, parallel.
• Timber blocks placed at 1/4 span from bearers to distribute load on flat areas, avoiding corrugation ridges.
• Load spreader symmetrically over runners.
• Timber weight included in total load.

Procedure Summary:

1. Place specimen on rig.
2. Apply load gradually until first tear appears.
3. Record load at first tear for each specimen.
4. Calculate arithmetic mean of all specimens.

Important:

• The test ensures bolt shear strength of sheets under load.
• Load at tear indicates bolt shear resistance.

Load Criteria Summary Table:

Diagram of Test Setup (simplified):

graph LR
A[Bearer (50 mm wide)] --> B[Timber Block (at 1/4 span)]
B --> C[Sheet Specimen]
C --> D[Load Spreader]
D --> E[Applied Load]

This method ensures uniform load distribution to test bolt shear strength per IS 12866 Annex D.

IS 12866: Load Deflection Test Method (Clause 6.6 & Annex E)

Key Specifications:

• Applicable to: Corrugated and curved flat sheets, thickness ≥ 1.10 + 0.15 mm.
• Test setup: Three sheets tested simultaneously.
• Load application: Incremental, steady, uniform up to specified total load (Table 2).
• Load holding: Maintain for ≥ 5 minutes.
• Deflection limit: Max 15 mm (Span/70) at sheet center.

Table 2: Total Load (N) per Profile

Procedure Summary (E-1.3):

• Apply load incrementally to the least load in Table 2.
• Maintain load for 5 minutes.
• Measure deflection at underside center of corrugation.
• Record deflection for each sheet separately.
• No rupture allowed; minor cracking near supports/load points permitted.

Test Setup (Fig. 1):

• Sheet length: 1360 mm
• Supports: Timber runners and bearers (100 × 50 mm)
• Loading platform on top.

flowchart TD
    A[Start Test] --> B[Place 3 sheets on timber runners]
    B --> C[Apply load incrementally to specified total load]
    C --> D[Maintain load for 5 minutes]
    D --> E[Measure center deflection under load]
    E --> F{Deflection ≤ 15 mm?}
    F -- Yes --> G[Pass Test]
    F -- No --> H[Fail Test]

Summary: The test ensures sheets can withstand specified loads with deflection ≤ 15 mm and no rupture, verifying structural adequacy under service loads.

IS 12866 - Light Diffusion Test Method (Clause 6.7)

Test Setup (Annex F, Fig. 2)

• Apparatus:
  • Box: 1350 mm (L) × 250 mm (W) × 300 mm (H)
  • Lamp: 60 V tungsten filament, vertical, in lamp house with matt white end wall
  • Illuminating slit A: 300 mm high × 20 mm wide, chamfered edges, 360 mm from lamp
  • Photocell: Selenium rectifier-type, 60 mm diameter sensitive surface
  • Photocell slit B: Movable, 25 mm wide × 240 mm high, chamfered edges, slides to measure shadow edge
  • Interior: Between slits painted matt black; lamp house and photocell compartments matt white

Key Formula: Gradient Constant ( G )

• Calculated from photometric readings (details in Annex F)
• Used to classify diffusion level of sheet material.

Classification Limits (Table 3)

Additional Specification: Minimum Total Transmission (Table 4)

Summary:

• Use the slit diffusion photometer setup to measure light diffusion.
• Calculate gradient constant ( G ).
• Classify sheets per ( G ) values (Table 3).
• Ensure minimum transmission values as per classification (Table 4).

flowchart LR
    A[Light Source] -->|Slit A (20 mm × 300 mm)| B[Sample]
    B -->|Light passes through| C[Movable Slit B (25 mm × 240 mm)]
    C --> D[Photocell Detector]
    D --> E[

IS 12866: Measurement of Total Light Transmission (Clause 6.8 & Annex G)

Key Specifications:

• Minimum Total Light Transmission (Table 4):

• For tinted sheets, transmission depends on coloring and is agreed upon by purchaser and manufacturer.

Measurement Procedure (Annex G - Integrating Box Photometer):

1. Lamp Preparation:

   • Turn on fluorescent lamps; stabilize for 15 min.
   • Maintain constant voltage supply.

2. Readings:

   • ( R_1 ): Reading without sample (initial).
   • ( R_2 ): Reading with sample.
   • ( R_3 ): Reading without sample (final).

3. Check:

   • ( R_1 ) and ( R_3 ) should be nearly equal; use mean ( \frac{R_1 + R_3}{2} ).

4. Calculate Total Light Transmission ( T % ):

[ T = \frac{R_2}{\frac{R_1 + R_3}{2}} \times \text{Correction Factor} \times 100 ]

Notes:

• The Correction Factor accounts for instrument calibration (denoted as ( B' ) in the code).
• Light diffusion is separately tested by slit diffusion photometer (Clause 6.7).

flowchart TD
    A[Start: Turn on lamps] --> B[Stabilize 15 min]
    B --> C[Record R1 (no sample)]
    C --> D[Place sample, record R2]
    D --> E[Remove sample, record R3]
    E --> F{Check if R1 ≈ R3}
    F -- Yes --> G[Calculate mean (R1+R3)/2]
    F -- No --> H[Repeat readings]
    G --> I[Calculate Transmission T%]
    I --> J[Report results]

This ensures accurate, standardized measurement of light transmission per IS 12866.