Electrical Grade Glass Epoxy Laminates — Maharashtra, India
Fiber Glass Laminates
Fiber glass laminates — also called glass epoxy laminates, glass cloth reinforced epoxy sheets, or GRP laminates — are high-performance composite insulation materials made by bonding layers of woven glass fibre fabric with thermosetting epoxy resin under heat and pressure. The result is a dense, rigid, electrically insulative structural material that offers a combination of mechanical strength, dielectric performance, and thermal stability unmatched by conventional insulation materials.
ACC Insulations manufactures premium electrical grade fiber glass laminates Component in NEMA grades G10, G11, FR4, FR5 and Indian standard grades EPGC 201 and EPGC 202 — covering every application from standard electrical panels to demanding high-voltage transformer and switchgear insulation.
Technical Specifications
| Fiber Glass Laminates — Complete Technical Data | |
|---|---|
| Grades Available | NEMA G10, G11, FR4, FR5, EPGC 201, EPGC 202 |
| Reinforcement | Woven E-Glass Fibre Fabric (glass cloth) |
| Resin System | Epoxy Resin (thermosetting) |
| Thickness Range | 0.1 mm to 150 mm |
| Sheet Lengths | 1000 mm and 1200 mm (custom lengths available) |
| Colours Available | Black, Red, Green, Blue |
| Density | 1.9 – 2.0 g/cm³ |
| Water Absorption | 20 mg (IEC 60893 method D24/23) |
| Flame Retardancy | UL 94-V0 Compliant (FR4, FR5, EPGC grades) |
| Thermal Class | Class F (155°C) and Class H (180°C) |
| Dielectric Strength | High — meets IEC 60893 / NEMA LI-1 requirements |
| Machinability | Excellent — CNC routing, milling, drilling, turning |
| Standards | IEC 60893, NEMA LI-1, UL 94, IS 3258, IEC 60085 |
What Are Fiber Glass Laminates?
Fiber glass laminates are composite structural insulation materials produced by stacking multiple plies of woven glass fibre fabric, impregnating them with epoxy resin, and curing the assembly under heat and pressure in a hydraulic press. The process creates a dense, void-free laminate in which continuous glass fibres carry mechanical loads while the cured epoxy matrix provides chemical resistance, moisture protection, and cohesion between layers.
The term "fiber glass laminate" covers a family of grades — each differing in the type and formulation of epoxy resin — engineered to meet specific electrical, thermal, and mechanical requirements. Understanding which grade is correct for your application is critical: using G10 where G11 is specified, for example, risks mechanical failure above 130°C in a transformer application rated for 155°C continuous service.
Available Grades — Full Description
Each grade has a specific resin system and performance profile. Selecting the correct grade is the most important decision when specifying fiber glass laminates:
General Purpose Glass Epoxy
Standard glass cloth reinforced epoxy laminate rated for continuous service up to ~130°C. Excellent dielectric strength, good machinability. No inherent flame retardancy. Best for terminal boards, electrical panels, and CNC-machined insulation components at ambient to moderate temperatures.
High-Temperature Glass Epoxy
Formulated with an elevated-temperature epoxy resin that retains full mechanical strength at 155°C and above. The correct specification for transformer spacers, phase barriers in hot switchgear, motor slot wedges, and any load-bearing insulation component in continuous high-temperature service.
Flame Retardant Glass Epoxy
The most widely used electrical insulation laminate worldwide. UL 94 V-0 flame retardant, excellent dielectric properties, outstanding machinability. The default choice for PCB substrates, switchgear arc barriers, electrical enclosure panels, and all applications requiring UL94 V-0 compliance.
High-Temp Flame Retardant
Combines the flame retardancy of FR4 with the elevated-temperature mechanical performance of G11. Rated UL 94 V-0 and Class F (155°C). Specified where both flame retardancy and high-temperature strength are simultaneously required — high-MVA transformer applications, high-voltage switchgear.
Indian Standard — General Grade
Indian Standard designation equivalent to G10/FR4 class. Widely specified by Indian transformer and switchgear OEMs in IS-referenced technical documents. Meets IS 3258 and IEC 60893 Type EP GC 201. Standard choice for insulation boards, phase barriers, and machined components in Indian OEM transformer designs.
Indian Standard — High-Temp Grade
Indian Standard equivalent to G11 class with improved mechanical retention at elevated temperatures. Meets IS 3258 and IEC 60893 Type EP GC 202. Specified in IS-referenced transformer designs where Class F thermal performance and high mechanical strength at operating temperature are required.
Grade-by-Grade Comparison
Use this table to quickly identify the correct grade for your application:
| Grade | Thermal Class | Flame Rating | High-Temp Strength | IS Equivalent | Best Application |
|---|---|---|---|---|---|
| G10 | Class B (130°C) | Not rated | Good at room temp | EPGC 201 (partial) | Terminal boards, machined components |
| G11 | Class F (155°C) | Not rated | Excellent >130°C | EPGC 202 | Transformer spacers, motor wedges |
| FR4 | Class B (130°C) | UL94 V-0 | Good at room temp | EPGC 201 | PCB, switchgear panels, arc barriers |
| FR5 | Class F (155°C) | UL94 V-0 | Excellent >130°C | EPGC 202 (FR variant) | HV switchgear, power transformer insulation |
| EPGC 201 | Class B–F | As specified | Standard | G10 / FR4 class | Indian OEM transformer & switchgear |
| EPGC 202 | Class F (155°C) | As specified | High-temperature | G11 class | IS-spec transformer, elevated temp duty |
Available Colours
Fiber glass laminates are available in four standard colours, each identified by its resin pigmentation. Colour coding helps differentiate grades or track component identification during transformer assembly:
Colour is a surface property only and does not affect electrical or mechanical performance. Custom colour requests are available on enquiry.
Thickness Range: 0.1 mm to 150 mm
Our fiber glass laminates are available across the full thickness range required in electrical engineering applications — from very thin inter-layer barriers to solid structural blocks:
Ultra-Thin Sheets
Inter-layer insulation barriers, slot cell liners, PCB substrates
Thin Sheets
Phase barriers, terminal boards, electrical panel insulation
Medium Sheets
Transformer spacers, structural supports, arc barriers
Heavy Sections
CNC-machined mechanical components, HV bushing supports
Key Electrical & Mechanical Properties
Applications of Fiber Glass Laminates
The unique combination of electrical insulation, mechanical strength, and thermal stability makes fiber glass laminates irreplaceable across a wide range of electrical and industrial applications:
Why Fiber Glass Laminates Outperform Conventional Insulation
Compared to phenolic paper laminates, pressboard, and other conventional electrical insulation materials, glass epoxy laminates deliver measurable advantages in every performance dimension:
3–5× Greater Mechanical Strength
Continuous woven glass fibre reinforcement provides tensile and flexural strength far exceeding phenolic paper or pressboard at equivalent thickness, enabling thinner, lighter components.
Retained Strength at Temperature
G11 and FR5 grades maintain full mechanical strength above 130°C where phenolic laminates soften and lose structural rigidity — critical for transformer and motor applications with sustained high operating temperatures.
Far Lower Moisture Absorption
At 20 mg (D24/23), glass epoxy laminates absorb a fraction of the moisture that phenolic or cellulose-based materials do — maintaining stable dielectric strength in humid environments and oil-immersed applications.
Chemical & Oil Resistance
The cross-linked epoxy matrix is chemically stable in transformer mineral oil, synthetic esters, solvents, and mild acids/alkalis — unlike cellulose-based materials that degrade in oil over time.
Excellent CNC Machinability
G10, G11, FR4, and EPGC grades machine precisely with CNC routers and mills — producing tight-tolerance components, clean drilled holes, and smooth profiles that phenolic laminates cannot match without delamination.
Dimensional Stability
Glass epoxy laminates do not swell or shrink significantly with temperature or humidity changes — maintaining consistent fit and electrical clearances over the full service life of the equipment.
Manufacturing Process at ACC Insulations
ACC Insulations produces fiber glass laminates through a controlled multi-stage hot-press lamination process that ensures consistent resin content, uniform glass distribution, and void-free laminate quality across every sheet:
- Glass fabric preparation: Woven E-glass fabric is selected to the specified areal weight, weave pattern, and fibre sizing for compatibility with the epoxy resin system of each grade.
- Resin impregnation: Glass fabric plies are impregnated with epoxy resin formulated to the grade's specification — standard epoxy for G10/FR4, elevated-temperature epoxy for G11/FR5, with appropriate flame retardant additives where required (FR grades).
- Layup and stacking: Resin-impregnated fabric plies are stacked to the required thickness. Ply count and resin content are calculated to achieve the target density (1.9–2.0 g/cm³) and mechanical properties.
- Hot-press curing: The stacked assembly is placed in a hydraulic hot press where heat (120–180°C) and pressure consolidate the plies, drive out volatiles, and fully cure the epoxy resin — producing a dense, void-free laminate.
- Sheet cutting and surface finishing: Cured laminate panels are cut to standard or customer-specified sheet sizes, surface-finished, and inspected for thickness uniformity, surface quality, and edge condition.
- Quality verification: Each batch is tested for thickness, density, dielectric strength, and water absorption before release.
Standards & Compliance
- IEC 60893 — Thermosetting laminates for electrical purposes (international standard covering all grades)
- NEMA LI-1 — National Electrical Manufacturers Association industrial laminate standards (G10, G11, FR4, FR5 grade definitions)
- IS 3258 — Indian Standard for glass fibre reinforced laminates (EPGC 201, EPGC 202)
- UL 94 — Standard for flammability of plastic materials (V-0 rating for FR4, FR5 grades)
- IEC 60085 — Thermal classification of electrical insulation (Class F, Class H)
- IEC 60664 — Insulation coordination for equipment within low-voltage systems
Industries Served
- Power transformer manufacturing — G11/EPGC 202 spacers, phase barriers, insulation blocks
- Distribution transformer manufacturing — G10/FR4/EPGC 201 panel insulation
- Switchgear & control panel manufacturing — FR4/FR5 arc barriers, bus supports, phase separators
- Electric motor manufacturing — G11 slot wedges, end ring insulation
- Renewable energy (solar & wind) — inverter and generator insulation components
- Railways & traction — traction transformer insulation, rolling stock electrical systems
- PCB & electronics manufacturing — FR4 substrate for printed circuit boards
- Industrial electrical equipment — industrial drives, rectifiers, furnace transformers
Engineering Tools Suite
Calculate precise dielectric clearances, moisture resistance derating, and select the correct fiber glass laminate grade for your specific application voltage, temperature, and mechanical load requirements.
Frequently Asked Questions
Both G10 and G11 are glass cloth reinforced epoxy laminates with excellent dielectric properties, but they differ critically in thermal performance. G10 uses a standard epoxy resin and is rated for continuous service up to approximately 130°C (Class B). G11 uses a higher-performance epoxy formulation that retains full mechanical strength at temperatures up to 155°C (Class F) and beyond. G11 is the mandatory specification for transformer spacers, switchgear phase barriers, motor slot wedges, and any load-bearing insulation component exposed to sustained operating temperatures above 130°C. Using G10 in a G11-specified application risks mechanical softening and dimensional failure above 130°C.
G10 and FR4 have virtually identical mechanical and dielectric properties — both are glass cloth reinforced standard-temperature epoxy laminates. The single critical difference is flame retardancy. G10 does not carry a UL 94 flame retardancy rating. FR4 meets UL 94 V-0 (self-extinguishing within 10 seconds) through the addition of flame retardant chemistry to the epoxy resin. FR4 is the default specification wherever UL 94 V-0 compliance is required — switchgear panels, electrical enclosures, PCB fabrication. G10 may be specified where flame retardancy is explicitly not required and maximum electrical performance and machinability are the priority.
EPGC 201 and EPGC 202 are Indian Standard (IS 3258 / IEC 60893) designations for electrical grade glass cloth reinforced epoxy laminates. EPGC 201 is the general-purpose grade equivalent to G10/FR4 class — widely specified in Indian transformer and switchgear OEM technical drawings. EPGC 202 is the elevated-temperature grade equivalent to G11 class, with improved mechanical retention above 130°C. Both are manufactured and stocked by ACC Insulations and supplied with IS-compliant material certificates. If your drawing specifies EPGC 201 or EPGC 202, we supply the correct grade directly.
Yes. Electrical grade fiber glass laminates — G10, G11, FR4, FR5, and EPGC grades — are specifically designed for high-voltage electrical insulation. Their high dielectric strength (typically 20–30 kV/mm depending on thickness and grade), very low moisture absorption (20 mg), and stable electrical properties across operating temperature make them standard materials for transformer phase barriers, switchgear arc barriers, busbar insulation, HV terminal boards, and high-voltage bushing support components.
We supply fiber glass laminates from 0.1 mm to 150 mm thickness in all grades — G10, G11, FR4, FR5, EPGC 201, EPGC 202. Standard sheet lengths are 1000 mm and 1200 mm. We also offer in-house CNC machining and precision slitting to produce custom components and cut-to-size sheets to your exact dimensions. Custom lengths and widths are available on enquiry.
Yes — fiber glass laminates, particularly G10, G11, and FR4, machine exceptionally well using CNC routing, milling, drilling, and turning. ACC Insulations operates CNC machining equipment to produce custom insulation components directly from laminate sheets: phase barriers, slot wedges, terminal boards, arc chutes, bushing support plates, transformer spacers, and any other precision-profiled structural part. Components are machined to customer CAD drawings with tight dimensional tolerances. Please provide your drawing or part description for a quotation.
ACC Insulations' fiber glass laminates have a water absorption of 20 mg tested per IEC 60893 method D24/23 (24 hours immersion at 23°C). This low value is critical because moisture absorbed by insulation materials directly reduces dielectric strength — the more moisture, the lower the insulation's ability to withstand voltage. Glass epoxy laminates have much lower water absorption than phenolic paper laminates or pressboard, which means their dielectric strength remains stable across the full range of humidity conditions encountered in electrical equipment service, particularly in tropical and coastal environments.
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