EN 60371-3-4:1995

Specification for insulating materials based on mica - Part 3: Specifications for individual materials - Sheet 4: Polyester film-backed mica paper with a B-stage epoxy resin binder

Gives requirements for materials made by combining mica paper with a single polyester film and impregnating the mica paper with an epoxy resin. The material is supplied in a flexible state for final cure after application in the form of sheets or rolls.

Bestimmung für Glimmererzeugnisse für elektrotechnische Zwecke - Teil 3: Bestimmungen für einzelne Materialien - Blatt 4: Polyesterfolienverstärktes Glimmerpapier mit Expoxidharz-Bindemittel im B-Zustand

Spécification pour les matériaux isolants à base de mica - Partie 3: Spécifications pour matériaux particuliers - Feuille 4: Papier de mica renforcé d'un film polyester avec un agglomérant en résine époxyde à l'état B

Fournit les prescriptions concernant les matériaux obtenus en combinant du papier de mica avec un seul film de polyester et en imprégnant le papier de mica avec une résine époxyde. Le matériau est fourni pour traitement de durcissement après application, sous forme de feuilles ou de rouleaux.

Specifikacija za izolacijske materiale na temelju sljude – 3. del: Specifikacije za posamezne materiale – 4. list: Sljudni papir na poliestrski foliji z vezivom iz epoksidne smole B (IEC 60371-3-4:1992)

General Information

• Status: Published
• Publication Date: 14-Jun-1995
• Withdrawal Date: 14-Dec-1995
• ICS: 29.040.20 - Insulating gases
• Technical Committee: CLC/SR 15 - Insulating materials
• Drafting Committee: IEC/TC 15 - IEC_TC_15
• Parallel Committee: IEC/SC 15C - IEC_SC_15C
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 15-Jun-1995
• Completion Date: 15-Jun-1995
• Ref Project: SIST EN 60371-3-4:1998 - Specification for insulating materials based on mica -- Part 3: Specifications for individual materials -- Sheet 4: Polyester film-backed mica paper with a B-stage epoxy resin binder

Relations

• Amended By: EN 60371-3-4:1995/A1:2006 - Specification for insulating materials based on mica - Part 3: Specifications for individual materials - Sheet 4: Polyester film-backed mica paper with a B-stage epoxy resin binder
• Effective Date: 28-Jan-2023

Overview

EN 60371-3-4:1995 (CLC adoption of IEC 60371-3-4) specifies requirements for polyester film-backed mica paper impregnated with a B‑stage epoxy resin binder. The standard covers flexible electrical insulating materials supplied as sheets or rolls, with the resin in the B‑stage so final cure occurs after application. Nominal material thicknesses covered fall in the range 0.16 mm to 0.23 mm, and products are described by codes such as F23/M150/R54 (film/mica/resin).

Keywords: EN 60371-3-4, polyester film-backed mica paper, B-stage epoxy, mica insulating materials, electrical insulation standard.

Key topics and technical requirements

• Material composition and designation
  • Defines descriptive codes (film thickness, mica content, resin content) and example type numbering (e.g., IEC 371-3-4: type 4.1.01).
  • Typical film thickness options: ~23 µm (32 g/m²) and ~50 µm (70 g/m²).
• Raw material references
  • Mica paper must meet IEC 371-3-2 requirements.
  • Polyester backing (PET) must comply with IEC 674-3-2.
  • Epoxy resin system is not prescriptive but must enable the finished material to meet the specification.
• As‑received requirements
  • Uniform, defect‑free surfaces; roll handling/unwinding performance.
  • Unwinding tension limits: ≤25 N/10 mm for 23 µm film, ≤45 N/10 mm for 50 µm film.
  • Preferred widths listed (10–50 mm), core diameters (25, 40, 55 or 76 mm), and limits on joins in consignments.
  • Minimum resin flow 10% at 160 °C ±2 °C (test method referenced to IEC 371-2).
• After‑curing performance
  • Flexural strength ≥ 150 N/mm² at 23 °C and ≥ 100 N/mm² at 155 °C.
  • Elastic modulus ≥ 30 kN/mm².
  • Electric strength ≥ 50 kV/mm (test per IEC 243-1 / IEC 371-2).
  • Dissipation factor limits: 30 °C ≤0.02; 130 °C ≤0.07; 155 °C ≤0.20.
  • Thermal endurance (temperature index) ≥ 155 °C.

Applications and users

• Used by manufacturers and specifiers of electrical insulation systems for transformers, rotating machines, switchgear, capacitors, and other high‑reliability electrical components that require mica‑based insulating materials.
• Relevant to: product engineers, materials and quality control teams, procurement specialists, test laboratories, and regulatory/compliance officers specifying mica‑based insulation.
• Practical value: ensures consistent composition, handling, mechanical, dielectric and thermal performance for materials intended for in‑service final curing.

Related standards

• IEC/EN 371-2 (Methods of test for mica-based insulating materials)
• IEC/EN 371-3-2 (Mica paper)
• IEC/EN 674-3-2 (PET film for electrical purposes)
• IEC 243-1 (Electric strength test methods)

This specification helps suppliers and users define, test and accept polyester film‑backed mica paper with a B‑stage epoxy binder to meet reliable electrical and thermal performance in insulating applications.

Standards Content (Sample)

SLOVENSKI STANDARD
01-junij-1998
Specifikacija za izolacijske materiale na temelju sljude – 3. del: Specifikacije za
posamezne materiale – 4. list: Sljudni papir na poliestrski foliji z vezivom iz
epoksidne smole B (IEC 60371-3-4:1992)
Specification for insulating materials based on mica -- Part 3: Specifications for individual
materials -- Sheet 4: Polyester film-backed mica paper with a B-stage epoxy resin binder
Bestimmung für Glimmererzeugnisse für elektrotechnische Zwecke -- Teil 3:
Bestimmungen für einzelne Materialien -- Blatt 4: Polyesterfolienverstärktes
Glimmerpapier mit Expoxidharz-Bindemittel im B-Zustand
Spécification pour les matériaux isolants à base de mica -- Partie 3: Spécifications pour
matériaux particuliers -- Feuille 4: Papier de mica renforcé d'un film polyester avec un
agglomérant en résine époxyde à l'état B
Ta slovenski standard je istoveten z: EN 60371-3-4:1995
ICS:
29.035.50 Materiali na podlagi sljude Mica based materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME CEI
INTERNATIONALE IEC
60371-3-4
INTERNATIONAL
Première
édition
STAN DARD
First edition
1992-10
Spécification pour
les matériaux isolants
à base de mica
Troisième partie:
Spécifications pour matériaux particuliers
Feuille 4: Papier de mica renforcé d'un film
de polyester avec un agglomérant en
résine époxyde à l'état B
Specification for insulating materials
based on mica
Part 3:
Specifications for individual materials
Sheet 4: Ployester film-backed mica paper
with a B
-stage epoxy resin binder
© IEC 1992
Droits de reproduction réservés — Copyright - all rights reserved
Aucune partie de
cette publication ne peut être reproduite ni No part of this publication may be reproduced or utilized in
utilisée
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procédé, électronique ou mécanique, y compris la photo- including photocopying and microfilm, without permission in
copie
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Telefax: [phone] e-mail: [e-mail] IEC web site http: //www.iec.ch
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EN S
CON T T
Page
FOREWORD 5
INTRODUCTION 7
Clause
1 Scope 9
2 Normative references 9
3 Designation 9
4 Requirements: raw materials 11
5 Requirements: compositions and tolerances 13
6 Requirement for material (as received) 13
7 Requirements for material after curing 15
8 Packing 17
371-3-4 ©IEC - 5 -
INTERNATIONAL ELECTROTECHNICAL COMMISSION
SPECIFICATION FOR INSULATING MATERIALS
BASED ON MICA
Part 3: Specifications for individual materials
Sheet 4: Polyester film-backed mica paper
with a B-stage epoxy resin binder
FOREWORD
1)
The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on
which all the National Committees having a special interest therein are represented, express, as nearly as
possible, an international consensus of opinion on the subjects dealt with.
2)
They have the form of recommendations for international use and they are accepted by the National
Committees in that sense.
3)
In order to promote international unification, the IEC expresses the wish that all National Committees
should adopt the text of the IEC recommendation for their national rules in so far as national conditions will
permit. Any divergence between the IEC recommendation and the corresponding national rules should, as
far as possible, be clearly indicated in the latter.
4)
The IEC not laid down any procedure concerning marking as an indication of approval and has no
responsibility when an item of equipment is declared to comply with one of its recommendations.
This International Standard has been prepared by Sub-Committee 15C: Specifications,
of IEC Technical Committee No. 15: Insulating materials.
The text of this standard is based on the following documents:
DIS Report on Voting
15C(CO)291 15C(CO)321
Full information on the voting for the approval of this standard can be found in the Voting
Report indicated in the above table.

371-3-4 ©IEC - 7 -
INTRODUCTION
This International Standard is one of a series which deals with insulating materials built up
from mica splittings or mica paper.
The series consists of the three following pa
rts:
Pa rt 1: Definitions and general requirements (IEC 371-1).
Part
2: Methods of test (IEC 371-2).
Part 3: Specifications for individual materials (IEC 371-3).
This standard contains one of the sheets comprising pa 3, as follows:
rt
Sheet 4: Polyester film-backed mica paper with a B-stage epoxy resin binder.

371-3-4 ©IEC - 9 -
SPECIFICATION FOR INSULATING MATERIALS
BASED ON MICA
Part 3: Specifications for individual materials
Sheet 4: Polyester film-backed mica paper
with a B-stage epoxy resin binder
1 Scope
This International Standard gives requirements for electrical insulating materials made by
combining mica paper with a single polyester film and impregnating the mica paper with an
epoxy resin. The material is supplied in a flexible state with the resin in the B-stage for
final cure after application. It may be supplied in the form of sheets or rolls.
The specification covers material having nominal thickness from 0,16 mm to 0,23 mm.
2 Normative references
The following normative documents contain provisions which, through reference in this
text, constitute provisions of this International Standard. At the time of publication, the
editions indicated were valid. All normative documents are subject to revision, and pa rties
to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated
below. Members of IEC and ISO maintain registers of currently valid International
Standards.
IEC 243-1: 1988, Methods of test for electric strength of solid insulating materials - Part 1:
Tests at power frequencies.
IEC 371-2: 1987, Specification for insulating materials based on mica - Part 2: Methods of
test.
IEC 371-3-2: 1991,
Specification for insulating materials based on mica - Pa rt 3:
Specifications for individual materials - Sheet 2: Mica paper.
IEC 674-3-2: 1992,
Specification for plastic films for electrical purposes - Part 3:
Specifications for individual materials - Sheet 2: Requirements for balanced biaxially
oriented polyethylene terephthalate (PET) film used for electrical insulation.
3 Designation
When ordering materials to this specification only the specification and type numbers need
be quoted (see table 1).
Example: IEC 371-3-4: type 4.1.01
...