Development of Fire-resistant PBT Material Offering Excellent Glow Wire Characteristics

TOKYO -

Polyplastics Co., Ltd. and WinTech Polymer Ltd. have jointly succeeded in developing DURANEX(R) 330GW, a fire-resistant PBT material which is the first PBT resin in the world to have glow wire characteristics complying with all thicknesses recommended by a new IEC standard (Notes 1-3), by combining new fire resistance technology with our proprietary advanced compound technology. This newly developed DURANEX(R) 330GW eliminates the need for customers to conduct a glow wire ignition test (GWT), irrespective of the wall thickness or shapes of parts, allowing for both cost reductions and more efficient development.

1. Background

Underwriters Laboratories Inc.’s UL94 standard defining the fire resistance of electronic parts is well known. This standard stipulates that test pieces be brought into direct contact with a flame from a burner to evaluate combustibility. However, because fires can be caused by both direct flames and electrical ignition, demand for fire-resistant safety with particular emphasis on the causes of electrical ignition of electric and electronic parts has grown sharply recently.

Accordingly, the fire resistance standard of the International Electrotechnical Commission (IEC) was made more stringent and extensively revised in 2001. This fire resistance standard is extremely strict, and requires materials that virtually do not ignite. In response to the revision of this safety standard, the demand for U.S. and European home electronics manufacturers to use components with glow wire resistance has risen sharply. However, as long as conventional fire resistance technology has been adopted, PBT (polybutylene terephthalate) has been considered incapable of complying with this standard.

2. Overview

We have succeeded in developing a fire-resistant PBT material named DURANEX(R) 330GW offering exceptional glow wire characteristics by combining our core advanced fire resistance technology with the latest advances in this area and sophisticated compound technology (Note 4). Using DURANEX(R) 330GW will exempt parts made of it from a glow wire ignition test (GWT) and impose no restrictions on the wall thicknesses of parts, irrespective of their shapes.

3. Future Prospect

Today, the market keeps a stricter eye on the safety of electrical equipment, and an increasing number of home electronics manufacturers are reviewing their internal fire-resistant safety standards with reference to the IEC’s revised safety standards. The Japanese market may, therefore, also require more stringent fire resistance standards, and demand for materials that afford excellent glow wire characteristics is expected to increase. We are determined to deal with such need in a proper manner and contribute to the prevention of fires involving electric and electronic parts attributable to electrical ignition.

Table 1: Characteristics of DURANEX(R) 330GW Test method Newly developed grade Item ISO Unit 330GW Strengthened by GF30% Density 1183 g/cm3 1.76 Tensile strength 527-1, 2 MPa 87 Tensile rupture strain 527-1, 2 % 0.9 Bending strength 178 MPa 130 Elastic modulus in flexture 178 MPa 11,000 Charpy impact strength (with notch) 179-1 kJ/m2 5.2 Deflection temperature under load (1.8 MPa) 75-1, 2 degrees C 208 Combustibility (UL94) - V-0 (0.32mm) degrees C 0.75mm more than 775 GWIT (*) (IEC 60695-2-13) 1.5mm more than 775 3.0mm more than 775 CTI (IEC 60112) V more than 250 (*): Test value by VDE, a German certification institution (natural color)

Note 1: First in the world

The glow wire ignition temperature (GWIT) value of DURANEX(R) 330GW, in black and natural color, exceeded 775 degrees C at all recommended thicknesses (0.75 mm, 1.5 mm, 3.0 mm) in tests conducted by VDE, a German certification institution. To the best of our knowledge, as of August 31, 2009, 330GW is the first PBT resin to achieve this in the world.

Note 2: New IEC standard

The new IEC standard is the fourth edition of the IEC60335-1 concerning the safety of domestic appliances (white goods). This standard requires that components in domestic appliances that operate unattended apply the following glow wire characteristics to parts made of insulating materials, which support connections carrying a current in excess of 0.2 A in regular operation, and parts made of insulating materials located within 3 mm of connections: In terms of their glow wire characteristics, the glow wire flammability index (GWFI) and glow wire ignition temperature (GWIT) of the materials comprising these parts shall exceed 850 degrees C and 775 degrees C, respectively. One of the features of this standard is that parts and products made of materials fulfilling this requirement are exempted from a glow wire ignition test (GWT). As a result, market demand for materials with an exceptional GWIT rating is extremely high.

Note 3: Glow wire test

The method for testing the GWIT is specified in IEC60695-2-13. The GWIT is represented by the value calculated by adding 25 degrees C to the maximum temperature (in steps of 25 degrees C) at which the tested part does not ignite when it is kept in contact with a glow wire (hot rod) for 30 seconds. Three thicknesses are recommended for test pieces: 0.75 mm, 1.5 mm, and 3.0 mm. The wall thickness applicable to the final products is restricted to the thickness of the test piece that passed. This means that if a material that passed all of the three recommended thicknesses is used, no restriction will be imposed on the wall thicknesses of parts, and parts made of the material will be exempted from glow wire ignition tests (GWT), irrespective of the product’s shape.

Note 4: Development of PBT resin with exceptional glow wire characteristics

In tests conducted by VDE, a German certification institution, DURANEX(R) 330GW fulfilled the GWIT value of 775 degrees C required by IEC60335-1 at all of the recommended thicknesses of 0.75 mm, 1.5 mm, and 3.0 mm. Electronic components, including relays, switches, and connectors, made of DURANEX(R) 330GW will, therefore, be free of restrictions on the wall thicknesses of the final products and exempted from glow wire ignition tests (GWT) by VDE, irrespective of the shape of the product, while still complying with the fire resistance requirements of IEC60335-1. The comparative tracking index (CTI) of this material is remarkable at over 250 V, which enables it to meet electronic fire safety requirements, which have been made more stringent recently, to a large degree. Additionally, DURANEX(R) 330GW achieves V-0 at a thickness of 0.32 mm in connection with the fire resistance requirements of UL94.

About Polyplastics Co., Ltd. President: Noboru Goto, Head office: Minato-ku, Tokyo, Japan About WinTech Polymer Ltd. President: Ryuichi Sekita Head office: Minato-ku, Tokyo, Japan Contact: Kei Ibano Administration Department Polyplastics Co., Ltd. Tel: +81-3-6711-8600 E-mail : 330GW@polyplastics.com URL: www.polyplastics.com

Source: Polyplastics Co., Ltd.

Kei Ibano, Administration Department, Polyplastics Co., Ltd., +81-3-6711-8600, 330GW at polyplastics.com