Demand for rubber cable compounds remains strong

RAVENNA, Italy—While demand for rubber cable compounds is growing or at least stable in most world regions, the sector is being held back by a lack of technical input from cable manufacturers, said Andrea Galanti, general director of Mixer SpA, based in Ravenna.

Mixer began manufacturing cable compounds in 1996 with the goal of meeting specific requirements of the wire and cable industry. Following sustained growth, the company has established itself as a global supplier of rubber compounds and flame-retardant compounds for the industry.

With an overall production capacity of 30 kilotons per year, Mixer's plant operates a black production line for jacket compounds, a white line for insulation/bedding compounds and a backup line. Equipment includes internal mixers and strainer extruders that can manufacture compounds in granule form.

Output from the northern Italy site encompasses insulation and jacketing compounds for low voltage and medium voltage power cables—including those produced using peroxide and irradiation crosslinking—as well as some thermoplastics materials.

Mixer's market profile is highest in Europe, where it claims to be the largest supplier of flexible cable, rubber cable, power cable and flame-retardant cable compounds in the Italian market. It also supplies a major part of the Spanish market.

Looking at the global market, Galanti describes demand as “stable in the European Union but growing in China, Middle East and South America.” He added that price and customer support are the “traditional key” to winning an increased market share in each region.

Asked about the main barriers to progress in the global cable market, the Mixer executive said, “Many (companies) have old plants or want to use improper machinery derived from PVC or XLPE technology. The main difficulty in this task is the communication with the customers. Most of them do not want to share information and knowledge of their activity. They are just interested in receiving a ready-to-use solution that will not involve them in any development.”

Galanti said rubber cables and compounds are becoming more of a niche market with limited knowledge. “Only a strong cooperation between customers and suppliers will lead to success (in) overcoming other well-known technologies,” he said.

In terms of materials, the Mixer executive listed “long-term stabilized rubber in pellets form with updated green composition” as technologies most in demand by the market today.

Among its recent developments, Mixer has introduced a lead-free EPDM compound for medium voltage cables, which is said to match the electrical and physical properties of leaded compounds. Based on a synergistic mixture of organic and inorganic additives with enhanced ion-scavenging properties, the company said it allows easy dispersion and compatibility with olefinic polymer matrices.

Lead chemicals are used as stabilizers in today's commercially available EPDM compounds for MV insulations, particularly for water resistance and long-lasting performance. In the EU, however, red lead oxide is listed in REACH as an SVHC (substances of very high concern), forcing MV cable producers to substitute the material with non-leaded alternatives.

Among some interesting recent developments at Teknor Apex Co. is a new PVC elastomer compound for cable jacketing, particularly for use in extreme low-temperature environments. Teknor Apex claims the Flexalloy 9614-73 grade can withstand frigid outdoor and rugged industrial conditions, while providing enhanced flexibility and flame performance.

The 73 Shore A compound is UV-stabilized and exhibits a brittle point of -65°C or below, the company said. It is designed to pass the UL 1685 Vertical Tray test and Canadian Standards Association's FT-4 vertical tray flame test.

“There is a gap in the market for PVC jacketing for cable compounds that meet stringent flammability standards, but at the same time can have the flexibility and a very low brittle point,” said Michael Roberts, industry manager for the vinyl division of Teknor Apex.

Creating this compound was difficult because the target properties work against each other; typically, the more flame retardant a compound is, the more brittle the product becomes, and the softer the material is, the more flammable it is.

Balancing those three properties, Roberts said, offers cable makers a very soft, flexible compound that can be used in all sorts of challenging applications, such as in the colder regions of Canada. This type of performance, he said, typically requires polymers that cost 50 to 300 percent more than a PVC-based elastomer.

The shipbuilding and off-shore oil and gas sectors are at the forefront in requiring halogen-free, flame-retardant cable sheathing materials that offer flexibility and oil resistance—even in Arctic conditions.

According to Lanxess A.G., this trend is driving demand for blends of hydrogenated nitrile (HNBR) and ethylene vinyl acetate (EVM) rubbers, which also offer enhanced levels of resistance to oils, lubricating greases and drilling chemicals.

“Engineers today demand cable sheathing materials that remain flexible at temperatures below minus 40°C,” said Joerg Stumbaum, technical marketing manager at Lanxess' high performance elastomers business. “There are various materials that can break through this mark. However, if there are also special safety requirements, then 50-50 blends of our Levapren (EVM) and Therban HNBR elastomer ... not only remain flexible at temperatures well below minus 40°C, they also exhibit high oil resistance and outstanding flame-retardant properties.”

“Due to their high polarity, Therban/-Levapren blends can incorporate large quantities of inorganic halogen-free fillers, such as aluminum hydroxide,” Stumbaum added. “Should an external fire ignite these flame-retardant cable sheathings, only limited amounts of smoke will develop, which is important for keeping evacuation routes visible as long as possible.”

Fire safety is the focus for specialty materials distributor Velox GmbH, which has extended its partnership with the Tolsa Group, a Spanish supplier of flame retardant and thermal insulation synergists.

The Hamburg, Germany-based firm will supply Tolsa's Adins Clay and Adins Fireproof flame retardant synergists, in Europe. The inorganic halogen-free products boost char formation during combustion and protect polymers from further fire propagation, the company said.

The additives, said Velox, combine a high surface area and special morphology with a tailored functionality for wire and cable as well as electronics applications.

Back in the polymers arena, APS Elastomers, based in Romulus, Mich., has added an extrusion grade for flat conductor network cables to its Viprene range of thermoplastic vulcanizate elastomers. These cables comprise foil-type copper strips of varying widths that are electrically insulated by a plastics layer and bound together into a single unit. They are used in applications requiring constant flexing and in areas “previously considered unfeasible or cumbersome,” such as exterior mirrors, trunk and hood lids, roof liners, doors and rotating arms.

German rubber technology company Melos has produced a "cable compound finder' app, to help users identify the most suitable compound for their specific cable requirements. The app has four stages of product groups: categories and applications; standards and features; technical data sheets and inquiry list; and create your compound.

Users can choose between sheathing, insulation and bedding materials and set filters to choose compounds for eight different applications while defining any required standard.