Machine Design

Nylon for neophytes

Nylon 12 heat-shrinkable electrical connectors handle tough environments their weaker cousins can't.

Butt splice connectors from Tyco (, made of nylon 12, resist harsh environmental factors such as oil, water, and high temperatures.
Terminals and splices made from heat-shrinkable polyethylene work well in less-demanding applications.
The graph shows that nylon 12 is less hydroscopic than nylon 6 and 6/6.
Nylon 12 resists chemicals such as battery acid better than other nylons.
Nylon 12 and HDPE tubing were immersed in various fluids and the tensile strength tested afterwards. Nylon 12 showed higher tensile strength both before and after immersion. Plus, in some cases, strength actually increased.

Leslie Kao
Product Manager
Tyco Electronics
Menlo Park, Calif.

Electrical crimp connectors such as butt splices and terminals are available in a range of different constructions and materials. These differences can lead to significant variation in the performance of electrical wire harnesses, particularly when connectors must withstand harsh environmental conditions such as temperature extremes, immersion in fluids such as coolants, oil, and water, and exposure to ultraviolet radiation.

Results of several studies show that nylon 12 outperforms materials such as nylon 6, 6/6, and high-density polyethylene (HDPE) tubing.

Tests show that heat-shrinkable nylon 12 outperforms other materials in critical properties. For instance, many preinsulated crimp splices are made with nylon 6 or 6/6. Testing against nylon 12 showed some interesting results. For example, nylon materials have long had a reputation of being hydroscopic and weak after exposure to chemicals. This is true for nylon 6 and 6/6 but not for nylon 12 which has better moisture and chemical-resistance properties.

When compared with HDPE tubing, nylon 12 comes out ahead in several areas including tensile strength after immersion in various fluids, cut through, and scrape abrasions.

The dielectric strength of both nylon 12 and polyethylene tubing exceeds 1,000 V/mil, even after exposure to many fluids. The insulation sleeve of the crimp connectors is typically greater than 10 mils thick after installation. Therefore, butt splices made from either nylon or HDPE easily meet UL 486D dielectric voltage-withstand requirements of no breakdown at 2,200 Vac.

Nylon 12 also does a good job protecting electrical connections in harsh environments. When cross-linked and stabilized, nylon 12 becomes heat shrinkable. When combined with an integral adhesive-sealing system, heat-shrinkable nylon 12 crimp connectors seal and protect against water, automotive fluids, and mechanical abuse, withstanding temperatures to 125°C.

Crimp connectors with heat-shrinkable insulation are similar to their preinsulated nonheat-shrinkable counterparts. The difference is that when the heat-shrinkable insulation sleeve is heated after crimping, the sleeve shrinks down around the connection and provides both strain relief and environment-resistant sealing.

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