Steel-lined plastic pipes have the aging life of the plastic. They have a low coefficient of friction among solid materials. They possess a small surface tension among solid materials, not adhering to any substance. They exhibit good mechanical toughness; even at a temperature drop to -196°C, they can maintain a 5% elongation rate. They show inertness to most chemicals and solvents, resistant to strong acids and alkalis, water, and various organic solvents. They have physiological inertness, and can be implanted in the body as artificial blood vessels and organs for a long time without any adverse reactions.