IR

Introduction to IR Rubber

IR, or Polyisoprene Rubber, is a synthetic polymer produced by the polymerization of isoprene monomers, resulting in a structure predominantly composed of cis-1,4-polyisoprene (typically 92-98% cis content), similar to natural rubber. It was developed in the 1950s as a synthetic alternative to NR to address supply shortages and inconsistencies in natural latex. IR is synthesized using catalysts like Ziegler-Natta or lithium-based systems for high cis content, ensuring properties akin to NR. It is available in grades such as 96% cis-IR and 92% cis-IR, and can be compounded with fillers like carbon black, silica, oils, and antioxidants. Unlike NR, IR is free of proteins and impurities, making it hypoallergenic and more uniform in processing. It is often used where NR's performance is desired but with better control over quality.

 

Characteristics of IR Rubber

IR shares many properties with NR but offers improved low-temperature performance and purity. Here are its key characteristics:

  1. Mechanical Properties: IR has excellent tensile strength (15-25 MPa in vulcanized form), high elongation at break (400-700%), and superior tear and abrasion resistance. It provides outstanding resilience and low hysteresis, similar to NR, with good flex fatigue resistance. However, it may have slightly lower green strength than NR, requiring adjustments in formulations.
  2. Chemical Resistance: Fair resistance to water, alcohols, dilute acids, and alkalis, but poor resistance to oils, hydrocarbons, ozone, and oxidizing agents, leading to swelling or cracking. It requires protective additives like antiozonants for outdoor use, similar to NR.
  3. Thermal Properties: Effective operating range from -60°C to +80°C (up to +100°C short-term), with better low-temperature flexibility than NR due to reduced crystallization. It maintains elasticity in cold conditions but softens at high temperatures without stabilizers.
  4. Durability and Aging: Good resistance to fatigue and dynamic stress, but susceptible to atmospheric aging, UV, and ozone without additives. It has low gas permeability and excellent adhesion to substrates. As a white material, it allows for light-colored compounds.
  5. Processing and Cost: Easy to process via milling, extrusion, calendering, and molding, with consistent quality due to synthetic production. It is more expensive than NR (due to manufacturing costs) but offers value in applications requiring purity and uniformity.
  6. Other Properties: Hypoallergenic (no latex proteins), low specific gravity (0.91-0.93), and good electrical insulation. It can be vulcanized with sulfur or peroxides. IR has high building tack and hot tear strength, making it suitable for molding.

In formulations, IR is often blended with NR or other synthetics to optimize cost and performance, such as improving low-temperature properties.

 

Applications of IR Rubber

IR's similarity to NR combined with its purity makes it versatile for high-performance and sensitive applications:

  1. Medical and Healthcare: Used in surgical gloves, catheters, stoppers, and medical tubing due to its hypoallergenic nature and elasticity, avoiding NR's allergy risks.
  2. Automotive and Tires: In tire treads, sidewalls, and inner liners for its resilience and low heat build-up, often blended with NR in high-performance tires.
  3. Industrial Products: Conveyor belts, hoses, seals, and vibration mounts for durability and flex resistance.
  4. Consumer Goods: Footwear soles, adhesives, tapes, and sports equipment like golf balls for elasticity and comfort.
  5. Electronics and Insulation: Wire coatings and seals where electrical insulation and flexibility are needed.
  6. Other Uses: Food-contact applications (FDA-compliant grades), toys, and light-colored rubber products like erasers or mats.

IR production emphasizes sustainability, with bio-based isoprene options emerging. It's a key material where NR-like performance is required without natural impurities.