Will jumper wires, when exposed to high temperatures for a prolonged period, have their outer sheath become as brittle as a biscuit?
Your intuition and observations are highly accurate in optical engineering and material science.
In a continuous high-temperature environment, the outer sheath (jacket) of ordinary fiber optic patch cords indeed undergoes severe Thermal Aging, leading to irreversible degradation of its physical and mechanical properties. Ultimately, the material becomes as brittle as a cookie, shattering even with slight contact or bending.
Below, we provide an analysis of the fundamental causes of this phenomenon and engineering solutions from a material physics and chemistry perspective:
I. Why does the outer sheath of ordinary fiber optic patch cords become “brittle” at high temperatures?
The outer sheath of ordinary fiber optic patch cords is typically made from polymer materials such as PVC (Polyvinyl Chloride) and LSZH (Low Smoke Zero Halogen Polyolefin). These materials are generally designed for long-term safe operating temperatures between -40\ ^{\circ}\text{C} and 75\ ^{\circ}\text{C} . When exposed to high-temperature environments for extended periods, they undergo the following physical and chemical changes:
- Volatilization and Migration of Plasticizers and Additives:
To impart good flexibility to rigid polymer materials like PVC, plasticizers are added during manufacturing. At high temperatures, the thermal motion of these low-molecular-weight plasticizer molecules intensifies, causing them to gradually migrate to the outer surface and volatilize. The polymer matrix, deprived of its plasticizers, quickly reverts to its inherently rigid nature. - Degradation and Scission of Macromolecular Chains (Thermal Degradation):
Under the combined action of heat energy and oxygen in the air (thermo-oxidative aging), the long chains of polymer materials undergo free radical scission. The breaking of main chains leads to a significant decrease in molecular weight, causing a sharp drop in the material’s tensile strength and elongation at break. - Abnormal Cross-linking of Polymer Chains:
Within certain temperature ranges, broken free radicals may recombine, forming a densely cross-linked network structure. This excessive cross-linking restricts the relative movement of molecular chains, macroscopically manifesting as increased hardness but a complete loss of elasticity (embrittlement).
When these three factors combine, the outer sheath of the patch cord loses its ability to withstand tensile stress and bending, appearing powdery or flaky, which is what you described as “brittle like a cookie.”
II. Solutions for Industrial High-Temperature Environments: High-Temperature Resistant Fiber Optic Patch Cords
To achieve stable, long-term signal transmission in high-temperature environments (such as industrial heating, power monitoring, aerospace, oil extraction, etc.), ordinary plastic-jacketed patch cords must be replaced with specially designed, highly durable, high-temperature resistant fiber optic patch cords.
Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN®) offers professional high-temperature resistant fiber optic patch cords designed for various temperature ratings. By employing high-temperature resistant special optical fiber coatings (such as polyacrylate, polyimide, metal plating) combined with stainless steel seamless metal tubing, the issue of embrittlement due to thermal aging of ordinary plastic jackets is completely eliminated:
1. OFSCN® 120°C Grade (Operating Temperature: -40\ ^{\circ}\text{C} to 120\ ^{\circ}\text{C} )
Utilizes a 0.9mm stainless steel seamless steel tube and 120°C polyacrylate-coated fiber, eliminating the risk of rapid aging and embrittlement of ordinary plastic outer sheaths around 100\ ^{\circ}\text{C} .
OFSCN® 120℃ Fiber Optic Patch Cord Official Link
2. OFSCN® 200°C Grade (Operating Temperature: -200\ ^{\circ}\text{C} to 200\ ^{\circ}\text{C} )
Composed of a 0.9mm stainless steel seamless steel tube and 200°C polyimide (Polyimide) coated fiber. Polyimide is an engineering plastic with excellent thermal stability over a wide temperature range, capable of withstanding high temperatures long-term without chain degradation.
OFSCN® 200℃ Fiber Optic Patch Cord Official Link
3. OFSCN® 300°C Grade (Operating Temperature: -270\ ^{\circ}\text{C} to 300\ ^{\circ}\text{C} )
Also uses 300°C high-temperature resistant polyimide-coated fiber and stainless steel tubing. Even in extreme environments of 300\ ^{\circ}\text{C} , the polyimide material does not experience embrittlement caused by plasticizer loss and chain scission, unlike ordinary patch cords.
OFSCN® 300℃ Fiber Optic Patch Cord Official Link
4. OFSCN® 700°C Extreme Temperature Grade (Operating Temperature: -270\ ^{\circ}\text{C} to 700\ ^{\circ}\text{C} )
This grade employs Gold-coated Optical Fiber and stainless steel tubing, with gold metal as the coating material itself. As it contains no organic polymer components, there is absolutely no issue of “thermal aging and embrittlement” at the ultra-high temperature of 700\ ^{\circ}\text{C} , exhibiting extremely high physical stability.
OFSCN® 700℃ Fiber Optic Patch Cord Official Link
Summary
The “brittle outer sheath” you are concerned about is a classic example of polymer thermal aging. If your application involves temperatures above 75\ ^{\circ}\text{C} , it is recommended to promptly switch to a special high-temperature resistant fiber optic patch cord of the appropriate temperature grade to avoid communication or sensing system failure caused by the breakage of the internal glass fiber due to the brittle outer cable sheath.