Heat Shrink Boots, Caps

Part Number	Description / PDF	Quantity
CAP26 BK078 Alpha Wire	HEATSHRINK CAP 2:1 SR-PO BK	40
CAP27 BK078 Alpha Wire	HEATSHRINK CAP 2:1 SR-PO BK	2
CAP22 BK078 Alpha Wire	HEATSHRINK CAP 2:1 SR-PO	0
CAP25 BK078 Alpha Wire	HEATSHRINK CAP 2:1 SR-PO	8
CAP24 BK078 Alpha Wire	HEATSHRINK CAP 2:1 SR-PO	175
CAP23 BK078 Alpha Wire	HEATSHRINK CAP 2:1 SR-PO	39
CAP21 BK078 Alpha Wire	HEATSHRINK CAP 2:1 SR-PO	66

Heat Shrink Boots, Caps

1. Overview

Heat shrink boots and caps are thermoplastic tubular components designed to shrink when exposed to heat. They provide environmental sealing, mechanical protection, and strain relief for cables, wires, and connectors. These components play a critical role in modern electronics, automotive, aerospace, and industrial systems by ensuring reliable connections and preventing moisture ingress, abrasion, or vibration-induced failures.

2. Main Types and Functional Classification

Type	Functional Features	Application Examples
Single-Wall Tubing	General-purpose protection with moderate mechanical strength	Consumer electronics cable insulation
Double-Wall Tubing	Internal adhesive layer for enhanced sealing	Automotive under-hood wiring harnesses
High-Temperature Tubing	Rated for continuous operation >150 C	Aerospace engine compartment wiring
Anti-Static Tubing	Dissipates electrostatic charges (10^9-10^12 surface resistance)	Semiconductor manufacturing equipment
Marker Sleeves	Pre-printed or customizable identification markings	Industrial control panel wiring

3. Structure and Composition

Typical construction includes:

Base Material: Cross-linked polyolefin, PVC, or fluoropolymer
Adhesive Layer: Thermoplastic adhesive (for double-wall types)
Shrink Ratio: Standard 2:1 to advanced 4:1
Wall Thickness: 0.5-5.0mm depending on application
Color Options: Standard colors (red, blue, black) and custom variants

Manufacturing involves irradiation cross-linking followed by expansion at controlled temperatures.

4. Key Technical Parameters

Parameter	Typical Range	Significance
Shrink Temperature	80-200 C	Determines required heating equipment
Shrink Ratio	2:1 to 4:1	Affects dimensional adaptability
Tensile Strength	10-50 MPa	Indicates mechanical protection capability
Dielectric Strength	15-100 kV/mm	Critical for electrical insulation
Fluid Resistance	Oil/gasoline/coolant	Essential for harsh environments

5. Application Fields

Automotive: Engine wiring harnesses, battery connectors
Aerospace: Avionics cabling, hydraulic system protection
Telecommunications: Fiber optic splice protection
Industrial: Motor terminal covers, control cabinet wiring
Marine: Corrosion protection for underwater connectors

6. Leading Manufacturers and Products

Manufacturer	Key Products	Special Features
3M	EC2000 Series	RoHS compliant, 4:1 shrink ratio
TE Connectivity	Raychem SCL	Self-extinguishing UL94 rating
Alpha Wire	3135 Series	Low-smoke zero-halogen (LSZH)
Sumitomo Electric	Heaton H-8	High-temperature stability to 200 C

7. Selection Guidelines

Key considerations:

Environmental Factors: Operating temperature range (-55 C to +175 C typical)
Dimensional Fit: Pre-shrunk ID should be 20-30% larger than substrate
Regulatory Compliance: UL, CSA, MIL-SPEC certifications
Installation Method: Match to heat gun, oven, or automatic system capabilities
Chemical Resistance: Required for exposure to fuels, solvents, or cleaning agents

Case Study: Automotive under-hood application selected 2:1 double-wall tubing with 150 C rating for engine control unit (ECU) harness protection.

8. Industry Trends

Material Innovation: Development of bio-based and recyclable polymers
Miniaturization: Ultra-thin wall designs for high-density electronics
Smart Materials: Conductive inks for integrated circuit diagnostics
Regulatory Drivers: Increasing RoHS/REACH restrictions on flame retardants
Automation Compatibility: Pre-cut lengths with laser-coded markings