What Are the Specific Requirements for PTFE High-Temperature Fabric to Withstand the Temperature and Pressure Conditions of Photovoltaic Module Lamination?

In photovoltaic (PV) module lamination processes, PTFE high-temperature fabric must simultaneously withstand the combined action of high temperature, high pressure, and vacuum — while also delivering non-stick, breathable, and dimensional stability performance. The following details the specific requirements across four dimensions: temperature resistance, pressure resistance, surface performance, and structural stability.

Ⅰ. Temperature Resistance Requirements

Standard Process Temperature Range
PV lamination processes typically operate within 140–165°C (encapsulant type-dependent: standard EVA approximately 150°C; POE encapsulants approximately 155–160°C; some bifacial modules may reach 165°C).

Performance Requirements Under Rated Temperature:

• Long-term continuous operating temperature ≥ 200°C (requiring a ≥ 35°C safety margin above process temperature to prevent degradation)
• PTFE fabric must complete ≥ 8,000 lamination cycles at 150°C without weight loss, strength degradation, or deformation — verifiable via oven isothermal aging test (150°C × 1,000h: tensile strength retention ≥ 85%)
• Zero adhesive residue migration to module surfaces or laminator heating plates at operating temperature

Ⅱ. Pressure Resistance Requirements

Lamination Pressure Parameters
Laminator pressure range: typically 50–150 kPa (varying by module type, encapsulant, and laminator model); maximum pressure ≤ 200 kPa in some high-performance laminators.

Performance Requirements Under Rated Pressure:

• Under 150 kPa pressure: fabric thickness compression rate ≤ 8% (ensuring uniform pressure transmission to the module); no localized pressure concentration
• Under cyclic pressure (50–150 kPa, 8,000+ cycles): tensile strength reduction ≤ 15%; no fatigue cracking, delamination, or fiber breakage
• Surface flatness: under pressure, surface flatness deviation ≤ 0.1 mm/m to prevent localized over-pressure causing cell micro-cracking

Ⅲ. Combined Temperature-Pressure-Vacuum Requirement Analysis

Lamination is not simple single-factor exposure — PTFE fabric simultaneously endures:

• Temperature + pressure combined: At 150°C + 100 kPa, PTFE material softening tendency compounds with pressure deformation — requires sufficient creep resistance. After 8,000 cycles: dimensional change rate ≤ 5‰
• Vacuum compatibility: Vacuum phase (0.1–1 kPa) requires ultra-low gas permeability of the fabric surface (prevents EVA permeating into vacuum channels); after vacuum phase, pressure phase requires fabric to rapidly restore flatness — good elastic recovery is essential
• Thermal shock resistance: From vacuum (ambient) → lamination (150°C) → cooling to below 80°C in one cycle; thermal cycling stress requires fabric with CTE ≤ 15 μm/(m·°C) (low thermal expansion) to prevent edge cracking from differential expansion

Ⅳ. Surface Performance Requirements (Non-Stick, Air Permeability, Surface Smoothness)

Non-Stick Performance (Core Requirement)

• EVA/POE encapsulant anti-adhesion at 150°C: anti-stick value ≤ 2 N/25mm (otherwise removal damages the module); no residual adhesive on fabric surface
• After 8,000 cycles: non-stick performance must not degrade significantly (test by measuring EVA peel force before and after cycling — change rate ≤ 20%)

Air Permeability (Key to Avoiding Bubbles and Delamination)

• Standard grade fabric: pore size 0.8–1.2 μm; porosity 5–10%; ensures rapid bubble evacuation in the early vacuum phase while preventing molten EVA from penetrating into vacuum channels
• Permeability uniformity: air permeability deviation across the fabric width ≤ 15% — uneven breathability causes localized bubble retention leading to module defects

Surface Smoothness (Affects Module Appearance)

• Surface roughness Ra ≤ 1.5 μm (smooth surface leaves no imprint marks on the glass surface)
• No localized bumps, fibers protruding through the coating, coating voids, or pinholes — these cause localized pressure anomalies that affect cell yield rate

Ⅴ. Structural Stability Requirements (Dimensional, Chemical, Electrical)

Dimensional Stability (Most Critical for Production Line)

• Thermal elongation at 150°C: ≤ 0.5% (or longitudinal dimensional change ≤ 5‰); must maintain dimensional accuracy after 8,000 cycles
• Width tolerance: ±2 mm (must match laminator cavity width; excessive deviation causes edge blockage or fabric deviation)
• Thickness uniformity: ±0.02 mm (thickness non-uniformity causes uneven pressure distribution → micro-cracking)

Chemical Stability (Prevents Module Contamination)

• No migration of fluorinated compounds, plasticizers, or other low-molecular-weight substances at 150°C — no contamination of glass, cell, or encapsulant surfaces
• Zero chemical reaction with EVA, POE, and other encapsulants — no color change, swelling, or dissolution
• Compliant with RoHS and REACH environmental standards; halogen content ≤ 0.1%

Electrical Safety (Prevents Equipment Safety Hazards)

• Surface resistivity ≥ 10¹² Ω (prevents electrostatic accumulation causing sparking in vacuum environments)
• Dielectric strength ≥ 30 kV/mm (PV modules are high-voltage products; fabric must prevent leakage)

Ⅵ. Product Specification Reference for Standard PV Laminators

Specification Item	Standard PV Lamination Requirements	Premium Grade Target
Thickness	0.25–0.35 mm	0.30 mm (optimal balance)
Width	Customized to laminator ± 2 mm	Precision slit ± 1 mm
Tensile Strength (warp/weft)	≥ 2,500/2,000 N/50mm	≥ 3,000/2,500 N/50mm
Elongation at Break	≤ 5%	≤ 3%
Surface Roughness Ra	≤ 2.0 μm	≤ 1.0 μm
EVA Peel Force	≤ 3 N/25mm	≤ 1.5 N/25mm
Service Life	≥ 5,000 lamination cycles	≥ 10,000 lamination cycles