Differences Between PET / PP / PVC Labels: 3 Types of Resin Molecular Structures + 7 Selection Scenarios

Last week, a customer in the electronics components business asked me: "I need to make high-temperature-resistant labels—should I use PET or PP?"

I said: "It depends on your application—the molecular structures of the three resins are completely different."

He asked, "What's the difference?"

I said: "PET contains benzene rings (rigid and heat-resistant), PP has a chain structure (flexible and chemically resistant), and PVC contains chlorine (elastic and self-extinguishing)—molecular structure determines physical and chemical properties. This article won't discuss 'which is better'—instead, it covers the molecular structures of the three resins plus 7 application scenarios, so you can make the right choice with a single table."

Comparison of Molecular Structures of 3 Resins

Molecular Structure of PET (Polyester)

Molecular Formula: (-CO-C₆H₄-CO-O-CH₂-CH₂-O-)n

Key Groups: benzene ring + ester bond

Structural Features:

• Benzene ring = rigidity
• Ester bond = strong polarity
• Regular arrangement = 50% crystallinity

Physical Properties:

• Temperature resistance: -40 to 200°C (good for both high and low temperatures)
• Strength: 200 MPa tensile (strong)
• Transparency: 85% translucent

Chemical Properties:

• Resistant to oil / alcohol / weak acids
• Not resistant to strong alkalis and phenol
• Not UV-resistant (yellows over time)

Molecular Structure of PP (Polypropylene)

Molecular Formula: (-CH₂-CH(CH₃)-)n

Key Group: methyl side chain

Structural Features:

• Chain structure = flexibility
• Methyl group = hydrophobicity
• Crystallinity 50-70%

Physical Properties:

• Temperature resistance: -20 to 100°C (medium temperature)
• Strength: 30 MPa tensile (medium)
• Transparency: 60% semi-transparent

Chemical Properties:

• Resistant to acids and alkalis (chemically stable)
• Resistant to organic solvents
• Not UV-resistant (requires UV stabilizers)

Molecular Structure of PVC (Polyvinyl Chloride)

Molecular Formula: (-CH₂-CHCl-)n

Key Group: chlorine atom

Structural Features:

• Chlorine atom = polarity + chemical inertness
• Irregular structure = elasticity
• Crystallinity 5-10% (low)

Physical Properties:

• Temperature resistance: -10 to 80°C (low temperature)
• Strength: 50 MPa tensile (medium)
• Transparency: 90% fully transparent

Chemical Properties:

• Weather-resistant + self-extinguishing (extinguishes when removed from flame)
• Resistant to acids and alkalis
• Contains chlorine (banned in some countries)

Comparison of Physical Properties of 3 Molecular Structures

Chemical Performance Comparison of 3 Molecular Structures

7 Scenario Selection

Scenario 1: Electronic Component Traceability

Recommendation: PET (high-temperature reflow soldering resistant at 150°C)

Rationale: Reflow soldering is a critical step in the SMT process (high-temperature soldering at 150°C); PET is the only material that can withstand it

Cost: +0.5 yuan/sheet

Scenario 2: Food Outer Labels (Standard)

Recommendation: PP (cost-effective + sufficient water resistance)

Rationale: PP offers water resistance + heat resistance up to 100°C (sufficient for microwave + boiling water sterilization)

Cost: +0.2 yuan/sheet

Scenario 3: Cosmetic Bottle Body (Transparent)

Recommendation: PVC (fully transparent to show the liquid inside)

Rationale: Cosmetic bottle labels commonly require transparency to display the liquid color; PVC's 90% transparency makes it the most suitable choice

Cost: +0.4 yuan/sheet

Scenario 4: Cold Chain Food

Recommendation: PP (T_g = -10°C, cold-resistant)

Rationale: In a frozen -20°C environment, PP has a low glass transition temperature, so its molecules will not freeze

Cost: +0.2 yuan/sheet

Scenario 5: Medical Device Sterilization

Recommendation: PET (no deformation after sterilization)

Rationale: Ethylene oxide sterilization / radiation sterilization requires high-temperature resistance; PET is the most stable

Cost: +0.6 yuan/sheet

Scenario 6: Outdoor Products

Recommendation: PP + UV stabilizer (weather-resistant)

Rationale: PP itself is not UV-resistant, but with UV stabilizers added, it can last 1-3 years outdoors

Cost: +0.3 yuan/sheet

Scenario 7: Children's Toys (EU Export)

Recommendation: PE or PP (chlorine-free)

Rationale: EU REACH restricts PVC (contains chlorine); toy labels must use PE/PP

Cost: +0.2 yuan/sheet

3 Resins for Quick Identification

Method 1: Combustion Test (30 seconds)

• PET: Yellow flame + black smoke (benzene ring combustion) + dripping
• PP: Blue flame (chain hydrocarbon combustion) + no dripping
• PVC: Flame-retardant + self-extinguishes when removed from flame (contains chlorine)

Method 2: Transparency

• PET: Translucent (objects appear blurred)
• PP: Opaque
• PVC: Fully transparent (text clearly visible)

Method 3: Tactile Feel

• PET: Stiff (does not break when folded 90°)
• PP: Flexible (rebounds after folding)
• PVC: Elastic (rubber-like feel when stretched)

To view the material map — refer to the complete comparison of 12 label materials, or directly contact a LeXiang Packaging consultant, material selection + quotation provided within 24 hours.