The inner liner of a beer bottle cap (commonly referred to as "bottle cap sealing gasket" or "crown cap inner liner" in professional terminology) is a critical component that ensures the airtightness, freshness preservation, and safety of beer.
The material application has undergone an evolution from traditional to modern, with the core objectives being: non-toxic, odorless, excellent elasticity, strong sealing, pressure resistance, corrosion resistance (acid and alcohol resistance), and ease of industrial production.
Main Material Types and Application Characteristics
1. PVC (Polyvinyl Chloride) Gasket - Traditional Mainstream
Composition: Typically composed of a mixture of PVC pellets, plasticizers, stabilizers, foaming agents, etc., which are baked at high temperatures to achieve foaming and molding.
Advantages:
Excellent sealing performance: The micro-porous structure formed after foaming possesses outstanding elasticity, effectively filling minor irregularities at the bottle mouth.
Low cost: Mature raw materials and production processes result in low costs.
Strong adhesion: Forms a firm bond with metal lids.
Drawbacks and Elimination:
Environmental and Health Concerns: Traditional PVC gaskets may contain phthalate-based plasticizers, posing potential migration risks. Additionally, PVC itself contains chlorine, which can generate dioxins during incineration when discarded.
Odor issue: Poor-quality PVC gaskets may impart a "plastic taste" or "gasket flavor" to beer.
Current Situation: Due to environmental and health concerns, it has been largely phased out in mature markets such as Europe and the U.S., but remains in use in some developing countries and lower-tier markets.
2. PE (Polyethylene)/PET (Polyethylene Terephthalate) Gasket - Eco-Friendly Upgrade
Composition: Typically made from food-grade PE or PET materials, formed through physical foaming or direct molding.
Advantages:
Safe and Non-Toxic: PE and PET are recognized as safe food-contact materials, free from chlorine and harmful plasticizers.
Odor-free: The pure material does not impart any off-flavors to the wine.
Environmental Protection: The material is more easily recyclable.
Disadvantages:
The sealing elasticity is slightly inferior to PVC: requiring more precise bottle openings and higher capping craftsmanship.
The cost is slightly higher.
Current Status: It is the mainstream choice for mid-to-high-end beer brands worldwide and the most common solution for replacing PVC.
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