In food processing, packaging, storage, and household kitchen appliances, sealing rings play a crucial role. They not only serve as a barrier against leakage but also are the first line of defense for food safety. Unlike ordinary sealing rings, food grade sealing rings have a series of strict standards. This article will thoroughly explain the characteristics that food grade sealing rings must possess and introduce several common materials to help you make the right choice.
I. Core Characteristics of Food-grade Sealing Rings: Safety is Paramount
The core requirements for food-grade sealing rings can be summarized as follows: Safety is the foundation, performance is the base, and durability is the key. Specifically, it must possess the following six characteristics:
Absolute food safety
Non-toxic and harmless: The material itself must not contain or release any harmful substances to the human body, such as heavy metals (lead, cadmium, mercury, etc.), harmful plasticizers (phthalates), BPA (bisphenol A), etc.
Odorless and Tasteless: It cannot transfer its own smell or taste to the food, thereby affecting the original flavor of the food.
Compliant with international certifications: It must meet strict regulations for food contact materials. Common certifications include:
US FDA standard: As per 21 CFR 177.2600 of the FDA.
EU standards: such as the EU 10/2011 regulation and the German LFGB certification.
Chinese national standard: GB 4806 series standards.
Outstanding chemical stability
It must be able to withstand the food media it comes into contact with, such as acidic beverages, edible oils, alcohols, alkaline cleaning agents, etc., without experiencing swelling, corrosion, deformation or performance degradation. For example, the sealing ring for edible oil must have excellent oil resistance.
Excellent physical and mechanical properties
High elasticity and resilience: This is the foundation for achieving effective sealing, ensuring a tight fit under pressure and a quick recovery.
Low compression permanent deformation: This refers to the ability of the sealing ring to return to its original shape after being under pressure for a long time. The lower this value is, the stronger the sealing ring's anti-aging ability is and the longer its service life will be.
Appropriate hardness and strength: Ensure that it is not easily torn or subject to permanent damage during installation and use.
Wide temperature tolerance range
It is necessary to adapt to various temperature conditions in food processing, ranging from low-temperature freezing (-60°C) to high-temperature cooking, sterilization (above 100°C), and even baking (above 200°C).
Excellent durability and anti-aging properties
It can resist aging and cracking caused by environmental factors such as oxygen, ozone and ultraviolet rays, thereby extending its service life.
Easy Cleanability
The surface should be smooth and dense, without any residue of food or the growth of bacteria, and easy to clean and disinfect.
II. Common Food-grade Sealing Ring Materials
Different application scenarios require different materials for sealing rings. Here are some of the mainstream options:
1. Platinum sulfide silicone rubber - A symbol of high safety standards
Feature: Produced using platinum catalyst, it is the highest-grade food-grade silicone.
Advantages: Ultra-pure, non-toxic, odorless, resistant to high and low temperatures (-60°C ~ 250°C), high transparency, good flexibility, and excellent biocompatibility.
Disadvantages: High cost, average mechanical strength (tensile strength), not resistant to strong alkalis and long-term steam environment.
Application: Baby pacifiers, medical devices, high-end water dispensers, coffee machines, baking molds, and in situations where they come into direct contact with sensitive foods.
2. Ethylene Propylene Diene Monomer (EPDM) Rubber - The Expert in Heat-Resistant Steam
Characteristic: A universal food-grade synthetic rubber.
Advantages: Outstanding ozone resistance, weather resistance, aging resistance and steam resistance properties, with high cost-effectiveness.
Disadvantage: Not resistant to grease and most solvents.
Application: It is the preferred choice for hot water and steam environments. It is widely used in CIP (in-situ cleaning) systems, cooking equipment, and high-pressure sterilization ovens in the beer, beverage, and dairy industries.
3. Fluorosilicone - The "King" of Harsh Environments
Characteristic: High-performance synthetic rubber, renowned for its ability to withstand extreme environments.
Advantages: Excellent high-temperature resistance (up to 200°C or above), oil resistance, acid and alkali resistance, solvent resistance, and can withstand almost all food media.
Disadvantages: Expensive, elasticity decreases at low temperatures.
Application: Suitable for contact with oils, aromatic solvents, or in demanding environments that require extreme high-temperature disinfection, such as frying equipment and edible oil processing lines.
4. Nitrile Rubber - The Economical Choice for Oil Resistance
Feature: Standard oil-resistant rubber.
Advantages: Excellent tolerance for mineral oil, vegetable oil and fat, highly wear-resistant, low cost.
Disadvantages: Poor ozone resistance and weather resistance; not resistant to polar solvents such as ketones and esters.
Application: Primarily used for equipment that seals edible oils and oil-based foods, such as oil presses and food packaging machinery.
In summary, for the vast majority of daily applications, silicone and EPDM are the most common choices. However, when dealing with extreme conditions like high-temperature oils, fluorosilicone rubber is an indispensable solution. Choosing the correct food-grade sealing ring is a crucial step in ensuring food safety and prolonging the lifespan of the equipment.
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