A seal or gasket on a packaging machine does not move product, form bags, or apply codes. It sits in a joint, a cover, or an interface between two surfaces, and it prevents something from getting through: air, moisture, product contamination, cleaning chemicals, or heat. When the seal is working, nobody knows it exists. When it fails, the consequences range from a minor air leak that reduces pneumatic efficiency to a food safety event where cleaning chemicals migrate into the product zone through a degraded gasket.
The maintenance challenge with seals and gaskets is that they degrade invisibly. Rubber and silicone compounds harden, crack, and lose elasticity over time from heat exposure, chemical contact, and compression set. A gasket that was soft and conformable when installed becomes rigid and brittle after 18 months of continuous thermal cycling. It still looks like a gasket. It no longer seals like one. The joint it was protecting now leaks at a rate too slow to notice visually but fast enough to affect machine performance, energy efficiency, or sanitary integrity.
This article covers the elastomer types used in packaging equipment seals and gaskets, how to match the material to the operating environment, and how to identify when a seal has passed its useful life.
Quick Reference: Match Your Application to an Elastomer
| Application | Elastomer | Why This Material |
|---|---|---|
| Heat sealing station gaskets and thermal insulation | Silicone (VMQ) | Temperature range -60°C to +230°C. Maintains flexibility through thousands of thermal cycles at sealing temperatures. |
| Guard door seals, enclosure gaskets | Silicone foam (closed-cell) | Closed-cell construction blocks water, air, and dust. Adhesive backing for clean installation. No glue residue on removal. |
| Washdown environment door seals | EPDM | Excellent resistance to hot water, steam, caustic soda, and dilute acids. Good compression set resistance for door seal applications. |
| Sanitary pump seals and food-contact gaskets | PTFE or EPDM (FDA-compliant) | FDA 21 CFR compliant. Non-porous surface resists bacterial harborage. PTFE for chemical universality, EPDM for cost-effective compliance. |
| Pneumatic cylinder rod seals | Polyurethane or NBR | High abrasion resistance for dynamic sealing. See the rod seals catalog for packaging-specific seal profiles. |
| Oil and grease exposure (gearbox seals) | NBR (nitrile) | Standard oil-resistant elastomer. Temperature limit around 100°C. Not suitable for washdown chemicals. |
| Aggressive chemicals, high temperature | FKM (Viton) | Resists most industrial chemicals, solvents, and fuels. Temperature range to +200°C. Premium cost. |
| Legacy machine, OEM gasket discontinued | Custom to original spec | Material, durometer, profile, and dimensions matched from worn sample or drawing. |
That covers the quick match. The sections below explain why silicone dominates packaging equipment applications, how each elastomer handles the specific chemical and thermal stresses found in food plants, and how to measure whether a gasket still seals.
Why Silicone Is the Default for Packaging Machine Seals
Silicone (VMQ) has the widest operating temperature range of any common elastomer: -60°C to +230°C in continuous service. On a packaging line, that range matters because seals and gaskets are exposed to temperature extremes that no other elastomer handles without degradation.
A gasket on a heat sealing station sits adjacent to jaw bars operating at 150 to 200°C. A gasket on a shrink tunnel door is exposed to tunnel temperatures of 180 to 220°C on the inside surface and ambient temperature on the outside. A gasket on a freezer conveyor transition operates at -30°C to -40°C. Silicone maintains its flexibility, compression recovery, and sealing force across all of these temperatures. NBR (nitrile) hardens and cracks above 100°C. EPDM loses elasticity below -30°C. Only silicone covers the full range without material substitution.
Vanguard stocks silicone adhesive-backed seal gaskets in two widths: HTMPSLC1X6.6 (1″ x 6.5ft) and #HTMPSLC2X6.6 (2″ x 6.5ft). These are closed-cell silicone foam with adhesive backing for direct application to machine frames, guard doors, enclosure panels, and thermal insulation surfaces. The closed-cell construction prevents water, air, and gas absorption, and the adhesive leaves no glue residue when the gasket is removed and replaced.
Where Silicone Falls Short
Silicone is not the correct choice for every application. It has low tear strength compared to other elastomers. A silicone gasket in a joint that is opened and closed frequently (a maintenance access panel, for example) tears at the bolt holes faster than an EPDM or NBR gasket would. It also has poor oil resistance. A silicone gasket exposed to petroleum-based lubricants swells and loses dimensional stability. For gearbox covers, oil-lubricated bearing housings, and any joint exposed to mineral oil, NBR is the correct choice.
Elastomer Comparison for Packaging Environments
| Property | Silicone (VMQ) | EPDM | NBR (Nitrile) | FKM (Viton) |
|---|---|---|---|---|
| Temperature range | -60 to +230°C | -40 to +150°C | -30 to +100°C | -20 to +200°C |
| Caustic soda (NaOH) | Good | Excellent | Poor | Poor |
| Peracetic acid | Good | Excellent | Poor | Good |
| Chlorinated sanitizers | Good | Excellent | Fair | Good |
| Mineral oil / grease | Poor | Poor | Excellent | Excellent |
| Compression set resistance | Good | Very good | Good | Fair |
| Tear strength | Low | Good | Good | Fair |
| FDA food contact | Yes (most grades) | Yes (FDA grades) | Limited | Yes (FDA grades) |
| Cost | Medium | Low | Low | High |
FDA Compliance for Food-Contact Seals and Gaskets
Any seal or gasket that contacts food, contacts a food-contact surface, or could allow contaminants to migrate onto a food-contact surface must comply with FDA 21 CFR regulations for food-contact materials. The specific regulation depends on the material type: 21 CFR 177.2600 covers rubber articles, 21 CFR 175.300 covers resinous coatings, and 21 CFR 177.1550 covers PTFE.
FDA compliance is not a property of the elastomer type. It is a property of the specific compound formulation. A silicone gasket made from an FDA-compliant silicone compound is food-safe. A silicone gasket made from an industrial-grade silicone compound with non-compliant fillers or plasticizers is not. The elastomer name on the material data sheet is not sufficient. The gasket must come with a Declaration of Compliance (DoC) from the manufacturer stating that the specific compound meets the applicable CFR section.
Vanguard stocks the PTFE inboard gasket (4410G-80-12AG) for Ampco AC/AC+ Series sanitary pumps. PTFE is the gold standard for sanitary pump gaskets because it is chemically inert (resists every cleaning chemical used in food plants), non-porous (no bacterial harborage), and FDA-compliant across all temperature ranges encountered in food processing.
For the full FDA compliance framework for food-contact materials in packaging equipment, see the food-grade conveyor belt compliance guide, which covers the same CFR sections and documentation requirements that apply to seals and gaskets.
How Seals and Gaskets Fail on Packaging Equipment
Compression Set
Every elastomer takes a permanent deformation when compressed for extended periods. This is called compression set, and it is expressed as a percentage of the original deflection. A gasket with 30% compression set has lost 30% of its ability to spring back to its original thickness after the clamping force is removed. In practical terms, the gasket is 30% thinner than when it was installed, and it exerts 30% less sealing force against the mating surfaces. The joint it was protecting now leaks.
Compression set is accelerated by heat. A silicone gasket at room temperature may take 10 years to reach problematic compression set. The same gasket at 200°C may reach the same level of set in 18 months. This is why gaskets on heat sealing stations and shrink tunnel doors need more frequent replacement than gaskets on ambient-temperature enclosures.
Chemical Attack
The wrong elastomer in a chemical environment does not just degrade. It swells, softens, and loses its mechanical properties. An NBR gasket exposed to caustic soda during washdown absorbs the chemical, swells by 10 to 15%, and becomes soft and mushy. The swollen gasket fills the joint and appears to seal better than before. But the softened material has no compression recovery. The next time the joint is opened and closed, the gasket does not spring back and the joint leaks. This failure mode is deceptive because the gasket looks fine (it is bigger and softer than a new one, which looks wrong but does not look failed) until the joint is disturbed.
Thermal Degradation
Elastomers exposed to temperatures above their rated range harden, crack, and become brittle. The hardening is permanent and irreversible. An NBR gasket that has hardened from heat exposure cannot be restored by cooling it back down. The crosslink structure of the polymer has changed, and the material is now a rigid plastic rather than a flexible elastomer. A hardened gasket cracks under compression instead of deforming, and the cracks become leak paths.
The 5-Minute Gasket Inspection at the Next Maintenance Window
When the OEM Gasket Is Discontinued
Seals and gaskets for packaging machines are specified by a combination of material, durometer, cross-section profile, and dimensions. Many packaging machine gaskets are not standard catalog items. They are custom-cut or custom-molded to fit specific machine interfaces that the OEM designed for that model. When the OEM stops supporting the machine, the gasket disappears from the supply chain along with it.
Vanguard’s custom fabrication process covers gaskets cut from sheet stock to customer-supplied dimensions, custom-molded O-rings and profile seals, FDA-compliant compounds for food-contact applications, and high-temperature silicone gaskets for sealing stations and heat tunnels. Provide the worn gasket, the OEM part number, or a dimensional drawing with the material specification. Vanguard confirms fabrication feasibility within one business day.
Browse stocked silicone gaskets in the silicone rubber catalog. For dynamic rod seals and cylinder seals, see the rod seals catalog. For PTFE seal profiles used on heat sealing jaws, see the heat sealing catalog. If your OEM gasket has been discontinued or you need a custom seal fabricated to sample, submit your part details through the custom parts request. Vanguard ships across the US, Canada, and Mexico.
