Guide for Industrial Silicone Rubber Parts: How to avoid over engineering and under engineering?

Why Silicone Rubber needs Engineering?

Silicone is often chosen over conventional rubbers because of its unique molecular structure and chemistry.

To simplify, we can compare silicone and glass—both share silica as a base material.

  • Glass has a rigid 3D molecular structure where oxygen bonds on all sides, giving very high hardness and bond energy.

  • Silicone has a flexible 2D backbone with organic side groups (carbon and hydrogen), making it elastic and rubber-like.

Bond Energy Comparison:

  • Glass: 450–460 kJ/mol

  • Silicone Rubber: 440–450 kJ/mol

This is why silicone behaves like a “flexible glass”—high thermal stability like glass, but with the flexibility of an elastomer. However, this structure also means silicone can be vulnerable to certain chemicals and extreme conditions if not formulated correctly.

Understanding this chemistry is the first step in preventing wrong material selection.

Core Properties of Silicone Rubber

These are the natural, inherent properties of silicone rubber that make it popular across industries:

  • Temperature resistance

  • Flexibility across wide temperature ranges

  • Non-reactive nature

  • Natural transparent color

  • Ozone, UV, and weather resistance

  • Food-grade and food-safe capability

  • Biocompatibility and low leachability

  • Low extractables

  • Resistance to mild acids, alkalis, and chemicals

  • Oxidation resistance

These properties alone already satisfy most industrial needs. Problems arise when designers demand far more than the application actually requires—or far less than what the environment demands.

Modified Properties – Where Engineering Begins

Silicone can be modified into hundreds of specialized versions. Some of the key modifications include:

  • Flame retardant and self-extinguishing

  • Custom colors (natural transparent to any RAL color)

  • High dielectric and volume resistivity

  • Low or high thermal conductivity

  • Conductive, semi-conductive, and insulating grades

  • Low coefficient of friction

  • Odorless and tasteless

  • Microbial resistant

  • Non-sticky or non-blocking surfaces

  • High tear and tensile strength

  • Very high elongation (>1000%)

  • Optical or glass-like transparency

  • Fully opaque

  • X-ray detectable (radiopaque)

  • Fluorescent

  • Fuel, oil, and solvent resistance (FVMQ)

  • Low gas permeability

  • Radiation resistance

  • Temperature resistance up to 300°C

  • Antistatic

  • Metal-bondable grades

  • EMI shielding

  • Extra low temperature down to -100°C

  • Low swelling

  • Zero halogen, low smoke, low toxicity

  • Hardness from ultra-soft 5 Shore A to 90 Shore A

  • Different compression set behaviors

  • High damping or high resilience

  • Matte or glossy finish

  • Magnetic grades

  • Sponge and foam

  • Fabric or metal reinforced

  • Heat shrinkable

  • UV cured

  • Arc, track and erosion resistant

  • Hydrophobic to super-hydrophobic

  • Oil bleeding grades

  • Self-adhesive and self-amalgamating

  • Recyclable or reusable (ongoing developments)

Silicone can be engineered to almost any extreme—but that does not mean it always should be.

Over-Engineering vs Under-Engineering

Over-Engineering

Happens when:

  • Extremely high temperature grade is chosen for normal temperature use

  • Medical-grade material is used for simple industrial sealing

  • Ultra-high tear or tensile grades are used where no mechanical stress exists

  • Exotic certifications are demanded without regulatory need

Result:

  • Higher cost

  • Longer lead times

  • Unnecessary complexity

  • Difficult processing

Under-Engineering

Happens when:

  • Chemical exposure is ignored

  • Temperature cycling is underestimated

  • Compression set is not considered

  • Electrical or flame requirements are overlooked

Result:

  • Premature failures

  • Safety risks

  • Recalls and rework

  • Loss of customer trust

The right design sits exactly in the middle: fit-for-purpose engineering.

Types of Silicone Based on Curing

Silicone is also classified by curing systems:

  • Peroxide cured

  • Platinum cured

  • Condensation cured

  • Addition cured

Each affects:

  • Mechanical strength

  • Purity and extractables

  • Food/medical suitability

  • Heat and aging performance

Wrong curing system selection is a common reason for over- or under-engineering.

Processing Methods

Silicone rubber can be processed by:

  • Extrusion

  • Moulding

  • Hand fabrication

  • Dipping

  • Calendaring

Design must consider process limitations. Over-complicated designs increase waste, tooling cost, and rejection rates.

Standards and Compliance

Silicone parts can meet many global standards, including:

Medical & Food:
FDA, USP Class VI, ISO 10993, BfR

Environmental & Chemical:
REACH, RoHS, SVHC

Fire & Safety:
EN45545, UL 94, IEC 60695, FAR 25.853, AMS, MIL-DTL/MIL-PRF, BS 6853, WRAS, NSF

Testing & Quality:
IEC, ASTM, ISO

Only demand what your application legally or technically requires—nothing more, nothing less.

How Centroid Approaches Smart Engineering

At Centroid, every silicone product is designed by correlating:

  • Application environment

  • Temperature, chemical, and mechanical loads

  • Regulatory requirements

  • Processing method

  • Cost targets

We use:

  • Internal laboratory testing

  • Third-party certified labs

  • AI-assisted material selection tools

  • Expert formulation design

This ensures customers get the most economical and reliable solution, not the most expensive or the weakest.

Design Support & Prototyping

We offer:

  • Free design consultation

  • Low-cost in-house prototyping

  • Rapid testing and validation

This helps OEMs avoid both over- and under-engineering before mass production begins.

You can share your design needs, concerns, problem statement over here.