Why Silicone Molds Fail — Troubleshooting Guide

1. Remedying Issues that will prematurely cause the failure of molds

This is one of the most common reasons of silicone mold failures, which start immediately at the time of their curing. Unless the silicone mixture is mixed correctly, or the ratios are not used correctly, the material cannot crosslink fully creating a mold that is soft, tacky or structurally weak. Curing can also be disrupted due to factors like high humidity, low room temperature or contamination by sulfur based clays, latex materials or incompatibility of additives.

When these happen, the silicone will never attain the required hardness, elasticity or tear strength meaning that the mold is highly susceptible when it comes to casting. Molds that are not cured properly tend to break apart long before this was originally planned as the inside of them was not built to last.

An excessive cold workspace retards the cure and excessive humidity may disrupt the reaction with some silicone systems. Pollution- this may be sulfurous clays, latex gloves or even remaining debris of old molds, which may prevent any curing of the silicone and leave it sticky or gel-like despite the long waiting time.

As soon as a cure imbalance starts life, as a mold, it will never attain the tensile strength or elasticity necessary to be cast again, and will tend to fail in the first few casts, either leaving sink marks or surface flaws, or simply collapsing altogether.

2. Minimal mechanical Stress and Handling Damage

Even an ideal cure silicone mold may wear out even when it is exposed to mechanical stress that is more than the type of stress it was designed to endure. Silicone is elastic, however, when subjected to repeated stretching, twisting or rough demolding, micro-tears would gradually increase with use.

Deep undercuts, hard cast materials or steep part geometries can put too much stress on the mold particularly where force is needed when removing the part. With time, such repeated stresses cause tearing, distortion or permanent deformation.

Rapid production settings in which operators are free and are allowed to treat molds in a rough or inconsistent manner tend to hasten this type of damage. Mechanical stress is one of the most frequent causes of the unexpected failure of silicone molds without design modification, reinforcement, or appropriate release methods.

An excessive cold workspace retards the cure and excessive humidity may disrupt the reaction with some silicone systems. Pollution- this may be sulfurous clays, latex gloves or even remaining debris of old molds, which may prevent any curing of the silicone and leave it sticky or gel-like despite the long waiting time.

As soon as a cure imbalance starts life, as a mold, it will never attain the tensile strength or elasticity necessary to be cast again, and will tend to fail in the first few casts, either leaving sink marks or surface flaws, or simply collapsing altogether.

3. Chemical Reaction and Environmental Exposure.

Silicone molds may also break down because of chemical incompatibility with casting material, cleaning agent or environmental pollution. Some resins penetrating silicone Matrices (In particular highly reactive urethanes or epoxies) may leak into the silicone matrix, and weaken silicone, leading to swelling, fracturing or surface erosion.

Silicone deteriorates over time under the influence of oils, solvents, alcohol-based cleaners or low-quality release agents and becomes less elastic, which leads to the loss of the mold shape. Heat exposure is also a cause of this issue; although silicone is less susceptible to high temperatures than most elastomers, repeated or sustained high temperatures may still render it brittle, promote crack propagation or lead to nonuniform shrinkage.

Even the storage of molds in the sun, in close proximity to equipment that produces ozone or in environments where the control is weak results in the deterioration of the molds much more rapidly than the achievement of production objectives.

Mechanical stress of the storage also contributes; molds that are stored in a pressed form or between heavy objects do not have the properties to recover this and have permanently distorted areas that would no longer produce a correct casting. Mechanical damages are one of the most rapid silicone mold accelerators when they accumulate such as in poor demolding techniques, lack of reinforcement in the design of the mold, or due to work handling.