High-consistency rubber (HCR) silicones see extensive use in diverse industries. Healthcare, in particular, uses this silicone variant in medical device manufacturing.
You can shape these elastomers into tubings, sheets, and other medical device components. But to ensure optimal use, manufacturers must take certain steps during production.
1. What is High-Consistency Rubber Silicone?
Silicone rubber sees as mainstream industry use. That’s no wonder since it can perform well even under extreme conditions. This elastomer has different types, one of which is High Consistency Rubber (HCR).
HCRs come out as clay-like in form, possessing high viscosity. Like all solid silicone, HCRs have high molecular weight and long polymer chains. These properties make them resistant to compression and elongation. And they also provide their higher levels of elasticity.
Like other silicone variants, HCRs resist extreme temperatures (both hot and cold). They also have superior electrical properties, chemical stability, and flame retardancy.
Generally, manufacturers can process HCR using various fabrication techniques. These methods include transfer molding, extrusion, calendering, and compression. You can also modify HCRs using additives to meet certain end product specifications.
2. The 5 Steps in the HCR Manufacturing Process.
2.1 Softening and Catalyst Incorporation
Uncured silicone stiffens from prolonged storage. So, manufacturers must perform softening as the initial step. To do this, the uncured material must go through milling. Sometimes, more than once. This process ensures the compound material mixes into a homogenous outcome.
Manufacturers then add the catalyst, which is either peroxide or platinum. This first step is necessary for both the molding and extrusion techniques.
2.2 Preform Preparation
Preparation starts by using a die-cutter to cut a plug from the preform. The plug is then fitted into the transfer press’ reservoir.
When applying the compression molding technique, the preform cut must be similar in shape to the intended component. This procedure introduces extra complexity because of the accuracy needed.
For extrusion and injection molding techniques, preparation means cutting the preform into strips. The cut pieces are then fed into the extruder.
Once prepared, the compound then goes through the main fabrication procedure. There are two main types of HCR fabrication: extrusion and molding.
This method involves using a single-screw extruder. The cut elastomer strips are fed to this extruder using a roller. It then squeezes through a die, which shapes the elastomer in the desired form.
Personnel loads the elastomer into molding equipment to produce the finished component. The molding process requires different equipment depending on the silicone application.
For instance, compression molding would require personnel to load preforms in each mold cavity. Since HCR cures slowly, the molds must consist of many individual cavities.
The extruded components must go through vulcanization to improve their physical properties. For this stage, manufacturers typically use are hot-air vulcanizing ovens (HAVs). Though some might also use a steam autoclave machine and radiant heat.
During vulcanization is when HCRs are reinforced and made tougher. The cross-linking reaction in the elastomer’s molecules increases its strength and durability.
Once an elastomer completes vulcanization, it must go through various finishing touches. These may include post-curing, trimming, and de-flashing, among others. The degree of the finish depends on the intended product’s specifications.
3. How to Ensure Optimal HCR Use?
Manufacturers can follow certain practices to ensure the optimal use of HCR silicones. These practices, if adhered to, may warrant everyone in the supply chain to get the most out of HCR.
When performing any fabrication method, manufacturers can’t take any chances. Personnel must follow all guidelines and best practices down to the last detail. Here are notable examples:
This strategy applies when using the calendering method for a peroxide-cured HCR. You can actually create gaskets that self-adhere. Die-cut the gaskets, press them in place and cure them for a complete seal.
HCRs are widely used in industry for good reason. These elastomers own many desirable properties that are too practical to pass up. Still, not all HCR products are of equal quality. Remember that every end product is only as good as its manufacturing quality.
It’s crucial to work with a reliable supplier that sticks to best practices in HCR manufacturing.
At GX Silicone, we run an active R&D team to ensure every process adheres to the highest innovative standards. We also make sure to use only the most state-of-the-art equipment and remain up-to-date with every industry certification.
This all comes down to providing high-quality products for the discerning client. Contact us and we’ll assist you in choosing the right solution for your application.