Silicone rubber and soft PVC should be treated as difficult, flexible substrates rather than ordinary plastic. Silicone has very low surface energy, while soft PVC can contain plasticizers or surface additives that change over time. A standard cyanoacrylate may not wet or retain adhesion consistently without the right surface preparation. TongLin recommends a small real-part trial before approving a grade, primer, or activator.
Separate the surface questions
First identify the exact polymer, hardness, additives, finish, and expected movement. Then record cleaning, abrasion, primer or activator use, open time, and joint geometry. A primer is not interchangeable with an accelerator: the former can change surface receptivity, while the latter is normally used to influence cure speed.
| Substrate | Pre-check | Acceptance focus |
|---|---|---|
| Silicone rubber | Surface energy, release residue, and flex direction | Peel, flex cycling, and cohesive failure |
| Soft PVC | Plasticizer migration, finish, and hardness | Aging, peel, and surface appearance |
| Mixed flexible joint | Movement, compression, and gap recovery | Repeated movement and post-conditioning bond |
Do not approve a rigid pull result alone when the finished product bends or stretches.
Use a focused candidate set
Silicone B is TongLin’s catalog starting point for a silicone-related comparison. S508 and S5401 can help compare flow and bead control, but neither product page replaces a trial on the customer’s actual polymer. Review the primer and activator guide before adding a surface treatment.
Validate aging and production variation
Test several parts, lots, and cleaning cycles. Inspect initial wetting, fixture time, failure mode, and appearance after heat, humidity, or flex conditioning defined by the customer. For a private-label process, send the polymer details and joint drawing through the cyanoacrylate OEM service. The material comparison guide explains how to keep flexible and rigid substrates in separate validation streams.
For a recommendation on the actual polymer, send the material and joint details through Contact.