The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →There is no single best glue for every silicone rubber. For bonding compatible Smooth-On RTV moldmaking silicone to silicone, Smooth-On’s Sil-Poxy is a purpose-made option. For silicone joined to plastic, metal, or another material, use an adhesive or primer-and-adhesive system whose manufacturer explicitly lists both sides of the joint. The right choice depends on the silicone formulation, the adjoining material, expected movement, cure process, and service conditions.
Why silicone rubber is difficult to bond
Silicone rubber is flexible and has a low-surface-energy surface, which can make ordinary adhesives unreliable. A product that bonds one silicone formulation—or works with a specified primer—cannot automatically be assumed to bond every commercial silicone elastomer. The same caution applies to the other side of the joint: confirm that the adhesive manufacturer names the material you are bonding to.
The available manufacturer documents describe product-specific uses and specifications, not a controlled comparison that identifies one universally strongest glue. Choose by compatibility and process requirements rather than a headline strength figure.
Which adhesive should you consider?
| Option | Manufacturer-stated scope | Key process or timing | Important qualification |
|---|---|---|---|
| Smooth-On Sil-Poxy | Bonding Smooth-On tin- or platinum-cure RTV moldmaking silicone to silicone; the bulletin also names certain plastics, plaster or ceramics, and fabrics. | Clean and dry surfaces; abrasion and solvent wiping are suggested where possible. Begins curing in about 5 minutes; handling after about 1 hour depending on temperature and humidity; full cure after 24 hours. | Purpose-made for the stated Smooth-On RTV silicone scope; this does not establish compatibility with every silicone or substrate. |
| 3M Scotch-Weld PR100 | 3M lists silicone rubber among its substrates and describes fast-strength bonding. | Approximately 20-second handling time and 24-hour full cure, according to 3M. | 3M labels it industrial/occupational use only, not for consumer sale or use. Timing and strength claims are manufacturer statements. |
| 3M AC79 primer with a compatible cyanoacrylate | Primer intended to improve cyanoacrylate adhesion on difficult-to-bond low-surface-energy elastomers, including silicone. | 3M says to apply the primer to each low-surface-energy substrate surface for desired results; follow current product directions for the full process. | Industrial/occupational use only. Do not assume generic cyanoacrylate or a different primer performs the same way. |
| WACKER Primer G 790 Toluene Free | Primer for addition-curing silicone rubbers, including named WACKER silicone families, bonded to metallic and non-metallic substrates. | WACKER calls for clean, dry surfaces, a thin primer layer, and a guiding dry time of 1–2 hours at ambient temperature and 40% relative humidity; apply silicone preferably within about 5 hours after drying. | These directions are specific to this primer and its stated silicone systems; do not transfer them to Sil-Poxy or 3M products. |
How to choose for your joint
Silicone to silicone
If both pieces are Smooth-On tin- or platinum-cure RTV moldmaking silicone, Sil-Poxy is the most directly matched option in the cited manufacturer documentation. Smooth-On also describes it for repairing torn silicone rubber molds and for applications such as prosthetics and animatronics. If either silicone comes from another manufacturer or its formulation is unknown, do not assume the same result: check with the adhesive and silicone manufacturers, then test a small sample.
Free tools Windows power users keep installed
One-click scans. No signup required.
#1 Best Overall
- [Always Ready] Tired of tossing squishies that split open, silicone toys that tear or TPR figures that break? INSOIA silicone glue creates a bond as strong as new — clear, flexible, won't crack or become brittle. One 20g bottle with 4 precision tips fixes squishies, silicone phone cases, TPR toys and rubber items. Whether you're a parent fixing kids' toys, a collector restoring favorites, or someone who hates waste — repair, don't replace.
- [Fast & Waterproof] No mixing, no waiting. Just twist the cap, squeeze gently, and the glue sets in 10-45 seconds. Apply a thin layer for the strongest, fastest bond. Full cure in 12-24 hours creates a waterproof, flexible seal that survives hand washing, humidity and daily play. Your repaired squishies and silicone items stay intact through every squeeze and every condition you encounter, day after day.
- [Easy for Anyone] You don't need to be a professional to fix broken squishies. Four precision tips reach deep into tear gaps, toy seams and tight corners where regular glue can't go — each tip delivers a controlled drop, no mess. The anti-clogging cap keeps the nozzle clean and reusable, so your glue stays fresh down to the last drop. Professional-quality silicone repair at home, even if you've never fixed anything before.
- [Fix Any Silicone] Seal squishy splits, patch silicone phone cases, fix TPR toy tears, mend rubber figures, bond silicone molds. Bonds silicone to silicone, TPR, rubber, plastic and metal. One bottle handles squishies, phone cases, kitchen seals, baking mats and DIY crafts. Whether you're a parent at the kitchen table or a hobbyist at the workbench, one bottle is all you need. Not for PP/PE plastics.
- [Trusted Quality] Professional-grade cyanoacrylate formula, non-toxic and clear-drying. Apply a thin layer on clean, dry surfaces — thinner layers cure faster and bond stronger. Sets in 10-45 seconds, full cure in 12-24 hours. Backed by INSOIA's 15+ years of adhesive expertise and satisfaction guarantee. Quality you can trust for silicone repairs that matter to you and your family.
Silicone to plastic, metal, or another material
Start with the exact substrate pair, not just the word “silicone.” Sil-Poxy’s bulletin names certain plastics, plaster or ceramics, and fabrics, but that broad category does not identify every grade or surface. 3M lists silicone rubber for PR100 and describes AC79 as a primer for low-surface-energy elastomers such as silicone; use only a compatible product system and observe 3M’s industrial/occupational restriction. WACKER Primer G 790 is a distinct route for its specified addition-curing silicone rubbers and metallic or non-metallic substrates.
Moving, flexible, or service-critical joints
Consider how far the joint must flex, whether it will be loaded in peel or tension, and what temperature or other service conditions it will face. Sil-Poxy is described as providing a strong, flexible bond between silicone parts. Its stated temperature range and mechanical values are manufacturer specifications in a specific test context—not a guarantee for a different silicone, substrate, joint design, or installation. When failure could cause injury or significant damage, obtain compatibility guidance for the exact materials and validate the joint under its intended conditions.
Rank #2
- Clear Silicone Sealant & Adhesive: Is A General Purpose Sealant Adhesive, Rtv (Room Temperature Vulcanized)Silicone Designed For Use In Household Or Mechanical Assembly Applications.
Preparing and bonding the surfaces
For Sil-Poxy
- Confirm that the silicone and adjoining substrate fall within the product’s stated scope. If suitability is uncertain, make a small test application first.
- Make the surfaces clean and dry. Smooth-On says, “A clean, dry surface is essential for successful adhesive bonding.” It suggests abrasion followed by a solvent wipe where possible; follow the current product instructions and ensure the surface is suitable for the chosen solvent.
- Apply and assemble the joint according to the current product bulletin and label. Account for the difference between the product beginning to cure, becoming handleable, and reaching full cure.
- Use ventilation, eye protection, long sleeves, and rubber gloves as Smooth-On advises. Do not apply uncured product to skin, and follow the current label and safety documentation.
For a primer-and-adhesive system
Use the instructions for that exact system. WACKER’s Primer G 790 guidance calls for surfaces free of grease, oil, wax, dust, rust, and other contaminants; very smooth surfaces may be roughened. It specifies a thin primer film and gives 1–2 hours at ambient temperature and 40% relative humidity as a guiding drying value, with silicone preferably applied no later than about 5 hours after drying. Those figures and steps are not general instructions for Sil-Poxy, PR100, or AC79.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to interpret the published strength and cure figures
Manufacturer data can help screen products, but values from different tests or product systems are not a head-to-head ranking. Smooth-On’s Sil-Poxy bulletin revision marker 121123DH (2023) reports the following silicone-to-silicone values measured after seven days at 73°F (23°C):
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesRank #3
- FIX TORN SQUISHIES & HARD-TO-BOND SILICONE – Split squishy, peeling silicone or torn TPR toy? This Silicone Glue for squishies bonds silicone, silicone rubber, TPU, TPE and TPR where ordinary glue often struggles, helping restore flexible items instead of replacing them.
- FAST-DRYING, WATERPROOF & TEMPERATURE RESISTANT – Get repairs done without unnecessary waiting. After full cure, the adhesive forms a waterproof bond designed to handle everyday moisture and temperature changes at home, in the workshop or outdoors.
- ONE CLEAR ADHESIVE FOR MORE MATERIALS – This clear Silicone Adhesive goes beyond squishies, bonding compatible rubber, plastic, glass, metal and ceramic surfaces. Make cleaner, less-visible repairs without keeping a different specialty glue for every project.
- 6 PRECISION TIPS FOR SMALL, CLEAN REPAIRS – Reach deep squishy tears, narrow seams, tiny model parts and tight corners without flooding the repair with glue. Six applicator tips give you better control over placement, helping make cleaner fixes with less mess.
- 100g VALUE FOR REPAIRS, CRAFTS & MORE – Two 50g bottles give you 100g total, so you have more glue ready for squishy repairs, models, crafts and everyday fixes. The clear, odorless formula makes it practical for repeated projects—repair more and replace less.
- Tensile strength: 750 psi.
- Elongation at break: 750%.
- Peel strength: 100 ppi.
- Tear strength: 100 ppi.
- Stated temperature range: -50°F (-41°C) to 500°F (260°C).
3M reports PR100 overlap shear strength of over 2,000 psi after full cure, alongside its approximately 20-second handling time and 24-hour full cure. That is a manufacturer-reported product figure, not a directly comparable silicone-to-silicone test against Sil-Poxy. Handling time is not full-cure time, and neither figure by itself predicts performance in a particular joint.
Quick Recap
Best Value
- Strong Flexible Bond Performance Form‑fitting adhesive creates durable, stretch‑resistant bonds for soft, bend‑able items. It moves with flexible materials without cracking or breaking after repeated bending
- Controlled No‑Mess Application Built‑in fine precision nozzle delivers an exact amount of glue. You can target narrow cracks, tiny gaps and worn seams with no messy overspill
- Transparent Non‑Yellowing Result Dries into a crystal‑clear, invisible layer. It will not leave ugly white marks and keeps the repaired area looking clean on translucent and colored surfaces
- Wide‑Range Soft‑Material Repair Perfect for fixing rips, splits, loose edges and small holes on rubber toys, soft balls, shoe parts and flexible household accessories
- Household & DIY Friendly Glue Works great on TPR, TPE, TPU, silicone‑like rubber and most soft plastics. A practical repair supply for daily home maintenance and handmade craft projects
Rank #4
- MADE FOR SILICONE – Joins silicone pieces and selected plastic, metal, glass, and ceramic surfaces.
- FLEXIBLE FINISH – The joined area remains flexible after setting.
- CLEAR APPEARANCE – The adhesive sets clear for a neat result.
- SIMPLE APPLICATION – Apply a thin layer to dry surfaces, join the pieces, and keep them in position.
- PACKAGE CONTENTS – Includes one 30g bottle and three applicator tips. Initial set takes 15 seconds. Allow 12 hours before use.
Common mistakes to avoid
- Assuming all silicone rubber is the same: silicone type and cure chemistry can affect compatibility.
- Choosing by a single strength number: test method, substrate pair, cure conditions, and joint geometry matter.
- Using a primer without checking the system: a primer’s process and compatible adhesive are product-specific.
- Confusing handling with full cure: a bond that can be handled may not have reached its stated full cure.
- Ignoring product-use limits: PR100 and AC79 are labeled industrial/occupational use only, not consumer products.
- Skipping a test on an uncertain material: Smooth-On recommends a small test application when suitability is in question.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
