Frequently Asked Questions

Q. What is rubber vulcanization ?
A. Vulcanization is irreversible; similar to thermoset plastics and in contrast to thermoplastic processes; as most modern polymers that are injection molded.
Typical vulcanization is done with temperature and pressure, an example: Passenger tires,
Vulcanized for 10 minutes at 170° C (338° F.)

Q. What are AS-568A O-Rings ?
A. Aerospace Standard 568 published by the S.A.E. (Society of Automotive Engineers), is a chart of “-xxx” dash numbers of standard molded O-Ring sizes.

Q. What temperature do rubber vulcanization adhesives cure ?
A. Normally 325° F. to 340° F., however EB bonders are set to 390° F., allowing heat to transfer to the center of the bond, since rubber has a low heat conduction value.

Q. What are Die-Sets made of ?
A. Aluminum alloy for many reasons, aluminum is easily machined, has a high heat conduction value and is corrosion resistant.

Q. Which bonder is best for extruded shapes ?
A. The “PB” Pneumatic Bonder has easily changeable die-sets, the die-set can be machined to suit any shape; “U”, “L”, “V” or irregular configurations.

Q. Why do large cross section O-Ring cord take longer to bond ?
A. Rubber is basically an insulator, having a low heat conduction value, therefore large cross section rubber will take longer for heat to penetrate to the rubber cord center.

Q. Why do solvents in liquid adhesives have to dry completely ?
A. Solvents left in a bond joint will eventually dissolve the rubber resulting in an poor bond.

Q. How do your bonders compensate for the tolerance range of the rubber cord diameter ?
A. Models EB and MB have a screw and nut adjustment of the toggle clamp to increase or decrease the clamping force. Model PB clamping force is controlled pneumatically by changing the air pressure.

Q. Why is it important to refrigerate rubber adhesive ?
A. A sealed container and cool temperature will minimize the solvent evaporation, thereby Increasing the shelf life. Certain rubber adhesives will partially cure at room temperature and will not allow for a complete bond at 325° F.

Q. Why are there two adhesives available: A liquid rubber adhesive and an uncured spreadable adhesive ?
A. It is a matter of preference: The liquid rubber adhesive is applied easily but takes longer for the solvent to evaporate. The uncured spreadable adhesive must be applied mechanically by spatula or small knife but can be put into the die-set without drying time.
NOTE:Both adhesive types are of the same basic rubber compound.

Q. Why do you stress the importance of a clean square cut of the rubber cord?
A. The adhesive will adhere better on a clean surface, a square cut will provide good matching of both cord ends when put into the die-set.

Q. Are vulcanized O-rings recommended for dynamic applications?
A. NO.
NOTE: Each user bears full responsibility for making its own determination as to the suitability of RSF Adhesives for its own particular use. Each user must identify and perform all tests to assure that its finished parts incorporating RSF Adhesives will be suitable for your end-use conditions.

Q. Why do you recommend a second coat of liquid rubber adhesive?
A. The initial coat can be absorbed in the rubber cross section, a second coat provides additional adhesive, especially for covering the outer corner, very important for eliminating gaps in the bond. Remember: More is better.

Q. How can I keep my rubber bonded parts clean?
A. If your table area is dirty you can build a bracket to hold the extruded rubber above the bonder, similar to the brackets designed for the MB unit. Click on the Accessories section to view these products.

Q. Can I use too much adhesive when bonding cord stock?
A. Excess bonding adhesive will form as flash on your part, this usually indicates a complete bond. Do not pull the flash off, use a flush trimming pliers. Wait for the bond to fully cure and cool before trimming. Click on the Accessories section to view this item.

Q. How can I eliminate parts that stick to the die-set?
A. Using a thin high temperature Teflon pressure sensitive tape to line the groove of the die-set.

Q. What are the largest cross section rubber extrusions a bonder can accommodate?
A. Click on the Die-Set information section.

Q. What are the smallest O-Rings that can be made ?
A. Click on the Die-Set information section.

Q. How can I test a bonded rubber part ?
A. ASTM D 1257 describes non destructive pull tests, always allow 24 hours before doing this test.

NOTE: Please contact RSF for the answer to a question not listed here.