Molding Rubber | McMaster-Carr

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57 Products

Casting Compounds

Capture intricate details when creating prototypes, molds, and linings with these easy-to-mix two-part compounds. This urethane rubber is water and abrasion resistant.

View our selection of release agents.

	Time to Demold, hr.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Urethane Rubber





	Soft
	Durometer 20A	15	168	5	77	180	0.1%	Black	Yes	25	1	0000000	000000
	Durometer 20A	15	168	5	77	180	0.1%	Black	Yes	250	10	0000000	000000



			Hard
			Durometer 40A	15	168	5	77	180	0.1%	Black	Yes	25	1	0000000	00000
			Durometer 40A	15	168	5	77	180	0.1%	Black	Yes	250	10	0000000	000000
			Durometer 60A	15	168	2	77	180	0.1%	Black	Yes	25	1	0000000	00000
			Durometer 60A	15	168	2	77	180	0.1%	Black	Yes	250	10	0000000	000000
			Durometer 80A	15	168	3	77	180	0.1%	Black	Yes	6	0.25	0000000	00000
			Durometer 80A	15	168	3	77	180	0.1%	Black	Yes	25	1	0000000	00000
			Durometer 80A	15	168	3	77	180	0.1%	Black	Yes	250	10	0000000	000000
			Durometer 94A	15	168	2	77	180	0.1%	Black	Yes	25	1	0000000	00000
			Durometer 94A	15	168	2	77	180	0.1%	Black	Yes	250	10	0000000	000000
			Durometer 60D	15	168	2	77	180	0.1%	Black	Yes	25	1	0000000	00000
			Durometer 60D	15	168	2	77	180	0.1%	Black	Yes	250	10	0000000	000000
			Durometer 75D	15	168	2	77	180	0.1%	Black	Yes	25	1	00000000	00000
			Durometer 75D	15	168	2	77	180	0.1%	Black	Yes	250	10	00000000	000000
			Durometer 85D	5	2	1.5	77	180	0.1%	Green	Yes	80	5	000000	00000
			Durometer 85D	5	2	1.5	77	180	0.1%	Green	Yes	320	20	000000	000000

Quick-Set Casting Compounds

Create detailed rubber shapes that are ready to use in fifteen minutes or less. Unlike traditional casting compounds, which can take up to 24 hours to set, these compounds harden after two minutes, and can be removed from molds within fifteen. Use them to make your own prototypes, molds, and linings.

Casting Compounds

Silicone Rubber

Soft—Soft silicone rubber is more flexible and easier to peel off of molds than hard silicone rubber, especially when making complex shapes.

Hard— Hard silicone rubber holds its shape better than soft silicone rubber, so small ridges and channels are less likely to collapse or deform while making molds.

69° F Cure Temperature—Combine acrylic plastic or silicone rubber with a 69° cure temperature compounds in different ratios to adjust the consistency from thin to thick. Thin mixtures are easier to pour and better for filling small crevices.

70° F Cure Temperature—Silicone rubber with a 70° cure temperature compounds are a putty that you can mix with your hands and form into any shape. Press an object into these compounds to create a mold for casting duplicates. They do not shrink as they dry, so textures and other fine details are captured faithfully.

	Time to Demold, min.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Silicone Rubber





	Soft
	Durometer 27A	2	15	15	70	650	0%	Light Blue	Yes	4	0.2	0000000	000000
	Durometer 27A	2	15	15	70	650	0%	Light Blue	Yes	46	2.2	0000000	000000
	Durometer 30A	2	10	10	69	250	0%	Green	Yes	8	0.5	0000000	00000
	Durometer 30A	2	10	10	69	250	0%	Green	Yes	23	1.1	0000000	000000



			Hard
			Durometer 40A	2	15	15	70	600	0%	Green	Yes	4	0.2	0000000	00000
			Durometer 40A	2	15	15	70	600	0%	Green	Yes	46	2.2	0000000	000000
			Durometer 50A	2	10	10	69	250	0%	Light Blue	Yes	13	0.8	0000000	000000
			Durometer 50A	2	10	10	69	250	0%	Light Blue	Yes	32	1.75	0000000	000000

Casting Compounds with Dispensing Gun

Compounds with dispensing gun come ready to use—no mixing required—and won’t leave a mess.

Soft—Soft silicone rubber is more flexible and easier to peel off of molds than hard silicone rubber, especially when making complex shapes.

Hard— Hard silicone rubber holds its shape better than soft silicone rubber, so small ridges and channels are less likely to collapse or deform while making molds.

	Hardness	Time to Harden, min.	Time to Cure	Time to Demold	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Wt., lb.	Includes		Each
Silicone Rubber


	Soft	Durometer 30A	2	10 min.	10 min.	69	250	0%	Green	No	4	Carrying Case, Six each 3 cu. in. Disposable Cartridges	0000000	0000000
	Soft Hard	Durometer 30A Durometer 55A	2	10 min. 6 min.	10 min. 6 min.	69	250	0%	Green Orange	No	4	Carrying Case, Six each 3 cu. in. Disposable Cartridges	0000000	000000
	Hard	Durometer 55A	2	6 min.	6 min.	69	250	0%	Orange	No	4	15 Disposable Nozzles, 2 Snap-On Nozzles, Carrying Case, Six each 3 cu. in. Disposable Cartridges	0000000	000000

See-Through Casting Compounds

Create transparent molds to monitor fill levels, differentiate parts at a glance, and avoid damaging parts when cutting the mold away. These casting compounds are two parts that activate when mixed.

View our selection of release agents.

Urethane Rubber—Urethane rubber compounds are tougher than silicone rubber compounds, so your molds will last longer. Although not required, curing urethane rubber molds inside a vacuum chamber improves their clarity. By removing trapped air bubbles, the chamber prevents the finished mold from looking speckled.

Silicone Rubber—Silicone rubber compounds handle higher temperatures than urethane rubber compounds—up to 570° F. Silicone rubber also cures faster than urethane rubber, and it won't shrink as it cures, which means you won't need to guess at the final size of your mold. Because silicone rubber compounds trap air bubbles when mixed, they must be cured inside a vacuum chamber. The chamber removes the trapped air bubbles, strengthens the mold, and improves its clarity.

	Time to Demold	Cure Temp.	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Urethane Rubber





	Hard
	Durometer 40A	6	144 hr.	2 hr.	77° F	180	0.8%	Clear	Yes	25	1	00000000	000000
	Durometer 60A	6	144 hr.	2 hr.	77° F	180	0.8%	Clear	Yes	25	1	00000000	00000
	Durometer 80A	6	144 hr.	2 hr.	77° F	180	0.8%	Clear	Yes	25	1	0000000	00000
	Durometer 75D	6	144 hr.	2 hr.	77° F	180	0.8%	Clear	Yes	25	1	0000000	00000

	Silicone Rubber





					Hard
					Durometer 40A	10	1.5 hr. 30 min.	1.5 hr. 30 min.	77° F 120° F	570	0%	Blue	Yes	57	2.2	0000000	000000

Easy-Form Casting Compounds

Combine the liquid components to form a putty that can be molded into or around any shape. Use these compounds to capture intricate details when creating prototypes, molds, and linings.

View our selection of release agents.

	Time to Demold, hr.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Urethane Rubber





	Hard
	Durometer 60A	15	168	3	75	180	Not Rated	Dark Gray	Yes	25	1	0000000	000000
	Durometer 60A	15	168	3	75	180	Not Rated	Dark Gray	Yes	100	4	0000000	000000
	Durometer 85A	15	168	3	75	180	Not Rated	Black	Yes	25	1	0000000	00000
	Durometer 85A	15	168	3	75	180	Not Rated	Black	Yes	100	4	0000000	000000
	Durometer 60D	15	168	3	75	180	Not Rated	Dark Gray	Yes	25	1	00000000	00000
	Durometer 60D	15	168	3	75	180	Not Rated	Dark Gray	Yes	100	4	00000000	000000

Fine-Detail Casting Compounds

Replicate even the most complex details when creating prototypes, molds, and linings. This easy-to-mix two-part compound flows smoothly into crevices. Cast up to _1/2" in thickness at a time.

View our selection of release agents.

	Time to Demold, hr.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Urethane Rubber





	Hard
	Durometer 80D	20	168	4	72	134	0.3%	White	Yes	49	2	0000000	000000
	Durometer 80D	20	168	4	72	134	0.3%	White	Yes	395	16	00000000	000000

Machinable Casting Compounds

After these compounds cure, they're tough enough to be machined. They are easy-to-mix two-part compounds that capture intricate details when creating prototypes, molds, and linings.

View our selection of release agents.

	Time to Demold, min.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Aluminum-Filled Urethane





	Hard
	Durometer 84D	6	168	90	72	130	1.5%	Gray	Yes	72 1/2	5	00000000	0000000
	Durometer 84D	6	168	90	72	130	1.5%	Gray	Yes	290	20	00000000	000000

Long-Life Casting Compounds

Create rubber molds that retain their shape for decades—they won’t soften, degrade, or warp, so you can continue to replicate intricate parts. Because these compounds don’t shrink as they cure, they are more accurate and predictable than other compounds.

View our selection of release agents.

	Time to Demold, hr.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Urethane Rubber





	Hard
	Durometer 45A	60	24	16	77	200	0%	Yellow	Yes	58	2.2	0000000	0000000

Food and Beverage Casting Compounds

These food-grade compounds comply with FDA 21 CFR. They are easy-to-mix two-part compounds that capture intricate details when creating prototypes, molds, and linings.

View our selection of release agents.

	Time to Demold, hr.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Food Industry Std.	Volume, cu. in.	Wt., lb.		Each
Urethane Rubber





	Hard
	Durometer 40A	8	12	2	120	180	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	25	1	0000000	000000
	Durometer 60A	8	12	2	120	180	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	25	1	0000000	00000
	Durometer 60A	8	12	2	120	180	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	250	10	0000000	000000
	Durometer 78A	4	12	2	120	180	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	25	1	0000000	00000
	Durometer 88A	4	12	2	120	180	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	25	1	0000000	00000
	Durometer 88A	4	12	2	120	180	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	250	10	0000000	000000
	Durometer 75D	5	12	2	120	180	5%	White	Yes	FDA Compliant 21 CFR 175.105, FDA Compliant 21 CFR 177.1680	25	1	0000000	00000

Chemical-Resistant Casting Compounds

This silicone rubber compound offers good resistance to acids, oils and salt water. Use it to capture intricate details when creating prototypes, molds, and linings with this easy-to-mix two-part compound. It is a durable and tear-resistant silicone rubber, which easily demolds.

View our selection of release agents.

	Time to Demold, hr.	Cure Temp., ° F	Max. Temp., ° F	Shrinkage	Color	Mixing Req.	Volume, cu. in.	Wt., lb.		Each
Silicone Rubber





	Hard
	Durometer 65A	120	24	16	78	400	0%	Blue	Yes	22	1	0000000	000000
	Durometer 65A	120	24	16	78	400	0%	Blue	Yes	242	11	0000000	000000