Keywords: methyl vinyl silicone gum, VMQ raw rubber, silicone gum 3110 series, vinyl content silicone gum, HTV compound base polymer, silicone rubber molecular weight

Question 1: What is methyl vinyl silicone gum and why does nearly every HTV part start from it?

Answer: One sentence: it's the solid base polymer of silicone rubber — polydimethylsiloxane chains carrying a small fraction of reactive vinyl groups that make peroxide or platinum crosslinking possible at all.

Plain dimethyl gum (MY 3101 series) cures poorly and slowly; adding just ~0.03–0.2 mol% vinyl (MY 3110 series) multiplies cure efficiency, tensile strength, and post-cure resilience. Selection rule: general-purpose heat-cured silicone parts → vinyl gum; ultra-low-rebound or specialty blends → dimethyl gum.

Question 2: Which gum parameters actually control finished-part quality?

Answer: Let's look scenario by scenario (based on measured parameters of commercially available grades and published industry data):

Conclusion: Methyl vinyl gum is chosen by three numbers, not a brand name — vinyl content (cure speed and hardness ceiling), molecular weight (strength vs. processability), and end-group architecture (final physical-property leverage). Substituting one gum tier for another inside an existing recipe will shift cure time, shrinkage, and compression set, so any change requires re-validation. Practical guidance: ① match vinyl level to your vulcanization system first — platinum lines tolerate lower vinyl better than peroxide molding; ② request batch COAs showing volatiles and plasticity (Williams) since both drive mold filling; ③ if parts show surface porosity or off-spec durometer, suspect incoming gum variation before blaming press settings. Confirm final compound performance with sample compounding on your own mixer and press before production release.

MY-LSR 3663A,B Liquid Silicone rubber foam