MQ Silicone Resin (M-Unit + Q-Unit Branched Silicone Resin): Reinforcement Resin for High-Modulus Silicone and Silicone PSA Tackifier
SEMITECH MQ silicone resin is the highly-branched silicone resin built from M-units (trimethylsilyl, monofunctional from HMDS) and Q-units (silicate, tetrafunctional from TEOS). Used as reinforcement filler in LSR and HCR silicone elastomer (boosts tensile strength + tear resistance), as tackifier in silicone pressure-sensitive adhesive (skin-contact medical, electronic assembly), and as carrier resin in silicone-based release coatings. Solid powder + 60% xylene/toluene solution forms.
Contents
| M:Q ~0.6–1.0 | 2,000–10,000 | 60% solution |
|---|---|---|
| Mole ratio | MW (g/mol) | Standard form |
Chemistry & Specifications
M (Me₃Si) endcaps + Q (silicate) core; soluble in toluene/xylene/IPA; brittle solid in dry form.
MQ silicone resin is a highly-branched silicone polymer built from two types of structural units in the silicone-resin nomenclature: M-units (trimethylsilyl, –OSi(CH₃)₃, monofunctional, derived from HMDS) and Q-units (silicate, –O₄SiO–, tetrafunctional, derived from TEOS). The polymer structure is a Q-unit-rich silicate core with M-unit trimethylsilyl groups capping the surface — the M:Q mole ratio (typically 0.6–1.0) controls molecular weight, processability, and elastic vs viscous properties of the finished resin. Higher M:Q ratio (closer to 1.0) gives lower-MW resins (3,000–5,000 g/mol) suitable for liquid silicone and PSA applications; lower M:Q (0.6–0.7) gives higher-MW resins (8,000–10,000 g/mol) suitable for hard-coating and reinforcement applications.
SEMITECH supplies MQ resin in two physical forms: (1) solid powder at ≥98% active resin (water content ≤0.5%, residual monomer ≤2%) — supplied for compounding into HCR/HTV silicone gum where the dry form is required for mill-mix processing; (2) 60% by weight solution in xylene or toluene solvent — supplied for liquid silicone PSA, optical-grade silicone resin, and any application requiring fast in-formulation dissolution. CoA verification: M:Q ratio (¹H-NMR or FT-IR ratio of methyl peaks to silicate peaks, target ±0.05 of nominal); MW (GPC, target ±15% of grade specification); residual silanol content (FT-IR or titration, target ≤0.5%). Multiple grades are available with M:Q ratios optimised for specific application categories.
Reinforcement Mechanism: MQ as Functional Filler in Silicone Elastomer
MQ resin co-disperses with PDMS, provides Q-rich rigid domains that enhance tensile + tear; alternative/complement to fumed silica.
In silicone elastomer compounds (LSR, RTV-2, HCR/HTV gum), MQ silicone resin functions as a “functional filler” — a polymeric additive that integrates into the silicone matrix as nano-scale rigid domains, providing reinforcement through a different mechanism than mineral filler (fumed silica, calcium carbonate). The MQ resin partitions into the silicone polymer matrix as 5–50 nm domains; the silicate (Q-unit) core provides rigid reinforcement; the trimethylsilyl (M-unit) surface provides chemical compatibility with the surrounding PDMS matrix.
Performance compared to fumed silica reinforcement: at equivalent loading (typically 15–35% on total formulation), MQ resin provides similar tensile strength uplift (10–18 MPa cured tensile vs 4–8 MPa for unreinforced silicone) but slightly different tear-resistance profile (lower trouser-tear strength, higher die-C tear strength) and meaningfully lower compound viscosity (since MQ resin disperses molecularly rather than as discrete particles). Many production-scale formulations blend the two — fumed silica at 15–20% as primary reinforcement plus MQ resin at 5–15% as supplementary functional filler — to optimise the property balance.
- Loading 15–35% MQ resin in LSR — high-modulus medical, automotive, industrial sealing applications
- Loading 30–60% MQ resin in silicone PSA — tackifier for skin-contact medical, electronic assembly, removable industrial
- Loading 5–20% MQ resin in HCR gum — supplementary reinforcement alongside fumed silica primary filler
- Loading 50–80% MQ resin in hard coating — silicone hard coating for plastic substrates, antifog optical surfaces
Applications: PSA Tackifier, LSR Reinforcement, Hard Coating, Defoamer Resin
Silicone PSA tackifier (largest), high-modulus LSR reinforcement, silicone hard coating, defoamer resin component.
Silicone pressure-sensitive adhesive (PSA) tackifier is the largest single application — skin-contact medical adhesive (wound dressings, transdermal patches, scar treatment sheets), electronic assembly adhesive (high-temperature aircraft electronics, semiconductor equipment), and removable industrial labels. MQ resin at 30–60% paired with low-MW vinyl-PDMS or OH-PDMS forms a silicone PSA with the unique combination of biocompatibility, removable + repositionable adhesion, and resistance to temperature extremes (operational from −40°C to +200°C+). The MQ resin provides the cohesive strength that allows the adhesive to be removed cleanly without leaving residue.
High-modulus LSR reinforcement uses MQ resin at 15–35% as primary or supplementary filler in LSR formulations targeting tensile 12+ MPa — automotive sealing components subject to high deformation, industrial seals operating at high pressure, sports protective equipment requiring impact resistance. Silicone hard coating for plastic substrates (PMMA, PC, PET) uses MQ resin at 50–80% as the primary film-forming polymer in solvent-borne coatings that cure to a glassy thin film providing scratch-resistant, antifog, and easy-clean surface modification. Defoamer resin component uses MQ resin at 1–5% in silicone defoamer compounds (alongside hydrophobic silica and PDMS fluid) — the resin provides additional surface-active functionality that improves spreading kinetics and bubble-rupture nucleation on certain difficult-to-defoam aqueous formulations.
Procurement, Storage and Quality Control
CoA per shipment with M:Q ratio + MW verification; powder + 60% solution forms; 24-month shelf life.
SEMITECH issues a CoA on every batch with: M:Q ratio (¹H-NMR or FT-IR, target ±0.05 of nominal grade), molecular weight (GPC, target ±15%), active resin content (powder: ≥98%; solution: 60.0 ± 0.5%), water content (Karl Fischer, target ≤0.5% for powder, ≤0.1% for solution), residual silanol (FT-IR or titration, target ≤0.5%), residual silanol-monomer impurity (target ≤2%), and APHA colour. Standard packing: powder form in 25 kg HDPE-lined fibre drums; 60% solution form in 200 kg HDPE-lined steel drums (xylene or toluene solvent). MOQ 25 kg per grade (powder) or 200 kg (solution). Lead time 4–6 weeks ex-Zhejiang to Asia ports for stocked grades, 6–8 weeks to Europe and North America after sea freight (specialty product, lower stock levels than other intermediates).
Storage: powder form is stable under ambient conditions in original sealed packaging (avoid moisture; stored shelf life 24 months sealed at <30°C); solution form requires segregated flammable storage (xylene flash point 27°C, toluene 4°C — Class IB flammable; standard flammable-storage cabinet required). Shelf life 24 months sealed for both forms; opened powder consumable within 12 months without significant property drift; opened solution consumable within 90 days (solvent loss on extended ambient exposure shifts active concentration). Cost positioning: MQ resin Q1 2026 ex-Zhejiang spot CNY 80,000–120,000/MT (USD 11.2–16.8/kg) for standard grades; specialty grades (high-purity for medical PSA; high-MW for hard coating; M:Q-tuned for PSA cohesion) at 30–50% premium. Health and regulatory: REACH-registered for industrial use; FDA 21 CFR 175.300 listed for indirect food-contact in adhesive components; specific medical-grade variants with USP Class VI compliance available on request; mild skin and eye irritant; standard PPE — nitrile gloves, splash goggles. SDS in EU/GHS format issued with every shipment.
MQ silicone resin is the M-unit + Q-unit branched silicone resin — functional filler for high-modulus LSR/HCR elastomer reinforcement, tackifier for skin-contact silicone PSA, primary film-former for silicone hard coatings. Available in solid powder and 60% xylene/toluene solution forms. Cost premium over fumed silica reinforcement justifies use in PSA, hard coating, and high-modulus elastomer applications.
MQ Silicone Resin Specification Sheet
SEMITECH stocked grades; CoA per batch with M:Q ratio and MW verification.
| Property | Powder Form | 60% Solution Form |
|---|---|---|
| Form | White-to-pale-yellow brittle solid | Pale-yellow viscous solution |
| Active resin content | ≥98% | 60.0 ± 0.5% |
| M:Q mole ratio | 0.6–1.0 (grade-dependent) | 0.6–1.0 (grade-dependent) |
| Molecular weight (Mw) | 3,000–10,000 g/mol | 3,000–10,000 g/mol |
| Solvent | None (solid) | Xylene or toluene |
| Water content | ≤0.5% | ≤0.1% |
| Residual silanol | ≤0.5% | ≤0.3% |
| Solubility | Soluble in toluene, xylene, MEK, IPA | Diluted with toluene, xylene, MEK |
| Density (25°C) | ~1.10 g/cm³ (powder) | 0.95–1.00 g/cm³ (solution) |
| Viscosity (25°C) | N/A (solid) | 50–200 cP |
| Flammability | Non-flammable (solid) | Class IB flammable (xylene/toluene) |
| Glass transition Tg | ~100°C | N/A |
| Packaging | 25 kg HDPE-lined fibre drum | 200 kg HDPE-lined steel drum |
| Shelf life | 24 months sealed below 30°C | 24 months sealed below 30°C |
FAQ
+When should I add MQ resin to my LSR formulation, and at what loading?
Add MQ resin when your LSR formulation needs higher tensile and tear properties than fumed silica reinforcement alone can deliver — typically applications targeting tensile 12+ MPa, elongation 250%+, and tear strength 25+ N/mm: automotive sealing components subject to high deformation, industrial seals operating at high pressure, sports protective equipment, medical-device elastomers requiring durability. Recommended loading: start at 15% MQ resin on total formulation as a supplementary filler alongside the existing fumed silica reinforcement (typically 15–20% silica + 15% MQ). Adjust based on cured-elastomer property testing — higher MQ (20–35%) gives further tensile uplift but at increasing cost; verify the cost-benefit aligns with the application requirement before scaling. Some specialty LSR formulations replace fumed silica entirely with MQ resin (35% MQ alone) — gives lowest compound viscosity but at higher cost than silica + MQ blend.
+How is silicone PSA different from acrylic or rubber-based PSA?
Silicone PSA uses MQ resin + low-MW silicone polymer to form an adhesive with three properties that acrylic and rubber-based PSAs cannot match: (1) extreme temperature range — operational from −40°C to +200°C+ continuous (vs −20°C to +80°C for typical acrylic PSA, −20°C to +60°C for rubber PSA); (2) skin compatibility — biocompatible MQ silicone PSA is the standard for medical wound dressings, transdermal patches, scar-treatment sheets where the adhesive is in direct skin contact for hours to days; (3) clean-removal characteristic — silicone PSA peels cleanly from substrate without residue at end of use, even after extended adhesion (acrylic PSA typically transitions to permanent adhesion over time). Trade-offs: silicone PSA is 5–10× more expensive than acrylic PSA on a per-square-metre basis; bonds to fewer substrates (mostly works on smooth low-energy plastics, glass, and metal — does not bond well to porous paper or fabric); requires more careful surface preparation. Use silicone PSA only where its unique properties are required.
+Powder vs 60% solution — which form is right for my application?
Powder form for: HCR / HTV silicone gum compounding (mill-mix processing requires dry MQ resin); high-modulus elastomer where the gum-stage incorporation gives best dispersion; cost optimisation (powder ~5–10% lower per-kg cost than solution due to no solvent); shipping economics (60% solution carries 40% solvent dead-weight). Solution form for: LSR formulation work where in-situ dissolution time matters (powder requires 30+ min dissolution at 60°C; solution is ready-to-use); silicone PSA manufacture where the formulation already includes solvent for application (the MQ solution solvent integrates with the formulation solvent); hard-coating manufacture where MQ resin is dissolved in coating solvent for spray or dip application; small-scale R&D and pilot production where convenience trumps cost. Many production-scale silicone PSA manufacturers receive MQ as solution and use it directly; production-scale HCR/HTV manufacturers receive powder for mill-mix incorporation. Engage SEMITECH technical service for application-specific form recommendation.