I. MQ Silicone Resin

MQ silicone resin, a uniquely structured organosilicone resin, is a silicone elastomer with a three-dimensional spherical structure. It is produced via a co-hydrolysis-polycondensation reaction between organosilicon compounds containing tetrafunctional siloxane units (Q units) and organosilicon compounds containing monofunctional siloxane units (M units). Its molar mass typically ranges from 1,000 to 8,000 g/mol, and it can exist in various states—from viscous fluids to solid powders. The material exhibits a hard and brittle texture and has a broad glass transition temperature (Tg) range.

By adjusting the ratio of M/Q units, it is possible to control the crosslinking density of the resin. As the M:Q ratio increases, the resin becomes more flexible; conversely, as the ratio decreases, a stiffer three-dimensional network structure is formed.

Generally speaking, MQ silicone resins exhibit a tightly packed, spherical structure with a double-layer configuration. The core of the sphere consists of cage-like SiO₂ (Q units) linked by Si—O chains, featuring a high density and a degree of polymerization ranging from 15 to 50. The shell of the sphere is composed of a lower-density layer of R₃SiO₁/₂ (M units).

II. Types of MQ Silicone Resins

MQ silicone resins come in various types due to the different organic groups R attached to the spherical shell.

When R is entirely methyl, it is referred to as methyl MQ silicone resin, or simply MQ silicone resin.

When part of R is H, the compound is referred to as hydrogen-containing methyl MQ silicone resin.

There are also methylphenyl MQ silicone resins, vinyl MQ silicone resins, phenyl MQ silicone resins, fluorine-containing MQ silicone resins, MDQ, MTQ silicone resins, and others. The performance and application scope of MQ silicone resins largely depend on the synthesis process conditions as well as the type and quantity of organic groups in the molecule—specifically, the molar ratio of M units to Q units. Among these organic groups, R primarily serves to enhance compatibility with other components and act as an adhesion promoter; while the SiO4/2 units mainly contribute to strengthening the composite material by improving its mechanical properties.

III. The Influence of MQ Silicone Resin Structure on Performance

The unique structure of MQ silicone resins endows the materials with a wide range of properties. Phenyl-substituted MQ silicone resins can significantly enhance the material's heat resistance and UV resistance, while the introduction of vinyl groups boosts their crosslinking reactivity, making them ideal for reinforcing addition-type silicone rubbers. Modification with fluorine-containing groups imparts excellent hydrophobicity and chemical stability to the resin, expanding its applications in specialized environments. The adjustment of the M/Q ratio directly influences the resin's polarity and hardness, thereby determining its suitability for use in coatings, adhesives, and electronic encapsulation materials. The synergistic design of different organic groups further optimizes the overall performance of MQ silicone resins, meeting diverse industrial needs. By precisely controlling the M/Q ratio and the types of organic groups, MQ silicone resins demonstrate irreplaceable advantages in fields such as transparent coatings, high-temperature resistant materials, and microelectronic packaging.

IV. Application Fields of MQ Silicone Resin

MQ silicone resin has a wide range of applications. In the optoelectronics field, it is used as specialized adhesives for eco-friendly, energy-saving lamp holders and sealing compounds for bulb sockets; in the paper printing and packaging industry, it serves as a coating agent for varnishing; in the construction waterproofing sector, thanks to its outstanding weather resistance and bonding performance, it is employed as an additive for exterior wall coatings; in the personal care industry, due to its excellent biocompatibility and film-forming properties, it is utilized as a stabilizing additive in hair gels and other products; in high-end electronic devices, it acts as a dielectric material and stress-buffering layer, enhancing the reliability of chip packaging. In the new energy sector, with its superior insulation performance and thermal stability, it is used as encapsulating material for photovoltaic modules and sealing material for power batteries, thereby improving system safety and durability. In the aerospace and extreme-environment equipment fields, its stability over a wide temperature range and low dielectric loss characteristics make it a critical component; its applications in flexible electronics and wearable devices are also gradually emerging, endowing these devices with outstanding performance.