The crosslinker and curing agent in screen printing silicone have the same essential function, both of which improve the material performance by constructing a three-dimensional network structure, but there are differences in the use scenarios of the terms, and the formula ratio directly affects the operating characteristics and curing effect. The following is a specific analysis:
1. Essential function: chemical commonality of crosslinkers and curing agents
Crosslinker
Definition: Connect linear polymer chains through chemical bonds (covalent bonds or ionic bonds) to form a three-dimensional network structure, improve material strength, heat resistance and chemical stability.
Mechanism of action:
Free radical reaction: such as organic peroxide decomposition to generate free radicals, which trigger polymer chain crosslinking.
Functional group reaction: Bifunctional groups (such as C=C, amino, carboxyl) react with polymer molecular chains to form crosslinking points.
Typical applications: rubber vulcanization (sulfur), polyurethane crosslinking (isocyanate), epoxy resin curing (amines).
Curing agent
Definition: Initiate polymer curing reaction under specific conditions (heat, light, catalyst), which is essentially a trigger for the crosslinking process.
Mechanism of action:
Condensation reaction: For example, silicone polymer reacts with curing agent to release by-products (such as alcohol) and form a cross-linked structure.
Addition reaction: For example, platinum catalyst catalyzes the hydrosilylation reaction to achieve by-product-free curing.
Typical applications: epoxy resin (amine curing agent), silicone (peroxide or platinum catalyst).
Conclusion: In chemical nature, cross-linking agents and curing agents both improve material performance through cross-linking reactions. The difference in terminology comes from industry habits (such as "vulcanizing agent" in the rubber industry and "cross-linking agent" in the coating industry).
2. Differences in formula ratios in screen printing silicone
The curing system of screen printing silicone is usually a two-component system (component A: silicone matrix; component B: curing agent/cross-linking agent). The formula ratio directly affects the operating characteristics and curing effect:
Low ratio formula (such as 10:1)
Features: The proportion of curing agent is low (such as 10 parts of silicone to 1 part of curing agent), the curing speed is fast, but the operation time is short.
Applicable scenarios:
Small batch production: manual screen printing or short-cycle orders require fast curing to improve efficiency.
High hardness requirement: Rapid cross-linking can form a high-hardness silicone layer, but some flexibility may be sacrificed.
Risk: Short operation time can easily lead to uncured or premature curing, and the mixing and printing speeds need to be strictly controlled.
High-ratio formula (such as 100:2)
Features: The curing agent accounts for a high proportion (such as 100 parts of silicone for 2 parts of curing agent), the curing speed is slow, but the operation time is longer.
Applicable scenarios:
Machine printing or large-area printing: Long operation time can avoid stratification or uneven curing of the rubber.
Complex pattern printing: Longer leveling time can achieve fine textures or three-dimensional effects.
Advantages: Low VOC emissions, in line with environmental protection standards (such as REACH, ROHS), suitable for high-end markets.
3. The influence of formula ratio on material properties
Mechanical properties
High-ratio formula: More complete curing, high cross-linking density, better hardness and wear resistance, but flexibility may be reduced.
Low-ratio formula: Low cross-linking density, better flexibility, but hardness and wear resistance may be insufficient.
Weather resistance
High-ratio formula: more complete curing, stronger resistance to high temperature and solvents, suitable for outdoor or harsh environments.
Low-ratio formula: weather resistance may decrease due to insufficient curing, which needs to be improved by additives.
Cost and efficiency
High-ratio formula: less curing agent is used, the cost per kilogram may be lower, but the production cycle is long.
Low-ratio formula: more curing agent is used, the cost per kilogram is higher, but it is suitable for short-cycle and high-efficiency production.