Why do we need to use silicone hot melt film to make silicone heat transfer trademarks?
In the silicone thermal transfer trademark process, silicone hot melt film (or silicone-compatible hot melt adhesive film) is the key material to ensure strong adhesion, durability and pattern integrity. The following are the core reasons and scientific basis:
1. The difficulty of bonding silicone with ordinary materials
Chemical inertness of silicone:
Silicone (mainly composed of SiO₂·nH₂O) has low surface energy and is non-polar. It has very poor adhesion to ordinary hot melt adhesives (such as EVA and PES) and is easy to fall off.
Failure cases of traditional adhesive films:
If ordinary hot melt films are used, there will be stratification between the silicone ink layer and the fabric, and the trademark will warp and crack after washing or friction.
2. Unique advantages of silicone hot melt films
(1) Chemical compatibility
Modified formula:
Hot melt films designed specifically for silicone (such as silicone-modified TPU or PA-based adhesive films) contain polar groups that can form chemical bonds or physical anchors with silicone molecules.
Case:
The urethane group (-NH-COO-) in TPU hot melt film forms a hydrogen bond with the hydroxyl group (-OH) of silicone.
(2) High temperature resistance
High temperature requirement for silicone curing:
Silicone ink needs to be vulcanized (cross-linked reaction) at 130–160°C, and ordinary EVA film will melt excessively or decompose at this temperature.
Solution:
PA or high-temperature TPU hot melt film can withstand temperatures above 160°C, and silicone curing and bonding can be completed simultaneously.
(3) Elastic matching
High elasticity of silicone:
Silicone elongation can reach more than 300%, and ordinary film (such as PES) is easy to break.
Elastic adaptation of TPU:
TPU hot melt film has an elongation of >500%, and deforms synchronously with silicone, which is suitable for elastic fabrics such as sportswear and swimsuits.
3. Process synergy
One-step transfer:
Silicone hot melt film and silicone ink layer are melted synchronously during hot pressing:
Lower layer: hot melt film penetrates the fabric fiber.
Upper layer: cross-linked with silicone ink.
Compared with traditional methods:
If a special film is not used, additional primer (such as Primer) is required, which increases costs and process complexity.
4. Improved durability
Test data:
Performance Ordinary EVA film + silicone Silicone special TPU film
Number of water washings (times) <20 times peeling off >50 times without abnormality
Peel strength (N/cm) ≤1.5 ≥4.0
5. Application scenario verification
High-demand fields:
Sports brands: Nike and Adidas silicone trademarks generally use TPU/PA hot melt film.
Outdoor equipment: Weather resistance (-30°C~120°C) is required, and PA-based adhesive film is the first choice.
Conclusion
Silicone hot melt film solves the bottleneck of bonding between silicone and textiles through chemical modification, high temperature resistant formula and elastic matching. It is an essential material for high adhesion, long life and low-cost mass production of silicone thermal transfer trademarks. When selecting, you need to match the film type (TPU/PA) according to the fabric type (elasticity/rigidity) and temperature requirements.