Requirements for Silicone and Diluent Selection in Small Font Dispensing for Silicone Labels
Small font dispensing (fine lines, small letters, precision logos) is a high-precision process in the production of silicone labels. It has extremely high requirements for the compatibility of silicone raw materials and diluents. Improper selection will easily lead to problems such as broken glue, edge seepage, burrs, blurred outlines, incomplete curing, poor washing resistance, and insufficient adhesion, directly resulting in product scrappage. The following are complete and standardized selection requirements, covering core standards, selection rules, operation taboos and quality control points.
1. Requirements for Special Silicone Selection for Small Font Dispensing
Prioritize the use of special silicone for precision dispensing of textile labels, especially for heat-transfer/sew-on labels of clothing, shoes and hats. It must meet the core needs of small font molding, washing resistance and skin-friendly fitting, and ordinary silicone for large fonts/thick lines is strictly prohibited.
1.1 Mandatory Requirements for Core Performance
Curing Type: Preferred addition-molded room temperature/heating curing silicone. It features uniform curing speed, no by-products, and no fabric corrosion, making it the exclusive choice for small fonts of textile silicone labels. Condensation-cured silicone is prohibited for high-end wearable products.
Viscosity Parameter: Moderate original viscosity, suitable for precision needles without excessive dilution. Recommended original viscosity: 10000-18000cps. It has smooth fluidity, avoiding needle clogging and rapid sagging deformation.
Hardness Standard: Strictly controlled at 40-50 Shore A, balancing the stiffness of small font outlines and fabric fitting. It is soft and bending-resistant, without cracking or deformation after repeated washing. Excessively high hardness leads to brittle fracture, while excessively low hardness causes collapsed edges and blurring.
Excellent Thixotropy: Good anti-sagging performance, quick shaping after dispensing. Small font lines have clear edges and neat outlines, no edge seepage or diffusion, ensuring the fineness of patterns and texts.
Adhesion and Weather Resistance: Good compatibility with textile fabrics, hot melt adhesives and back adhesives, firm bonding. It passes multiple washing and friction tests, without falling off, yellowing or stickiness, complying with the durability standards for garment accessories.
Eco-friendly and Non-toxic: Free of heavy metals and pungent odors, passes textile environmental protection testing, non-irritating to skin, suitable for close-fitting clothing such as children's wear and underwear.
1.2 Taboos for Silicone Selection
It is forbidden to use industrial-grade silicone with high viscosity and high hardness. Such raw materials have poor fluidity, cannot adapt to fine needles for small fonts, and are prone to broken glue, missing strokes and incomplete filling.
It is forbidden to use low-quality silicone that shrinks easily and deforms after curing, to avoid size deviation and edge distortion of small font patterns.
Prioritize special supporting silicone of the same brand to reduce subsequent compatibility issues of diluents and ensure production stability.
2. Requirements for Diluent Selection for Small Font Dispensing
Diluents are only used to fine-tune silicone viscosity and improve glue dispensing fluency. The core principles are special matching, small dosage, slow volatilization and no residue. Random use of general organic solvents is strictly prohibited to avoid damaging silicone properties.
2.1 Core Selection Standards
Complete System Matching: Addition-molded silicone must be matched with special active diluent for addition-molded silicone. Mixing with condensation-cured diluent is strictly prohibited, and general solvents such as acetone, alcohol, toluene and xylene cannot be used to prevent silicone poisoning and incomplete curing.
Slow Volatilization and Low Odor: Choose slow-volatile diluents to prevent needle clogging caused by rapid solvent volatilization during dispensing, and avoid edge seepage and burrs of small fonts due to rapid solvent volatilization, ensuring clean and tidy lines.
High Dilution Efficiency: Reduce viscosity with a small amount of addition without excessive use, retaining the original hardness, adhesion and washing resistance of silicone to the maximum extent without affecting the molding quality of small fonts.
No Residue and No Corrosion: Solvent volatilizes completely or participates in cross-linking reaction after curing, leaving no residue. The surface of small fonts is smooth and flat, without stickiness, yellowing or fabric damage.
2.2 Addition Ratio and Operation Requirements
Strictly Control Addition Ratio: Follow the principle of "less is more, add in small amounts multiple times". The addition ratio for small font dispensing is controlled at 3%-8%, and the maximum shall not exceed 10%. Excessive addition will cause a sharp drop in silicone hardness, collapsed deformation of small fonts, poor adhesion and falling off after washing.
Stir evenly at low speed after dilution to avoid mixing a large number of bubbles caused by high-speed stirring. Bubbles will lead to missing corners, broken strokes and surface pits of small fonts. Let stand for 5-10 minutes for complete defoaming after stirring, then start dispensing.
Use the prepared glue as soon as possible to avoid viscosity recovery caused by long-term volatilization of diluent, which affects the stability of glue dispensing. It is recommended to prepare and use immediately to reduce storage time.
3. General Production Precautions
Key Quality Control Points
Before mass production, a small trial must be conducted to confirm the ratio of silicone and diluent, and dispensing parameters. Test the molding effect, curing state and washing resistance of small fonts, and start mass production only after passing the test.
Small font dispensing is suitable for precision dispensing needles of 0.15-0.3mm, with low pressure and slow glue output parameters, matched with high-quality diluents to ensure continuous lines and uniform thickness.
It is strictly forbidden to add excessive diluent for fluidity. Adjust in small amounts multiple times instead of adding all at once to avoid mass product scrappage.
Store the unused prepared glue in a sealed and refrigerated manner to prevent viscosity changes and curing. Stir evenly and check the state before reuse.