TECHNOLOGY | LASER MARKING
Right: An animal tag indelibly marked using Gabriel-Che- mie’s Maxithen laser marking additive
possible in the polymer matrix,” Evonik says. When irradiated by a laser, the metal
oxides absorb the energy and heat their immediate environment, which results in foaming or carbonisa- tion. In both cases, there is a locally confined change of refractive index, rendering the marking visible in a shade of grey that depends on the polymer and the laser parameters.
Right: These cosmetic bottles are decorated using laser marking additives from Gabriel-Chemie
Marking categories Italian compounder Lati says that thermoplastics can be divided into three general categories according to their ability to be marked: polymers such as polysulphone (PSU) and polyethersulphone (PES) that adequately absorb laser energy and conse- quently carbonise to produce a noticeable darken- ing of the area where the laser hits; thermoplastics such as styrenics and polyesters that absorb laser energy erratically and so also carbonise in an irregular way; and thermoplastics with low or negligible absorption such as polyamides, polyole- fins, acetals, and polyphenylene sulphide. In the case of the latter two groups it is necessary to use special pigments or additives to achieve good results. “Laser marking may be strongly influenced by the addition of fillers, reinforcers, special additives, self-extinguishing additives and other additives,” Lati says. “Contrary to what one might think, the pres- ence of fibreglass reduces the ability to be marked only slightly. Due to their intrinsic colour, some types of fillers or self-extinguishing additives may reduce the ability to be marked by laser. On the other hand, the additives in certain self-extinguishing systems may improve the contrast of laser marking.” Budenheim has developed a range of laser-sen- sitive ingredients that enables advanced high-con- trast laser marking and laser welding in a wide range of thermoplastics. It says the Budit L Series is both easy to add and to process. The additives also absorb NIR radiation and provide high transparency in the visible range. Depending on the energy level, different visual marks from bright to dark can be generated on the polymer surface. “Using a typical concentration of 0.1%-5.0%, the energy of the laser beam creates marks within 10 microns underneath the plastic surface,” Budenheim says. Budenheim marketing manager Henrike Scheel says the company has a number of promising new development projects for the product involving medical devices, food packaging and automotive back lights. Eckart says its Lasersafe 040 laser marking
64 COMPOUNDING WORLD | February 2018
PHOTO: GABRIEL-CHEMIE
additives (which like most other offerings use heavy metal-free pigments) enable “exception- al” contrasts and high quality at high speeds. The additives work with all standard laser technologies. “Lasersafe 040 is designed for plastics which are inherently poor for laser marking such as polyolefins as well as engineering plastics,” the company says. “Due to its excellent laser marking efficiency, even at low dosage levels, Lasersafe 040 offers good colour stability of the final
formulation.” The additives are supplied in pellet form so they can be handled and processed like regular colour masterbatches. The carrier material is based on a thermoplastic polyolefin.
Contrasting results Gabriel-Chemie offers laser additives under its Maxithen brand and says material optimisation through the addition of 2-3% of laser additives is usually enough to achieve the desired marking contrast. The company claims to have been involved with the technology since laser marking on plastics was first introduced. As a result, its product portfolio now consists of additives and combination masterbatches (additives plus pigment) suitable for all thermoplastics. The company can also provide customers with access to infrared lasers for trials and tests. It works with a network of partners who supply laser equipment or offer contract laser marking services. Typical laser marking applications, according to Gabriel-Chemie, span promotion codes in bever- age caps and bottles, barcodes and QR codes, food and cosmetics packaging with logos and decorative designs, product information and expiry dates, animal ear tags, safety seals, security tags and anti-counterfeit measures, keyboards, automo- tive interior and exterior components, cables and
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