Close-up of a worker spraying a workpiece with a spray gun

After plastic parts are sprayed, the film pulls back at the corners and screw-boss positions; if the levelling agent is not compatible enough with the system, edge pull-back and orange peel show up at these positions first, the gloss mottles with it, and the appearance consistency after assembly is dragged down.

Chemi Tech supplies levelling agents for solvent-based coatings and room-temperature-curing plastic systems, drawn from the levelling agent KMT-458 series; the dosage is set by the resin system, the spraying viscosity and the tack-free time. This grade benchmarks BYK-358 N, with a more controllable supply cycle and response; Chemi Tech runs measured comparisons of the orange-peel grade and the gloss uniformity, and matches a fitted grade for the customer.

Advantages of Chemi Tech Levelling Agents

Chemi Tech KMT-458 series is a polyacrylate solution type, stable in compatibility in medium-to-high polarity systems, so the clear coat does not cloud and the pigmented coat shows no haze; at the same time, its surface-tension reduction is marked, and the film spreads fully before tack-free; besides, its heat stability is strong, and it does not decompose or yellow in the baking section; moreover, it does not disturb intercoat adhesion and recoating, and the rework and touch-up steps stay feasible as before; compared with imported grades, KMT-458 is more controllable in supply and response and can serve as a replacement.

Industry Pain Points and Solutions

Film defects on plastic parts usually stem from the polarity mismatch between the levelling agent and the resin system, rather than from the spray-gun nozzle size; the consequence is edge pull-back and orange peel at the corners.

The first problem to appear is at the corners and screw-boss positions. The coating contracts inward at these positions, the corners expose the substrate, and accumulation appears around the screw bosses. Chemi Tech fixes the KMT-458 dosage by the resin system, and the film is able to finish spreading within the tack-free window.

Close behind is orange peel that will not flatten. The film has no time to spread within the tack-free window, ripples remain on the surface, and the gloss mottles with it. KMT-458 reduces the surface tension markedly, and the spreading window after spraying is widened.

The last point is yellowing in the baking section. When the levelling agent's heat stability is insufficient, the film yellows after baking, especially on white and light-coloured parts. Chemi Tech checks against the resin system and the spraying viscosity, rearranges the mixing order and the dosage of KMT-458, and the gloss uniformity falls into the qualified range.

Typical Operating Conditions and Verification

Customer: a home-appliance parts enterprise in Zhejiang, for the spraying and baking line of plastic parts.

At this home-appliance parts plant, the plastic parts showed edge pull-back and screw-boss accumulation after spraying; the orange peel was not obvious in small-batch test spraying, but the rework rate climbed as soon as volume went up. An imported grade had been used and failed to hold steady as well. After checking the resin system and the spraying viscosity, KMT-458 was set as the levelling agent, the dosage was re-fixed by the tack-free time and the baking temperature, and it served as an import replacement. The panel performance after the switch: edge pull-back basically no longer appeared, the orange peel fell by one grade, and the gloss uniformity met the requirement; the rework rate fell back with it, and the performance matched that of the imported grade.

Frequently Asked Questions

For a levelling agent used in plastic parts spraying, how is the dosage usually fixed?

The dosage is decided jointly by the resin system, the spraying viscosity and the baking conditions. KMT-458 has completed comparison tests of the orange-peel grade and intercoat adhesion under multiple dosage gradients, and recommends only the dosage range in which both properties stay stable. If you currently use an imported grade, Chemi Tech can run a dedicated comparison first and give a replacement dosage; a single small trial on the current formula before full production is enough to confirm.