Anyone who works with polyurethane foam knows that results depend half on the formulation and half on the operator—and the two places operators most often go wrong are the A/B mixing ratio and chemical storage. This article covers both, so new line workers can avoid the common pitfalls.

Know your A and B components. Foam-in-place packaging uses a two-component polyurethane system: the A component (isocyanate, typically in red drums) and the B component (polyol blend, typically in blue or white drums). The two are mixed at the weight ratio specified by the manufacturer; the reaction expands and cures into foam. Cosmolar foam glue is labeled with its standard ratio at the factory, so production lines only need to meter accurately—no formula tuning required.

What happens with an incorrect ratio? Too much A component makes the foam brittle and crumbly, destroying cushioning; too much B component causes poor expansion, collapsed foam and weak recovery. Calibrate your meters and keep the ratio within ±2%. On semi-automatic and fully automatic machines, the equipment meters the ratio automatically—check the pumps and hoses regularly to prevent A-component crystallization from clogging the system and skewing the ratio.

Storage is the key to preventing crystallization. The A component is extremely sensitive to moisture: when it absorbs humidity it reacts and crystallizes, clogging drum openings, pumps and hoses. A key reminder for the warehouse: after opening the red A-component drum, wrap the connection between the drum opening and the transfer pump with waterproof tape or stretch film to reduce air exposure and prevent moisture-induced crystallization. Also: keep A and B components separate to avoid cross-contamination; store in a dry, shaded, ventilated area at 5-35°C; seal drums tightly when not in use and use opened drums within 3 months.

Quick troubleshooting. Foam does not expand: check the ratio first, then check whether the A component has crystallized. Foam shrinks: ambient temperature is too low—warm the B component. Brittle foam: A-component ratio is too high or it absorbed moisture. When in doubt, send us photos—Cosmolar after-sales will help you diagnose.

A/B ratio and storage discipline are the fundamentals of using polyurethane foam glue, and the prerequisite for reliable protection. For ratio charts, storage guides or test reports, contact Cosmolar, the source factory for polyurethane foam packaging: https://www.cosmolar.com/