Is the high amount of fine powder in hot melt adhesive a sign of poor quality? 5 common misconceptions about the appearance of rubber particles

First answer: Having more fine powder does not necessarily mean poor quality, but it is worth asking a question

Hot melt adhesive granulesA small amount of fine powder at the bottom of the bag is a normal phenomenon. Particles rub against each other during granulation, cutting, conveying, bagging, and long-distance transportation, inevitably producing powder. The industry generally considers a fine powder proportion of less than 1% to be within the normal range. What really needs to be wary of is the abnormal amount of fine powder, dark color, or accompanied by a large amount of clumping – this often points to rough cutting process, insufficient cooling, or damp storage, rather than “poor glue itself”.

Misconception 1: Fine powder will cause a decrease in adhesive strength

Fine powder and particles are the same material, with identical chemical composition and no difference in properties after melting. Its real impact lies in the feeding process: the powder has a low density, is prone to bridging, and is easily blocked in the automatic feeding system. After entering the melt glue pot, it has a large heating area and heats up quickly. If it stays on the pot wall for a long time, it will first carbonize and form black slag. So the problem lies in ‘difficult operation’, not ‘inability to stick firmly’.

Misconception 2: Larger particles are better

Many buyers feel that the large particles make the material appear solid. In fact, the particle size needs to match the adhesive method: small adhesive pots and graphic printing equipment use small and medium-sized particles to heat up quickly and melt evenly; Using slightly larger particle sizes for large sealing and pasting lines is less likely to cause clumping and bridging. Blindly pursuing large particles, small devices are prone to surface coating and internal mixing of raw materials.

Misconception 3: The whiter the color, the purer it is

The color of the adhesive particles is determined by the base material and thickening resin, and also depends on whether whitening agents are added. Beige, milky white, and semi transparent are common appearances. Conversely, using whitening agents to make the color exceptionally white does not necessarily mean the formula is better. Judging quality should be based on measured data such as softening point, melt viscosity, and peel strength, rather than relying solely on the naked eye.

Misconception 4: If it clumps, it must be scrapped

Slight clumps are mostly caused by moisture or high storage temperatures in summer, resulting in physical adhesion. Those that can be pinched and dispersed by hand can usually be used, but they should be spread out in a cool and shady place to dry first to avoid bubbles and white spots caused by moisture entering the pot. If it forms a hard lump and the cross section becomes sticky and brushed, it indicates that it has softened and deformed, and should not be used for formal production anymore.

Misconception 5: Black spots indicate the addition of recycled materials

There are several sources of black spots: carbonization residue generated by long-term failure to clean the melt glue pot, residue of different grades from the previous batch, aging and falling off of the conveying pipeline, and finally the problem with the raw materials themselves. If black spots are found, first clean the pot, replace the filter screen, and then take new materials for control experiments. Don’t rush to draw conclusions. To distinguish between mixed materials, it is important to observe viscosity fluctuations and odors between batches, rather than a few black spots.

FAQ

Q: Can fine powder be collected separately for use?
Answer: It can be mixed in small amounts and reused. It is recommended to control it within 10% of the total feed and melt it in a timely manner. Do not accumulate it at the bottom of the pot for a long time.

Q: How to reduce the fine powder generated during transportation?
Answer: Choose packaging with a sturdy inner lining, avoid multiple bag transfers, and do not stack excessively high when stacking.

Instead of worrying about appearance, it’s better to establish the acceptance criteria for storage: measure the softening point and melt viscosity of each batch, and keep samples for comparison. Guangzhou Sunlife TradingSunlife Hot Melt AdhesiveEach brand comes with testing data at the factory, supporting customers to review by batch number. The stability between batches is traceable and much more reliable than relying on visual judgment.