Hot melt adhesives, being highly temperature-sensitive materials, undergo a severe test of their internal structure when exposed to the extreme heat of the Middle East. Understanding these "high-temperature stress responses" is the first step to ensuring their performance stability.

1. Loss of Physical Form: From Solid to "Soft Mud"
The foundation of hot melt adhesives is their thermoplasticity. When the ambient temperature consistently exceeds their softening point (especially inside sealed shipping containers where temperatures can surpass 70°C), types like EVA and PSA begin to soften, losing their solid form. This causes adhesive sticks to bend and granules to fuse into hard lumps. This not only paralyzes automatic feeding systems but also makes subsequent processing difficult.

2. "Premature Aging" of Chemical Properties: The Onslaught of Thermo-Oxidation
Sustained high temperatures act like an accelerated aging test, triggering and accelerating oxidation reactions within the adhesive's molecules. The most visible manifestation is the yellowing or darkening of the adhesive. More critically, this oxidation damages key properties like initial tack, holding power, and cohesion.

3. The "Fatal Flaw" of PUR: Pre-Reaction in Heat and Humidity
For chemically crosslinking PUR (Polyurethane Reactive), heat brings not only thermal energy but also an intensified moisture threat. High temperatures drastically increase the activity of trace moisture within the packaging. This moisture pre-reacts with the PUR's active isocyanate (-NCO) groups. The consequence is that when customers use the product under normal conditions, the PUR's pot life is significantly shortened, and its final bond strength and toughness are compromised—its performance is degraded even before use.

4. The "Invisible Collapse" of PSA: Loss of Cohesive Strength
The performance of Pressure-Sensitive Adhesives (PSA) relies on a balance between tack, elasticity, and cohesive strength. High temperatures significantly reduce this cohesive strength, causing the adhesive to experience "cold flow" under sustained pressure (e.g., stacked rolls)—slowly deforming and shifting like toffee, ultimately leading to adhesive failure or residue.