News

Knowledge

Company News

Application Mind Map

Test Report

Technical Article

Industry News

Analysis of Common Issues with Traditional Adhesives (Part 5)

Release time:

2025-04-16 01:44

Analysis of Common Issues with Traditional Adhesives (Part 5)
Analysis of Common Issues with Traditional Adhesives (Part 5)

In industrial production and everyday bonding applications, traditional adhesives have long occupied a prominent position thanks to their advantages such as low cost and wide applicability. However, in the application of traditional adhesives, porosity in the adhesive layer—a typical defect—directly threatens the integrity and durability of bonded structures. This manifests itself as voids and a loose structure within the adhesive layer, leading to a significant reduction in bonding strength, insufficient durability, and even potential safety hazards. Based on the common manifestations and causes of adhesive-layer porosity, this article analyzes its technical essence.

I. Typical Characteristics of a Loose Adhesive Layer

Loose adhesive layers are characterized by the presence of voids visible to the naked eye or under microscopic examination, and the bonding interface exhibits “honeycomb-like” or “layered” defects. These defects directly weaken the mechanical interlocking and intermolecular forces between the adhesive and the adherend, leading to a reduction in bond strength and a deterioration in environmental resistance.

The negative effects of a loose adhesive layer exhibit multi-scale characteristics in bonded structures:

1. Macroscopic strength degradation: Internal voids within the adhesive layer become stress concentration points, significantly reducing shear and peel strengths and substantially diminishing the structural load-bearing capacity.

2. Microscopic Defect Propagation: Microcracks tend to initiate at the edges of voids and rapidly propagate under cyclic loading, leading to interfacial debonding or adhesive layer failure.

3. Degradation of environmental resistance: The loose structure accelerates the penetration of corrosive media, leading to accelerated corrosion of the substrate and aging of the adhesive layer.

4. Failure of sealing performance: In applications requiring air or liquid tightness, gaps significantly increase the risk of leakage, thereby affecting the normal operation of equipment.

II. Analysis of the Causes of Loose Adhesive Layers

The formation of a loose adhesive layer is the result of the combined effects of material properties, process parameters, and environmental factors, specifically including the following reasons:

1. Insufficient drying

If the curing time is too short or the humidity in the curing environment is too high, the solvent will not fully evaporate, leaving residual moisture or volatile substances inside the胶体, which can lead to the formation of bubbles or pores.

2. Improper adhesive application process

If the thickness of a single adhesive application exceeds the self-leveling capacity of the adhesive, the internal solvent evaporation will be hindered, making it easy for the surface to cure while the interior remains uncured, thus forming a “sandwich” structure and causing localized looseness in the adhesive layer. Moreover, excessively high viscosity can impede bubble escape, further exacerbating the looseness of the adhesive layer.

3. Surface Treatment Defects

If surface moisture, oil contamination, or oxide layers are not thoroughly removed, they will hinder the wetting and penetration of the adhesive, resulting in a weak interfacial layer. During curing, moisture on the surfaces of the adherends evaporates, generating vapor pressure that can rupture the adhesive layer and create voids, thereby weakening the interfacial bond strength.

4. The filler’s moisture content exceeds the standard.

Moisture is introduced by the undried filler, which releases moisture during the curing process, vaporizes, expands, and forms voids. This leads to local looseness and reduces the uniformity of the adhesive layer.

5. Insufficient curing pressure

If insufficient pressure is applied during curing, the adhesive cannot fully fill the microscopic pores on the surfaces of the bonded materials, and the adhesive layer cannot effectively expel internal air. This results in physical voids at the bonding interface, and the residual voids adversely affect the bonding quality.

6. Temperature Gradient Effect

Non-uniform temperature fields lead to differences in curing rates, while localized stress concentrations cause microvoids to accumulate, thereby reducing the quality of the adhesive layer.

7. Environmental humidity interference

High-humidity environments accelerate the hygroscopic absorption of colloids, causing moisture to accumulate on the surface of the adhesive layer and form a water film. This slows down the curing reaction, hinders solvent evaporation, and triggers local phase separation—even initiating hydrolysis reactions that compromise the colloid’s structural integrity. As the adhesive layer absorbs moisture and swells, it also creates voids during subsequent curing shrinkage, thereby undermining the structural compactness.

8. Synergistic effect of curing temperature and humidity

If the curing temperature is too high or the humidity is too high, both can lead to insufficient crosslinking of the胶体, resulting in a loose structure.

III. Summary

In summary, the causes of loose adhesive layers in traditional adhesives are intricate and multifaceted, involving a variety of factors such as material properties, process control, and environmental conditions. Such issues not only directly weaken the strength and durability of bonded structures but may also pose safety risks, thereby compromising the reliability of industrial production and everyday applications. Therefore, throughout the entire process—from adhesive selection and surface pretreatment to optimization of application techniques and control of curing conditions—key parameters must be rigorously monitored, and material compatibility and environmental adaptability should be comprehensively considered to effectively prevent and mitigate the defect of loose adhesive layers.

Disclaimer: The above content is sourced from the internet and is for reference only. If any infringement occurs, please contact us, and we will remove it promptly. 

Share to:

Previous page

Analysis of Common Issues with Traditional Adhesives (Part 6)

Analysis of Common Issues with Traditional Adhesives (Part 4)

Next page

Related News

Analysis of Common Issues with Traditional Adhesives (Part 4)

In the practical application of traditional adhesives, the thickness of the adhesive layer is one of the key parameters affecting bonding performance; the precision with which this thickness is controlled directly impacts the reliability and durability of structural components. As a typical defect, an adhesive layer that is too thin not only reduces bonding strength but can also lead to premature failure. In the actual use of adhesives, the issue of reduced bonding strength caused by insufficient adhesive-layer thickness is frequently encountered. This article provides a detailed analysis of the problem of excessively thin adhesive layers, aiming to offer technical guidance for the application of adhesives.

Analysis of Common Issues with Traditional Adhesives (Part 3)

As an essential means of joining materials, adhesives play an irreplaceable role in numerous fields. However, traditional adhesives often face the challenge of brittle adhesive layers during use—these layers tend to fracture easily under stress and lack sufficient toughness, severely limiting the performance and application potential of adhesives. Adhesive-layer brittleness not only affects the overall strength and durability of bonded structures but can also lead to premature failure of products during service. Therefore, a thorough investigation into the causes of adhesive-layer brittleness and the development of effective mitigation strategies are of great significance for enhancing the comprehensive performance of adhesives.

Analysis of Common Issues with Traditional Adhesives (Part 2)

In the application of traditional adhesives, rough adhesive layers are the second most common issue after sticky adhesive layers. This manifests directly as an uneven adhesive surface with particles or bubbles present, seriously affecting bonding strength and the aesthetic appeal of the product. This article explores the issue of rough adhesive layers and provides technical improvement directions for the industry.