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Pureland

木虫之王 (知名作家)

[资源] 胶黏剂基础之5——新型柔韧性环氧树脂胶黏剂（英文版）

Introduction
Since first discovered in 1943, epoxy adhesives have gained a solid reputation in industries that require optimum performance and reliability. Epoxy adhesives are widely used in the aerospace, automotive, electrical / electronic, construction, and medical industries. The primary reason for the broad acceptance of epoxy adhesives in so many markets is their capacity to provide a good balance of handling characteristics and ultimate physical properties.
The advantages and disadvantages of epoxy adhesives are compared generally to other structural adhesives in Table 1. Epoxy adhesives are relatively inexpensive materials that are available as solventless resins, solvent solutions, water based dispersions, and solids (e.g., film and powder). They adhere well to a wide range of substrates, offer resistance to many environments, and can be formulated to provide pot lives and cure rates that can be adjusted to meet practical production requirements.

Note: Advantages and disadvantages will depend on the specific epoxy adhesive formulation.
However, unmodified epoxy resins cause certain problems for both the adhesive formulator and end-user. Unmodified epoxies are often rigid and brittle; hence, impact resistance and peel strength are poor. Since they are thermosetting systems that cure by chemical reaction, metering and mixing of the unreacted components and time and temperature are required to polymerize the epoxy system. Although epoxy adhesives are environmentally friendly and often formulated without solvents, clean-up or dilution may require the addition of an organic solvent that contributes to environmental, health, and safety concerns.
Formulators have been vigorously working to minimize the major shortcomings of these adhesives. Fortunately there are a wide variety of starting epoxy raw materials, modifiers, and additives that can be used in this pursuit. As a result significant achievements have been made in epoxy adhesive technology with regard to:
• Improvements in flexibility and toughness,
• Advancement of waterborne systems and solid (powder, film, etc.) systems,
• Development of formulations for fast, simple application ("performance-on-demand"

, and
• Incorporation of performance-enhancing additives.
This article will concentrate on developments in the first area, improving flexibility and toughness. Recent developments will be summarized as well as the market opportunities that such activity provides. Perhaps, the greatest commercial advancements in epoxy structural adhesives over the last decade have been made in improving flexibility and toughness. The remaining areas of epoxy advancement that are listed above will be discussed in future SpecialChem articles.[ Last edited by Pureland on 2012-12-17 at 21:16 ]

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