Лако-красочные материалы — производство

7.1 Introduction You only have to type the words ‘adhesives for plastics’ into an internet search engine and you are rewarded with thousands of websites, each one of which is trying to tempt you to visit their site for one reason or another. There is a bewildering range of adhesives available to the end user […]

PTFE and other fluoropolymers have been treated using a solution of sodium in liquid ammonia and other etching solutions [3]. This method dramatically improves surface-wetting characteristics, and the plastic can then readily be bonded using a wide range of adhesives. In the late 1980s primers were introduced that considerably enhance the adhesion of cyanoacrylates to […]

Flame treatment is often used to change the surface characteristics of plastics. It involves passing the surface of the plastic through the oxidising portion of a natural gas flame. The surface is rapidly melted and quenched by the process; some oxidation of the surface may occur at the same time. Exposure to the flame is […]

Plasma surface treatment increases the surface energy of a substrate by bombarding the substrate surface with ions of a gas such as argon. Plasma treatment can be performed at atmospheric conditions or in a sealed chamber under extremely low pressures. By selecting appropriate gases and exposure conditions, the surface can be cleaned, etched or chemically […]

The corona discharge technique consists of having the polymer film pass over a metal electrode coated with a dielectric material which receives a high voltage from a high-frequency generator (10-20 kHz). Normally the voltage increases cyclically until the gas ionises, generating a plasma at atmospheric pressure that is known as ‘corona discharge’. This is a […]

Several techniques are in use within the plastics industry, including corona discharge, plasma etching, flame treating and the use of chemical primers to enhance surface energy. 6.3.1 Abrasion One of the easiest forms of surface preparation is simply cleaning and abrading the surface. The most common procedure is a solvent wipe, followed by abrasion and […]

When a designer is selecting an adhesive for a specific application, the engineering properties of the individual plastic will be considered carefully. All too often, however, the data supplied by the plastic manufacturer will include melting point, mould shrinkage, tensile modulus, hardness, dielectric properties, water absorption, density and thermal conductivity but almost never the surface […]

6.1 Surface Wetting Silicone rubber, polytetrafluoroethylene (PTFE), Acetal and the polyolefin plastics (polypropylene, polyethylene) are always a challenge to the adhesive engineer due to the low surface energy of these materials. Whilst the detailed consideration of surface tension is more in the province of the physicist than the engineer, wetting (the establishment of contact) plays […]

Good wetting of the substrate surface is essential for developing reliable bonds. Adhesives that do not wet the surface will not spread out and fill substrate surface irregularities. Wetting occurs when the surface tension of the liquid adhesive is lower than the critical surface tension of the substrates being bonded (see Section 6.1). In many […]

Viscosity is a product property associated with all engineering adhesives and with most sealants. The rheology of an adhesive is the key to determining its potential field of application (gap-filling capability, strength before curing, penetrability, orientation of parts receiving adhesive, etc.) and the dispensing systems to be used. Viscosity is defined as a measure of […]