Principles of Dipping

Several synthetic polymers are used by the glove industry. Clearly, for dipping, the polymer must be provided in a liquid form. For poly(vinyl chloride) the liquid is a plasHsol, which is a dispersion of the polymer in an organic liquid, most of which is a plasticizer for the polymer. Heat treatment causes the plastisol to gel and the plasticizer to dissolve in the polymer, giving the final flexible composition. Gloves made from this composition are commonly termed vinyl . 

There are only two commercially important water-borne polymers currently used by the dipping industry and both are used to manufacture hand-protection articles. These polymers are  

Nitrile and polychloroprene latices are made by the industrial process of emulsion polymerization, in which the polymerization reaction and the formation of an aqueous emulsion occur simultaneously. In this process, reaction temperature and control of the polymer molecular weight are important in order to obtain the desired final glove properties. In the case of the nitrile latex, the ratio of the three monomers can also be used by the polymer chemist as an important tool in tailoring the final product properties. 

The basic concept of producing a coating or a thin-walled article by the dipping process is straightforward. A former of the desired shape is dipped into a liquid mix 

There are several ways in which the deposition of the mix can be controlled, in order to produce the desired wall thickness in the final article. The first is simply by adjusting the viscosity and solids content of the liquid, and is applicable to both solution and dispersion mixes. This process is called simple or straight dipping and is the method usually employed for making condoms from natural rubber latex. Straight dipping usually yields thin films. For the manufacture of condoms, the final film is normally built up by two or more separate dips. 

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Figure 12 Principle of dip-pen nanolithography , whereby SAM-forming molecules are transported to a specific position with nanometer resolution, by means of an AFM tip. The molecules are transported within the water meniscus at the tip-substrate interface. From Reference 54 with kind permission.

Figure 10 Schematic diagram illustrating the basic principles of dip-pen nanoUthography.

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