Internal Antistatic Agents

Intermetallics Intermolecular forces Internal antistatic agents Internal conversion Internal energy Internal placticizers... 

The incorporation of metal salts of amphoteric surface active agents (Mostat Series) as internal antistatic agents in polypropylene fibers has been reported (95). Metal salts of alanine, amidoamine, and imida2oiine-type amphoteric surface-active agents show excellent performance as internal antistatic agents and also improve the dyeing abiUty of the fibers with acid dyes. 

Table 8. Commercially Available Internal Antistatic Agents and the Polymers for Which They Are Recommended ...

Internal antistats are considered permanent antistats. This permanence is based on the concept that most plastic products are disposable, so that the antistat is not required to last long. The antistatic effectiveness of an internal antistat can decrease over time. One study showed large increases in surface resistivity on antistatic bags stored at 71 °C for six months. Antistatic bags stored at room temperature showed only a small increase in surface resistivity (137). Loss of antistatic effectiveness is attributed to the volatility of the antistatic agent. The antistat does not easily wear off the plastic, but it can be removed with solvents and/or repeated wear. 

The effectiveness of an internal antistatic agent incorporated in the melt depends primarily on its molecular structure. This determines properties vital to the antistatic effect such as polarity and migration. The aliphatic C)4-C,7 chain in the alkanesulfonates imparts the required migration property to polar plastics, whereas the polar group is responsible for their hygroscopic behav-... 

Alkanesulfonates are preferably used as an internal antistatic agent for plastics, but where incorporation into the polymer is not possible they can be applied to the surface of the finished article in the form of a 1 % aqueous solution of the surfactant by spraying or dipping [99]. 

Alkanesulfonates are widely used as an internal antistatic agent for poly(vinyl chloride) (PVC). Since alkanesulfonates cause hazing of unplasticized PVC in the normally used quantities of 1.0 to 1.5 parts per hundred parts resin (phr), its main use is in the manufacture of opaque PVC-calendered film. To produce transparent unplasticized articles, the addition of alkanesulfonates should not exceed 0.3 phr. Figure 40 shows the antistatic effect of alkanesulfonates in PVC. 

For antistatic modification of extruded and injected-molded articles made from unplasticized PVC, internal antistatic agents are unsuitable in the usual amounts (<2 phr). Instead, the external application of the alkanesulfonates solution mentioned above is recommended. 

Alkanesulfonates are an important internal antistatic agent for polystyrene (PS) as well. If it is not possible to apply the pure active surfactant with the intended processing machine, the use of a master batch of alkanesulfonates and an appropriate polystyrene product is recommended. The addition of alkanesulfonates in amounts greater than 0.3 phr can cause hazing also in transparent PS articles. The antistatic effect of alkanesulfonates in PS is demonstrated in Fig. 41. 

Saturated hydrocarbons (waxes), fatty acids, metal soaps, fatty acid amides and esters (primarily Cig-Cis) act as internal lubricants, fluoro elastomers as external lubricants. Many other polymer additives, e.g. antistatic agents, antifogs, antioxidants, UV stabilisers, etc., act as lubricants in the barrel of the extruder once they are in the liquid form. 

Poly(oxyethylene) sorbitan monolaureate is a surface active compound which is also known as an internal or external antistatic agent for a great number of plastics. It has been found that this compound provides an almost instantaneous antistatic action (14). 

Antistatic agents. Static electrical charges may build up on the surface of polymers due to their low electrical conductivity, which may cause dust accumulation and sparking problems. These charges can be dissipated through the addition of external or internal antistatic agents (phosphate and fatty acid esters, sulfated waxes, quaternary ammonium compounds, amines, etc.). 

Antistats can be appiied internally or externally. Internal antistats are compounded into the resin, and act once they migrate to the surface of the poiymer. External antistats are appiied directly on the surface by spraying, or sometimes by dipping the polymer in a solution of the antistatic. Internal antistatic agents can... 

Antistatic agents commonly used are substances that are added to plastics molding formulations or to the surface of molded articles in order to minimize the accumulation of static electricity. In general terms, antistatic agents can be divided according to the method of application into external and internal agents. 

Nonionic antistatic agents are supplied for the most parting liquid form or as waxes with a low softening region. The low polarity of this class makes its members ideal internal antistatic agents for polyethylene and polypropylene. 

---