Antistatic effect

Abbreviations of prominent use properties of the various classes of commercial surfactants are shown in Table 1. Antimicrobial activity includes germicidal, bactericidal, and bacteriostatic effects emolliency describes lubrication or a soft feel imparted to skin by surfactants a hair conditioner is a substantive surfactant appHed from aqueous solution to impart a lubricating or antistatic effect and opacifters are used to thicken hand-dishwashing products and cosmetic preparations to convey an appearance of high concentration and to retard solvent drainage from foam. 

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 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. 

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. 

Alkanesulfonates, mostly in combination with other surfactants, can also be used to provide an antistatic effect on expandable polystyrene. Even after foaming up of the polystyrene pearls, such as with water, the antistatic effect is retained [90],... 

FIG. 40 Antistatic effect of alkanesulfonates in rigid polyvinyl chloride (tin-stabilized). Surface resistance according to DIN 53 482. Test specimen I-mm milled sheets, stored for 1 day at 23°C and 50% relative humidity. 

In contrast to the applications previously described in which alkanesulfonates are used in polymers with a high glass transition temperature (PVC, polystyrene, and ABS), in antistatic-modified polyethylene articles the antistatic agent is able to continue migrating to the surface over a long period of time. Thus, a more permanent antistatic effect is achieved. 

AGENTS FOR FIBRE LUBRICATION, SOFTENING, ANTISTATIC EFFECTS, SOIL RELEASE 705... 

Even if this class covers the smallest market segment, amphoteric surfactants still remain useful because of their unique properties, which justifies their comparably high manufacturing costs. Since they have partial anionic and cationic character, they can be compatible, under specific conditions, with both anionic and cationic surfactants. They can function in acid or basic pH systems and, at their isoelectric point, they exhibit special behaviour. Many amphoteric surfactants demonstrate exceptional foaming and detergency properties combined with antistatic effects. 

The surfactant and anti-corrosion properties of PEs also find use in textile auxiliaries -low foaming gives further benefits and C8 diesters are also reported to give antistatic effects on synthetic fibres. 

Concentration of antistats in plastics is mostly 0.1 to 2 %. Special grades of electroconducting (EC) carbon black are used in PO at levels higher than 10 % (Accorsi and Yu, 1998). Other conducting fillers incorporating antistatic effects, such as metals or organic semiconductors (e.g. polypyrrole) are not commonly used in plastics for contact with food. 

Some effects are similar or assist each other, for example silicone elastomers cause water repellency, softeners bring about antistatic effects and antistatic finishes can be softening. 

Anionic softeners are heat stable at normal textile processing temperatures and compatible with other components of dye and bleach baths. They can easily be washed off and provide strong antistatic effects and good rewetting properties because their anionic groups are oriented outward and are surrounded by a thick hydration layer. Sulfonates are, in contrast to sulfates, resistent to hydrolysis (Fig. 3.3). They are often used for special applications, such as medical textiles, or in combination with anionic fluorescent brightening agents. 

Typical properties are good softening effects, low permanence to washing and high antistatic effects (becanse of their strong ionic character). They have fewer ecological problems than similar cationic prodncts. Examples of the betaine and the amine oxide type are shown in Fig. 3.4. 

Most non-polymeric antistatic finishes are also surfactants that can orient themselves in specific ways at fibre surfaces. The hydrophobic structure parts of the molecule act as lubricants to reduce charge buildup. This is particularly true with cationic antistatic surfactants that align with the hydrophobic group away from the fibre surface, similar to cationic softeners (see Chapter 3, Fig. 3.1). The main antistatic effect from anionic and non-ionic surfactants is increased conductivity from mobile ions and the hydration layer that surrounds the hydrophilic portion of the molecule since the surface orientation for these materials places the hydrated layer at the air interface. 

Another advantage of the silicon oxide network is that it can be modified in various ways as shown in Fig. 18.2. One way is co-condensation of the most nsed tetramethylol silanes with other kinds of metal oxides. Another way is cohydrolysis and co-polycondensation with snbstitnted trimethoxy silanes where this substituent is, for example, a long alkyl chain for hydrophobation, an organic portion with polar structures for antistatic effects, a fluorocarbon for the release of water, oil and soil or a bioactive group. The easiest method of modification is the physical one, the simple addition of the desired chemicals. They are then incorporated in the porous network of the metal oxides and are released in a more or less controlled way. 

The cationic product SIbIGEN HS Imparts good softness to fibres of all types. It also has an antistatic effect. 

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