Antiblock properties

Figure 19.19. Antiblocking properties of LLDPE film containing CaCOs. Courtesy of ECC International, St Austell, UKia Johnson S L, Ahsan I. Polymers, Laminations Coatings Conference, TAPPI Press, Atlanta, 1997.

Table 3.9 contains a condensed summary of types and properties of antiblocking agents used in PVC. For a comprehensive review of antiblocking properties, mechanisms of action, and use of the antiblocking agents, see the specialized monographic source... 

In addition, some Asian and Middle Eastern coimtries are using a water-quenched process for the conversion of PP tubular film, most of which needs good optical properties. The film tube has to be opened up by hand immediately after conversion, and this requires good antiblocking properties to prevent delays through sticking. 

Amides dispersed in melted PE at RT, at levels exceeding their solubility, migrate to the PE surface during and after the blowing of films. Exuded amides form random aggregates on the film s surface that reduce the close contact and cohesion between adjacent sheets. Slip or antiblock activity increases upon increasing the amount of amide on the PE surface until a critical level is reached thereafter, further increase of the surface amide concentration does not improve the slip or antiblock properties and may produce an undesirable oily layer on the film. 

The fatty amides used in PE production include erucamide (EA) cis-13-docosenoic acid, amide), behenamide (docosenoic acid, amide), oleamide (OA) and stearamide (SA) [43]. Unsaturated amides, such as EA and OA, provide superior slip properties, whereas saturated amides, such as behenamide and SA, provide acceptable slip and superior antiblocking properties. EA displaced OA as the preferred slip agent for the production of PO film because it melts at a higher temperature and is more stable at extrusion temperatures EA can be used as a slip and antiblock agent [45]. SA also provides useful slip properties, although it is slower acting it has superior antiblock properties to those of EA and OA. 

Highly cross-linked spheres with an average particle size from 0.5 to 12.0 /rm have been produced. Extremely narrow particle size distributions are possible. The particle size and degree of monodispersivity are controlled by kinetic factors during the hydrolysis. Applications for Tospearl powders include wear resistance, antiblocking properties, light-diffusion control, and lubrication (542). 

Tospearl has been used as a plastic film additive in polypropylene (PP). A specific example is shown in Table 5 where Tospearl 120 was incorporated into a single PP sheet. One third less Tospearl was required when compared to silica to obtain the same antiblocking properties. In addition, the static slip was half as large. 

EXAMPLES OF FORMULATIONS Polyolefin film having antiblocking properties ... 

Polyethylene waxes have several useful characteristics in their application to paints, such as low toxicity, antiblocking properties combined with slip properties, and improved mar and scratch resistance (see Figure 10.4). ° ... 

Compounding ingredients for rubber can be conveniently packaged in bags made from thermoplastic polymers or paper, while bales of unvulcanized rubber are often packaged by wrapping them with paper or with thermoplastic film, the latter being conventionally known as bale wrap. Polyethylene is usually used for these purposes because of its plasticity and antiblock properties, and because it can be obtained at a relatively low cost. ... 

Bisamides are generally used in the same applications as primary f and are even more efficient in terms of lubricity and antiblocking properties. 

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