Metal stearates, effect

Neutralise acidity (e.g. deriving from acidic catalyst residues) effectively. Commonly salts of weak organic acids (metal stearates) or inorganic bases (hydrotalcite). Also called antiacids. 

Hoang, E.M., Liauw, C.M., AUen, N.S., Fontan, E., and Lafuente, P, Effect of Metal Stearate Antacid on the Melt StahiUzation Performance of Phenolic/Phosphite Antioxidants in Metallocene LLDPE. Part 1 Melt Processing Stahility /. Vinyl Addit. Technol., 10, 3, 137 (2004)... 

Because the forces of attraction prevail when molecules are brought into sufficiently dose proximity under normal conditions, release is best effected if both the strength of the interaction and the degree of contact are minimized. Aliphatic hydrocarbons and fluorocarbons achieve the former effect, finely divided solids the latter. Materials such as microcrystalline wax [64742 42-3] and hydrophobic silica [7631-86-9] combine both effects. Some authors refer to this combined effect as the ball bearing mechanism. A perfluoroalkylated fullerene nanosphere would perhaps be the ultimate example of this combined effect (17). These very general mechanistic remarks can be supplemented by publications on the mechanism of specific classes of release agents such as metallic stearates (18), fatty acids and fluorinated compounds (19), and silicone-coated rdease papers (20,21). The mechanism of release of certain problem adherents, eg, polyurethanes, has also been addressed (22,23). 

Sears and Schulman (51) measured surface pressures and potentials vs. molecular area (20 to 110 sq. A. per molecule) for the alkali metal stearates over 0.5N solutions of LiOH, NaOH, and KOH. Like Adam and Miller, they detected a specific cation effect on the 7r-A and AV-A isotherms of the ionized monolayer at high pH the ir-A curves were expanded in the order of the crystalline sizes of the alkali metal cations K > Na > Li. The sequence is the reverse observed for the long-chain... 

In PVC, alkaline-earth-metal stearates prevent dehydrochlorination quite effectively by reducing the energy of activation of photo-oxidation. ... 

Duvdevani(40) have been directed at modification of ionomer properties by employing polar additives to specifically interact or plasticize the ionic interactions. This plasticization process is necessary to achieve the processability of thermoplastic elastomers based on S-EPDM. Crystalline polar plasticizers such as zinc stearate can markedly affect ionic associations in S-EPDM. For example, low levels of metal stearate can enhance the melt flow of S-EPDM at elevated temperatures and yet improve the tensile properties of this ionomer at ambient temperatures. Above its crystalline melting point, ca. 120°C, zinc stearate is effective at solvating the ionic groups, thus lowering the melt viscosity of the ionomer. At ambient temperatures the crystalline additive acts as a reinforcing filler. 

Table I. Effects of Metal Counterion and Metal Stearates...

The plasticizing effects of a larger number of metal stearates on the zinc sulfonate ionomer were examined, and the results are given in Table III in terms of flow and mechanical properties. Lead stearate, zinc stearate, and ammonium stearate significantly improved melt flow along with the stearic acid control. The barium, magnesium, sodium, lithium, and calcium stearates showed little, if any, improvement in melt flow. Of the four melt flow improvers, both stearic acid and ammonium stearate exerted deleterious effects on tensile properties. Only the zinc and lead stearates substantially improved tensile properties. Thus, while zinc stearate is not unique, the number of fatty acid derivatives that improve both melt flow and mechanical properties is limited. 

Russell [545] and Chauduri [142] studied the effect of stearates on the resistance of polypropylene to oxidation by air. Stearic acid reacts with heavy metals or metal oxides (catalyst residues remaining in the polymer or transferred from the surface of the processing equipment) to yield heavy metal stearates... 

EFFECT OF METALLIC STEARATES ON THERMAL OXIDATION OF ABS PLASTICS [333]... 

As soon as the maleated coupling agents were introduced into the WPC, it was noticed that their effect often significantly depends on lubricants employed in the same system. The most striking was a conflicting effect between maleated polyolefins and metal stearate lubricants (Tables 5.15 and 5.16)... 

The effect of conflicting of the maleated polyolefins with zinc stearate and other metal-containing stearates is commonly known in the industry. Therefore, a number of companies have developed nonmetal lubricants, such as Ferro Corporation RC-553, RC-571, RC-572, RC-576, SXT 3100 (see Table 5.16 Ferro s SXT 2000 is a blend of metal stearates with other nonmetal lubricants [3]), Struktol TPW-113 (Struktol s TPW 104 contains zinc stearate), Lonza Glucolube WP-2200 (a new proprietary amide lubricant that contains no metal stearates [12]). 

Metals in metal stearates quite significantly effect the lifetime of plastics and composite materials. Table 15.18 illustrates these effects. 

Effects of a series of transition metal stearates, the concentration of the copper stearate, the solvent, various additives, and other factors on the thermal oxidation of polypropylene were studied in trichlorobenzene solution. The mechanism of copper catalysis is discussed. The order of decreasing catalytic activity of the metal stearates was Cu > Mn > Fe > Cr > Al Ni Co control Ti >> Zn >> V. The addition of propionic acid to the solvent accelerated the oxidation of the polymer. The presence of the copper leveled off oxygen uptake of the polymer after a certain time. The amount of oxygen absorbed decreased with increasing concentration of the copper, and at higher concentration (7.9 X 10 3M) the polymer oxidation was inhibited. 

In this chapter, the effect of a series of transition metal stearates on the thermal oxidation of polypropylene in homogeneous solution is examined, and the results obtained are compared with that in bulk reported previously (16). In addition, the effects of the anion of copper compounds, the concentration of copper, the solvent, and the additives on the copper compound-catalyzed thermal oxidation of polypropylene are studied, and the mechanism of the copper catalysis in solution is discussed. 

Effect of Metal Stearates. The oxygen uptake curves of isotactic and atactic polypropylene in the presence of transition metal stearates in trichlorobenzene are shown in Figures 1 and 2, respectively. The order of decreasing catalytic effect of the metal stearates at the early stage of the oxidation of the polymers is for isotactic PP, Cu > Mn > Fe > Cr > Co > Ni > Ti > control > A1 > > Zn > > V and for atactic PP, Cu > Mn> Fe > Cr > Ah Ni Co control Ti >> Zn >> V. The order of the catalytic effect of the metals is quite different from that in bulk reported previously (16). In particular, V-stearate inhibits the thermal oxidation, and Co-stearate is not as effective as in bulk. In the presence of effective metal stearates such as Cu and Fe, the oxygen uptake levels off after a certain time. However, the amount of oxygen absorbed in the isotactic polypropylene is higher than that in the atactic polypropylene. 

Effect of Anions in Copper Compounds. Since the copper stearate was the most effective catalyst among the transition metal stearates for the early stage of the thermal oxidation of polypropylene, the effect of anions in copper compounds on the thermal oxidation of atactic polypropylene was examined. The oxygen uptake curves of the polymer in the presence of various copper compounds (acetate, propionate, butylate, stearate, laurate, polyacrylate, and cupric oxide) are shown in Figure 4. In the absence of the copper compounds, oxygen uptake of the polymer increases linearly with time. In the presence of copper compounds of fatty acids (acetate, propionate, butyrate, laurate, and stearate), the oxygen uptake of the polymer levels off at ca. 25-30 O2 mL/g polymer after... 

Mechano—chemical processes that are essential for HDPE macromolecular dispersion were defined by analyzing MWD of the transfer fragments of polyolefine—based composites doped with active additives (5 wt.%), such as antioxidant (Neozone D), aromatic compound (anthracene) and metal seilt (zinc stearate). Effect of the active additives on molecular features and certain friction characteristics of HDPE (load 0.5 MPa sliding velocity = 0.25 m/s) is shown in Table II. 

For waterborne paint systems (especially emulsions used for decorative purposes) defoamers based on mineral oils are often used. In addition to the mineral oil as carrier, these products contain finely dispersed hydrophobic particles (e.g., silica, metal stearates, polyureas) as defoaming components. A small amount of silicone is sometimes included to intensify the defoaming action. For high-quality waterborne coatings in industrial applications, defoamers are used that contain hydrophobic silicone oils as the principal defoaming component instead of mineral oils. They have a better defoaming effect, but are more expensive. In most cases silicone defoamers do not cause the gloss reduction that is often observed with mineral oil products. 

NDBs can contain highly concentrated combinations of AOs, add scavengers (metal stearates), light stabilizers (HALS and UV absorbers), and other additives. For delivering phosphite AOs, NDBs are said to provide better combinations of processing stability and hydrolytic stability than phosphites in powder forms. Also, NDBs reportedly allow the least-expensive phosphites to perform more effectively, saving the costs of using more expensive AOs in powder form, for equiwilent performance [3-30]. 

Lubricants are used with polymers for two main needs external lubrication and internal lubrication. External lubrication reduces friction between the polymer and the extrusion hardware, such as on the internal flow surfaces of the die. For example, lubricants can help eliminate melt fracture of blown film by reducing stress on the polymer as it passes through the die. Additionally, die drool (or die lip buildup) has been reduced by the use of lubricants. Internal lubrication reduces the friction between flowing polymer molecules, effectively reducing melt viscosity. Use of internal lubricants can reduce the power consumption required for polymers that are difficult to process. Some common lubricants are metal stearates and paraffin waxes. 

Coating is increasingly used to enhance the properties of fillers. One of the most widely used materials is stearic acid. Metal stearates are particularly effective as coatings for reactive particulate fillers, such as magnesium hydroxide (MH), producing polypropylene compounds with better impact resistance than those containing uncoated, or stearic acid-coated fillers. 

Metal stearates, including predominately calcium stearate as well as zinc stearate, are the most widely used lubricants. In PVC calendering and extrusion, the stearates provide heat stabilizing effects as well as act as an internal Inbri-cant. In polyolefins, stearates act as external lubricants as well as deactivators of catalyst residues. Ferro (Synpro, Petrac), Baerlocher (Hydense), and Crompton (Witco) are the major producers of metal stearates in North America. 

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