Interaction with Other Additives

Ideally, pigment should provide only color. They are expected to be heat- and light-stable and not have any effect on fiber properties. However interactions do occur. Some are predictable—such as the interaction between some inorganic sulfides with nickel stabilizers. Most interactions are unpredictable and are found only via an Edisonian approach, that is, produce the fiber and test it. 

Steinlin and Saar reported the effect of various concentrations of pigments on the light stability of fine-denier polypropylene yarn (72 denier, 24 filament) containing varied levels of Tinuvin 770 [145]. Although Tinuvin 770 is not a preferred HALS stabilizer for fine-denier fibers, the data presented are of considerable interest. (The authors pointed out that Tinuvin 622 and Chimassorb 944 are preferred for polypropylene fibers.) The amount of energy required to reduce yarn strength by 50% was determined. Tinuvin 770 was added at 0.25, 

---

Practically all lubricating oils contain at least one additive some oils contain several. The amount of additive that is used varies from < 0.01 to 30% or more. Additives can have detrimental side effects, especially if the dosage is excessive or if interactions with other additives occur. Some additives are multifimctional, eg, certain VI improvers also function as pour-point depressants or dispersants. The additives most commonly used in hydrautic fluids include pour-point depressants, viscosity index improvers, defoamers, oxidation inhibitors, mst and corrosion inhibitors, and antiwear compounds. 

The particular absorber to be used in a given application depends on several factors. One important criterion is whether the absorber will strongly absorb that portion of the ultraviolet spectrum responsible for degradation of the plastic under consideration. Compatibility, volatility, thermal stability, and interactions with other additives and fillers are other items that must be considered. When used in food wrappings, Food and Drug Administration approval must be obtained. While one or more of these considerations may rule out a given stabilizer or influence llie choice of one class over another, the final selection must await the results of extensive accelerated and long-term tests. 

The prediction of antiwear benefits and optimization of the ZDDP dosage has become a very complex task. The chemistry of the mode of action of ZDDP itself is complicated and so the nature of its interactions with other additives needs investigating all the more. Interaction between ZDDP and fatty acids, again in lubricating oil formulations, shows a considerable amount of mechanical test wear. The antiwear property of ZDDP is reduced by fatty acid additive due to the adsorbed layer of fatty acid, and the solubilization process, which disturbs the function of ZDDP (Otsubo, 1975), see Fig. 2.11. 

As for all additives, interactions with other additives in solution, Fig. 3.16, and competition for surface reaction sites together with the effect of environmental factors such as temperature, blow-by gases, water and fuel dilution have variable effects on the formation of the film. Because ZDDPs are much more widely used as antiwear performance additives compared to other classes of compounds, these additive effects will now be discussed in greater detail than has been the case for other classes of anti-wear/friction additives. In particular the influence of structure, concentration, dispersant, detergent, antioxidancy and friction modifier on friction and wear will be discussed. In addition the influence of NO c and H2O will be briefly illustrated. 

In using organic or inorganic pigments or colorants, considerations should be given to their influence on the final performance properties, especially electrical properties and any interactions with other additives of the formulation. 

To enhance polymer properties, additives must interart with the polymer matrix and the mechanisms that tend to stress or degrade it. Unfortunately, they may also interact with other additives or the external environment in unexpected ways. One additive might improve property X while hurting property Y (or while diminishing a different additive s effect on improving property Y). 

This chapter provides a basic description of UV s effects on POs, and how different additives interfere with UV degradation. The different roles and mechanisms of various commercially available additives are related to each other in terms of effectiveness, relative costs, and interactions with other additives. (Since UV stabilization is an ever-developing field of continuously "new and improved" additives, emphasis will be given to more recently commercialized additive types.) UV stabilizer use in different PO applications will be presented, and case studies will show how companies have been able to fight the effects of UV in real applications. 

Interactions with other additives Some nudeators or darifiers may interact with other additives in the compound. Sodium benzoate, for example, is reactive with caldum stearate which is used as a lubricant and add scavenger—though not with hydrotaldte-based add scavengers. Or haze may be inaeased by the peroxides used in controlled-rheology PP for viscosity-breaking and improved melt flow. Different darifiers reportedly can limit this haze inaease such as RiKA s nonsorbitol PCI product [10-4, 10-19]. 

Process aids can sometimes interact with other additives and lose some of their effectiveness. Antiblocking agents such as silica and talc and certain pigments are known to have an adverse effect. Careful selection of processing aids is advisable with certain polyethylenes containing HALS additives. Different substances are used in different polymers and to combat different defects. 

Hindered amine light stabilisers function as free radical scavengers and can double as thermal antioxidants. They are, though costly, effective at very low concentrations. Hindered amines can interact with other additives (e.g., phenolic antioxidants, titanium dioxide) in the PP to produce yellowishness. Halogenated flame retardants can react with hindered amine light stabilisers and render them ineffective. 

High resistance to gas fading caused by interaction with other additives as well as urbeui pollution. 

Dyes may adversely interact with other additives - primarily through charge interaction - and interfere with them. 

An accelerator is a chemical additive that is used to speed up the normal rate of the reaction between cement and water (7). This shortens the time of thickening of the cement. Further, an accelerator increases the early strength of cement. Accelerators do not increase the ultimate compressive strength of cement but promote a rapid strength development. However, in a higher concentration the accelerator may act as a retarder. Accelerators may also interact with other additives, such as dispersants. 

HALS can interact with other additives such as... 

Other concerns may be interactions with other additives. For example, antiblocking agents may absorb other additives such as antioxidants, slip agents, and other processing aids. Natural silica shows a low level of interaction whereas synthetic silica types and uncoated talc exhibit a higher absorption of additives. These properties may be affected by surface treatment (2). 

EFFECT ON POLYMER AND/OR OTHER ADDITIVES There are several aspects which must be taken into consideration in order to select appropriate additives for polyethylene processing. These include melt fracture, head pressure, blocking, and optical properties.Most antiblocks used in polyeftylene are inorganic particulates which may interact with other additives (especially processing additives based on fluorocompounds). This interaction or absorption (see more on this subject in Chapters 5, 7, 8, 10) may reduce the active concentration of the additive or delay its release from bulk (additive must migrate... 

The models discussed in this paper clearly attempt to model the lubrication of the valve train as accurately as possible. However it is evident from the methods used that they only manage to take a very limited account of lubricant properties. Certainly no account of the blend characteristics such as the additives used, their type, their interaction with other additives / the surface material and their relevance at different points within the cam / follower cycle are considered. It therefore remains an area in which possible improvements could be made, through the use of empirical data derived from tribometer tests. 

---