Types of Filler

Complex tri-dimensional object = structural effect of the filler 

It is tempting to consider a classification scheme for polymer fillers but no overall system is available and the analysis of existing proposals reveal that their validity and interest strongly reflect the application considered. We will nevertheless consider a few logical possibilities, which imderline certain specific aspects of the common property considered. 

Distinguishing Between Filler and Pigment with Respect to Refractive Index 

Silicas (fumed, precipitated) Metal oxides (TiOy ZnO.) Metal salts (BaSO, ...) 

Classifying fillers with respect to fabrication process and reinforcing activity. 

Relative Reinforcement by Carbon Blacks Judged by Tire Tests in Natural and SBR Rubbers  

Relative Typical specific reinforcement surface area, (HAF = 100) mVg 

ISAF (intermediate super abrasion furnace) SAF (super abrasion furnace) 

Carbon blacks and silicas are both manufactured by means of several different routes, and the total number of variations on each process is large (Kraus, 1965a,h, 1971a Kraus et a/., 1970 Lindley, 1964 Peterson and Kwei, 1961 Rivin, 1971 Rowland et a/., 1965 Wagner and Sellers, 1959). This section will delineate the major types of carbon blacks and silicas. 

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Elongation. The extension produced by a tensile stress appHed to an elastomer, ie, elongation, is almost always reduced by fillers. Regardless of what type of filler is used, elongation decreases with increased loading above approximately 5 vol % (13). 

Sihcone polymers when cured into elastomers by themselves ate weak, gel-like materials. For this reason, fillers must be used to provide reinforcement. The type of fillers (qv) used in sihcone sealants varies widely two of the most common fillers are fumed sihca and calcium carbonate. 

Polypropylene can be fabricated by almost any process used for plastics (see Plastics processing). The extmsion of pipe and injection mol ding of fittings present no unusual problem. However, there is no way to bond the fittings to the pipe except by remelting the polymer, which is impractical on most constmction sites. The resin can be reinforced by glass fibers, mineral fillers, or other types of fillers and can be pigmented readily. 

The term filler is usually applied to solid additives incorporated into the polymer to modify its physical (usually mechanical) properties. Air and other gases which could be considered as fillers in cellular polymers are dealt with separately. A number of types of filler are generally recognised in polymer technology and these are summarised in Figure 7.1. 

It is important to stress that with each chemical type of filler a number of grades are usually available. Such grades may differ in the following ways ... 

The chemical resistance of the mouldings depends on the type of filler and resin used. Simple phenol-formaldehyde materials are readily attacked by aqueous sodium hydroxide solution but eresol- and xylenol-based resins are more resistant. Provided the filler used is also resistant, phenolic mouldings are resistant to acids except 50% sulphurie aeid, formic acid and oxidising acids. The resins are stable up to 200°C. Some reeently developed grades of moulding compounds are claimed to be capable of exposure to 300°C for short periods. 

The meehanical properties are strongly dependent on the type of filler used and typical figures are given in Table 23.2... 

There is one particular type of filler whose value can be in no doubt. This is the so-called thixotropic filler exemplified by certain fine silicas and silicates which appear to increase the viscosity of the resin on standing. These are useful in minimising drainage of resins from vertical and near-vertical surfaces during hand lay-up operations. 

Last but not least, destruction of the matrix may result from the shaping process, the extent of which depends primarily on the manufacturing process, conditions and type of filler [376, 377]. The destruction of the matrix in a composite may be... 

Chemical structure, molecular weight, amount and type of fillers/ additives, heat history, storage, handling. 

Reinforcement of polymer matrices using various types of nanofillers is being extensively studied nowadays. The reinforcement mechanisms as well as enhancement of properties are different with different types of fillers. This field is quite green and many more developments are yet to come to enrich our science and technology in the near future. 

Interestingly, exceptions are possible. Stewart et al. [81] reported that the effect of magnesium stearate concentration on the dissolution of a model low-dose drug, riboflavin, from capsules was dependent in some manner on the type of filler. Soluble fillers exhibited the anticipated prolonged times with increasing lubricant levels. However, the trends with insoluble fillers were less predictable. In some cases insoluble fillers were only slightly affected by the concentration of magnesium stearate. For others, such as microcrystalline cellulose, there appeared to be an ideal intermediate concentration of lubricant at which the dissolution rate was maximized. 

A-4 One required for each welding procedure, for each type of filler metal (i.e., AWS E-XXXX classification), and for each flux to be used. Test pieces shall be subjected to essentially the same heat treatment (including time at temperature or temperatures and cooling rate) as the erected piping will have received. 

The various types of fillers used to make the composite disk specimens are given in Table 3. ACP [5] was prepared by rapidly stirring an equal volume of an 800 mmol/L Ca(N03)2 solution into a 536 mmol/L Na2HP04 solution previously brought to pH 12.5 with 1 mol/L NaOH. The instantaneous precipitation was carried out in a closed system under C02-free N2 at 22°C. In this way, CO2 adsorption by the precipitate was minimized. 

The primary failure modality identified clinically for restorations in posterior teeth is loss of material through abrasion. The complex nature of this failure mode in composite materials makes it difficult to correlate this phenomenon with any one mechanical property. A number of studies have suggested improvements in the system by using various mechanical properties as evidence. These studies have identified major factors such as ceramic filler loading and type of filler [186-191]. Some effects have been identified related to the... 

Of the various synthetic processes that are available, two are of most relevance in the present context - precipitation from aqueous solution and melt forming. These methods are used where it is not possible to produce adequate products directly from natural sources. This will be because there is no suitable mineral, due to the chemical nature of the product, of particle size and shape requirements, or to purity considerations. The other principal synthetic method in use for filler production is pyrolysis/combustion. This type of process in which the particles are formed in the gas phase is used where very small particles are required, such as with carbon blacks and some silicas. This type of filler is not widely used in thermoplastics and so these processes are not discussed in any detail here, although some information specific to the production of antimony oxide will be found later. 

Heroin (Schedule I) is the acetylated form of morphine. The derivatization makes it more lipophilic and heroin therefore has about three times the potency of its morphine parent. Street heroin is rarely more than 10% heroin, the rest being some type of filler. The summer of 1989 saw what the L.A. Times reported as an "explosion" of Southeast Asian heroin with average purities of 48% to 51 %, much higher than is expected by the user. The purer heroin makes it easier to smoke, a practice used by crack addicts... 

Changes in bottle filler (e.g., change in weight of cotton or amount used) without changes in the type of filler (e.g., cotton to rayon). 

In the fust system the inner surface of a pre-made, open-necked bottle is sterilised. The sterility is maintained while the bottle is transferred to the aseptic filler. The layout of this type of filler is shown in Figure 9.1. The pre-made... 

The materials studied in63 65) can be regarded as binary or three-phase syntactic foams because they contain two types of filler, namely macrospheres and microspheres in 63), and macrospheres and glass fiber in 65). The latter may be called reinforced syntactic foams and have also been referred to as foamed glass-reinforced spheroplasts66 671 (see Sect. 4.11). 

Figure 8.5 Plot of volume fraction ratio Vro/Vrf characterizing the swelling of an unfilled PDMS network relative to that of a filled PDMS network, against filler loading expressed as volume ratio of filler to PDMS is the volume fraction of filler).40 Types of filler were silica-titania mixed oxides ( ), silica (O), and titania (A).

In composite systems, 2H NMR is particularly suited to investigate interfacial properties. Indeed, isolated nuclei are observed, which potentially allows spatially selective information to be obtained. It has been used to investigate polymer chain mobility at the polymer-filler interface, mainly in filled silicon (in particular PDMS) networks. The chain mobility differs considerably at the polymer-filler interface, and this may be interpreted in terms of an adsorbed polymer layer at the filler surface. T1 relaxation measurements allowed to determine the fraction of chain units involved in the adsorption layer, or equivalently, the thickness of the layer [75, 76, 77]. The molecular mobility and the thickness of the adsorption layer are very sensitive to the type of filler surface [78]. 

The rubber compounds prepared in this way are analysed and packed into polyethylene bags. Then they are loaded into metal cylinders or rubberised bags and sent to the consumer. Silicone rubber compounds can be stored for 3 to 6 months depending on the type of fillers and stabilisers. 

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