Composite resins classification

While the thermally regenerable plum pudding resins can be classified as composite resins without ambiguity, the authors are of the opinion that it may not be appropriate to use such a classification for thermally regenerable no-matrix resins. Unlike the plum pudding resin, which is obtained by blending two independent resins in an inert matrix, the no-matrix resin is devoid of aify inert matrix and refers to a polymer matrix in which the weakly acidic and weakly basic domains are segregated. 

This chapter is concerned with the essential classification of the materials used to repair teeth and restore their function. As far as direct restoratives are concerned, we follow the classification on Mount et al. [1] and consider that the two basic types of modem tooth-coloured materials are the composite resins and the glass-ionomer cements. They are fundamentally different, and though hybrids have been attempted, combining their advantages is not feasible for sound scientific reasons. 

As we have seen, in the classification of tooth-coloured dental restorative materials, the composite resins represent one of the major types [1,6], The other major type is the glass-ionomer cement. 

The size range of the filler particles was the basis of an early classification of composite resins [102], Though the range of particle sizes has now been extended to include nano-particles [103], this is still a useful approach to classifying these materials. Table 3.1 shows the order of development of composite resins based on the particle size of their fillers. 

F. Lutz, R.W. Phillips, A classification and evaluation of composite resin systems, J. Prosthet. Dent. 50 (1983) 480-488. 

It is traditional to divide phenolics into two main categories. These are novolacs and resoles. This system of classification is consistent with the division of applications as well as the compositions and conditions of resin manufacture. Novolacs are used primarily in the molding industries and electronics applications. Resoles are used primarily as binders for other materials. 

However, it has to be considered that it is neither the content of free formaldehyde itself nor the molar ratio which eventually should be taken as the decisive and the only criterion for the classification of a resin concerning the subsequent formaldehyde emission from the finished board. In reality, the composition of the glue mix as well as the various process parameters during the board production also determine both performance and formaldehyde emission. Depending on the type of board and the manufacturing process, it is sometimes recommended to use a UF-resin with a low molar ratio F/U (e.g. F/U = 1.03), hence low content of free formaldehyde, while sometimes the use of a resin with a higher molar ratio (e.g. F/U = 1.10) and the addition of a formaldehyde catcher/depressant will give better results [17]. Which of these two, or other possible approaches, is the better one in practice can only be decided in each case by trial and error. 

Fiber-Matrix Composites. As shown in Figure 1.75, there are two main classifications of FMCs those with continuous fiber reinforcement and those with discontinuous fiber reinforcement. Continuous-flber-reinforced composites are made from fiber rovings (bundles of twisted filaments) that have been woven into two-dimensional sheets resembling a cloth fabric. These sheets can be cut and formed to a desired shape, or preform, that is then incorporated into a composite matrix, typically a thermosetting resin such as epoxy. Metallic, ceramic, and polymeric fibers of specific compositions can all be produced in continuous fashions, and the properties of the... 

Resin composites can be classified according to filler particles as fine-particle, hybrid, microhybrid and microfilled other classifications such as flowable or packable are related to their manipulation [1-3]. Quartz and glass (several types) fillers in fine-particle composites have sizes of about 0.5 to 3 pm. Microfilled and hybrid composites contain colloidal silica particles of 0.01 to 0.02 pm diameter incorporated in the polymer matrix. The microfilled composites also contain these submicron particles in groimd 10 to 20 pm filler particles of the polymerized oligomers. The filler volume fraction for composite products varies widely from about 20% to 70%. Clinical selection of composites depends upon strength, wear resistance and esthetics needed for the particular tooth restoration. 

The Artificial Muscle Project draws people from a variety of disciplines. Indeed, the field of electroactivity is extremely interdisciplinary. Case in point for my first patent in this area, the examiner from the USPTO called me. Evidently, they had several meetings trying to decide which patent classification code it came under—chemistry or electrical engineering So they resolved the matter by putting the question to me. We chatted and I agreed that it was on the fence between the two areas, but since my background was stronger in chemistry, the main classification was placed in class 523/113, synthetic resins, subclass composition suitable for use as tissue or body member replacement, restorative, or implant. 

A special grade meets the demand for halogen-free materials for pultruslon, resin transfer moulding, filament winding, and hand lay-up processes, giving highly retarded composites at a comparatively low addition rate. With this additive, at approximately 50 parts per hundred resin (phr), the Epiradiateur NF 92-501 test - one of the most stringent in Europe - can be passed with a classification of Ml, where 250 phr is required with aluminium hydroxide. With epoxy resins, the same low smoke density is produced as with polyester laminates, at addition levels of 20-50 phr. The aviation standard FAR 25.8 53 can be passed with an addition of 25-35 phr. A liquid-form additive is available where no powder additive can be used. 

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