Thermosetting resins introduction

GIM is particularly suitable for predicting the change in polymer properties observed upon introduction of a diluent into a thermosetting resin. Firsdy, the model... 

Introducing toughness to thermoset resin systems 13.1.9.1 Introduction... 

I have divided this book into seven chapters. It starts with a general introduction to thermosets, which includes network concept, additives and techniques/instrumentations (their principles) used to characterise a thermoset resin. The chemistry, properties and applications of individual thermoset resins are discussed in Chapters 2 and 3. Chapters 4 and 5 deal with the modification of thermoset resins for improvement in fracture toughness. The thermoset-based composites and nanocomposites are... 

Amino resins are thermosetting polymers made by combining an aldehyde with a compound containing an amino (—NH2) group. Urea—formaldehyde (U/F) accounts for over 80% of amino resins melamine—formaldehyde accounts for most of the rest. Other aldehydes and other amino compounds are used to a very minor extent. The first commercially important amino resin appeared about 1930, or some 20 years after the introduction of phenol—formaldehyde resins and plastics (see Phenolic resins). 

Since the introduction of the first commercial thermoset, Bakelite, based on phenol formaldehyde condensation, a wide range of thermoset materials have been introduced. These are typically designed for specific properties related to their chemistry and processability. Some commercially important thermosets include phenolics, ureas, melamines, epoxy resins, unsaturated polyesters, silicones, rubbers, polyurethanes, acrylics, cyanates, polyimides, and benzocyclobutenes. ... 

Figure 33-4. Relationship between the growth, G (in % increase in production per year) and age, A (in years), of an industry since the introduction of the first large-scale technological process. For thermoplasts and thermosets, PL, this is the commercial phenolic resin synthesis, for glass, GL, it is the bottle production by molding process, for aluminum, Al, it is the electrolysis process, for paper, PR, it is the paper machine, and for iron, Fe, it is the use of coke. (After G. R. Snelling.)...

For a general introduction, see Wood adhesives - basics. Aminoplastic resins are polycondensation products of the reaction of aldehydes with compounds carrying amine or amide groups. Formaldehyde is by far the primary aldehyde used. The name amino-plastic is traditional, but is a misnomer these are thermosetting, irreversibly hardening resins. Two main classes of these resins exist urea-formaldehyde (UF) resins and melamine-formaldehyde (MF) resins. Today, for wood adhesives, pure MF resins are not used anymore because of cost, and only melamine-urea-formaldehyde (MUF) adhesives are used. The main use of these resins is in composite products such as particle board, plywood, medium density fibreboard (MDF), oriented strand board (OSB), glu-lam/flngerjointing and furniture. 

Krigbaum [12] has reported on the use of glass fiber-reinforced composites based on Cyglas 685 unsaturated polyester BMC and Cyglas 695 vinyl ester resin BMC (Cytec Industries) in automotive valve covers and other engine cover applications. He reviews development programs that led to the successful introduction of these components. The recyclability of thermoset composite valve covers is also discussed. 

Thermosets may be omitted In some lists of high performance polymers but they meet specifications and would not be used today If they were not high performance material. This criterion applies to carbon fibers, barrier resins, thermotropic polyesters, interpenetrating network polymers and many specialty elastomers. Likewise, the introduction of UV/EB curing techniques has brought about a new era in the polymer industry. 

The different resin systems differ in terms of their degradation behavior. Each particular class of thermosets (epoxy resin, unsaturated polyester resin, etc.) combines a variety of structurally and chemically different systems that will be discussed in the following introduction. 

Gel time and peak exothermic temperature are two of the most important parameters for a thermosetting material processor. Gel time is the interval of time between introduction of the catalyst and the formation of gel. Such information regarding viscosity change with time of resin-catalyst mixture helps to determine... 

Mechanics. Structural Foam (SF) uses the same basic approach as injection molding for conveying the material to the mold when thermoplastics are the raw material. Thermosets can be induced to foam as well, and this approach normally uses equipment associated with the RIM process. The uttiqueness of this process approach stems from the introduction of inert gases or reaction prodnct gases that disperse into the resin inside of the closed mold. These gases have two major effects upon the part—an increase in stiffness and a reduction of the material s density or specific gravity. 

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