Thermosets introduction

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). 

The principal types of rigid plastic, both thermoplastic and thermosetting, are listed in Table 2.1, which also lists the abbreviations used in this text. A more comprehensive introduction to polymers is available [1]. 

Increased demand for granulated thermosetting materials and their effective use necessitated the selection and utilization f the efficient methods known in the art or provision of new rational techniques for granulation of aminoplasts, development and introduction of highly productive equipment to meet the aforementioned requirements. 

The major trend observed is a modest increase in KIc or GIc by the introduction of initially miscible thermoplastics. This improvement is obtained without any loss in stiffness and thermal properties. Some very high improvements in KIc, claimed by some authors, are due to phase inversion, leading to a thermoplastic matrix with thermoset particles. 

Different ways of toughening thermosets may be employed such as the use of rubber block copolymers (Mulhaupt and Buchholz, 1996) or introduction of microgels (crosslinked microparticles) (Funke et al., 1998). 

I have included an introduction to rubber elasticity in Chapter 4 because it follows logically from considerations of conformational changes in polymers. This material need not be taught in the sequence presented, however, and this topic, or all of Chapter 4, can be introduced at any point that seems best to the instructor. Chapters 5 through 7 are quite orthodox in their plans. 1 have, however, taken the opportunity to present alkyd calculations as an example of practice in the coatings industry and formulating thermosetting materials. 

A brief description of the books contents may be helpful. Chapter 1 by M. Okoroafor and K.C. Frisch is an introduction and also covers the subject of foam formation. The chapter includes a discussion of the Montreal Protocol mandating the development of foams with substantially reduced CFC content by 1995. Chapter 2 is a comprehensive discussion of thermosetting foams of all types, with the emphasis on urethane and phenolic foams. The authors, K. Ashida and K. Iwasaki, are recognized authorities in their fields of specialization. This chapter presents extensive discussions of such fields as composites and syntactic foams. There is some overlap between this chapter and topics covered in later chapters, but the treatments are different. 

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. ... 

Brittle thermosets are best toughened by the introduction of a rubbery or thermoplastic dispersed phase (1-4). The dispersed phase can be produced by two methods in situ reaction and adding preformed particles. The first method is used much more because it is easy and it can create specif-... 

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

The introduction of nanoceramics in thermoplastics or thermosets seems to be a promising route to improving mechanical moduli, particularly of elastic matrices. The macroscopic properties are governed by the nature of polymer-nanoparticle interactions. In this chapter, specific attention will be paid to nanocomposites of polyamide (PA) with HAp. Considering their attractive viscoelastic properties, semiaromatic polyamides (e.g., PA-llTlO) have been chosen as the matrix [Choe et al., 1999]. Recently, several publications have been devoted to one-dimensional nanostructures with high-aspect-ratio particles. Promising data have been obtained for the polymer/nanowire-nanotube nanocomposites. 

Epoxy-based thermosets are the most widely used and versatile thermosets. They dominated the reinforcing piping field until the introduction of the vinyl esters, and they are still widely used. They find usage in many applications, including adhesives, coatings, encapsulants, tooling compounds, composites, and molding compounds. Their versatility is due to the wide latitude in properties that can be achieved by formulation. 

Part VI is totally new. It is an introduction into polymer technology and thus discusses thermoplasts, thermosets, elastomers, fibers, coatings, and adhesives with respect to their end-use properties. It also contains chapters on additives, blends and composites. 

Quasi-Static Loading of Thermosets and High Performance Composites - Introduction... 

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