Oligomers formaldehyde resin

Template copolymerization seems to be applied to the synthesis of copolymers with unconventional sequences of units. As it was shown, by copolymerization of styrene with oligomers prepared from p-cresyl-formaldehyde resin esterified by methacrylic or acrylic acid - short ladder-type blocks can be introduced to the macromolecule. After hydrolysis, copolymer with blocks of acrylic or methacrylic acid groups can be obtained. Number of groups in the block corresponds to the number of units in oligomeric multimonomer. Such copolymers cannot be obtained by the conventional copolymerization. 

Processing of phenol-aldehyde oligomers into various articles is based on a polycondensation reaction which leads to solidification of the material at temperatures below 200°C and pressures exceeding 10 MPa. The process is accompanied by volatile product formation. However, phenol-formaldehyde resins of the resol type can be cast without additional pressure and heat. The raw molding reactants contain different organic and mineral fillers and other additives in addition to the basic resin. 

Resorcinol-phenol-formaldehyde resins are produced by combining phenol with formaldehyde, under mild alkaline conditions, before the resorcinol is introduced. Thus these resins may be considered to be a resorcinol-modified resole type and would be a mixture of oligomers something like that shown in Figure 1. 

Figure 1. Resorcinob-phenol-formaldehyde resin oligomers...

The expression (29) points to the existence of proportionality between the reciprocal value of the gelation time and the rate constant Figure 33 presents the interrelation between 1/t and the rate constant determined from the rheokinetic equation for the curing of melamine-formaldehyde oligomer. The value of the proportionality factor determined from the data of Fig. 33 coincides with the value calculated from Eq. (29). In particular, for melamine-formaldehyde resin investigated in Ref. [81], Eq. (29) assumes the form ... 

Urea-formaldehyde resin solutions are shown to be dominated by physical associations rather than primary chemical bonding. These physical associations, or colloidal dispersions, are directly related to the thermodynamic balance of secondary bond formation between resin and solvent systems. Steric and entripic evaluations of molecule configuration have shown that linear urea-formaldehyde oligomers resemble polypeptides, and have the potential to form both 3-sheets and n-helixs, While the exact configuration of the associations is not known, their presence has been confirmed by x-ray analysis, which shows that urea-formaldehyde resins are crystalline in solid form. 

The intermediate oligomers such as 13 were then subjected to methylolation with formaldehyde to form phenolic-furanie-formaldehyde resins, according to ... 

Urea, (p-ethoxyphenyl)-. See Dulcin Urea, 1,3-ethylene. See 2-lmidazolidinone Urea/formaldehyde adduct Urea/formaldehyde condensate Urea/formaldehyde copolymer Urea/formaldehyde oligomer Urea/formaldehyde polymer Urea/formaldehyde precondensate Urea/formaldehyde prepolymer. See Urea-formaldehyde resin Urea-formaldehyde resin CAS 9011-05-6... 

Synthetic polymers can be classified as thermo-plasts, which soften under heat and can be reversibly melted, and thermosets, which by the action of heat or chemical substance undergo chemical reaction and form insoluble materials that cannot be melted. Mixtures of molecules of relatively low molar mass (hundreds to thousands) that are able to react mutually or with other compounds and form cross-linked materials are often called synthetic resins. That is, synthetic resins such as epoxy or polyester or phenol-formaldehyde resins are thermosets. The term oligomer refers to a polymer molecule with relatively low molar mass (roughly below 10 000 g mol whose properties vary significantly with the removal of one or a few of the units. 

Epoxy group functionalized polyphenylsilsesquioxane oligomers were used for modification of phenol-formaldehyde oligomer (novolac resin -SF-0112) for increasing their flexibility, their hydrophobic surface properties, thermal stability and flame-retardant properties. Novolac resin - SF-0112 contains a little amount of free phenols (0.9%) compared with other phenol-formaldehyde oligomers. 

Pol)merization reaction of phenol-formaldehyde oligomer (novolac resin - SF-0112) with tetraepoxypolyphenylsilsesquioxanes was carried out in melt condition at 125 5°C temperature at various ratios of initial compounds, without catalyst. The samples were tested on contain of epoxy groups during the reaction. It was shown that during synthesis of block-copolymers the reaction rate decreases, which may be explained by presence of free phenols in used phenol-formaldehyde oligomer. In accor-... 

Figure 3.7 shows an example of an oligomer separation achieved by this method for various POE-HPLC has also been applied to the determination of oligomers in polyesters [34], alkylphenyl formaldehyde resins [35, 36] and polyethylene terephthalate [37, 38]. 

The natural resins present in native guayule have been extensively studied and include mono-, sesqui-, di-, and triterpene groups, as well as other secondary metabolites (108). Unfractionated guayule resin has shown considerable promise in the areas of wood preservation (in marine and terrestrial environments) (129) and insect antifeedents (termite resistance) (130-132). These resins also show promise as a biobased renewable replacement for petroleum-based monomers and oligomers in adhesives and coatings. Additional profitable uses for the resins include a natural, low toxicity replacement for creosote in wood treatment and for prevention of termite attack. Resin/lignin products, such as additives for phenol formaldehyde resins, may also prove possible. 

The performance of several column packings has been assessed and it has been stressed that low eluent flow rates are necessary for high performance separation. The effects of water contamination in eluents has been studied by Berek et a/. " highlighting the need for rigorou dried systems. Phase equilibria studies in polymer-polymer-solvent systems have proved feasible using a dual detection system and could be extended in the future. Other applications are concerned with copolymer analysis, polydispersity, oligomers, and melamine-formaldehyde and urea— and phenol-formaldehyde resins. New techniques, recycle liquid SEC, phase-distribution chromatography, and the measurement of diffusion coefficients from GPC have been described. 

Phenol-formaldehyde polymers, including novolaks and resoles, have a number of applications in coatings, finishes, adhesives, composites, laminates and related areas. Concerns have been raised regarding the continued use of phenol-formaldehyde resins due to the various toxic effects of formaldehyde. Consequently, there has been active investigation for alternative sources of these types of oligomers and polymers with a consideration for environmental compatibility. 

FIGURE 13.11 First stage in the polymerization of formaldehyde resins. The oligomers that are formed are mixtures whose composition depends on the proportion of reactants and the reaction conditions. 

The mobility of the hydrogen atom in the —SH group conditions polysulfide oligomer modification with phenol-formaldehyde resins, so that the following chemical reaction occurs [89] ... 

Introduction of phenol-formaldehyde resins improves polysulfide oligomer ad-hesivity. In these composites, the preferred curing agent is PbOj. 

Averko-Antonovich, L. A., Muhudnikova, T. E., and Kirpichnikov, P. A., Polysulfide oligomers modification using phenol-formaldehydic resins, Cauciuk i Rezina, 1975, No. 4, p. 18 (Russian). 

---