Epoxy Modifiers

Aqueous dispersions are used in fiber bonding, paper coating, friction and abrasive appHcations, and laminates and wood bonding. PhenoHc dispersions improve the strength of latex-contact adhesive appHcations. Epoxy-modified phenoHc dispersions are prepared by dispersion of the phenoHc epoxy resin. The systems are used for baked primer appHcations and bonding requirements. Minimum baking conditions are 20 min at 150°C (25). 

The quantitative bulk conversion of unsaturated functional groups in PHAs to epoxides has been achieved by reaction with m-chloroperbenzoic acid as the chemical reagent [107]. No chain scission of the macromolecular chain was observed. Epoxy-modified PHAs are chemically even more reactive than unsaturated PHAs and therefore could be useful in further chemical reactions (e.g. grafting of therapeutic important substances) [108]. 

Adherent films would not necessarily require formation of covalent bonds at the Interface, since localized lntermolecul u dispersion forces that u e operative In the adsorption of coatings (with good wetting properties) should provide stable interfacial bond conditions. Among candidate materials which could fulfill the requirements of good adhesion and substrate protection from moisture are epoxy-modified polyurethanes and epoxy-siloxane polymers. 

Cement hydration and epoxy polymerization occur simultaneously to form a structure that is similar to the latex-modified cementitious system. Epoxy systems develop high strength, adhesion and have low permeability, good water resistance and chemical resistance. A major advantage of this system is that it can be cured under moist or wet conditions. According to a recent study, the epoxy-modified mortars can be made without the hardeners with superior properties to those obtained with conventional epoxy mortars [89, 90]. 

PEG-epoxy modified surface Streptavidin modified surface Ni " chelate modified surface... 

The control resin network used in this study was a diglycidyl ether-based epoxy resin crosslinked with a cycloaliphatic diamine. Cooligomeric modifiers were prepared having varying percentages of TFP and DP siloxane and aminoethylpiperazine end groups. Both siloxane and ATBN and CTBN elastomers were used as epoxy modifiers, the latter two having been included to facilitate direct comparisons between modifiers in similarly prepared networks. 

Fig. 5. Tan 8 as a function of temperature for epoxy modified with 10 weight percent of dimethyl/TFP siloxane oligomers...

Our interest in PDMS as an epoxy modifier lies partly in its low Tg relative to the ATBN and CTBN modifiers. Up to this time, however, improvements in K,c through copolymerization of dimethyl siloxane with TFP and DP siloxane require raising the Tg of the siloxane modifier above that of PDMS, as shown by Table 1. It is hoped that increased understanding and control of the synthesis and morphologies of siloxane-modified epoxies will make it possible to retain the low Tg of the modifier while raising the fracture toughness of the resin. The true value of this objective could eventually be shown by measurement of Klc at temperatures below ambient. 

In summary, we can first say that there is no significant evidence that the low surface energy siloxane-modified epoxies reduce friction compared with the unmodified epoxy or the ATBN- and CTBN-modified epoxies. Based on the results of the steel ball-on-epoxy experiments, the most significant effect of the siloxane modifiers is the reduction of the elastic modulus associated with large closely spaced domains. The longer initiation times and lowest wear rates observed for the siloxane-modified epoxies were generally associated with a lower modulus. Epoxy modified with the CTBN of 18% AN content also showed lower wear rates with lower modulus but, in contrast with the siloxane-modified resins, had shorter initiation times with lower modulus. 

Auad, M.L. Zhao, L.H. Shen, H.B. Flammability properties and mechanical performance of epoxy modified phenolic foams. J. Appl. Polym. Sci. 2007,104, 1399-1407. 

An epoxy-modified acrylic resin in n-butanol and xylol, sometimes with the addition of 2-ethoxyethanol. 

Adhesives formulated with epoxy-modified latex retain the tack and conformability of the original latex but show improvements in green bond strength and fully cured bond strength. Cured epoxy latex epoxy resin systems also exhibit improved water and chemical resistance over unmodified latex systems. 

Epoxy modified polymer latex systems offer improved handling performance and moisture and chemical strength advantages over unmodified formulations. The wide range of latex polymers and the range of waterborne epoxy dispersions offer the formulator a wide latitude in performance characteristics required by specific applications. 

Various adhesives can be used to bond polyphenylene oxide to itself or to other substrates. Parts must be prepared by sanding or by chromic acid etching at elevated temperature. Methyl alcohol is a suitable solvent for surface cleaning. The prime adhesive candidates are epoxies, modified epoxies, nitrile phenolics, and polyurethanes. Epoxy adhesive will provide tensile shear strength on abraded polyphenylene oxide substrates of 600 to 1300 psi and 1300 to 2200 psi on etched (chromic acid) substrates.71... 

Dawdy, T. H., Epoxy Modified Structural Adhesives Having Improved Heat Resistance, U.S. Patent 4,467,071 (1984). 

Fig. 13 is a TTT cure diagram of three systems a neat epoxy resin and the same epoxy modified with two reactive rubbers at the same concentration level. The times to the cloud point, gelation and vitrification are shown for each system. The cloud point is the point of incipient phase separation, as detected by light transmission. The modified system with the longer times to the cloud point and gelation, and the greater depression of Tg, contains the more compatible of the two rubbers. The difference in compatibility could then be used to account for differences in the volume fractions of the phase separated rubber-rich domains and in the mechanical properties of the neat and the two rubber-modified systems. 

Figure 103 The weathering resistance of epoxy-polysulphide coatings after one month of outdoor exposure [A] LP-epoxy modified coating [B] unmodified epoxy coating. Substrate = oily, rusty and wet mild steel. Reproduced with permission from Morton International...

Epoxies modified with acrylate functional urethane are suitable for application in coatings and adhesives. 

Morton International (undated b) ELP-3 Epoxy Modifier, product properties, Morton International Ltd, Coventry, UK. 

Epoxy coating is well suited for the separation of proteins in CE. This coating is easy to prepare and can be used for a broad range of pHs. High recoveries of proteins prove that this epoxy modified surface has reduced the protein adsorption significantly. 

As opposed to flexible urethane foams, rigid urethane foams have a highly cross-linked chemical structure and a high percent of closed cells, e.g., over 90%. Rigid urethane foams can be classified as follows unmodified (or pure) rigid urethane foams and modified rigid urethane foams, which include isocyanurate-modified, epoxy-modified, amide-modified and oxazolidone-modified rigid urethane foams. 

Polycarbonate Conventional adhesives recommended include epoxies, modified epoxies, polyurethanes, acrylics, RTV silicones, cyanoacrylates, one-part elastomers, some epoxy-polyamides, and hot melts (13). 

Cationic Photoinitiators for Curing Epoxy-Modified Silicones... 

Epoxy resin ester paint, Epoxy modified alkyl resin paint,... 

Besfight Prepreg - 100 series (epoxy modified), 300 series (bismaleimide modified)... 

It is seen that all three known types of distribution are observed experimentally. One can see that the nature of surface bonded groups of initial modified silica plays an important role. Namely, reactions between the amines studied and the bromopropyl-modified silica run according to the island-like mechanism. Whereas, both random and uniform coverages are more frequent for the tosyl- and the epoxy-modified silicas. 

In this paper, we report the preliminary results on the synthesis and properties of epoxy-modified ZrP. These materials show classical graded characteristics in composition, microstructure, and properties. The microstructure-property relationships in these novel FGMs are discussed. 

The as-received ZrP powder showed the wide range of particle size and distribution. The particle size ranged fi om submicron (0.05 m) to 50 (xm with a mean value of 1.8 xm and had surface area of 15.2 m /g. This wide range of particle size distribution has also been observed by several workers. The x-ray dififiaction spectra of pure ZrP powder and the epoxy-modified ZrP samples infiltrated for various times showed [5] the presence of high degree of crystallinity in as-received ZrP by virtue of the sharp reflection lines. The intensity of these lines decreased as the infiltration time or epoxy content increased, resulting in the broadening of peaks and the appearance of a broad but diffuse peak at 17°. 

---