Melamine cross-linker

Preformed Two-Piece Metal Containers. Ink vehicles for letterset printing of two-piece aluminum or steel containers are mainly based on special polyester vehicles used in conjunction with melamine cross-linkers. Short cycle ovens which dry inks in 1—5 seconds are now used and operate at temperatures as high as 350 °C. The rheology of these inks must be adjusted to the unique geometry of the press. Desired rheological properties are achieved by the use of additives as weU as extender pigments. 

All resins except polybutadiene formulated with conventional melamine cross-linkers, applied to SAE 1010 bare steel paint test panels, and baked to yield cross-linked, solvent resistant films. 

A primer surfacer, composed most often of a polyester to be cross-linked with a blocked isocyanate or melamine cross-linker, is applied next at a dry film thickness of approximately 1.0 mil by conventional spray application. The function of this coating is to provide filling and leveling properties as well as some stone-chip resistance. Cure conditions range from 250 to 325°F for 20 min. 

Scheme 6.19 Acid-catalyzed condensation reaction of novoiac resins by melamine cross-linker.

Scheme 7.6 Cross-linking reaction between novolac and melamine cross-linker.

Figure 11.32 Dissolution rate curves for (a) an i-line DNQ/novolac resist, (b) a poly(hydroxystyrene)/melamine cross-linker resist (DUV 248-nm chemical amplification negative resist), and (c) poly(butylcarbonyloxy styrene-co-hydroxystyrene) (DUV 248-nm chemical amplification positive resist). The slope is the development rate log slope. ...

Urea—formaldehyde and melamine—formaldehyde reagents are resin formers, which not only cross-link cotton but also copolymerize with themselves. These have been used both as simple cross-linkers or prepolymer systems. If too much of the polymerization is concentrated on the fiber surface, the fabric may be sufficiendy stiffer that it takes on a boardy character. As such, the finisher must control the action of agent to give the desired crisp hand but prevent the development of boardiness. Melamines have been recommended for applications when complete shrink resistance is required. However, both finishes were rejected for the white-shirt market because of loss of strength when hypochlorite bleach is used on account of vulnerable NH groups and the ensuing discoloration (37). 

The polyacrylic copolymer (PAC) process incorporated new wall materials including proprietary emulsifiers and a melamine formaldehyde cross-linker (Figure 59.7). The polymers used... 

Amino Rosins. Melamine (l,3,5-triazine-2,4,6-triamine) [108-78-1] is reacted with formaldehyde [50-00-0] and alcohols to make melamine-formaldehyde (MF) resins, the most widely used cross-linkers for baked coatings. The ethers groups are activated toward nucleophilic substitution by the neighboring N. Hydroxyl, carboxylic acid, urethane, and phenols with an unsubstituted ortho position react (see Amino Resins). 

The melamine- and urea-formaldehyde resins are also called amino resins (118). The phenol-formaldehyde resoles are often called phenolic resins, which is rather easily confused with phenolic-terminated cross-linkers such as novolacs and bisphenol A terminated resins. 

The can and coil coatings, generally, are cross-linked with phenol, melamine, or urea-formaldehyde condensation products at elevated temperatures (150-200°C) with acid catalysts. Normal epoxy-amino resin weight ratios are epoxy-urea, 70 30 epoxy-benzoguanamine, 70 30 epoxy-melamine, 80 20, and 90 10. Increasing cross-linker levels give improved thermal and chemical resistance at the sacrifice of coating flexibility and adhesion. 

Vinyl acetal polymers can be formulated with other thermoplastic polymers and with a variety of multifunctional cross-linkers. Examples of polymers that are at least partially compatible with PVF or PVB resins include some types of polyurethanes, some types of celluloses, epoxies, isocyanates, phenolics, silicones, unsaturated polyesters, and melamine- and urea-formaldehyde polymers (19-21). Although vinyl acetal polymers are thermoplastic, hydroxyl groups permit cross-linking reactions with a variety of thermosetting resins, for example. 

By a surface imprinting technique, in Zhang H. et al., 2011, a comfX)site imprinted material, on the basis of a MWCNTs-incorporated layer using melamine as a template, methacrylic acid as a functional monomer, and ethylene glycol dimethaciylate as a cross-linker, was synthesized. In this work, the poly(acrylic-acid)-functionalized CNTs were synthesized to increase the diameter of CNTs. Then, the vinyl group was introduced to the surface of poly(acrylic-acid)-functionalized CNTs by an amidation Using Melamine as a template molecule, imprinted CNT composite material was fabricated by a thermal fX)lymeiization. Applied as a sorbent, the imprinted materials were used for the determination of Melamine in the spiked sample by online SPE combined with HPLC. 

Carter et al. [402] have addressed the chemical assessment of automotive clearcoats (usually melamine-cross-linked systems), which requires evaluation of the cross-linker type, HALS and UV absorbers. Coating systems require a variety of chemical analytical techniques for their evaluation [403], including UV microspectroscopy [402, 404], /xFTIR [402,405], /xRS [406,407], NMR [408], ESR [409], ToF-SIMS [410,411] and hydroperoxide titration [412]. Ideally, what is needed for industrial evaluation purposes is a set of techniques that can follow chemical changes in individual layers of a full automotive paint system, typically consisting of 45 /xm clearcoat, 25 /xm basecoat, 35 /xm primer, and 35 /xm E-coat on metal. The clearcoat must shield underlayers from UV. Unlike the case for IR radiation, examination of 30 /xm and thinner clearcoat layers with 0.3 to 0.4 /xm radiation lends itself quite well to the use of microscopes and microspectroscopic techniques. UV microspectroscopy of 10 /xm paint system cross-sections is the method of choice cfr. also Chp. 1.1). UV microspectroscopy... 

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