Crosslinked hand builders

Another category of durable hand builders are formaldehyde-containing thermosetting polymers. These products are usually supplied as dispersions or aqueous solutions of precondensates of urea or melamine with formaldehyde, for example di-methylol urea or di- to hexa-methylol melamine and their methyl ethers. The thermosetting polymers are comparatively inexpensive and provide fabrics with stiffness and resilience. However, they have a tendency to reduce abrasion resistance, yellow after exposure to heat, and release formaldehyde. Melamine-based hand builders are more highly crosslinked than urea-based products and are accordingly more durable. Butylated urea condensates are especially useful for rayon fabrics (see also Chapter 5 Easy-care and durable press finishes of cellulosics). 

Non-slip finishes are mostly applied by the pad-dry process, combined as needed with hand builders, repellents or cellulose crosslinkers (easy-care finish). The combination of silicic acid sols with softeners or silicone-based water repellents is crucial - their effects are contrasting. 

Uses Crosslinking agent, hand builder adding durability and resilience to fabrics (cellulosics, synthetics) adds durability to fluorochem. and water repellent finishes crosslinking agent for hydroxyl-contg. emulsion polymers for top coat systems, waterborne wood finishes, nonwoven binders... 

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