Chemical Finishing Agents Questions and Answers

Answer: C

Correct answer: True

Polycarboxylic acids, principally butanetetracarboxylic acid, crosslink cellulose through ester linkages and release no formaldehyde at all. They work, and they are used where the specification demands it; what has limited them is cost and the catalyst required. Low-release modified reactants are the more common compromise in ordinary goods.

Answer: D

Correct answer: lowering the surface energy of the fibres

Repellency is a surface energy effect: a finish with a lower surface energy than the liquid prevents the liquid spreading, so a drop beads up and rolls off. The interstices are deliberately left open, which is what distinguishes a repellent fabric from a waterproof coated one - the first still breathes, the second does not.

Answer: A

Both are true and the reason gives the distinction, which is why the two terms are not interchangeable and a garment specification has to state which of the two is wanted. Comfort depends on which of the two is chosen.

Answer: B

A soil release finish deliberately raises the surface energy so that water can carry soil away in the wash. The other three all lower it to make the surface repellent. Soil release and repellency pull in opposite directions.

Answer: C

Correct answer: a fluorochemical finish

Oil has a much lower surface tension than water, so a finish must have a lower surface energy still to repel it, and only fluorocarbon chemistry - with its densely packed CF3 groups - goes low enough. Waxes and silicones repel water perfectly well and are wetted by oil, which is exactly the distinction the next item turns on.

Answer: D

Correct answer: 1 and 2 only

Statements 1 and 2 are correct: fluorochemicals repel both liquids, and the long chain C8 types have been restricted because their perfluorooctanoic degradation products are persistent and bioaccumulative, driving the shift to C6 chemistry and to non-fluorinated alternatives. Statement 3 is wrong - silicones repel water well and oil hardly at all.

Answer: A

The phosphorus promotes charring rather than flaming combustion and survives repeated laundering. Borax systems work but wash out, so they suit only disposable or rarely washed articles. Durability is what the phosphorus systems add.

Answer: B

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the cause. Borax and boric acid are effective and cheap flame retardants but they are simply deposited on the fibre, with no covalent bond and no insolubility to hold them, so the first wash removes them. They are therefore used on disposable and non-launderable goods, while durable flame retardancy needs a reactive phosphorus finish or an inherently flame resistant fibre.

Answer: C

Substantial add-on and crosslinking are needed for durability, and both affect the handle. This is why inherently flame resistant fibres are preferred where the requirement is severe. Add-on levels are high for a durable finish.

Answer: D

Bacteria and fungi cause both smell and, in natural fibres, actual rotting. Regulatory approval of the active agent is a significant part of bringing such a finish to market. Odour control is the largest single application.