Chemical Finishing Agents Questions and Answers

Answer: A

Correct answer: lubricating the fibres so they slide

A softener deposits a lubricating layer on the fibre surface, reducing the friction between fibres and between yarns so that the fabric bends and drapes more readily and feels smooth. Nothing about the fibre itself changes. That also explains the usual side effects - a lubricated surface is more easily soiled and, with cationic softeners, less absorbent.

Answer: B

The ionic class decides both the softness delivered and what the softener can be combined with. A cationic softener on a brightened white is the classic incompatibility to avoid. Silicones are the premium option of the four.

Answer: C

Both are true and the reason gives the mechanism: the two carry opposite charges, and non-ionic or specially selected products are used where a high white must be kept. The loss appears only after the softener is applied.

Answer: D

The first two are correct. The third is exactly the difficulty, since the opposite charges cause precipitation or quenching, which is why compatibility must be checked before use. Yellowing shows up after heat or long storage.

Answer: A

The lubricity reduces needle heat and seam damage, which matters in garment manufacture. They cost more than conventional softeners and can cause spotting if the emulsion is not stable. Seam damage falls markedly with a silicone.

Answer: B

The crosslinks hold the chains in place so the fabric recovers its shape after bending. The price is a loss of tensile and tear strength, which is the central compromise of the finish. Crease recovery is bought at the cost of strength.

Answer: C

Both are true and the reason gives the mechanism: the same rigidity that gives crease recovery prevents the fibre from yielding, so strength losses of a quarter or more are normal and are accepted as part of the trade.

Answer: D

The first two are correct and are the classic trade-off. The third is wrong, since abrasion resistance falls along with the other strength properties for the same reason. The trade-off is unavoidable with this mechanism.

Answer: A

Correct answer: formaldehyde, now tightly restricted

The classic durable press resins are N-methylol compounds, which release free formaldehyde during curing and slowly afterwards in storage and wear. Formaldehyde is an irritant and a recognised carcinogen, so release limits are set by legislation and by retailer specifications, and the industry has moved to low-release and free formaldehyde chemistries.

Answer: B

Correct answer: improved tear strength

Crosslinking the cellulose is what gives the crease recovery, but the same crosslinks stop the chains sliding past one another when the fabric is stressed, so tensile and tear strength both fall - often by a third or more, and abrasion resistance with them. Moisture absorption falls too, since the crosslinks occupy hydroxyl groups that would otherwise bind water.