Acrylic fiber is thermoplastic (heat sensitive) similar to polyester and nylon, but is even more heat sensitive. Acrylic, because of its heat sensitivity, can be closely  made to resemble wool, due to its high bulking power. The fibers are strong, absorb very little water, and are resistant to most chemicals likely to be encountered in normal use.

High bulking acrylic yarn is produced by mixing high shrinkage fibers with low shrinkage/non-shrinkable acrylic fibers and then spinning it into a yarn.

When the yarn is subjected to steaming or hot air treatment, high shrinkage fibers shrink and force the non-shrinkable fibers to buckle, thus increasing the voluminosity of the yarn.            

For bulking, acrylic yarns are generally subjected to steaming for 20 min. Studies made with acrylic fibers found that yarns made of coarser fibers resulted in more voluminous yarns when treated in hot air as compared with steaming treatment. The best crimp contraction for coarser yarns (i.e. carpet yarns) will be achieved by hot air treatment with approx. 100°C for approx. 10 seconds.

With our Power-Heat-Set GVA equipment you can determine individually the temperature and the duration of the hot air treatment. Additionally, with a Power-Heat-Set type 5000, e.g. a GVA 5000 belt version, you can mix the bulking process by using the first chamber for the hot air treatment and the second chamber of the GVA 5000 for steam treatment.

Acrylic Balking with Power-Heat-Set equipment based on Internet research results with following links:
[1] http://cms.americanthreadcleaners.com.content/view/4/37  [2] http://personalpages.manchester.ac.uk/staff/mike.wilding/Textile%20Materials/Handouts/MATS-10061-FJW-B11-Acrylics-Elastomerics.pdf