Qualitative detection of formaldehyde in coatings and decorative materials

Formaldehyde ( HCHO ) is a colorless, irritating and water - soluble gas. It has the effect of solidifying proteins, and its 35% to 40% aqueous solution is called Formarin, often as a solution for impregnated specimens. Formaldehyde is a highly toxic substance, ranking second on the priority control list of toxic chemicals in China. The International Agency for Research on Cancer (IARC) upgraded formaldehyde to a class 1 carcinogen in 2004. The findings come after 26 scientists from 10 countries evaluated existing evidence of carcinogenicity in formaldehyde
china
.
expert group concluded that there is sufficient evidence that formaldehyde can cause nasopharyngeal, nasal and sinus cancers in humans, and that formaldehyde can cause leukemia. In 2006, the U.S. Department of Health and Human Services QA and the Department of Public Health issued a report on carcinogens, formaldehyde included in a class of carcinogens. Under certain conditions, indoor air formaldehyde detection concentration can be gathered above the standard allowable level, and the release period is relatively long, a study by Yokobin National University in Japan shows that indoor formaldehyde release period is generally 3 to 15 years!1 The main source of formaldehyde in residents' homes
formaldehyde comes from artificial sheets such as plywood, carpentry board, medium density fiberboard and particle board for interior decoration. Because formaldehyde not only has a strong adhesion, but also can increase the hardness of the material, at the same time has anti-worm, anti-corrosion function, so the current production of artificial board adhesive is formaldehyde as the main component of the formaldehyde resin, plate residue and non-reaction formaldehyde will gradually release to the surrounding environment, resulting in indoor air formaldehyde content exceeds the standard.
formaldehyde comes from furniture made from artificial panels. Some furniture manufacturers in pursuit of profit, the use of unqualified sheets, or manufacturing process irregularities, so that furniture has become formaldehyde emission station. Beijing Consumer Association conducted a comparative test results show: in Beijing extracted 60 sets of medium density furniture, There are 29 sets of formaldehyde exceeded the relevant national standards, non-conformity rate as high as 48.23%. Formaldehyde comes from decorative materials, such as white latex, foam, paint and paint. Such as some water-based adhesive free formaldehyde exceeded the standard, some white latex actual formaldehyde content exceeded nearly 5 times. Latex adhesive in decoration is widely used in wood engineering and wall treatment, closed in the wall formaldehyde is difficult to remove.
formaldehyde comes from interior decoration textiles, bedding, wallpaper, chemical fiber carpets, curtains and fabric furniture. In textile production, In order to increase the anti-wrinkle performance of textiles, waterproof performance, fire resistance, often added additives containing formaldehyde. In July 2004, the State Administration of Quality Supervision and Inspection of 149 kinds of bedding, individual products formaldehyde detection content is 50 times the standard limit. National 5 textile formaldehyde content limit 6 regulations, direct contact with the skin bedding and indoor (including cars, boats, aircraft) supplies, such as sofa covers, bedspreads, wall cloths and other formaldehyde content to be strictly controlled. Formaldehyde comes from cosmetics, detergents, pesticides, disinfectants, preservatives, printing inks, paper, etc.
with the improvement of human self - protection consciousness and the continuous progress of industrial technology, some formaldehyde- and industrial products are gradually replaced by environmentally friendly products. China has also continuously introduced corresponding standards to limit the content of formaldehyde in products, but because formaldehyde-containing products have cheap and anti-corrosion characteristics, by some ungratical enterprises or individuals to use, pit harm consumers. Such as the use of formaldehyde content of water-soluble inner wall paint (containing 107 glue) posing as a similar sense of the outside latex paint (environmental protection, no formaldehyde), the use of Formarin (formaldehyde 40% water solution) for anti-corrosion treatment products, The use of industrial bleach "hanging white block" (formaldehyde sodium sulphate) as whitening agent to deal with wheat flour, etc. These problems have aroused great concern of china's quality inspection departments at all levels. In order to effectively protect the vital interests of consumers, we must take effective measures to strengthen the quality supervision and management of related products, water-soluble interior wall coatings, interior decoration materials formaldehyde identification inspection and content determination.2 Formaldehyde Detection
The test principle of formaldehyde qualitative testing is the principle of using formaldehyde in sulfuric acid solution to produce purple compounds, to test.
2. 1 Sample treatment formaldehyde extraction in
coating first called a well-mixed sample 2 g, placed in a distillation bottle added to 50 mL water, shake well, then add 200 mL water, using normal pressure distillation method to collect fractions 100 to 200 mL, spare.
formaldehyde extraction composite floor cut into 300mm x 150 mm block, all around with formaldehyde-free tape sealed into a small beaker, add 20 mL of water, put into 40 L dryer. Particle board, plywood, carpentry plate cut into 150 mm x 50 mm large block mounted on the iron frame.
2. 2 Qualitative test of formaldehyde
take the above formaldehyde extract 5 mL into the color tube, add 1 mL sodium chromate salt solution and 4 mL sulfuric acid, heating 3 to 5 min. If the solution from colorless or light yellow to purple, can be determined to contain formaldehyde.
2. 3 Rapid method and arbitration method comparison
acetylacetone method to measure formaldehyde method is more classic and accurate, but acetyl acetone needs to be re-distilled, the preparation of a good color agent preservation time is short, if only to know whether the sample contains formaldehyde, chromic acid method is more convenient.
acetyl acetone colorant itself is colorless or light yellow after reacting with formaldehyde only color deepening, while chromic acid method, color agent changes significantly, easy to observe.
if the formaldehyde content of the sample needs to be further tested, only the collection amount is extracted at the time of distillate collection, and the formaldehyde content is determined according to the corresponding test standards.