Monitoring and Preventive Countermeasures of Formaldehyde in Wood Furniture

With the acceleration of the urbanization process, people's awareness of environmental protection has been continuously enhanced with the improvement of living standards and material conditions. Consumer demand has driven the demand for wooden furniture to increase. However, the excessive formaldehyde in wooden furniture has seriously affected people's health. Monitoring and prevention of its quantity has become a top priority.

1 Analysis of formaldehyde source in wooden furniture

Wood furniture is often supplemented with a large number of artificial boards in the production process, and the materials are glued together. Therefore, the main sources of formaldehyde are as follows:

(1) formaldehyde inherent in wood; (2) unreacted free formaldehyde remaining in the artificial board of the auxiliary material, or formaldehyde generated by resin degradation; (3) adhesive used in veneering of furniture (such as urea-formaldehyde resin glue, phenolic resin) Part of formaldehyde remaining in rubber, melamine resin, etc.; and (4) residual veneer material for wooden furniture, residual formaldehyde in various coating materials, covering fabrics, fillers (such as fabrics, leather, sponges, etc.) .

2 The harm of formaldehyde to the human body

Formaldehyde is a colorless, water-soluble irritating volatile gas. It is an important chemical raw material for the manufacture of phenolic resin, urea-formaldehyde resin, vinylon, malotropine, dye, etc. The residual formaldehyde in wooden furniture material is slowly released within 3a. For the peak period, the release period is within 3~5a, and the residue can be completely removed after 15a. Therefore, its harm is long-lasting. The latest research shows that the human body has been exposed to low-level formaldehyde (0.01~0.68mg/m3) for a long time, which can cause skin allergies, dermatitis, nose, throat, throat discomfort, loss of appetite, about 0.07 mg/m3, which will cause children to occur. asthma. Formaldehyde is a protoplasmic toxic substance that binds to proteins. In the case of excessive absorption, it can be severely mucosal ulceration, spasm, neurasthenia, loss of liver and kidney function, and can also cause neonatal chromosomal variation, high concentration of formaldehyde or genotoxicity. Substance, even carcinogenic (such as nasal cancer, nasopharyngeal cancer, oral cancer).

3 Investigation and monitoring of formaldehyde emission in wooden furniture

The problem of excessive formaldehyde in wooden furniture was first seen in the results of the sampling of formaldehyde sold in 70 companies published by Shanghai Liberation Daily in August 2001. Half of the products exceeded the standard by the perforation method, reaching 40~114mg/100g. According to the survey, in the first half of 2001, about one-fifth of the consumers in 15 cities in China caused diseases due to the smell of furniture purchased. According to the data provided by relevant medical institutions, the average number of nasopharyngeal patients registered in Zhuzhou City's outpatient clinics in 2007, 2006 and 2005 was 4.3 percentage points higher than that in 2004, 2003 and 2002. Based on the above reasons, the authors investigated the situation of excessive formaldehyde in several major furniture markets in Zhuzhou City. Judging according to the national standard GB18584-2001, see Table 1

3.1 Monitoring method: dryer method

3.2 Monitoring process

(1) Specimen sample collection: Through random sampling of 51 batches of test pieces in Zhuzhou City's 4 major furniture markets [10 pieces per test piece, specification 15.0×5.0cm (length × width)], immediately use formaldehyde-free aluminum The tape is sealed and placed in a vinyl bag and placed in an incubator (20 ° C, 24 h) for inspection.

(2) Formaldehyde collection: A crystallizing dish (diameter 12cm, height 6cm) with 300ml distilled water is placed at the bottom of the dryer with a volume of 11L and a diameter of 24cm. The upper test pieces are not in contact with each other and are placed at a constant temperature of 20 ° C for 24 hours. The formaldehyde released from the test piece is absorbed, and the solution is used as a test solution.

(3) Quantification of formaldehyde: according to formaldehyde (10.0ml test solution) and acetylacetone (10.0ml, 0.4%) plus ammonium acetate (10.0ml, 20%) in a constant temperature (40 ° C + 2 ° C) water bath pot color 15 In the minute, the reaction at room temperature (23 ° C + 5 ° C, 1 h) produces diacetyl dihydrolutidine which is yellow-green with maximum absorption at 412 nm, with a 0.5 cm cuvette as a blank sample with distilled water, absorbance, and monitoring results. See Table 2.

From Table 2, it can be calculated that the excess test specimens accounted for 35.3% of the total random samples, that is, more than 30% were unqualified, of which plywood and joinery were the most. Almost every market has more than 25% of unqualified products.

4 Prevention and control measures for formaldehyde pollution of wooden furniture

National Mandatory Standard GB18584-2001 "Interior Decoration Materials. Limits of Hazardous Substances in Wood Furniture" was implemented in January 2002. According to the above-mentioned analysis and monitoring of the source, hazard and release amount of formaldehyde in wood furniture, the prevention and control of formaldehyde pollution of wooden furniture can be started from the following aspects;

4.1 Switch to environmentally friendly design

In the future, wooden furniture will no longer be satisfied with the use of functions, but should enhance the modern “eye-catching” function with beautiful, novel and individualized style, and make the “green furniture” and “green design” become fashionable.

Specific design (1) try to reduce the number of pieces of furniture, the combination of functions can be combined as much as possible to reduce the release of formaldehyde; (2) try to design removable furniture, reduce the adhesive structure, and directly reduce the amount of adhesive; (3) try to Reduce the amount of artificial boards, auxiliary materials, veneers, etc., reduce the thickness of the board (under the premise of ensuring strength and structure) and carry out edge sealing treatment (the amount of formaldehyde released from the end face is more than 2 times that of the plane, and the sealing ratio is not sealed. The amount of formaldehyde emission can be reduced by more than 4 times.); (4) Wood furniture should be made of natural solid wood materials, and combined with enamel structure or nails and joints, and internal paste paper containing water-soluble formaldehyde trapping agent (absorbable) Formaldehyde in the wooden interior of the furniture; (5) Try to avoid making furniture in winter, and make it well ventilated during painting. Excess plates, adhesives, paints, etc. should be thrown away as soon as possible; (6) Pack the doors and drawers as much as possible during packaging ( Avoid formaldehyde accumulation in confined spaces) and prevent some activated carbon from being detoxified.

4.2 Improve production process

Highly free formaldehyde is present in most of the suitable urea-formaldehyde glues (polycondensation products formed by the addition of urea and formaldehyde). The phenolic glue can be mixed with it to reduce the amount of formaldehyde released, or it can be mixed with isocyanate glue. Studies have shown that adding the right amount of tannins or sulfides (such as sodium thiosulfate, sodium dithionite, sodium dithionite, etc.), polyvinyl acetate can also reduce the amount of formaldehyde released from the board. In the subsequent treatment, the plate is sprayed with ammonia (three-stage treatment: ammonia absorption, dehydration, compounding) or the plate is sprayed with an aqueous solution containing an ammonium salt. Can effectively reduce the amount of formaldehyde released.

4.3 Improve the use environment

(1) Consumers should put the furniture for a period of time before use and put it in a high temperature and humid environment to accelerate the release and volatilization of formaldehyde.

(2) Raising some of the hanging orchids, aloe vera, green radish, and iron trees in the living room to absorb the formaldehyde released by the wooden furniture. (A study has shown that under 24h illumination, aloe vera and spider plant can fully absorb more than 80% of indoor formaldehyde.)

(3) Consumers should try to stay indoors during the first 3 years after purchasing furniture, and stay outdoors, and keep indoors fully ventilated.

5 Conclusion

From October 1, 2004, the national mandatory standard GB5296.6-2004 "Consumer Instructions for Use Part VI Furniture" clearly stipulates that furniture manufacturers should have instructions for use and indicate the amount of formaldehyde released. There is reason to believe that with the rise of wooden furniture with green environmental protection concept, with the awakening of manufacturers, sellers and people's self-protection awareness, the development and popularization of a new generation of formaldehyde-free and non-toxic furniture will not be too far away.

Table 1 Standard for Hazardous Substances in Wood Furniture (GB18584-2001)

Item limit value

Formaldehyde emission (Desiccator)

E1≤1.5mg/L

Heavy metal content (color limited paint)

Soluble lead

≤90mg/L

Solubility

≤75mg/L

Soluble chromium

≤60mg/L

Soluble mercury

≤6mg/L

Table 2 Monitoring Table for Formaldehyde Release of Wood Furniture in Zhuzhou City Furniture Market

market

Shenlong Furniture Market

Fengtai Furniture Plaza

Tianyuan Building Materials Market

Honggang Building Materials Market

Random sampling

bookcase

dining table

office

chair

Wooden sofa

Bedside table

Big cabinet

Blockboard

Particle board

bed

Medium density

Plywood

Number of test pieces

2

3

3

8

3

2

4

6

5

3

7

5

Average formaldehyde

1.927

0.715

0.601

0.217

2.303

1.749

1.141

2.858

1.371

0.566

0.734

3.655

Release amount (unit: mg/L)

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