CN1540315A - Method for scatheless analyzing content of formadldehyde in man-made board rapidly - Google Patents

Abstract

Characteristic absorption peak of formaldehyde is measured by using THz-TDS device. Then, regression equation for unprocessed wood same to sample to be tested is prepared. Content of formaldehyde in sample is obtained by inserting processed THz spectrum of sample to be tested in time domain into the said regression equation. The method does not harm the sample, and invention shortens measuring time and provides more accurate result.

Description

The quick nondestructive analytical approach of content of formaldehyde in the wood-based plate

Technical field

The present invention relates to the analytical approach field, specifically, the present invention relates to a kind of THz of utilization time-domain spectroscopy content of formaldehyde in the artificial board is carried out the method that quick nondestructive is analyzed.

Background technology

Along with the raising of people's living standard, a lot of families fit up indoor, in beautify life, have also brought serious indoor pollution problem, wherein are mainly derived from the content overproof of indoor free formaldehyde.Artificial board such as most employing Lauxite when making such as scale board, core-board, medium density fibre board (MDF) and particieboard as finishing material are tackifier, add the performance that excess formaldehyde can improve sheet material in the tackifier.The formaldehyde boiling point is-21 ℃, be easy to evaporate under the room temperature, and release period reaches 3-15.An our grade artificial board of domestic production is equivalent to European E at present ₂Grade, and the E in Europe ₂The grade wood-based plate then requires to seal under the condition of finishing and uses.So the content of formaldehyde for artificial board should carry out strictness control.

The assay method of burst size of methanal has following several in the world at present: perforation method, WKI (wide-necked bottle mensuration), drying basin method, eudiometry, big sensing chamber method, 1m ³Test box method, air circulation method, suction method etc., it is similar with step that it detects principle, all is at first to collect the free formaldehyde that discharges from testing sample, uses chemical method then, as iodimetric titration, diacetone colourimetry, electrochemical process, the formaldehyde that assay determination is collected.The common drawback of these methods is analysis time long (4 hours to 6 weeks), complex operation, and environmental factors such as measurement result and temperature are relevant, and the formaldehyde total content that can't know material is to assess the formaldehyde release duration.In addition, these detection methods belong to and diminish analysis, detect and finish, and material can not be used again, therefore, can only spot-check detection.

Based on the THz time-domain spectroscopy (THz-TDS) of femtosecond laser is a kind of new technique of development in recent years in the world.Because formaldehyde is polar molecule, its dipole rotates has absorption in the THz frequency range, and the THz ripple is transparent for most of dielectric materials, very little for the timber absorption of drying, therefore can utilize the THz time-domain spectroscopy to come PARA FORMALDEHYDE PRILLS(91,95) to detect.

Summary of the invention

The quick nondestructive analytical approach of purpose of the present invention with regard to being to provide a kind of THz of utilization time-domain spectroscopy that the content of formaldehyde in the artificial board is measured, not only minute is very short for it, and can not destroy sample.

For reaching this purpose, the quick nondestructive analytical approach of utilizing the THz time-domain spectroscopy to content of formaldehyde in the artificial board of the present invention, may further comprise the steps: 1, utilize the THz-TDS device to measure the THz time-domain spectroscopy figure of formaldehyde, carry out Fourier transform, again ordinate is taken the logarithm, obtain the characteristic absorption peak of formaldehyde; 2, get the rough lumber identical with testing sample, measure its THz time-domain spectroscopy figure, spectrogram carries out Fourier transform, compares to determine not having covering with the formaldehyde characteristic absorption peak after ordinate being taken the logarithm again; 3, get the sample of several known content of formaldehyde, carry out respectively with the same processing of step 2 after, utilize BIPTCHEM software to carry out match and obtain regression equation; 4, get testing sample and survey its THz time-domain spectroscopy figure, carry out Fourier transform, the substitution regression equation obtains content of formaldehyde after ordinate being taken the logarithm again.

Utilize method of the present invention can directly measure content of formaldehyde in the artifical board material (non-release amount), not only can not cause damage to sample, and step 1 wherein～3 can be carried out in advance, only need carry out 3 and 4 step when need measuring like this, compare and to shorten detection time widely with existing content of formaldehyde assay method, the process of analyzing a sample only needs 2 minutes, and the result is relatively accurate.On this project achievement in research basis, if can be with the miniaturization of THz radiation detection instrument, portability and commercialization, the market of then bringing is big, economic benefit high-leveled and difficult to estimate.Other the harmful polar molecule such as the mensuration of toluene and ammonia in the also suitable artificial board of the present invention.

Description of drawings

Fig. 1 is the THz time-domain spectroscopy of blank sample;

Fig. 2 is the THz time-domain spectroscopy of beech plate;

Fig. 3 is the THz time-domain spectroscopy of formaldehyde gas;

The frequency spectrum that Fig. 4 takes the logarithm through Fourier transform for the THz time-domain spectroscopy of unprocessed beech plate, formaldehyde and blank sample again, wherein A is a formaldehyde, and B is blank, and C is unprocessed beech material.

Embodiment

Below by specific embodiment, so that the THz of utilization time-domain spectroscopy of the present invention is described further the method that content of formaldehyde in the wood-based plate carries out the quick nondestructive analysis.

Experimental apparatus and principle

The THz-TDS device is the titanium jewel femto-second laser of Spectra-Physics's manufacturing and the THz system of U.S. Zomega company development, and spectral measurement ranges is 0.1-4THz (wavelength 3.3mm-80 μ m), signal to noise ratio (S/N ratio)＞1000, and spectrum is differentiated and is better than 10GHz.

The collection of illustrative plates test condition is: laser power is 0.75W, and pulse width is measured offset voltage 16.18KHz less than 100fs, and the phase-locked time is 30ms, and temperature is 22 ℃, and air humidity is 41%.

Principle: according to Lambert-Beer's law $1g\frac{I_0}{I}=\mathrm{abc},$ Wherein $\frac{\mathrm{<figure-callout\; id="0"\; label="I\; I"\; filenames="A20031010814500081.png"\; state="\{\{state\}\}">I</figure-callout>}}{I_{}}=T,$ T is a transmissivity, and c is a measured matter content, and a, b are constant, and Fig. 4 ordinate is 1gT; The content of formaldehyde is linear in the intensity of formaldehyde absorption peak and the sheet material, promptly $c=\frac{-1\mathrm{gT}}{\mathrm{ab}}.$ Therefore can be from figure data obtain the content of formaldehyde in the wood-based plate sample.

Embodiment 1

A certain amount of paraformaldehyde is placed in the five phosphorous oxide exsiccators dry a couple of days, in the 100ml round-bottomed flask, adds an amount of paraformaldehyde then, oil bath to 175 ℃, gas is collected with polythene film bag.At first survey blank sample THz time-domain spectroscopy figure with the THz-TDS device, its result as shown in Figure 1; Each later on THz time-domain spectroscopy figure that measures makes the difference spectrum with it.THz time-domain spectroscopy figure (direct light path focusing place that sample is placed on device of surveying polyethylene film and the Polythene Bag of formaldehyde gas being housed, scan), utilize THz time-domain spectroscopy process software (U.S. Zomega company) that two time domain spectrums are differed to subtract and obtain the difference spectrum, influence with the deduction polyethylene film, obtain the THz time-domain spectroscopy figure of formaldehyde, its result as shown in Figure 3; Fig. 3 is carried out Fourier transform, ordinate is taken the logarithm again, can obtain formaldehyde has a characteristic peak (see figure 4) at 1.6THz.

Embodiment 2

Take by weighing crude beech plate 100 grams, survey its THz time-domain spectroscopy figure with the THz-TDS device, its result as shown in Figure 2, spectrogram carries out Fourier transform equally, ordinate is taken the logarithm, make comparisons with known formaldehyde characteristic absorption peak then, do not have the covering (see figure 4) to determine itself and formaldehyde characteristic absorption peak; Get the known beech particieboard of content of formaldehyde (five concentration of formaldehyde c1～c5 be respectively 110,130,150,170, the every 100g sheet material of 190mg/) of five 100 grams, measure their THz time-domain spectroscopy figure respectively, carry out Fourier transform again and ordinate is taken the logarithm, the intensity at record peak, 1.6THz place is designated as Y ₁～Y ₅Utilize BIPTCHEM software (U.S. UMETRICS company) to carry out the regression equation that match obtains the beech plate:

Y(1E+24)＝2.52-0.0125c，

Its coefficient of multiple correlation R is 0.994 (the R value more approaches 1, and fitness better).

Embodiment 3

Get 100 grams beech particieboard to be measured again and survey its THz time-domain spectroscopy figure, spectrogram obtains data Y after handling equally, and the above regression equation of substitution obtains content of formaldehyde c ' wherein;

Simultaneously the plank test specimen in identical source with acetylacetone colorimetry to compare: it is hot altogether with toluene to get 100 gram beech particieboards, by liquid-solid extraction formaldehyde is disengaged in plank, the toluene that will be dissolved with formaldehyde then carries out liquid-liquid extraction by perforator, formaldehyde is changeed soluble in water, content of formaldehyde in the water is analyzed with the diacetone colourimetry, obtain content of formaldehyde c wherein ", its concrete outcome is as shown in table 1:

	Content of formaldehyde (mg/100g material plate)	Detection time	Whether need the perforation extraction
				The THz-TDS method	??145.1	2 minutes	Not
The diacetone colourimetry	??139	4 hours	Be

By above result as seen, under the situation that is ready to formaldehyde characteristic absorption peak and content of formaldehyde mensuration equation in advance, the needed minute of method of the present invention is very short, only needs a few minutes to get final product; And its accuracy also will be higher than other method (the diacetone colourimetry is because extraction is not thorough, and the content that records usually is lower) accordingly.

Embodiment 4

Change the beech material into the cypress material, repeat the step of embodiment 2, the concentration of formaldehyde accounting equation (regression equation) that obtains the cypress material is:

Y(1E+24)＝2.60-0.0105c，

Its coefficient of multiple correlation R is 0.992

And then get cypress material to be measured and measure its THz time-domain spectroscopy figure, spectrogram obtains data Y after handling equally, the accounting equation of concentration of formaldehyde in the substitution cypress material, and the content of formaldehyde that obtains wherein is a 157.3mg/100g material plate.

Embodiment 5

Change the beech material into masson pine timber, repeat the step of embodiment 2, the concentration of formaldehyde accounting equation that obtains masson pine is:

Y (1E+24)=2.35-0.0120c, its coefficient of multiple correlation R is 0.997

And then get cypress material to be measured and measure its THz time-domain spectroscopy figure, spectrogram obtains data Y after handling equally, the concentration of formaldehyde accounting equation of substitution masson pine, and the content of formaldehyde that obtains wherein is a 149.6mg/100g material plate.

Claims (2)

1, the quick nondestructive analytical approach of content of formaldehyde in a kind of artificial board is characterized in that may further comprise the steps:

(1) the THz time-domain spectroscopy figure of mensuration formaldehyde carries out Fourier transform, ordinate is taken the logarithm again, and obtains the characteristic absorption peak of formaldehyde;

(2) get the rough lumber identical with testing sample, measure its THz time-domain spectroscopy figure, spectrogram carries out Fourier transform, compares to determine not having covering with the formaldehyde characteristic absorption peak after ordinate being taken the logarithm again;

(3) get the sample of several known content of formaldehyde, carry out respectively with the same processing of step 2 after, the intensity at record formaldehyde characteristic absorption peak place utilizes BIPTCHEM software to carry out the regression equation that match obtains calculating content of formaldehyde;

(4) get testing sample and survey its THz time-domain spectroscopy figure, carry out Fourier transform, the substitution regression equation obtains content of formaldehyde after ordinate being taken the logarithm again.

2, the quick nondestructive analytical approach of content of formaldehyde in the artificial board as claimed in claim 1 is characterized in that wherein step (1)～(3) can be used as preliminary work and carry out in advance.

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