CN102539372B - Method for detecting content of end carboxyl of para-position aramid fiber - Google Patents

Abstract

The invention relates to a method for detecting content of end carboxyl of para-position aramid fiber, which is characterized by including the following steps, using para-position aramid fiber as a sample S1, using para-position aramid fiber after neutralizing the end carboxyl as a sample S2, determining infrared sptectrograms of the sample S1 and the sample S2 respectively, using a difference spectrum and peak-differentiation imitation to obtain integral absorbance of an infrared spectrum of the end carboxyl, and calculating the content of the end carboxyl of the para-position aramid fiber. The method for detecting the content of the end carboxyl of the para-position aramid fiber is high in flexibility and simple in operation.

Description

A kind of detection method of content of end carboxyl of para-position aramid fiber

Technical field

The present invention relates to chemical industry detection method, be specifically related to a kind of detection method of content of end carboxyl of para-position aramid fiber.

Background technology

Because p-aramid fiber has the macromolecular structure of rigidity, possess the excellent properties such as high-strength, Gao Mo and heat-resisting, fire-retardant, insulation, therefore can be widely used in the fields such as space flight, aviation, protective clothes, tire, mechanical rubber, friction product and packing ring, hawser, individual protection.The content of p-aramid fiber end carboxyl has significant impact to the performance of the final products of this polymkeric substance, and the while is also for the analysis of number-average molecular weight provides foundation.Yet, do not have at present a kind of compared with the detection method of Accurate Determining content of end carboxyl of para-position aramid fiber.

Summary of the invention

In order to overcome above-mentioned defect, the invention provides a kind of detection method of content of end carboxyl of para-position aramid fiber highly sensitive, simple to operate.

The detection method of content of end carboxyl of para-position aramid fiber of the present invention, it comprises the steps:

Take p-aramid fiber as sample S1, the p-aramid fiber of take after neutralization end carboxyl is sample S2, the infrared spectrum of working sample S1 and sample S2, utilizes poor spectrum and swarming matching to draw the integrated absorbance of holding carboxyl infrared spectrum respectively, calculates the content of carboxyl end group of p-aramid fiber.

Wherein, with W ₁the potassium bromide of g and W ₂the sample S1 of g fully mixes, and gets W ₃the infrared spectrum of the potpourri compressing tablet working sample S1 of g; Sample S2 is mixed with arbitrary proportion with potassium bromide powder, with the infrared spectrum of pellet technique working sample S2, with following formula, calculate content of end carboxyl of para-position aramid fiber F (molg ^-1):

$F=\frac{A\×\mathrm{\π}\×r^2}{1000{\×\mathrm{\ϵ}\×W}_3\×\frac{W_2}{W_1\×W_2}}---\left(1\right)$

Wherein, A is the integrated absorbance (infrared spectrum absorpting peak area) of end carboxyl infrared spectrum, the pore radius that r is compression mold (cm), and ε is the absorptivity (Lmol of end carboxyl ^-1cm ^-1).

Wherein, formula (1) is derived and is drawn by langbobier law, and detailed process is as follows:

According to langbobier law,

$A=\∫\lg \left(\frac{I_0}{I}\right)\mathrm{dv}=\mathrm{\ϵ}\×l\×C---\left(2\right)$

Know,

$C=\frac{A}{\mathrm{\ϵ}\×d}=\frac{n}{V}---\left(3\right)$

Therefore,

$n=\frac{A\×V}{\mathrm{\ϵ}\×l}=\frac{A\×l\×S}{\mathrm{\ϵ}\×l\×1000}=\frac{A\×S}{\mathrm{\ϵ}\×1000}---\left(4\right)$

Therefore, the content of p-aramid fiber end carboxyl is

$F=\begin{array}{c}n\\ W\end{array}=\begin{array}{c}\frac{A\×S}{\mathrm{\ϵ}\×1000}\\ W_3\×\frac{W_2}{W_1\×W_2}\end{array}=\begin{array}{c}A\×\mathrm{\π}\×r^2\\ 1000\×\mathrm{\ϵ}\×W_3\×\frac{W_2}{W_1\×W_2}\end{array}---\left(5\right)$

Wherein, A is the integrated absorbance (infrared spectrum absorpting peak area) of end carboxyl infrared spectrum, I ₀for incident light intensity, I is transmission light intensity, and v is wave number, and l is the thickness (cm) of KBr print, and C is the concentration (molL of end carboxyl in KBr print ^-1), n is the molal quantity (mol) of KBr print middle-end carboxyl, and V is the volume (L) of KBr print, and S is die hole area (cm ²), W is the quality (g) that KBr print contains p-aramid fiber.

In addition, with in the ethanolic solution of inorganic metal highly basic salt and end carboxyl.

Wherein, described inorganic metal highly basic salt is potassium hydroxide or NaOH.

In addition, before neutralization end carboxyl with sweller swelling p-aramid fiber.

The dimethyl formamide solution of the lithium chloride that the weight percentage that wherein, described sweller is lithium chloride is 2.5%.

In addition, the particle diameter of described p-aramid fiber is below 0.05mm.

The described object that filters out the former powder of p-aramid fiber below particle diameter 0.05mm be for make the former powder of p-aramid fiber in sweller fast, minute fill swelling.

The former powder of p-aramid fiber that can select with washing lotion washing before detection is to remove the monomer of not participating in polycondensation reaction.Washing lotion is anyly can dissolve organic solvent or its combination do not participate in the monomer of polycondensation reaction and not dissolve p-aramid fiber, preferred lower boiling solvent or its combination, methyl alcohol for example, acetone, ethanol one or a combination set of.

Described sweller is for making any solvent or its combination, the preferably dimethyl formamide solution of 2.5% lithium chloride of p-aramid fiber swelling.The object of swelling is in order to make to hold carboxyl completely, be neutralized fully.

With in the ethanolic solution of inorganic metal highly basic salt and end carboxyl, the preferred potassium hydroxide of described metal overbase salt or NaOH.After neutralization, can wash filter residue to remove the neutralizing agent of not participating in neutralization reaction with distilled water.

The detection method of content of end carboxyl of para-position aramid fiber of the present invention is highly sensitive, simple to operate.

Accompanying drawing explanation

Fig. 1 is the infrared spectrum of end carboxyl of the p-aramid fiber after poor spectrum and swarming process of fitting treatment of embodiment 1.

Embodiment

Following examples are used for illustrating the present invention, but are not used for limiting the scope of the invention.

Embodiment 1

Filter out the former powder of p-aramid fiber below particle diameter 0.05mm, with acetone and the washing of ethanol combination liquid, filter, filter residue is dried as sample S1.

The former powder of p-aramid fiber of getting 0.5g washing same as described above, filtration, dry processing is placed in the dimethyl formamide solution swelling of 2.5% lithium chloride, after swelling, add wherein in the ethanolic solution of NaOH and end carboxyl, then filter, with distilled water, wash filter residue, after oven dry as sample S2.

Get 0.0596g potassium bromide powder and 0.0103g sample S1, mix and grind evenly, getting this potpourri 0.0266g, to be placed in diameter be the mould compressing tablet of 0.35 centimetre, utilizes BRUKERVECT33 to carry out Fourier transform infrared spectroscopy test, obtains the infrared spectrum of sample S1.Utilize conventional pellet technique to record the infrared spectrum of sample S2.By difference, composed with swarming fitting technique and processed this two spectrogram, obtain holding the infrared spectrum absorpting peak (Fig. 1) of carboxyl, its integrated absorbance is 22.13.Therefore, the content of carboxyl end group of this p-aramid fiber sample is:

$\frac{22.13\×3.14{\×0.35}^2}{1000\×217000\×0.0266\×\frac{0.0103}{0.0596+0.0103}}=10.01\×{10}^{-6}\mathrm{mol}\·g^{-1}$

Embodiment 2

Filter out the former powder of p-aramid fiber below particle diameter 0.05mm, with acetone washing, filter, filter residue is dried as sample S1.

Get 0.5g and sample S1 described in washing same as described above, filtration, the dry former powder of p-aramid fiber of processing is placed in to the dimethyl formamide solution swelling of 2.5% lithium chloride, after swelling, add wherein in the ethanolic solution of NaOH and end carboxyl, then filter, with distilled water, wash filter residue, after oven dry as sample S2.

Get 0.0626g potassium bromide powder and 0.0082g sample S1, mix and grind evenly, get this potpourri 0.0308g and be placed in the mould compressing tablet that diameter is 0.35cm, utilize BRUKERVECT33 to carry out Fourier transform infrared spectroscopy test, obtain the infrared spectrum of sample S1.Utilize conventional pellet technique to record the infrared spectrum of sample S2.By difference, composed with swarming fitting technique and processed this two spectrogram, obtain holding the infrared spectrum absorpting peak of carboxyl, its integrated absorbance is 12.40.Therefore, the content of carboxyl end group of this p-aramid fiber sample is:

$\frac{12.40\×3.14{\×0.35}^2}{1000\×217000\×0.0308\×\frac{0.0082}{0.0626+0.0082}}=6.36\×{10}^{-6}\mathrm{mol}\·g^{-1}$

As can be seen from the results, infrared spectrum is for the content detection of p-aramid fiber end carboxyl, and structure is sensitive, simple to operate.

Claims (1)

1. a detection method for content of end carboxyl of para-position aramid fiber, is characterized in that, comprises the steps:

Take the p-aramid fiber of particle diameter below 0.05mm as sample S1, then with sweller swelling p-aramid fiber, take in the ethanolic solution of potassium hydroxide or NaOH and the p-aramid fiber after end carboxyl as sample S2, with W ₁the potassium bromide of g and W ₂the sample S1 of g fully mixes, and gets W ₃the infrared spectrum of the potpourri compressing tablet working sample S1 of g; With the infrared spectrum of pellet technique working sample S2, utilize poor spectrum and swarming matching to draw the integrated absorbance of end carboxyl infrared spectrum, with following formula, calculate content of end carboxyl of para-position aramid fiber F, unit is molg ^-1:

$F=\frac{A\×\mathrm{\π}\×r^2}{1000\×\mathrm{\ϵ}\×W_3\×\frac{W_2}{W_1+W_2}}$

Wherein, A is the integrated absorbance of end carboxyl infrared spectrum, the pore radius that r is compression mold, and unit is cm, and ε is the extinction coefficient of end carboxyl, and unit is Lmol ^-1cm ^-1; Described sweller is the dimethyl formamide solution of the weight percentage of the lithium chloride lithium chloride that is 2.5%.

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