application of attapulgite clay mineral modified by flame retarder in green building materials

18
Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials Liu Xiaoqi 1,a , Duan Xuechen, Shen Minghui 2,b , Chen Jienan 3,c 1 School of Resources and Bioengineering of Central South University, 410083 2 School of Materials Science and Engineering of Central South University, 410083 3 Institute of Biological and Environmental Science and Technology of Central South University of Forestry and Technology, 41008 a [email protected], b [email protected], c [email protected] Key words: Straw based panel; flame retardant; nano; attapulgite; aluminium hydroxide Abstract: In this thesis, the composite of aluminum hydroxide on the surface of natural one-dimensional nano minerals and the nanocrystallization of inorganic flame retarder (aluminium hydroxide) are achieved by hydrothermal method. The obtained nano-composite flame retarder is applied in the preparation of straw based panel to improve its flame retardant performance. After ultrasonic dispersion and complex purification with the addition of EDTA, the crude attapulgite clay minerals is put in acid solution of PH 2 or 3, where the surface of the complex is modified with the addition of cetyl trimethyl ammonium bromide (CTAB).Then add into it aluminum hydroxide of different amounts, to start the hydrothermal composite reaction and get aluminum hydroxide/ nano-attapulgite composite flame retarder. After the characterization by SEM the best hydrothermal reaction conditions for preparing aluminum hydroxide/attapulgite are obtained. The prepared nano composite flame retarder, the PF adhesive and straw shavings are mixed in different proportions and made into straw based panel by hot pressing. Then the study on the flame retardant performance and the mechanical properties of the straw based panel is carried out. 1.Introduction Our country is short of timber resources. With the constant rapid development of wood based panel industry, the shortage state of timber raw materials is becoming severer and severer in recent years. As a result, some wood based panel industries are in a state of no production or only half production, and the further development of wood based panel industry is much influenced. At the same time, timber raw materials of poor quality are widely used, causing a big influence in production quality. Under such circumstances, extensive attentions are paid to the technology of manufacturing panel of non-wood raw materials. Among which straw based panel manufacturing technology has been studied for many years both home and abroad, with proper solutions being found to crucial technical problems and gradual perfect in technology and production solution plans. The industrialization of straw based panel manufacture is obviously getting faster. Now the annual output of straw in our country is very great, something between 600 million and 700 million tons. But because of the great changes in the fuel structure in the countryside, and owing to the substantial decline of manufactures made of straw, a great amount of straw is burned on the side of field and road. The burning smoke causes traffic barriers in highways and aviation, Advanced Materials Research Vol. 298 (2011) pp 226-242 Online available since 2011/Jul/27 at www.scientific.net © (2011) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.298.226 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 130.207.50.37, Georgia Tech Library, Atlanta, USA-11/11/14,19:04:47)

Upload: jie-nan

Post on 14-Mar-2017

215 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

Application of Attapulgite Clay Mineral Modified by Flame Retarder in

Green Building Materials

Liu Xiaoqi1,a, Duan Xuechen, Shen Minghui2,b, Chen Jienan3,c

1School of Resources and Bioengineering of Central South University, 410083

2 School of Materials Science and Engineering of Central South University, 410083

3Institute of Biological and Environmental Science and Technology of Central South University of

Forestry and Technology, 41008

a [email protected], b [email protected], [email protected]

Key words: Straw based panel; flame retardant; nano; attapulgite; aluminium hydroxide

Abstract: In this thesis, the composite of aluminum hydroxide on the surface of natural

one-dimensional nano minerals and the nanocrystallization of inorganic flame retarder (aluminium

hydroxide) are achieved by hydrothermal method. The obtained nano-composite flame retarder is

applied in the preparation of straw based panel to improve its flame retardant performance.

After ultrasonic dispersion and complex purification with the addition of EDTA, the crude

attapulgite clay minerals is put in acid solution of PH 2 or 3, where the surface of the complex is

modified with the addition of cetyl trimethyl ammonium bromide (CTAB).Then add into it

aluminum hydroxide of different amounts, to start the hydrothermal composite reaction and get

aluminum hydroxide/ nano-attapulgite composite flame retarder. After the characterization by SEM

the best hydrothermal reaction conditions for preparing aluminum hydroxide/attapulgite are

obtained.

The prepared nano composite flame retarder, the PF adhesive and straw shavings are mixed in

different proportions and made into straw based panel by hot pressing. Then the study on the flame

retardant performance and the mechanical properties of the straw based panel is carried out.

1.Introduction

Our country is short of timber resources. With the constant rapid development of wood based

panel industry, the shortage state of timber raw materials is becoming severer and severer in recent

years. As a result, some wood based panel industries are in a state of no production or only half

production, and the further development of wood based panel industry is much influenced. At the

same time, timber raw materials of poor quality are widely used, causing a big influence in

production quality. Under such circumstances, extensive attentions are paid to the technology of

manufacturing panel of non-wood raw materials. Among which straw based panel manufacturing

technology has been studied for many years both home and abroad, with proper solutions being

found to crucial technical problems and gradual perfect in technology and production solution plans.

The industrialization of straw based panel manufacture is obviously getting faster.

Now the annual output of straw in our country is very great, something between 600 million

and 700 million tons. But because of the great changes in the fuel structure in the countryside, and

owing to the substantial decline of manufactures made of straw, a great amount of straw is burned

on the side of field and road. The burning smoke causes traffic barriers in highways and aviation,

Advanced Materials Research Vol. 298 (2011) pp 226-242Online available since 2011/Jul/27 at www.scientific.net© (2011) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.298.226

All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 130.207.50.37, Georgia Tech Library, Atlanta, USA-11/11/14,19:04:47)

Page 2: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

and even flies to town to bring harm to the respiratory health of residents. The most obvious is the

severe wastewater pollution of small-scale straw pulp mill, which is strongly forbidden by the

government. What is more, the burning will produce a great amount of carbon dioxide, which

heavily increases the greenhouse effect. Crop straw contains considerable organic fibers, some even

equal to the content of hardwood. Manufacturing wood based panel by crop straw could make good

and useful things out of wastes. It can also replace woods and thus relieve the stress of wood

supply.

The use of crop straw to make panel in the world could date back to early 20th

century. The

study and practice of using adhesive and straw to make panel emerged in Germany. Then there

were research institutions and personnel starting study on straw based panel manufacturing

technology in Europe and North America. With the depth of the study and the improvement of

technology, Europe and North America maintained a mature straw based panel manufacturing

technology and started industrialization one after another. The Britain COMPAK company in

Europe had constructed nearly 20 manufacture lines in south Asia and Africa, while in North

America; a high tide of industrialization of straw based panel arose in 1990s. The United States and

Canada established more than ten factories of straw based panel manufacture in succession.

However, owing to multiple reasons such as technology and capital, most factories met financial

crisis and were hard to run, some even going bankrupt. The process of industrialization promoted

by technology in Europe and North America was hampered, and the development of straw based

panel manufacturing was slowing down,

In 1970s, our country started study on manufacturing panel by raw materials such as straw,

wheat straw, bagasse and flax tow. Among them, bagasse and flax tow were promoted to

application to some extent. Nevertheless, owing to the limitation of relative technology and

influence of market factors, no deeper study was carried on. Till 1990s, with reference to the

developmental situation of other countries and the application of isocyanate resin, the research on

manufacturing panel by wheat straw and straw was rapidly developed. At the same time, the

shortage of raw wood materials was becoming increasingly obvious and severe, and the harm of

straw burning was gradually appearing. Under the market and policy status, wheat straw and straw

based panel manufacture in our country stepped into a state of industrialization.

Chinese Academy of Forestry, Nanjing Forestry University and Northeast Forestry University

had made progress and breakthroughs in research and development, and carried out researches and

small-scale practices in industrialization technology. In the 21st century, some companies noticed

the developmental prospect and enormous social and economic value in straw based panel industry,

and started to devote to the industrialization of straw based panel. In recent years, straw based panel

manufacture companies such as Sichuan Guodong, Hubei Jili, Jiangsu Dasheng, Huaian Dingyuan

and Shandong Tongsen were founded. Either absorbing foreign technologies or combining with

strong national research institutions, they carried out the first practice of large-scale

industrialization of crop straw based panel manufacture. Besides, provinces like Jiangsu, Anhui and

Heilongjiang also have projects under construction.[28]

Flame retarder is also called fire retardants, flame retardants or fire retarding agent.

Being a special kind of auxiliary chemicals that can change the combustion performance of

combustible and inflammables, it is widely used in the flame-retardant processing of various

decoration materials. After flame-retardant processing, the materials, when attacked by

external fires, could efficiently prevent, delay or stop the transmission of fire and make a

function in flame retardancy.

Advanced Materials Research Vol. 298 227

Page 3: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

According its application mode, flame retarder can be divided into additive flame

retarder and reactive flame retarder. Directly mixed with resin or adhesive, additive flame

retarder is easy in processing and wide in usage. It is the main body of flame retarder.

Reactive flame retarder is always bonded to the chain of polymers as monomer, having small

influence on product performance and a long effect on flame retardancy. According to

components, additive flame retarder mainly includes inorganic flame retarder and halogen

flame retarder (organic chlorides and organic bromides) Phosphorus flame retarder (red

phosphorous, P-16 and halogenated phosphate and etc.) and nitrogen flame retarder, etc. Reactive

flame retarder is mainly the monomer of organic halogen and organic phosphorous that

contains reactive functional group. In addition, Molybdenum compounds, tin compounds and

ferrum compounds which can suppress smoke are included in flame retarder as well.

Flame retarders are mainly used in plastics with flame retardant requirements. They can

delay or prevent the combustion of plastics, especially macromolecule plastics, increase

their combustion time, enable them to self-extinguish and be hard to inflame. Flame retarder

must be added into inflammable macromolecule plastic such as PP, PA, PE, PS, ABS, EVA,

PET and PBT, for special use.

At the present, flame retarder is mainly organic and inorganic, halogen and halogen free.

Organic flame retarder is represented by bromides, nitrogens, red phosphorous and

compounds. Inorganic flame retarder is mostly aluminium hydroxide, Magnesium hydroxide

and silicons. Generally speaking, organic flame retarder has good affinity in plastics.

Bromide flame retarder has absolute advantage over other organic flame retarders. Though

having received many criticisms in environmental problems, it could hardly be replaced by

other flame retarders.

Red phosphorous is a fairly good flame retarder among halogen free flame retarders. It

has the advantage of small additives, high flame retardant efficiency, low smoke, low

toxicity and wide usage. Red phosphorous, with complex of inorganic flame retarder like

aluminium hydroxide and exfoliated graphite, is made into halogen free flame retarder of

composite phosphomagnesium, phosphoaluminium, phosphographite. It greatly decreases the

quantity of flame retarder, so as to improve the processing performance and physical and

mechanical properties of plastic products. However, red phosphorous is limited in use

because of its disadvantage of being easily oxidized, hygroscopic and easy to cause dust

explosion, hard to transport and poor compatibility with macromolecule materials. To make up for

those disadvantages, and expand the application scope of red phosphorous, our country

adopts the advanced Microencapsulation, and microencapsulates the red phosphorous. The

micro-encapsulated red phosphorous not only overcomes the inherent drawbacks of red

phosphorous, but also has high efficiency and low smoke. It does not produce toxic gases in

processing and its dispersion, physical and mechanical performance, thermal stability and

flame retardancy have all been developed and improved.[29]

With synthetic materials being widely used in various industries closely related to life and work,

such as building trade, plastic products, textile, transport, electrical and electronic industry and

aerospace industry, the importance of flame retarder even more can not be ignored. The

development of modern technology and the attention paid to worldwide safety and environment

protection increase the demand for flame retardancy of materials. Thus promotes the rapid

development of research, manufacture and promotion of flame retarder which results in the

emergence of more varieties and enormous increase in production. At present, according to a rough

estimate, 65%-70% of international flame retarder is used in flame retardant plastics, 20% in rubber,

228 Soft Magnetic Materials

Page 4: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

5% in textile, 3% in paint and 2% in paper and wood. In recent years, with the raising requirement

toward flame resistance and rapid development in plastic production, the used amount of flame

retarder in the globe is continuously increasing. In synthetic materials, inorganic flame retarder not

only resists combustion, but also suppresses the produce of smoke and Hydrogen chloride. Besides,

it enables the material to be free of toxin and causticity and low in cost.

After the prosperous development in early 1980s, the production and application of

flame retarder have stepped into a steady stage. With the development of Chinese synthetic

material industry and the continuous expansion of its application scope, flame retarder faces

a promising market in all fields including chemical building materials, electronic appliances,

transportation, aerospace, household furniture, interior decoration and basic necessities.

Moreover, fire extinguishment of coalfield, oil deposits and forest also promotes the produce

of flame retarder and fire resistant agent in China. Flame retarder has become the second

largest macromolecule material-modified additive, only less than Plasticizer in China.

Recent years witness a sustainable development in the manufacture and consumption of

Chinese flame retarder, the annual consumption growth from 2002 to 2004 being over 20%.

Started from 2002, the consumption of domestic flame retarder is increasing rapidly, majorly

owing to two aspects: electronic appliances and automotive markets.

The major consumed kind of domestic flame retarder is organic flame retarder, while the

production and consumption of inorganic flame retarder are relatively small. But in recent

years, it enjoys a good momentum of development and a potential market. Though halogen

flamer retarder, the most common flame retarder, has higher efficiency than other flame retarders,

its harm to the environment is also unnegelactable. Environmental problems are the focus of

auxiliary development and application providers. So the adaptation of product structure of flame

retarder is continuously made to deep the research on efficient eco-friendly flame retarder.

It is urgent to develop low smoke and toxin free inorganic flame retarder in China at

the moment. Magnesium hydroxide, as a kind of eco-friendly halogen free flame retarder, has a

broad application prospect. But presently, compared with foreign advanced product, domestic

magnesium hydroxide flame retarder has many defects. It has low efficiency in flame retardancy

and high filler content is required. It is easy to reunion and influences the mechanical properties of

basic materials. The industry needs to make greater efforts to develop advanced technology and

reduce production cost and product price.

The global consumption of flame retarder in 2005 is about 1.3 million tons. It can be

predicted that it will keep an annual increase of 3.5% until 2010. In 2005, the global sales of

flame retarder is about 3.5 billion dollars and the number will be 4.6 million in 2010 with an

annual increase of 5.6%.

Of Chinese flame retarder products in 2007, chlorine flame retarder accounts for 84%, while

low-smoke and non-toxic inorganic flame retarder products only accounts for 8%. Flame retarder

for construction use has a large potential market. At the moment, the variety and consumption of

flame retarder in China is far from the same as developed countries. With growing requirements of

flame retardancy technology, China will have more encouraging research and development

prospects of low-smoke and non-toxic inorganic flame retarder. [30]

Advanced Materials Research Vol. 298 229

Page 5: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

1. Flame retardant treatment of slate product

(l) Impregnation

Flame retardant treatment of wood based panel is based on its combustion and flame retardant

mechanism, and carried out by the choice of proper flame retarder in production process. Flame

retardant treatment of wood based panel could generally divided into processing treatment and slate

product treatment. Processing treatment is mainly the addition of various solid or liquid flame

retarders, while slate product treatment includes impregnation and surface veneer coating.

Put and soak the slate product in flame retarder solution under atmospheric or vacuum pressure

and then dry it in a temperature between 100 and 110℃. Divided into non-pressure cold bath

process and autoclave pressure process, this method requires technical equipment and costs a lot.

The greatest advantage of this method is no reagent loss. While its disadvantages are: ①a process

of slate product drying should be added after reagent impregnation; ②a limited and unsteady

amount of impregnation reagent can not ensure high flame retardancy; ③in impregnation process,

moisture content of reagent will break some fiber combination of the panel and reduce its strength;

④in impregnation process, dielectric will cause the fall off of wax, increasing the absorbent, hot

and cold bath process and autoclave pressure process could be used in impregnation treatment.

Reagent impregnation amount could reach 15% under an impregnation circumstance of 50%

concentration solution, 65℃ and 10 min.

(2) Surface treatment

Coat the flame retarder on the surface by brush, sprayer or roller coater. The coating can slowly

dry in the air or be made dry by hot air. The process is easy and cost is lower. This treatment has

little connection with panel-making technology and no technical impregnation equipment is needed.

Its easy operation satisfies the application in construction site. This treatment is used for

water-soluble flame retarder. Its disadvantages are: ①low surface productivity; ②hard escape of

inflammable volatile produced; ③influences on surface quality and limitation on its application;

④internal stress generated when heating will cause coating cracking; ⑤pressure of assembled gas

products produced in the decomposition of internal fiber will undermine the integrity of coating.

Pasting refractory materials on the surface of article board to form a protective layer of flame

retarder is also an efficient method to solve flame retardancy problem. It also improves the surface

quality and appearance of the article board.

2. Flame retardant treatment in panel-making process

(1) Fiber treatment

Mix the flame retarder solution with wet fibers in appropriate proportion (or add powder flame

retarder into wet fibers). Because of concentration gradient, the flame retarder will permeate into

the fibers in a short time. Because moisture brought by flame retarder will evaporate in fiber drying,

the moisture content of slab will not increase. When enough flame retarder is added uniformly,

Flame-retardant MDF that meets the requirements will be produced. The disadvantages of this

method are: ①thermal degradation of some flame retarder that may happen in fiber drying process

will reduce the flame retardant effect; ②the load of the dryer will be increased ; ③fiber strength

will be reduced in drying if the flame retarder is not of neutral or alkaline PH values; ④a storage

box of wet fiber is needed to provide enough time for the permeation of flame retarder into fibers;

⑤flame retarder solution causes hard control of fibers' reagent absorbing amount and leads to

waste. Meanwhile, reagent solution will pollute the environment.

230 Soft Magnetic Materials

Page 6: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

Mix the flame retarder solution with wet shavings in appropriate proportion (or add powder

flame retarder into wet shavings). Because of concentration gradient, the flame retarder will

permeate into the shavings in a short time. Taking this method, the moisture brought by flame

retarder will evaporate in shaving drying, so the moisture content of slab will not increase. When

enough flame retarder is added uniformly, product which meets the requirements will be produced.

This method has many disadvantages. The thermal degradation of some flame retarder that may

happen in shaving drying process will reduce flame retardant effect. The load of the dryer will be

increased. Shaving strength will be reduced in drying if the flame retarder is not of neutral or

alkaline PH values. A storage box of wet shaving is needed to provide enough time for the

permeation of flame retarder into shavings. Flame retarder solution causes hard control of shavings'

reagent absorbing amount and leads to waste. Meanwhile, reagent solution will cause environmental

pollution.

The advantages of this method are: ①the simple process requires no new equipment; ②the

flame retarder could be solid, liquid or emulsive with no limitation on its form; ③artificial control

over reagent amount and moisture content can be reached so that no waste will be caused;

④increase in drying capacity of fibers is not needed. The flame retarder spraying can be operated

before, after or at the same time with the spraying of adhesive. But this method requires a limitation

on the used amount of flame retarder, which is decided by the moisture content of resin. The more

amount of flame retarder is used, the easilier its precipitation and loss from the fibers will be caused.

Non-water-soluble flame retarder can not mix completely with adhesives, resulting in poor flame

retardancy. And with the moisture it brings in, the moisture content of slab will also be increased.

Besides, flame retarder and adhesive should have suitable PH values as good compatibility between

them is required.

By air paving equipment, a certain amount of flame retarder is paved into a part of the shaving

slab before its shaping. This method not only avoids flame retarder loss when being sanded, but also

enables the minimum flame retarder to have the greatest flame retardant effect. Simple though this

method, the physical and mechanical properties of article board will decrease in the process.

Besides, the addition of flame retarder is not suitable for all paving processes.

In this method, flame retarder must be suitable with adhesive to make no influences on its

curing time and bonding strength. The advantages are: ①it is simple and easy to operate; ②it costs

little with no changes on original production process and no addition of new equipment; ③the

uniform distribution of flame retarder on the fibers prevents flame retarder loss. While the

disadvantages are: ①moisture content of slab is increased to influence hot-pressing; ②sometimes

influenced by its PH values, the adhesive cures badly, so as to influence the physical and

mechanical properties of MDF; ③There is a limitation on the used amount of flame retarder.

2.... Experimentation

2.1 Experimental Apparatus and Materials

Experimental Apparatus: Ultrasonic Oscillator, Centrifuge, Thermostat Magnetic Mixer(85-2),

PH Meter (PHS-3C), Vacuum Drying Oven, FTIR Spectrometer, Electronic Balance①

ES-103HA(0.001g), Electronic Balance② ES-3000A (0.1g), Vacuum filter, X-ray Diffraction

Meter(D/max2500), Hydrothermal Reactor, Scanning Electron Microscope(SEM), Hot Press

Machine(100tons), Materials Mixer, Oxygen Index Tester(JF-3)

Raw Materials: Attapulgite Clay Powder, EDTA, CTAB, Concentrated Sulfuric Acid(98%),

Aluminium Hydroxide, Anhydrous Ethanol, Urea-Formaldehyde Resin, Straw Shavings

Advanced Materials Research Vol. 298 231

Page 7: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

2.2 Experimental Method

2.2.1 Experimental Flow

Ultrasonic Dispersing Aluminium Hydroxide

Complex Purification Hydrothermal Reaction

Clamping Adhesive

Cutting sampling

2.2.2 Experimental Procedure

(1) Ultrasonic dispersion

The ultrasonic oscillation creates a large amount of micro bubbles in the medium, which

form and grow in the zone of negative pressure in the longitudinal-wave propagation of ultrasonic

waves. In this process called “cavitation”, the instantaneous high pressure, more than 1000

Atmospheric Pressure and caused by the burst of bubbles, effectively strips off the impurities on the

surface of the attapulgite with its continuous impact and at the same time disperses the attapulgite

granules into rod crystal monomer. The compressing energy of ultrasonic waves, the expansion

impact of micro bubbles and the micro-jet flow effect produce the high-frequency vibration, which

with its diffusive force deep into the inside of crystal, speeds up the cleansing of adherents in the

slits of the crystal through high-speed compressing and diffusing motion and consequently leads to

the strong collision, aggregative friction and dispersion among attapulgite aggregates and improves

the effect of nanocrystallization.

Put the rude attapulgite ore and distilled water at a solid-to-liquid ratio of 1:100(10g rude attapulgite

ore powder into 1L distilled water) into the ultrasonic oscillator (BUG25-O6, BRANSON) and

obtain Solution A after one hour of ultrasonic oscillation.

(2) Complex purification

Add 3g EDTA into Solution A and put it into the magnetic agitator (85-2) for reaction for 12 hours,

after which the milky white solution turns into steel gray. Then put it in the centrifuge (LG10-2.4A)

for centrifugation for 8 minutes at the speed of 6000r/min. Pour away the supernatant fluid and take

out the subnatant solid. Add proper amount of anhydrous ethanol into it for vacuum filtration, then

recycle the solid (Circulation water vacuum pumpSHZ-DC3, made by Yuhua Instrument Factory,

Zhengjiang), dry and grind it in the vacuum drying oven at the temperature of 80 ℃ to obtain the

powder.

Crude

Attapulgite

Ore

Attapulgite

Powder

Nano-composite

flame retarder

XRD Test on

Purification Effect Straw

Shavings

Test on flame

retardancy

Flame Retardant

Straw Based

Panel

232 Soft Magnetic Materials

Page 8: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

(3) Hydrothermal reaction

Prepare acid solutions with pH values of 2 and 3 respectively (out of the sulfuric acid and distilled

water); add the materials into the prepared solutions as displayed in Fig.3 (with a solid-to-liquid

ratio of 1:20) and number them.

Fig. 2-3: Solution preparation in hydrothermal reaction

A:B

pH

2 3

5% Condition Ⅰ

Condition Ⅱ

10% Condition Ⅲ

Condition Ⅳ

Add 3g CTAB into the prepared solution for ultrasonic oscillation for one hour and put it into the

reaction kettle, after numbering, to leave it react for 48 hours in the vacuum dying oven at the

temperature of 180℃. Then take it out and leave it standing for 3 hours, pour away the supernatant

fluid and put the sediments for centrifugal washing 2-3 times (rotational speed 7500r/min, 8

minutes) and take out the subnatant sediments. After adding proper amount of anhydrous ethanol

into it, dry it in the blowing drying oven at the temperature of 80℃, then take out the dried

substance and grind it into fine powder in agate bowel and after numbering pack it for use.

(4) Preparation of Straw based panel

The process flow for preparing straw based panel is demonstrated in the flowing chart:

Materials Preparation mixing blank mold hot press demoulding panel

Prepare about 80g nano-composite flame retarder at the optimum condition decided in the former

procedure and three clamp formulations in which the nano-composite flame retarder is respectively

2%, 4% and 6% of the gross mass of the materials with the adhesive(PF) taking 16% of the gross

mass. The gross mass for each time of clamp is 630g. The obtained straw based panels are

numbered as Panel Ⅰ, Panel Ⅱ and Panel Ⅲ, as in the following figure:

Fig. 2-4 Clamp Formulation

Formulation

Flame

Retarder

percentage

Flame

Retarder

Mass

Adhesive

Mass

Straw

Shavings

Mass

Materials

Gross mass

① 2% 12.6g 100g 517.4g 630g

② 4% 25.2g 100g 504.8g 630g

③ 6% 37.8g 100g 492.2g 630g

④ 0% 0g 100g 530g 630g

Advanced Materials Research Vol. 298 233

Page 9: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

0 10 20 30 40 50 60 70

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Intensity

2 Theta

Process Flow for Production of Straw based panel:

Materials Mixing: Add straw shavings and then nano-composite flame retarder in the mixer for a

proper time and after mixing them uniformly add corresponding amount of adhesive in steps and

mix them uniformly each time.

Clamping: Pour the materials mixture obtained in the former step into the wooden mould with the

size of 300mm*300mm*10mm and disperse the glue lumps by hand to prevent the formation of

glue spots. After pressing it tightly by hand, put it into the 100tons hot press machine for hot

pressing for 10 minutes.

(5) Cutting and Sampling

After the hot-pressed straw based panel aging for 5-6 days in the laboratory environment, cut the

three straw based panels(300mm*300mm*10mm ) obtained for sampling respectively to obtain 10

pieces of the size of (120mm) * (10±0.5mm) * (5.0±0.5mm) out of each panel, which are used

for testing Oxygen Combustion Index. The sampling should be clean, level and smooth, without

bubbles, cracks, and burrs, etc. Scribe a line on the sampling for testing Oxygen combustion index,

50mm from the ignition end.

(6) Test on flame retardancy and mechanical property

Test the Oxygen index of the obtained samplings of straw based panels (3groups, 10pieces each

group) in the Oxygen Index Tester and recorded the test data to draw a preliminary conclusion on

the flame retardancy of the three straw based panels with different content of flame retarder.

Divide the samplings of straw based panels into 84 pieces and test the static bending strength and

internal bond strength of the sheet materials of straw based panel in the universal testing machine.

3. Results and Analysis

3.1 X-Ray Diffraction (XRD) Test

Fig.3-1 XRD of crude attapulgite ore Fig.3-2 XRD of crude attapulgite ore after

30%EDTA purification

Fig.3-1 and Fig.3-2 are the X-ray diffract grams obtained respectively on the crude attapulgite ore

and the crude attapulgite ore processed by EDTA of the mass fraction of 30% with the Cu target in

radiation condition K1 , in the XRD meter D/max 2500 with a working voltage of 40kV, a working

current of 250mA and the scanning range 2θ=0~80°in pace scanning.

0 10 20 30 40 50 60 7 0

0

500

1000

1500

2000

Intensity

2 T h e ta

234 Soft Magnetic Materials

Page 10: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

The XRD analysis shows that the grade of the crude ore is not high, about 20% to 30% and contains

large amount of impurities such as quartz, opal and illite, etc. which directly influence the

high-added value application of the attapulgite clay minerals. Therefore, it is needed to carry out

separation and purification, refining and nanocrystallization of the attapulgite clay to improve its

grade. In the XRD test, a strong absorption peak appears when d=0.3345nm, next to which is the

characteristic absorption peak of 2SiO , therefore, it is concluded that the main impurities in the

attapulgite clay minerals is 2SiO .

The characteristic absorption peak of attapulgite corresponds to where 2θ is 8.32º in Fig.3-1 and 2θ

is 8.24 º in Fig.3.1.2, while where 2θis 26.6 ºin Fig.3-1 and Fig.3-2 shows the characteristic

absorption peak of quartz. The comparison of the two Figures shows that the characteristic

absorption peak of quartz in Fig.3-1 is stronger than that in Fig.3.1.2, but the characteristic

absorption peak of attapulgite is stronger in Fig. 3-2. In another word, the content of quartz in the

attapulgite mixture processed by ultrasonic dispersion and purification with 30% EDTA decreases

while the content of attapulgite increases.

3.2 SEM Test

The purified attapulgite powder is mixed with other reagents according to the proportion in Table.3,

and the sampling of aluminium hydroxide/nano-attapulgite composite material. Since aluminium

hydroxide does not conduct electricity, the scanning of its surface appearance is carried out after

metal spraying on it.

The test on surface appearance by SEM directly reveals the appearance of the sampling of

aluminium hydroxide/nano-attapulgite composite material. Further analysis shows that the

composition effect of preparing aluminium hydroxide/nano-attapulgite composite material varies

with the reaction conditions: pH value and the percentage of aluminium hydroxide in the total mass

of attapulgite powder (5g).

When pH is 2 or 3 and the percentage of aluminium hydroxide in the total mass of attapulgite

powder (5g) is 5% or 10%, the SEM images of the aluminium hydroxide/nano-attapulgite

composite materials sampling after hydrothermal reaction with 3g CTAB are respectively Fig.3-3,

Fig.3-4, Fig.3-5 and Fig.3-6.

Through analysis of the composition of aluminium hydroxide on the surface of attapulgite by SEM,

the optimum condition for hydrothermal reaction is decided by the requirements for the refining and

uniformity of the straw based panel.

Fig.3-3 The SEM image of the sampling after ultrasonic hydrothermal reaction (pH 2, 5%

aluminium hydroxide)

Advanced Materials Research Vol. 298 235

Page 11: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

Fig.3-4 The SEM image of the sampling after ultrasonic hydrothermal reaction (pH 2, 10%

aluminium hydroxide)

Fig.3-5 The SEM image of the sampling after ultrasonic hydrothermal reaction (pH 3, 5%

aluminium hydroxide)

Fig.3-5 The SEM image of the sampling after ultrasonic hydrothermal reaction (pH 3, 10%

aluminium hydroxide)

In the above images, the composite flame retarder is of a diameter of 20-30nm and a length of

1-2µm, with a bar-shaped one-dimensional nano structure that can effectively improve the flame

retardancy and mechanical property of the straw based panel.

In Fig.3-3 and Fig.3-5, when there is 5% aluminium hydroxide, most of the attapulgite fail to

composite with flame retarder, which means that the content of aluminium hydroxide is not

sufficient to improve effectively the flame retardancy.

In Fig.3-4 and Fig.3-6, with 10% aluminium hydroxide, most of the attapulgite can composite with

the flame retarder, which demonstrates that the content of 10% aluminium hydroxide is more

favorable than 5% for the preparation of composite flame retarder.

236 Soft Magnetic Materials

Page 12: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

The comparison of Fig.3-4 and Fig.3-6 shows that the distribution of aluminium hydroxide on the

attapulgite is more uniform when pH= 2 than that when pH =3, and is, therefore, more favorable in

the effective improvement of the flame retardancy of the straw based panel.

The content of aluminium hydroxide and its uniform distribution are of vital importance to obtain a

better flame retardancy and mechanical property of the straw based panel, therefore, it is concluded

that the optimum process condition for preparation of nano composite flame retarder in this

experiment is when pH=2 and aluminium hydroxide is 10% of the gross mass.

3.3 Observation on the Surface Quality of the Straw Based Panel

Images of the straw based panel obtained are taken by a digital camera as in Fig.3-7:

Fig.3-7 Straw Based Panel

There are lots of glue spots on the surface of straw based panels in the images, which are

caused by the wetting and absorption effect which makes the small amount of straw shavings that

are mixed with PF adhesive in the addition of adhesive, unable to disperse, resulting in the high

concentration of the adhesive at certain part of the panel and its solidification into glue spots in hot

press.

Although glue lumps can be picked out and dispersed by hand, the correspondingly

non-uniform distribution of adhesive on the straw shavings is not improved. The underlying cause

is the rough method of glue blending which pours the adhesive from the beaker into the mixer by

hand. However, in the industrial production, the adhesive is usually nebulized and then sprayed

under high pressure onto the straw shavings in a more uniform way.

Advanced Materials Research Vol. 298 237

Page 13: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

Fig.3-8 Cutting and Sampling Fig.3-9 Oxygen Index Tester: JF-3

The on-spot observation on the straw based panel reveals the unevenness of its four sides with quite

a few flashes, and an inferior intensity especially on the corners and edges which can be easily

broken.

The density distribution on the two sides of the panel is not uniform, the big straw shavings on the

upper layer creating a smaller density while the small straw shavings on the lower layer creating a

greater density.

Granules of flame retarder can be found on the surface of the panel. Some of them adhere to the

straw shavings in the panel out of physical effect, while the others adhere to the surface of straw

shavings by the adhesive.

The rectangular sampling obtained after cutting involves problems such as flashes, damaged corners

and edges, etc. which are unfavorable for the test of mechanical property and flame retardancy.

In a word, the inferior technical process for preparation of straw based panel leads to various

problems such as the uneven distribution of density and flame retarder, flashes and glue spots, etc.

which requires the further test of mechanical property and flame retardancy.

3.4 Test of Flame Retardancy

The various problems of the straw based panel samplings after cutting such as not a few flashes and

burrs, and the damaged corners and edges, etc. lead to the different sizes of the samplings.

Meanwhile, the test of Oxygen Combustion Index can not carry out due to the characteristics of

straw shavings and the existence and uneven distribution of adhesive which make flaming

combustion impossible for the panel in a fairly low Oxygen concentration.

As for the samplings obtained from the Panel Ⅰ, Panel Ⅱ, Panel Ⅲ and Panel Ⅳ in this

experiment, the respective periods of time needed for them to combust 50mm steadily in the

Oxygen concentration of 36% are shown in Table.3-1:

238 Soft Magnetic Materials

Page 14: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

Table.3-1 Periods of Time needed for the steady combustion of 50mm of straw based panels with

different content of flame retarder

Panel

No.

Content of Flame

retarder

Sampling

No. Needed Time (S)

Average

(S)

Panel Ⅰ 2%

① 175

194 ② 247

③ 162

Panel Ⅱ 4%

① 210

211 ② 207

③ 217

Panel Ⅲ 6%

① 249

251 ② 256

③ 250

Panel Ⅳ 0%

① 257

256 ② 248

③ 264

The following conclusions can be drawn from the above data:

1. The combustion time needed for different samplings of the same piece of panel are of fairly large

differences, which is mainly caused by the flashes and burrs, different sizes(damaged corners and

edges), and uneven distribution of the internal density of the straw based panel, etc.

2. Comparing the combustion time needed for samplings with different contents of flame retarder

(2%, 4%, 6%), it is shown that the flame retardancy of the straw based panel is improving

continuously with the increase of flame retarder.

3. It is noteworthy that the longest combustion time is needed when there is no flame retarder in the

panel (0%). It is because that combustion becomes more difficult with a better clamping effect of

the panel, which is caused by the greater density of straw shavings in the straw based panel when

there are only straw shavings and adhesive in it, since the straw density is far lower than that of

inorganic flame retarder.

Therefore, it is concluded in this experiment that the addition of flame retarder into the straw based

panels with the nearly same density of straw shavings has effectively improved the flame retardancy

of the straw based panels.

Advanced Materials Research Vol. 298 239

Page 15: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

Table.3-2 The part in red is the Static Bending strength obtained in the test

Content of

Flame

Retarder

Serial

Number

Span Height σbb Fbb Average Static

Bending strength

mm mm mm MPa kN

1.1 200 50 10 1.79 30.03

0% 1.2 200 50 10 2.25 37.50 1.743

1.3 200 50 10 1.19 19.80

2.1 200 50 10 1.10 18.40

2% 2.2 200 50 10 1.23 20.50 1.26

2.3 200 50 10 1.45 24.10

3.1 200 50 10 1.46 24.40

4% 3.2 200 50 10 1.10 18.40 1.32

3.3 200 50 10 1.40 23.40

4.1 200 50 10 1.08 18.00

6% 4.2 200 50 10 1.15 19.20 1.09

4.3 200 50 10 1.04 17.40

Equation for calculating the Static Bending strength:

σb=3*Pmax*l/(2*b*h2)

σb : the Static Bending strength of the sample, Mpa;

Pmax : the maximum load of the breaking of sample, N;

l: the distance between two supports (200mm);

b:the breadth of the sample (50mm);

h: the height of the sample (10).

Note: there are 4groups of samples with 3 pieces in each group.

4. Conclusion

(1) The analysis of XRD shows that the content of quartz decreases in the attapulgite mixture

purified with 30% EDTA after ultrasonic dispersion and the content of attapulgite increases.

(2) The analysis of SEM test shows that the best composite effect of the aluminium

hydroxide/nano-attapulgite composite materials is obtained when pH is 2 and the content of

aluminium hydroxide is 10%.

(3) Through the test of Oxygen Combustion Index and comparison of the combustion time needed

for samples with different contents of flame retarder (2%, 4%, and 6%), it is shown that the flame

retardancy of the straw based panel is continuously improving with the addition of flame retarder.

(4) The test on the mechanical property of the composite straw based panel through universal

testing machine shows that the Static Bending strength of samples with different contents of flame

retarder varies and is reducing with the increasing content of flame retarder.

240 Soft Magnetic Materials

Page 16: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

Summary

About the author: LIU Xiaoqi, female, born in Dec.1972, Doctoral candidate and lecturer in

School of Resources Processing and Bio-engineering of Central South University(410083), major in

mineral processing and material chemistry.

Tel.0731-88658530 (Home); 15802672506; E-mailz:[email protected]

This paper is funded by the Program of Supporting Science and Technology of China’s 11th

Five-year Plan, numbered 2006BAD07A07-08 and is under the financial assistance from the

Institute of Biological and Environmental Science and Technology of Central South University of

Forestry and Technology.

References:

[1] ZHOU Jiyuan and CUI Bingfang: Studies on the Attapulgite Clay Aboard. Resources Survey &

Environment Vol. 25(2004)

[2] ZHAN Gengsheng, XIAO Shuming and ZHENG Maosong, et al.: Studies on the Development

and Protection of the Attapulgite Clay Resources in Jiangsu Province (2005)

[3] ZHAN Gengsheng, GAO Zhenru and ZHENG Maosong, et al.: The Current Development of the

Attapulgite Clay, the Reflection and the Outlook. Jiangsu Geology [1] (2003)

[4] Mineral Commodity Summaries.US Geological Survey. [7](2007)

[5] Paul Moore: Cat Litter Clays, Consolidate and Conquer. Industrial Minerals, [11] (2004)

[6] Lan Wilson: Special Clays from Attapulgite to Sepiolite. Industrial Minerals, [11] (2004)

[7] ZHAN Gengsheng, GAO Zhengru and ZHENG Maosong: The Company Profile of the

Engelhard, U.S.A. Geoinformation of Jiangsu, [1] (2001)

[8] WANG Youfu, ZHAN Gengsheng, WANGkai and ZHENG Maosong: The Investigation Report

on the Attapulgite Clay in U.S.A. by the Delegation of the People’s Government of Xuyi

County. (2009)

[9] ZHAN Gengsheng, and ZHENG Maosong: A Tentative Study on the Development and

Utilization of the Attapilgite Clay in U.S.A. Non-metallic Mines (2005)

[10] CHENjian: An Overview of the Studies on the Application of Flame Retarder. Chemical

Intermediate (Oct. 2007), p25-29

[11] ZHENG Maosong and WANG Aiqin, et al.: Studies on the Application of Attapulgitte Clay

(Chemical Industry Press, P.R.C, 2007)

[12] LIU Boyuan, HUANGrui and ZHAO Anchi: Nanometer Materials and Nanotechnology

Non-metallic Nanometer Materials, China Powder Science and Technology [7(3)] (2001)

[13] ZHANG Hongmei and SUN Lefang: Applications of Nanotechnology in Chemical Industry.

Chemical Technology Market [26(8)](2003)

[14] CAO Mingli and CAO Minghe: Non-metallic Nano-Mineral Materials. (Chemical Industry

Press, Beijing 2006)

[15] ZHANG Hongsheng and TANGlu: The Current Development of the Attapulgite in China and

Outlook on it. China Non-Metallic Mining Industry Herald [4] (2002)

[16] ZHAN Gengsheng and ZHENG Maosong: On the Development and Utilization of Attapulgite

Clay in U.S. A. Non-metallic Mines.[2] Vol. 28

[17] LV Muyuan: The Current Development of Attapulgite Clay and Its Future Development. Gansu

Technology [21] Vol. 24, 2008

[18] ZHU Haiqing and ZHOUjie: The Current Development and Application of Attapulgite Clay

and Its Future Development. Conservation and Utilization of Mineral Resources [4]

Advanced Materials Research Vol. 298 241

Page 17: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

[19] ZHAN Gengsheng, ZHENG Maosong, GAO Zhenru and ZHU Shipeng: The Current

Development and Utilization of Attapulgite Clay, the Reflection and Outlook: a Case study on

the Development of Attapulgite Clay in Xuyi County, Jiangsu Province. Jiangsu Gelogy

[27(1)], 2003, p41-47

[20] ZHAOping, YAOying, LINfeng and ZHANG Chunxia: Method for Modifying Attapulgite and

its Current Application. Chemical Production and Technology [5] Vol.13 (2006)

[21] TANGhao, AOman, SHI Enqi and SONGhui. http://www.51pla.com/ (March, 2, 2007)

[22] BAO Junjie, YU Guifen, and JIANGxin, et al.: Removal Mechanisms of Phenol from

Wastewater by Modified Attapulgite. Environmental Chemistry 25(1), 2006, p37-40

[23] SONGyong and DAI youfen: Researches and Development on the Control of Organic

Pollutants with Ultrasound Technology and Other Technologies Related. Industrial Safety and

Environmental Protection, [31(7)], 2005, p1-3

[24] WANG Youfu, ZHAN Gengsheng, WANGkai and ZHENG Maosong: The Investigation Report

on the Attapulgite Clay in U.S.A. by the Delegation of the People’s Government of Xuyi

County.2009

[25] HUANG Jianhua, WANG Xingguo and JIN Qingzhe, et al.: Adsorption of Phenol on Organic

Modified Attapulgite by Ultrasonic Method. Techniques and Equipment for Environmental

Pollution Control [6(9)], 2005, p25-28

[26] WANG Jinming and YI Facheng: Study on Characterization of Modified Attapulgite and Its

Adsorption Capacity on Simulated Nuclide Cs+. Non-metallic Mines [29(2)], 2006, p53-55

[27] ZHU Guoming and CHENG Hailong: The Present Status of Strawboard Industry in China and

and Analysis of Its Prospect. The First National Symposium on Bio-materials Science and

Techniques, Beijing, August 12-19, 2007

[28] BAIbo: On the Production Process of the Flame Retardant Furniture Facing Panel.

Doctorate Dissertations of the Northeast Forestry University, Dec.2008

[29] ZHANG Hongsheng and TANGlu: The Actualities and Prospects of Attapulgite in China.

China Non-metallic Mining Industry Herald [4]2002

[30] WANG Hongyan, ZHANGyan and ZHOU Shouyong, et al.: Characteristics and Application

Research of Sulfuric Acid Modified Attapulgite. Journal of Huaiyin Teachers College (Natural

Science Edition), [4] 2005, p47-50

[31] ZHANG Tiejiang: The Flame-retardant Mechanism of Common Flame Retarders. Chemical

Engineering and Equipment, 2009, p114-115

[32] WANG Xiaoying, BI Chengliang, LI Lili and ZHANG Baogui: The Research Development of

the New Environment-friendly Flame Retarder. Tianjin Chemical Industry [1] Vol. 23

[33] QI Zhenyu: A Tentative Study on the Formulation of Quick and Simple Testing Methods for the

Combustion Property of the Flame Retardant Wood Based Panel, the First National Forum on

Production and Application of Environmental Flame Retardant Wood Based Panel

[34] XU Zhiyun: Study on the Preparation Techniques on Nano Materials. Journal of Wuhan

Institute of Science and Technology [8] Vol.20, p44-47

[35] HUANGhui: Hydrothermal Preparation of TiO2 Film and Its Photocatalytic Degradation

Performance. Master Thesis of Northwest Institute of Light Industry, 1999

[36] RANG Xianqiang: Research Development on Hydrothermal. Silicon Valley (Nature and

Science edition)

[37] LI Shutang: Foundations for X-ray Diffraction of Crystals (Metallurgical Industry Press,

Beijing 1990)

[38] CHEN Shipu: Electronic Micro-Analysis of Metal (Mechanical Industry Press, Beijing 1982)

242 Soft Magnetic Materials

Page 18: Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials

Soft Magnetic Materials 10.4028/www.scientific.net/AMR.298 Application of Attapulgite Clay Mineral Modified by Flame Retarder in Green Building Materials 10.4028/www.scientific.net/AMR.298.226