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