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ABSTRACT:
The objective of the project is to synthesize a cheap non-toxic and efficient flame retardant from disposable diapers, since diapers are intended for Children, the presence of harmful chemicals is quite negligible. The process involves the synthesis of flame retardant using sodium polyacrylate as raw material and magnesium hydroxide is added as an additive. The characterization of the flame retardant will be determined using ignition test and small flame test. The flame retardant, thus, produced can be utilized for many applications such as steam pipe insulation and also it can be used to clean up massive oil spills.
Keywords: Sodium Polyacrylate; magnesium hydroxide; IgnitionTest; small flame test; non-toxic;
oil spilling ; Steam Pipe Insulation
INTRODUCTION
Flame retardants are added to different materials or applied as a treatment to materials (e.g., textiles, plastics) to prevent fires from starting, limit the spread of fire and minimize fire damage. Some flame retardants work effectively on their own; others act as “synergists” to increase the fire protective benefits of other flame retardants. A variety of flame retardants is necessary because materials that need to be made fire-resistant are very different in their physical nature and chemical composition, so they behave differently during combustion. The elements in flame retardants also react differently with fire. As a result, flame retardants have to be matched appropriately to each type of material. Flame retardants work to stop or delay fire, but, depending on their chemical makeup.
While a large number of flame retardants are considered safe to use there has been growing concern regarding the use of particular flame retardant chemicals. For example; Polybrominated diphenyl ether (PBDE) is a common flame retardant used to reduce the risk of fire in a wide variety of products, such as children's pajamas and computer’s. PBDEs are excellent flame retardants, but the chemicals have been accumulating in the environment and in human bodies. Relatively recent reports have indicated that exposure to low concentrations of these chemicals may result in irreparable damage to the nervous and reproductive systems[1].
Fire retardants such as PBDEs (polybrominated diphenyl ethers) are chemicals added to furniture, electronics, foam insulation, and building materials so they will not easily burn. PBDEs are not chemically bound to the flame-retarded material, so they enter the environment from volatilization, leaching, or degradation of PBDE-containing products. They accumulate in house dust, exposing children, adults, and pets through inhalation or ingestion. PBDEs, found in blood and breast milk, are now found in almost all people studied. People are exposed to low levels of PBDEs through ingestion of food and by inhalation. PBDEs bioaccumulate in blood, breast milk, and fat tissues. Increasing PBDE levels have been detected in the blood of marine mammals such as harbor seals[2].
Water is currently the most frequently used fire-fighting medium. The extinguishing properties of water are based mainly on its effect in cooling the combustible material to a temperature below the ignition point of the material, by absorbing heat through conversion of water to water vapor. Use of water as an extinguishing agent has a number of disadvantages. For example, during the extinguishing process, large quantities evaporate or flow away unused and may cause
unnecessary water damage.
This project involves the preparation of non-toxic flame retardant material using diapers. Commercial superabsorbent materials are widely used in a variety of personal care products, such as infant diapers. Sodium polyacrylate (Fig.1.1) is the absorbing agent found in disposable diapers. It absorbs water by a process called osmosis. When the (sodium-containing) polymer is placed in contact with water, there is a tendency for the sodium to distribute equally between the network and the water. That means, some of the sodium atoms want to leave the network and move to the water. When these sodium atoms leave, they are replaced with water molecules. Water swells the polymer network to try to keep the sodium concentration balanced between the polymer and the water. The cross-links that connect the chains together prevent them from dissolving/breaking apart in the water. Sodium polyacrylate can absorb 800 times its weight in water.
sodium polyacrylate is chosen among the various chemicals because of its non-toxic nature.
According to the report given by HMS medicals, sodium polyacrylate is considered as a
non-toxic chemical. Magnesium hydroxide is chosen as an additive for its flame retardant nature. Suspensions of magnesium hydroxide in water are used as an antacid to neutralize stomach acid, and as a laxative. Magnesium hydroxide is also used as an antiperspirant underarm deodorant. magnesium hydroxide is useful against canker sores (aphthous ulcer) when used topically.Magnesium hydroxide is sold for medical use as chewable tablets, capsules, and as liquids having various added flavors. It is primarily used to alleviate constipation, but also to relieve indigestion and heartburn. Industrially Magnesium hydroxide powder is used as a non-hazardous alkali to neutralize acidic wastewaters. The method involves the separation of super absorbent material present in the diaper core , certain amount of water is added in order to obtain swelling nature.
LITERATURE REVIEW :
Song Hou studied the formation of formation of toxic species from 4-chlorobiphenyl in fires, Polychlorobiphenyls (PCB) are persistent organic pollutants, first identified as environmental contaminants in 1966.Prior to their phase-out in late 1970s, they were widely used as coolants and insulating fluids in transformers and capacitors[3]. They were first introduced in these applications in 1930s. PCB are toxic and accumulate in the environment. Inspite of PCB production concluding in the late 1970s, these compounds persist in every part of the world, in water, soil, as well as bird and fish tissue. The hazards of accidental chemical fires, which may occur in production and storage facilities, necessitate a better understanding of the formation of toxic species in combustion of MCB.
Natalia Quinete evaluated the PBDEs and PCBs levels in selected fish species and dolphins from Paraiba do Sul River, Brazil. BDE 47 and 85 were the predominant congeners. Low chlorinated congeners showed the highest concentrations in fish; however dolphins presented the highest proportion of PCBs 153, followed by 138 and 180. The daily intake of PBDEs and PCBs was estimated for the population of this region. PCB daily intake through consumption of croaker was above the limits set by the Brazilian Ministry of Agriculture, raising great concern over the existence of a source of PCB contamination in Brazil[4].
Shen Hao analyzed the various halogen free flame retardants , Two different types of magnesium hydroxide namely, platy magnesium hydroxide (MH) and magnesium hydroxide sulfate hydrate (HMOS) whiskers were used to fill with Polypropylene (PP) in his study. Addition of MH and HMOS enhanced flame retardancy of PP, but the filler content needed to reach 40wt% loading. Either MH or HMOS reduced the mechanical properties of PP, due to the poor adhesion between PP matrix and filler in SEM observation[5]. However,PP/HMOS composites showed higher tensile strength than PP/MH composites.
Haifen pan done an extensive research on improving the flame retardancy of cotton fabrics. He developed a renewable and environmentally benign technique to improve the flame retardancy of cotton fabrics by the layer-by –layer deposition of semi-biobased substances on the surface of the cotton fabrics. The used semi-biobased substances included negatively charged ingredients. Some typical combustion tests, including vertical flame tests and microscale combustion calorimeter were mainly used to measure the fire safety of coated cotton fabrics[6].
Tang Hao investigated the effect of addition of magnesium hydroxide to improve flame retardant nature . As a kind of polymeric materials, unsaturated polyester resin is widely used in aerospace, building and paint industries. Unsaturated polyester resin is combustible material, and could produce a lot of heat, smoke and toxic gas during its combustion process, so it becomes a potential fire risk. Flame retardant performance is an important index to evaluate the performance and application of the polymerization unsaturated polyester resin[7]. Halogen- (especially bromine-) and phosphorus- flame retardant agents can be used as flame retardants for unsaturated polyester resin, but considering of their costly and environmental safety problems, their application scope is limited. Magnesium hydroxide is an environmental friendly inorganic flame retardant with multiple flame retardant, low smoke non-toxic characteristics.
According to the report given by HMS medicals sodium polyacrylate is identified as non-toxic chemical and also biodegradable
Chronic Toxicity
Chronic inhalation exposure to rates for a lifetime (two years) using sodium polyacrylate that had been micronized to a respirable particle size (less than 10 microns), In the absence of chronic inflammation, tumors are not expected. There were no adverse effects detected at 0.05 mg/m³.
Mutagenicity
Sodium polyacrylate had no effect in mutagenicity tests.
Ecotoxicity
polyacrylate absorbents are non-toxic to aquatic or terrestrial organisms at predicted exposure levels. Environmental Fate Polyacrylate absorbents are relatively inert in aerobic and anaerobic conditions. They are immobile in landfills and soil systems (> 90% retention), with the mobile fraction showing biodegradability. They are also compatible with incineration of municipal solid waste. Incidental down-the-drain disposal of small quantities of polyacrylic absorbents will no affect the performance of wastewater treatment systems.
3. MATERIALS AND METHODS:
Chemicals required : sodium polyacrylate(absorbent pad in diapers) , additives
Absorbent pad removal
The single most important property of a diaper, cloth or disposable, is its ability to absorb and retain moisture. Cotton material used in cloth diapers is reasonably absorbent, but synthetic polymers far exceed the capacity of natural fibers. Today's state-of-the-art disposable diaper will absorb 15 times its weight in water. This phenomenal absorption capacity is due to the absorbent pad found in the core of the diaper. This pad is composed of two essential elements, a hydrophilic, or water-loving, polymer and a fibrous material such as wood pulp. The polymer is made of fine particles of an acrylic acid derivative, such as sodium acrylate, potassiumacrylate, or an alkyl acrylate. These polymeric particles act as tiny sponges that retain many times their weight in water. Microscopically these polymer molecules resemble long chains or ropes. Portions of these chemical "ropes" are designed to interact with water molecules. Other parts of the polymer have the ability to chemically link with different polymer molecules in a process known as cross linking. When a large number of these polymeric chains are cross linked, they form a gel network that is not water soluble but that can absorb vast amounts of water. Polymers with this ability are referred to as hydrogels, superabsorbents, or hydrocolloids. Depending on the degree of cross linking, the strength of the gel network can be varied. This is an important property because gel strength is related to the tendency of the polymer to deform or flow under stress. If the strength is too high the polymer will not retain enough water. Either use scissors or tear the elastic border off both sides of diaper. Place the absorbent core in a gallon size zip-closing plastic bag.
ADDITIVES:
The following components can be chosen as additives
CHEMICAL FUNCTION
Aluminum Trihydrate Fire retardant, astringent
Acediasulfone Antibacterial
Agaricic acid Antiperspirant
Alclometastone Topical anti-inflammatory
Calcium alginate Topical hemostatic
Amidomycin Fungicide
Antimony oxide Fire retardant
Apigenin Yellow dye, mordant
Arsenic disulfide Red Pigment
Azanidazole Antiprotozoal (Trichomonas)
Azelaic acid Antiacne
Baicalein Astringent
Bendazac Anti-inflammatory
Benomyl Fungicide; ascaricide
Benzestrol Estrogen
Benzylpenicillinic acid Antibacterial
Benzylsulfamide Antibacterial
Bergaptene Antipsoriatic
Betasine Iodine source
Bezitramide Narcotic analgesic
Bibrocathol Topical antiseptic
Bietanautine Antihistaminic
Bifenox Herbicide
Bifonazole Antifungal
Binapacryl Fungicide, miticide
Bis (p-chlorophenoxy) Miticide
Bismuth aluminate Antacid
Bismuth iodide oxide Anti-infective
Bismuth phosphate Antacid; protectant
Bismuth subcarbonate Topical protectant
Bismuth subgallate Astringent, antacid;
Bisphenol Fungicide
Bitertanol Agricultural fungicide
Bithionol Topical anti-infective
Bromacil Herbicide
Magnesium hydroxide Flame retardant
In this experiment magnesium hydroxide is chosen as an additive because of its non-toxic nature. 20 grams of magnesium hydroxide is added for every 100ml of water and a hydrogel is formed. This hydrogel is completely non-toxic and eco friendly . The material must be stored in in a cool, dry place making provisions for an airtight seal.
TESTING METHODS :
NFPA FIRE TEST (to check the deformation tendency):
Suspend each sample vertically , the short edge at the bottom . Metal thongs or pliers work well to keep fingers out of the test . using a standard, wooden kitchen match and apply the tip of the flame to the center of the bottom edge of the suspended sample , hold the flame steadily after 12 seconds , remove the match and do not blow it out in the direction of the sample. Continue to observe the specimen . Any flame on the specimen must self extinguish within 2 seconds after you remove the match, any glowing along the burnt edge of the or any generation of smoke must stop completely within 20 seconds after the removal of the match if either of these limits is exceeded , your material is not sufficiently flame resistant and it has low deformation level
ignition behavior test :
During testing the sample the burning behaviour and time of burning were investigated .A burner with a flame is exposed to the free end of the sample for 15s and then removed and the flammability properties of the sample is studied[9] .Finally burning rate is calculated using the formula
Burning rate = (60*Burning length )/burning time mm/min
small flame test :
The test must be conducted on six samples. Propane/ butane burner must be used and the burner must be angled at 45o through out the experiment the total test time was 20 sec divided in to 15 sec to expose the sample to the flame then removed and 5 sec to study the effect of burning on the sample
RESULTS AND DISCUSSIONS
NFPA –fire test :
No considerable deformation is observed when the sample is subjected to NFPA fire test , after 25 seconds there are no actual traces of fire/ flame. Formation of smoke is also not observed.
Ignition behavior test :
six samples are subjected to ignition behavior test and some of the details such as Burning length ,Burning rate and Burning time are noted. Dripping , shrinking , small area burning and Fast burning are also noted.
CONCLUSION
Due to exceeding levels of the toxic flame retardants , there has been a lot of damage to human health and environment . This flame retardant is non-toxic and biodegradable material. This material can also be used as steam pipe insulation (low temperature), the material can also be used to clean the massive oil spillages[10].