Is the adhesive toxic?
Adhesives are generally made of resins, monomers, curing agents and other main materials and diluents, initiators, solvents, antioxidants, accelerators, coupling agents, colorants, fillers and other auxiliary materials and additives, which are used to dissolve, dilute and surface treatment of organic solvents are mostly toxic and volatile organic substances. At the same time, the adhesive in the curing of some will release toxic low molecular substances. In addition, some solid fillers are also toxic. Thus, it can be seen that the general adhesives have more or less will have a certain degree of harm to the human body and the environment. There are many types of adhesives, and different varieties of adhesives have different degrees of toxicity due to the different components they contain.
Epoxy resin adhesive
Main material
Commonly used epoxy resin for E-type epoxy resin, LD50 is 11400mg/kg, basically non-toxic, but the raw material Bisphenol A is suspected to be an environmental hormone substances, if the main material in the free Bisphenol A content is too high will have a certain impact on the environment. The toxicity of alicyclic epoxy resin is also larger, for example, the LD50 of YJ-132(6206) epoxy resin is 2830mg/kg.
In addition, the epoxy resin will escape a trace amount of epichlorohydrin when heated, which will irritate the respiratory tract, skin and eyes, and its LD50 is 1140mg/kg, which is a moderately toxic substance.
Curing agents
Especially amine curing agent is the main source of toxicity of uncured epoxy resin adhesive, had been used for many years of ethylenediamine curing agent volatility, high vapor pressure, the oral cavity, respiratory mucous membranes and lungs have a serious irritation, skin contact will cause allergies, itching, edema, and even produce erythema, ulceration, will be the original amine curing agent modification is to reduce the toxicity or implementation of the non-toxic important way. The LD50 indexes of commonly used amine curing agents are shown in the following table:
Curing agent
It can be seen from the table that the toxicity of m-phenylenediamine is also very big, mainly causing dermatitis and asthma, and it can not be used in contact with the skin. At present, isophthalic acid is used instead of m-phenylenediamine, the performance is similar, but the toxicity is greatly reduced, and its LD50 is 625-1750mg/kg.
Diaminodiphenylmethane is also one of the more toxic curing agents, but has not been found to be carcinogenic; phthalic anhydride is an anhydride curing agent for epoxy resins with an LD50 of 800-1600mg/kg, and its dust and vapor are irritating to the eyes, skin, and respiratory tract, resulting in ocular conjunctivitis, hoarseness, coughing, asthma, and other symptoms.
Diluent
From the table it can be seen that m-phenylenediamine is also very toxic, mainly causing dermatitis and asthma, and should not be used in contact with the skin. At present, isophthalic acid is used instead of m-phenylenediamine, the performance is similar, but the toxicity is greatly reduced, and its LD50 is 625-1750mg/kg.
Diaminodiphenylmethane is also one of the more toxic curing agents, but has not been found to be carcinogenic; phthalic anhydride is an anhydride curing agent for epoxy resins with an LD50 of 800-1600mg/kg, and its dust and vapor are irritating to the eyes, skin, and respiratory tract, resulting in ocular conjunctivitis, hoarseness, coughing, asthma and other symptoms.
Filler
Certain fillers in epoxy resin adhesives are also toxic, silica micropowder is inhaled and accumulated to produce silicosis; fine fibers of amphibole powder with burrs cause respiratory diseases and are designated as carcinogenic; chromates are harmful to lungs and other organs; nano-fillers cause more serious and bizarre damage to the lungs than ordinary harmful dusts.
Phenolic Resin Adhesives
Phenol
Phenol is a white crystal with a melting point of 40-41°C. Its vapor has an aromatic odor and can be decomposed in nature. When the phenol load exceeds the self-purifying ability of nature, it will not only pollute the environment and jeopardize the growth and reproduction of various organisms, but also endanger human health. When the human body is exposed to phenol, it will have a strong corrosive effect on the skin and mucous membranes, and can also inhibit the central nervous system or damage the liver and kidney functions. Aqueous solutions are more readily absorbed through the skin than pure phenol, while emulsions are more readily absorbed. Phenol mostly invades the body in the form of vapor or liquid through the respiratory tract, skin and mucous membranes. When the concentration is low, it can denature proteins, and when the concentration is high, it can precipitate proteins, so it is directly harmful to all kinds of cells, and the lethal dose of human oral intake is 2-15 g. Phenol has strong corrosive effect on skin and mucous membranes, and skin burns are the most common, such as burning caused by hot phenol liquid splashed on the skin and absorbing the toxicity. If splashed into the eyes, immediately cause conjunctival and corneal burns, necrosis. Phenol LD50 is 530mg/kg, long-term inhalation of low concentrations of phenol will be vomiting, dysphagia, increased saliva, diarrhea, tinnitus, delirium and other symptoms.
Formaldehyde
Formaldehyde is a gas with a strong irritating odor, which is very harmful to the respiratory tract, mucous membranes and skin, and can cause chronic respiratory diseases, nasopharyngeal cancer, colon cancer, brain tumors, menstrual disorders, gene mutations in the cell nucleus, cross-linking within the single-stranded DNA and DNA-protein cross-linking and inhibition of the repair of DNA damage, pregnancy syndromes, chromosomal abnormalities in newborns, leukemia, and causes memory and intellectual decline in adolescents.
Polyurethane Adhesives
The toxicity of polyurethane adhesives mainly comes from the monomer isocyanate when synthesizing polyurethane. The vapor of isocyanate is a serious irritant to the respiratory tract, skin, and eyes, and is also a lachrymator. Inhalation of isocyanate vapors by humans will result in dryness of the throat, itching, coughing, bronchitis, asthma, and difficulty in breathing. At the same time, the more commonly used toluene diisocyanate splashed in the eyes or fall on the skin not only irritation, but also burns.
Neoprene Adhesive
Benzene
Benzene is a very toxic colorless transparent volatile liquid, carcinogenic substances, long-term exposure may cause leukemia and bladder cancer and other diseases. Inhalation of too much steam will appear in the vegetative nervous system dysfunction, excessive sweating, rapid or slow heartbeat, blood pressure fluctuations, resulting in acute poisoning, severe fainting, cell maturation disorders, aplastic anemia. Chronic benzene poisoning can cause neurasthenia, damage to the hematopoietic system, anemia, a sustained decline in white blood cell count, thrombocytopenia and a tendency to bleed. If the skin is exposed to benzene for a long period of time, the skin is dry, red, sores and eczema appear.
Toluene and Xylene
Toluene is a volatile liquid with irritating odor, second to benzene in toxicity, irritating to the skin and mucous membranes, stronger than benzene in neurological effects, and has the potential to cause bladder cancer in long-term exposure. However, toluene can be oxidized into benzoic acid, and glycine generated by the discharge of uric acid, will not produce accumulation of poisoning, so there is no toxicity to the blood. Short-term inhalation of higher concentrations of toluene can appear in the eyes and upper respiratory tract irritation symptoms, conjunctiva and eye congestion, dizziness, headache, limb weakness and other symptoms. GB18583 – 2001 and GB19340 – 2003 mandatory The national standards all limit the amount of toluene in solvent-based adhesives.
Xylene has an irritating effect on the eyes and mucous membranes of the upper respiratory tract, and has an anesthetic effect on the central nervous system at high concentrations. Short-term inhalation of higher concentrations of xylene can appear in the eyes and upper respiratory tract obvious irritation symptoms, conjunctiva and pharynx congestion, dizziness, headache, nausea, vomiting, chest tightness, limb weakness, blurred consciousness, staggering gait. Industrial xylene often contains benzene and other impurities.
Antioxidant D
Also known as antioxidant D, the scientific name is N-phenyl-β-naphthylamine, has a large toxicity, not only on the eyes, skin, mucous membranes and upper respiratory tract irritation, sensitization of the skin, but also contains carcinogenic substances, endangering health.
Fast-setting acrylic adhesive
Fast-fixing acrylic adhesives, the main monomer is methyl methacrylate, colorless and transparent, its toxicity is not great, but has an unpleasant odor, making people nausea, headache. There is a certain degree of irritation to the eyes, and local coating on the skin can only cause a slight sting. If the amount of inhaled vapors, serious symptoms of neurasthenia, dyspnea, some effects on the liver, but there is no significant accumulation of toxic phenomena.
Unsaturated polyester adhesive
The main toxic substance in unsaturated polyester resin adhesive is the cross-linking agent styrene, which has an unpleasant odor and has been designated as a carcinogen. Prolonged exposure can cause headaches and skin irritation. The vapors have an irritating effect on the eyes, nose and respiratory tract. Meanwhile, the accelerants N,N-dimethylaniline and N,N-diethylaniline, in addition to being carcinogenic themselves, emit aniline gas when heated. Studies have shown that bladder cancer is 30 times more common in people exposed to aniline than in the general population.
Solvent-based adhesives
Trichloromethane
Trichloromethane, also known as chloroform, chloroform, triclosan, is a colorless and transparent volatile liquid with a boiling point of 61.2℃. The vapor has irritating effect on eyes, nose and throat, anesthesia and irritation on central nervous system, and can damage heart, liver and kidney, and is suspected to be carcinogenic. Oral intoxication amount is 280g, in the concentration of 120g/m3 continuous inhalation 5 ~ 10min can die. Under the action of light and heat, it can be oxidized by oxygen in the air to generate hydrogen chloride and highly toxic phosgene (carbonyl chloride), and the phosgene generated can be eliminated by adding 1%~2% ethanol.
Carbon tetrachloride
Colorless transparent volatile liquid, boiling point 76.8℃, with a slightly sweet odor similar to chloroform. Toxicity is very large, serious damage to the liver and kidney, recognized liver poison, acute carbon tetrachloride poisoning due to inhalation of its high concentration of vapors in the production of labor, with central anesthesia symptoms and liver and kidney damage as the main feature. Inhalation of a high concentration of vapor can quickly appear coma, convulsions, serious cases can die suddenly. People inhaling 0.21-0.78g/m3 vapor will feel extremely tired, pale and confused, and even lead to death. Ethanol has a toxicity-enhancing effect and can promote the absorption of carbon tetrachloride in the body.
Methanol
Methanol is a volatile, colorless and transparent liquid with a boiling point of 64.6℃. The toxic effect of methanol on human body is caused by methanol and its metabolite formaldehyde and formic acid, mainly characterized by central nervous system damage, eye damage and metabolic acidosis. Methanol itself has an anesthetic effect and has a direct toxic effect on nerve cells. Inhalation of vapors will feel a headache, causing vomiting, blurred vision, a normal person once drinking 10mL. pure methanol or 2 days of oral oral divided cumulative up to 124 ~ 164mL can lead to blindness; an oral dose of more than 30mL will die.
Cyclohexanone
Cyclohexanone is a colorless oily liquid with a boiling point of 155.7°C. It has an unpleasant odor, makes people nauseous, has anesthetic effect, and has certain damage to the liver and kidneys, with an LD50 of 2060mg/kg. Cyclohexanone is a low-toxicity chemical substance, which can be discharged from the urine after inhalation, and will not accumulate in the body. However, when the concentration in the air reaches 40mg/m3, it has irritating effect on human eyes, nose and throat.
Trichloroethylene
Trichloroethylene is a colorless transparent liquid with a boiling point of 86.7°C. It is toxic and is a central nervous system accumulative anesthetic, and reacts with oxygen to produce highly toxic phosgene when heated or at high temperatures, and damages the liver, kidney and heart. Acute poisoning appears drunkenness, headache, dizziness, agitation and other manifestations. In severe cases, toxic encephalopathy and damage to the liver, kidneys and heart occur, and neurodepression and paranoia-like psychosis can occur during the recovery period.The HSE has categorized trichloroethylene as a class II carcinogen, and although it has not been banned, it should always be used with caution.
