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The role of curing agents

Release time:

2023-05-31

The physical and chemical properties of the curing agent have a significant impact on toxicity. For example, whether a curing agent is liquid or solid, its toxic effects vary. Solid state can easily adhere to the skin, while liquid state has vapor pressure. Generally speaking, if the chemical activity of the curing agent is high, its biomass activity is also strong, which is prone to toxicity, and it seems to be a rule. The toxicity of curing agents is manifested in the following aspects.

1. Acute toxicity: Generally expressed as LD50. Amine curing agents have strong toxicity. The LD50 value for most organic polyamines to cause respiratory irritation and death in mice is approximately 1000 to 12000 vapor concentrations μ G/g, exposure time 4-6 hours. Primary and secondary amines are more irritating than tertiary amines, while aromatic amines are more toxic than fatty amines. The toxicity of m-phenylenediamine is 10 times stronger than that of diethylenetriamine. Pyridine and piperazine can cause liver and kidney damage and have significant systemic toxicity.

2. Irritating effects on the skin and mucous membranes: The toxicity of curing agents is more importantly reflected in their irritation to the skin and mucous membranes. Because amines are organic bases that are soluble in water and fat, they can also dissolve and soak in skin fat. Long term stimulation can easily lead to punctate erythema, formation of blisters, cracking, and even flaky peeling, leading to tissue necrosis.

3. Allergic effects of curing agents. Allergy refers to the formation of an allergen after a compound acts on the skin of the human body. In the next or subsequent repeated contact, skin diseases may also occur regardless of the degree of contact. After this situation occurs, work in contact with the allergic compound should be interrupted. The occurrence of allergic effects is relatively complex, and the pudding test is used to study animals.

4. Other toxic effects of curing agents. In addition to the damage caused to the internal organs by aromatic amines and heterocyclic amine curing agents, biphenyl aromatic amines are carcinogenic and have been banned from production and use. M-phenylenediamine and diaminodiphenylsulfone have been confirmed by many toxicologists to be non carcinogenic, and previous views have been refuted.

Information

2019-05-05

What are polymer materials included?

It mainly includes three categories: plastic, chemical fibers, and rubber. There are many types of synthetic materials among them, which are made from monomers produced by petrochemical industry through polymerization reactions. Some have special properties that natural materials cannot achieve and are widely used in industrial and agricultural production and daily life, so they have developed rapidly. In the 1930s, the world's production of polymer materials did not exceed 100kt, but by the 1980s it had reached about 80Mt, with plastics accounting for 3/4. Due to the fact that plastic is lighter than metal, its production by volume has already surpassed that of metal materials.

It mainly includes three categories: plastic, chemical fibers, and rubber. There are many types of synthetic materials among them, which are made from monomers produced by petrochemical industry through polymerization reactions. Some have special properties that natural materials cannot achieve and are widely used in industrial and agricultural production and daily life, so they have developed rapidly. In the 1930s, the world's production of polymer materials did not exceed 100kt, but by the 1980s it had reached about 80Mt, with plastics accounting for 3/4. Due to the fact that plastic is lighter than metal, its production by volume has already surpassed that of metal materials.


Curing agents can be divided into room temperature curing agents and heating curing agents according to their use. Epoxy resin generally has excellent performance during high-temperature curing, but coatings and adhesives used in civil construction require room temperature curing due to heating difficulties; So most of them use fatty amines, alicyclic enantiomers, and polyamides, especially in winter when coatings and adhesives have to be used in combination with polyisocyanates, or when using odorous polyols.


Fine chemical industry is a general term for the production of fine chemicals, abbreviated as "fine chemical industry". The meaning of fine chemicals is still under discussion abroad. Chemical products with the following characteristics are commonly referred to as fine chemicals, namely:


(1) Consider the variety and performance of curing agents. The variety of curing agents has a significant impact on the mechanical properties, heat resistance, water resistance, corrosion resistance, etc. of the cured product. For example, curing agents such as aromatic polyamines, imidazole, and anhydride have a higher heat resistance than curing agents such as aliphatic polyamines and low molecular weight polyamides in curing epoxy resins; The water resistance of aromatic anhydride cured epoxy resin is better than that of aromatic diamine and aliphatic polyamine curing agents; Triethylenetetramine curing agent has good alkali resistance, but poor acid resistance and formaldehyde solution resistance. The resistance of epoxy resin cured with alicyclic polyamines (such as isophorone diamine) is excellent. The alkali resistance of epoxy resin cured with anhydride curing agent is superior to acid resistance. Appropriate curing agents should be selected based on different applications and performance requirements.


The curing temperature of the curing agent is closely related to the heat resistance of the cured product. Similarly, in the same type of curing agent, although it has the same functional group, its properties and cured product characteristics also differ due to different chemical structures. Therefore, a comprehensive understanding of the properties and characteristics of polyamine curing agents with the same functional group but different chemical structures is crucial for selecting curing agents.


Plasticizers are usually structurally polar or partially polar, and are liquids or low melting point solids with high boiling points, high volatility, and good miscibility with polymers. Plasticizers are distributed between macromolecular chains, which can reduce intermolecular forces, reduce polymer viscosity, and enhance flexibility. Plasticizers are divided into two categories: main plasticizer and secondary plasticizer. The main plasticizer has a good compatibility with resins, with low permeability and volatility, which can improve plasticization efficiency.


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