Curing agents have different temperatures at which they work, and the heat resistance of the final cured material varies significantly. Generally, a curing agent with a higher curing temperature tends to produce a product with better heat resistance. For addition polymerization type curing agents, the order of increasing curing temperature and heat resistance is as follows: aliphatic polyamines, then alicyclic polyamines, followed by aromatic polyamines, and finally phenolic anhydrides.
The heat resistance of catalytic addition-type curing agents usually matches that of aromatic polyamines. Meanwhile, anionic and cationic polymerization types—such as tertiary amines, imidazolium antimony, and BF3 complexes—show similar heat resistance levels. This is because, although their initial reaction mechanisms differ, they eventually form a similar ether-bonded network structure.
The curing process is a chemical reaction highly dependent on temperature. As temperature increases, the reaction rate accelerates, leading to shorter gel times. Typically, the logarithm of the gel time decreases linearly with rising curing temperature. However, excessively high temperatures can degrade the properties of the final product, so there's a practical upper limit to the curing temperature. A balance must be struck between curing speed and the quality of the cured material when selecting the optimal temperature. Based on this, curing agents are generally classified into four categories: low-temperature (below room temperature), room-temperature (between 20°C and 50°C), medium-temperature (50°C to 100°C), and high-temperature (above 100°C).
Low-temperature curing agents are relatively rare, but examples include polyalkylene glycols and polyisocyanates. Recently, modified amines like T-31 and YH-82 developed in China can cure at temperatures as low as 0°C or below. Room-temperature curing agents are more common and include aliphatic polyamines, alicyclic polyamines, low-molecular-weight polyamides, and modified aromatic amines. Medium-temperature curing agents often consist of certain alicyclic polyamines, tertiary amines, carbazoles, and boron trifluoride complexes. High-temperature curing agents include aromatic polyamines, acid anhydrides, resole phenol resins, amino resins, dicyandiamide, and hydrazides.
In high-temperature curing systems, the process is typically divided into two stages. First, the material is pre-cured at a lower temperature before it gels. Once it reaches the gel stage or slightly beyond, it undergoes post-curing at a higher temperature to fully develop its properties. This two-step approach ensures both efficient curing and optimal performance of the final product.
Thin-Walled Polypropylene PCR strip tubes
As one of the largest manufacturers of PCR strip tubes in China for over a decade, we have been supplying PCR 8 strip tubes and PCR single tube to our international customers.
As these PCR tube strips have thin and uniform walls, they can fit in different types of thermal cyclers. As a next step, we are also planning to develop PCR tube strips with attached caps, also called PCR strip tubes with individually attached caps.
More info about PCR strip tubes:
What Are PCR strip tubes?
PCR strips tubes allow scientists working with cyclers and enzymes to gain enhanced PCR yield through a faster transmission of heat from block to the reaction. It offers better control over the reaction while speeding up the process with high heating and cooling rates.
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