Study On Yellowing Mechanism And Yellowing Resistance Of Semi-Aromatic Nylon 12T

As a new type of long carbon chain heat-resistant polyamide,semi-aromatic nylon 12T is formed by high-temperature high-compression polymerization of long-chain 12-carbon diamine and aromatic dibasic-terephthalic acid.Due to its excellent dimensional accuracy,heat resistance and chemical resistance,it can be used as an ideal engineering plastic for a wide range of heat-resistant parts in the automotive,mechanical and electrical industries.At the same time,nylon 12T is also an ideal choice for parts that must maintain structural integrity under special conditions such as short-term high temperatures.However,aging is a common problem of polymer materials,and it is an irreversible chemical reaction.From the beginning of synthesis,to the molding and processing of products,and finally to use in certain environments,aging is carried out all the time,and aging will destroy polymers.The molecular structure of the material causes various properties to deteriorate.Especially for some light-colored products,the color becomes yellower and more deadly during the aging process.Yellowing is a macroscopic manifestation of aging of polymer materials,and it is an important signal for changes in the internal structure of polymers and changes in their properties.Therefore,it is extremely important to study the yellowing mechanism of high temperature nylon 12T in the aging process and take timely and effective yellowing resistance to prolong the service life.This topic firstly explored the color change of pure sample high temperature nylon 12T during heat aging and thermal aging.The infrared spectrum of nylon 12T before and after aging was tested.The results showed that nylon 12T was in the hot oxygen aging chamber.The extension of the medium time,the carbonyl stretching vibration peak near the wave number of 1715 cm-1 is getting stronger and stronger,the carbonyl index increases with the prolongation of the thermal oxygen aging time,and the yellow index and chromatic aberration also increase with the aging time.Finally,it tends to be flat.While the thermal aging of nylon 12T under vacuum at 260 ℃ is almost constant with time,the yellow index of heat aging for 5 days only reaches 10,which is equivalent to 1 hour of thermal oxygen aging at 170 ℃,indicating that oxygen is discoloring nylon 12T.The main factor is that with the formation of the imide and the conjugated structure on the nylon 12T main chain,the energy required for the electron transition is reduced,and the absorption wavelength shifts to the blue-violet light in the visible region.The macroscopic color is the yellowing of the nylon material.In order to improve the yellowing resistance of nylon 12T,expand its application in LED lamps and other aspects.In this paper,different methods were used to explore the effect of its yellowing resistance.The first is to select a suitable anti-aging system for antioxidants.The effects of different antioxidants and dosages on the yellowing resistance of nylon 12T were studied.The experimental results show that the composite system with primary antioxidant 1098 and auxiliary antioxidant s9228 can be significantly improved.The yellowing resistance of nylon 12T showed a good synergistic effect.Secondly,the active end group of nylon 12T was completely deactivated and stabilized.The different blocking agents and their dosages were tested for nylon 12T resistance.The effect of yellowing performance indicates that cyclohexanecarboxylic acid as a blocking agent can greatly improve the yellowing resistance of nylon 12T.Finally,a combination of a blocking agent with good yellowing resistance and an antioxidant system is used to prepare yellowing resistance.The modified nylon 12T with excellent performance makes it meet the requirements for whiteness of materials such as LED lamps.