Authors:Pingle Liu, Haike Zhang, Sihua Liu, Zhengjie Yao, Fang Hao, Kuiyi You, and He'an Luo
The hydrogenation of nitro compounds is an interesting industrial process for the manufacture of a great variety of oximes, amines and amides. Of these, cyclohexane oxime and ∊-caprolactam are important
The copolyamides consisting of ε-caprolactam and 6.1–24.5 wt.% of nylon salt prepared from adipic acid and 1-(2-aminoethyl)
piperazine were synthesized. Physical and thermal characteristics of polyamide 6 and the copolyamides were compared. Nylon
salt does not influence the polyreaction equilibrium so it is possible to prepare the copolyamides with high molecular weight
and with the content of low-molecular compounds comparable with that of pure PA 6. Melting temperatures of the copolyamides
are lower in comparison with PA 6 and decrease proportionally to the amount of the nylon salt. The thermal stability of the
copolyamides is good and equal to that of PA 6. The melting enthalpies indicate that the process of crystallization of the
copolyamides is influenced by the time of crystallization and the amount of comonomer present. Longer time of the crystallization
assures higher degree of crystallization. The kinetics and the level of crystallization are positively influenced by the mobility
of copolyamide segments mainly up to 10 wt.% of comonomer.
Both the activated and the non-activated alkaline polymerization ofε-caprolactam were studied by DSC. In the latter case, a curve-resolving method was applied to separate the superimposed polymerization and crystallization processes. The counter-ion effect was taken into account in the complexing of the initiator cations by crown compounds.
Authors:Dongshun Zhang, Rijie Wang, Xiaoxia Yang, and Wensheng Yao
A series of phosphorus modified Si-MCM-41 catalysts prepared via the impregnation method were used for the vapor-phase Beckmann
rearrangement of cyclohexanone oxime to caprolactam. The catalysts were characterized by XRD, N2 adsorption, FT-IR, and NH3-TPD. The results indicated that weak acid sites increased with P content, leading to enhanced catalytic activity. The catalyst
with Si/P mol ratio of 25 showed best performance at 633 K. The conversion of cyclohexanone oxime and the selectivity for
caprolactam were 92.7 and 64.2%, respectively. The P–OH groups are main active sites for the Beckmann rearrangement. Grafting
acid hydroxyl groups to cover the Si–OH groups may be a good way to improve the selectivity for this reaction.
Authors:Dongling Han, Longxiao Liu, and Xinghua Wang
The thermal properties of caprolactam/long chain lactam copolymer were studied with a Perkin-Elmer DSC 7. The melting point
(Tm), heat of fusion (δHm), crystalline degree (Xc), crystallization temperature (Tc) and glass transition temperature (Tg) of the copolymers increase with decrease of the content of the log chain lactam. From the changes in the mechanical properties
with corresponding changes in the thermal properties, it is clear that the copolymers are thermal plastic and elastic. In
addition, it is found that the results at a heating rate of 10 deg·min−1 are almost the same as that at 20 deg·min−1 after thermal history is erased.
Authors:M. Krištofič, A. Marcinčin, and A. Ujhelyiová
The DSC method was used to obtain more information on changes of thermal properties connected with different comonomers bound
in the (co)polymer chains. The copolyamides propered were block ones which were less crystalline and compatible with poly-&-caprolactam.
The results have confirmed the crystalline nature of polyamides and copolyamides.
Polyamide-6-block-polybutadiene copolymers have been prepared by the anionic polymerization of ɛ-caprolactam in presence of
α,ω-dihydroxy terminated polybutadiene. TG, Hi-Res™ TGA, DSC, TMDSC and DMA techniques have been applied. The suitability
of the methods used to determine the content, thermal stabilities and glass transition temperatures of the components constituting
the block copolymer is discussed.
The thermal degradation of the aliphatic polyamides 6 and 66 was investigated by means of the combined techniques TA-MS and TA-FTIR. The analyses were performed in three different devices. Sample mass ranged from 13 mg to 1 g and heating rates of 2.6 and 10 K min–1 were used in both air and nitrogen atmospheres. The most important decomposition products were caprolactam for PA 6 and cyclopentanone for PA 66. Evolution of NH3 and HCN was registered. The findings of the two hyphenated techniques led to the same results and complemented each other well. The evolved products were captured and analyzed off-line by GC/MS for further confirmation of results.
Differential thermal analysis and thermogravimetry have been carried out on oligoamidophosphates with established plastifying and anti-ignition effects, which contained various amounts or bound phosphorus, had different molecular masses, and were obtained on the basis of epsilon-caprolactam, oligo- or polycaproamide. The ranges of thermal stability were determined and some differences between the combustion mechanisms of the starting polycaproamide and the oligoamidophosphates were shown. A probable mechanism of the anti-ignition action of the latter is proposed.
Authors:J. Ryba, A. Ujhelyiová, M. Krištofič, and I. Vassová
This article focuses on the thermal properties of PA 6 and additives, i.e. ternary copolyamides, concentrates consisting of
binary or ternary copolyamides + nanoadditive montmorillonite Bentonite 11958 or Cloisite 15A and PA 6 fibres modified with
Bentonite, copolyamide and concentrate. The copolyamides are prepared from ε-caprolactam as a major comonomer and nylon salts
AN2 from adipic acid + 1-(2-aminoethyl)piperazine and ADETA from adipic acid + diethylenetriamine. All copolyamides and concentrates
exhibit lower melting temperatures Tm and lower melting enthalpies ΔHm compared to neat PA 6. PA 6 fibres modified with 0.25–2.5 wt% MMT exhibit higher melting enthalpies in comparison with unmodified
PA 6 fibres. PA 6 fibres modified with 10 wt% of ternary copolyamide containing 21.4 wt% of comonomers AN2 and ADETA have
higher melting enthalpy as well. PA 6 fibres modified with 10 and 20 wt% of concentrate containing the same ternary copolyamide + 5
wt% of MMT have higher melting enthalpies and higher tensile strength in comparison with these characteristics of unmodified
PA 6 fibres.