Evaluation of thermal and dielectric behaviour of some anionic nylon 612 copolymers
Introduction
The challenge to perform materials with tailored properties has focused the interest of researchers toward aliphatic polyamides (nylons) due to their excellent physico-chemical and mechanical features. A great variety of nylons and composites based on nylons can be obtained due to opportunity to choose the fraction and type of the components (monomers and matrix/filler, respectively) and the preparation method. These materials have gained a great importance for many field such as textile fibres, packaging, implants, membranes, biosensors, automotive, electrical/electronic and consumer applications [1], [2], [3], [4].
The semicrystalline character and the attractive properties of nylons stem from intra- and interchain hydrogen bonds (specific to α- and γ-crystalline phase, respectively) constituted between amide groups separated by methylene repeat unit with variable lengths [5]. The changing of the homogeneity in the structure of nylons by heating, copolymerization or addition of other compound as well as the slow crystallization seems to favour the γ-crystalline form. In the even nylons, such as nylon 6 all the NH and CO groups can establish hydrogen bonds between the adjacent molecular chains and a predominant trans conformation (α-form) of the macromolecular chains is present. In the same time, even–even nylons have the different crystal structures that even ones when methylene segments have not same lengths, as in the case of nylon 612. The gauche conformation of the molecular chain, namely γ-form, appear in the crystal lattice of these type of nylons to allow all the NH and CO groups to establish hydrogen bonds in the neighbouring molecular chains [6].
It is well known that nylon 6 has both desirable (high strength, stiffness, and resistance to nonpolar solvents) and undesirable (poor low-temperature toughness, moisture-sensitive) properties [7], [8], [9]. The anionic copolymerization of ϵ-caprolactam (CL) with another lactam (i.e. laurolactam, LL) is one promising pathway to modifying the properties of nylon 6 [7], [10], [11], [12], [13]. It is expected that the new nylon 612 copolymers with different content of the comonomer to combine the characteristics of the homopolymers.
The revealing of changes in the nylon properties needs knowledge of structural characteristics and understanding of the molecular dynamics in these polymers.
The survey of the literature has not yet revealed too many information about anionic nylon 612 copolymers obtained from corresponding lactams [13], [14], [15].
Taking into account all these it is of interest to contribute to evaluation of nylon 612 copolymers characteristics.
We focused our attention on the characterization of a series of nylon 612 copolymers based on lactams (CL and LL) with 0.0, 10.0, 20.0, 30.0, and 50.0 wt.% LL, denoted PCLL0–PCLL50 obtained by anionic copolymerization–rotational moulding combined technique.
The investigations were based on the fact that nylons are semicrystalline and rich in molecular dynamics and the amide groups have in FTIR spectra many characteristic bands (amide A, I–VII) especially related to chemical bonding and structure of materials [16], [17].
Properties of the nylon 612 copolymers have ascertained through the combined use of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy, X-ray spectroscopy (WADS) and broadband dielectric spectroscopy (BDS) measurements.
The thermal behaviour of the nylon 612 copolymers was also investigated by differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA).
The experimental results were correlated with initial content of LL and literature data and reported herein. For comparison of our results related to samples nylon 6 and nylon 612 copolymers with behaviour of other aliphatic polyamides reported in the literature one must take account that they were carried out on different polymers (obtained by anionic polymerization–rotational moulding process) and in different experimental conditions.
Section snippets
Materials
The monomers: ϵ-caprolactam (CL) (technical grade, Sigma–Aldrich Chem. Gmbh) and laurolactam (LL) (Huls – Germany) were used after purification in similar fashions to those described in the literatures [13], [18]. ϵ-Caprolactam magnesium bromide (1.6 mol/kg concentration in ϵ-caprolactam) as initiator, was obtained in our laboratories according to the procedure described in the literatures [19]. The activator, N,N′-isophthaloyl-bis-ϵ-caprolactam was synthesized in our laboratories [10], [18].
Synthesis of anionic nylon 612 copolymers
Anionic nylon 6 and nylon 612 copolymers were prepared by reactive rotational moulding process via anionic ring opening copolymerization of CL with of various weight content of LL comonomer. The process was performed in a laboratory scale rotational moulding installation. The content of LL was varied between 0.0 and 50.0 wt.%. With respect to CL and LL mixture the content of N,N′-isophthaloyl-bis-ϵ-caprolactam, as activator and ϵ-caprolactam magnesium bromide, as initiator, were kept constant at
ATR-FTIR analysis
The structure of all copolymers under consideration can be identified as polyamides by recording the ATR-FTIR spectra of their thin and transparent film at 25 °C. The various bands that appeared in the spectra of nylons PCLL0-50 represent spectral patterns for stretching and bending vibrations characteristic to their structural elements, secondary amide group –CO–NH– existing in the trans planar conformation and CH2 units [13]. The relationship between amide bands and molecular structure has
Conclusions
Nylon 612 copolymers with different concentrations of LL were obtained by in situ anionic ring opening copolymerization of CL with LL monomers using rotational moulding technique. The characteristics of the nylon 612 copolymers were compared to neat nylon 6. The nylon 612 copolymers properties (Tm, Tc, αDSC) were found to be directly dependent on the content of LL comonomer added to the copolymerization mixture. Nonisothermal crystallization behaviour of pure nylon 6 and the nylon 612
References (50)
- et al.
Preparation, characterization and crystalline transitions of odd–even polyamides 11, 12 and 11, 10
Eur Polym J
(2005) - et al.
In situ compatibilization of polyamide 6/natural rubber blends with maleic anhydride
Polymer
(2000) - et al.
Polyamides from lactams via anionic ring-opening polymerization: 1. Chemistry and some recent findings
Polymer
(1997) - et al.
Polymerization of lactams, 96 anionic copolymerization of ϵ-caprolactam with ω-laurolactam
Polymer
(2006) - et al.
Polyamides from lactams by centrifugal molding via anionic ring-opening polymerization
Polymer
(2001) - et al.
Anionic copolymers of caprolactam with laurolactam (nylon 612 copolymers). II. Crystallisation, glass transitions and tensile properties
Eur Polym J
(1983) - et al.
Dielectric properties of nylon 6/clay nanocomposites from on-line process monitoring and off-line measurements
Polymer
(2005) - et al.
FT-IR study for hydroxyapatite/collagen nanocomposite cross-linked by glutaraldehyde
Biomaterials
(2002) - et al.
Characterization of microbial poly (ϵ-l-lysine) by FT-IR, Raman and solid state13C NMR spectroscopies
J Mol Struct
(2003) - et al.
Morphology and properties of nylon 6–polyoxypropylene–nylon 6 block copolymers
Mater Chem Phys
(1994)
Preparation and characterization of nylon 6 11 copolymer
Mater Lett
The microstructural characterization of PA6/PA12 blend specimens fabricated by selective laser sintering
Polym Test
Aromatic polyisophthalamides with iminobenzoyl pendant groups
Eur Polym J
Unusual accelerated molecular relaxations of a tin fluorophosphate glass/polyamide 6 hybrid studied by broadband dielectric spectroscopy
Polymer
Investigation of the water absorption in polyamide and wood plastic composite by terahertz time-domain spectroscopy
Polym Test
Reversible crystallization and the rigid-amorphous phase in semicrystalline macromolecules
Prog Polym Sci
Optimisation of properties of ternary co-polyamides based on ϵ-caprolactam
Fibres Textiles Eastern Europe
Effect of particle size of filler on properties of nylon-6
J Miner Mater Charact Eng
Mechanical properties and morphology of nylon-6 hybrid composites
Polym Int
Thermal properties of aliphatic nylons and their link to crystal structure and molecular motion
J Therm Anal Calorim
Mesomorphic form (β) of nylon 6
Macromolecules
The effect of composition on the properties of nylon 612 copolymers
J Appl Polym Sci
Picosecond relaxations in hydrated polyamide-6 observed by millimeter-wave spectroscopy
J Polym Sci Part B: Polym Phys
Changes in the morphology of cast nylon 6 through copolymerization
J Appl Polym Sci
Caprolactam–laurolactam copolymers: fast activated anionic synthesis, thermal properties and structural investigations
Macromol Chem Phys
Cited by (28)
Evaluation and realization of safer Mg-S battery: The decisive role of the electrolyte
2021, Nano EnergyCitation Excerpt :This indicates the upper pressure limit of the CR2032 cell at 403 K and 455 K, respectively. The Nylon‐6 O‐ring that seals the cells becomes less thermally stable above 423 K [46]. Its ability to withhold the over-pressure then decreases.
Ultrafine electrospun fiber based on ionic liquid/AlN/copolyamide composite as novel form-stable phase change material for thermal energy storage
2021, Solar Energy Materials and Solar CellsCitation Excerpt :Hence, aluminum nitride (AlN) could be a suitable addictive in this research because of its high thermal conductivity, chemical stability and high electrical resistivity [39,40]. Polyamide has been widely used as fibers and engineering thermoplastics due to its high strength, stiffness, and resistance to nonpolar solvents [41]. The thermal conductivity of polyamide (250 mW m−1 K−1) is higher than most of polymer substrate, like polyester (140 mW m−1 K−1) and cotton (71 mW m−1 K−1) [42].
Thermally stable, conductive and flame-retardant nylon 612 composites created by adding two-dimensional alumina platelets
2017, Composites Part A: Applied Science and ManufacturingCitation Excerpt :Unexpectedly, when the loading level of alumina increases up to 40 wt%, another melt peak (Tm3) appears at a very low temperature of only 129.6 °C, about 86 °C lower than that of the main melt peak. This endothermic peak was reported to belong to the melting of the γ-phase crystalline region relating to the reflection of crystalline plane (1 0 0) of PA612 [27,29,30]. This indicates that the a great quantity of alumina platelets can induce the formation of γ-phase crystalline, as evidenced by X-ray diffraction results [27,29].
Effect of materials on the noise of a water hydraulic pump used in submersible
2017, Ocean EngineeringCitation Excerpt :Polytetrafluoroethylene (PTFE) is extensively used in a polymer-metal system operating in an aqueous environment because it has excellent self-lubrication ability, good resistance to chemical attack (Tevruz, 1998). Aliphatic polyamides (NYLON), especially NYLON 6, has both desirable high strength and stiffness (Rusu and Rusu, 2010). In this study, the TC4 titanium is used to manufacture the inflow and discharge valve spool due to its excellent strength to density ratio.
Correlations between thermal and tensile behavior with friction coefficient in copolyamides 6/12
2017, WearCitation Excerpt :Budin et al. studied the effect of CLNa and CLMgBr as initiators in the structure and thermal properties [11]. Rusu et al. evaluated copolymers PA6/12 thermal, physical, mechanical and dielectric properties, obtained from anionic polymerization by using the centrifugal molding technique; they used EtMgBr and CLMgBr as initiators, at 160 °C as polymerization temperature in 0–50 wt% LL [12–14]. Cast PA6 is applied today as a replacement for metal parts; the selection of the appropriate polyamide grade is difficult because the sliding mechanisms are still unknown.