Page 65 - 《橡塑技术与装备》英文版2026年3期

THEORY AND RESEARCH

stability (decomposition temperature), and monomer structure. molecular weight and structure of the compounds, and the
types of nylon 6 and nylon 66 can be determined based on the
1 Experimental part structural formula and molecular weight information.
1.1 Experimental instruments and equipment TGA test of nylon 6 and nylon 66: A temperature rise rate
DSC: DSC214, Netzsch Scientific Instruments GmbH, of 10 K/min was adopted, with the temperature increasing from
Germany; 30℃ to 800℃. Throughout the entire process, N 2 was used
GCMS: PY3030D/7890B, Agilent Technologies, USA; as a protective gas. The weight loss curves of nylon 6, nylon
TGA: TGA/DSC1, Mettler Toledo, Switzerland. 66, and sample 2 (an unknown sample peeled off from a tire)
1.2 Sample were obtained. The decomposition temperature corresponding
Nylon 6 and nylon 66 are commercially available; to the maximum decomposition rate of the two materials
Four unknown samples (nylon cords peeled off from was investigated to determine whether it could serve as a test
tires). method for distinguishing between nylon 6 and nylon 66.
1.3 Testing and characterization
Melting point analysis of nylon 6 and nylon 66: Utilize 2 Results and discussion
DSC (differential scanning calorimeter) to test the prepared 2.1 Melting point analysis of nylon 6 and
samples of nylon 6 and nylon 66. Based on the measurement nylon 66
principle of the heat flow difference between the substance and In the field of material identification, accurately
the reference material during heating or cooling, analyze the identifying material categories is crucial for product
characteristic temperatures of nylon 6 and nylon 66 materials. performance evaluation and quality control. For tire cord
The test procedure is set at 210~310 ℃, with a heating rate of materials, specifying their specific type is one of the key factors
10 K/min, and the sample size is 5 mg. in ensuring tire performance and safety. Polyamide 6 (nylon 6)
Crystallinity testing of nylon 6 and nylon 66: The and polyamide 66 (nylon 66), as common tire cord materials,
principle involves calculating the crystallinity based on the are widely used due to their excellent performance. However,
heat released or absorbed during the phase transition of the due to their similar appearance, distinguishing between the two
material during heating. When the material is heated, there is can be challenging.
a difference in thermal stability between the crystalline and Existing literature reports have shown that due to the
amorphous regions. The molecules in the crystalline region are different structural compositions of nylon 6 and nylon 66, nylon
arranged tightly, requiring a higher temperature to disrupt their 6 can only form one hydrogen bond with two carbonamide
structure. Therefore, the crystallinity of the polymer can be groups, while the carbonamide groups of nylon 66 are arranged
inferred by measuring the heat of fusion. The specific formula relatively, allowing each functional group to form a hydrogen
is: heat of fusion on DSC × 100% / theoretical enthalpy of bond without molecular deformation. The theoretical melting
100% crystalline material. point of nylon 6 is 220 ℃, while that of nylon 66 is 260 ℃,
Monomer analysis of nylon 6 and nylon 66: During the and the significant difference in melting points provides an
experiment, a pyrolysis gas chromatography-mass spectrometer important physical basis for distinguishing between the two.
was used for analysis. The sample was cut into pieces and Based on this, this study selected standard samples of nylon 6
weighed at 2mg, then pyrolyzed at 550℃ with helium as the and nylon 66, as well as four unknown sample cords peeled off
carrier gas. The components separated by the chromatographic from tires, for testing and analysis.
column entered the mass spectrometer and were ionized into Differential scanning calorimetry (DSC) is a kind of
charged particles (ions) in the ion source. Under the influence commonly used thermal analysis technique that can accurately
of an electric field and magnetic field, these ions were separated measure the thermal effect changes of materials during heating
according to their mass-to-charge ratio (m/z), forming a mass or cooling, thereby obtaining key thermal performance
spectrum. The mass spectrum provides information on the parameters such as melting point. By conducting DSC melting

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