Why is nylon film easy to absorb moisture?
Classification of nylon film production process
Polyamide film: a linear polymer containing many repeating amide groups (- CO-NH -) in the PA molecular chain segment, with a specific gravity of 1.14 g / cm3. Polyamide (PA) refers to the polymer with amide group in the main chain, which is usually called nylon.
At present, nylon films used in China are all made of nylon 6 obtained by ring opening polymerization of caprolactam. And nylon film on the production and molding process is divided into: salivation method (CPA), blowing tube membrane method (IPA), biaxial stretching method (BOPA). Drawing method can be divided into synchronous drawing and asynchronous drawing.
Nylon film is a kind of directional film, and its properties are as follows:
A. After longitudinal and transverse stretching, the polymer molecules have a high degree of orientation, so they lose the heat sealing property, such as BOPP, pet, BOPA, etc;
B. The crystallinity is increased, the physical and mechanical properties are greatly improved, and the transparency is also improved;
C. The initiation tear strength is large, but the secondary tear strength is greatly reduced.
Why is nylon film easy to absorb moisture?
Nylon is mainly made of dibasic acid, diamine or amino acid group by condensation polymerization. Because polyamide contains a wide range of amide groups, but in the production process, not all the molecules in the polyamide can crystallize and coordinate with molecules, and there are some amorphous polyamide polar genes. The amide groups in the amorphous polyamide molecular chain can coordinate with water, that is to say, it has water absorption, and can absorb water molecules with strong polarity. In serious cases, it will form a The barrier and air tightness of nylon film are greatly reduced by water film.
