Transparent nylon is a kind of polymer material with excellent comprehensive properties. It not only has the advantages of high mechanical strength, good thermal stability, excellent corrosion resistance, but also has the advantages of easy molding processing, good dimensional stability, small linear expansion coefficient, high cost performance, excellent electrical insulation and aging resistance, non-toxic, odorless, easy to form alloy with other amorphous or semi-crystalline polycool amine.
On the one hand, it has excellent transparency (transparency even exceeds PC, close to PMMA), and on the other hand, it is more superior than ordinary transparent polymer materials (such as PS, PC, PMMA, etc.) in environmental stress cracking resistance, oil solvent resistance, scratch resistance, wear resistance, etc.).
01
Modified preparation
Since nylon is a semi-crystalline polymer, usually white and translucent, in order to produce nylon with high light transmittance, three aspects can be considered:
(1) Reduce the crystallization capacity of polycoolamine, thus obtaining amorphous products;
(2) Reduce the crystal size of the crystal region, so that the diameter of the crystal is less than the visible light wave wavelength, the transport method is also known as the microcrystallization method;
(3) Polycoolamine is modified by blending, copolymerization and other methods to adjust the refractive index of the amorphous region and the crystal region, so that they have the same refractive index.
The method of the main transparent nylon supplier is to introduce monomer containing side group or ring structure, destroy the regularity of molecular chain, and obtain amorphous or microcrystalline transparent nylon. Common transparent nylon types are
PA MACM12, PA 12/MACMI, PA 6I/X and so on.
Due to the choice of monomers with ring structure or side chain structure, the composition of almost every brand of transparent nylon is not the same, here are two varieties to illustrate.
One is PATMDT (TMD is a mixture of 2,2,4 and 2, 4, 4-trimethylhexanediamine, and T is terephthalic acid), such as Evonik's Trogamid T series, whose aromatic ring structure further prevents the molecular bond between the polymer chains to form an amorphous polymer with high light transmittance.
There is also PACM12, which further uses aliphatic monomers to replace aromatic ring monomers, achieving the semi-crystalline state of the polymer, and because the size of its crystals can only reach the nanometer level, it does not affect the propagation of visible light, so it maintains the high light transmittivity of the material.
02
Processing injection molding and precautions
The injection molding temperature of transparent nylon is 300~315℃, and the temperature of the barrel should be strictly controlled during the molding process. Too high melt temperature will cause discoloration of the product due to degradation, and too low temperature will affect the transparency of the product due to poor plasticization. The mold temperature should be as low as possible, and the high mold temperature will reduce the transparency of the product due to crystallization.
Some transparent nylon parts, sometimes through the light can see some glittering filaments of silver, these silver patterns are also known as shuo spots or cracks, can use the following solutions:
(1) Eliminate the interference of gas and other impurities, and fully dry the plastic.
(2) Reduce the material temperature, adjust the cylinder temperature in stages, and appropriately increase the mold temperature.
(3) Increase the injection pressure and reduce the injection speed.
(4) Increase or reduce the pre-plastic back pressure and reduce the screw speed.
(5) Improve the flow channel and cavity exhaust conditions.
(6) Clean up possible blockage of nozzle, runner and gate.
(7) Shorten the molding cycle, after stripping can be used to eliminate silver grain annealing method.
03
Apply
Transparent nylon is now widely used in the surrounding mechanical and electrical parts involving fuel and oil (such as lighter oil tank, flowmeter sleeve, filter cover, filter cup, circuit breaker and high voltage switch housing, etc.), Especially in the fields of precision optical instruments, pressure-resistant Windows, viewing glasses, special lamp covers, food packaging films, high-grade sports equipment and other applications can not be replaced by other materials. In addition, transparent nylon is also widely used in household appliances, such as hot kettle gauges, baby food processors, baby meal spoons, coffee beans, milk containers, multifunctional processors and other kitchen appliances.
