Low temperature plasma treatment improves the surface adhesion of plastics
Low temperature plasma treatment improves the surface adhesion of plastics:
Difficult to stick plastic mainly refers to polyethylene (PE), polypropylene (PP) and other polyolefin and polytetrafluoroethylene (PTFE), perfluoroethylene propylene (FEP) and other fluorinated plastics. This kind of plastic usually has the advantages that other polymer materials do not have, such as PE polyolefin plastic low cost, good performance, easy to process into various profiles, so it is widely used in daily life; PTFE, commonly known as plastic King, is a plastic with excellent comprehensive performance, excellent heat resistance, cold resistance and chemical corrosion resistance. It is widely used in the electronics industry and some cutting-edge fields. However, due to the difficult plastic surface is chemically inert, without special surface treatment, it is difficult to use general adhesive for bonding.
Reasons for difficult adhesion:
1.difficult to adhere to the plastic treatment molecular chain structure, high crystallinity, good chemical stability, their swelling and dissolution than the non-crystalline polymer is difficult, when the solvent adhesive bonding, it is difficult to occur polymer molecular chain diffusion and entanglement, can not form a strong adhesion.
2. PE molecular chain is non-polar polymer without any polar groups; There is -CH3 in the molecular structure unit of PP, but -CH3 is a very weak polar group, so PP basically belongs to non-polar polymer; Fluorinated plastics, such as PTFE, are also non-polar polymers due to their highly symmetrical structure. Adhesive adsorption in these difficult plastic surface can only form a weak dispersion force, but the lack of orientation force and induction force, so the adhesion property is poor.
3.difficult to stick plastics in addition to the structural reasons; There is also a weak boundary layer on the material surface. The weak boundary layer comes from the low molecular components of the polymer itself, the various additives added in the polymerization process, and the impurities brought by the processing, storage and transportation. This kind of small molecule material is very easy to precipitate and collect on the plastic surface, forming a weak interface layer with very low strength. The existence of this weak boundary layer greatly reduces the bonding strength of plastics.
Methods for surface treatment of hard-to-stick plastics:
At present, the improvement of adhesive properties of refractory plastics is mainly achieved by surface treatment and research and development of new adhesives. Among them, there are mainly the following several ways to treat the difficult plastic surface: (1) lead the human polar group on the molecular chain of the difficult plastic surface; (2) Improve the surface energy of the material; (3) Improve the surface roughness of products; (4) Reduce or eliminate the product surface of the weak interface layer. The surface treatment methods of refractory plastics include chemical treatment method, high temperature melting method, gas thermal oxidation method, radiation grafting method, ArF laser method and low temperature plasma method, among which low temperature plasma method has developed rapidly in recent years.
A low-temperature plasma is an ionized gas produced by a low-pressure discharge (glow, corona, high frequency, microwave, etc). Under the action of an electric field, free electrons in the gas gain energy from the electric field and become high-energy electrons. These high-energy electrons collide with gas molecules, atoms, if the electronic energy is greater than the atoms or molecules of the excitation energy can produce trigger molecules or atoms excited free radicals, ion and with different energy radiation, low temperature plasma in the active particles can be chemical reactive gas, inert gas (gas) or metal elements are usually close to or more than with the energy of a C - C key or other C key key can inject polymer surface by ion bombardment or, produce off key or the introduction of functional groups, the surface activity to achieve the purpose of modification, plasma cleaning machine can well solve the problem of low plastic surface adhesion.