Cosmetic plastic hoses are generally polymers formed by initiators such as vinyl chloride monomers, peroxides, azo compounds, or through free radical polymerization mechanisms under the action of light and heat. The homopolymer and copolymer of vinyl chloride are collectively referred to as vinyl chloride resin. This material is amorphous. In practical use, PVC materials often contain additives such as stabilizers, lubricants, auxiliary processing aids, pigments, and impact resistant agents. Non flammable, high strength, weather resistance, and excellent geometric stability.
PVC has strong resistance to oxidants, reducing agents, and strong acids. But it can be corroded by concentrated oxidizing acids, such as concentrated sulfuric acid, concentrated nitric acid, etc., and should not come into contact with aromatic hydrocarbons and chlorinated hydrocarbons.
Selection of plastic hoses and pipes for cosmetics:
A. Hygiene of plastic hose materials for cosmetics
Firstly, the materials used must comply with relevant hygiene standards, and harmful substances such as heavy metals and fluorescent agents must be controlled within the specified range. For example, for hoses exported to the United States, polyethylene (PE) and polypropylene (PP) should comply with the US Food and Drug Administration (FDA) standard 21 CFR 117.1520.
B. Barrier performance of plastic hose materials for cosmetics
If the content of packaging for daily chemical enterprises is products that are particularly sensitive to oxygen (such as some whitening cosmetics) or products with highly volatile fragrance (such as essential oils or some corrosive chemicals such as oils, acids, and salts), a five layer co extruded tube should be selected. Because the oxygen permeability of the five layer co extruded pipe (polyethylene/adhesive resin/EVOH/adhesive resin/polyethylene) is 0.2 to 1.2 units.
The oxygen permeability of ordinary polyethylene single-layer pipes is 150-300 units. Within a certain period of time, the weight loss rate of ethanol in co extruded tubes is several times lower than that in single-layer tubes. In addition, EVOH is an ethylene vinyl alcohol copolymer with excellent barrier and fragrance retention properties (with the best effect at a thickness of 15-20 microns). The double-layer pipe adopts high-density HDPE and LDPE combined with low-density PE in a certain proportion, and achieves a uniform mixing effect through high-speed rotation. This method can adjust the softness and hardness of the hose appropriately. Compared to single-layer pipes, the pipe body is thicker and has better corrosion resistance.
C. Hardness of plastic hose materials for cosmetics
Daily chemical enterprises have different requirements for the stiffness of hoses, so how can we obtain the desired stiffness? The commonly used polyethylene for hoses includes low-density polyethylene, high-density polyethylene, and linear low-density polyethylene. Among them, the rigidity of high-density polyethylene is better than that of low-density polyethylene, so the required rigidity can be achieved by adjusting the ratio of high-density polyethylene to low-density polyethylene.
D. Chemical resistance of plastic hose materials for cosmetics
High density polyethylene has better chemical resistance than low-density polyethylene.
E. Weathering resistance of plastic hose materials for cosmetics
In order to control the short-term or long-term performance of hoses, factors such as appearance, pressure resistance/drop resistance, sealing strength, environmental stress cracking resistance (ESCR value), loss of fragrance and active ingredients need to be considered.