Polyethylene containers have good acid and alkali resistance, but are not resistant to many organic solvents, while nylon containers are resistant to hydrocarbons and organic solvents, but have poor acid and alkali resistance (especially poor acid resistance). Polycarbonate bottles can be used for the packaging of goods (such as juice) that are filled at high temperatures, but if polycarbonate bottles are used for carbonated beverages that require good barrier properties (to prevent the escape of carbon dioxide in the beverages) or edible oil ( It is necessary to prevent oxygen from entering the bottle to avoid oxidation and rancidity of the edible oil), the product cannot be well protected, and the ideal packaging effect cannot be obtained; while the ordinary polyester stretch bottle packaging carbonated beverages can effectively prevent Carbon dioxide escapes (polyester stretch bottles have excellent barrier properties). Using them in the packaging of edible oils can delay the oxidative deterioration of edible oils and extend its shelf life (polyester stretch bottles have good oxygen barrier properties and can effectively prevent Oxygen in the upper atmosphere enters the bottle through the wall of the container), but when it is used to package high-temperature filled juices and other commodities, when filled at high temperature, the polyester stretch bottle will undergo serious deterioration and lose its use value.
Polyethylene cosmetic containers can contain acids and alkalis rather than organic solvents such as benzene and toluene (the swelling strength of polyethylene bottles is significantly reduced or organic solvents escape through the container walls), while nylon containers are not suitable for storage of acids and alkalis. It is very suitable to contain organic solvents such as benzene and xylene.
The following points should be paid attention to in the formula design of polyethylene:
(1) Various types of polyethylene and ethylene copolymers. Such as: ethylene and vinyl acetate (EVA), ethylene and vinyl alcohol copolymers, etc. have good compatibility, so it can be blended and modified to improve the performance of the blend;
(2) The same product type, such as film, can be manufactured by multiple production processes. The same kind of raw material, due to different production processes, will have great differences in product performance; even if the same product is the same raw material and production process, the process parameters used are different, the product performance will be different, so , In addition to the production formula and process, you should also pay attention to the temperature, shear stress, stretching ratio and other parameters in the production;
(3) When using rubber and plastics to modify, it is better to use powdered rubber, or use a double-roll rubber mixer to fully mix with plastics, and then pelletize them for production, otherwise the rubber will not be easily dispersed into the plastics. When using functional materials such as fillers, antioxidants, antistatic agents, etc., it is better to use master batches to achieve a more uniform addition effect;
(4) The important principle of the formula is to use a process with low price and simple production method while fully meeting the requirements of the product.
The modification of plastics includes chemical modification and physical modification. Blending formulation is a physical modification, and lamination is also a modification. Even if the two materials are completely compatible, they should be mixed thoroughly to have a good effect. The properties of the blend are the sum of the properties of two completely compatible substances and their weight percentage in the blend.