(1) Acetic acid Acetic acid is the main component of vinegar, so it is also called acetic acid. It is a colorless liquid with a strong pungent odor, with a boiling point of 118°C and a melting point of 16.6°C. When the temperature is lower than its melting point, it condenses into ice crystals, so it is also called glacial acetic acid. Acetic acid is easily soluble in water and ethanol.
Acetic acid has the typical properties of carboxylic acid, which are mainly manifested in the following two aspects:
① Acidic acetic acid has obvious acidity and can ionize to produce hydrogen ions in aqueous solution. It is a Kind of weak acid.
The ionization constant Ki of acetic acid is 1.8×10-5 (25℃), and its acidity is stronger than that of carbonic acid (the first-level Ki is 4.3×10-7 at 25℃). Acetic acid has acid properties. For example, it can turn blue litmus paper red; it can react with metals, as well as with alkali, sodium carbonate, and sodium bicarbonate.
Polyvinyl chloride (PVC) is toxic
The original color is yellowish, translucent and shiny. The transparency is better than polyethylene and polystyrene, but worse than polystyrene. Depending on the amount of additives, it is divided into soft and hard polyvinyl chloride. Soft products are flexible and tough and feel sticky, while hard products have a higher hardness than low-density polyethylene. , and lower than polypropylene, whitening will occur at the inflection point.
Common products: sheets, pipes, shoe soles, toys, doors and windows, wire sheaths, stationery, etc.
Polyethylene terephthalate PET
Transparency Very good, strength and toughness are better than polystyrene and polyvinyl chloride, not easy to break.
Common products: often bottle products such as cola, mineral water bottles, etc.
Polyethylene waste
Polyethylene is the largest plastic and has the most wide range of uses. Thermoplastic, which is polymerized from ethylene, is a partially crystalline material and can be processed by the molding methods of general thermoplastics. Polyethylene can be divided into three categories: high-density polyethylene, low-density polyethylene and linear low-density polyethylene.
The density of high-density polyethylene is generally higher than 0.94g/cm, while the density of low-density polyethylene and linear low-density polyethylene is between 0.91 and 0.94g/cm. There are two main sources of waste polyethylene films:
1. Leftovers and defective products produced in film production. These waste materials are clean and have clear varieties. They can be crushed and compressed and sent directly to the extruder for granulation. The recycling process is relatively simple.
2. Waste films from the chemical industry, electrical industry, food and consumer goods industry, etc. These waste films have been contaminated, some have been colored and printed with trademarks, and some also contain impurities such as sand, sawdust or shredded paper.
Because polyethylene is cheap, easy to obtain and easy to mold, its products have a wide range of applications, but the most used ones are packaging products, estimated to be more than 60. High-density polyethylene is mainly used in packaging films, bottles, and hollow containers; low-density polyethylene is mainly used in packaging films and agricultural films; linear low-density polyethylene is mainly used in films, film plastics, and pipes. And on wires and cables.
Polyvinyl chloride waste
Polyvinyl chloride used to be the most widely used plastic in history. Now it is replaced by polyethylene and PET in some fields, but it is still used in large quantities. Use, its consumption is second only to polyethylene and polypropylene. Polyvinyl chloride products are available in various forms and can be divided into three categories: hard polyvinyl chloride, soft polyvinyl chloride, and polyvinyl chloride paste. Rigid polyvinyl chloride is mainly used in extruded products such as pipes, door and window profiles, and sheets, as well as injection molded parts such as pipe joints, electrical parts, and extrusion-blown bottle products. They account for more than 65% of PVC consumption. Soft PVC is mainly used in calendered sheets, automotive interiors, handbags, films, labels, wires and cables, medical products, etc. PVC paste accounts for about 10% of PVC products, and its main products include slush molding products.