Food bag science
Food bag science
Generally made of PE polyethylene PP polypropylene, food packaging bags. Synthetic resins are almost always used in plastics. Resin is the most important component in plastic, which acts as an adhesive and can bind other components of plastic into a whole. Although adding various additives can change the properties of plastics, resin is the fundamental factor that determines the type, performance and use of plastics.
The main material of food bags is generally PE polyethylene PP polypropylene, food bags are widely used in food packaging. Manufacturers of food bags must have QS certification.
Synthetic resins are almost always used in plastics. Resin is the most important component in plastic, which acts as an adhesive and can bind other components of plastic into a whole. Although adding various additives can change the properties of plastics, resin is the fundamental factor that determines the type, performance and use of plastics.
The types of resins commonly used in plastic decoration materials are:
Polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), phenolic (PF), urea-formaldehyde (UF), epoxy (EP), polyester (PR), polyurethane (PU), polymethyl Methyl Acrylate (PUMA), Silicone (SI), etc.
According to the changes that occur when heated, synthetic resins can be divided into thermoplastic resins and thermosetting resins.
It has the properties of softening by heating and hardening by cooling, and it does not react chemically. No matter how many times heating and cooling are repeated, it can maintain this property. All thermoplastic resins have a linear molecular structure. It includes all polymeric resins and partially condensed resins. Thermoplastic resins include: polyethylene, polyvinyl chloride, polystyrene, polyamide, polyoxymethylene, polycarbonate, polyphenylene ether, polysulfone, rubber, etc. The advantage of thermoplastic resin is that it is easy to process and shape, and has high mechanical energy. The disadvantage is poor heat resistance and rigidity.
After the resin is heated, it undergoes chemical changes and gradually hardens into shape. It will not soften or dissolve when heated again. The molecular structure of thermosetting resin is body shape, which includes most condensation resins. The advantages of thermosetting resin are high heat resistance and not easy to deform under pressure. Its disadvantage is poor mechanical properties. Thermosetting resins include phenolic, epoxy, amino, unsaturated polyester and silicone ether resins.
Fillers improve and enhance the properties of plastics. For example: adding fibers can improve the mechanical strength of plastics; adding asbestos can enhance the heat resistance of plastics; adding mica can enhance the electrical insulation properties of plastics; adding graphite and molybdenum disulfide can improve the abrasion resistance and wear resistance of plastics. Adding fillers can also reduce plastic costs.
Adding plasticizers to plastics can improve the plasticity and softness of plastics and reduce brittleness. Commonly used plasticizers are: dibutyl phthalate, dioctyl phthalate, tricresyl phosphate, camphor, benzophenone, etc.
Hardener is also called curing agent or curing agent. Its main function is to cross-link the linear molecular structure of the polymer into a bulk molecular structure, thereby making the resin thermosetting. The hardener commonly used in phenolic resin is urotropine (hexamethylenetetramine). Commonly used hardeners for epoxy resins are amines and acid anhydrides.
Adding colorants to plastics can make plastics have bright colors and luster. Colorants often use various pigments and dyes, and sometimes pigments that can produce fluorescence or phosphorescence.
During the molding process and product use of many plastics, due to the action of heat, light or oxygen, premature degradation, oxidative chain scission, crosslinking and other phenomena occur, which deteriorates the properties of the material. In order to stabilize the quality of plastic products and prolong their service life, stabilizers are usually added to their components. The commonly used stabilizers are stearate, lead white, epoxy and so on.
In plastic processing, lubricants are often needed in order to release the mold and make the product smooth. The commonly used lubricants are fatty acids and their salts. In order to make plastic products such as plastic mats and carpets antistatic, antistatic agents are added to improve surface conductivity and quickly discharge charged plastics.
In order to make plastic products have better performance and adapt to various application requirements, there are also: antioxidants, ultraviolet absorbers, flame retardants, foaming agents, luminescent agents, balsams, etc.
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