With the increasing global environmental protection voice, the use of recyclable & sustainable plastic bags has also become more and more.
The main types of degradable plastic bags are as follows:
Biodegradable plastic bags composed of microorganisms, including biopolyester, biocellulose, polysaccharides and polyamino acids, are a type of biodegradable plastic bags that can be completely differentiated by microorganisms in nature.
The polylactic acid microbial degradable plastic bag is composed of lactic acid, which is a microbial fermentation product. It can be actively degraded after use. Polylactic acid can be processed into fibers and films with excellent mechanical properties, and its strength is comparable to that of nylon fibers and polyester fibers. Polylactic acid can be hydrolyzed into lactic acid and acetic acid in vivo, and metabolized into carbon dioxide and water by enzymes, which is especially suitable for medical materials. In Japan and the United States, polylactic acid plastics have been processed into surgical sutures, artificial bones, and artificial skin. Polylactic acid is also used in the production of packaging containers, agricultural mulching films, sportswear for fibers, and bedding.
Starch plastic bags, containing more than 90% starch, and other components added can also be completely degraded (January to 1 year), completely biodegradable plastic bags without leaving any traces, no pollution, can be used to make various containers, Bottles and cans, film bags and garbage bags, etc.
So, what are the potential advantages of developing crop-degradable plastic bags with starch as raw materials?
Starch has complete biodegradability in various environments. After the starch molecules in plastic bags are degraded or ashed, carbon dioxide gas is generated, which does not cause poisoning to soil or air.
The vast majority of starch plastic bags currently produced are filled starch plastics, that is, adding a certain amount of starch to non-biodegradable polymer materials, and the biodegradation of starch causes the physical collapse of the entire plastic bag, which promotes the exposure of many end groups. Oxidative degradation, but some of the remaining PE, PVC, etc. after this “collapse” cannot be degraded and remain in the soil, which will of course cause pollution over time, so such products are classified as screening type.
Photodegradable plastic bags
According to the production method, photodegradable plastics can be divided into constitutive degradable plastic bags and incremental degradable plastic bags.
Constitutive photodegradable plastics
a. Ethylene/carbon monoxide copolymer, the photodegradation is characterized by main chain cracking. The photodegradation speed and degree of E/CO are related to the amount of ketone groups contained in the chain. The higher the content, the faster the degradation speed and the greater the degree.
b. Vinyl/vinyl ketone copolymer, the defect of this type of polymer is that it starts to degrade once it is exposed to light, and there is almost no induction period. It needs to add antioxidants to achieve the purpose of conditioning the induction period.
Increased photodegradable plastic
The increased photodegradable plastic is to add a few photosensitizers to the polymer, which is a photooxidative degradation catalyst at a low concentration, and it acts by sunlight (ultraviolet light) irradiation, which makes the polyolefin polymer crack. Better photodegradability can be obtained by adding photosensitizers such as ketones and amines to polymers such as PE and PP.
The increased photodegradable plastic has low cost, simple production process, and better use as a covering mulch. However, its degradation characteristics are that the exposed surface degrades relatively completely, and the part buried in the soil degrades poorly. The degradation induction period of such photodegradable plastics can be controlled at more than two months. However, the controllability of the degradation time is poor.
