Bioplastics are plastics derived from renewable plant sources such as corn starch, instead of from petroleum. Most bioplastics are also biodegradable, meaning they can be decomposed by microbes under suitable environmental conditions, for example in a composting facility. Bioplastics have the potential to reduce dependence on fossil fuels and help alleviate plastic waste disposal problems.
Thermoplastic starch is made from starch with added glycerol or other biodegradable plasticizers to allow it to be formed by traditional plastic forming processes such as injection molding. Other biodegradable polymers are often added to the mixture to improve processing and physical properties. TPS is currently the most widely used bioplastic. It typically has a low cost relative to other bioplastics, and can be processed on standard plastics processing equipment without extensive modifications, making it competitive with traditional plastics. It is resistant to heat, so it can be used in applications involving contact with heated food.
The main disadvantages of TPS are that it absorbs water readily, and is fairly soft and low in strength. Other bioplastics such as PLA may be more suitable where water resistance and rigidity is required.
There are many different thermoplastic starch materials available on the market with a wide range of prices. Many of them contain a certain percentage of materials that are not biodegradable or are derived from petroleum sources, so it is important to choose wisely and ensure the resin you use meets applicable standards and customer requirements. It is also important to use a molder you can trust, as some factories will add traditional petroleum-based plastics such as polyethylene or polypropylene to the mixture to make molding easier, thus rendering the product poorly or incompletely biodegradable.
Polylactic acid is typically derived from corn starch or cane sugar. It has advantages over PSM in that it is similar to traditional plastics in appearance and strength. Unlike PSM, it can be used to manufacture transparent articles. However, PLA is less heat resistant than PSM, so it may not be suitable for items that will be in contact with hot food. PLA is often considerably more expensive than PSM, and may have a higher carbon footprint due to the extra processing steps needed in its manufacture.
Biodegradability of PLA depends on temperature. High temperatures, such as those present in commercial composting units, are required for fast decomposition. Thus PLA is often defined as a compostable plastic instead of a true biodegradable plastic.
Bioplastics are typically designed to accommodate traditional plastics processing methods as much as possible. However, physical properties of most bioplastics are still significantly different from traditional plastics, so plastic injection molds usually need to be designed or modified specifically for use with a particular bioplastic.
ChinaForgeTM has experience in designing injection molds for bioplastic processing and can produce a mold design to suit your particular product and your desired bioplastic material.