Bioplastics Injection Molding
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 (TPS)
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 (PLA)
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.
Molds for Bioplastics
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.