Injection Molding of High-Performance Bioplastics

As consumers become more interested in environmentally sustainable products, and also governments and regulatory bodies place more strngent requirement on environmental sustainability of products manufacturers are forced to increasingly seek products that are regarded as more environmentally friendly by consumers, governments and regulatory bodies. At the same time, to remain competitive, these products still need to be good enough to meet the performance demand also. This is particularly important in an increasingly globalized world where a manufacturer is likely competing with manufacturers who are producing and selling in regions with diverse regulatory requirements and diverse consumer demand.

Bioplastics have increasingly received attention for their environmental friendliness¹. However one issue that has always been raised when it comes to producing parts from bioplastics has always been if such materials will match the processibility and performance of their non biodegradable counterparts². This has led to the development of high performance bioplastics that are expected to meet both environmental and performance requirements.

In the early years of bioplastics, they were primarily intended for temporary biomedical applications such as disolvable sutures, in consumer goods they were mainly used in disposable products and packaging. Bioplastics still have only around 1% market share of the plastics industry to date. However as the downside of conventional plastics becomes increasingly more apparent to the point of being a global issue, manufacturers increasingly look to bioplastics as alternatives. High-performance bioplastics capable of meeting demanding engineering requirements pose a wider commercial significance than temporary use disposable bioplastics.

Other than performance, bioplastics need to be processible. They need to fit into the conventional and advanced injection molding processes without needing significant modification. This impacts their widespread adoption and capital cost of manufacturing products from bioplastics.

High performance bioplastics are advanced materials that combine renewable or biodegradable characteristics with excellent mechanical strength, thermal stability, chemical resistance, and durability. With injection molding being a widely used manufacturing process accross diverse industries from automotive, electronics, medical devices, consumer goods, aerospace, to industrial equipment , it is important to establish a range of high perfromance bioplastics that are suited for injection molding process.

When applied to high-performance bioplastics, injection molding enables manufacturers to produce lightweight, durable, and environmentally friendly components suitable for high-value applications.

Therefore in this article we explore the injection molding process for high-performance bioplastics. We discuss different classifications of high performance bioplastics, the material properties, processing parameters, design considerations and challenges associated with injection molding of high performance bioplastics.

High Performance Plastics

These are a class of plastics that are designed to match or even exceed the performance of materials like glass and steel in applications under extreme conditions. These materials combine the desirable properties of plastics such as moldability, corrosion resistance and lightweight with the toughness and thermal resistance of traditionally tougher materials like steel, titanium and glass. These are referred to as high performance plastics.

These plastics can either inherently possess these high performance properties as a result of their basic chemistry or they have been modified or specially formulated to achieve their high performance properties. Where they have been specially formulated, you might find them available as brand names with different grades. An example is the Ultramid®PA from BASF. While the base polymer is polyamide, it has been specially formulated into different grades to meet different high performance applications.

Within the context of this article, high performance bioplastics refer to bioplastics whose mechanical and thermal properties exceed those of other bioplastics. These may not be competitive with fossil derived or non biodegradable high performance plastics in terms of performance under extreme conditions. However when compared to other bioplastics they are regarded as high performance..

Key Features of High-Performance Bioplastics

Within the concept of this article “bioplastics” refers to the biodegradabie or bioderived plastics. These are plastics that are either produced from monomers sourced from nature or will be degraded in the environment in the presence of microbes and moisture either under normal conditions or in industrial compost environment.

High-performance bioplastics are advanced bioplastics or biopolymer materials that are engineered to provide superior mechanical, thermal, and chemical properties for long-term applications.

Key characteristics include:

• High tensile and flexural strength
• Good impact resistance
• Excellent dimensional stability
• High heat resistance
• Low density for lightweight applications
• Improved chemical resistance
• Reduced carbon footprint

These properties make them suitable for manufacturing components that require reliability under mechanical stress and elevated temperatures.

Industrial Applications of Injection Molded High Performance Bioplastics

Existing and potential application of injection molded high-performance bioplastics extends across diverse industries including automotive industry where they find use in Interior trim, dashboard components, and air duct systems amongst others. In such applications their lightweight nature contributes to improved fuel efficiency and reduced emissions.

They also have existing and potential applications in medical devices. Injection-molded bioplastics are increasingly used for surgical instruments, drug delivery devices, and diagnostic equipment. Electronic manufacturers utilize high-performance bioplastics in applications such as device housings, keyboard components, connectors, battery enclosures
And wearable devices.Injection molded high performance bioplastics also have applicability in industrial equipment manufacturing as machine components, gears, bearings, handles, and protective covers increasingly incorporate reinforced bio-based polymers to improve sustainability without sacrificing performance.

Classification of High Performance Biopolymers

The term bioplastics is used within the context of this article as biodegradable or biobased plastics. These can either be biobased or non biobased. Some high-performance bioplastics are biodegradable but not biobased, while others are bio-based but not biodegradable.
. Here we’ll explore bioplastics that fall into any of the following 4 different classes of high performance biopolymers. These are:

• High Performance Biobased Synthetic Biodegradable Biopolymers
• High Performance Biobased Synthetic non biodegradable Biopolymers
• High Performance Fossil based Synthetic Biodegradable Biopolymers
• High Performance Biobased Natural Biodegradable Biopolymers

Polylactic Acid (PLA)

PLA is a biobased diodegradable natural biopolymer. It is among the most widely used bioplastics due to its renewable origin and ease of processing. The properties of PLA varies significantly for different grades. Properties like molecular weight, degree of polymerization and composition of D and L lactide in the chains as well as other factors like the additives used, determine the properties of the particular PLA you have.

In most cases PLA is blended with other polymers like ABS or reinforced with fillers such as glass fibers to improve properties such as stiffness, heat resistance, and dimensional stability. This modification makes them better suited for engineering applications.

While standard unmodified PLA has relatively low impact resistance and heat distortion temperature, high performance PLA can achieve high temperature resistance, impressive mechanical strength, excellent surface finish and good stiffness as well as good processibility. Luminy® from Total Energies Corbion is one of the leading brands of high performance PLA designed for injection molding.

High perfromance PLA grades can achieve tensile strength of 50MPa. Crystaline PLA grades designed for injection molding can withstand service temperatures of up to 105oC.
High performance PLA grades intended for injection molding typically gets processed between 180 and 220 oC, and 50 to 100 bar pressure and relatively low screw speed between 20 and 100 rpm. These values might not seem exceptional when compared to high performance fossil based plastics, however for bioplastics these are quite impressive.

Strict moisture control and mold temperature control is still required for high performance PLA to achieve dimensional stability and adequate crystalization of the part in order to retain good heat resistance and prevent defects.

Polyhydroxyalkanoates (PHA)

PHA is a class of biopolymers that are biosynthesized by certain bacteria. Unlike PLA where the microbes synthesize the lactic acid monomer alone, PHA producing bacteria produces the whole polymer through fermentation process. The manufacturing process involves creating the environment for the microbes to metabolize PHA and separation and purification stages to obtain the pure polymer.

PHA grades can achieve heat deflection of up to 140oC. They also have good barrier properties against water vapor and oxygen. Despite these impressive properties for a bioplastic, PHAs have desirable biodegradability. They can biodegrade in household compost and in the soil and waters without need for specialized composting facilities.
Performance of PHAs can be improved by reinforcing and blending with other polymers like PLA. PHAs inherently have tensile strength of around 40MPa, a glass transition temperature between 2 and 4oC and a melting temperature of 175oC. The properties of PHAs vary significantly with chain length. Medium chain length PHAs are generally more elastic while short chain length PHAs tend to be more brittle making them less suitable for processes like injection molding. While the medium chain length PHAs are better candidates for injection molding, formulations still need to be optimized to meet the demands of injection molding process.

Injection molding grades of PHAs are commercially available from manufacturers like Helian Polymers. PHA is typically processed with barrel temperature between 155 and 175oC with mold temperatures ranging between 60 and 80oC. As bioplastics are more prone to thermal degradation, keep residence time in the barrel as low as possible. Gates should not be excessively small, use vents and avoid high shearing.

Bio-Based Polyamide

Polyamide (PA) is a high performance plastic conventionally produced from petrochemical based feedstock. New development in sustainable polymer synthesis has led to the development of bio based polyamide. This is a biobased synthetic bioplastic that is synthesized from monomers that are derived from renewable, biological sources.
Since the chemical structure of biobased polyamide is identical to conventional polyamide from petrochemical feedstock, bio-based polyamide possesses the same high performance properties of polyamide. Bio-based polyamides provide high strength, excellent wear resistance, and good thermal stability. As more manufacturers seek to make their processes and products more environmentally compliant, bio-based PA is increasingly replacing petroleum-based PA in automotive and industrial applications. Processing of biobased of PA is identical to the processing of conventional fossil based PA.

Polyethylene Furanoate (PEF)

PEF is a biobased biodegradable polymer obtained from monoethylene glycol derived from ethanol which is derived from the fermentation of natural sugars and 2,5-furandicarboxylic acid that can be derived from fructose obtained from a combination of fermentation and metal catalyzed oxidation. PEF is often used as a biodegradable and biobased alternative to polyethylene terephthalate (PET). Although it has a lower melting point and crystallisation mechanism than PET. Its performance surpasses those of other bioplastics.

PEF can be ideally injection molded around 225oC which is well below its melting point of around 250oC. This avoids thermal degradation and associated defects. Injection pressure of 950 to 1050 bar screw speeds between 60 and 100 rpm and mold temperatures between 30 and 40oC are recommended. PEF is prone to moisture degradation therefore a thorough drying process prior to feeding into the injection machine is required.

This biopolymer is particularly priced for its exceptional gas barrier properties as well as its mechanical and thermal properties that rival those of PET. The company Avantium produces Releaf®, a commercial brand of PEF, that is marketed as a recyclable plant-based recyclable alternative to PET.

Cellulose-Based Plastics

Cellulose is the most abundant polymer on earth as it is found in all plant cell walls, some algae and cellulose producing bacteria. Wood is 40 to 60% cellulose. The first commercially successful plastics were derived from cellulose; celluloid, a bio derived plastic synthesized from cellulose nitrate and camphor.
Cellulose acetate is another bio-derived biodegradable plastic derived from cellulose. It is produced from the cellulose and acetic acid in an esterification reaction. The mechanical and thermal properties as well as processibility of cellulose acetic can be significantly varied by altering the degree of substitution of the hydroxyl groups of the cellulose with the acetic groups.
Cellulose acetate is used in textiles, photographic films, frames for eyewear, telephones, toothbrushes, radios, toys amongst others. Eastman Tenite Cellulosics is commercially available injection grade cellulose acetate that is commonly used in the production of frames for eye glasses and accessories.
Cellulose acetate is typically processed at a barrel temperature between 180 and 220oC and a mold temperature between 40 and 80oC. Screw speed can vary between 30 and 75rpm, injection pressure ranging between 70 to 120 MPa and a back pressure of 5 to 15 MPa.

Cellulose fiber is widely used as filler in the formulation of high performance plastics that are injection moldable. Nanocellulose has been widely explored for improving the performance of biopolymers when used as fillers. The cellulose fiber reinforced polymers have higher thermal resistance, tensile strength and flexural strength compared to the neat polymers.
Such cellulose reinforced plastics can be used in injection molded parts like electronic casings and automotive interiors.

Natural Rubber Based Bioplastics

Epoxidized natural rubber (ENR) is another type of bioderived bioplastic that offers the potential for achieving high performance injection molded parts. ENR offers the added advantage of being recyclable. Researchers have recently developed ENR that can achieve high performance properties through simultaneous crosslinking with dianhydride and an aromatic structure. This introduces dynamic ester bonds and rigid benzene rings into the crosslinked ENR structure. This alteration to the chemistry of the ENR confers high performance properties. Note that this particular type of high performance bioplastic is still in early stage development and may only be available through customized production services.

Common Processing Challenges in Injection molding of High Performance Bioplastics

Although within the sub topics above we have discussed some of the processing requirements for injection molding of high-performance bioplastics, injection molding of bioplastics in general poses some challenges that cuts across all the bioplastics types. These are discussed below.

Moisture Sensitivity

Bioplastics, in particular biodegradable biobased ones, tend to be more hydrophilic than conventional fossil derived synthetic plastics. They partly owe their biodegradability to this which is an advantage for environmental consideration but poses a processing challenge. Many bio-based polymers require an adequate drying stage before feeding into the injection molding machine. Moisture content should be reduced to around 0.02% to eliminate the possibility of hydrolytic degradation during processing.

Thermal Degradation

While the biodegradable high performance bioplastics discussed within this article tend to have relatively higher temperature tolerance, they are more prone to thermal degradation than conventional fossil based plastics. Bioplastics often possess narrower processing windows than conventional polymers. Excessive residence time or high barrel temperatures may cause degradation.

Warpage

Bioderived bioplastics like PHA that are fully synthesized by microbes can introduce microscopic levels of non uniformity. While polydispersity and chain length can be better controlled in chemical synthesis, it is more challenging to control how the microbed biosynthesize polymers, especially in the commercial case. This slight variation makes warping more likely in bioplastics therefore more measures need to be put in place to prevent such defects.
These bioplastics have less tolerance for uneven cooling or improper mold design which may result in warping of the part. Injection molding of high performance bioplastics still require optimized cooling systems and balanced wall thickness to eliminate the chances of a warped part.

Shrinkage

Biobase biodegradable plastics are more prone to shrinkage than conventional fossil based non biodegradable plastics. This is related to their different moisture absorption rate and heat distribution kinetics within the material. Different bioplastics exhibit varying shrinkage rates and shrinkage anisotropy. Threfore in designing molds for biobased biodegradable bioplastics the shrinkage must be adequately compensated for with consideration for the specific material.

Brittleness

Although high performance bioplastics that have been formulated for injection molding tend to have impact modifiers, plasticizers, or fiber reinforcements within their formulation to improve toughness, some bioplastics still remain relatively brittle. In some cases this is a compromise in order to retain other properties such as transparency or biodegradability.
This should be considered in the design of the mold cooling process and part ejection. The heat exchange process can be optimized to minimize brittleness of the final part and the ejection process can be optimally designed to evenly distribute and efficiently apply ejector force to prevent breakage of the part.

Future Trends

Research continues to expand the capabilities of high-performance bioplastics. Scientists are developing materials with greater heat resistance, improved impact strength, enhanced flame retardancy, and better recyclability.

Emerging technologies explore nanocomposite bioplastics reinforced with cellulose nanofibers, graphene, and other advanced fillers. Others are taking the approach of improving compatibility of blends and composites through modification such as substitution of pendant groups, copolymerization, crosslinking and acetylations. These are aimed towards achieving bioderived and/or biodegradable plastics with exceptional mechanical performance while maintaining reduced environmental impact.

Recently the European bioplastics funded BioSupPack project presented newly developed high performance PHA and PHB produced from brewry waste. This project brought together 18 top level stakeholder accross the supply chain. This suggests growing interest in further advancing commercialization of high perfromance PHA.

High perfromance bioplastics are currently premium price feedstock. However, as the industry sees growing investment in renewable feedstocks and bio-refineries, the is expected to lower production costs and expand the availability of engineering-grade bioplastics.

Conclusion

High performance bioplastics offer the promise of environmentally sustainable plastic product manufacturing without compromising on quality and performance. It is important that these materials are designed for manufacturability. Their processibility through injection molding significantly impacts their commercial success and practicality as this ensures they can be processed into diverse products efficiently using readily available and well established technology such as injection molding.
Currently even the best performing bioplastics are still limited by the processibility and performance barrier due to the inherent properties of these materials compared to fossil derived high performance plastics. Using specially formulated grades for injection molding and optimizing the injection molding process can significantly improve the performance of the part produced.

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By Ololade Olatunji
19 July, 2026