Effect of Mineral Fillers on the Mechanical Properties of Commercially Available Biodegradable Polymers

Abstract

In the successful transition towards a circular materials economy, the implementation of biobased and biodegradable plastics is a major prerequisite. To prevent the accumulation of plastic material in the open environment, plastic products should be both recyclable and biodegradable. Research and development actions in the past few decades have led to the commercial availability of a number of polymers that fulfil both end-of-life routes. However, these biobased and biodegradable polymers typically have mechanical properties that are not on par with the non-biodegradable plastic products they intend to replace. This can be improved using particulate mineral fillers such as talc, calcium carbonate, kaolin, and mica. This study shows that composites thereof with polybutylene succinate (PBS), polyhydroxybutyrate-hexanoate (PHBH), polybutylene succinate adipate (PBSA), and polybutylene adipate terephthalate (PBAT) as matrix polymers result in plastic materials with mechanical properties ranging from tough elastic towards strong and rigid. It is demonstrated that the balance between the Young’s modulus and the impact resistance for this set of polymer composites is subtle, but a select number of investigated compositions yield a combination of industrially relevant mechanical characteristics. Finally, it is shown that the inclusion of mineral fillers into biodegradable polymers does not negate the microbial disintegration of these polymers, although the nature of the filler does affect the biodegradation rate of the matrix polymer.

Extrusion and Injection Molding of Poly(3-Hydroxybutyrate-co-3-Hydroxyhexanoate) (PHBHHx): Influence of Processing Conditions on Mechanical Properties and Microstructure

“…An explanation for a decrease in tensile strength at elevated process temperatures could be found in the fact that PHBHHx twin-screw extrusion and injection molding at high temperatures can lead to a reduction in molecular weight due to thermal degradation [18]. Random chain scission has been reported as the degradation mechanism causing a rapid decrease in molecular weight of PHAs during thermal treatment [46].…”

“…PHBV and PHBHHx display slower crystallization rates than the homopolymer PHB because the co-monomer units are excluded from the PHB lattice during crystallization from the melt, which can be a challenge for efficient processing of PHBHHx, especially in methods with high cooling rates like injection molding [15,16]. Despite the rise in attempts to further improve both thermal and mechanical properties of PHAs with or without processing aids [17][18][19][20], current research regarding PHA processing and compound fabrication mostly relates to batch processing methodologies without the involvement of high temperatures and/or high shear rates, like solution casting [21][22][23], compression molding [24,25], or spinning techniques [26][27][28]. While these techniques are practical for use in a lab-scale context, they often have limited applicability on larger scales.…”

Materials Informatics Approach Using Domain Modelling For Exploring Structure-Property Relationships Of Polymers

“…These materials clustered in the following way i.e., navy blue circle symbols are polyethylene terephthalate (PET), light blue circle symbols are polyethylene (PE), and the clusters of these polymer materials are on the top, blue triangle symbols are poly(butylene adipate-co-terephthalate) (PBAT), light pink circle symbols are polylactic acid (PLA), light green circle symbols are poly(hexano-6lactam) (nylon), and the clusters of these polymer materials are on the bottom left, black cross symbols are polybutylene succinate (PBS), orange diamond symbols are poly(butylene succinate-co-butylene adipate) (PBSA), and red square symbols are PCL, and the clusters of these polymer materials are found to exist solidly in the lower right corner, respectively. These clusters formed two groups: high heat resistant polymers with many rigid domain components, and low heat resistant polymers with many mobile domain components 43,44 . The results of thermal analysis for PET, PE, PBAT, PLA, nylon, PBS, PBSA, and PCL were consistent with their characteristics shown above (Figure S4, Table S3).…”

Are Natural-Based Composites Sustainable?

“…Cotana states that residual lignin from bioethanol production using Arundo donax as raw material is suitable to be used as filler in composites, as composition and thermal degradation profiles look favorable [ 56 ]. Lignin has been successfully used for the reinforcement of several matrices (PP, PE, PLA or PVA among others) [ 34 , 57 , 58 ], with applications in energy storage devices, adhesives or biosensing [ 32 ]. Moreover, Vaidya [ 59 ] has used lignin from a saccharification process in a biorefinery as a reinforcement of a PHB matrix, obtaining a composite suitable to be 3D-printed, reducing the warpage observed for neat PHB printed parts.…”

“…Moreover, lignin has also been investigated as a sustainable precursor to obtain carbon fibers [ 60 ]. Talc, mica or calcium carbonate have also been used as fillers of biobased biodegradable matrices (such as polybutylene succinate, PBS, or polybutylene adipate terephthalate, PBAT), increasing their mechanical properties and reaching values similar to polyolefins, while keeping their biodegradable character [ 57 ].…”