Four-ingredient blends of poly(lactic acid) with cottonseed oil and meal for biocomposite utilization

Authors: He, Zhongqi; Cheng, Huai; Ford, Catrina; Nam, Sunghyun; Fortier, Chanel; Santiago Cintron, Michael; Olanya, Modesto; Uknalis, Joseph

Submitted to: Macromol
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2024
Publication Date: 10/1/2024
Citation: He, Z., Cheng, H.N., Ford, C.V., Nam, S., Fortier, C., Santiago Cintron, M., Olanya, O.M., Uknalis, J. 2024. Four-ingredient blends of poly(lactic acid) with cottonseed oil and meal for biocomposite utilization. Macromol. 4(4): 708-722. https://doi.org/10.3390/macromol4040042.
DOI: https://doi.org/10.3390/macromol4040042

Interpretive Summary: This study demonstrated that washed cottonseed meal (WCSM) and cottonseed oil (CSO) could be incorporated into poly(lactic acid) (PLA) matrix to make four-component biocomposite materials using a melt blending method. While WCSM served as a filler in the composite product, CSO served as the compatibilizer function, replacing the common compatibilizer poly(ethylene glycol) (PEG). scanning electron microscopic images confirmed the homogenous, though not perfect, morphology of the two sets of composites (i.e., CSO series and PEG series). Mechanical, water absorption and thermogravimetric data showed similar or minor differences between CSO biocomposite products and PEG bio-composites, which implied the suitability of CSO as a compatibilizer of WCSM within PLA for the development of cotton byproduct-based biocomposites by the melt blending process. These biocomposite products may be used for sustainable agricultural practices (e.g., degradable plant containers, and mulch films). Future work should be focused on improving their mechanical strength through green chemistry modification strategies and evaluating the biodegradability of these biocomposites by soil burial experiments.

Technical Abstract: Development and characterization of agricultural byproduct-based composites are important part of green and sustainable chemistry. In this work, two sets of four-ingredient biocomposite products were formulated with melt blending method. The first set (CSO series) was made with poly(lactic acid) (PLA) as the major matrix, washed cottonseed meal (WCSM) as a filler, cottonseed oil (CSO) as a compatibilizer, and glycerol (GLY) as a plasticizer. The second set (PEG series) was made by substituting CSO with another compatibilizer poly(ethylene glycol) (PEG). Morphological analysis showed the homogenous dispersion of cottonseed byproducts into PLA matrix to some extent. The mechanical strengths of PEG composites were slightly higher than those of CSO series, but affected by the ratios of PLA-PEG (or CSO). Generally, the tensile strengths were in the range of 0.5-1.5 MPa, which indicate its suitability for low-strength biodegradable plant container development. Both series of biocomposites had lower water absorption during water soaking test. Thermogravimetric analysis revealed higher thermal stability of CSO composites than PEG composites. Functional group analysis of sample and simulation by Fourier transform infrared spectra confirmed the chemical interactions of PLA with WCSM, PEG and probably PEG com-ponents in the biocomposite products. CSO was most likely subjected to physical blending into the biocomposites. This work shows the feasibility of incorporating cottonseed WCSM and CSO into PLA composite for sustainable agricultural applications.