Chemical composition, crystallinity, and thermal degradation of bleached and unbleached kenaf bast (Hibiscus cannabinus) pulp and nanofibers

Kenaf (Hibiscus cannabinus) nanofibers were isolated from unbleached and bleached pulp by a combination of chemical and mechanical treatments. The chemical methods were based on NaOH-AQ (anthraquinone) and three-stage bleaching (DEpD) processes, whereas the mechanical techniques involved refining, cryo-crushing, and high-pressure homogenization. The size and morphology of the obtained fibers were characterized by environmental scanning electron microscopy (ESEM) and transmission electron microscopy (TEM), and the studies showed that the isolated nanofibers from unbleached and bleached pulp had diameters between 10-90 nm, while their length was in the micrometer range. Fourier transform infrared (FTIR) spectroscopy demonstrated that the content of lignin and hemicellulose decreased in the pulping process and that lignin was almost completely removed during bleaching. Moreover, thermogravimetric analysis (TGA) indicated that both pulp types as well as the nanofibers displayed a superior thermal stability as compared to the raw kenaf. Finally, X-ray analyses showed that the chemo-mechanical treatments altered the crystallinity of the pulp and the nanofibers: the bleached pulp had a higher crystallinity than its unbleached counterpart, and the bleached nanofibers presented the highest crystallinity of all the investigated materials

Sustainable polymers

peer reviewedSustainable polymers are materials derived from renewable, recycled and waste carbon resources and their combinations, which at the end of life can be recycled, biodegraded or composted. Sustainable polymers also exhibit reduced environmental impact throughout their life cycle. This Primer presents an overview of the research in and potential of sustainable polymers, with a focus on their life cycle, synthetic routes from renewable carbon feedstocks, production, material characterization, applications, end of life, data reproducibility and limitations faced, and provides a brief outlook. The Primer also briefly covers other carbon feedstocks such as carbon dioxide and wastes, including agricultural and woody residues. Although still in their infancy, new sustainable polymers are already finding applications in packaging, automotive parts and 3D printing. This Primer also discusses the headwinds facing the adoption of sustainable polymers, including complexities of recycling and composting, manufacturing scale-up, data reproducibility, deposition and potential solutions. Development of sustainable polymers will accelerate the age of sustainable polymers and create a truly circular economy for plastics by reducing production and use of virgin plastics from finite resources

Super Toughened Poly(lactic acid)-Based Ternary Blends via Enhancing Interfacial Compatibility

Novel super toughened bioplastics are developed through controlled reactive extrusion processing, using a very low content of modifier, truly a new discovery in the biodegradable plastics area. The super toughened polylactide (PLA) blend showing a notched impact strength of ∼1000 J/m with hinge break behavior is achieved at a designed blending ratio of PLA, poly­(butylene succinate) (PBS), and poly­(butylene adipate-co-terephthalate) (PBAT), using less than 0.5 phr peroxide modifier. The impact strength of the resulting blend is approximately 10 times that of the blend with the same composition without a modifier and ∼3000% more than that of pure PLA. Interfacial compatibilization among the three biodegradable plastics took place during the melt extrusion process in the presence of a controlled amount of initiator, which is confirmed by scanning electron microscopy and rheology analysis. The synergistic effect of strong interfacial adhesion among the three blending components, the decreased particle size of the most toughened component, PBAT, to ∼200 nm, and its uniform distribution in the blend morphology result in the super tough biobased material. One of the key fundamental findings through the in situ rheology study depicts that the radical reaction initiated by peroxide occurs mainly between PBS and PBAT and not with PLA. Thus, the cross-linking degree can be controlled by adjusting renewable sourced PLA contents in the ternary blend during reactive extrusion processing. The newly engineered super toughened PLA with high stiffness and high melt elasticity modulus could reasonably serve as a promising alternative to traditional petroleum plastics, where high biobased content and biodegradability are required in diverse sustainable packaging uses

Alkali and Peroxide Bleach Treatments on Spring Harvested Switchgrass for Potential Composite Application

Natural fibers are desirable in composite applications for their sustainability. However, improving upon the interfacial adhesion between the fiber and matrix is a major challenge. Chemical surface modification is a method used to improve compatibility of the fiber by exposing or adding functionalities to the surface, and removing non-cellulosic components in order to enhance mechanical and thermal properties. Switchgrass, an abundant natural fiber, has potential for use as a reinforcing material in composite applications. Surface modifications were conducted on switchgrass via alkali and peroxide bleaching treatments in order to remove surface impurities and create a rougher surface, as observed in scanning electron micrographs. Fourier transform infrared spectroscopy and compositional analysis showed that non-cellulosic components were reduced following the alkali and bleach treatments. Reduction of hemicellulose and lignin improved thermal stability by increasing the onset temperature of degradation from 258 °C to 289 and 281 °C for alkali and bleach treatments, respectively. The crystallinity index (CI) of untreated and treated fibers was calculated from x-ray diffraction analyses. An increase of 48% and 38% for the alkali and bleach treated fibers, respectively, was seen in the CI, compared to the untreated switchgrass. The surface of switchgrass was successfully modified using alkali and peroxide bleach treatments for composite applications

Biodegradable compatibilized polymer blends for packaging applications A literature review

The majority of materials used for short-term and disposable packaging application are non-biodegradable which are not satisfying the demands in environmental safety and sustainability. Biodegradable polymers are an alternative for these non-biodegradable materials. The biodegradable polymeric materials can degrade in a reasonable time period without causing environmental problems. However, biodegradable polymers possess some limitations such as comparatively high cost, insufficient mechanical performances, and inferior thermal stability to extend their widespread application in packaging industry. To overcome these limitations, one of the most commonly used strategies is melt blending of dissimilar biodegradable polymers. Unfortunately, most of the biodegradable polymer blends exhibit insufficient performance because they are thermodynamically immiscible as well as exhibit poor compatibility between the blended components. It has been established that the compatibilization is a well-known strategy to improve the performances of the immiscible biodegradable polymer blends by enhancing the adhesion between the phases. As a result, recent studies focus on various compatibilizers to enhance the performances of the resulting biodegradable polymer blends. This review summarizes the recent developments on a variety of biodegradable polymer blends compatibilized by melt processing with a main focus of ex situ and in situ compatibilization strategies. (C) 2017 Wiley Periodicals, Inc