Grafted Lactic Acid Oligomers on Lignocellulosic Filler towards Biocomposites

Lactic acid oligomers (OLAs) were in situ synthesized from lactic acid (LAc) and grafted onto chokeberry pomace (CP) particleboards by direct condensation. Biocomposites of poly (lactic acid) (PLA) and modified/unmodified CP particles containing different size fractions were obtained using a mini-extruder. To confirm the results of the grafting process, the FTIR spectra of filler particles were obtained. Performing 1HNMR spectroscopy allowed us to determine the chemical structure of synthesized OLAs. The thermal degradation of modified CP and biocomposites were studied using TGA, and the thermal characteristics of biocomposites were investigated using DSC. In order to analyse the adhesion between filler particles and PLA in biocomposites, SEM images of brittle fracture surfaces were registered. The mechanical properties of biocomposites were studied using a tensile testing machine. FTIR and 1HNMR analysis confirmed the successful grafting process of OLAs. The modified filler particles exhibited a better connection with hydrophobic PLA matrix alongside improved mechanical properties than the biocomposites with unmodified filler particles. Moreover, a DSC analysis of the biocomposites with modified CP showed a reduction in glass temperature on average by 9 °C compared to neat PLA. It confirms the plasticizing effect of grafted and ungrafted OLAs. The results are promising, and can contribute to increasing the use of agri-food lignocellulosic residue in manufacturing biodegradable packaging.

Effects of Various Types of Modified Nanoclay on The Physical, Mechanical, and Viscoelastic Characteristics of Lignocellulosic Filler-Reinforced PVC Composites

The objective of this research was to comprehensively compare the effects of two different types of nanoclay, namely layered double hydroxide (LDH) and halloysite nanotube (HNT) on the physical, mechanical, and dynamic mechanical properties of compression-molded composite panels fabricated from wood flour (WF) and polyvinyl chloride (PVC). To achieve the desired properties in the composites, the clay nanoparticles were modified with surfactant (mLDH and mHNT) before usage. The results showed that the composite specimens with mLDH exhibited higher tensile and flexural properties (strength and moduli) than with mHNT at low content. However, at high content, the composite specimens with mHNT presented greater hydrophobicity. The DMTA results indicated that the composite specimens with mLDH demonstrated better molecular restriction and larger storage modulus than with mHNT. Besides, the loss-tangent (tan δ) peak was shifted to a higher temperature for the samples including both mLDH and mHNT than without ones. Morphological observations showed that the nanoparticles were predominantly dispersed uniformly within the polymer matrix. Overall, it is found that the addition of 3 phc mLDH clay was the most effective in the composite formulation; it has significantly enhanced the properties of the wood-plastic composites.

Effects of filler type and content on the mechanical, morphological, and thermal properties of waste casting polyamide 6 (W-PA6G)-based wood plastic composites

Cast polyamide 6 (PA6G), trade name Castamide, is a semi-crystalline polymer widely used in the engineering plastics industry. There is a need to recycle valuable waste (W)-PA6G generated during part manufacturing of this polymer (approximately 30%). This study attempts to utilize W-PA6G in the manufacture of wood-plastic composites as a polymeric matrix. The effect of lignocellulosic filler type (FT) and filler content (FC) on the mechanical, morphological, and thermal properties of W-PA6G-based composites were investigated. During manufacturing, N-butyl benzene sulfonamide (N-BBSA) and lithium chloride (LiCl) were utilized as a plasticizer and a melt temperature-lowering salt, respectively. The rice husk (RH) and Uludağ fir wood flour (WF) filled W-PA6G-based composites were successfully manufactured using a combination of extrusion and injection molding. Compared to RH filled composites, WF filled composites provided better tensile and flexural properties (both strength and modulus) at 20% and 30% filler contents. Morphological study showed the nonhomogeneous distribution of fillers in the polymeric matrix. Lignocellulosic filler resulted in reduced melting temperature and crystallinity of W-PA6G-based composites. This reduction was more pronounced in RH filled composites.

Properties of Chemically Modified (Selected Silanes) Lignocellulosic Filler and Its Application in Natural Rubber Biocomposites

This article concerns the functional properties of elastomeric composites reinforced with modified lignocellulosic material obtained from cereal straw. The aim of the research was to acquire new knowledge on the effectiveness of cereal straw modification methods in multifunctional properties, while reducing the flammability of newly designed elastomeric materials made of natural rubber. The article deals with investigating and explaining dependencies that affect the performance and processing properties of polymer biocomposites containing modified cereal straw. Three different silanes were used to modify the lignocellulosic filler: n-Propyltriethoxysilane, Vinyltriethoxysilane, and 3,3′-Tetrathiobis(propyl-triethoxysilane). The influence of the conducted modifications on the morphology and structure of straw particles was investigated using a scanning electron microscope, contact angle measurements, and thermogravimetric analysis technique. The increase in hydrophobicity and thermal stability of natural fibers was confirmed. In turn, the impact of silanization on the properties of filled composites was determined on the basis of rheometric characteristics and cross-linking density, static mechanical properties, tear resistance, thermal stability, and flammability tests. Noteworthy was the improvement of the mechanical strength of biocomposites and their resistance to burning. Correlations affecting the structure, morphology, dispersion, and properties of produced composites can facilitate the indication of a further research path in the field of development of new elastomeric biomaterials.

Recent advances in compatibilization strategies of wood-polymer composites by isocyanates

Wood-polymer composites technologies are gaining more and more attention in the scientific community, positively affecting the increase in their industrial applications, for example, automotive, building, 3D printing, etc. Many research works are focused on the improvement in matrix–lignocellulosic filler interactions to produce highly filled composites with satisfying performance properties. In this field of research, using isocyanates due to their versatile structure and functionality seems to be a very promising approach. This paper aims at reporting on recent advances in compatibilization strategies of wood-polymer composites by isocyanates. Particular attention is focused on the correlation between isocyanate structure, as well as modification conditions on the matrix–lignocellulosic filler interactions and their impact on the structure–property relationships of wood-polymer composites. Furthermore, limitations and future research trends related to applications of isocyanate to wood-polymer composites technologies are also discussed.

Preparation of thermoplastic polyurethane-based biocomposites through injection molding: Effect of the filler type and content

The effects of lignocellulosic filler type and filler loading levels were investigated relative to selected properties of thermoplastic polyurethane (TPU)-based composites. Teak wood (TK), rice husks (RH), and microcrystalline cellulose (MCC) were used as lignocellulosic fillers at 15 wt% and 30 wt% filler loading levels. Test specimens were manufactured using both extrusion and injection molding, except for abrasion resistance samples that were manufactured using a compression molding process. Density, tensile, flexural, and impact properties, and hardness and abrasion resistance values, of the specimens were determined. The composites’ morphology was studied using scanning electron microscopy analysis; results showed all filler types and filler loading levels were affected by the TPU’s density and mechanical properties. The TPU composites were successfully produced using TK, RH, and MCC as lignocellulosic fillers. Regardless of filler type, addition of 15% filler to TPU yielded excellent mechanical properties. With 30% MCC filler, composite properties increased due to their higher surface area, while properties of TK- and RH-containing specimens were, at 30%, reduced. There was a proportional correlation between hardness and modulus, with both increasing with a rising filler loading level. Abrasion resistance of TPU decreased with the presence of filler. Regardless of filler type, abrasion resistance continued to drop at higher filler loading levels. Scanning electron micrographs showed better MCC distribution in the TPU matrix.

Horsetail (Equisetum Arvense) as a Functional Filler for Natural Rubber Biocomposites

Over the past decades, increased scientific and research activity has been observed in the development of new, innovative materials for various end uses. This is mainly due to the growing ecological, environmental, and material awareness of many industries and societies. Equisteum arvense-horsetail is a plant that has demonstrated its properties in pharmacological and clinical aspects as well as in vitro and in vivo biological activity. This article presents a new method of using horsetail as a natural, lignocellulosic filler for a natural rubber matrix. In-depth characteristics of the applied bio-additive were prepared based on several research techniques and methods such as ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-RAY spectroscopy, thermogravimetric analysis, and flame atomic absorption spectroscopy. Elastomer composites were prepared as a function of horsetail content. Then, an analysis of their main functional properties was performed, including mechanical properties and susceptibility to accelerated aging processes such as thermo-oxidative, ultraviolet radiation, and weathering. The research emphasizes the significant value of horsetail in its new role—as an active filler of elastomer biocomposites. The obtained results confirmed that horsetail is lignocellulosic material thermally stable up to 180 °C. Horsetail is an active filler to natural rubber, positively affecting mechanical strength. Due to the presence of flavonoids and phenolic acids in horsetail, it can be used as a polymer anti-aging agent.

Development and Characterization of Sustainable Composites from Bacterial Polyester Poly(3-Hydroxybutyrate-co-3-hydroxyhexanoate) and Almond Shell Flour by Reactive Extrusion with Oligomers of Lactic Acid

Eco-efficient Wood Plastic Composites (WPCs) have been obtained using poly(hydroxybutyrate-co-hexanoate) (PHBH) as the polymer matrix, and almond shell flour (ASF), a by-product from the agro-food industry, as filler/reinforcement. These WPCs were prepared with different amounts of lignocellulosic fillers (wt %), namely 10, 20 and 30. The mechanical characterization of these WPCs showed an important increase in their stiffness with increasing the wt % ASF content. In addition, lower tensile strength and impact strength were obtained. The field emission scanning electron microscopy (FESEM) study revealed the lack of continuity and poor adhesion among the PHBH-ASF interface. Even with the only addition of 10 wt % ASF, these green composites become highly brittle. Nevertheless, for real applications, the WPC with 30 wt % ASF is the most attracting material since it contributes to lowering the overall cost of the WPC and can be manufactured by injection moulding, but its properties are really compromised due to the lack of compatibility between the hydrophobic PHBH matrix and the hydrophilic lignocellulosic filler. To minimize this phenomenon, 10 and 20 phr (weight parts of OLA-Oligomeric Lactic Acid per one hundred weight parts of PHBH) were added to PHBH/ASF (30 wt % ASF) composites. Differential scanning calorimetry (DSC) suggested poor plasticization effect of OLA on PHBH-ASF composites. Nevertheless, the most important property OLA can provide to PHBH/ASF composites is somewhat compatibilization since some mechanical ductile properties are improved with OLA addition. The study by thermomechanical analysis (TMA), confirmed the increase of the coefficient of linear thermal expansion (CLTE) with increasing OLA content. The dynamic mechanical characterization (DTMA), revealed higher storage modulus, E’, with increasing ASF. Moreover, DTMA results confirmed poor plasticization of OLA on PHBH-ASF (30 wt % ASF) composites, but interesting compatibilization effects.

Effect of Almond Shell Waste on Physicochemical Properties of Polyester-Based Biocomposites

Polyester-based biocomposites containing INZEA F2® biopolymer and almond shell powder (ASP) at 10 and 25 wt % contents with and without two different compatibilizers, maleinized linseed oil and Joncryl ADR 4400®, were prepared by melt blending in an extruder, followed by injection molding. The effect of fine (125–250 m) and coarse (500–1000 m) milling sizes of ASP was also evaluated. An improvement in elastic modulus was observed with the addition of< both fine and coarse ASP at 25 wt %. The addition of maleinized linseed oil and Joncryl ADR 4400 produced some compatibilizing effect at low filler contents while biocomposites with a higher amount of ASP still presented some gaps at the interface by field emission scanning electron microscopy. Some decrease in thermal stability was shown which was related to the relatively low thermal stability and disintegration of the lignocellulosic filler. The added modifiers provided some enhanced thermal resistance to the final biocomposites. Thermal analysis by differential scanning calorimetry and thermogravimetric analysis suggested the presence of two different polyesters in the polymer matrix, with one of them showing full disintegration after 28 and 90 days for biocomposites containing 25 and 10 wt %, respectively, under composting conditions. The developed biocomposites have been shown to be potential polyester-based matrices for use as compostable materials at high filler contents.