Role of Wood Fibers in Tuning Dynamic Rheology, Non-Isothermal Crystallization, and Microcellular Structure of Polypropylene Foams

A Critical Review on Wood-Based Polymer Composites: Processing, Properties, and Prospects

Waste recycling is one of the key aspects in current day studies to boost the country's circular economy. Recycling wood from construction and demolished structures and combining it with plastics forms wood-polymer composites (WPC) which have a very wide scope of usage. Such recycled composites have very low environmental impact in terms of abiotic potential, global warming potential, and greenhouse potential. Processing of WPCs can be easily done with predetermined strength values that correspond to its end application. Yet, the usage of conventional polymer composite manufacturing techniques such as injection molding and extrusion has very limited scope. Many rheological characterization techniques are being followed to evaluate the influence of formulation and process parameters over the quality of final WPCs. It will be very much interesting to carry out a review on the material formulation of WPCs and additives used. Manufacturing of wood composites can also be made by using bio-based adhesives such as lignin, tannin, and so on. Nuances in complete replacement of synthetic adhesives as bio-based adhesives are also discussed by various researchers which can be done only by complete understanding of formulating factors of bio-based adhesives. Wood composites play a significant role in many non-structural and structural applications such as construction, floorings, windows, and door panels. The current review focuses on the processing of WPCs along with additives such as wood flour and various properties of WPCs such as mechanical, structural, and morphological properties. Applications of wood-based composites in various sectors such as automotive, marine, defense, and structural applications are also highlighted in this review.

Unique Compatibilized Thermoplastic Elastomer with High Strength and Remarkable Ductility: Effect of Multiple Point Interactions within a Rubber-Plastic Blend

In the case of thermoplastic elastomers (TPEs) based on nonpolar polypropylene (PP) and polar rubbers, a small quantity of a third component known as the compatibilizer is added to maximize the compatibility between the incompatible blend components. Generally, one part of the compatibilizer reacts with the nonpolar PP phase and the other part of the compatibilizer reacts with the polar rubber phase, which in turn produces TPEs with useful properties. Till today, there have been no reports in the literature that examine the effect of a compatibilizer that can have multifaceted interactions with the incompatible blend components for the development of TPEs with unique properties. Accordingly, here, an ethylene-acrylic ester-maleic anhydride terpolymer (E-AE-MA-TP) has been used as the compatibilizer for the preparation of TPEs based on nonpolar isotactic polypropylene (i-PP) and polar epichlorohydrin rubber (ECR). The E-AE-MA-TP compatibilizer contains ethylene groups, acrylic groups, and anhydride/acid groups along its backbone, which act as the sites for establishing multifaceted interactions with both i-PP and ECR. The compatibilization efficiency of the E-AE-MA-TP compatibilizer has been analyzed by contact angle measurements, Fourier transform infrared (FTIR) spectroscopy, tensile stress-strain studies, mixing torque profiles, rheological studies, differential scanning calorimetry (DSC), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM) images. The particle size of the dispersed ECR domains in the i-PP matrix of the i-PP/ECR blend prominently decreases (∼90% reduction) by incorporation of a very low dosage (5 wt %) of the E-AE-MA-TP compatibilizer. The i-PP/ECR (40 wt %/60 wt %) blend containing 5 wt % compatibilizer displays outstanding mechanical properties (especially strain at break value (∼370%)), which are superior to the mechanical properties of several compatibilized TPEs (based on PP and polar rubbers) reported in the literature. The unique properties of TPEs based on i-PP and ECR in the presence of the E-AE-MA-TP compatibilizer is attributed to the efficacy of the E-AE-MA-TP compatibilizer to establish multifaceted interactions with both i-PP and ECR.

Fabrication of poly (lactic acid) foams using supercritical nitrogen

In this article, poly (lactic acid) (PLA) was foamed via batch foaming using supercritical nitrogen as a physical blowing agent by two methods, conventional foaming process (CFP) and low-temperature foaming process (LTFP). The fabrication processes, cell morphologies, thermal properties, crystallization behavior, and electrical resistance of resulted foams were studied to investigate the effect of foaming on these properties of PLA. It was found that the foams resulted from CFP method have micrometric cell sizes, while LTFP method led to nanometric cell structure and high cell density. Also scanning electron microscopy showed that the PLA foams have a heterogeneous cellular structure. The results showed that the foaming process increased the melting point and degree of crystallinity of PLA, which led to decrease in the electrical resistance of samples.