Interfacial properties of highly oriented coextruded polypropylene tapes for the creation of recyclable all-polypropylene composites

Approaches in Sustainable, Biobased Multilayer Packaging Solutions

The depletion of fossil resources and the growing demand for plastic waste reduction has put industries and academic researchers under pressure to develop increasingly sustainable packaging solutions that are both functional and circularly designed. In this review, we provide an overview of the fundamentals and recent advances in biobased packaging materials, including new materials and techniques for their modification as well as their end-of-life scenarios. We also discuss the composition and modification of biobased films and multilayer structures, with particular attention to readily available drop-in solutions, as well as coating techniques. Moreover, we discuss end-of-life factors, including sorting systems, detection methods, composting options, and recycling and upcycling possibilities. Finally, regulatory aspects are pointed out for each application scenario and end-of-life option. Moreover, we discuss the human factor in terms of consumer perception and acceptance of upcycling.

Modification of self-reinforced composites (SRCs) via film stacking process

This work presents the mechanical behavior of self-reinforced composites (SRCs) manufactured and modified via film stacking. For modification, interleaved films made of polypropylene (PP), a thermoplastic elastomer and a polyolefin engage were combined in different ways to induce the elastic modifier into the matrix material. The content of modifier was also varied in two ways. First, the films were produced out of a single material and second out of a compound. So, the same content of modifier was implemented in two different ways. It is shown that, in case of this research, only the kind of modifier and the content but not the way of implementation are responsible for the mechanical behavior of SRCs. It is shown that the modification can adjust the tensile strength, tensile stiffness and impact properties in a broad range. It is also shown that different mechanical properties of the composite can be predicted by a regression model that uses the Shore A hardness and the content of modifier.

Development of Polypropylene-Based Single-Polymer Composites With Blends of Amorphous Poly-Alpha-Olefin and Random Polypropylene Copolymer

We developed polypropylene-based single-polymer composites (PP-SPC) with blends of amorphous poly-alpha-olefin (APAO) and random polypropylene copolymer (rPP) as matrix material and polypropylene (PP) woven fabric as reinforcement. Our goal was to utilize the lower melting temperature of APAO/rPP blends to increase the consolidation of the composites and decrease the heat load of the PP reinforcement. We produced the composites by film-stacking at 160 °C, and characterized the composites with density, peel, static tensile and dynamic falling weight impact tests, and by scanning electron microscopy. The results indicate that consolidation can be enhanced by increasing the APAO content of the matrix. We found that the APAO content of 50% is optimal for tensile properties. With increasing APAO content, the perforation energy decreased, but even the well-consolidated composites showed very high perforation energy. In the case of a pure APAO matrix, fiber content can be increased up to 80 wt% without a severe loss of consolidation, resulting in good tensile properties. The PP-SPCs developed possessed excellent mechanical properties, and well-consolidated composites can be produced with APAO/rPP blends as a matrix with high fiber content.

Experimental study on influence of molding parameters on self-reinforcement characteristics of polymer co-injection molding

In this paper, self-reinforced samples with different mechanical properties were obtained by adjusting the molding parameters by co-injection molding technology, and the micro-morphology of these samples was observed. Then, using structured statistical methods, the analysis of variance and response surface methodology were used to study the effects of various molding variables on the morphology and properties of the materials, and to determine the most important molding variables and their interaction relationships. Finally, the associated experimental data were fitted by the least square minimization program, and the parameters in the fitting equation were dimensionless to obtain the correlative dimensionless equation. The purpose was to establish the mechanism model of the influence of the molding parameters on the co-injection self-reinforced sample and to objectively analyze its mechanism. It was found that the melt temperature is the most important factor affecting the morphology and mechanical properties. The highly oriented skin thickness is the most important factor in determining the tensile properties of the sample. The change in crystallinity is the most important factor in relation to the elastic modulus. Through the establishment of the relevant dimensionless equations, the theoretical study on the tensile strength and elastic modulus of the co-injection self-reinforced samples of the molding parameters was preliminarily realized.

Tailoring Hydrocarbon Polymers and All-Hydrocarbon Composites for Circular Economy

The world population will rapidly grow from 7 to 9 billion by 2050 and this will parallel a surging annual plastics consumption from today's 350 million tons to well beyond 1 billion tons. The switch from a linear economy with its throwaway culture to a circular economy with efficient reuse of waste plastics is therefore mandatory. Hydrocarbon polymers, accounting for more than half the world's plastics production, enable closed-loop recycling and effective product-stewardship systems. High-molar-mass hydrocarbons serve as highly versatile, cost-, resource-, eco- and energy-efficient, durable lightweight materials produced by solvent-free, environmentally benign catalytic olefin polymerization. Nanophase separation and alignment of unentangled hydrocarbon polymers afford 100% recyclable self-reinforcing all-hydrocarbon composites without requiring the addition of either alien fibers or hazardous nanoparticles. Recycling of durable hydrocarbons is far superior to biodegradation. The facile thermal degradation enables liquefaction and quantitative recovery of low molar mass hydrocarbon oil and gas. Teamed up with biomass-to-liquid and carbon dioxide-to-fuel conversions, powered by renewable energy, waste hydrocarbons serve as renewable hydrocarbon feedstocks for the synthesis of high molar mass hydrocarbon materials. Herein, an overview is given on how innovations in catalyst and process technology enable tailoring of advanced recyclable hydrocarbon materials meeting the needs of sustainable development and a circular economy.

All-aramid composites by partial fiber dissolution

The area of self-reinforced polymer composites is one of the fastest growing areas in engineering polymers, but until now these materials have been mainly developed on the basis of thermoplastic fibers of moderate performance. In this work, we report on a new type of self-reinforced composites based on high-performance aramid fibers to produce an "all-aramid" composite by applying a surface-dissolution method to fuse poly(p-phenylene terephthalamide) (PPTA) fibers together. After immersion in concentrated (95%) sulphuric acid (H(2)SO(4)) for a selected period of time, partially dissolved fiber surfaces were converted into a PPTA interphase or matrix phase. Following extraction of H(2)SO(4) and drying, a consolidated all-aramid composite was formed. The structure, mechanical- and thermal properties of these single-polymer composites were investigated. Optimum processing conditions resulted in unidirectional composites of high reinforcement content (approximately 75 vol %) and good interfacial bonding. The all-aramid composites featured a Young's modulus of approximately 65 GPa at room temperature, and a tensile strength of 1.4 GPa, which are comparable with or exceed the corresponding values of conventional aramid/epoxy composites. However, since fiber, matrix and interphase in all-aramid composites are based on the same high-temperature resistant PPTA polymer, a high modulus of approximately 50 GPa was maintained up to 250 degrees C, demonstrating the potential of these materials for high-temperature applications.