Substantial Effect of Water on Radical Melt Crosslinking and Rheological Properties of Poly(ε-Caprolactone)

One-step reactive melt processing (REx) via radical reactions was evaluated with the aim of improving the rheological properties of poly(ε-caprolactone) (PCL). In particular, a water-assisted REx was designed under the hypothesis of increasing crosslinking efficiency with water as a low viscous medium in comparison with a slower PCL macroradicals diffusion in the melt state. To assess the effect of dry vs. water-assisted REx on PCL, its structural, thermo-mechanical and rheological properties were investigated. Water-assisted REx resulted in increased PCL gel fraction compared to dry REx (from 1–34%), proving the rationale under the formulated hypothesis. From dynamic mechanical analysis and tensile tests, the crosslink did not significantly affect the PCL mechanical performance. Dynamic rheological measurements showed that higher PCL viscosity was reached with increasing branching/crosslinking and the typical PCL Newtonian behavior was shifting towards a progressively more pronounced shear thinning. A complete transition from viscous- to solid-like PCL melt behavior was recorded, demonstrating that higher melt elasticity can be obtained as a function of gel content by controlled REx. Improvement in rheological properties offers the possibility of broadening PCL melt processability without hindering its recycling by melt processing.

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Substantial Effect of Water on Radical Melt Crosslinking and Rheological Properties of Poly(Ε-Caprolactone)

10.20944/preprints202101.0451.v1 ◽

2021 ◽

Author(s):

Angelica Avella ◽

Rosica Mincheva ◽

Jean-Marie Raquez ◽

Giada Lo Re

Keyword(s):

Rheological Properties ◽

Mechanical Performance ◽

Radical Reaction ◽

Tensile Tests ◽

Viscous Medium ◽

Mechanical Analysis ◽

Substantial Effect ◽

Melt Processing ◽

One Step ◽

Reactive Melt

One-step reactive melt processing (REx) via radical reaction was evaluated with the aim of improving the rheological properties of poly(ε-caprolactone) (PCL). In particular, a water-assisted REx was designed under the hypothesis of increasing crosslinking efficiency with water as a low viscous medium in comparison with a slower PCL macroradicals diffusion in the melt state. To assess the effect of dry vs. water-assisted REx on PCL, its structural, thermo-mechanical and rheological properties were investigated. Water-assisted REx resulted in increased PCL gel fraction compared to dry REx (from 1 to 34 %), proving the rationale under the formulated hypothesis. From dynamic mechanical analysis and tensile tests, the crosslink did not significantly affect the PCL mechanical performance. Dynamic rheological measurements showed that higher PCL viscosity was reached with increasing branching/crosslinking and the typical PCL Newtonian behavior was shifting towards a progressively more pronounced shear thinning. A complete transition from viscous- to solid-like PCL melt behavior was recorded, demonstrating that higher melt elasticity can be obtained as a function of gel content by controlled REx. Improvement in rheological properties offers the possibility of broadening PCL melt processability without hindering its recycling by melt processing.

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Study of Nano-Mechanical Performance of Pretreated Natural Fiber in LDPE Composite for Packaging Applications

Materials ◽

10.3390/ma13214977 ◽

2020 ◽

Vol 13 (21) ◽

pp. 4977

Author(s):

Muhammad Sulaiman ◽

Tanveer Iqbal ◽

Saima Yasin ◽

Hamayoun Mahmood ◽

Ahmad Shakeel

Keyword(s):

Elastic Modulus ◽

Creep Rate ◽

Mechanical Performance ◽

Natural Fiber ◽

Choline Chloride ◽

Peak Load ◽

Substantial Effect ◽

Melt Processing ◽

Creep Properties ◽

Composite Samples

In this work, the effects of chemical pretreatment and different fiber loadings on mechanical properties of the composites at the sub-micron scale were studied through nanoindentation. The composites were prepared by incorporating choline chloride (ChCl) pretreated rice husk waste (RHW) in low-density polyethylene (LDPE) using melt processing, followed by a thermal press technique. Nanoindentation experiments with quasi continuous stiffness mode (QCSM) were performed on the surface of produced composites with varying content of pretreated RHW (i.e., 10, 15, and 20 wt.%). Elastic modulus, hardness, and creep properties of fabricated composites were measured as a function of contact depth. The results confirmed the appreciable changes in hardness, elastic modulus, and creep rate of the composites. Compliance curves indicated that the composite having 20 wt.% of pretreated RHW loading was harder compared to that of the pure LDPE and other composite samples. The values of elastic modulus and hardness of the composite containing 20 wt.% pretreated RHW were increased by 4.1% and 24% as compared to that of the pure LDPE, respectively. The creep rate of 42.65 nm/s and change in depth of 650.42 nm were also noted for the composite with RHW loading of 20 wt.%, which showed the substantial effect of holding time at an applied peak load of 100 mN. We believe that the developed composite could be a promising biodegradable packaging material due to its good tribo-mechanical performance.

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Influence of preparation methods on the performance of cold-mixed epoxy bitumen

Materials and Structures ◽

10.1617/s11527-021-01669-y ◽

2021 ◽

Vol 54 (2) ◽

Author(s):

Quan Liu ◽

Chonghui Wang ◽

Zeyu Zhang ◽

Cong Du ◽

Pengfei Liu ◽

...

Keyword(s):

Mechanical Performance ◽

Preparation Method ◽

Tensile Tests ◽

Mechanical Analysis ◽

Curing Temperature ◽

Steel Bridge ◽

Preparation Methods ◽

Two Component ◽

Direct Tensile ◽

Thermal Stability Of

AbstractCold-mixed epoxy bitumen (CEB) has been presented as an eco-friendly paving material used for steel bridge deck pavements. This study performed an investigation on three preparation methods of CEBs, which includes one kind of three-component and two kinds of two-component methods. The curing process was characterized through the viscosity measurement. Meanwhile, the microstructure of CEBs was observed using fluorescence microscopy. Mechanical properties of CEBs prepared with different methods were characterized by employing direct tensile tests and dynamic mechanical analysis (DMA). Finally, thermogravimetric analysis (TGA/DTG) was conducted to feature the thermal stability of CEBs. The results indicated that the preparation methods significantly affected the performance of cured CEBs, although the same mix design was adopted. The curing temperature determined the curing rate of CEBs, while the preparation methods dominated the morphological characteristic of cured CEBs. The three-component preparation method can achieve acceptable mechanical performance for engineering requirements. As for two-component methods, the curing agent is supposed to be mixed with bitumen to obtain satisfying microstructures of CEBs.

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Star-Shaped Crosslinker for Multifunctional Shape Memory Polyurethane

Polymers ◽

10.3390/polym12040740 ◽

2020 ◽

Vol 12 (4) ◽

pp. 740 ◽

Cited By ~ 1

Author(s):

Xiuhuan Song ◽

Hong Chi ◽

Zibiao Li ◽

Tianduo Li ◽

FuKe Wang

Keyword(s):

Shape Memory ◽

Flame Retardant ◽

Fire Resistance ◽

Mechanical Performance ◽

Tensile Tests ◽

Mechanical Analysis ◽

Good Shape ◽

Thermosetting Polymers ◽

High Flexibility ◽

Shape Memory Polyurethane

Star-shaped cyclophosphazene (ACP) was employed as covalent crosslinker to form a rigid segment in polyurethanes network, to enhance the mechanical performance and to add extra flame retardant property. The effects of different ACP contents on the shape memory ability and fire resistance performance of polyurethane (PU) were studied. Tensile tests suggested high flexibility of the PUs with the maximum elongation-at-break of 161.59%. Dynamic mechanical analysis (DMA) indicated good shape recovery ratio of 72.58% after more than three repeated cycles. Under thermal treatment, the temporary shape could recover to its original state in 10 s. The peak heat release rate (pHRR), total heat released (THR) and temperature at pHRR (Tp) of flame-retardant shape memory polyurethane (FSPU) by micro-combustion calorimeter (MCC) was as low as 183.2 W/g, 21.4 KJ/g, 330.8 °C respectively, suggesting good inherent fire-resistant performance. As amine-containing crosslinkers are one of the most common building units in thermosetting polymers, we anticipate that our finding will have significant benefits beyond shape memory and fire-resistance.

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Copper slag as a potential waste filler for polyethylene-based composites manufacturing

Tanzania Journal of Science ◽

10.4314/tjs.v47i2.1 ◽

2021 ◽

Vol 47 (2) ◽

pp. 405-420

Author(s):

Aleksander Hejna ◽

Paulina Kosmela ◽

Mateusz Barczewski ◽

Olga Mysiukiewicz ◽

Adam Piascki

Keyword(s):

Mechanical Properties ◽

Mechanical Performance ◽

Copper Slag ◽

Tensile Tests ◽

Mechanical Analysis ◽

Filler Loading ◽

Copper Production ◽

Color Analysis ◽

Composites Manufacturing ◽

Static Tensile

The present study aimed to analyze the application of waste material from copper production– copper slag (ŻŻL) as filler for composites based on the high-density polyethylene (HDPE). Copper slag filler was introduced in the amounts of 1–20 wt%, and its influence on the appearance (color analysis), chemical structure (Fourier-transform infrared (FTIR) spectroscopy), microstructure (optical microscopy), as well as static (tensile tests) and dynamic (dynamical mechanical analysis (DMA)) mechanical properties of composites were investigated. Proper dispersion of filler implicated that the incorporation of up to 5 wt% of filler caused only slight, 5% drop of tensile strength, with the simultaneous 16% rise of Young’s modulus. Further increase of filler loading resulted in higher values of porosity and the rise of the adhesion factor, determined from DMA results, which led to the deterioration of mechanical performance. Moreover, spectroscopic analysis of PE-ŻŻL composites indicated that the analyzed filler might be applied as a coloring agent, and the appearance of composites may be engineered by adjustment of filler loading. Keywords: polyethylene, copper slag, mechanical properties, structure, composite, particle reinforced composite

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Poly(ε-Caprolactone)/Brewers’ Spent Grain Composites—The Impact of Filler Treatment on the Mechanical Performance

Journal of Composites Science ◽

10.3390/jcs4040167 ◽

2020 ◽

Vol 4 (4) ◽

pp. 167

Author(s):

Aleksander Hejna

Keyword(s):

Chemical Structure ◽

Mechanical Performance ◽

Natural Fiber ◽

Reactive Extrusion ◽

Tensile Tests ◽

Mechanical Analysis ◽

Mechanical Tests ◽

Interface Surface ◽

Spent Grain ◽

The Impact

Waste lignocellulose materials, such as brewers’ spent grain, can be considered very promising sources of fillers for the manufacturing of natural fiber composites. Nevertheless, due to the chemical structure differences between polymer matrices and brewers’ spent grain, filler treatment should be included. The presented work aimed to investigate the impact of fillers’ reactive extrusion on the chemical structure and the poly(ε-caprolactone)/brewers’ spent grain composites’ mechanical performance. The chemical structure was analyzed by Fourier-transform infrared spectroscopy, while the mechanical performance of composites was assessed by static tensile tests and dynamic mechanical analysis. Depending on the filler pretreatment, composites with different mechanical properties were obtained. Nevertheless, the increase in pretreatment temperature resulted in the increased interface surface area of filler, which enhanced composites’ toughness. As a result, composites were able to withstand a higher amount of stress before failure. The mechanical tests also indicated a drop in the adhesion factor, pointing to enhanced interfacial interactions for higher pretreatment temperatures. The presented work showed that reactive extrusion could be considered an auspicious method for lignocellulose filler modification, which could be tailored to obtain composites with desired properties.

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Wastes from Agricultural Silage Film Recycling Line as a Potential Polymer Materials

Polymers ◽

10.3390/polym13091383 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1383

Author(s):

Jerzy Korol ◽

Aleksander Hejna ◽

Klaudiusz Wypiór ◽

Krzysztof Mijalski ◽

Ewelina Chmielnicka

Keyword(s):

Vinyl Acetate ◽

Thermal Performance ◽

Mechanical Performance ◽

Ethylene Vinyl Acetate ◽

Tensile Tests ◽

Solid Particles ◽

Polymer Materials ◽

Slight Reduction ◽

Scanning Calorimetry ◽

Crystallinity Degree

The recycling of plastics is currently one of the most significant industrial challenges. Due to the enormous amounts of plastic wastes generated by various industry branches, it is essential to look for potential methods for their utilization. In the presented work, we investigated the recycling potential of wastes originated from the agricultural films recycling line. Their structure and properties were analyzed, and they were modified with 2.5 wt % of commercially available compatibilizers. The mechanical and thermal performance of modified wastes were evaluated by tensile tests, thermogravimetric analysis, and differential scanning calorimetry. It was found that incorporation of such a small amount of modifiers may overcome the drawbacks caused by the presence of impurities. The incorporation of maleic anhydride-grafted compounds enhanced the tensile strength of wastes by 13–25%. The use of more ductile compatibilizers—ethylene-vinyl acetate and paraffin increased the elongation at break by 55–64%. The presence of compatibilizers also reduced the stiffness of materials resulting from the presence of solid particles. It was particularly emphasized for styrene-ethylene-butadiene-styrene and ethylene-vinyl acetate copolymers, which caused up to a 20% drop of Young’s modulus. Such effects may facilitate the further applications of analyzed wastes, e.g., in polymer film production. Thermal performance was only slightly affected by compatibilization. It caused a slight reduction in polyethylene melting temperatures (up to 2.8 °C) and crystallinity degree (up to 16%). For more contaminated materials, the addition of compatibilizers caused a minor reduction in the decomposition onset (up to 6 °C). At the same time, for the waste after three washing cycles, thermal stability was improved. Moreover, depending on the desired properties and application, materials do not have to go through the whole recycling line, simplifying the process, reducing energy and water consumption. The presented results indicate that it is possible to efficiently use the materials, which do not have to undergo the whole recycling process. Despite the presence of impurities, they could be applied in the manufacturing of products which do not require exceptional mechanical performance.

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Bio-Based Polyurethane Networks Derived from Liquefied Sawdust

Materials ◽

10.3390/ma14113138 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3138

Author(s):

Kamila Gosz ◽

Agnieszka Tercjak ◽

Adam Olszewski ◽

Józef Haponiuk ◽

Łukasz Piszczyk

Keyword(s):

Biomass Conversion ◽

Structural Features ◽

Mechanical Analysis ◽

Process Efficiency ◽

Hydroxyl Number ◽

Step Method ◽

One Step ◽

Liquefaction Process ◽

The Fourier Transform ◽

Liquefaction Temperature

The utilization of forestry waste resources in the production of polyurethane resins is a promising green alternative to the use of unsustainable resources. Liquefaction of wood-based biomass gives polyols with properties depending on the reagents used. In this article, the liquefaction of forestry wastes, including sawdust, in solvents such as glycerol and polyethylene glycol was investigated. The liquefaction process was carried out at temperatures of 120, 150, and 170 °C. The resulting bio-polyols were analyzed for process efficiency, hydroxyl number, water content, viscosity, and structural features using the Fourier transform infrared spectroscopy (FTIR). The optimum liquefaction temperature was 150 °C and the time of 6 h. Comprehensive analysis of polyol properties shows high biomass conversion and hydroxyl number in the range of 238–815 mg KOH/g. This may indicate that bio-polyols may be used as a potential substitute for petrochemical polyols. During polyurethane synthesis, materials with more than 80 wt% of bio-polyol were obtained. The materials were obtained by a one-step method by hot-pressing for 15 min at 100 °C and a pressure of 5 MPa with an NCO:OH ratio of 1:1 and 1.2:1. Dynamical-mechanical analysis (DMA) showed a high modulus of elasticity in the range of 62–839 MPa which depends on the reaction conditions.

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Chemical and physical interactions of regenerated cellulose yarns and isocyanate-based matrix systems

Scientific Reports ◽

10.1038/s41598-021-91115-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Bernhard Ungerer ◽

Ulrich Müller ◽

Antje Potthast ◽

Enrique Herrero Acero ◽

Stefan Veigel

Keyword(s):

Mechanical Performance ◽

Tensile Force ◽

Tensile Modulus ◽

Tensile Tests ◽

Size Exclusion ◽

Regenerated Cellulose ◽

Hydrolytic Cleavage ◽

Yarn Twist ◽

Exclusion Chromatography ◽

Physical And Chemical

AbstractIn the development of structural composites based on regenerated cellulose filaments, the physical and chemical interactions at the fibre-matrix interphase need to be fully understood. In the present study, continuous yarns and filaments of viscose (rayon) were treated with either polymeric diphenylmethane diisocyanate (pMDI) or a pMDI-based hardener for polyurethane resins. The effect of isocyanate treatment on mechanical yarn properties was evaluated in tensile tests. A significant decrease in tensile modulus, tensile force and elongation at break was found for treated samples. As revealed by size exclusion chromatography, isocyanate treatment resulted in a significantly reduced molecular weight of cellulose, presumably owing to hydrolytic cleavage caused by hydrochloric acid occurring as an impurity in pMDI. Yarn twist, fibre moisture content and, most significantly, the chemical composition of the isocyanate matrix were identified as critical process parameters strongly affecting the extent of reduction in mechanical performance. To cope with the problem of degradative reactions an additional step using calcium carbonate to trap hydrogen ions is proposed.

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Mechanical Optimization of Concrete with Recycled PET Fibres Based on a Statistical-Experimental Study

Materials ◽

10.3390/ma14020240 ◽

2021 ◽

Vol 14 (2) ◽

pp. 240

Author(s):

Alejandro Meza ◽

Pablo Pujadas ◽

Laura Montserrat Meza ◽

Francesc Pardo-Bosch ◽

Rubén D. López-Carreño

Keyword(s):

Reinforced Concrete ◽

Aspect Ratio ◽

Mechanical Performance ◽

Tensile Tests ◽

Superior Performance ◽

Fibre Reinforced Concrete ◽

Marine Fauna ◽

Recycled Pet ◽

Pet Bottles ◽

Fibre Aspect Ratio

Discarded polyethylene terephthalate (PET) bottles have damaged our ecosystem. Problems of marine fauna conservation and land fertility have been related to the disposal of these materials. Recycled fibre is an opportunity to reduce the levels of waste in the world and increase the mechanical performance of the concrete. PET as concrete reinforcement has demonstrated ductility and post-cracking strength. However, its performance could be optimized. This study considers a statistical-experimental analysis to evaluate recycled PET fibre reinforced concrete with various fibre dose and aspect ratio. 120 samples were experimented under workability, compressive, flexural, and splitting tensile tests. The results pointed out that the fibre dose has more influence on the responses than its fibre aspect ratio, with statistical relation on the tensional toughness, equivalent flexural strength ratio, volumetric weight, and the number of fibres. Moreover, the fibre aspect ratio has a statistical impact on the tensional toughness. In general, the data indicates that the optimal recycled PET fibre reinforced concrete generates a superior performance than control samples, with an improvement similar to those reinforced with virgin fibres.

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