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Silica nanoparticles were reported that can improve the fire safety and mechanical properties of polymers simultaneously due to excellent rigidity and physical barrier effect. However, its efficiency was limited by the agglomeration in polymers due to their high specific surface energy. Silica@ polydopamine (SiO2@PDA) was prepared by a facile self-polymerization method to comprehensively improve fire safety, thermal stability, and mechanical properties of plant fiber-reinforced polymer (PFRP) composites. The results of micro-morphology confirmed that the SiO2@PDA nanoparticles exhibit better dispersion state in epoxy matrix. The introduction of SiO2@PDA further increased the thermal decomposition temperature and the yield of graphitized char residue of PFRP composites compared to pure silica nanoparticles. And the fire safety of composites including limiting oxygen index, heat parameters, smoke parameters and mass loss rate was improved effectively. Particularly, the time to ignition of composites was delayed by 30 s, which was beneficial for individuality escape and rescue. Meanwhile, the improvement of storage modulus suggested the SiO2@PDA enhanced the mechanical properties of the PFRP composites. And it was proved that PDA can improve the graphitization degree of char layer and release inert gas including NH3 and CO2 during combustion. The effectiveness of non-toxic PDA in enhancing the quality of char layer and optimizing the interface to improve the dispersion state of nanoparticles appeared promising potential in the field of manufacturing fire-safe polymer-matrix composites. [ABSTRACT FROM AUTHOR]

Nowadays, continuous development of soft-electronics and wearable devices opens to the development needs of stretchable and flexible materials able to interface with the human body. In this scenario, biopolymers are particularly intriguing materials given their biocompatibility and biodegradability. For the application in this specific field the material requires several properties such as biological and mechanical performance and thermal stability. In this study, membranes able to fulfill some of these requirements are described. The electrospun membranes, composed of a blend of polycaprolactone (PCL) and gelatin (GN), have been produced in various configurations. The results show how blend or coaxial systems have different effects on both the interactions between the polymers and their thermal and mechanical properties. An important result of the chosen experimental conditions is the narrow dimensional distribution of the nanofiber diameters constituting the electrospun membranes. Thermal and mechanical tests evidenced that, by properly choosing the material composition and the method of the electrospinning process, membranes capable of withstanding high strain values before the failure can be obtained. In particular, optimizing the electrospinning process and using a blend PCL/GN with a mass ratio of 80/20, it is possible to increase the thermal stability up to 310 °C and confer to the sample the ability to reach a percentage of strain up to 350%. [ABSTRACT FROM AUTHOR]

In this work, thermal and mechanical properties of cationic cassava starch-g-poly(butyl acrylate-co-methyl methacrylate) films with different amounts of cationic cassava starch (CCS) were studied. The objective of this work was to substitute a portion the monomers (BA/MMA) by CCS in the copolymer and to investigate the consequent effects on the properties of the polymer latex films (e.g., graft percentage, surface tension, thermal and mechanical properties). The results show that the grafting percentage decreased as the concentration of CCS increased. Thermal and mechanical properties of polymer films showed a direct relationship with respect to the content of CCS used and the grafting percentage. Higher grafting percentage led to improvement of the thermal degradation, which indicated better thermal stability than neat poly(BA/MMA). DSC analysis showed that the Tg of the graft copolymers was a little lower as compared to Tg values of un-grafted copolymers. The addition of CCS increases the tensile, elastic modulus and hardness properties of the polymer film, but the elongation at break decreased dramatically. The optimal CCS contents that maximized not only thermal properties, but also mechanical properties, were 7 and 10 mass%, which are directly related to the grafting percentage and CCS content in the formulation. In addition, these results create a new approach for the application of CCS graft-polymer as an adhesive for wood, paper and shoes insole applications. [ABSTRACT FROM AUTHOR]

Different types of phosphorus containing halogen-free flame retardants (FRs) were added to an epoxy-dicyandiamide resin formulation in order to study to which extent they affect its glass transition temperature (Tg), tensile properties, thermal stability and burning behavior of the resin. For this purpose, an additive-type FR (ammonium polyphosphate encapsulated in melamine resin, MAPP) and two reactive-type FRs i) a commercial epoxy resin pre-reacted with 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide, (DOPO), and ii) a phosphorus containing hardener (poly(m-phenylene methylphosphonate), (PMP) were used. It was observed that the addition of additive-type FR did not affect in great extent the Tg and provided a V-0 rating in UL94 test at low loadings. The addition of reactive-type FRs (DOPO and/or PMP), however, modified the structure of the chain network resulting in lower crosslink density as a consequence of their higher equivalent mass, but achieving also with low PMP content V-0 rating. [ABSTRACT FROM AUTHOR]

In the present research, mechanical and thermal properties of high-density polyethylene/wood flour were improved by incorporating nanoclay (Cloisite 30B) and antioxidant (Irganox B225) in the compound. Design of experiments was carried out to optimize composition among nine compounds and to investigate the effect of nanoclay and antioxidant (0–5 phr) and (0–0.4 phr), respectively. The results of mechanical tests showed approximately 24% increase in the tensile strength of compounds containing 2.5 and 5.0 part per hundred (phr) of the nanoclay in the composite compared with the same samples without nanoclay. The tensile modulus of composites increased 7.3% by increasing the level of nanoclay from 0 to 2.5 phr. However, a further increase in the nanoclay content led to a 4.3% decrease in tensile modulus. Evaluation of the thermal oxidation stability of samples confirmed that the thermal oxidation of composites decreased with increasing nanoclay from 0 to 5.0 phr and increased significantly with the addition of the antioxidant. [ABSTRACT FROM AUTHOR]

In this paper, the poly(ester-urethane)s obtained using petrochemical and bio-based chain extenders were prepared and characterized. The influence of glycols' origin on the chemical structure, mechanical and thermal properties of the prepared polyurethanes was studied. The materials were synthesized by prepolymer method. The first step involved the reaction of α,ω-dihydroxy(ethylene-butylene adipate) (POLIOS 55/20) with 4,4′-diphenylmethane diisocyanate (MDI). In the next step, obtained prepolymer terminated with isocyanate group was extended using 1,3-propanediol and 1,4-butanediol at three different molar ratios of NCO group (presented in prepolymer chains) to OH groups (presented in chain extender structure), i.e., 0.95, 1.0 and 1.05. The results showed that applying the different types (diversified chemical structure and origin) of glycols results in obtaining materials with diversified mechanical properties and slight different thermal stabilities. The results of Fourier transform infrared spectroscopy showed that the chemical structure of the obtained polyurethanes was not affected by the presence of glycols with the same chemical structure and different origins (petrochemical and bio-based nature). [ABSTRACT FROM AUTHOR]

In this work, in order to investigate the reinforcement effects of organomontmorillonite (OMMT) in soybean oil-based polyurethane (PU)/epoxy (EP) interpenetrating polymer networks (IPNs), a series of OMMT-modified PU/EP IPNs were prepared. The impacts of OMMT on the structure, morphology, glass transition, damping properties, thermal stability, and mechanical properties of the PU/EP IPNs were characterized by X-ray diffraction, scanning electronic microscope, dynamic mechanical analysis, thermogravimetry analysis, and tensile test. Results reveal that the addition of OMMT increases the glass transition temperature of the PU/EP IPNs. However, the damping properties of the PU/EP IPNs are lowered with the incorporation of OMMT. The addition of OMMT heightens the thermal stability of the PU/EP IPNs. Tensile tests show that the addition of OMMT significantly increases the tensile strength and tensile modulus of the PU/EP IPNs. With 4 and 6 % loading of OMMT, the tensile strength and tensile modulus increase 64 and 391 %, respectively. [ABSTRACT FROM AUTHOR]

The higher mechanical properties of polypropylene (PP) fibers based on metallocene-catalyzed PP (miPP) in comparison with fibers based on Ziegler-Natta-catalyzed PP (zniPP) were presented in periodic literature in the last decade. At the same time the miPP fibers have lower crystallinity and lower melting temperature compared with conventional zniPP fibers. In our experimental work, the thermal and mechanical properties of both the miPP and zniPP multifilaments depending on their spinning and drawing conditions were investigated. The dynamic viscosity and deviation from the Newtonian flow of polymer melt were evaluated as important parameters for melt-spinning technology. The melting temperature, melting enthalpy and melting entropy of multifilaments were investigated using DSC analysis in dependence on spinning temperature and draw ratio of fibers. At the same time the mechanical properties of fibers tenacity, elongation and elastic modulus were measured. The DSC measurements were carried out using conventional method and constant length method at which the constant length of fibers was held (constrained fibers). The changes in melting temperature, melting enthalpy and melting entropy of drawn fibers were analyzed and correlated with mechanical properties of fibers. The mechanical and thermal properties of fibers were discussed with regard to the spinning and drawing conditions as well. [ABSTRACT FROM AUTHOR]

The influence of two types of carbon black filler N330 and N990 (primary particle size 46 nm and >230 nm) on elastomeric composites based on acrylonitrile-butadiene rubber (NBR) have been investigated. The activation energy ( Ea) were determined from two high temperature rheokinetic curves ( T1 = 180 °C and T2 = 190 °C). For tensile testing, the compounds with different content of carbon black were vulcanized in a hydraulic press at 150 °C. The stress-strain experiments were performed before and after ageing the specimens in an air-circulating oven at 100 °C for 168 h. The thermal degradation and thermal stability of carbon black filled NBR rubber was investigated by thermogravimetric analysis in a flowing nitrogen atmosphere at a heating rate of 10 °C/min. [ABSTRACT FROM AUTHOR]