Properties Of Other Polymers Research Articles

Effect of mold temperature on properties of hybrid biocomposites from semicrystalline polymers and agro-industrial by-products

The surface temperature of the mold is a critical processing parameter that significantly influences the quality of composites during injection molding. Therefore, this study aimed to investigate the effect of mold surface temperature on the properties of hybrid biocomposite materials prepared by incorporating polypropylene-PP with agro-industrial by-products such as rice husks-RH and fique powder-FP using co-rotating twin-screw extrusion and injection molding. While this article focuses on PP as the polymeric matrix, the methodology employed in this study can also be applied to investigate the effect of mold surface temperature on the properties of other polymers used in the production of hybrid composites via injection molding as biobased or biodegradable plastics. The mechanical characterization reveals that the utilization of higher mold temperatures and the hybridization of RH and FP result in an increase in the elastic modulus of up to 30% compared to PP. Also, thermal, viscoelastic, morphological, and HDT characterization revealed that higher surface mold temperature led to changes in PP crystallinity, and a better hybrid biocomposites performance. This study highlights the potential of mold surface temperature controlling and agro-industrial by-products hybridization for the design and production of higher quality and sustainable products using injection molding.

Supramolecular additive-induced conformational transition of polymer chains via π-π interaction

Controlling the conformation of polymer chains throughout melt processing is a critical factor in the development and optimization of polymer materials for a variety of applications. In this study, we present a supramolecular strategy for modulating the conformational transition of polymer and investigate the structural evolution with supramolecular additive. It is found that minute amounts (0.07–0.9 wt%) of supramolecular nucleating agent, N, N′-dicyclohexylterephthalamide (DCHT), enable polystyrene (PS) chains to adopt more gauche conformation than the trans mode when processed from the melt, resulting in higher PS chain mobility and improved PS film transmittance. The conformational transition of PS chains shows dependence on the π-π interactions between PS and DCHT molecules. By controlling the critical assembly concentration and the self-assembly behavior of DCHT in PS, it is possible to tailor the ratio of gauche to trans states and the corresponding properties of PS. We anticipate that this study will advance the design and development of supramolecular additives for tailoring the structure and properties of other polymers.

Effect of Thermal Aging on Dynamic Mechanical Performance of a Novel Structural Adhesive

This study mainly evaluates the thermal aging properties of a new room temperature cured structural adhesive. Multiple adhesive specimens were thermal aged at 80℃, 100℃, 120℃ and 140℃, respectively, and subjected to the dynamic mechanical analysis (DMA) at different temperatures and frequencies. According to the results of DMA and thermodynamic analysis, the performance of the adhesive changes little after aging at 80℃, 100℃ and 120℃ for 30 days. However, the adhesive performance became unstable at 140℃, and deteriorated rapidly with the extension of aging time. Hence, this structural adhesive is suitable for the environment below 120℃. In addition, the generalized curve of the structural adhesive aging for 20 days at 100℃ was obtained, following the principles of time-temperature equivalence superposition and time-aging time equivalence superposition. The test time was shortened significantly. This research provides an accelerated characterization strategy for the long-term mechanical properties of other polymers, making it possible to obtain the generalized curve of polymers aging for a specific time at a specific temperature.

Theoretical studies of structural, optic and electronic properties of polypyrrole (PPy) oligomer

The paper demonstrates theoretical studies of structural, optical and electronic properties of polypyrroll oligomer. first-principles calculations are used to investigate the electronic properties of n-pyrrole oligomers with n = 1–29, and all results were plotted to determine the optimal number of chains (n). Then, transition energies and oscillator strengths for the electronic excitation of the first 12 singlet-to-singlet excited states of PPy were calculated using time-dependent (TD) DFT at the same level. In addition, optical properties of PPy were studied as theoretically. It was observed that there is quite compatibility between the calculated and experimental data. We think that this systematic study may be useful for the structural analysis, spectroscopic and theoretical properties of other oxime I think that this systematic study may be useful for the structural analysis, optical and theoretical properties of other polymers. .

Eco-Friendly Flame-Retardant Additives for Polyurethane Foams: A Short Review

Polyurethane (PU) materials are extensively used in the construction industry as core material insulation for sandwich panel application, such as wall cladding, structure insulation and roof panel. Demands on PU application have escalated given its significant advantages to reduce energy consumption. Meanwhile, rigid PU (RPU) foams are combustible materials characterized by rapid flame spread, high heat-release rates, and ability to produce large quantities of toxic gases in original form. Thus, flame-retardant (FR) additives are used to improve the thermal properties of PU. However, some commercial additives used today have are hazardous to humans and the environment, and their extensive application is limited by their negative effects on polymer mechanical properties. Accordingly, identifying materials that are environmentally friendly and harmless to humans has become urgent. Some alternative additives that are gaining research interest are clay and fly ash, which are natural and recyclable resources that can enhance the FR properties of other polymers. However, room for improvement is always present as the related technology is continually being developed. This review focuses on studies aiming to enhance the flame retardancy of RPU foam using fly ash and local clay as additives.

Quantitative analysis of mechanical and electrostatic properties of poly(lactic) acid fibers and poly(lactic) acid—carbon nanotube composites using atomic force microscopy

We use atomic force microscopy (AFM) to perform a systematic quantitative characterization of the elastic modulus and dielectric constant of poly(L-lactic acid) electrospun nanofibers (PLLA), as well as composites of PLLA fibers with 1.0 wt% embedded multiwall carbon nanotubes (MWCNTs–PLLA). The elastic moduli are measured in the fiber skin region via AFM nanoindentation, and the dielectric constants are determined by measuring the phase shifts obtained via electrostatic force microscopy (EFM). We find that the average value for the elastic modulus for PLLA fibers is (9.8 ± 0.9) GPa, which is a factor of 2 larger than the measured average elastic modulus for MWCNT–PLLA composites (4.1 ± 0.7) GPa. We also use EFM to measure dielectric constants for both types of fibers. These measurements show that the dielectric constants of the MWCNT–PLLA fibers are significantly larger than the corresponding values obtained for PLLA fiber. This result is consistent with the higher polarizability of the MWCNT–PLLA composites. The measurement methods presented are general, and can be applied to determine the mechanical and electrical properties of other polymers and polymer nanocomposites.

Properties of linear elastomeric polyurethanes

AbstractThe viscoelastic properties of some polyester‐urethanes are compared with the properties of other polymers. The behavior observed is anomalous in that these polyurethanes exhibit an unusually high value of modulus well above their Tg, unaccounted for by either crosslinking or crystallinity. Various experiments including incorporation of plasticizes of widely varying chemical composition have suggested interpretation of the system as a block copolymer, each block having its own Tg. Each of the two types of blocks seems to associate with similar blocks from other molecules.

The Kinetics of High Elasticity in Synthetic Polymers

Abstract The simple Mark-Kuhn theory of high elasticity of rubber has been extended, on the basis of the work of Alexandrov and Lazurkin, to cover the elastic properties of other polymers. The chief principle invoked is that high elasticity is developed only when rotation of the main C—C chain in the polymer is comparatively free. The effect of molecular structure, plasticizer and cross-links on elastic properties has been indicated, and also a connection with other observed physical properties, such as volume expansion, dielectric dispersion and specific heat.

The kinetics of high elasticity in synthetic polymers

Abstract The simple Mark-Kuhn theory of high elasticity of rubber has been extended, on the basis of the work of Alexandrov and Lazurkin, to cover the elastic properties of other polymers. The chief principle invoked is that high elasticity is developed only when rotation of the main C—C chain in the polymer is comparatively free. The effect of molecular structure, plasticizer and cross-links on elastic properties has been indicated, and also a connection with other observed physical properties, such as volume expansion, dielectric dispersion and specific heat.