On the multiple melting behavior of bisphenol-A polycarbonate

Synthesis and Properties of Semicrystalline Poly(ether nitrile ketone) Copolymers

As a high-performance engineering plastic, polyarylene ether nitrile (PEN) is widely used in many fields. The presence of cyano groups of PEN ensures its good adhesion to other substrates, but the inherent low crystallinity of PEN limits its application. In this work, the poly(aryl ether ketone) segment was introduced into PEN via copolymerization using both 2,6-Dichlorobenzonitrile and 4,4'-Difluorobenzophenone as the starting reagents to prepare poly (ether nitrile ketone) (BP-PENK). The effect of composition and thermal treatment on the crystallization behavior and properties of poly (ether nitrile ketone) were systematically studied. It was found that when the content of DFBP is 30%, the copolymer BP-PENK30 had the best mechanical properties, with a tensile strength of 109.9 MPa and an elongation at a break value of 45.2%. After thermal treatment at 280 °C for 3 h, BP-PENK30 had the highest crystallinity with a melting point of 306.71 °C, a melting enthalpy of 5.02 J/g, and crystallinity of 11.83%. Moreover, with the increase in crystallinity, the dielectric constant and energy density increased after thermal treatment. Therefore, the introduction of poly(aryl ether ketone) chain segments and thermal treatment can effectively improve the crystallization and the comprehensive properties of PEN.

The Study of Crystallization Behavior, Microcellular Structure and Thermal Properties of Glass-Fiber/Polycarbonate Composites

Polycarbonate (PC) foam is a versatile material with excellent properties, but its low thermal stability limits its application in high-temperature environments. The aim of this study was to improve the thermal stability of PC foam by adding glass fibers (GF) and to investigate the effect of GF on PC crystallization behavior and PC foam cell morphology. This study was motivated by the need to improve the performance of PC foams in various industries, such as construction, automotive, and medical. To achieve this goal, PC/GF composites were prepared by extrusion, and PC/GF composite foams were produced using a batch foaming process with supercritical carbon dioxide (SC-CO₂) as the blowing agent. The results showed that the addition of GF accelerated the SC-CO₂-induced crystallization stability of PC and significantly increased the cell density to 4.6 cells/cm³. In addition, the thermal stability of PC/GF foam was improved, with a significant increase in the residual carbon rate at 700 °C and a lower weight loss rate than PC matrix. Overall, this study highlights the potential of GF as a PC foam reinforcement and its effect on thermal and structural properties, providing guidance for industrial production and applications.

Superhydrophobic Polydimethylsiloxane via Nanocontact Molding of Solvent Crystallized Polycarbonate: Optimized Fabrication, Mechanistic Investigation, and Application Potential

Herein, we describe a benchtop protocol to create superhydrophobic polydimethylsiloxane (PDMS) via nanocontact molding of polycarbonate (PC) that was crystallized by controlled solvent treatment. The crystallized PC chains rearrange into a network of spherulites (spherical semicrystalline domains); the overall surface is rough on the micrometer-scale, while the spherulites themselves consist of nanoscale features. It was confirmed via conventional spectroscopic and high-resolution microscopic investigation that such hierarchical roughness is key to the development of superhydrophobic PC and the substantial enhancement upon PDMS molding. Thus, the prepared PDMS surface has excellent superhydrophobicity with an optimized contact angle of 172 ± 1° and a sliding angle of <1°, superior to those prepared from more elaborate techniques, such as plasma sputtering and laser etching. More importantly, the knowledge acquired regarding the structural transition and superhydrophobicity development would be beneficial to engineering and evaluating templates for many other polymeric nanostructures and functional surfaces.

From terpenes to sustainable and functional polymers

The use of renewable terpene-based monomers for the preparation of sustainable functional polymers is highlighted.

Influence of Bulk Temperature on Laser-Induced Periodic Surface Structures on Polycarbonate

In this paper, the influence of the bulk temperature (BT) of Polycarbonate (PC) on the occurrence and growth of Laser-induced Periodic Surface Structures (LIPSS) is studied. Ultrashort UV laser pulses with various laser peak fluence levels F0 and various numbers of overscans (NOS) were applied on the surface of pre-heated Polycarbonate at different bulk temperatures. Increased BT leads to a stronger absorption of laser energy by the Polycarbonate. For NOS<1000 High Spatial Frequency LIPSS (HSFL), Low Spatial Frequency LIPSS perpendicular (LSFL-I) and parallel (LSFL-II) to the laser polarization were only observed on the rim of the ablated tracks on the surface but not in the center of the tracks. For NOS≥1000, it was found that when pre-heating the polymer to a BT close its glass transition temperature (Tg), the laser fluence to achieve similar LIPSS as when processed at room temperature decreases by a factor of two. LSFL types I and II were obtained on PC at a BT close to Tg and their periods and amplitudes were similar to typical values found in the literature. To the best of the author’s knowledge, it is the first time both LSFL types developed simultaneously and consistently on the same sample under equal laser processing parameters. The evolution of LIPSS from HSFL, over LSFL-II to LSFL I, is described, depending on laser peak fluence levels, number of pulses processing the spot and bulk temperature.

Coexistence of melting and growth during heating of a semicrystalline polymer

The coexistence of melting and growth during heating is observed by molecular dynamics simulations of semicrystalline entangled polymers. During heating, some microcrystalline domains (MCDs) are melted while others are still growing, which can be associated with multiple-peaked melting endotherms. The growth of MCD's stability is related to the increase of molecular disorder. The increasing of the stem length during annealing close to the melting point is contributed by the orientational correlation in the semimelted surface regions while direct trans-trans states are decreasing which increases the flexibility and mobility of the crystalline stems.

Comportamento do polipropileno em presença de monômeros trifuncionais no estado fundido e sua influência na morfologia

O aumento de ramificações e da massa molecular em polímeros essencialmente lineares influencia as propriedades no estado fundido desses polímeros. Este comportamento foi observado pela análise dos dados de resistência do fundido, extensibilidade e do conteúdo de gel em amostras de Polipropileno linear (iPP) modificado. A modificação foi obtida utilizando agentes modificadores (monômeros multifuncionais) e radiação gama. Os agentes modificadores empregados foram o Tri-metilol-propano-tri-acrilato (TMPTA) e o Tri-alil-cianurato (TAC). O TMPTA demonstrou ser um agente mais eficiente para a promoção do iPP modificado (reticulado/ramificado), uma vez que o produto final apresentou um valor maior da resistência do fundido do que o material com TAC. No entanto, ambos modificam a morfologia original do iPP constatada pelo deslocamento do pico de fusão para temperaturas menores, pelo aumento da temperatura de cristalização (Tc) e pela presença de múltiplas endotermas.