Self-initiated butyl acrylate polymerizations in bulk and in solution monitored by in-line techniques

High-temperature acrylate polymerizations are technically relevant, but yet not fully understood. In particular the mechanism and the kinetics of the thermal self-initiation is a topic of current research. To obtain more detailed information the conversion dependence of the polymerization rate, rbr, is determined via in-line DSC and FT-NIR spectroscopy for reactions in bulk and in solution at temperatures ranging from 80 to 160 ◦C. Solution polymerizations revealed that dioxane is associated with the highest rbr, while aromatic solvents result in the lowest values of rbr. Interestingly, rbr for polymerizations in solution with dioxane depends on the actual monomer concentration at a given time in the system, but is not depending on the initial monomer concentration. The overall rate of polymerization in bulk and in solution is well represented by an equation with three or four parameters, respectively, being estimated by multiple linear regression and the temperature as additional parameter

Ultrasonic Degradation of Polystyrene for Tailoring Molecular Weight and Polydispersity of Polystyrene Fragments

Ultrasonic degradation of polymers attracts more and more attention in the field of chemical recycling of polymers due to the promising opportunity to tailor molecular weight and polydispersity of the gained polymer fragments. In this work, the influence of solvent, gas atmosphere, and ultrasound amplitude on the ultrasonic degradation process of polystyrene is investigated. Therefore, an experimental procedure to perform ultrasonic degradation of polystyrene under homogeneous temperature conditions in the solvents cyclohexane and toluene under the gas atmospheres CO$_{2}$ and N$_{2}$ for different ultrasonic amplitudes was designed. It could be shown that a significant effect on the molecular weight and polydispersity of the polymer could only be revealed for N$_{2}$ and not for CO$_{2}$ atmosphere

Influence of spray drying parameters on the formation of β-phase poly(vinylidene fluoride)

A simple one-step spraying method to produce poly(vinylidene fluoride) (PVDF) in the desired conformation is presented. The content of the piezoelectric β-phase is measured at different spray drying conditions and during electrospray. The influence of a strong electrical field and charges on the droplet are investigated separately from the electrospray setup with a pneumatic atomizer. For this purpose, the electric field is integrated into a pneumatic atomization process by a plate capacitor and the charge of the droplets by corona discharge. To investigate the drying properties, the drying temperature and the flow rate of dry air are examined. The presented process offers the possibility to deposit PVDF films or to produce PVDF powders, in their piezoelectric β- and γ-phases or in the nonpolar α-phase

Molecular weight as a key for electroactive phase formation in poly(vinylidene fluoride)

Outstanding electroactive properties of certain crystallographic phases of poly(vinylidene fluoride)(PVDF) bring much attention to its melting and crystallisation behaviour for tailoring crystallographic nature. In the past, the focus was put on operating conditions in terms of melting and crystallisation kinetics, whereas a deeper understanding of the molecular structure–property relationship of PVDF is sparsely addressed. This study is the first survey to investigate systematically the structure–property relationship by clarifying the question, how molecular weight distribution affects thermal–caloric properties and hence polymorphous phase behaviour. It is shown that molecular weight strongly influences electroactive phase formation and plays a key role in phase design

Synthesis and Characterization of New Polymers from Adenopus breviflorus benth oil, Styrene and Divinyl benzene by Cationic Polymerization

A variety of new polymers ranging from soft to hard plastics were prepared by cationic polymerization of Adenopus breviflorus oil with styrene and divinyl benzene initiated by modified boron trifluoride etherate. The fully cured thermosets were found to contain between 78- 92% cross linked materials possessing crosslink densities of between 2.39 x 103 to 2.09 x 104 mol/m3 and glass transition temperatures of 12 – 800C. The tensile moduli of the materials ranged from 1.47 to 404MPa, the ultimate tensile stress varied from 0.18 to 7.78MPa and the elongation at break varied between 2 and 34%. Depending on composition, some of the materials possessed good damping and shape memory properties. Overall the newly prepared materials from Adenopus breviflorus oil hold a lot of promise as new polymeric materials

Preparation of Polymer Electrolyte Membranes via Radiation-Induced Graft Copolymerization on Poly(ethylene-alt-tetrafluoroethylene) (ETFE) Using the Crosslinker N,N′-Methylenebis(acrylamide)

Polymer electrolyte membranes (PEM) prepared by radiation-induced graft copolymerization are investigated. For this purpose, commercial poly(ethylene-alt-tetrafluoroethylene) (ETFE) films were activated by electron beam treatment and subsequently grafted with the monomers glycidyl methacrylate (GMA), hydroxyethyl methacrylate (HEMA) and N,N′-methylenebis(acrylamide) (MBAA) as crosslinker. The target is to achieve a high degree of grafting (DG) and high proton conductivity. To evaluate the electrochemical performance, the PEMs were tested in a fuel cell and in a vanadium redox-flow battery (VRFB). High power densities of 134 mW∙cm−2 and 474 mW∙cm−2 were observed, respectively

Controlled release of tea tree oil from a chitosan matrix containing gold nanoparticles

Chitosan is a biopolymer that, due to its versatile bioactive properties, has applications in several areas, including food, medicine and pharmaceuticals. In the field of tissue engineering, chitosan can be used, for example, as a dressing to treat wounds or dermal damage, such as burns or abrasions. This work deals with the controlled release of tea tree oil from chitosan-based polymeric films and droplets containing gold nanoparticles (AuNP). AuNPs were successfully incorporated into the chitosan matrix using two different approaches. Both solutions were loaded with tea tree oil, and from these solutions, it was possible to obtain drop-cast films and droplets. The controlled release of oil in water was performed both in the films and in the droplets. The addition of AuNP in the controlled release system of melaleuca oil favored a release time of around 25 h. A series of experiments was carried out to investigate the effects of different reaction temperatures and acetic acid concentrations on the formation of AuNPs in the presence of chitosan. For this purpose, images of the AuNP films and droplets were obtained using transmission electron microscopy. In addition, UV-vis spectra were recorded to investigate the release of tea tree oil from the different samples

Update and critical reanalysis of IUPAC benchmark propagation rate coefficient data

The dataset used to generate IUPAC benchmark Arrhenius parameters for propagation rate coefficients in radical polymerization is extended and reanalyzed, taking into account systematic interlaboratory variation