5. In Situ Polymerization 3907 5.1. General Polymerization 3907 5.2. Photopolymerization 3910 5.3. Surface-Initiated Polymerization 3912 5.4. Other Methods 3913 6. Colloidal Nanocomposites 3913 6.1. Sol-Gel Process 3914 6.2. In Situ Polymerization 3916 6.2.1. Emulsion Polymerization 3917 6.2.2. Emulsifier-Free Emulsion Polymerization 3919 6.2.3. Miniemulsion Polymerization 3920 6.2.4. Dispersion Polymerization 3921 6.2.5. Other Polymerization Methods 3923 6.2.6. Conducting Nanocomposites 3924 6.3. Self Assembly 3926 7. Other Preparative Methods 3926 8. Characterization and Properties 3928 8.1. Chemical Structure 3928 8.2. Microstructure and Morphology 3929 8.3. Mechanical Properties 3933 8.3.1. Tensile, Impact, and Flexural Properties 3933 8.3.2. Hardness 3936 8.3.3. Fracture Toughness 3937 8.3.4. Friction and Wear Properties 3937 8.4. Thermal Properties 3938 8.5. Flame-Retardant Properties 3941 8.6. Optical Properties 3942 8.7. Gas Transport Properties 3943 8.8. Rheological Properties 3945 8.9. Electrical Properties 3945 8.10. Other Characterization Techniques 3946 9. Applications 3947 9.1. Coatings 3947 9.2. Proton Exchange Membranes 3948 9.3. Pervaporation Membranes 3948 9.4. Encapsulation of Organic Light-Emitting Devices 3948

Polymer/Silica Nanocomposites: Preparation, Characterization, Properties, and Applications

https://bura.brunel.ac.uk/bitstream/2438/18351/1/FullText.pdf

An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling.

Mechanical and chemical recycling of solid plastic waste.

Recently, polymer nanocomposites reinforced with lower volume fraction of nanoceramics and carbon nanotubes have attracted steadily growing interest due to their peculiar and fascinating properties as well as their unique applications in commercial sectors. The incorporation of nanoceramics such as layered silicate clays, calcium carbonate or silica nanoparticles arranged on the nanometer scale with a high aspect ratio and/or an extremely large surface area into polymers improves their mechanical performances significantly. The properties of nanocomposites depend greatly on the chemistry of polymer matrices, nature of nanofillers, and the way in which they are prepared. The uniform dispersion of nanofillers in the polymer matrices is a general prerequisite for achieving desired mechanical and physical characteristics. In this review article, current development on the processing, structure, and mechanical properties of polymer nanocomposites reinforced with respective layered silicates, ceramic nanoparticles and carbon nanotubes will be addressed. Particular attention is paid on the structure–property relationship of such novel high-performance polymer nanocomposites.

Structural and mechanical properties of polymer nanocomposites

Inspired by nature, self-healing materials represent the forefront of recent developments in materials chemistry and engineering. This review outlines the recent advances in the field of self-healing polymers. The first part discusses thermodynamic requirements for self-healing networks in the context of conformation changes that contribute to the Gibbs free energy. The chain flexibility significantly contributes to the entropy changes, whereas the heat of reaction and the external energy input are the main contributors to enthalpy changes. The second part focuses on chemical reactions that lead to self-healing, and the primary classes are the covalent bonding, supramolecular assemblies, ionic interactions, chemo-mechanical self-healing, and shape memory polymers. The third part outlines recent advances using encapsulation, remote self-healing and the role of shape memory polymers. Recent developments in the field of self-healing polymers undeniably indicate that the main challenge will be the designing of high glass transition (Tg) functional materials, which also exhibit stimuli-responsive attributes. Build-in controllable hierarchical heterogeneousness at various length scales capable of remote self-healing by physical and chemical responses will be essential in designing future materials of the 21st century.

Self-healing polymeric materials

Autonomous healing of damage is a common phenomenon in living organisms but is hardly ever encountered in synthetic materials. Disulfide chemistry is used to introduce a self-healing ability in a covalently cross-linked rubber. Autonomous healing of a cut takes place at moderate temperatures and leads to full recovery of mechanical properties. This result is achieved by introducing disulfide groups in the network that are able to exchange, leading to renewal of cross-links across the damaged surfaces. The healing process can be repeated many times. The combination of their unique self-healing properties and applicability for a large variety of polymers makes this approach ideal for coatings.

Self-Healing Materials Based on Disulfide Links

Effect of in situ prepared silica nano-particles on non-isothermal crystallization of polypropylene

The global plastics production has increased annually and a substantial part is used for packaging (in Europe 39%). Most plastic packages are discarded after a relatively short service life and the resulting plastic packaging waste is subsequently landfilled, incinerated or recycled. Laws of several European and Asian countries require that plastic packaging waste collected from households has to be sorted, reprocessed, compounded and reused. These recycling schemes typically produce milled goods of poly(ethylene terephthalate) (PET), poly(ethylene) (PE), isotactic poly(propylene) (PP), mixed plastics, and agglomerates from film material. The present study documents the composition and properties of post-consumer polyolefin recyclates originating from both source separation and mechanical recovery from municipal solid refuse waste (MSRW). The overall composition by Fourier transform-infrared (FT-IR) spectroscopy and differential scanning calorimetry (DSC) were determined and compared with the sorting results of the sorted fractions prior to the reprocessing into milled goods. This study shows that the collection method for the plastic packaging waste has hardly any influence on the final quality of the recyclate; however, the sorting and reprocessing steps influence the final quality of the recyclate. Although the mechanical properties of recyclate are clearly different than those of virgin polymers, changes to the sorting and reprocessing steps can improve the quality.

Assessment of plastic packaging waste : material origin, methods, properties

Poly(butylene terephthalate) (PBT) vitrimers were prepared by reactive extrusion from industrial PBT thermoplastics using Zn(II)-catalyzed addition and transesterification chemistry. PBT thermoplastics are characterized by a high degree of crystallinity, high melting temperature, and high crystallization rate, but right above their melting temperature their mechanical resistance disappears and they show a tendency to drip. We compared −OH and −COOH end-group additions on epoxies in the presence of two different catalysts: 2-methylimidazole (2-MI) and zinc acetylacetonate (Zn(acac)2). With 2-MI, chain extension reactions were efficiently catalyzed in a few minutes at 270 °C, but no gelation was observed. With Zn(acac)2, −COOH addition and transesterification led to efficient cross-linking within a few minutes at 270 °C. Such cross-linked material combines the crystalline properties of PBT and dimensional stability above the melting temperature. PBT materials cross-linked through epoxy-vitrimer chemistry ar...

/pdf/cross-linking-of-poly-butylene-terephthalate-by-reactive-2ct20u2pj2.pdf

Cross-Linking of Poly(butylene terephthalate) by Reactive Extrusion Using Zn(II) Epoxy-Vitrimer Chemistry

The solid-state structure and yield behavior of isotactic polypropylene (i-PP) containing the nucleating/clarifying agent 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (DMDBS) was investigated in the additive concentration range 0−1 wt %. The raise of the crystallization temperature of i-PP caused by addition of 0.2 wt % and more of the additive led to an increase in the polymer lamellar thickness, which, in turn, resulted in an increase of the yield stress at constant aging time. Both the strain-rate dependence of the yield stress and the rate of increase of the yield stress upon physical aging of compression-molded samples were not influenced by the addition of DMDBS. Analysis of the experimental data by means of the Eyring theory for thermally activated processes resulted in an average shear activation volume of 2.21 nm3. The dependence of the yield stress on the additive concentration was in gratifying agreement with the previously reported monotectic phase behavior of the i-PP/DMDBS system.

Han Goossens

Papers

Self-Healing Materials Based on Disulfide Links

Effect of in situ prepared silica nano-particles on non-isothermal crystallization of polypropylene

Assessment of plastic packaging waste : material origin, methods, properties

Cross-Linking of Poly(butylene terephthalate) by Reactive Extrusion Using Zn(II) Epoxy-Vitrimer Chemistry

Mechanical Properties of Sorbitol-Clarified Isotactic Polypropylene: Influence of Additive Concentration on Polymer Structure and Yield Behavior