Search results for "Plastics"

Hydrogen-Bonded Aggregates of Oligoaramide−Poly(ethylene glycol) Block Copolymers

2010

Rod−coil copolymers with an oligomeric rod aggregate on a nanometer length scale, which is important for many applications like e.g. organic photovoltaics. However, this aggregation behavior and the driving forces such as hydrogen bonding and π−π interactions, as well as the role of side groups, are not yet fully understood. Here, we investigated these noncovalent interactions in oligo(p-benzamide)−poly(ethylene glycol) (OPBA−PEG) copolymers using solid-state NMR supported by wide-angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and polarization optical microscopy (POM). It was found that longer OPBAs form layered β-sheet-like aggregates and that these are stabilized …

Improvement of the mechanical properties of photo-oxidized films after recycling

2002

Mechanical recycling of post-consumer plastics gives rise, in most cases, to secondary materials with mechanical properties worse than those of the reclaimed polymer. This is mostly due to the thermomechanical treatment undergone during the melt reprocessing operations. In this work, low density polyethylene films have been photo-oxidized in artificial accelerated ageing conditions and then the brittle films have been melt reprocessed. It is shown that the secondary material, after reprocessing, shows mechanical properties, in particular elongation at break, better than those of the photo-oxidized films. This behaviour has been attributed to the fact that the melt reprocessing has the effec…

Some photochemical transformations of polymers

1969

Abstract Several light-induced reactions of polymers are described. The light-sensitive groups are part of the macromolecules. Photoisomerization of polyvinylbutyral produces a polymer with vinylbutyrate-groups. At exposure to light, furan and benzofuran are added to the carbonyl-groups of polyvinylbenzophenone. Polymers with azido-groups are prepared, which eliminate nitrogen at irradiation. Light-sensitive films can be cast from polymers with o-quinonediazide-groups.

Closed-loop recycling. A case study of films for greenhouses

2010

Abstract The degradation undergone by plastic films used for greenhouse coverage is the main cause of the worsening of the processability, of the mechanical properties and of the durability of secondary materials obtained by their recycling. This means that this secondary material cannot be processed to produce films for the same applications (closed-loop recycling). In this work different strategies are proposed to improve the processability, some mechanical properties and the resistance to photo-oxidation of these secondary materials. In particular, homopolymer blends or multilayer films where the secondary material is used in combination with virgin polymer give the best results.

Polydimethylsiloxanes with amylose side chains by enzymatic polymerization

1996

Maltoheptaonamide modified polydimethylsiloxane was prepared applying a simplified synthetic pathway in the derivatization sequence of the carbohydrate. The products were characterized by 13C NMR and FT-IR spectroscopy. The glucan side chains of these “sweet siloxanes” were elongated by enzymatic catalysis with potato phosphorylase.

Hyperbranched polymer architectures: From Flory's AB(f-1) polycondensates to controlled structures

2020

Abstract Celebrating the 100th anniversary of Staudinger's “macromolecular concept”, polymer scientists critically evaluate the past developments and future challenges of polymer science, asking: Quo vadis, Macromolecular Science? The main focus in Polymer Science has been on linear polymers or crosslinked systems (elastomers and thermosets) until the late 1980ies. The advent of dendritic polymers, i.e. dendrimers and hyperbranched polymers (HBPs) attracted wide-spread attention in the polymer community. This article gives a brief overview of the developments in the area of hyperbranched polymers and demonstrates that they have since become a novel class of polymer materials.

Intrinsic Viscosities of Polymer Blends and Polymer Compatibility: Self-Organization and Flory-Huggins Interaction Parameters

2018

Synthetic approaches to new polymers

1990

A plenary lecture should be an introduction into the main topic of the symposium and a review about the state of art. Therefore, in the first part of this presentation different possibilities for the preparation of new polymers are briefly discussed from a chemical point of view. Some selected examples from the literature show how methods of organic chemistry can be utilized for polymer science: new catalytic systems, new monomers, modification of polymers, new poly-reactions. In the second part, several polyelectrolytes are described: polymers with sec., tert. and quart. N-atoms in the main chain, block copolymers and block polyampholytes. The third part deals with the problems of rod-like…

Aliphatic Polyethers: Classical Polymers for the 21st Century.

2015

Polyethers-polymers with the structural element (R'-O-R)n in their backbone--are an old class of polymers which were already used at the time of the ancient Egyptians. However, still today these materials are highly important with applications in all areas of our life, reaching from the automotive and paper industry to cosmetics and biomedical applications. In this Review, different aliphatic polyethers like poly(epoxide)s, poly(oxetane)s, and poly(tetrahydrofuran) are discussed. Special emphasis is placed on the history, the polymerization techniques (industrially and in academia), the properties, the applications as well as recent developments of these materials.

Complete in-plane elastic characterisation under tensile tests of angle-ply laminates composed of polymer-matrix layers

2002

In this paper we present a new strategy to completely characterise the in-plane elastic properties of a large range of angle-ply laminates using only unidirectional tests. We consider laminates having the same number of identical plies in the α and – α directions. This new method uses some preceding results found by Verchery for orthotropic laminates, namely the conditions of existence of a specific direction ω, in which the shear-extension coupling is null. The characterisation of the laminate is then made using the results of three tensile tests: two in the orthotropy axes, and the third one in the ω direction, in order to have always a pure one-dimensional state of stress. We show that …