Search results for " Plastics"

Molekulare Deutung der Umwandlungswärmen bei den Modifikationsübergängen des n-Tritriacontans

1978

Ausgehend von dem durch die Experimente nahegelegten Bild wurden Modellrechnungen angestellt, um die fur die drei Modifikationsumwandlungen desn-Tritriacontans gemessenen Umwandlungsenthalpien und -entropien molekular zu deuten.

Kommentar zu der Arbeit von Hans Craubner: „Lösefraktionierapparatur für makromolekulare Stoffe”

1976

Cyclopolymerisation bei zweifach-ungesättigten Monomeren

1967

Das Prinzip der Cyclopolymerisation wird erlautert; an Beispielen wird gezeigt, welche Verbindungen zu intra-intermolekularen Wachstumsschritten befahigt sind. Der Gehalt an cyclischen Grundbausteinen in den gebildeten Polymerisaten hangt auser von der Struktur der Monomeren auch von den Polymerisationsbedingungen ab. Es werden stereochemische Fragen behandelt, die im Zusammenhang mit Ringschlusreaktionen an 6- und hohergliedrigen Ringen auftreten. Chemische Umsetzungen an Cyclopolymeren konnen zu Copolymeren mit bestimmter Zusammensetzung und regelmasigem Aufbau fuhren.

Chemical Routes Toward Multicompartment Colloids

2012

The search for mimicking natural living and non-living systems with synthetic products leads to the fabrication of advanced colloidal morphologies with hierarchical micro- and nanostructures. Different chemical routes toward the synthesis of colloids with complex morphologies are presented and a tentative analogy between these routes and the four basic arithmetic operations is proposed.

Comparison of Different Processing Methods to Prepare Poly(lactid acid)–Hydrotalcite Composites

2013

The effect of the compounding method on the morphology and on the properties of poly(lactic acid) (PLA)-hydrotalcite (HT) composites was studied. Moreover, the influence of two different kinds of HT - organically modified (OM-HT) and unmodified (U-HT) - and their concentration was evaluated. The composites were prepared using either a single screw extruder (SSE), a counter rotating twin-screw compounder (TSC) or a corotating twin-screw extruder (TSE). The prepared materials were characterized by scanning electron microscopy, gel permeation chromatography (GPC) analysis, mechanical and rheological measurements. The results indicated that the best morphology, i.e., particles dimension and dis…

Torque rheometry investigation of model transreactions involving condensation polymers: I. Polyesters

2005

The chemical transformations taking place when poly(ethylene terephthalate) (PET) or poly(ethylene naphthalate) (PEN) are blended in the melt with different low molar mass substances containing hydroxyl, carboxyl, or amine functional groups have been investigated as models of the transreactions, undergone by the polyesters in reactive blending operations. The polyester molecular weight changes caused by the alcoholysis, acidolysis, aminolysis, and esterolysis reactions have been monitored by torque-rheometry, using a Brabender Plasticorder static mixer. The degradation of the polyesters by hydrolysis was also studied, under similar conditions, by the addition of a water-releasing substance …

Synthesis, characterization and fine-tuning of bimodal poly(organosiloxane) nanoparticles

2010

Abstract The acid catalyzed sol–gel type synthesis of polyorganosiloxane core-shell nanoparticles with removable PDMS core in aqueous dispersion leads to the inherent formation of a bimodal size distribution with smaller spheres having approximately 26 nm radii and larger nanoparticles with 60 nm in radius. The origin of the self-organized bimodality is investigated and finally attributed to a combination of stabilization of the growing particles due to i) a miniemulsion-type stabilization by the ultrahydrophobe PDMS and ii) by surface co-stabilization by the employed surfactant. The significant influence of temperature, pH, stirrer speed and amount of the surfactant on the particle sizes a…

Long-Chain Branched Poly(Lactide)s Based on Polycondensation of AB2 -type Macromonomers

2012

A series of long-chain branched poly(d-/l-lactide)s is synthesized in a two-step protocol by (1) ring-opening polymerization of lactide and (2) subsequent condensation of the preformed AB2 macromonomers promoted by different coupling reagents. The linear AB2 macromonomers are prepared by Sn(Oct)2-catalyzed ROP of D- and L-lactide with 2,2-bis(hydroxymethyl)butyric acid (BHB) as an initiator. Optimization of the polymerization conditions allows for the preparation of well-defined macromonomers (Mw/Mn = 1.09–1.30) with adjustable molecular weights (760–7200 g mol−1). The two-step approach of the synthesis comprises as well the coupling of these AB2 macromonomers and hence allows precise contr…

On the use of PET-LCP copolymers as compatibilizers for PET/LCP blends

1996

Copolyesters of poly[ethylene terephthalate) (PET) with a liquid crystalline polymer (LCP), SBH 1:1:2, have been synthesized by the polycondensation, carried out in the melt at temperatures up to 300 degrees C of sebacic acid (S), 4,4'-dihydroxybiphenyl (B), and 4-hydroxybenzoic acid (H) in the presence of PET. The PET-SBH copolyesters have been characterized by differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, etc., and the relationships between properties and preparation conditions are discussed. The copolyesters show a biphasic nature, which is more evident for the products synthesized with a thermal profile comprising relatively lower temperatures (220-…

Aliphatic Hyperbranched Copolyesters by Combination of ROP and AB2-Polycondensation

2005

Hyperbranched aliphatic copolyesters have been prepared by the copolymerization of e-caprolactone and 2,2-bis(hydroxymethyl)butyric acid (AB 2 -monomer), catalyzed by (i) HfCl 4 (THF) 2 and (ii) diphenylammonium trifluoromethanesulfonate (DPAT), respectively. In both cases, copolymerization by combined ROP/AB 2 -Polycondensation was achieved. The degree of branching (DB) and consequently the density of functional groups of the resulting copolyesters were controlled by the comonomer ratio in the feed. Molecular weights in the range M n =22 000-166 000 g mot -1 (GPC, PS standards) were obtained, with apparent polydispersity indices of 1.20 to 1.95. The DB was in the range 0.03-0.35. Remarkabl…