Joachim Rösch

Polymers from renewable resoureces: polyester resins and blends based upon anhydride-cured epoxidized soybean oil

SummaryA broad range of crosslinked polyesters were prepared by curing epoxidized soybean oil with various dicarboxylic acid anhydrides in the presence of cure catalysts such as tertiary amines, imidazoles, or aluminum acetylacetonate. The mechanical and thermal properties of the casting resins were dependent upon the type of anhydride. While the anhydrides of hexahydrophthalic acid, succinic acid, and norbornene dicarboxylic acid yielded highly flexible rubbery materials with glass transition temperatures below room temperature, the more rigid anhydrides of maleic and phthalic acid gave amorphous stiff polyesters with higher glass transition temperatures varying between 43 and 73°C. When the cure reaction was carried out in polypropylene melts, multiphase polymers were formed containing polyester phases dispersed in the continuous polyolefin matrix.

The role of core/shell-microparticle dispersions in polypropylene/polyamide-6 blends

SummaryReactive blending of 70 vol.-% polypropylene (PP) and 30 vol.-% polyamide-6 (PA-6) was performed in the presence of various amounts of succinic-anhydride-functional elastomers which are immiscible with both blend components. Characteristic morphological feature of the resulting multiphase polymer blends was a continuous polypropylene matrix containing dispersed core/shell microparticles with rigid polyamide-6 core and soft elastomer shell. Accumulation of the elastomer component at the polypropylene/polyamide-6 interface and reaction of the succinic anhydride of the elastomer with the amine-endgroups of PA-6 enhanced PA-6 dispersion and proved to be the key to unusual property synergisms. In contrast to the conventional soft maleicanhydride-grafted EPM elastomer (EPM-g-MAH), the stiffer maleic-anhydride-grafted poly[styrene-b-(ethene-co-butene-1)-b-styrene] (SEBS-g-MAH) was much more efficient as blend compatibilizer and gave PP/PA-6 blends with greatly improved strength and toughness without sacrificing stiffness.

Syntheses of mono(1,3-oxazolin-2-yl)-terminated oligopropene macromonomers and novel polymers containing oligopropene side chains

SummaryMono(1,3-oxazolin-2-yl)-terminated atactic oligopropene with Mn=710g/mol was derived in high yields from monoester-terminated oligopropene via reaction with 2-aminoethanol and subsequent Ti(OC4H9)4-catalyzed dehydration at 180°C. Cationic bulk polymerization of this novel macromonomer, initiated with 2 mol% methyl-4-nitrobenzenesulfonate at 200°C, afforded high molecular weight poly[N-oligopropene-1-carbonyl]-ethyleneimine]. Grafting of mono(1,3-oxazolin-2-yl)-terminated oligopropene with poly(ethene-co-methacrylic acid), containing 3 mol% methacrylic acid, by heating both components for 15minutes at 220°C yielded novel ethene copolymers containing 41wt% esteramide-coupled oligopropene as side chains.

Mechanical properties of organosolv-lignin-filled thermoplastics

SummaryOrganosolv lignin was used as organic filler for polypropylene (PP) and poly(ethene-co-vinylacetate) (EVA) containing 13wt-% vinylacetate. As a function of the lignin content, which was varied between 0 and 30wt-%, mechanical properties such as Youngs modulus, yield stress, fracture stress, and elongation at break of the thermoplastic lignin-based compounds were measured. Both lignin-filled thermoplastics exhibit pronounced matrix reinforcement with increasing lignin content. Due to better interfacial adhesion between lignin and EVA, 30wt-% lignin addition to EVA doubles Youngs modulus without sacrificing high elongation at break.

Creep measurements on “in situ” compatibilized polypropylene/polyamide-6 blends

SummaryRheological properties of Polypropylene/Polyamide-6 blends at different degrees of compatibilization were studied at 240°C. The compatibilizing agent was synthesized in situ during the mixing procedure. Creep measurements at constant stress levels were performed on a Rheometrics Stress Rheometer.The morphology of the blends was determined by scanning and transmission electron microscopy before and after the shear experiments. No changes of the morphology occurred during the experiments.In the creep experiments the flow zone was reached. Data of that region such as zero shear viscosity, creep compliance and terminal retardation time were determined.The values of these quantities increased with increasing amount of the compatibilizing agent.

Anisotropic polyaramide/polyol dispersions—new components for the preparation of polyurethane microcomposites

SummaryPolymerization of N-(p-aminobenzoyl)-caprolactam (PAC) in melts of polyols such as dihydroxy-terminated oligo(oxytetramethylene) with Mn=2000 g/mol at 200°C afforded stable dispersions of poly(p-phenylenebenzamide) whiskers in polyol. In spite of the low molecular weight of the polyaramide, which was isolated by solvent extraction, the microparticles are efficient reinforcing agents of polyurethanes because of the excellent interfacial adhesion resulting from covalent attachment of the polyols onto the microparticle surfaces. The role of the competing formation of p-aminobenzoate-terminated polyols via esterification of PAC was investigated. Morphological and mechanical properties of polyurethane microcomposites, prepared from poly(p-phenylenebenzamide)/poly(oxytetramethylene)diol dispersions and 4,4′-diisocyanatodiphenylmethane, were determined as a function of the microparticle content. When compared to conventional polyurethanes, containing equivalent amounts of spherical organic and inorganic fillers, the microcomposites give higher Youngs modulus, tensile strength without sacrificing high elongation at break.

Dynamic mechanical properties of semi-interpenetrating networks based on poly(styrene-co-maleic anhydride)

SummarySemi-interpenetrating networks based on linear anionic polystyrene (PS) and poly(styrene-co-maleic anhydride) P(ScoMA) of low MA content are prepared by crosslinking the P(ScoMA) with 4,4′-diphenylmethanediamine (DPMDA). It is demonstrated by dynamic mechanical analysis and by DSC that immiscible semi-IPNs are obtained for MA contents greater 5 wt.-%. In miscible semi-IPNs the relaxation of free PS chains is observed as a second maximum in the loss tangent at higher temperatures. The position of this maximum is shifted to higher temperatures for a polystyrene of molecular weight 500000 compared to a polystyrene of molecular weight 150000. The experimental temperature shift is in good agreement with a M3 dependence of the terminal relaxation time. In addition the temperature of this second tan δ maximum is shifted to higher temperatures with increasing crosslink density. Again the shift is in good agreement with the theoretical prediction of an increased terminal relaxation time of the relaxing chains with decreasing tube diameter.

Dynamic mechanical properties of semi-interpenetrating networks based on poly(styrene-co-maleic anhydride): 3. Poly(2,6-dimethyl-1,4-phenylene ether)-cross-poly(styrene-co-maleic anhydride)

Semi-IPNs based on linear poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and diamine crosslinked poly(styrene-co-maleic anhydride) (PScoMA) copolymers containing small amounts of maleic anhydride (PSA=4.7wt.-% MA, PSB=5.8 wt-% MA) are studied with respect to the influence of cross-linking on the phase behavior. Temperature-dependent dynamic mechanical analysis (DMA) and DSC show that the semi-IPNs prepared from concentrated solution show weak crystallinity of the PPE phase. After heating above the PPE melting transition the semi-IPNs remain amorphous and the relaxation in the glass transition region as well as the terminal relaxation of the free PPE chains in the network is studied as a function of PPE concentration and network density.

Organic microcomposites via reactive processing

The in-situ formation of dispersed polyaramide whiskers during melt processing of polymers represents a new route to thermoplastic and elastomeric organic microcomposites. When N-(p-amino-benzoyl)-caprolactam (PAC) is injected into melts of high molecular weight polyamide-6 or dihydroxy-terminated poly(oxytetramethylene) liquid rubber, stable dispersions of polymeric whiskers are formed. At temperatures around 200°C, PAC polymerization takes place exclusively through attack of the PAC amine group at the exocyclic carbonyl group, thus eliminating caprolactam and forming whiskers being composed of highly crystalline poly(p-phenylenebenzamide). With increasing polymerization temperature, the elimination reaction is accompanied by the competing attack of the amine group at the endocyclic carbonyl group of the caprolactam ring system. This side-reaction causes ring-opening, thus incorporating 6-aminocaproic structural units into the polyaramide backbone. Moreover, the condensation reaction of PAC and N-acyl-caprolactam-functional whisker surfaces with hydroxy- or amine-endgroups affords steric stabilization of the dispersions and excellent interfacial adhesion of the microcomposites. This covalent bond formation between matrix polymer and dispersed in-situ formed polyaramide whiskers is the key to unusual property synergisms of such organic microcomposites. In most cases, small amounts of PAC as additives during processing are sufficient to improve stiffness and strength without sacrificing toughness. Morphologies, mechanical properties, and the basic structure/property relationships of in-situ formed polyaramide-reinforced polyamide-6 and of polyurethanes elastomers prepared from novel anisotropic polymer polyol dispersions and diisocyanates are reported as a function of the PAC content and polymerization conditions