Ein fundiertes Verständnis der Mechanismen der Gummi-Vulkanisation von Dien-Kautschuken ist noch immer eine der größten Herausforderungen in der Chemie und Technologie der Elastomere. Die Schwefelvulkanisation von Elastomerwerkstoffen ist ein seit langem verwendeter, aber dennoch sehr anspruchsvoller Prozess, mit dessen Hilfe moderne Reifen hergestellt werden. Bei dieser chemischen Reaktion spielt Zinkoxid, zusammen mit den anderen Hilfsstoffen der Schwefelvulkanisation eine entscheidende Rolle. Um die Produkteigenschaften von mit Schwefel vulkanisierten Elastomermaterialien zu verbessern, sollten die Mechanismen der chemischen Vernetzung - und insbesondere auch die Rolle von Zink enthaltenden Verbindungen bei der Vulkanisationsreaktion besser verstanden werden. Zum Beispiel könnte das Eigenschaftsprofil von Reifen durch die Ausbildung von geeigneten Netzwerken aus Schwefel oder anderen Netzknoten optimiert werden. Nitrilkautschke aus der Klasse der Spezialelastomere und die meisten nicht-Tire- Kautschuk in der ganzen Welt eingesetzt, wecken ein großes Interesse der Forschung wegen ihrer einzigartigen Vulkanisationschemie bei der Vernetzung mittels Zinkverbindungen und wegen der besonderen Eigenschaften der dadurch erzeugten Elastomerwerkstoffe. In dieser Arbeit wurde besonderes Augenmerk darauf gelegt, die Rolle von verschiedenen Zinkverbindungen in der Schwefelvulkanisation von carboxylierten Nitrilkautschuken zu verstehen. In der vorliegenden umfangreichen und eingehenden Untersuchung konnte die Ausbildung einer weiteren Polymerphase im Elastomer nachgewiesen werden. Durch dieses Ergebnis kann nun das dynamische mechanische Verhalten von solchen Polymerwerkstoffen besser verstanden werden. Teile dieser Arbeit beschäftigen sich mit der Erforschung der Rolle von Zinkchlorid bei der Vernetzung von Nitrilkautschuken. Hierzu wurde festgestellt, dass Zinkchlorid einen besonderen Einfluss auf die chemische Vernetzung des NBR aufweist, auch in Abwesenheit anderer Vernetzungs- oder Vulkanisationsadditive. Die so vernetzten Elastomere weisen ein stark hydrophiles Verhalten auf, im Gegensatz zu den allgemeinen Eigenschaften solcher Elastomerwerkstoffe. Eine detaillierte Analyse dieser neuartigen Netzwerkstruktur, gebildet durch eine Koordinationsbindung zwischen dem Zinkatom des Zinkchlorids und dem Nitrilkautschuk, wurde durchgeführt. Carboxylierter Nitrilkautschuk (XNBR) wurde ebenfalls eingesetzt, um funktionale Kautschukmischungen mit neuartigen flammhemmenden Eigenschaften zu entwickeln. Zu dieser Thematik wurden Zink enthaltende Doppelhydroxide (Layered Doube Hydroxides, LDH) als multifunktionale Füllstoffe in XNBR-Kautschuk eingesetzt. Neben dem Flammschutzverhalten zeigt LDH einzigartige Eigenschaften als verstärkenden Füllstoff und gleichzeitig als aktivierendes Additiv für die Schwefelvulkanisation. Eine weitere Zink enthaltenden Verbindung, Zinkstearat, wurde eingesetzt um mechanoadaptive elastomere Materialien durch gezieltes Einstellen des kristallinen bzw. amorphen Charakters dieser Verbindung zu entwickeln. Dies könnte einen wichtigen Beitrag zur Entwicklung zukünftiger Reifenmaterialien mit intrinsisch adaptiven Eigenschaften liefern.

Sustainable development has become a global goal and the utilization of bioresources is a key way to achieve this crucial goal. Glyoxylic acid-functionalized lignin (GA-lignin) is one of the novel lignin derivatives extracted from beech wood (hardwood) and has great potential to be an industrially important bioresource. In this thesis work, epoxies prepared by GA-lignin and polyethylene glycol diglycidyl ether (PEGDE) were studied, and the feasibility to prepare smart materials based on these epoxies was explored. Three smart properties, including self-healing properties, thermoelectric properties and piezoelectric properties, were successfully embedded in the GA-lignin-based materials. Many applications are envisioned based on the unique properties of GA-lignin and the value-added materials based on this lignin, including adhesives, hydrogels, flexible electronics, etc. In the first part of this thesis work, different pathways were performed to synthesize GA-lignin/PEGDE epoxies: solvent-free pathway, NaOH solution pathway, DMSO solvent pathway and 1,4-dioxane solvent pathway. The elastomeric epoxy with 50wt% lignin was synthesized following the solvent-free pathway showing mild self-healing properties. The introduction of NaOH solution was found to have the ability to enhance self-healing properties. The epoxy obtained following the dioxane solvent pathway had a similar structure to the original one without any medium, therefore dioxane was chosen to be the solvent for further fabrication of nanocomposites. In the second part, two kinds of GA-lignin-based nanocomposites were fabricated with dioxane as solvent. The first kind of nanocomposite was filled with reduced graphene oxide nanoparticles (rGO). 1wt%, 2wt% and 3wt% of rGO nanoparticles were dispersed into the 50wt% GA-lignin/PEGDE epoxy matrix. Power factor analysis was performed, and the potential of GA-lignin-based thermoelectric nanocomposite was verified. The second nanocomposite was filled with barium titanate nanoparticles (BaTiO3). 7.5wt% and 15wt% of BaTiO3 were dispersed into the epoxy matrix and the piezoelectric response test was performed to show the embedded piezoelectric properties. / Hållbar utveckling har blivit ett globalt mål och användningen av bioresurser är ett viktigt sätt att uppnå detta avgörande mål. Glyoxylsyra-funktionaliserad lignin (GA-lignin) är en av de nya ligninderivaten extraherade från bokträ (lövträ) och har stor potential att vara en industriellt viktig bioresurs. I detta examensarbete undersöktes epoxier framställda av GA-lignin och polyetylenglykol-diglycidyleter (PEGDE), och möjligheten att framställa smarta material baserade på dessa epoxier utforskades. Tre "smarta egenskaper" integrerades framgångsrikt i GA-lignin-baserade material, inklusive självläkande egenskaper, termoelektriska egenskaper och piezoelektriska egenskaper. Många tillämpningar förutspås baserat på de unika egenskaperna hos GA-lignin och de mervärdesmaterial som baseras på detta lignin, inklusive lim, hydrogeler, flexibel elektronik, osv.I den första delen av detta examensarbete genomfördes olika metoder för att syntetisera GA-lignin/PEGDE-epoxier: en metoden utan lösningsmedel, en metod med NaOH-lösning, en metod med DMSO-lösningsmedel och en metod med 1,4-dioxan som lösningsmedel. Den elastiska epoxin med 50 viktprocent lignin syntetiserades genom den lösningsmedelsfria metoden och uppvisade milda självläkningsegenskaper. Införandet av NaOH-lösningen visade sig kunna förbättra självläkningsegenskaperna. Epoxin som erhölls genom metoden med dioxan som lösningsmedel hade en liknande struktur som den ursprungliga epoxin utan något medium, därför valdes dioxan som lösningsmedel för vidare tillverkning av nanokompositer. I den andra delen tillverkades två typer av GA-lignin-baserade nanokompositer med dioxan som lösningsmedel. Den första typen av nanokomposit fylldes med reducerade grafenoxid-nanopartiklar (rGO). 1 viktprocent, 2 viktprocent och 3 viktprocent rGO-nanopartiklar disperserades i matrisen av 50 viktprocent GA-lignin/PEGDE-epoxi. En analys av effektfaktorn utfördes och potentialen hos GA-lignin-baserade termoelektriska nanokompositer verifierades. Den andra nanokompositen fylldes med bariumtitanat-nanopartiklar (BaTiO3). 7,5 viktprocent och 15 viktprocent BaTiO3 disperserades i epoximatrixen och en test för piezoelektrisk respons genomfördes för att visa de inbäddade piezoelektriska egenskaperna.

No description available.

Synthesized polymer from bio-based and renewable resources reported as an attractive substitution for fossil-fuel based polymers. Therefore, this work has focused on using sustainable material for production of elastomers to reduce the environmental impact of fossil-based elastomers and overcome the shortage of non-renewable fuels. In this research (as thesis work) bio-based elastomers (resins synthesized by reacting of lactic acid with 1,4-butanediol in presence of toluene and methanesulfonic acid as solvent and catalyst, respectively. To trace the reaction, the Fourier transform infrared (FT-IR) spectrometer was used for structural characterization of the products. Furthermore, the degree of reaction followed by measuring of the acid value using alkali titration method. To achieve the desirable results, both condensed resins were reacted with caprolactone for ring opening polymerization. The produced resins were finally functionalized using methacrylic anhydride and the structures and thermal properties of the produced resin were characterized using FT-IR, DSC and TGA. In addition, the viscoelastic properties of the resins were investigated using dynamic mechanical analysis (DMA); and elasticity and viscosity of the elastomers measured using tensile testing machine and viscometer, respectively. The important result such as viscosity showed the resin with chain length n= 5 had higher viscosity when compared to the resin chain length n=3. This makes the resin (n=5) suitable for applications that need high viscosities. The resin with chain length n=3 had lower viscosity that is suitable for processing at room temperature. Furthermore, the tensile strength results show maximum elongation for resin with chain length n=3 is almost double compared to resin with chain length n=5. The results showed that these bio-based resins are compatible with petrochemical-based resins, due to desirable rubbery properties, melting temperature, also acceptable viscosity, and other good mechanical properties as will be mentioned below.

No description available.

<p>Silicone polymers, particularly PDMS (poly(dimethylsiloxane)) exhibit a wide range of exceptional properties including optical transparency, biostability, hydrophobicity and excellent oxygen transmissibility that make them extremely useful in a wide range of applications, particularly as biomaterials. Current methods for the preparation of silicone elastomers have been well documented, however, silicone elastomers are thermoset materials and once cured, they cannot be reformed without chemical intervention. The properties of silicones that make them a popular material choice in a wide variety of industries also make them un-responsive and non-reusable often limiting their application to one primary purpose.</p> <p>This thesis aims to further understand the mechanisms of silicone polymer chain interactions and how the chemistry of polymer modification can alter the mechanical and chemical properties of materials. The effects of distinctive functional groups (coumarin) on silicone chains to allow for both the formation of thermoplastic silicone elastomers and stimuli-responsive elastomers for reversible crosslinking are explored.</p> <p>A companion study examined a different way to form silicone elastomers. The Piers- Rubinsztajn reaction was used to create elastomers and foams rapidly and under relatively mild conditions using very small quantities of the catalyst B(C6F5)3. The factors required to create – on demand – a foam or an elastomer, and the strategies to control physical properties, including bubble density and modulus, are explored.</p> <p>Silicone foams that were structured in a completely different way are described. Allyl- modified PEG (poly(ethylene glycol)) was found to structure foam mixtures precure. The product foam after cure was amphiphilic, due to the presence of both silicone and PEG constituents. The origins of bubble stabilization and the ability to control foam properties are described.</p> / Doctor of Science (PhD)

In the project, our purpose is the synthesis of segmented block copolymers using novel selectively reacting bi-functional coupling agents which have recently been developed by Jakisch at al. Both couplers have one oxazoline group that reacts with carboxylic groups and one oxazinone group that reacts with hydroxyl or amino groups. It was intended to synthesize segmented block copolymers by combination of amino or hydroxyl terminated pre-polymers and carboxylic terminated chain extenders using the above mentioned coupling agents. Several prepolymers were selected such as hydroxyl terminated liquid polybutadiene (PBD-OH), hydroxyl terminated liquid natural rubber (LNR) and amino terminated liquid polybutadiene-b-acrylonitrile (PBAN) and poly(propylene glycol)-bis(2-aminopropylether) (PPO). They were selected as soft polymer segments in the segmented block copolymers aimed for. Additionally, various di-carboxylic acids were chosen as chain extenders. The resulting block copolymers are phase separated materials with a crystalline hard phase. This was demonstrated by two glass transition temperatures corresponding to the soft and hard segments and various melting regions of the hard chain extenders. For these new materials, the controlled phase separation morphology in nano-size was evidenced by TEM. A hard domain size of about 2-5 nm surrounded by a soft matrix was observed on the micro-photographs. This is consistent with the low hard segment content and the segment alternation (A-B)n in multi-block copolymers. With respect to the mechanical properties, a relationship between tensile strength and the average molar mass of the block copolymers was found out. The samples behave as rubber-like thermoplastic materials. The tensile properties depend on the degree of polymerization and the polymer distribution. The reinforcement ability of the hard domains in a physical network was achieved as expected. As a consequence, the obtained final products have mechanical properties like a typical elastomeric material.

Die Arbeit widmet sich der Problemstellung der Substitution des Primärrohstoffes Kautschuk durch Rezyklate in Form von Gummimehl. Die für das innerbetriebliche Recycling von Kleinchargen technischer Elastomere hier eigens konzipierte und umgesetzte Warmmahltechnologie dient zur Herstellung von Gummimehlrezyklat hoher Qualität aus Lkw-Altreifen. Hinsichtlich ausgewählter Verarbeitungs- und Materialkennwerte von Mischung und Vulkanisat werden die Auswirkungen der Zugabe von Rezyklaten und die wesentlichen Einflussgrößen des den Rezyklaten zugrunde liegenden Aufbereitungsprozesses – das Kryogenmahlverfahren bzw. die neu entwickelte Warmmahltechnologie – herausgearbeitet. Abschließend erfolgt die Formulierung materialspezifischer Versagensmechanismen, die das entsprechende Aufbereitungsverfahren der Rezyklate berücksichtigen. / The work is devoted to the problem of the substitution of the primary raw material rubber by recycled materials in the form of rubber powders. For the in-plant recycling of small batches of technical elastomers an ambient grind technology was specifically designed and implemented for making rubber powders of high quality out of used truck tires. In terms of selected processing and material characteristics of the mixture and the vulcanizate the influences of the addition of recycled material and the significant factors affecting the regeneration process underlying these recyclates – the cryogenic grinding versus the new developed ambient grinding technology – were worked out. Finally, the material-specific failure mechanisms were formulated, incorporating the regeneration process of such regenerated materials.

In the project, our purpose is the synthesis of segmented block copolymers using novel selectively reacting bi-functional coupling agents which have recently been developed by Jakisch at al. Both couplers have one oxazoline group that reacts with carboxylic groups and one oxazinone group that reacts with hydroxyl or amino groups. It was intended to synthesize segmented block copolymers by combination of amino or hydroxyl terminated pre-polymers and carboxylic terminated chain extenders using the above mentioned coupling agents. Several prepolymers were selected such as hydroxyl terminated liquid polybutadiene (PBD-OH), hydroxyl terminated liquid natural rubber (LNR) and amino terminated liquid polybutadiene-b-acrylonitrile (PBAN) and poly(propylene glycol)-bis(2-aminopropylether) (PPO). They were selected as soft polymer segments in the segmented block copolymers aimed for. Additionally, various di-carboxylic acids were chosen as chain extenders. The resulting block copolymers are phase separated materials with a crystalline hard phase. This was demonstrated by two glass transition temperatures corresponding to the soft and hard segments and various melting regions of the hard chain extenders. For these new materials, the controlled phase separation morphology in nano-size was evidenced by TEM. A hard domain size of about 2-5 nm surrounded by a soft matrix was observed on the micro-photographs. This is consistent with the low hard segment content and the segment alternation (A-B)n in multi-block copolymers. With respect to the mechanical properties, a relationship between tensile strength and the average molar mass of the block copolymers was found out. The samples behave as rubber-like thermoplastic materials. The tensile properties depend on the degree of polymerization and the polymer distribution. The reinforcement ability of the hard domains in a physical network was achieved as expected. As a consequence, the obtained final products have mechanical properties like a typical elastomeric material.

Puncture resistance is among the major mechanical properties often required for protective clothing, especially in the medical sector. However the intrinsic material parameters controlling puncture resistance of protective materials are still unknown. Therefore, the purpose of this work is to study the mechanism and mechanical behaviors of puncture resistance of protective clothing materials to various probe types. A better understanding of puncture mechanics will be helpful to develop suitable methods to evaluate the puncture resistance and to predict the failure of protective clothing materials. The thesis includes 4 articles which expose two major phases in this study. Article I and II studied the mechanics and mechanisms of puncture by conical and cylindrical probes used in the standard test methods (ASTM F1342 and ISO 13996). The results show that the punctures of rubber membranes by conical and cylindrical probes are controlled by a maximum local deformation (or puncture failure strain) that is independent of the probe geometry. The puncture strengths of elastomer membranes are much lower than their tensile and biaxial strengths. In addition, a simpler cylindrical probe can be used in the place of the costly conical probe required by the ASTM standard and still provides a quantitative characterization of puncture. Actually, since 2005, an alternative method B had been added to F1342 ASTM with 0.5 mm-diameter rounded-tip cylindrical probe. Furthermore, the puncture probes used in the ASTM F1342 are very different to the actual pointed objects (medical needle, pointed tip of knife... ) and cannot accurately characterize the puncture resistance to real objects. Therefore, in the second step, the mechanics and mechanisms of puncture by medical needles were studied. Article III shows that the puncture by sharp-pointed objects like medical needles is very different from the puncture by conical probes used in the ASTM standard test. For medical needles, the puncture resistance involves cutting and fracture energy of material. Using the fracture mechanics, based on the change in strain energy with the change in fracture surface, the fracture energy in puncture was estimated. This calculation assumes that there is no friction between the needle tip and fracture surface. However, even with the application of a lubricant on the needle surface, the effect of friction on the puncture process cannot be totally eliminated, preventing the determination of the material fracture energy. Therefore, Article IV has described a method, similar to that of Lake and Yeoh for cutting to access the precise value of fracture energy in puncture of rubbers by sharp-pointed objects. The method allows substantially eliminating the effects of friction on the evaluation of the fracture energy involved in the puncture process.