Morphological and Tribological Properties of PMMA/Halloysite Nanocomposites

From an environmental and cost-effective perspective, a number of research challenges can be found for electronics, household, but especially in the automotive polymer parts industry. Reducing synthesis steps, parts coating and painting, or other solvent-assisted processes, have been identified as major constrains for the existing technologies. Therefore, simple polymer processing routes (mixing, extrusion, injection moulding) were used for obtaining PMMA/HNT nanocomposites. By these techniques, an automotive-grade polymethylmethacrylate (PMMA) was modified with halloysite nanotubes (HNT) and an eco-friendly additive N,N′-ethylenebis(stearamide) (EBS) to improve nanomechanical properties involved in scratch resistance, mechanical properties (balance between tensile strength and impact resistance) without diminishing other properties. The relationship between morphological/structural (XRD, TEM, FTIR) and tribological (friction) properties of PMMA nanocomposites were investigated. A synergistic effect was found between HNT and EBS in the PMMA matrix. The synergy was attained by the phase distribution resulted from the selective interaction between partners and favourable processing conditions. Modification of HNT with EBS improved the dispersion of nanoparticles in the polymer matrix by increasing their interfacial compatibility through hydrogen bonding established by amide groups with aluminol groups. The increased interfacial adhesion further improved the nanocomposite scratch resistance. The PMMA/HNT-EBS nanocomposite had a lower coefficient of friction and lower scratch penetration depth than PMMA/HNT nanocomposite.Financial support by the EU Commission through Project H2020-686165-IZADINANO2INDUSTRY is gratefully acknowledged

Effects of chemical structure and morphology of graphene-related materials (GRMs) on melt processing and properties of GRM/polyamide-6 nanocomposites

In this work, different graphene-related materials (GRMs) and polyamide-6 (PA6) were melt compounded by twin screw extrusion. The GRMs prepared were graphene nanoplatelets (GNPs), graphene oxide (GO), reduced graphene oxide (rGO) and silane functionalised reduced graphene oxide (f-rGO). The GRMs had comparable lateral size (20-30μm), but different thickness and surface chemistry which resulted in different behaviour in processing of melt flow, maximum loading in the PA6 matrix (15%wt for GNPs, 10%wt for GO, 2%wt for rGO and 2.5%wt for f-rGO) as well as mechanical properties. A second extrusion phase produced formulations with lower concentration of GRMs. In the case of f-rGO/PA6, the melt flow index increased by over 76% at 0.5%wt loading compared with the pure PA6 resin, facilitating processing and dispersion of the flakes within the matrix and increasing the elastic modulus and tensile strength by 39%. However, high filler content above 10% has been achieved only for GNPs improving the elastic modulus by 50% at 15%wt

Reinforcement of natural rubber by precipitated silica: the influence of processing temperature

The thermal history and in particular the mixing dump temperature is a parameter of paramount importance in mixing rubber and silica with a silane coupling agent in order to achieve proper silanization of silica and to avoid premature scorch reactions. In this work, the influence of mixing dump temperature on the performance of silica reinforced Natural Rubber (NR) is investigated. The investigation also includes the effect of non-rubber constituents, primarily proteins in NR, by using deproteinized Natural Rubber (DPNR) and synthetic polyisoprene (IR). The vulcanization properties and rubber-to-filler interactions of silica reinforced NR in presence and absence of a silane coupling agent are highlighted. With increasing mixing dump temperature, the silanization reaction between silica and silane coupling agent proceeds further. At sufficiently high dump temperature, filler-filler interactions in the NR-silica compounds are reduced and silica-rubber interaction improved as evidenced by a drop in the Payne effect and increment in chemically bound rubber. It is demonstrated that NR and IR compounds mixed till above the optimum dump temperature exhibit cure reversion and reduction in tensile properties. On the other hand, DPNR-silica vulcanizates show slightly more constant physical properties

The challenges of silica-silane reinforcement of natural rubber

In recent years, highly-dispersible silica has become the preferred alternative to carbon-black as reinforcing filler for low rolling-resistance tires. However, the application of this filler system is so far limited to passenger car tires, as their treads contain styrene butadiene rubber (SBR). In contrast to this, truck tires are mainly made from natural rubber (NR); this is the main application of the currently used 11 million tons of natural rubber. unfortunately, the combination of NR with silica and a coupling agent remains a challenge. Natural rubber is a durable, natural resource, but has the disadvantage of containing a variety of non-rubber components such as proteins. An in-rubber study of the interaction of silica with proteins present in natural rubber shows that the latter compete with the coupling agent during the silanization reaction; the presence of proteins makes the silane less efficient for improving dispersion and fillerpolymer coupling, and thus negatively influences the final properties of the rubber material. Furthermore, the protein\ud content influences the rheological properties as well as filler-filler and filler-polymer interactions. Stress strain properties also vary with protein content, as do dynamic properties. With high amounts of proteins present in NR, the interactions between proteins and silica are able to disrupt the silica-silica network and improve silica dispersion. High amounts of proteins reduce the thermal sensitivity of the filler-polymer network formation. The effect of proteins is most pronounced when no silane is used; however, proteins are not able to replace a coupling agent. In order to achieve a good balance of properties, the presence of a coupling agent is essential. Keywords: silica, silane, natural rubber, protein, rolling resistance

Preparation and characterization of self assembled polymer nanocomposites

Polymerní nanokompozity na bázi polyhedrálních oligomerních silsesquioxanů (POSS) představují slibnou oblast výzkumu, která potenciálně může využít samouspořádávní při navrhování nových materiálů. Tato diplomová práce popisuje postup přípravy oktafenyl-POSS/PS, oktafenyl-POSS/PMMA a oktamethyl-POSS/PS systémů a charakterizaci jejich termomechanických vlastností v pevné fázi a reologických vlastností v roztoku. Získané výsledky jsou diskutovány s přihlédnutím k teoriím zabývajících se stavem disperze nanočástic.Polymer nanocomposites based on polyhedral oligomeric silsesquioxanes (POSS) are promising field which could potentially utilize self-assembly approach in designing new materials. In this thesis, a preparation protocol of octaphenyl-POSS/PS, octamethyl-POSS/PMMA and octamethyl-POSS/PS systems was described and thermomechanic properties in solid state and rheological properties in solution were investigated. The obtained results are discussed with focus on nanoparticles dispersion state theories.

Is there any chance for polypropylene/clay nanocomposites in injection molding?

editoria

The influence of masterbatches of fillers and stabilizers on polyethylene’s thermostability

The article presents the influence of joint and separate introduction of fillers (ADDITIVE 13169, TALC MB, EFPE 1001, VC PE 175) and stabilizers (RA10) masterbatches on the thermal aging of polyethylene’s composites. It was estimated the thermal stability of polyethylene compositions by determining dynamics change of strength properties du ring thermal aging. The ac tivation energy of thermal oxidative degradation of polyethylene compositions was calculated. The content of carbonyl groups in the IR spectra was determined. Compositions with high thermal stability containing mas-terbatches chalk (VC PE 175) and talc (TALC MB) and masterbatch stabilizer PA10 were developed

Low density polyethylene/silica nanocomposite foams. Relationship between chemical composition, particle dispersion, cellular structure and physical properties

Postprint (author's final draft