Mixed Matrix Membranes Based on Torlon® and ZIF-8 for High-Temperature, Size-Selective Gas Separations

Torlon® is a thermally and plasticization-resistant polyamide imide characterized by low gas permeability at room temperature. In this work, we aimed at improving the polymer performance in the thermally-enhanced He/CO2 and H2/CO2 separations, by compounding Torlon® with a highly permeable filler, ZIF-8, to fabricate Mixed Matrix Membranes (MMMs). The effect of filler loading, gas size, and temperature on the MMMs permeability, diffusivity, and selectivity was investigated. The He permeability increased by a factor of 3, while the He/CO2 selectivity decreased by a factor of 2, when adding 25 wt % of ZIF-8 at 65 °C to Torlon®; similar trends were observed for the case of H2. The MMMs permeability and size-selectivity were both enhanced by temperature. The behavior of MMMs is intermediate between the pure polymer and pure filler ones, and can be described with models for composites, indicating that such materials have a good polymer/filler adhesion and their performance could be tailored by acting on the formulation. The behavior observed is in line with previous investigations on MMMs based on glassy polymers and ZIF-8, in similar conditions, and indicates that ZIF-8 can be used as a polymer additive when the permeability is a controlling aspect, with a proper choice of loading and operative temperature.

Degradation Mechanisms Occurring in PTFE-Based Coatings Employed in Food-Processing Applications

The application of polytetrafluoroethylene (PTFE) coatings to metal surfaces is a well-known procedure carried out to avoid fouling phenomena on food-processing surfaces. Fluorine-based polymers are generally chemically and thermally stable, thus allowing them to be the preferred choice when designing anti-stick coatings in the food service industry. Their lifespan, however, depends on the environmental conditions. It is well known that thermal ageing can affect the properties of PTFE polymers and reduce their mechanical, thermal, and chemical properties causing failures and contaminating food. The main goal of the study is to identify the different failure mechanisms occurring in PTFE-based coatings, using both SEM/EDXS and ATR FT-IR data to reveal the starting point of degradation phenomena in food processing applications. The results from this research reveal that the preferential points for failures are mainly the polymer/substrate interfaces, the polymer/filler interfaces, or the polymer matrix itself.

Effects of talc, kaolin and calcium carbonate as fillers in biopolymer packaging materials

We compared the performance of bio-based and biodegradable polymers for packaging applications. Cost-effective inorganic fillers (talc, kaolin and calcium carbonate) were first melt-compounded with polylactic acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT) and poly(hydroxy butyrate-co-valerate) (PHBV). Following this, injection- and compression-molded specimens were produced to test the effect of filler loading (0–30 wt%) in relation to the morphological, thermal, mechanical and barrier properties of the composites. All the fillers were homogeneously dispersed in the polymer matrices and suitable polymer–filler adhesion was observed for talc and kaolin. The elastic modulus increased at the expense of a reduced tensile and elongation. The most significant improvements in water vapor and oxygen barrier properties were achieved with talc in PLA, PBAT and PHBV films. Overall, the results point to the promise of the introduced compositions for food packaging materials.

Wear resistance of nanostructured metal-polymer self-lubricating powder composites

Tribotechnical tests and microstructural studies were carried out. Wear mechanism of nanostructured metalpolymer self-lubricating composite materials has been established. This mechanism involves in the formation of separating polymer layers on the friction surface, which reduces the coefficient of friction and running-in period of parts of friction units. Carbon nanoparticles move along the friction surface, hinder the development of seizure processes during the interaction of microroughnesses of the contacting surfaces of the material and the counterbody during the destruction of the separating polymer layers. It was found that the polymer filler is displaced from the friction zone, carbon nanoparticles are pressed into the open areas of the surface of the copper matrix of the composite when the pressure in the tribocontact is higher than 1.5 MPa. The temperature in the tribocontact increases, the polymer filler degrades, the carbon nanoparticles are removed from the friction zone, the strength properties of the composite decrease, the friction coefficient and the wear rate increase at a sliding speed above 1.5 m/s. The obtained research results can be used in mechanical engineering, transportation industry and power engineering.

Composites of Cysteamine Functionalised Graphene Oxide and Polypropylene

Cysteamine functionalised reduced graphene oxide (rGO) was grafted to polypropylene-graft-maleic anhydride (PP-g-MA) and subsequently melt blended with PP. The covalent bridging of rGO to PP-g-MA via the cysteamine molecule and co-crystallization are routes to promoting interfacial interactions between rGO and the PP matrix. A rheological percolation threshold was achieved for a nanofiller loading between 3 wt% and 5 wt%, but none detected for the composites prepared with un-functionalized rGO. At low loadings (0.1 wt%), functionalized rGO is well dispersed in the PP matrix, an interconnecting filler-filler, polymer-filler and polymer-polymer network is formed, resulting in increased tensile toughness (1 500%) and elongation at break (40%) relative to neat PP. Irrespective of whether the rGO was functionalised or not, it had a significant effect on the crystallization behavior of PP, inducing heterogeneous nucleation, increasing the crystallisation temperature (Tm) of PP by up to 10°C and decreasing the crystalline content (Xc) by ∼30% for the highest (5 wt%) filler loading. The growth of the monoclinic a-phase of PP is preferred on addition of functionalised rGO and b crystal growth suppressed.

An understandable approach to the temperature dependence of electric properties of polymer-filler composites using elementary quantum mechanics

In today’s society, with a high percentage of elderly people, floor heating to ensure constant temperature and heat jackets in winter play important roles in winter to them to live comfortable lives without compromising health – except tropical zones. Under floor heating maintains a comfortable temperature in a room without polluting the air and heat jackets allow for light clothing at comfortable temperatures. The two facilities are attributed to Joule heat generated by tunnel currents between adjacent short carbon fillers in flexible polymer matrixes under low voltage. The current between adjacent conductive fillers is due to electron transfer associated with elementary quantum mechanics. Most of undergraduate students investigating polymer physics will have learned, about electron transfer in relation to the temperature dependence of the conductivity of conductive filler-insulator polymer composites as well as the phenomenon of Joule heat at high school. Despite their industrial importance, most students show little interest for investigating electric properties, since most of polymers are insulation materials. Polymer scientists have carried out qualitative analyses for tunneling current using well-known simplified equations derived from complicated mathematical process formulated by solid-state physicists. Hence this paper is focused on a teaching approach for temperature dependence on electric properties of the polymer-filler composites relating to tunnel current in terms of elementary quantum mechanics. The approach also attempts to bridge education and research by including reference to the application limit of the well-known theories to such complicated composite systems that fillers are dispersed uniformly in the polymer matrix.

Effect of Crosslink Density on Cut and Chip Resistance of 100% SBR Based Tire Tread Compound

The effect of Crosslink density on Cut and Chip resistance was affected on a typical 100 percent styrene-butadiene rubber (SBR)-based tire tread compound. In order to successfully develop products for tires used in off-road or poor roads and other demanding rubber applications, it is important to understand the C and C effect in rubber. Crosslink density varied by varying the sulphur to the accelerator ratio and also by changing the process aids. Basic polymer, filler and other ingredients such as activators and anti-degradants have remained unchanged. In the first setup, the sulphur was kept constant and the accelerator varied and the reverse was done in the second setup. It was made to achieve different crosslink density by changing the oil dosage and adding different resins. An attempt has been made to correlate Cut and Chip resistance to other physical properties. All these tests have been identified and optimized by the traditional tire tread compound.

Nano lamellar zirconium phosphate and screw speed changing properties of melt extrusion polypropylene nanocomposites

Tetravalent metal phosphates find application mainly as a catalyst and ionic exchangers besides structural and some other properties. In this study, pristine zirconium phosphate (ZrP) and chemically modified with Jeffamine™ (variable amine:phosphate ratio) were used as fillers to yield polypropylene nanocomposites by melt extrusion. Additionally, two different screw speeds (60 and 120 rpm) were carried out. Structural, crystallographic, thermal, dynamic-mechanical, and relaxometry properties were assessed. The morphology was also noticed. Wide-angle X-ray diffraction revealed that high speed and chemical modified ZrP led to the mixing of intercalated and exfoliated microstructures. Screw speed (60 rpm) and zirconium phosphate promoted a slight increase of thermal stability. Crystallization temperature and crystallinity degree were strongly influenced by screw speed and zirconium phosphate. Hydrogen nuclear magnetic resonance in the time domain endorsed the existence of polymer/filler interaction. Both screw speed and zirconium phosphate induced changes in glass transition temperature and moduli (storage and loss). Scanning electron microscopy images corroborated the polymer/filler interaction due to the low level of micro void and filler detachment. Crystallographic, thermal, calorimetric, relaxometry and morphologic evaluations endorsed the better effect of high screw speed and good interaction between polypropylene and phosphate.

NanoDielectric Theories

This chapter sheds light on the recent nanotechnology theoretical models for interphase power law IPL model, inhomogeneous interphase, and multi-nanoparticles technique. Moreover, this chapter reviews deliberate hypothetical researches of the effective dielectric constant for polymer/filler nanocomposites and its reliance on “filler concentration, the interphase interactions, polymer filler dielectric constant, and interphase dielectric constant.” This chapter also investigates the prediction of the dielectric constant of new nanocomposite materials dependent upon exponential power law model. Thus, this work moves from the dielectric properties of beginning polymer matrix forward and predicts the dielectric properties of new nanocomposite materials to be utilized for high voltage and directing materials by adding specified nanoparticles with polymer matrix.