Two antagonistic effects of flow/mixing on reactive polymer blending

Reactive polymer blending is basically a flow/mixing-driven process of interfacial generation, interfacial reaction for copolymer formation and morphology development. This work shows two antagonistic effects of mixing on this process: while mixing promotes copolymer formation by creating interfaces and enhancing collisions between reactive groups at the interfaces, excessive mixing may pull the in-situ formed copolymer out of the interfaces to one of the two polymer components of the blend, especially when the copolymer becomes highly asymmetrical. As such, the copolymer may loss its compatibilization efficiency. The mixing-driven copolymer pull-out from the interfaces is a catastrophic process (less than a minute), despite the high viscosity of the polymer blend. It depends on the molecular architecture of the reactive compatibilizer, polymer blend composition, mixing intensity and annealing. These findings are obtained using the concept of reactive tracer-compatibilizer and a model reactive polymer blend.

Wellbore Integrity and CO2 Sequestration Using Polyaramide Vesicles

A new cementing additive is chemically engineered to react with formation fluids that act antagonistically towards cement. Engineered polymer capsules house encapsulants to react with antagonistic gases downhole like CO2 to form a more benign and beneficial material. Embedded in cement, the polymer capsules with semi-permeable shells allow fluids to permeate and react with encapsulants to produce beneficial byproducts, such as calcite and water from CO2. Reactivity between the encapsulant and antagonist gas CO2 is demonstrated using thermal gravimetric analysis (TGA) and other tests from oilfield equipment. When cement fails, casing-in-casing events, or CCA, causes antagonistic gases like CO2 to migrate to the surface. Embedded in the cement for such moments such as cement failure, additives housed within polyaramide vesicles chemically and physically intersect CO2 from gas migration events. The shape of the polyaramide additive is unique and versatile. Furthermore, because the material is polymeric, it imparts beneficial mechanical properties like elasticity to cement. A vesicle in form, this polymer allows the manufacturing of new cement additives for applications such as increasing the integrity and sustainability of oil well cement. Data also shows production of calcite by the bulk of the material. This technology applies to CO2 fixation and self-healing cement using reactive polymer vesicles.

In vivo and Post-synthesis Strategies to Enhance the Properties of PHB-Based Materials: A Review

The transition toward “green” alternatives to petroleum-based plastics is driven by the need for “drop-in” replacement materials able to combine characteristics of existing plastics with biodegradability and renewability features. Promising alternatives are the polyhydroxyalkanoates (PHAs), microbial biodegradable polyesters produced by a wide range of microorganisms as carbon, energy, and redox storage material, displaying properties very close to fossil-fuel-derived polyolefins. Among PHAs, polyhydroxybutyrate (PHB) is by far the most well-studied polymer. PHB is a thermoplastic polyester, with very narrow processability window, due to very low resistance to thermal degradation. Since the melting temperature of PHB is around 170–180°C, the processing temperature should be at least 180–190°C. The thermal degradation of PHB at these temperatures proceeds very quickly, causing a rapid decrease in its molecular weight. Moreover, due to its high crystallinity, PHB is stiff and brittle resulting in very poor mechanical properties with low extension at break, which limits its range of application. A further limit to the effective exploitation of these polymers is related to their production costs, which is mostly affected by the costs of the starting feedstocks. Since the first identification of PHB, researchers have faced these issues, and several strategies to improve the processability and reduce brittleness of this polymer have been developed. These approaches range from the in vivo synthesis of PHA copolymers, to the enhancement of post-synthesis PHB-based material performances, thus the addition of additives and plasticizers, acting on the crystallization process as well as on polymer glass transition temperature. In addition, reactive polymer blending with other bio-based polymers represents a versatile approach to modulate polymer properties while preserving its biodegradability. This review examines the state of the art of PHA processing, shedding light on the green and cost-effective tailored strategies aimed at modulating and optimizing polymer performances. Pioneering examples in this field will be examined, and prospects and challenges for their exploitation will be presented. Furthermore, since the establishment of a PHA-based industry passes through the designing of cost-competitive production processes, this review will inspect reported examples assessing this economic aspect, examining the most recent progresses toward process sustainability.

Viscosity improvement of recycled poly (ethylene terephthalate) from waste bottles by adding antioxidants and chain-extender

This research work is focused on the viscosity improvement of recycled poly(ethylene terephthalate) (rPET) from waste bottles by adding antioxidants and multi-functional reactive polymer (Joncry ADR 4468, chain extender). The achieve the objective of this work the investigated was broken into two parts. The first part studied the effect of rPET viscosity after adding various types of antioxidants and stabilizer such as Irgafos®168, Tinuvin® 770, Irganox®1010. The second part observed the effect of viscosity after it was blended with chain extender at 0, 0.2, 0.4, 0.6 and 0.8 pph. rPET was then dried in the oven at 120 oC for 12 hrs, to deplete the moisture. Then, the dried rPET (mixed with the chemicals above) was extruded into a compound using a twin screw extruder. The shear viscosity of the extruded compound was then measured using a rotational rheometer at 270 oC. The results revealed that the addition of chain extender increased the shear viscosity and the tensile strength at break of rPET. Therefore, the chain extender interacted with chains, which could change the structure to be the longer chains, branching or network structures. These structures are entangled and interrupt the movement of the molecular chains. It can be concluded that the viscosity of rPET can be improved by adding a chain extender at 0.6 pph, and the antioxidants of Irgafos®168, Tinuvin®770 and Irganox®1010 at 0.2, 0.1 and 0.5 pph, respectively.