Manufacturing and Joining PP/NBR Blends in the Presence of Dual Compatibilizer and Halloysite Nanotubes

Polypropylene (PP)/acrylonitrile butadiene rubber (NBR) composite plates reinforced with halloysite nanotubes (HNTs) were manufactured in the presence of dual compatibilizers: PP-grafted maleic anhydride (PP-g-MA) and styrene ethylene butylene styrene-grafted maleic anhydride (SEBS-g-MA). The mechanical characteristics and microstructure of the PP/NBR/HNT nanocomposites were investigated as a function of NBR content (10, 20, and 30 wt.%) and HNTs content (3, 5, and 7 wt.%). The results demonstrated that the rubber particles were well dispersed over the PP matrix and that the HNTs were partly agglomerated at contents above 5%. Friction stir welding (FSW) was used to join the nanocomposite plates. A significant reduction in scattered NBR droplet size was seen in the FS-welded specimens containing 80/20 (wt/wt) PP/NBR composites in the presence of a dual compatibilizer. Considerable improvement in particle dispersion was observed in the case of PP/NBR blends filled 80/20 (wt/wt) with HNTs joined using FSW, leading to enhanced mechanical properties in the joints. This was due to the stirring action of the FSW tool. Suitable agreement between anticipated and confirmed values was observed in experiments.

Acid-triggered, degradable and high strength-toughness copolyesters: Comprehensive experimental and theoretical study

The popularization and widespread use of degradable polymers is hindered by their poor mechanical properties. It is of great importance to find a balance between degradation and mechanical properties. Herein, poly(butylene terephthalate) (PBT) modified by SPG diol from 10% to 40 mol% were synthesized through a two-step polycondensation reaction. Chemical structures, thermal properties, mechanical properties, viscoelastic behavior and degradation of poly(butylene terephthalate-co-spirocyclic terephthalate) (PBST) were investigated. The SPG could toughen the copolyesters and the elongation at break of PBST20 was up to 260%. Moreover, the introduction of SPG enables to provide an acid-triggered degradable unit in the main chain. PBSTs copolymers maintain stable structures in a neutral environment, and the degradation under acid conditions will be unlocked. As tailoring the content of SPG, the degradation rate of the chain scission in response to acid stimuli will be adjusted. The acid degradation was proved to be occurred at the SPG units in the amorphous phase by DSC, XRD, GPC and ¹H NMR tests. After the acid degradation, the hydrolysis rate will also be accelerated, adapting to the requirements of different degradation schedules. The plausible hydrolytic pathways and mechanisms were proposed based on Fukui function analysis and density functional theory (DFT) calculation.

Bio-Based PBT-DLA Copolyester as an Alternative Compatibilizer of PP/PBT Blends

The aim of this work was to assess whether synthesized random copolyester, poly(butylene terephthalate-r-butylene dilinoleate) (PBT–DLA), containing bio-based components, can effectively compatibilize polypropylene/poly(butylene terephthalate) (PP/PBT) blends. For comparison, a commercial petrochemical triblock copolymer, poly(styrene-b-ethylene/butylene-b-styrene) (SEBS) was used. The chemical structure and block distribution of PBT–DLA was determined using nuclear magnetic resonance spectroscopy and gel permeation chromatography. PP/PBT blends with different mass ratios were prepared via twin-screw extrusion with 5 wt% of each compatibilizer. Thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis were used to assess changes in phase structure of PP/PBT blends. Static tensile testing demonstrated marked improvement in elongation at break, to ~18% and ~21% for PBT–DLA and SEBS, respectively. Importantly, the morphology of PP/PBT blends compatibilized with PBT–DLA copolymer showed that it is able to act as interphase modifier, being preferentially located at the interface. Therefore, we conclude that by using polycondensation and monomers from renewable resources, it is possible to obtain copolymers that efficiently modify blend miscibility, offering an alternative to widely used, rubber-like petrochemical styrene compatibilizers.

Tuning the compatibility to achieve toughened biobased poly(lactic acid)/poly(butylene terephthalate) blends

A series of sustainable biobased polymer blends from poly(lactic acid) (PLA) and poly(butylene terephthalate) (PBT) were fabricated and characterized. These blends are engineered to achieve optimal mechanical properties and toughness with a reactive epoxidized styrene-acrylic copolymer (ESAC) compatibilizer, and an ethylene-n-butyl-acrylate-co-glycidyl methacrylate (EBA-GMA) elastomer-based compatibilizer. The results showed that the tensile strength, modulus, flexural strength and modulus of the PBT increase, while the elongation at break and notched impact strength decrease after blending with the biopolymer PLA. The full co-continuity of PLA in PBT was confirmed at a 50/50 wt% blend ratio. The droplet size of the PLA was reduced and the distinct phases of the blends were gradually diminished with the increasing content of the ESAC compatibilizer. The increase in the complex viscosity of the blends was due to the formation of PLA-g-PBT copolymers in the blend after addition of reactive compatibilizers. The incorporation of both compatibilizers in the blends led to superior notched impact strength in comparison to only a single compatibilizer used in the blends. The synergistic effect of both compatibilizers effectively reduces the PLA droplet size and improves the dispersion of PLA in PBT as evidenced by atomic force microscopy (AFM) topography observations. The high toughness of the blends corresponds to the formation of effective EBA-GMA structures and enhanced interfacial compatibilization due to the synergistic effect of the compatibilizers.

Novel toughened biobased polymer blends from poly(lactic acid) and poly(butylene terephthalate) were developed by judicious compatibilization.