Elastomer Research Articles

Crack modes and toughening strategies of bioinspired 3D printed double-helicoidal architectures

The crack modes and toughening strategies of 3D printed double-helicoidal (DH) composites were fully characterized by performing quasi-static three-point bending experiments and simulations. Notch-containing DH specimens were fabricated with dual-material curing 3D printer PolyJet technology, while single-helicoidal (SH) specimens were also prepared for comparison. The rigid glassy polymer VeroWhite and the soft rubbery polymer TangoBlackPlus were selected as the brick and adhesive of the specimens, respectively. First, the crack propagation path of the specimens under three-point bending loading was observed, and the fracture toughness and critical deformation displacements were calculated. The double twisting pattern of DH composite makes cracks deflect along complex deflection paths, resulting in increased energy dissipation required to produce deflected crack surfaces, which delays catastrophic damage. Then, the deformation and interlayer stress distribution under static loading were analyzed by finite element analysis. It was found that the interlaminar shear stresses σ13 and σ23 generated in adjacent layers were responsible for the crack deflection of the DH specimens. Toughening mechanisms of the DH structure inspired by coelacanth will promote the design of next generation fracture-resistant composites.

Polydimethylsiloxane/Magnesium Oxide Nanosheet Mixed Matrix Membrane for CO2 Separation Application

Carbon dioxide (CO2) concentration is now 50% higher than in the preindustrial period and efforts to reduce CO2 emission through carbon capture and utilization (CCU) are blooming. Membranes are one of the attractive alternatives for such application. In this study, a rubbery polymer polydimethylsiloxane (PDMS) membrane is incorporated with magnesium oxide (MgO) with a hierarchically two-dimensional (2D) nanosheet shape for CO2 separation. The average thickness of the synthesized MgO nanosheet in this study is 35.3 ± 1.5 nm. Based on the pure gas separation performance, the optimal loading obtained is at 1 wt.% where there is no observable significant agglomeration. CO2 permeability was reduced from 2382 Barrer to 1929 Barrer while CO2/N2 selectivity increased from only 11.4 to 12.7, and CO2/CH4 remained relatively constant when the MMM was operated at 2 bar and 25 °C. Sedimentation of the filler was observed when the loading was further increased to 5 wt.%, forming interfacial defects on the bottom side of the membrane and causing increased CO2 gas permeability from 1929 Barrer to 2104 Barrer as compared to filler loading at 1 wt.%, whereas the CO2/N2 ideal selectivity increased from 12.1 to 15.0. Additionally, this study shows that there was no significant impact of pressure on separation performance. There was a linear decline of CO2 permeability with increasing upstream pressure while there were no changes to the CO2/N2 and CO2/CH4 selectivity.

Effectiveness of a Combined Toothbrushing Technique on Cariogenic Dental Biofilm in Relation to Stainless Steel and Elastomeric Ligatures in Orthodontic Patients: A Randomized Clinical Trial

Increased dental biofilm commonly occurs during orthodontic treatment. The aim of this study was to evaluate the effect of a combined toothbrushing method on dental biofilm cariogenicity in patients with stainless steel (SSL) and elastomeric (EL) ligatures. At baseline (T1), 70 participants were randomized (1:1 ratio) to the SSL or EL group. Dental biofilm maturity was evaluated using a three-color-disclosing dye. The participants were instructed to brush their teeth using a combined horizontal-Charters-modified Bass technique. Dental biofilm maturity was reassessed at the 4-week follow-up (T2). We found that at T1, new dental biofilm was the highest, followed by mature and cariogenic dental biofilm in the SSL group (p < 0.05). In the EL group, cariogenic dental biofilm was highly observed, followed by mature and new dental biofilm (p < 0.05). After intervention, cariogenic dental biofilm significantly decreased in both groups (p < 0.05). Moreover, a marked decrease in cariogenic dental biofilm was observed in the EL group compared with the SSL group (p < 0.05). However, the change in mature dental biofilm in the groups was similar (p > 0.05). Our results demonstrated that the combined toothbrushing method reduced cariogenic dental biofilm in the SSL and EL groups.

Water Sorption in Rubbery and Glassy Polymers, Nifedipine, and Their ASDs.

Polymers like poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA) or hydroxypropyl methylcellulose acetate succinate (HPMCAS) are commonly used as a matrix for amorphous solid dispersions (ASDs) to enhance the bioavailability of the active pharmaceutical ingredients (APIs). The stability of ASDs is strongly influenced by the water sorption in the ASD from the surrounding air. In this work, the water sorption in the neat polymers PVPVA and HPMCAS, in the neat API nifedipine (NIF), and in their ASDs of different drug loads was measured above and below the glass-transition temperature. The equilibrium water sorption was predicted using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) combined with the Non-Equilibrium Thermodynamics of Glassy Polymers (NET-GP).The water-sorption kinetics were modeled using the Maxwell-Stefan approach whereas the thermodynamic driving force was calculated using PC-SAFT and NET-GP. The water diffusion coefficients in the polymers, NIF, or ASDs were determined using the Free-Volume Theory. Using the water-sorption kinetics of the pure polymers and of NIF, the water-sorption kinetics of the ASDs were successfully predicted, thus providing the water diffusion coefficients in the ASD as a function of relative humidity and of the water concentration in polymers or ASDs.

How Segmental Dynamics and Mesh Confinement Determine the Selective Diffusivity of Molecules in Cross-Linked Dense Polymer Networks.

The diffusion of molecules ("penetrants") of variable size, shape, and chemistry through dense cross-linked polymer networks is a fundamental scientific problem broadly relevant in materials, polymer, physical, and biological chemistry. Relevant applications include separation membranes, barrier materials, drug delivery, and nanofiltration. A major open question is the relationship between transport, thermodynamic state, and penetrant and polymer chemical structure. Here we combine experiment, simulation, and theory to unravel these competing effects on penetrant transport in rubbery and supercooled polymer permanent networks over a wide range of cross-link densities, size ratios, and temperatures. The crucial importance of the coupling of local penetrant hopping to polymer structural relaxation and the secondary importance of mesh confinement effects are established. Network cross-links strongly slow down nm-scale polymer relaxation, which greatly retards the activated penetrant diffusion. The demonstrated good agreement between experiment, simulation, and theory provides strong support for the size ratio (penetrant diameter to the polymer Kuhn length) as a key variable and the usefulness of coarse-grained simulation and theoretical models that average over Angstrom scale structure. The developed theory provides an understanding of the physical processes underlying the behaviors observed in experiment and simulation and suggests new strategies for enhancing selective polymer membrane design.

Supramolecular Networks Obtained by Block Copolymer Self-Assembly in a Polymer Matrix: Crystallization Behavior and Its Effect on the Mechanical Response

In recent years, there has been growing interest in the study of supramolecular networks obtained by self-assembly of amphiphilic molecules due to their responsive behavior to different external stimuli. The possibility of embedding supramolecular networks into polymer matrices opens access to a new generation of functional polymers with great potential for various applications. However, very little is known about how the dynamics of the supramolecular network is affected by diffusional and topological limitations imposed by the polymer matrix. In this work, we investigate the behavior of supramolecular networks embedded into a rubbery polymer. Crystallization-driven self-assembly of a poly(ethylene-block-ethylene oxide) (PE-b-PEO) diblock copolymer was used to generate supramolecular networks in dimethacrylate monomers, which were then photopolymerized at room temperature. PE-b-PEO self-assembles into nanoribbons with a semicrystalline PE core bordered by coronal chains of PEO, and the nanoribbons, in turn, bundle into lamellar aggregates with an average stacking period of around 45 nm. The nanoribbons are interconnected through crystalline nodes in a 3D network structure. Small-angle X-ray scattering experiments show that the polymer matrix preserves the structure of the supramolecular network and avoids its disintegration when the material is heated above the melting temperature of PE cores. Successive self-nucleation and annealing studies reveal that the polymer matrix does not influence the crystallization–melting processes of PE, which take place through the interconnected cores of the supramolecular network. In contrast, the matrix imposes strong effects of topological confinement on the crystallization of PEO, limiting the dimensions of the crystalline lamellae that can be formed. Mechanical tests show that the deformation capacity of these materials can be precisely tuned by programming the temperature within the melting range of the supramolecular network. This behavior was also characterized by shape memory cyclic tests.

Understanding Interfacial Block Copolymer Structure and Dynamics

Block copolymer (BCP) structure and dynamics were studied using small-angle neutron scattering (SANS), neutron spin echo (NSE) spectroscopy, and molecular dynamics (MD) simulations to obtain a fundamental understanding of the impact of an interfacial block on chain dynamics. A glassy block acted as the interface, and the dynamics of a rubbery block was studied. The rubbery block was protonated near the interface in one sample and near the chain end in another sample to observe the interfacial effect on the rubbery polymer. Analysis of the structure and dynamics revealed that the interfacial rubbery block was confined in layered morphologies and exhibited much slower dynamics than the chain-end rubbery block that was dispersed in the rubbery matrix. The interfacial rubbery block showed weaker dynamical relaxation than that at the chain end, and it also had critically important length scale dependence. Dynamical slowing was only observed at length scales significantly larger than the characteristic segmental length, and the disparity between interfacial and chain-end dynamics increased with increasing length.

Non-destructive observation of internal structures of epoxy monolith and co-continuous network polymer using X-ray CT imaging for elucidation of their unique mechanical features and fracture mechanism

New kind of polymer composites, i.e., co-continuous network polymers (CNP), were fabricated by the filling of the continuous pores of an epoxy monolith (EM) with a cross-linked acrylate polymer. The internal structures of EM and CNP were non-destructively observed by X-ray CT imaging. The mechanical properties of EM were highly dependent on the pore and epoxy frame sizes. Increasing the molar ratio of the amino groups to glycidyl groups during the monolith fabrication process created a coarser co-continuous structure. It greatly enhanced the stretching property of EM. Filling the pores of EM with a rubbery cross-linked acrylate polymer as the second component increased the maximum strength of CNP, independent of the pore size. Furthermore, the gap formation at the boundary between the hard phase and the soft phase of CNP was observed by X-ray CT imaging for the broken test piece used for a tensile test. We discussed a mechanism for the deformation and fracture of EM and CNP.

Physical aging-induced embrittlement of PLA/PBAT blends probed by tensile test and AFM nanomechanical mapping

Poly(lactic acid) (PLA) is a well-known biodegradable sustainable polyester but with intrinsic brittleness. PLA can be toughened through blending with immiscible rubbery polymers like biodegradable poly(butylene adipate-co-terephthalate) (PBAT). However, little was done to examine the effectiveness of the additives after long-term physical aging. Herein, the mechanical properties of PLA/PBAT (80/20) blends were measured by combining tensile tests and atomic force microscopy (AFM) based nanomechanical mapping after ageing at 40 °C for different periods. It is found that the elongation at break of the blends decreases dramatically from 257 % after compression molding to 14 % after aging for 7 days, and an equilibrium value is not yet reached. AFM nanomechanical mapping reveals that the microscopic Young’s modulus distribution of PLA matrix broadens significantly with increasing aging time, reflecting the increase of heterogeneity and resulting in the embrittlement of the blends. This work raises the severe impact of physical aging on the mechanical properties of PLA based blends, which is usually overlooked but may limit their applications.

Simulation and Experiment of CO2 Philicity and Separation in Carbonate-Rich Polymers

Functional polymers containing CO2-philic groups are of great interest for membrane CO2/gas separation for carbon capture. This work, for the first time, systematically elucidates the effect of carbonate groups on CO2/gas solubility selectivity and permselectivity using an integrated simulation and experimental approach in two carbonate-rich polymers: poly(ethylene carbonate) (PEC) and poly(propylene carbonate) (PPC). Both polymers are amorphous and rubbery at 35 °C, and they are thoroughly characterized for physical properties and CO2/gas separation properties. PEC exhibits a CO2/C2H6 solubility selectivity of 24 at 35 °C, much higher than that of poly(ethylene oxide) (2.8), one of the leading membrane materials for CO2/gas separation. The binding energy between gas molecules and polymer analogue was calculated using density functional theory (DFT), and the results are consistent with the experimental sorption data. Both PEC and PPC show CO2/CH4 permselectivity of ≈53 at 35 °C, the highest reported for rubbery polymers. PEC also exhibits a CO2/N2 permselectivity of 74, one of the best reported in the literature. Although polar carbonate groups may lower gas permeability, they can be incorporated into polymer architectures to improve CO2/gas selectivity.

Hybrid Benzimidazole-Dichloroimidazole Zeolitic Imidazolate Frameworks Based on ZIF-7 and Their Application in Mixed Matrix Membranes for CO2/N2 Separation.

Mixed-linker zeolitic imidazolate frameworks (ZIFs) with the sodalite (sod) topology type and based on ZIF-7 have been prepared by direct synthesis from the mixtures of benzimidazole (BzIm) and 4,5-dichloroimidazole (dcIm). Incorporation of dcIm into the ZIF-7 structure gives ZIF-7/COK-17 hybrids with rhombohedral symmetry that do not show the “open-to-closed form” structural transition upon solvent removal exhibited by ZIF-7. They show Type I isotherms for low molecular weight gases and high affinity for CO2 even at low partial pressures. Synthesis under mild conditions gives ZIF nanoparticles (250–400 nm) suitable for incorporation into mixed matrix membranes (MMMs): these were prepared with both glassy (Matrimid) and rubbery (PEBAX 1657) polymers. Permeation tests at 298 K and 1.2 bar reveal that the incorporation of Zn(BzIm0.55dcIm0.45)2 nanoparticles at up to ca. 12 wt % gives defect-free membranes with enhanced CO2 permeability in both polymer matrices, with retention of selectivity (Matrimid) or with an enhancement in selectivity that is most pronounced for the smaller nanoparticles (PEBAX). The membrane with the best performance exhibits a selectivity of ca. 200 for CO2/N2 (a 4-fold increase compared to the pure polymer) and a CO2 permeability of 64 Barrer. At the relatively low loadings investigated, the MMMs’ performance obeys the Maxwell model, and the intrinsic property of diffusivity of the ZIFs can be extracted as a result.

Geometric thermodynamics of strain-induced crystallization in polymers.

Going beyond the classical Gaussian approximation of Einstein's fluctuation theory, Ruppeiner gave it a Riemannian geometric structure with an entropic metric. This yielded a fundamental quantity, the Riemannian curvature, which was used to extract information on the nature of interactions between molecules in fluids, ideal gases, and other open systems. In this article, we examine the implications of this curvature in a nonequilibrium thermodynamic system where relaxation is sufficiently slow so as not to invalidate the local equilibrium hypothesis. The nonequilibrium system comprises a rubbery polymer undergoing strain induced crystallization. The curvature is found to impart information on a spurious isochoric energy arising from the conformational stretching of already crystallized segments. This unphysical component perhaps arises as the crystallized manifold is considered Euclidean with the stretch measures defined via the Euclidean metric. The thermodynamic state associated with curvature is the key to determine the isochoric stretch and hence the spurious energy. We determine this stretch and propose a form for the spurious free energy that must be removed from the total energy in order for the correct stresses to be recovered.

Strengthening and Toughening of Protein-Based Thermosets via Intermolecular Self-Assembly.

As proteins are abundant polymers in biomass sources such as agricultural feedstocks and byproducts, leveraging them to develop alternatives to synthetic polymers is of great interest. However, the mechanical performance of protein materials is not suitable for most target applications. Constructing copolymers with proteins as hard domains and rubbery polymers as soft domains has been shown to be a promising strategy for improving mechanical properties. Herein, it is demonstrated that toughening and strengthening of protein copolymers can be advanced further by thermal treatment, leading to mechanical enhancements that generalize across a variety of different protein feedstocks, including whey, serum, soy, and pea proteins. The thermal treatment induces a rearrangement of protein structure, leading to the formation of intermolecular β-sheets. The ordered intermolecular structures in the hard domains of thermosets greatly improve their mechanical properties, providing simultaneous increases in strength, toughness, and modulus, with little sacrifice in fracture strain. Analogous to crystalline structures, the formation of intermolecular β-sheet structures also leads to reduced hygroscopicity. This is a valuable contribution, as practical applications of natural polymer-based plastics are frequently hindered by the materials' humidity sensitivity. Therefore, this work demonstrates a simple yet versatile strategy to improve the materials' performance from a wide range of protein feedstocks, as well as signifies the implications of protein structural assembly in materials design.

MOF-layer composite polyurethane membrane increasing both selectivity and permeability: Pushing commercial rubbery polymer membranes to be attractive for CO2 separation

We demonstrated a novel MOF-layer composite membrane consisting of three layers, based on a polyurethane/PIM layer and a UiO-66-NH2 layer to separate CO2/N2 mixture. A small amount of PIM (i.e., ≤10 wt% PIM in PU) could completely dissolve in PU. After blending it with PU, it could use its own porosity to increase the CO2 permeability of the PU/PIM polymer blend layer. UIO66-NH2 was prepared into a 10 μm thick MOF layer by spin coating. The densely packed MOF in this layer brings abundant adsorption sites to enrich CO2, thereby bringing high selectivity to the composite film. These unique two layers simultaneously increase permeability and CO2/N2 selectivity, and the PAN-UIO66-NH2-PU/PIM (10 wt%) composite membrane displayed a CO2 permeance of 333 Barrer and a CO2/N2 selectivity of 138, its performance can easily exceed the 2008 CO2/N2 upper bound. Moreover, the entanglement of its molecular chain with PIM slows down the aging, leading a more consistent selectivity performance over a sixty-day-ageing study period. This attractive separation performance of PAN-UIO66-NH2-PU/PIM provides an exciting platform for rubbery polymer membranes to economically separate CO2 and makes commercial PU an attractive option for large-scale industrial CO2 separation.

Water Sorption in Glassy Polyvinylpyrrolidone-Based Polymers.

Polyvinylpyrrolidone (PVP)-based polymers are excellent stabilizers for food supplements and pharmaceutical ingredients. However, they are highly hygroscopic. This study measured and modeled the water-sorption isotherms and water-sorption kinetics in thin PVP and PVP-co-vinyl acetate (PVPVA) films. The water sorption was measured at 25 °C from 0 to 0.9 RH, which comprised glassy and rubbery states of the polymer-water system. The sorption behavior of glassy polymers differs from that in the rubbery state. The perturbed-chain statistical associating fluid theory (PC-SAFT) accurately describes the water-sorption isotherms for rubbery polymers, whereas it was combined with the non-equilibrium thermodynamics of glassy polymers (NET-GP) approach to describe the water-sorption in the glassy polymers. Combined NET-GP and PC-SAFT modeling showed excellent agreement with the experimental data. Furthermore, the transitions between the PC-SAFT modeling with and without NET-GP were in reasonable agreement with the glass transition of the polymer-water systems. Furthermore, we obtained Fickian water diffusion coefficients in PVP and in PVPVA from the measured water-sorption kinetics over a broad range of humidities. Maxwell-Stefan and Fickian water diffusion coefficients yielded a non-monotonous water concentration dependency that could be described using the free-volume theory combined with PC-SAFT and NET-GP for calculating the free volume.

Polynorbornenes bearing ether fragments in substituents: Promising membrane materials with enhanced CO2 permeability

Polymers with rigid main chains and flexible long side substituents combine membrane properties of both glassy and rubbery polymers. Such polymers exhibit high selectivity for CO2/N2 and light hydrocarbon separations. Herein we report synthesis and gas transport properties of two sets of addition and metathesis polynorbornenes bearing flexible ether moieties as side groups. Norbornenes with one and two ether moieties per a substituent have been prepared and used as monomers. ROMP polymerization of these monomers over the 1st generation Grubbs catalyst affords high-molecular-weight products in good yields. Vinyl-addition polymerization of norbornenes with one ether moiety in a substituent also gives polymers with good film-forming properties, while the polymerization of norbornenes with cellosolve moieties (–CH2–O–CH2–CH2–O–Alk) has been a challenge and this problem has been overcome by tuning the nature of catalytic systems based on Pd–N-heterocyclic carbene complex. The obtained polymers are amorphous and show good thermal stability. Pure permeability and diffusivity of permanent gases and gaseous hydrocarbons were investigated for these polymers. Gas transport properties are considered along with the results of quantum mechanical simulations. Key parameters of the substituents for tuning gas transport properties are discussed. Polymers with cellosolve substituents demonstrate enhanced solubility-controlled permeation of CO2. The incorporation of ether moiety in side substituents also increases solubility-controlled hydrocarbon separation selectivity (up to 35 for C4/C1 pair) compared to the similar polymers with alkyl groups.

Modelling the interphase of 3D printed photo-cured polymers

3D printing , in particular the Polyjet technology, has been widely employed for the production of complex heterogeneous composites such as co-continuous architectures (the so-called Interpenetrating Phase Composites, IPCs). It is a manufacturing method in which discrete photopolymer droplets of different materials can be deposited on a build tray and cured by UV light lamp. Previous research already demonstrated how the characteristics of the interface between different photopolymers can vary if formed before or after UV curing process, with the formation of a narrow or broad interphase . In the present work, the dynamic-mechanical properties of multilayer bimaterial composites (made combining a glassy and a rubbery polymer) were investigated under tensile loading, which is relatively insensitive to the spatial arrangement of layers, as opposed to bending. The use of a simple parallel configuration allowed the development of an analytical model which incorporates the properties of the two photopolymers and their interphase, considering their effect on both elastic and dissipative behaviour of the composites; in particular, the interphase behaviour is quite close to that of the glassy polymer and even small quantities are sufficient to dramatically change the overall dissipative behaviour of the composite. It is demonstrated that reliable modelling of real co-continuous architectures as obtained by Polyjet printing (and similar techniques) should include the effect of the interphase.

Combining FTIR spectroscopy and pressure-decay techniques to analyze sorption isotherms and sorption kinetics of pure gases and their mixtures in polymers: The case of CO2 and CH4 sorption in polydimethylsiloxane

A hyphenated technique combining FTIR Spectroscopy and Barometry is implemented to study transport properties of pure and mixed gases in rubbery polymers. FTIR spectroscopy is operated in situ and in the transmission mode. The specific case of transport of pure CO2 and CH4 in polydimethylsiloxane (PDMS) was addressed by performing the experimental investigation at ambient temperature and pressure values up to 9 bar, analyzing quantitatively both the gas phase and the solid polymer phase. The IR signals of each species in the gaseous phase were first calibrated against density data of each pure gas. Then, sorption experiments from a unary gas phase were conducted increasing the pressure stepwise and the amount of gas sorbed at each pressure within the polymer was quantitatively determined by measuring the absorbance decay within the gas phase. From these measurements, equilibrium sorption isotherms and sorption kinetics of both pure gases in PDMS have been evaluated. At the same time, FTIR spectra of pure CO2 absorbed within the polymer phase were collected and calibrated. The spectroscopic contrast in the gas and the polymer phase allowed us to apply the same approaches to sorption of gas mixtures, a very difficult task with the techniques currently available. Preliminary results for the sorption of carbon dioxide from CO2/CH4 gas mixtures are presented.

How to Get the Best Gas Separation Membranes from State-of-the-Art Glassy Polymers

Herein we focus on fundamental polymer science factors in membrane-based gas separation to open another chapter on this important topic. Realistically thinking about nanometer and angstrom scale matrix attributes that are translatable into higher performance thin glassy polymer asymmetric membrane layers in practical large-scale devices is crucial. Such thinking should be guided by expertise in both polymer and membrane communities to advance the state-of-the-art. Polymer structures, membrane morphologies, and effects of operating conditions are discussed here by using specific examples to illustrate key issues. Rubbery polymers are not the focus of this discussion since they lack diffusive discrimination for size-similar penetrants, which glassy polymers provide and make them the focus here. Four scalable subtopics guide necessary thinking: (i) plasticization, (ii) antiplasticization, (iii) dual-mode transport involving saturation of unrelaxed free volume, and (iv) nonuniform free volume and stress profiles in thin skin glassy polymer asymmetric or composite membranes. Using these subtopics in the context of macromolecular science, we discuss issues needed to expand the state-of-the-art in gas separation membranes.

Mimicking human ingestion of microplastics: Oral bioaccessibility tests of bisphenol A and phthalate esters under fed and fasted states

Notwithstanding the fact that microplastic fragments were encountered in the human stool, little effort has been geared towards elucidating the impact of chemical additives upon the human health. In this work, standardized bioaccessibility tests under both fasting and fed conditions are herein applied to the investigation of human oral bioaccessibility of plastic additives and monomers (i.e. eight phthalate esters (PAEs) and bisphenol A (BPA)) in low-density polyethylene (LDPE) and polyvinyl chloride (PVC) microplastics. The generation of phthalate monoesters is evaluated in the time course of the bioaccessibility tests. Maximum gastric and gastrointestinal bioaccessibility fractions are obtained for dimethyl phthalate, diethyl phthalate and BPA, within the range of 55–83%, 40–68% and 37–67%, respectively, increasing to 56–92% and 41–70% for dimethyl phthalate and diethyl phthalate, respectively, whenever their hydrolysis products are considered. Bioaccessibility fractions of polar PAEs are dependent upon the physicochemical characteristics of the microplastics, with greater bioaccessibility for the rubbery polymer (LDPE). With the method herein proposed, oral bioaccessible pools of moderately to non-polar PAEs can be also accurately assessed for risk-assessment explorations, with values ranging from 1.8% to 32.2%, with again significantly larger desorption percentages for LDPE. Our results suggested that the highest gastric/gastrointestinal bioaccessibility of the eight PAEs and BPA is reached under fed-state gastrointestinal extraction conditions because of the larger amounts of surface-active biomolecules. Even including the bioaccessibility factor within human risk assessment/exposure studies to microplastics, concentrations of dimethyl phthalate, di-n-butyl phthalate and BPA exceeding 0.3% (w/w) may pose severe risks after oral uptake in contrast to the more hydrophobic congeners for which concentrations above 3% (w/w), except for diethylhexyl phthalate, would be tolerated.