POSS Content Research Articles

Structure–property relationships and nanofiller‐induced hydro‐anti‐plasticization in polyhydroxyurethane/POSS hybrid composites

AbstractNon‐isocyanate polyhydroxyurethanes/polyhedral oligomeric silsesquioxane (PHU/POSS) hybrid composites are prepared by in situ physical introduction of octa(3‐hydroxy‐3‐ethylbutyldimethylsiloxy) POSS into a linear non‐isocyanate polyhydroxyurethane matrix. The amorphous nature of the matrix is retained in the composites and no POSS crystals are observed. Thermal and mechanical properties are studied along with water‐polymer interactions and are discussed in terms of structure‐properties relationships. POSS has only minimal effect on thermal stability. Composite materials with up to 2 wt% POSS exhibit an increased rubbery modulus. The glass transition temperature of the composite materials increases up to 2 wt% loading and decreases at higher POSS content. Water‐polymer interactions are studied in a broad range of relative humidity (0–0.97). Materials exhibit a relatively high water absorption, which is enhanced by POSS at low concentrations. Moisture sorption isotherms are discussed in terms of the Guggenheim‐Anderson‐de Boer model. The study of molecular mobility of hydrated systems by differential scanning calorimetry reveals a peculiar POSS‐induced antiplasticization in PHU/POSS blends at 10–20 wt% water uptake, possibly due to the formation of POSS‐centered water clusters.

THERMODYNAMICS, MORPHOLOGY AND DYNAMIC-MECHANICAL PROPERTIES OF POLYURETHANE AND NANOCOMPOSITES BASED ON IT, CONTAINING HYDROXY-POSS

Nanocomposites based on polyurethane matrix consisting of an adduct of trimethylolpropane with toluene diisocyanate and a bifunctional polyester of poly(diethylene glycol) adipinate with mol. weight 2000, and contained 1,2-propanediolisobutyl-POSS with the amount of 1–10 %, were synthesized. The thermodynamic compatibility, dynamic-mechanical properties and morphology of the created nanocomposites were investigated. For the purpose of calculations the thermodynamic parameters of interactions between the components of POSS-containing nanocomposites, a study of the isothermal sorption of methylene chloride vapors by the created systems was conducted. The sorption of methylene chloride vapors by the samples of the native PU, POSS-containing nanocomposites and nanofiller was studied using a vacuum instalation with McBean balances. The values of the free energy of polyurethane and POSS mixing during the formation of the nanocomposites were calculated based on the concentration dependences of Ägm - the average free energy of mixing of individual components (polyurethane and POSS) and nanocomposites with methylene chloride, according to the thermodynamic cycles proposed by A.A. Tager. It is shown that polyurethane and hydroxy-POSS demonstrate thermodynamic incompatibility during the formation of nanocomposites. The free energy of mixing polyurethane and hydroxy-POSS have positive values at all concentrations of the nanofiller. By the method of dynamic-mechanical analysis investigations it was shown that the introduction of POSS into polyurethane matrix led to a shift of the tan δ maximum in the direction of increasing temperatures. The temperature values of the tan δ peak for nanocomposites with increasing POSS content increased from 38 to 47 °C for PU1 and PU10, respectively. With the introduction of the POSS nanofiller into the polyurethane matrix, the intensity of the tan δ peak also decreased. Therefore, it was shown that the introduction of hydroxy-POSS into the polyurethane matrix leads to suppression of segmental motions in polyurethane, to an increase in the glass transition temperature of nanocomposites, and to an increase in the modulus of elasticity of nanocomposites compared to the native matrix. It is assumed that this happens due to the fact that the part of hydroxy-POSS, which was not incorporated into the polyurethane chain, is concentrated in the flexible segments of polyurethane as a nanofiller. When studying the morphology of the created nanocomposites using scanning electron microscopy, it was found that starting from a content of 3 % of hydroxy-POSS, it forms agglomerates of nanoparticles in the polyurethane matrix, which increase in size when the content of hydroxy-POSS increases.

Unlocking the Potential Use of Reactive POSS as a Coagent for EPDM/PP-Based TPV.

Thermoplastic vulcanizates (TPVs) are multifunctional materials consisting of two or more phases with solid elastomeric properties at room temperatures and fluid-like properties above their melting point. They are produced through a reactive blending process known as dynamic vulcanization. The most widely produced TPV type is ethylene propylene diene monomer/polypropylene (EPDM/PP), which is the focus of this study. The peroxides are mainly selected to be used in crosslinking of EPDM/PP-based TPV. However, they still have some disadvantages, such as the side reactions resulting in the beta chain scission of the PP phase and undesired disproportionation reactions. To eliminate these disadvantages, coagents are used. In this study, for the first time, the use of vinyl functionalized polyhedral oligomeric silsesquioxane (OV-POSS) nanoparticles was investigated as a potential coagent in EPDM/PP-based TPV production via peroxide-initiated dynamic vulcanization. The properties of the TPVs having POSS were compared with the conventional TPVs containing conventional coagents, such as triallyl cyanurate (TAC). POSS content and EPDM/PP ratio were investigated as the material parameters. Mechanical properties of EPDM/PP TPVs exhibited higher values in the presence of OV-POSS, which resulted from the active participation of OV-POSS into the three-dimensional network structure of EPDM/PP during dynamic vulcanization.

THE STUDY OF INTERMOLECULAR INTERACTIONS IN THE POSS-CONTAINING NANOCOMPOSITES BASED ON POLYURETHANE AND POLYURETHANE/POLY(HYDROXYPROPYL METHACRYLATE) MATRICES

The nanocomposites based on polyurethane matrix and multicomponent polymer matrices consisting of polyurethane and poly(hydroxypropyl methacrylate) with different contents of the last, and 1,2-propanediolisobutyl polyhedral oligomeric silsesquioxane (1,2-propanediolisobutyl-POSS), which was used as a functionalized nanofiller, were synthesized. The influence of the content of 1,2-propanediolisobutyl-POSS on intermolecular interactions and structural features of the nanocomposites was investigated by the method of IR-spectroscopy with Fourier transformation and attenuated total reflection (FTIR-ATR). The study of thermal curing of the model system, which consists of the adduct of trimethylolpropane with toluene diisocyanate and 1,2-propanediolisobutyl-POSS, made it possible to conclude that 1,2-propanediolisobutyl-POSS participates in the reaction of urethane formation using of one of the terminal hydroxyl groups, and it is incorporated into the polymer chain between cross-linking of polyurethane networks. The investigation of multicomponent polymer matrices by FTIR-ATR spectroscopy was done and was shown that photopolymerization of second polymer poly(hydroxypropyl methacrylate) in the matrix of polyurethane was completed by the opening of a double bond and the formation of a linear polymer in the composition of semi-IPN. Studies of nanocomposites based on multicomponent polymer matrices consisting of polyurethane and poly(hydroxypropyl methacrylate) with 15 and 30 % of the last by FTIR-ATR spectroscopy demonstrated the presence of POSS in the nanocomposites and the influence of POSS content on the structure of the studied systems and on the degree of phase separation. The POSS is "embedded" into the polymer chain between cross-linking of the polyurethane networks, with the additional formation of a complex system of intermolecular hydrogen bonds between the carboxyl and amine components of urethane groups in the nanocomposites.

THE THERMODYNAMICS OF INTERACTIONS AND RELAXATION PROPERTIES OF THE POSS-CONTAINING NANOCOMPOSITES BASED ON POLYURETHANE-POLY(HYDROXYPROPYL METHACRYLATE) MATRIX, WHICH IS FORMED BY THE PRINCIPLE OF IPNS

A series of the nanocomposites based on a multicomponent polymer matrix consisting of polyurethane and poly(hydroxypropyl methacrylate) and 1,2-propanediolysobutyl polyhedral oligomeric silsesquioxane (1,2-propanediolysobutyl-POSS), used as a functionalized nanofiller, was synthesized. The polymer matrix was formed on the principle of interpenetrating polymer networks (IPNs). The influence of 1,2-propanediolysobutyl-POSS amount on the thermodynamics of polymer components of the matrix interactions and on the dynamic mechanical properties of the created nanocomposites was studied. With purpose of the thermodynamic parameters interactions calculations the isothermal sorption of methylene chloride vapour by samples was investigated. The methylene chloride vapour sorption by the samples was studied using a vacuum installation and a McBain balance. By calculations of the thermodynamic parameters of PU and PHPMA interactions was shown that the free energy of PU and PHPMA mixing was positive. The introduction of 1-3 wt % of POSS lead to further phase separation in semi-IPNs. This is due to concentration of POSS particles in the PU’s nanodomains. The increasing of POSS content up to 5-10 wt % lead to compatibi-lization in semi-IPNs. These is due to concentration of POSS nanoparticles not only in the PU’s nanodomains but also in the interphase region of semi-IPN. The dynamic mechanical properties of the created nanocomposites were investigated and the degree of polymer components segregation was calculated. It was shown that there are two peaks of tan δ (PU and PHPMA) in the nanocom-posites. The introduction of 1-3 wt % of POSS lead to increasing of tan δ peak of PHPMA and to deepening of the bridge between two peaks (PU and PHPMA). At the same time the degree of polymer components of the matrix segregation became higher. This means the further phase separation in semi-IPNs. Increasing of 1,2-propanediolysobutyl-POSS amount up to 5-10% leads to the concentration of the nanofiller not only in the nanodomains of PU, but also in the interfacial layers. This leads to a change in the free energy of polymer components mixing, which becomes negative. At the same time the degree of polymer components of the matrix segregation became significantly reduced. These means that the process of compatibilization took part in the semi-IPNs.

The effect of macromolecular architecture of ethylene copolymers with multi-alkenylsilsesquioxane on morphological, rheological and dynamic mechanical behavior

The influence of the degree and the way of incorporation of multi-alkenylsilsesquioxane into the polymer chain on morphological, rheological and dynamic mechanical parameters were determined. It was found that POSS incorporated into the polymer chain was located outside the crystalline structure of lamella in amorphous phase. The incorporation of POSS-6-2 as a pendant group resulted in significant increase of separation of macromolecules. The key factor in rheological and dynamic mechanical behavior of copolymers turned out to be the way of POSS incorporation into the polymer chain. The incorporation of POSS into the polymer chain as a pendant group resulted in decreased relaxation time of reputation in comparison with PE. The glass transition temperature for E/POSS copolymers decreased with increasing POSS content and increasing gel number due to the decrease of the crystallinity degree which affected mechanical parameters such as molecular weight between crosslinks, crosslink density and coefficient parameter.

Polyhedral Oligomeric Silsesquioxane Induced Thermomechanical Reinforcement in Polymer Films Using Only Parts‐per‐Million Content

AbstractReinforcement of polymers by nanoparticles has been a challenge due to aggregation and solubility limits, especially at high loads. In this research, a robust and environmentally friendly fabrication approach to produce films reinforced with only parts‐per‐million (ppm) octamethyl‐polyhedral oligomeric silsesquioxane (mePOSS) using conventional extrusion and blow molding processing is demonstrated. The nanocomposites exhibit enhanced thermomechanical properties, and only 160 ppm mePOSS increase the tensile mechanical modulus, E, by ≈120% relative to the neat polymer. Remarkably, there is no penalty on strain at fracture εf, as usually seen in reinforced (nano) composites. Toughness, yield stress, tear, and puncture resistance are also an increasing function of mePOSS content. Furthermore, mePOSS also increase the thermal decomposition temperature and melting temperature. The placement of mePOSS in the molecular web is key to the thermal and mechanical reinforcement and these properties maximize when the nanoparticle size 〈D〉 matches the tube diameter dt, i.e., 〈D〉/dt ≈ 1. This simple fabrication approach combined with ppm POSS content and tunability of physical properties afforded by the location of POSS in the entangled web offers a new paradigm for the bottom‐up design of tunable lightweight polymer nanocomposites with superior thermomechanical and transport properties.

Silicone-enriched surface of immersed polyurethane-POSS antifouling coating

A series of waterborne polyurethane-polyhedral oligomeric silsesquioxane (WBPU-POSS) dispersions were synthesized. Different POSS contents were used to evaluate the effect of POSS content on silicone enrichment under both nonimmersed and immersed conditions. The impact of silicone enrichment under immersed conditions on antifouling properties was also evaluated. The structure of the WBPU-POSS coating was identified by FT-IR and 29Si-NMR. X-ray photoelectron spectroscopy (XPS) analysis confirmed a silicone-enriched surface with a certain composition of the WBPU-POSS coating under both nonimmersed and immersed conditions. The mechanical properties, hydrophilicity and hydrolytic degradation of the coating all varied with POSS content. The long-term antifouling performance of immersed coatings depends on surface silicone enrichment, which was found to be above 0.0021 mole POSS content in WBPU-POSS coatings.

Preparation and Performance Study of Fluorosilicone Oligomer Anti-Sticking Coatings

In this paper, fluorosilicone oligomer and its curing agent are used as the main film-forming materials, and fluorosilicone POSS is added to reduce the surface energy of the composites to prepare a coating with certain anti-sticking effect. The changes of molecular structure before and after the reaction were obtained by infrared spectroscopy. The contact angle and anti-sticking property of the coating surface were studied by changing the content of POSS containing fluorine. It was found that the contact angle of fluorine-containing POSS reached 98.7° when the content of fluorine-containing POSS was 3 Wt.%. With the increase of POSS content, the anti-sticking force of composites changed little, but with the increase of the contact time of tape, the anti-sticking force showed an increasing trend.

Thermal behavior of ethylene copolymers with di- and tri-alkenylsilsesquioxane comonomers synthesized by post-metallocene catalysts

This paper reported thermal properties of ethylene copolymers with di- and tri-alkenylsilsesquioxanes (POSS) synthesized by bis(phenoxy-imine) Ti, Zr, V, and V salen-type complexes. Ethylene copolymers with multi-alkenyl POSS obtained by such complexes contain multi-alkenyl POSS incorporated into the polymer chain as a side group. They were characterized by different thermal behavior depending on the kind of multi-alkenyl POSS comonomer, and type of the catalyst used, as well as polymerization conditions and thus the structure of the copolymer chain. Ethylene/POSS copolymers differed in incorporation of POSS into the polymer chain, content of specific unsaturation groups, and molecular weight, as well as heterogeneity of polymer chain compositions. The incorporation of multi-alkenyl POSS into the polymer chain affected melting and crystallization processes of copolymers in different ways. The POSS units could act as a nucleating agent of macromolecules. The increasing POSS content in E/POSS copolymers resulted in increasing thermal stability of obtained products, regardless of the kind of multi-alkenylsilsesquioxanes used. Thermal stability of such copolymers increased with decreasing content of trisubstituted vinylene groups (internal saturations) as well. The highest improvement of thermal stability over 85 °C in comparison with PE was observed in case of E/POSS copolymers synthesized by bis(phenoxy-imine) zirconium catalyst. The composition heterogeneity of E/POSS copolymers was found to affect markedly thermal stability of E/POSS copolymers.

POSS-Induced Dynamic Cross-Links Produced Self-Healing and Shape Memory Physical Hydrogels When Copolymerized with N-Isopropyl acrylamide.

The hydrogel morphology and viscoelasticity and the two-way shape memory behavior of copolymers of N-isopropyl acrylamide-polyhedral oligomeric silsesquioxane (PNIPAm-POSS) were investigated. NIPAm-POSS copolymers are unentangled and exhibit a thermoplastic and thermoresponsive hydrogel behavior ( Romo-Uribe ; ; Albanil , Eur. Polym. J. 2018 , 99 , 350 - 360 ). Here, we demonstrated by high-resolution transmission electron microscopy that POSS segregated into crystals to form physical cross-links. The hydrogels exhibited significant swelling, higher than chemical hydrogels at the same POSS content. The morphology of the hydrogels consisted of a honeycomb structure, and the pore size and swelling were a decreasing function of POSS. Moreover, the hydrogels were self-healing, exhibiting a liquid-like behavior under large amplitude shear and rubber-like behavior immediately after cessation of shear, that is, the POSS aggregates break and re-form, acting as dynamic cross-linkers. Strikingly, the physical networks behaved as perfect networks, thus matching chemically cross-linked networks and holding the scaling |η*| ∼ ω-1. Furthermore, the physical hydrogels exhibited a thermally activated shape memory (SM) behavior, without external stress and the lower critical solution temperature (LCST) being the only stimulus. The SM process involved swelling-deswelling, effectively opening opportunities for drug delivery. Furthermore, the SM was reversible, and no external stress was involved, therefore behaving as the two-way SM. Finally, POSS modulated the shear elastic modulus G' and LCST; therefore, the PNIPAm-POSS copolymers open opportunities for reusable, thermoformable SM hydrogels with tuned mechanical modulus and activation temperature.

POSS Hybrid Robust Biomass IPN Hydrogels with Temperature Responsiveness.

In order to improve the performance of traditional sodium alginate (SA) hydrogels cross-linked by Ca2+ ions to meet greater application demand, a strategy was designed to structure novel SA-based gels (named OP-PN gels) to achieve both stimulus responsiveness and improved mechanical strength. In this strategy, the SA chains are co-cross-linked by CaCl2 and cationic octa-ammonium polyhedral oligomeric silsesquioxane (Oa-POSS) particles as the first network, and an organically cross-linked poly(N-isopropyl acrylamide) (PNIPA) network is introduced into the gels as the second network. Several main results are obtained from the synthesis and characterization of the gels. For OP-PN gels, their properties depend on the content of both uniformly dispersed Oa-POSS and PNIPA network directly. The increased Oa-POSS and PNIPA network content significantly improves both the strength and resilience of gels. Relatively, the increased Oa-POSS is greatly beneficial to the modulus of gels, and the increased PNIPA network is more favorable to advancing the tensile deformation of gels. The gels with hydrophilic PNIPA network exhibit better swelling ability and remarkable temperature responsiveness, and their volume phase transition temperature can be adjusted by altering the content of Oa-POSS. The deswelling rate of gels increases gradually with the increase of POSS content due to the hydrophobic Si–O skeleton of POSS. Moreover, the enhanced drug loading and sustained release ability of the target drug bovine serum albumin displays great potential for this hybrid gel in the biomedical field.

Mechanically Robust Hybrid POSS Thermoplastic Polyurethanes with Enhanced Surface Hydrophobicity.

A series of hybrid thermoplastic polyurethanes (PUs) were synthesized from bi-functional polyhedral oligomeric silsesquioxane (B-POSS) and polycaprolactone (PCL) using 1,6-hexamethylene diisocyanate (HDI) as a coupling agent for the first time. The newly synthesized hybrid materials were fully characterized in terms of structure, morphology, thermal and mechanical performance, as well as their toughening effect toward polyesters. Thermal gravimeter analysis (TGA) and differential scanning calorimetry (DSC) showed enhanced thermal stability by 76 °C higher in decomposition temperature (Td) of the POSS PUs, and 22 °C higher glass transition temperature (Tg) when compared with control PU without POSS. Static contact angle results showed a significant increment of 49.8° and 53.4° for the respective surface hydrophobicity and lipophilicity measurements. More importantly, both storage modulus (G’) and loss modulus (G’’) are improved in the hybrid POSS PUs and these parameters can be further adjusted by varying POSS content in the copolymer. As a biodegradable hybrid filler, the as-synthesized POSS PUs also demonstrated a remarkable effect in toughening commercial polyesters, indicating a simple yet useful strategy in developing high-performance polyester for advanced biomedical applications.

“Open‐Mouth” Mesoporous Hollow Micro/Nano Coatings Based on POSS/PDMS: Fabrication, Mechanisms, and Anti‐Icing Performance

AbstractA simple spray approach for fabricating unique micro–nano polyhedral oligomeric silsesquioxane/polydimethylsiloxane (POSS/PDMS) composite coatings decorated with 3D “opened‐mouth” hollow structures is reported. The structures are formed by a template‐free self‐assembly of cuboidal POSS precursors driven by room‐temperature aerosol‐assisted process. A three‐stage mechanism is proposed to explain the formation of the structures. The morphology and performance of the coatings are controlled via the type of the carrier liquid, the content of crystalline nanoparticles (POSS), the presence of ligands, and processing temperature. Mechanically stable micro‐ or micro–nano “open‐mouth” spherical or cylindrical structures with excellent super‐hydrophobic and anti‐icing properties are formed when POSS content exceeds 5%. Such spatial geometry of interphase‐embedded hollow structures incorporates effective heat‐transfer barrier, drastically reduces surface wettability and ice adhesion, which are quantified by water freezing temperature lowered to −26.3 °C and ice adhesion to 86 kPa.

Investigation of thermal stability of ethylene copolymers with POSS - Study under static and dynamic conditions

In the paper there was studied thermal stability of a series of ethylene copolymers with monoalkenylsiloxy- or monoalkenylsilsesquioxanes (POSS) under dynamic and static conditions. The copolymers proved to be more thermally stable than neat polyethylene and neat silsesquioxane comonomers. The kind and the content of the POSS units significantly affected degradation of the copolymers. Thermal oxidation process resulted in structural changes of the (co)polymers as it was evidenced by the variations in the kind and content of carbonyl, as well as by unsaturated end groups. Depending on the structure of the POSS comonomer incorporated into the polymer chain, the silsesquioxane units offered different stabilities which affected thermal oxidation resistance of the copolymer products. The kind and the POSS content determined the role of silsesquioxane units which may act as accelerating or stabilizing agents during thermal degradation of the copolymers. Thermo-oxidative process was also shown to affect melting and crystallization behavior of ethylene/POSS copolymers. Hampering decrease of lamellae thickness by POSS units was demonstrated for aged copolymers and the range of changes was dependent on POSS incorporation level which influenced also the homogeneity of the polymeric products.

Viscoelasticity and microstructure of POSS-methyl methacrylate nanocomposites. Dynamics and entanglement dilution

The linear viscoelastic behavior of molten hybrid nanocomposites poly [(propylmethacryl-heptaisobutyl-POSS)-co-methyl methacrylate], denoted POSSn-MMA, was investigated; POSS content varied up to n = 45 wt%. The nanocomposites were amorphous and ΔTg ≈ −20 K. The melts exhibited linear viscoelastic behavior, and master curves were constructed using time-temperature superposition (TTS) at Tref = Tg+50 K. The viscoelastic response covered terminal, rubber-like and transition regimes. Strikingly, POSS induced considerable fast dynamics with over three orders of magnitude reduction of terminal relaxation time τt. Furthermore, POSS induced entanglement dilution where the rubbery modulus Ge decreased three-fold (i.e., packing length p increased). The melt viscosity exhibited Newtonian and shear thinning regimes, and the zero-shear viscosity ηο decreased up to three orders of magnitude. The unusual viscosity reduction suggests that the viscoelastic response arises from (relatively weak) POSS-POSS associations and not chain entanglements as in linear polymers. Hence, shear would easily break the associations and rather low viscosity would be experienced. At Angstrom-scale POSS modified the structure of PMMA but did not crystallize, consistent with DSC results. At nm-scale POSS-POSS associations were detected by small-angle X-ray scattering, and the size of aggregates increased with POSS content.

Improving Damping Properties and Thermal Stability of Epoxy/Polyurethane Grafted Copolymer by Adding Glycidyl POSS

Modified castor oil-based epoxy resin (EP)/polyurethane (PU) grafted copolymer by glycidyl polyhedral oligomeric silsesquioxane (glycidyl POSS) was synthesized. The damping properties, thermal stability, mechanical properties and morphology of the grafted copolymer modified by glycidyl POSS were studied systematically. The results revealed that the incorporation of glycidyl POSS improved the damping performance evidently and broadened damping temperature range, especially when the glycidyl POSS content was 0.2%–1%. At the same time, there was a slight increase in thermal stability with the increase of POSS content. The tensile properties changed with the change of the copolymer’s Tg, decreased at low POSS contents and increased at high POSS contents. This modified copolymer has the potential to be used as film damping material or constrained damping layer.

Minimizing the Strong Screening Effect of Polyhedral Oligomeric Silsesquioxane Nanoparticles in Hydrogen-Bonded Random Copolymers.

A series of poly(vinylphenol-co-methacryisobutyl polyhedral oligomeric silsesquioxane) (PVPh-co-PMAPOSS) random copolymers have been synthesized through free radical copolymerizations of acetoxystyrene with methacryisobutyl POSS monomer and subsequent hydrazine monohydrate-mediated hydrolysis of the acetoxyl units. These random copolymers were characterized using nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC), which revealed that the POSS content in the random copolymers could be varied by changing the POSS monomer feed ratio by 1H NMR analyses. This molecular design approach allowed us to investigate the thermal properties and hydrogen bonding interactions of these PVPh-co-PMAPOSS random copolymers in comparison with those of PVPh/PMAPOSS blend systems. Hydrogen bonding interactions were absent in the PVPh/PMAPOSS blend system, because of a strong screening effect; in contrast, the PVPh-co-PMAPOSS random copolymers experienced enhanced intramolecular hydrogen bonding that minimized the strong screening effect of the POSS nanoparticles.

The effects of POSS particles on the flame retardancy of intumescent polypropylene composites and the structure-property relationship

In the current study, the effects of four different POSS nanoparticles on the flame retardant properties of intumescent PP were investigated through mass-loss calorimetry (MLC), limiting oxygen index (LOI) test and UL-94 ratings. In addition, the structure-property relationship was enlightened via thermal, morphological and mechanical tests. The four different POSS types, namely aminopropyl isobutyl-POSS (A-POSS), octaphenyl-POSS (OP-POSS), octaammonium-POSS (OA-POSS) and trissulfonic acid propyl-POSS (TS-POSS), were used. The ratio of ammonium polyphosphate (APP) to pentaerythritol (PER) was kept constant and the POSS content was varied as 0.5%, 1% and 3%. The MLC, LOI and UL-94 tests revealed that the addition of POSS particles had adjuvant on the flame retardant properties of PP/IFR system. All POSS nanoparticles showed their highest adjuvant effect at the lowest concentration of 0.5 wt%. The highest UL-94 rating and the highest LOI values were achieved in the presence of OA-POSS and TS-POSS. The ceramic layer formation was monitored using scanning electron microscopy (SEM) and FTIR on the char residues. The thermal properties of PP/IFR/POSS composites were obtained via differential scanning calorimeter and thermo-gravimetric analysis. The inline melt flow properties were observed via vertical force measurements. The fracture morphology was investigated using SEM. Mechanical tests showed that the yield strengths of the composites were lower than that of pristine PP; in contrast, the elongation at break and the impact strength of composites enhanced in A-POSS and TS-POSS based composites.

Strong, transparent and flexible aramid nanofiber/POSS hybrid organic/inorganic nanocomposite membranes

Mechanical performance, transparency and thermal stability still remain the dominating constraints for the application of polymeric composite membranes. Thus, the research and development of co-effectively strong, transparent and heat-resistant membranes are necessary and significant for promoting practical outcomes. POSS NPs is incorporate into the structure of aramid nanofibers (ANFs) to synthesize the ANFPs nanocomposite membranes with different amounts of POSS by vacuum-assisted flocculation. FT-IR and XPS were applied to characterize the structure of composite membranes. Upon the addition of POSS, the surface topological structures of composite membranes were not affected, and they retained excellent transparency and flexibility. The mechanical properties of ANFPs membranes could be altered by changing the POSS content, in which the POSS served as a cross-linking agent between nanofibers, and ANFPs composite membrane presented the optimal tensile strength with 6 wt% POSS embedding in the nanocomposite. Besides the excellent mechanical performance and transparency, the unique thermal assets of ANFs and POSS further enabled the membranes with high thermal stability. Based on these results, it could be concluded that the ANFPs membranes developed here might provide the alternative materials for the practical application of strong, transparent and heat-resistant membrane.