Synthesis of poly(ε‐caprolactone)/clay nanocomposites using polyhedral oligomeric silsesquioxane surfactants as organic modifier and initiator

Poly(ε‐caprolactone)/clay nanocomposites were synthesized by in situ ring‐opening polymerization of ε‐caprolactone in the presence of montmorillonite modified by hydroxyl functionalized, quaternized polyhedral oligomeric silsesquioxane (POSS) surfactants. The octa(3‐chloropropyl) polyhedral oligomeric silsesquioxane was prepared by hydrolytic condensation of 3‐chloropropyltrimethoxysilane, which was subsequently quaternized with 2‐dimethylaminoethanol. Montmorillonite was modified with the quaternized surfactants by cation exchange reaction. Bulk polymerization of ε‐caprolactone was conducted at 110°C using stannous octoate as an initiator/catalyst. Nanocomposites were analyzed by X‐ray diffraction, transmission electron microscopy, thermo gravimetric analysis, and differential scanning calorimetry. Hydroxyl functionalized POSS was employed as a surface modifier for clay which gives stable clay separation for its 3‐D structure and also facilitates the miscibility of polymer with clay in the nanocomposites due to the star architecture. An improvement in the thermal stability of PCL was observed even at 1 wt % of clay loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(ɛ‐caprolactone)/polyhedral oligomeric silsesquioxane hybrids: Crystallization behavior and thermal degradation

Biodegradable organic–inorganic hybrids based on poly(?‐caprolactone) (PCL) and polyhedral oligomeric silsesquioxane (POSS) with 5.3–21.3 wt % POSS were synthesized via ring‐opening polymerization (ROP). Chemical structures of the polymers were characterized by proton nuclear magnetic resonance (¹H NMR), fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). X‐ray diffraction (XRD) analysis illustrated that both POSS and PCL segment in POSS/PCL hybrids could crystallize and form two well‐separated crystalline phases except in the one with low content of POSS (5.3 wt %). Melting behavior and non‐isothermal crystallization kinetics of POSS/PCL hybrids were studied by differential scanning calorimeter (DSC). The results indicated that the POSS segment suppressed crystallization of the PCL segment to some extent. Polarizing optical microscope (POM) images showed that POSS/PCL hybrids with the highest POSS loading (21.3 wt %) possessed “snowflake” shape crystals whereas the ones with relatively low POSS loading exhibited classic spherulites. Thermogravimetry (TG) measurement revealed that thermal degradation of POSS/PCL hybrids proceeded by four‐step while PCL homopolymers degraded by a single step. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44113.     

Performance enhancement of polylactide by nanoblending with POSS and graphene oxide

We report the effect of filler modification on the properties of polylactide (PLA)‐based nanocomposites, where graphene oxide (GO) nanosheets and polyhedral oligomeric silsesquioxane (POSS) nanocages are employed as nanofillers. The organically treated nanofillers are termed as GO‐functionalized and POSS‐functionalized. The synthesis of the nanocomposites was carried out via in situ ring‐opening polymerization of lactic acid (LA). The following four naocomposite systems were prepared, characterized, and compared to achieve a better understanding of structure‐property relationship (1) PLA/GO‐functionalized, (2) PLA/POSS‐functionalized, (3) PLA/physical mixture of GO‐functionalized and POSS‐functionalized, and (4) PLA/GO‐graft‐POSS (with eight hydroxyl groups). As revealed by the thermal and mechanical (nanoindendation) characterization, that the nanocomposites having a combination of GO and POSS as nanofiller, either as physical mixture of GO‐functionalized and POSS‐functionalized or as GO‐graft‐POSS, is far more superior as compared with the nanocomposites having individually dispersed nanofillers in the PLA matrix. Observed enhancement is attributing to the synergistic effect of the nanofillers as well as better dispersion of the modified‐fillers in the matrix. POLYM. COMPOS., 35:118–126, 2014. © 2013 Society of Plastics Engineers     

High‐performance nanocomposites derived from allyl‐terminated benzoxazine and octakis(propylglycidyl ether) polyhedral oligomeric silsesquioxane

In this study, we used the Mannich condensation of bisphenol A, formaldehyde, and allylamine to synthesize a allyl‐terminated benzoxazine (VB‐a), which can be polymerized through ring opening polymerization. We used this VB‐a monomer, blended with octakis(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OG‐POSS), to prepare polybenzoxazine/POSS nanocomposites. Differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy revealed that the mechanism of the crosslinking reaction leading to the formation of the organic/inorganic network involved two steps: (i) ring opening and allyl polymerizations of VB‐a and (ii) subsequent reactions between the in situ‐formed phenolic hydroxyl groups of VB‐a and the epoxide groups of OG‐POSS. Dynamic mechanical analysis revealed that the nanocomposites had higher mechanical properties than did the control VB‐a. In the glassy state, nanocomposites containing less than 10 wt % POSS displayed enhanced storage moduli; those of the nanocomposites containing greater than 10 wt % POSS were relatively low, due to aggregation, as determined using scanningelectron microscopy. Thermogravimetric analysis indicated that the nanocomposites possessed greater thermal stability than that of the pure polymer. FTIR spectroscopic analysis revealed the presence of hydrogen bonding between the siloxane groups of POSS and the OH groups of the polybenzoxazine. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Blends of poly(d,l‐lactide) with polyhedral oligomeric silsesquioxanes‐based biodegradable polyester: Synthesis,morphology, miscibility,and mechanical property

A highly branched hybrid copolymer based on polyhedral oligomeric silsesquioxane (POSS) was designed to improve the brittleness of poly(d,l‐lactide) (PDLLA). The toughening material was synthesized using POSS‐OH as the core, which initiated the ring‐opening polymerization of ε‐caprolactone and d,l‐lactide sequentially to form the highly branched POSS‐g‐poly (ε‐caprolactone)‐b‐poly(d,l‐lactide) (POSS‐g‐PCL‐b‐PLA) copolymer with eight PCL‐b‐PLA arms. The POSS‐g‐PCL‐b‐PLA copolymer had a very good dispersion in the PDLLA matrix with the size of microdomains smaller than 1 µm when added at a low content below 10 wt %. In related to the nano‐scale size of microdomains in the blends, the crystallinity of PCL blocks was significantly suppressed. Thus, the addition of POSS‐g‐PCL‐b‐PLA is very effective to improve the roughness of the matrix polymer when added at a low content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40776.     

Synthesis and characterization of poly (imide–benzimidazole) hybrid nanocomposites using nano‐cluster of octa‐amino functionalized polyhedral oligomeric silsesquioxane

Poly (imide–benzimidazole)/polyhedral oligomeric silsesquioxane (POSS), nanocomposites were prepared by the reaction of the heterocyclic diamine monomer 2,2‐(1,2‐phenylene)‐bis(5‐aminobenzimidazole), octa(aminophenyl)silsesquioxane(OAPS), and benzophenonetetra carboxylic dianhydride (BTDA). The structure of the prepared monomers was confirmed by FTIR and NMR (²⁹Si, ¹H, and ¹³C) spectral studies. The thermal stability behavior of the poly (imide–benzimidazole) and poly (imide–benzimidazole)–POSS nanocomposite films were studied by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). Dynamic mechanical analysis shows that the glass transition temperatures of the polyhedral oligomeric silsesquioxane (POSS) containing poly (imide–benzimidazole) nanocomposites are higher than that of the corresponding neat poly (imide–benzimidazole) systems. Decrease in the dielectric constant was observed with an increase in the determined amount of amino‐functionalized POSS in the poly (imide–benzimidazole) matrix. Further, the morphological studies were carried out by X‐ray diffraction and transmission electron microscopy. POLYM. COMPOS., 34:825–833, 2013. © 2013 Society of Plastics Engineers     

Isothermal crystallization of HDPE/octamethyl polyhedral oligomeric silsesquioxane nanocomposites: Role of POSS as a nanofiller

The isothermal crystallization of HDPE/POSS (polyhedral oligomeric silsesquioxane) nanocomposites (POSS content varying from 0.25 to 10 wt %) was studied using differential scanning calorimetry (DSC) technique. The Avrami model could successfully describe the isothermal crystallization behavior of the nanocomposites. The value of Avrami exponent (n) varies between 2 and 2.5 for all the compositions studied. For a given composition, the values vary with crystallization temperature and in general increased with POSS content up to 1 wt % POSS content and decreased thereafter. The presence of POSS was found to increase the rate of crystallization, which manifested itself in the increased value of the Avrami rate constant (K) and reduced value of crystallization half‐time (t_1/2). The rate of crystallization peaked at 1 wt % POSS content and was almost constant at higher POSS loadings. X‐ray diffraction studies revealed that POSS exists as nanocrystals in HDPE matrix while some POSS gets dispersed at molecular level too. It is observed that only the POSS dispersed at molecular level acts as a nucleating agent while the POSS nanocrystals do not affect the crystallization process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Thermal pressure coefficient of a polyhedral oligomeric silsesquioxane (POSS)‐reinforced epoxy resin

The thermal pressure coefficients of a neat, unfilled, epoxy resin and a 10 wt % POSS (polyhedral oligomeric silsesquioxane)‐filled epoxy nanocomposite have been measured using a thick‐walled tube method. It is found that just below the glass transition temperature the thermal pressure coefficient is ～ 20% smaller for the polymer composite containing 10% POSS than for the neat, unfilled resin. The thermal expansion coefficient and thermal pressure coefficient of the uncured POSS itself are also reported. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microwave‐assisted preparation of polylactide/organomontmorillonite nanocomposites via in situ polymerization

Microwave technology was introduced to assist the synthesis of polylactide (PLA)/organomontmorillonite (OMMT) nanocomposites in bulk by the in situ ring‐opening polymerization of D,L ‐lactide. Factors that influenced the polymerizing effects, such as the microwave power, irradiation time, and dosages of the catalyst and OMMT, were studied in terms of tensile strength. The polymerization time was decreased dramatically to 10 min under 90 W of microwave irradiation, and the mechanical and thermal properties of the PLA/OMMT nanocomposites were significantly improved. The composite with the highest mechanical properties was obtained when the dosages of the OMMT and the catalyst were 1.0 and 0.6 wt % of the lactide, respectively. The initial decomposition temperature of the PLA/OMMT(1.0 wt % OMMT) nanocomposite was heightened 11.5°C compared with that of pure PLA. The results of scanning electron microscopy confirmed an improvement in the toughness with the addition of OMMT. The transmission electron microscopy and X‐ray diffraction results indicate that an exfoliated and intercalated nanocomposite was successfully prepared. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Morphology and rheological behaviors of poly(ethylene terephthalate) nanocomposites containing polyhedral oligomeric silsesquioxanes

Poly(ethylene terephthalate) (PET)/polyhedral oligomeric silsesquioxane (POSS) nanocomposites were prepared by in situ polymerization. Light scattering measurement suggested that there is significant change in molecular weight arising from gel formation by chemical crosslinking during polymerization. The thermal decomposition temperatures of the composites measured at 5 wt % weight loss were 5–10°C higher than that of PET. There is no significant change in other thermal properties. Scanning electron microscopy observations suggest that there is obvious phase separation in PET/POSS composites, composites containing 1 wt % of disilanolisobutyl and trisilanolisobytyl‐POSS show fine dispersions of POSS (30–40 nm in diameter), which arise from strong interfacial interactions between POSS and PET during polymerization. The viscosity of the composites increased with the addition of POSS. The observation of a plateau region of composites containing 1 wt % of POSS in the plot of log G′ vs. log G″ indicates strong interfacial interactions between POSS and PET. Sixty‐three percent and 41% increase in tensile strength and 300 and 380% increase in modulus were achieved in the composites containing 1 wt % of disilanol‐ and trisilanol‐POSS, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,structure, and properties of high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane nanocomposites

The organic–inorganic hybrid nanocomposites from high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane (HIPS/POSS) containing various percentages of POSS were prepared by free radical polymerization and characterized by Fourier transform infrared spectroscopy (FTIR), ¹H‐NMR, thermal gravity analysis (TGA), X‐ray diffraction (XRD), and transmission electron microscopy (TEM). The octavinyl POSS has formed covalent bond connected PS‐POSS hybrid with polystyrene. POSS can well disperse in the composites at the composition of 0.5 and 1 wt%. The mechanical properties and thermostability of HIPS/POSS nanocomposites were significantly improved. The tensile strength, the izod impact strength, and the elongation at break of the nanocomposite containing 1 wt% of POSS was increased, respectively, by 15.73%, 75.62%, and 72.71% in comparison with pristine HIPS. The thermal decomposition temperature of HIPS/POSS (1 wt% of POSS) was 33°C higher than that of pristine HIPS. The HIPS/POSS nanocomposites showed great potential for applications in many fields, such as electric appliance and automotive trim. POLYM. COMPOS. 37:1049–1055, 2016. © 2014 Society of Plastics Engineers     

Crystallization behavior of ultrahigh‐molecular‐weight polyethylene/polyhedral oligomeric silsesquioxane nanocomposites prepared by ethylene in situ polymerization

A [3‐t‐Bu‐2‐O? C₆H₃CH?N(C₆F₅)]₂TiCl₂ catalyst (bis(phenoxyimine)titanium dichloride complex – FI catalyst) was immobilized on disilanolisobutyl polyhedral oligomeric silsesquioxane (OH‐POSS) to prepare ultrahigh molecular‐weight polyethylene (UHMWPE)/polyhedral oligomeric silsesquioxane (POSS) nanocomposites during ethylene in situ polymerization. The dispersion state of POSS in the UHMWPE matrix was characterized by X‐ray diffraction measurements and transmission electron microscopy. It was shown that the OH‐POSS achieved uniformed dispersion in the UHMWPE matrix, although its polarity was unmatched. The isothermal and nonisothermal crystallization behavior of the nanocomposites was investigated by means of differential scanning calorimetry. The crystallization rate of the nanocomposites was enhanced because of the incorporation of POSS during the isothermal crystallization. POSS acted as a nucleus for the initial nucleation and the subsequent growth of the crystallites. For nonisothermal studies, POSS showed an increase in the crystallinity. The crystallization rate of the nanocomposites decreased because the presence of POSS hindered the crystal growth. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40847.     

Crystallization,morphology, and mechanical properties of poly(butylene succinate)/poly(ethylene oxide)‐polyhedral oligomeric silsesquioxane nanocomposites

The biodegradable poly(butylene succinate) (PBS)/poly(ethylene oxide)‐polyhedral oligomeric silsesquioxane (PEO‐POSS) nanocomposites were prepared by the solution blending and melt‐injection methods. The effect of PEO‐POSS on the non‐isothermal and isothermal crystallization, morphology, as well as mechanical properties of PBS was carefully investigated. The PEO‐POSS nanoparticles dispersed well in the PBS matrix, with the diameters around 30 nm. From isothermal crystallization analysis, the incorporation of PEO‐POSS enhanced the crystallization of PBS due to the heterogeneous nucleation effect while the crystal structure of PBS remained. PBS/PEO‐POSS nanocomposites showed of higher glass transition temperatures than that of neat PBS, attributing to the existence of PEO‐POSS decreasing the flexibility of PBS chains. The elongation at break of the PBS/PEO‐POSS nanocomposites reached the maximum value with PEO‐POSS content of 5 wt%. However, the elastic modulus of PBS decreased after the incorporation of PEO‐POSS. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Poly(ethylene glycol)–polyhedral oligomeric silsesquioxane as a novel plasticizer and thermal stabilizer for poly(vinyl chloride) nanocomposites

The plasticizing and thermostabilizing effect of poly(ethylene glycol)–polyhedral oligomeric silsesquioxane (PEG‐POSS) on poly(vinyl chloride) (PVC) is discussed thoroughly in this work. As PEG‐POSS content increases, PVC becomes more flexible and the decomposition temperature of PVC increases slightly. Meanwhile, the temperature of maximum HCl emission is elevated from 265.3 °C in neat PVC to 285.7 °C in PVC nanocomposites, with the peak intensity of HCl emission decreased by 30.8%, and a new lower intensity of HCl emission peak appearing at much higher temperature (around 370 °C), which is in accordance with the maximum degradation temperature of PEG‐POSS. Thereby, a possible dehydrochlorination mechanism is suggested according to the fact that the electron donor effect of ether groups would stabilize the C? Cl bonds by means of more electron cloud stacked in those bonds, which agrees with Fourier transform infrared and X‐ray photoelectron spectroscopy experiments in terms of hydrogen bonds. © 2016 Society of Chemical Industry     

Enhanced nonisothermal and isothermal cold crystallization kinetics of biodegradable poly(l‐lactide) by trisilanolisobutyl‐polyhedral oligomeric silsesquioxanes in their nanocomposites

In this work, the nonisothermal and isothermal cold crystallization behaviors of poly(l ‐lactide) (PLLA)/trisilanolisobutyl‐polyhedral oligomeric silsesquioxanes (tsib‐POSS) nanocomposites with low tsib‐POSS contents were fully investigated. For all the samples, the variations of heating rate and the tsib‐POSS loading may influence the nonisothermal cold crystallization of PLLA. During the nonisothermal crystallization kinetics study, the Ozawa equation failed to fit the nonisothermal crystallization process of PLLA, while the Tobin equation could fit it well. For the isothermal crystallization kinetics study, the crystallization rates of all the samples increased with increasing crystallization temperature. The cold crystallization activation energy of PLLA was increased with 1 wt % tsib‐POSS. Moreover, the addition of tsib‐POSS and the increment of tsib‐POSS loading could increase the crystallization rate of PLLA, indicating the nucleating agent effect of tsib‐POSS. However, the crystallization mechanism and crystal structure of PLLA remained unchanged in the nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43896.     

Synthesis and characterization of UV-cured epoxy acrylate/POSS nanocomposites

In this study, epoxy acrylate (EA)/vinyl-polyhedral oligomeric silsesquioxane (POSS) nanocomposites were prepared through in situ polymerization and by UV-curing technique. The vinyl-POSS monomers were added to EA matrix by physically blending at loadings between 0 wt.% and 15 wt.%. The microstructure of the EA/vinyl-POSS composites was studied by X-ray diffraction (XRD) measurements, and the result indicated that the separate POSS domains were present in EA/POSS composites. Aggregates were observed in the nanocomposites by SEM and the EDS results indicated that there were vinyl-POSS molecules existing in the EA matrix. TEM images further proved there were both POSS aggregates and monomers dispersed in the EA matrix. The kinetics of the photopolymerization was investigated by real time FTIR spectroscopy. The DSC analysis showed that the increasing POSS content caused a decrease on the composite's glass transition temperature. TGA measures confirmed that the degradation mechanism of EA was not affected by POSS and the nanocomposites thermal stability was slightly improved with the increasing of POSS loadings. It can be seen that the degradation rate slowed down with the increasing of POSS content and the 50% mass loss temperature of EA/POSS hybrids all increased conspicuously relative to plain EA.     

Allylated novolac/4,4′‐bismaleimidodiphenylmethane resin containing polyhedral oligomeric silsesquioxane: Preparation,morphology and thermal stability

Allylated novolac/4,4′‐bismaleimidodiphenylmethane resin (AN/BDM) had been modified with well‐defined inorganic building blocks‐polyhedral oligomeric silsesquioxane (POSS). Octamaleimidophenyl polyhedral silsesquioxane (OMPS) was used as the cocuring reagent of the AN/BDM resin to prepare POSS‐modified AN/BDM resin, and POSS content was between 0 and 17.8 wt %. The curing reaction of the POSS‐modified AN/BDM resin was monitored by means of Fourier transform infrared spectroscopy (FTIR), and the results revealed that maleimide groups on OMPS molecule could undergothe curing reaction between allyl groups and maleimide groups. Therefore, the crosslinked network containing POSS was formed. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) were employed to study the morphology of the cured POSS‐modified AN/BDM resins. The homogeneous dispersion of POSS cages in AN/BDM matrices was evidenced. Thermogravimetric analysis (TGA) indicated that incorporation of POSS into AN/BDM crosslinked network led to enhanced thermal stability. The improved thermal stability could be ascribed to higher crosslink density and inorganic nature of POSS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3903–3908, 2007     

Nanocomposites based on copolymers of fluorinated imide and polyhedral oligomeric silsesquioxane macromonomer: microstructure and morphology studies

Towards the development of copolymeric nanocomposites, N‐3(trifluoromethyl)phenyl‐7‐oxanorbornene‐5,6‐dicarboximide (TFI) monomer and a macromonomer of polyhedral oligomeric silsesquioxane (POSS) were synthesized. Ring‐opening metathesis polymerization to copolymerization of specified proportions of the two co‐monomers was carried out. All the monomers and polymers were characterized using Fourier transform IR analysis and ¹H and ²⁹Si NMR. Gel permeation chromatography shows that copolymeric nanocomposites have a lower average molar mass than a homopolymer of TFI (HTFI). TGA shows that the thermal stability of the copolymer is inversely proportional to the proportion of POSS units. DSC studies have demonstrated that the glass transition temperature (T_g) of a nanocomposite possessing 25 wt% POSS is at a higher temperature (180 °C) than that of HTFI (175 °C). Transmission electron microscopy and AFM images of copolymers are consistent with the self‐assembled spherical aggregation of POSS units, while X‐ray diffraction studies have confirmed the homogeneous dispersion of the same units within the nanocomposites. © 2012 Society of Chemical Industry     

High molecular weight poly (L‐lactic acid) clay nanocomposites via solid‐state polymerization

We propose here, a novel technique to synthesize high molecular weight (MW) poly (L ‐lactic acid)‐clay nanocomposite (PLACN), via solid state polymerization (SSP). We synthesize prepolymer of PLACN (pre‐PLACN) from both, L ‐lactic acid and L ‐lactide, as starting materials. Synthesis of pre‐PLACN from L ‐lactic acid is carried out via in situ melt polycondensation (MP) of L ‐lactic acid oligomer, followed by SSP, to achieve high MW PLACN (M_w ∼ 138,000 Da). In case of L ‐lactide as the starting material, we prepare L ‐lactide–clay intercalated mixture which yields moderate MW pre‐PLACN during subsequent ring opening polymerization (ROP). Interestingly, ROP is performed by using hydroxyl functionalized ternary catalyst system (L ‐lactide–Sn(II) octoate–oligo (L‐lactic acid) complex), which provides the terminal hydroxyl end‐groups, required for step‐growth SSP. Pre‐PLACN MW is now increased to M_w ∼ 127,000 Da, by the subsequent SSP process. ¹H NMR analyses confirm that these end‐groups, are indeed consumed during SSP. During SSP, the PLACN also achieves up to 90% crystallinity, which may be due to the synchronization of the slow step‐growth SSP of poly(L ‐lactic acid) (PLA) with the crystallization kinetics. Optical purity of PLACNs is similar to that of neat PLA, whereas the thermal stability of PLACNs is significantly superior. As evidenced by wide‐angle X‐ray scattering/small‐angle X‐ray scattering analyses and in line with the literature, both, intercalated and exfoliated PLACN morphologies, have been synthesized, by suitable selection of clays. We also verify the correlation between the PLA semicrystalline morphology and the PLACN morphology, which is consistent with those of PLACN synthesized by other techniques. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Studies on Polybenzoxazine/Capron PK4/octakis(dimethylsiloxypropylglycidylether) Silsesquioxane Nanocomposites for Radiation Resistant Applications

Polymeric materials can erode when exposed to the radiation environment that includes atomic oxygen (AO), ultraviolet (UV) ionizing radiation, and ultrahigh vacuum (UHV). Many studies have been devoted to develop polymeric materials that can withstand decades of exposure on radiation. In this connection an attempt has been made to develop polyhedral oligomeric silsesquioxane (POSS) reinforced capron PK₄ (CPL) modified polybenzoxazine nanocomposites in the present work and to assess their ability to resist radiation for a prolonged period. Varying weight percentages of (0, 1, 3, and 5 wt%) POSS were reinforced in to 1:1 (w/w) PBZ/CPL copolymerization through chemical ring opening polymerization. The POSS reinforced PBZ/CPL nanocomposites have been studied their tensile strength and morphological behavior before and after exposure of UV irradiation. Data resulted from the studies indicated that the neat PBZ-CPL has significantly eroded after UV exposure, whereas POSS reinforced PBZ/CPL composites have eroded only an insignificant extent and the value of tensile properties are reduced to a small extent. The POSS reinforced nanocomposites during exposure under UV radiation undergo changes on the surface and lead to the formation of silica (Si-O-Si) passivation layer. The formation of silica layer protects (act as inert layer) from further erosion of the composites and was ascertained from SEM images. Data obtained from thermal and dielectric studies indicate that thermal stability and dielectric behavior of composites were appreciably improved when compared with those of neat PBZ/CPL matrix.