Condensed-phase Effects Research Articles

Facile Synthesis of Bis-Diphenylphosphine Oxide as a Flame Retardant for Epoxy Resins.

A phosphorus-containing compound, (oxybis(4,1-phenylene))bis(phenylphosphine oxide) (ODDPO), was successfully synthesized and used as a flame retardant for epoxy resin (EP). The results demonstrated that EP/ODDPO, containing 1.2 wt% phosphorus, achieved a vertical burning V-0 rating, with a limited oxygen index value of 29.2%, indicating excellent flame retardancy. Comprehensive evaluations revealed that ODDPO exhibited both gas-phase and condensed-phase flame-retardant effects on EP, with a particularly notable barrier effect. In addition, the incorporation of ODDPO had a minimal negative impact on the glass transition temperature (Tg) and thermal stability of the EP matrix. Compared to unmodified EP (EP-0), the Tg value and initial decomposition temperature of EP/ODDPO-1.2 decreased by only 7.6 °C and 10.0 °C, respectively. Moreover, the introduction of ODDPO significantly improved the hydrophobicity and water absorption resistance of epoxy materials, which is attributed to ODDPO's rigidity and symmetric structure, reducing water molecule permeation. Furthermore, the dielectric properties of ODDPO-modified EP samples were strengthened compared to EP-0, due to the ODDPO's symmetric structure reducing the polarity of the matrix. The above results indicated that ODDPO serves as an excellent flame retardant while enhancing other properties of the EP matrix, thereby contributing to the preparation and application of high-performance epoxy materials.

Construction of phosphorus-containing polyimine vitrimer film by incorporating ionic liquid BMIM∙PF6 for enhanced mechanical, flame-retardant and reprocessable properties

A composited flame-retardant phosphorus-containing polyimine vitrimer films (Ionic-PIs) were synthesized by using ionic liquid BMIM∙PF6 containing flame retardant elements N, P and F as the regulator. The effects of the addition amount of BMIM∙PF6 on the mechanical properties, degradation, recycling, and flame retardancy were investigated. Compared to intrinsically phosphorus-containing polyimine film (PI), the composited Ionic-PIs exhibited better mechanical strength and toughness. Hydrogen bonding interactions between BMIM∙PF6 and polyimine network greatly increased Ionic-PI’s mechanical strength at a low addition of 1 wt%, and the microphase separation caused by the aggregation of BMIM∙PF6 drastically enhanced their toughness as the addition increased. Ionic-PIs exhibited excellent reprocessability at 85 °C and degradable recyclability under acidic conditions. In addition, due to the synergistic effect of condensed-phase and gas-phase flame-retardant mechanisms, the Ionic-PIs possessed good flame retardancy with LOI above 27 % and a UL-94 test reaching VTM-0 grade, which was important for the high-fire safety of polyimine vitrimer. This work is helpful to provide a simple and feasible strategy to modulate the comprehensive properties of cross-linked polyimine vitrimer film and to expand their applications in many fields.

Comparative study on the flame retardancy, pyrolysis behavior, and flame retardant pathways of black phosphorus in polyurethane and polypropylene

Black phosphorus nanosheets (BPns) have gained widespread attention in the field of flame retardancy due to their highly efficient flame-retardant properties achieved with a low addition rate (e.g., 0.4%). However, the pyrolysis pathways of BP in polymers have not yet been elucidated. This work systematically studies the flame retardancy and pyrolysis behavior of BP in oxygen-containing (polyurethane, PU) and oxygen-free (polypropylene, PP) polymers, distinguishing between the gas-phase and the condensed-phase flame retardant effect of BP. Through slow heating and staged heating methods, the condensed phase and gas phase pyrolysis products of BP in PU and PP at different temperatures are compared in detail. The distinct flame retardant pathways of BP in PU and PP are revealed. The results indicate that the oxidation of BP commences with its reaction with atmospheric oxygen, implying that the condensed-phase flame-retardant effect of BP primarily occurs at the polymer surface. In PP, BP mainly functions as a gas-phase flame retardant. In the condensed phase, BP generates phosphate derivatives that cover the substrate surface, providing solely a physical barrier effect. In PU, while BP demonstrates an outstanding gas-phase flame-retardant effect, it also accelerates the early dehydration carbonization of alcohols within the substrate, resulting in the formation of phosphate ester compounds (P–O–C structure) to bolster the thermal stability of residual carbon. Additionally, the side reactions of BP during catalytic carbonization will decrease the thermal stability of ester bonds in PU. This work lays a theoretical foundation for the development and application of BP-based flame retardant systems.

Quantitative assessment of whether phosphorus-based flame retardants are optimizing or degrading the fire hazard of aircraft carbon fiber/epoxy composites

Fire hazards are a primary concern in aircraft accidents, and controlling combustible materials is pivotal in managing cabin fire risks. This work aims to elucidate the impact of widespread measures that introduce phosphorus-based flame retardants (PFRs) on the fire safety of carbon fiber epoxy composites (CF/EP). Firstly, the hazardous indicators for flame retardant CF/EP composites exhibit two categories of optimization and degradation, which are caused by the intrinsic feature, pyrolysis characteristics and chemical valence states of PFRs. Secondly, the fire hazards of composites are assessed by fusing the analytic network process and information weights guided by Nash Equilibrium theory. The method combines the merits of subjective and objective weights from dimensions of intrinsic hazards, interrelationships and data dispersion of indicators. Finally, the assessed fire hazard rankings under 35 and 65 kW/m2 both are EP > CF/EP16%DOPO-HQ > CF/EP > CF/EP7%DPO. In conclusion, DOPO-HQ (+1) primarily increases the fire hazard of CF/EP due to gas-phase flame-retardant effects, while DPO (+3) predominantly reduces the fire hazard of CF/EP by contributing to condensed-phase effects. This work highlights the contradictory effects of PFRs on the fire safety of CF/EP composites due to structure and thermal stability. The proposed ANP and IW hybridization method provides a theoretical foundation for selecting flame retardants and assessing material fire hazards comprehensively.

Preparation of High-Transparency Phosphenanthrene-Based Flame Retardants and Studies of Their Flame-Retardant Properties.

Transparency is an important property for polymer flame retardants, especially epoxy resin (EP) flame retardants, and flame-retardant epoxy resins that maintain a high transparency and low chromatic aberration play important roles in the optical, lighting, and energy industries. Herein, a DOPO-based flame retardant 6,6'-((sulfonylbis(4,1-phenylene))bis(oxy))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) with a high transparency and low chromatic aberration was prepared via the classical Atherton-Todd reaction and named SBPDOPO. Its chemical structure was characterized with Fourier IR spectroscopy and NMR spectroscopy. An EP loaded with 7 wt% SBPDOPO passed the UL-94 V-0 rating with an LOI value of 32.1%, and the peak heat release rate, total heat release, and total smoke production were reduced by 34.1%, 31.6%, and 27.7%, respectively, compared with those of pure EP. In addition, the addition of SBPDOPO improved the thermal stability, residual mass, and glass transition temperature of the EP. On this basis, the EP containing 7 wt% SBPDOPO maintained a high transparency and low color aberration, with a transmittance of 94% relative to that of pure EP and a color aberration ΔE of 1.63. Finally, the flame-retardant mechanism of SBPDOPO was analyzed, which demonstrated that it exerted both gas-phase and condensed-phase flame-retardant effects, and that SBPDOPO/EP had high potential for application scenarios in which both flame retardancy and transparency are needed. SBPDOPO/EP has great potential for applications requiring both flame retardancy and transparency.

Roles of organic chain structure in flame retardancy and mechanical properties of epoxy coating

Chain structure of flame retardants plays an important role in the performance of epoxy (EP) coatings. Three flame retardants containing hexyl, cyclohexyl and naphthalene were synthesized and marked as DAH, DAC and DAP, respectively. The three flame retardants were used to regulate the flame retardant and mechanical performances of EP coatings. The EP containing 3 wt% DAH displays a UL-94 V0 rating and a limiting oxygen index (LOI) 29.4 vol%, while 6 wt% DAC and >8 wt% DAP are needed to achieve the UL-94 V0 rating. The order of flame-retardant efficiency in UL-94 test is DAH > DAC > DAP, while that in cone calorimetry test is the opposite. The gas-phase effect plays a key role in the former, and the condensed-phase effect decides the heat release behaviors in the later. In addition, the improvement of mechanical property is EPC > EPH > EPP, the EPC4 has an impact strength of 13.4 kJ/m2 which is 168 % higher than that of EP. Toughening is contributed by the increased free volume, flexibility of cyclohexyl and microphase separation.

Facile preparation of inherently flame-retardant polyamide 6 filaments with enhanced anti-dripping enabled by the synergistic charring effect

The absence of inherently flame-retardant polyamide 6 (FR-PA6) with enhanced anti-dripping and melt spinnability has significantly limited its further application in textiles. In this work, a binary reactive flame retardant composed of commercial 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phosphaphenanthrene-10-oxide (DDP) and synthesized polydiphenylsiloxane (PDPS) was employed to fabricate FR-PA6 through a facile synthetic route. The prepared FR-PA6 containing 5 wt% DDP and 5 wt% PDPS (FR-PA6-5-5) exhibited a UL94 V-0 rating with no melt-droplets during combustion, a 31.0% reduction in heat release rate and a 18.8% decrease in total heat release compared to pure PA6 in cone calorimetric tests. The improved fire safety of FR-PA6-5-5 was contributed to the gas-phase quenching and dilution effect and the condensed-phase barrier effect, which was enhanced by the synergistic charring effect achieved through the formation of P(=O)-O-Si. Additionally, FR-PA6-5-5 exhibited excellent melt spinnability as demonstrated by the successful preparation of filaments with a tensile strength of approximately 2.27 cN/dtex.

Sub-keV corrections to binary encounter cross section models for electron ionization of liquid water with application to the Geant4-DNA Monte Carlo code

IntroductionThe electron ionization cross section of water is one of the most important input in Monte Carlo studies of cellular radiobiological effects. Analytical cross section models of the binary-encounter type have the potential of reducing simulation time and facilitate application to a variety of biological materials (other than water). The Binary-Encounter-Bethe (BEB) and Binary-Encounter-Dipole (BED) models of NIST are perhaps the most popular of such models giving reliable results for atoms and molecules in the gas-phase over a wide energy range. However, the use of such models to sub-keV electron energies in liquid water raises concerns due to the neglect of condensed phase effects that leads to a significant overestimation when compared to medium-specific dielectric models. PurposeTo modify the BEB and BED models towards better agreement with the recommended low-energy dielectric model of Geant4-DNA (Option 4). To implement the new modifications to the existing BEB model of the Option 6 physics constructor of Geant4-DNA and re-evaluate fundamental transport quantities for sub-keV electrons. MethodsIn analogy to a Yukawa potential a simple, yet physically-motivated, modification of the Burgess correction term is proposed to account for the reduction of the Coulomb interaction due to the polarizability of the target. The magnitude of the correction is guided by the dielectric-based ionization cross section implemented in Option 4. ResultsDifferential, total and stopping ionization cross sections for low-energy electrons in liquid water are presented. When combined with the Vriens correction (which is not included in Option 6), the proposed modification to the BEB and BED models brings the ionization and stopping cross sections in much better agreement against those used in the Option 4 dielectric model of Geant4-DNA, with up to 30% and 10% deviation, respectively. Implementation of the new correction to the Option 6 constructor of Geant4-DNA and re-evaluation of fundamental transport quantities, such as electron penetration ranges and dose-point-kernels, reduced the discrepancies from Option 4 at sub-keV energies from 20 to 100% (or more) to well below 10% in most cases. ConclusionsA simple modification to the BEB and BED analytic models was found to improve their performance for sub-keV electrons in liquid water medium. Implementation of the new modification to the Option 6 constructor of Geant4-DNA significantly improved the agreement with the recommended low-energy Option 4 constructor for a variety of fundamental quantities related to electron transport.

Preparation and Mechanism of Toughened and Flame-Retardant Bio-Based Polylactic Acid Composites

As a biodegradable thermoplastic, polylactic acid (PLA) shows great potential to replace petroleum-based plastics. Nevertheless, the flammability and brittleness of PLA seriously limits its use in emerging applications. This work is focused on simultaneously improving the flame-retardancy and toughness of PLA at a low additive load via a simple strategy. The PLA/MKF/NTPA biocomposites were prepared by incorporating alkali-treated, lightweight, renewable kapok fiber (MKF) and high-efficiency, phosphorus-nitrogenous flame retardant (NTPA) into the PLA matrix based on the extrusion-injection molding method. When the additive loads of MKF and NTPA were 0.5 and 3.0 wt%, respectively, the PLA/MKF/NTPA biocomposites (PLA3.0) achieved a rating of UL-94 V-0 with an LOI value of 28.3%, and its impact strength (4.43 kJ·m-2) was improved by 18.8% compared to that of pure PLA. Moreover, the cone calorimetry results confirmed a 9.7% reduction in the average effective heat of combustion (av-EHC) and a 0.5-fold increase in the flame retardancy index (FRI) compared to the neat PLA. NTPA not only exerted a gas-phase flame-retardant role, but also a condensed-phase barrier effect during the combustion process of the PLA/MKF/NTPA biocomposites. Moreover, MKF acted as an energy absorber to enhance the toughness of the PLA/MKF/NTPA biocomposites. This work provides a simple way to prepare PLA biocomposites with excellent flame-retardancy and toughness at a low additive load, which is of great importance for expanding the application range of PLA biocomposites.

Microdosimetry Study of Proton Quality Factor Using Analytic Model Calculations

The quality factor (Q) is formally linked to the stochastic (e.g., carcinogenic) risk of diverse ionizing radiations at low doses and/or low dose rates. Q can be a function of the non-stochastic physical quantity Linear Energy Transfer (LET) or the microdosimetric parameter lineal energy (y). These two physical quantities can be calculated either by Monte Carlo (MC) track-structure simulations or by analytic models. In this work, various generalized analytical models were utilized and combined to determine the proton lineal energy spectra in liquid water spheres of various sizes (i.e., 10–3000 nm diameter) over the proton energy range of 1–250 MeV. The calculated spectra were subsequently used within the Theory of Dual Radiation Action (TDRA) and the ICRU Report 40 microdosimetric methodologies to determine the variation of Q¯ with proton energy. The results revealed that the LET-based Q values underestimated the microdosimetric-based Q¯ values for protons with energy below ~100 MeV. At energies relevant to the Bragg peak region (<20–30 MeV), the differences were larger than 20–50%, while reaching 200–500% at ~5 MeV. It was further shown that the microdosimetric-based Q¯ values for protons below ~100 MeV were sensitive to the sphere size. Finally, condensed-phase effects had a very small (<5%) influence on the calculated microdosimetric-based Q¯ over the proton energy range considered here.

Pyrolytic activation of cellulose: energetics and condensed phase effects

Computational strategies used to capture condensed phase effects provide a novel outlook on cellulose chemistry. With phase transition, cellulose primary decomposition has a significant entropic penalty below 900 K but is enthalpy controlled beyond.

Phosphorous-phosphorous synergistic effect on flame retardancy, mechanically reinforce and hydrolytic resistance for PC/ABS blends

The pursuit of highly efficient phosphorous flame retardants for polymer-matrix composites is of great sense in industrial and academic community. In the contribution, a phosphorous-phosphorous (P-P) synergy between structurally well-defined phosphonium sulfonates (PhS) and triphenyl phosphate (TPP) or bisphenol A bis (diphenyl phosphate) (BDP) was specifically revealed in PC/ABS alloy. Compared with TPP and BDP loadings of respective 14 wt% and 12 wt% to pass UL-94 V-0, the mere 8 wt% FRs was required via an exceptional synergy of 2% allyl-substituted PhS and 6 wt% TPP (or BDP). In parallel, the studied P-P synergy reduced heat release rate and total heat release significantly. Deep mechanism analysis by solid NMR and Py/GC-MS unveiled a concurrent optimization of condensed-phase and vapor-phase effect. Additionally, the multifunctional reinforcement of tensile property, thermal resistance and hydrolytic resistance was sysmatically investigated. In perspective, the P-P synergy between structurally tailored PhSs and phosphates exploits a pathway for highly efficiently fire-safe polymers.

Screened Range-Separated Hybrid Functional with Polarizable Continuum Model Overcomes Challenges in Describing Triplet Excitations in the Condensed Phase Using TDDFT.

Long range-corrected (LRC) or range-separated hybrid (RSH) functionals where the long-range (LR) limit of electronic interactions is set to the exact exchange have been shown to correct the tendency of traditional density functional theory (DFT) to underestimate the frontier orbital gap. Consequently, the use of such functionals in calculating electronic excited states using linear response based time-dependent DFT (TDDFT) has been successful in correcting the tendency for underestimating the energies of charge transfer states by DFT-based calculations. More recently formulations of functionals that attenuate the LR limit to address condensed-phase effects to polarize the electronic density have been reported. In particular screened RSH (SRSH) combined with polarizable continuum model (PCM) was benchmarked successfully in reproducing the fundamental gap and charge transfer state energies of molecular systems in the condensed phase. Here we use SRSH-PCM to address triplet excited states, and show its success in obtaining correspondence of the low-lying triplet states to the singlet-triplet gap in a similar way that the fundamental orbital gap corresponds to electron removal and addition energies. Importantly, the accuracy of the SRSH-PCM in calculating triplet excitations stands on the polarization consistent framework in addressing the scalar dielectric constant and without affecting the optimal tuning by triplet energies. The prospect of even further improving the SRSH-PCM accuracy in calculating triplet states can be achieved by optimal tuning on the basis of the spin multiplicity gap.

Intumescent flame retardant behavior of charring agents with different aggregation of piperazine/triazine groups in polypropylene

To explore the structure mode of charring agent with higher flame retardant efficiency, two charring agents (PT-Cluster and PT) with different aggregation structure of piperazine/triazine groups were synthesized and characterized, and then were applied to preparing intumescent flame retardant polypropylene (PP) composites with ammonium polyphosphate (APP). Both PT-Cluster/APP/PP and PT/APP/PP composites performed excellent intumescent flame retardant effects. The values of LOI reached over 32% while the mass ratio of charring agent was only 3 wt% in the case of 25 wt% IFR loading. The pk-HRR values of 5%PT-Cluster/20%APP/75%PP and 5%PT/20%APP/75%PP were 242 kW/m2 and 330 kW/m2, respectively, which were all decreased by over 73% compared with neat PP. Besides, the total heat release (THR) and average effective heat of combustion (av-EHC) of charring agent/APP/PP were also decreased. More importantly, the aggregated piperazine/triazine groups in PT-Cluster further raised the flame retardant efficiency of charring agent/APP system. PT-Cluster/APP system brought higher residue yields and lower THR, av-EHC and total smoke release than PT/APP in cone calorimeter test, implying that PT-Cluster/APP exhibited better charring and barrier effect, and more effective quenching effect than PT/APP during combustion. The enhanced flame retardant effect was resulted by the aggregated piperazine/triazine groups in PT-Cluster. By means of the macromolecular structure of PT-Cluster, more residues were remained in condensed phase and more phosphorus-containing components were released to gas phase. Accordingly, PT-Cluster/APP performed better condensed-phase and gas-phase effects than PT/APP.

Novel Thermoset Nanocomposite Intumescent Coating Based on Hydroxyapatite Nanoplates for Fireproofing of Steel Structures

Thermoset nanocomposite intumescent coating swells under the influence of heat forming a thick cohesive insulating barrier; it is one of the most effective ways for fire protection of steel structures. This study reports on the sustainable fabrication of hydroxyapatite (HA) nanoplates as an efficient phosphorous-based flame retardant agent (phosphorous content of 18.5 wt%). Epoxy nanocomposite, based on the synergism between HA particles and advanced intumescent flame retardant agent (commercially known as AP750) was developed. This novel nanocomposite was able to resist a direct flame source at 1700 °C and to self extinguish; it demonstrated an enhanced flammability performance in cone calorimetry with 51% decrease in the peak heat released. Nanocomposite layer of 3 mm thickness was employed for steel substrate protection against direct heat source. The developed intumescent coating was able to protect the steel substrate from heat source at 900 °C. It offered an improved performance, in terms of the coating’s mechanical barrier, and flame resistance properties. HA nanoplates could propose a gas phase effect due to the release of active flame scavengers such as $$ {\text{PO}}_{2}^{ \cdot } $$, PO·, and HPO·. Furthermore, HA could expose a condensed phase effect via the formation of a protective charr layer.

Aluminum hypophosphite and aluminum phenylphosphinate: A comprehensive comparison of chemical interaction during pyrolysis in flame-retarded glass-fiber-reinforced polyamide 6

This study compared thermal degradation, pyrolysis behavior, and the fire behavior of flame-retarded glass-fiber-reinforced polyamide 6 with aluminum hypophosphite and aluminum phenylphosphinate (BPA-Al), respectively. We sythesize aluminum phenylphosphinate by benzenephosphinic acid (BPA) and AlCl3.6H2O in water. so we call aluminum phenylphosphinate BPA-Al for short. The dependence of limiting oxygen index on phosphorus content was linear for aluminum hypophosphite and BPA-Al. Thermogravimetric analysis proved aluminum hypophosphite was less stable than BPA-Al. Thermogravimetric-Fourier transform infrared tests showed that aluminum hypophosphite system balanced the charring process and the gas releasing well, and that BPA-Al system enhanced the charring process and decreased the gas releasing. Peak heat release rate and total heat release data proved that aluminum hypophosphite system was superior to BPA-Al system in lowering the heat release. Their differences were caused by different P-H (aluminum hypophosphite) and P-phenyl (BPA-Al) structures. P-H structure did better than P-phenyl structure in balancing the condensed phase effect and the gaseous phase action. So P-H structure (aluminum hypophosphite) was more suitable than P-phenyl structure (BPA-Al) in the flame retardancy of glass-fiber-reinforced polyamide 6.

Preparation, characterization and flame retardancy of phosphorus-containing poly-styrene-acrylate emulsion

ABSTRACTPhosphorus (P)-containing monomer (P-monomer) was firstly prepared by condensation reaction between 2-hydroxyethyl methacrylate and phosphorus pentoxide (P2O5) and then used to prepare P-containing poly-styrene-acrylate (P-PSA) emulsion by semi-continuous emulsion polymerization. The components of the prepared P-monomer were characterized by potentiometric titration method. The chemical composition of the P-PSA co-polymer was studied by Fourier-transform infrared spectra. The storage stability properties of P-PSA emulsion were tested by Ca2+, centrifugal and mechanical stability tests. The thermal stability and flame retardancy of the P-PSA co-polymer were studied by thermogravimetric analysis, limiting oxygen index and UL-94 method. The results show that stable P-PSA emulsions can be successfully prepared, and the latex particles present a spherical structure. When the P-monomer content is 30 wt%, the P-PSA co-polymer can pass the UL-94 test (V0 level) and the char yield is 54 wt% at 700°C. Scanning electron microscopy results indicate that incorporation of the P-monomer shows a condensed-phase flame-retardant effect. This study provides useful suggestions for the application of the flame-retardant P-PSA emulsion in the coating industry.

Thermal degradation and combustion behavior of flame-retardant epoxy resins with novel phosphorus-based flame retardants and silicon particles

The investigation focuses on the effect of silicon particles (Si) and phosphorus-based flame retardants on the flame retardancy of epoxy resins. The flame-retardant properties have been studied by limiting oxygen index, vertical burning test, cone calorimeter test and micro-combustion calorimeter. The results demonstrate that Si, FR and APP can greatly improve the flame-retardant and thermal properties. It is found that the addition of Si/APP/FR can promote the formation of stable char layers, indicating the condensed-phase effect of the flame retardants.

Impact of finite-temperature and condensed-phase effects on theoretical X-ray absorption spectra of transition metal complexes.

The impact of condensed-phase and finite-temperature effects on the theoretical X-ray absorption spectra of transition metal complexes is assessed. The former are included in terms of the all-electron Gaussian and augmented plane-wave approach, whereas the latter are taken into account by extensive ensemble averaging along second-generation Car-Parrinello ab initio molecular dynamics trajectories. We find that employing the periodic boundary conditions and including finite-temperature effects systematically improves the agreement between our simulated X-ray absorption spectra and experimental measurements. © 2018 Wiley Periodicals, Inc.

The effect of the condensed-phase environment on the vibrational frequency shift of a hydrogen molecule inside clathrate hydrates.

We report a theoretical study of the frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the vibrational frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2-H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the vibrational state of H2, v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H2-H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 vibrational frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the vibrational frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.