Polymer Degradation and Stability (v.105, #C)

The effect on flame retardancy in polycaprolactam composites with the combination of aluminium diethylphosphinate and melamine polyphosphate, and, organically modified montmorillonite nanoclay was investigated. TGA, DSC, TGA-FTIR and FTIR-ATR were applied to assess the condensed phase action of the flame retardants. A mechanism for the decomposition of polycaprolactam and its interaction with the flame retardants is deduced. The outcome of this study implies that combining both flame retardants results in an enhanced effect when compared with their application on a separate basis.
Keywords: Polycaprolactam; Aluminium diethylphosphinate; Melamine polyphosphate; Natural montmorillonite;

A novel oligomeric charring agent (PTCA) containing triazine and diphenyl group was synthesized by cyanuric trichloride, diphenylamine and ethylenediamine through nucleophilic reaction. The structure and thermal stability of PTCA were characterized by Fourier transform infrared spectrometry (FT-IR), element analysis testing and thermogravimetric analysis (TGA). The effectiveness of the novel intumescent flame retardant system (ammonium polyphosphate and PTCA, abbrev. IFRs) on fire retardancy and thermal stability of polypropylene (PP) was investigated through UL-94, limiting oxygen index (LOI) tests, cone calorimeter tests and thermogravimetric analysis (TGA). UL-94 vertical burning test revealed that the addition of 20 wt% IFRs into neat PP was enough to reach V-0 rating. LOI value of PP by addition of 20 wt% IFRs rose from 17.5 to 31 vol%. Moreover, a remarkable decrease in peak heat release rate (PHRR: −90%), total heat release (THR: −54%) and total smoke release (TSR: −51%) was revealed when the loading of IFRs was 20 wt%. TGA results showed that PTCA presented good char formation ability, and it would greatly increase the thermal stability of PP when combined with APP. The Fourier transformed infrared spectra (FTIR) revealed that the flame retardant mechanism might be ascribed to aromatic and phosphoric char formed during combustion. Additionally, the structure and morphology of char residues were further studied by SEM and Raman spectra.
Keywords: Polypropylene; Triazine; Charring agent; Intumescent flame retardant; Cone calorimeter;

High impact polystyrene (HIPS) based composite filled by magnesium hydroxide (MH) and microencapsulated red phosphorus (MRP) with a gradient dispersion of the flame retardant was successfully prepared through layer-on-layer laminating. The gradient variations of structure and composition of the flame retardant along the thickness direction of the composite were characterized by scanning electron microscopy and energy dispersive spectroscopy. Fire performance of the gradient composite was determined by cone calorimeter test. It has been shown that the flame retardant displays a symmetric gradient dispersion along the thickness direction of the HIPS/MH/MRP composite. Thermo-oxidative degradation of the HIPS/MH/MRP gradient composite is retarded notably. This gradient composite can not only produce more charred residue upon thermal degradation, the residue is also more continuous and compact than its homogeneous counterpart with the same loadings of flame retardant. The time to ignition of the gradient composite is prolonged and the times to peak heat release rate, peak mass loss rate, peak smoke production rate and peak CO yield of the gradient composite are all delayed remarkably. Overall, the gradient composite exhibits significantly improved thermal stability, flame retardancy, smoke suppression and decreased toxic release in comparison with its homogeneous counterpart.
Keywords: High impact polystyrene; Thermal stability; Flame retardancy; Gradient structure;

Full scale nanocomposites: Clay in fire retardant and polymer by Deqi Yi; Rongjie Yang; Charles A. Wilkie (31-41).
Full scale nanocomposites of polypropylene and ethylene-co-vinyl acetate with ammonium polyphosphate/MMT nanocompound composites were prepared by melt blending. Their morphologies are assessed by X-ray diffraction and thermal stability and flammability were characterized by thermogravimetric analysis and cone calorimetry. PP full scale nanocomposites show enhanced flame retardancy compared to other PP composites because the clay can control the viscosity during char formation, maintain the layered structure of the clay and function as a barrier. The EVA full scale nanocomposites also show good fire retardancy with a nanoplatelet char.
Keywords: Nanocomposites; Ammonium polyphosphate; Polypropylene; EVA;

Study on inhibition mechanisms of light-induced wood radicals by Acacia confusa heartwood extracts by Tzu-Cheng Chang; Huan-You Lin; Sheng-Yang Wang; Shang-Tzen Chang (42-47).
The aim of this study was to investigate the inhibition mechanisms of light-induced wood radicals by Acacia confusa heartwood extracts (AcE). Wood radical scavenging analysis was determined by ESR spectroscopy. The results obtained demonstrated that wood radicals could be inhibited through UV absorption of AcE. According to results of AcE photooxidation derivative analyses detected by HPLC–DAD, HPLC–MS/MS and FTIR spectroscopy, o-quinones, peroxides and other oxidation derivatives were yielded from flavonols (such as melanoxetin and transilitin) in AcE; okanin (chalcone) might be formed from 7,8,3′,4′-tetrahydroxyflavanone (flavanone); 7,8,3′,4′-tetrahydroxyflavone and 7,3′,4′-trihydroxyflavone (flavones) would transform to flavanone. On the basis of GPC analysis results, proanthocyanidins and derivatives of higher molecular weight might be polymerized from melacacidin (flavan-3,4-diol). Taken together, these results clearly demonstrated that A. confusa heartwood extract can absorb UV light and form photooxidation derivatives. Accordingly, wood radicals induced by UV light were inhibited and consequently wood photodegradation was retarded.
Keywords: Acacia confusa; Extract; Photodegradation; Radical; Wood;

Alkyd artists' paints: Do pigments affect the stability of the resin? A TG and DSC study on fast-drying oil colours by C. Duce; L. Bernazzani; E. Bramanti; A. Spepi; M.P. Colombini; M.R. Tiné (48-58).
We studied ten alkyd artists' paints from the Griffin Alkyd, “fast drying oil colours” series (Winsor & Newton) in order to evaluate the effect of pigment–binder interactions on the stability of the alkyd resin. The literature on alkyd paints has focused above all on the characterization of the paints and their ageing processes using various techniques, however, to the best of our knowledge, research on pigment-resin interaction is still lacking.We selected four alkyd colours (red, blue, yellow and green) in two formulations based on inorganic or organic pigments together with titanium white and black formulated with carbonized bones and we applied a combined differential scanning calorimetric (DSC) and thermogravimetric (TG) approach. The pure pigments and the whole paint replicas were analyzed, and the effect of natural ageing on the paints was monitored for eight months. Artificial ageing in an acetic acid atmosphere was also studied.We found that organic and metallorganic pigments interacted the strongest with the alkyd resin, while the inorganic pigments appear to act more as dispersants. The chemical drying of the paint on the other hand, via auto-oxidation, is almost independent of the pigment and only depends on the alkyd content. The paint is fully dried after eight months. Paint samples from two hyper-realistic artworks, “Salto di qualità”, 2003, and “Senza nome”, 2007, by the Italian painter Patrizia Zara were investigated by DSC in order to evaluate the effects of several years of natural ageing on alkyd fast-drying oil colours. At the end of chemical drying, the alkyd colours seemed very stable. Artificial acid ageing visibly damaged the paint replicas, but appeared to act mostly on the pigment rather than on the resin network.
Keywords: Alkyd paints; Pigments; Natural ageing; Acetic acid artificial ageing; TG; DSC;

Thermal and in vitro degradation properties of the NH2-containing PHBV films by Yu Ke; Zhengxiang Qu; Gang Wu; Yingjun Wang (59-67).
Solution-cast poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films were photographed with polyacrylamide that was further partially transformed into amine groups through Hofmann degradation. The resulting NH2-containing PHBV films were incubated in phosphate-buffered saline for up to 360 days to study the abiotic degradability of the films with different polyacrylamide grafting percentage and the effect of the grafting percentage or hydrolysis on the thermal degradation of PHBV. The 360-day static degradation results showed that the maximum weight loss of PHBV reached to 2.50% at 300 days incubation. The value of the NH2-containing PHBV films was much greater than that of PHBV and increased with the polyacrylamide grafting percentage. All thermal degradation temperatures of the NH2-containing PHBV films decreased with the polyacrylamide grafting percentage before or after in vitro degradation. At 360-day incubation, the temperature at the maximum thermal-degradation rate of PHBV films decreased and those of the NH2-containing PHBV films increased compared with the samples without in vitro degradation. Thermal degradation model of PHBV and the NH2-containing PHBV films followed Avrami-Erofeev with index of 0.4 and Mampel Power with index of 2 before in vitro degradation, respectively. However, only Mampel Power with index of 2 was found to be the most frequently used mechanism to represent the thermal decomposition of PHBV in all films after in vitro degradation.
Keywords: PHBV; Modification; Degradation; Thermal degradation;

A simulation approach to study photo-degradation processes of polymeric coatings by Hesam Makki; Koen N.S. Adema; Elias A.J.F. Peters; Jozua Laven; Leendert G.J. van der Ven; Rolf A.T.M. van Benthem; Gijsbertus de With (68-79).
Chemical degradation of polymer coatings via a photo-oxidative pathway, denoted as photo-degradation, results in physical changes which, in spite of the long service life of coatings, eventually lead to failure of the material. Conventional molecular simulations cannot cope with this process with its wide range of time and length scales, related to the rare occurrence of ‘degradation events’ as compared to the time scale of structural relaxation of the polymer chains. Therefore a combination of suitable simulation techniques is needed to overcome this problem. By coupling a kinetic Monte Carlo simulation to a Dissipative Particle Dynamics method, a novel simulation approach has been developed that makes it possible to take into account chemical and physical pathways of the photo-degradation process. For a model polyester-urethane coating photo-degradation under inert conditions was studied with and without taking structural relaxation into account as well as by varying the ratio of reaction rate constants. For the model coating studied, taking physical relaxation into account proved to be essential for modeling the photo-degradation process.
Keywords: Photo-degradation; Polyester-urethane; Monte Carlo simulation; Dissipative Particle Dynamics;

Polyacrylonitrile (PAN) nanofibers were produced by electrospinning, then heated to crosslink and stabilize their morphology. The properties of resultant nanofibers were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and solvent extraction. The FTIR spectra of heated PAN revealed three simultaneous reactions within nanofibers: dehydrogenation, cyclization, and carbonylation. Their stabilization kinetics was different from the microfibers. The gel fraction results of extraction in DMF indicated the crosslinking degree resulted from the heat treatment. The SEM observation confirmed the integrity of nanofibers after alkaline hydrolysis. These finely modified PAN nanofibers have potential applications such as superabsorbent and artificial muscles.
Keywords: Polyacrylonitrile; Nanofibers; Electrospinning; Heat stabilization; Alkaline hydrolysis; FTIR;

Different flame retardancy effects and mechanisms of aluminium phosphinate in PPO, TPU and PP by Hongxia Li; Nanying Ning; Liqun Zhang; Yanxiang Wang; Wenli Liang; Ming Tian (86-95).
The effects of aluminium phosphinate (AlPi) on the flame retardancy of three different polymers, namely, poly(2, 6-dimethyl-1, 4-phenylene oxide) (PPO), thermoplastic polyurethane (TPU) and polypropylene (PP), were investigated through cone calorimeter tests (CONE), vertical burning tests (UL-94), limiting oxygen index (LOI), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) observation. The results showed that the amounts of AlPi needed to reach V-0 UL-94 rating in the PPO, TPU and PP matrices were 0 wt%, 30 wt% and 50 wt%, respectively. Moreover, the addition of AlPi significantly increased the LOI values of PPO and PP, but had almost no effect on that of TPU. With the addition of AlPi, the peak of heat release rate (PHRR) of PPO and TPU decreased whereas that of PP increased. The total heat evolved (THE) of all polymers decreased by adding AlPi into the polymers. With the addition of AlPi, PPO composite formed a dense char layer and showed the best flame retardancy, TPU composite formed a thinner char layer and PP composite did not form char layer during combustion.Based on the thermal degradation behaviour and the char residue of these composites, the flame retardancy mechanisms of the three systems were discussed. For AlPi/PPO composites, the flame retardancy mechanism was condensed phase charring mechanism because of the formation of continuous char layer during combustion. For AlPi/TPU composites, AlPi acted mainly in gas phase, and a synergistic reaction of phosphorus and nitrogen compounds occurred and diethylphosphic acid providing flame inhibition was released during the burning process. As a result, the addition of AlPi successfully reduced the melt-dripping and enhanced flame retardancy of TPU matrix. For AlPi/PP composites, AlPi acted as a flame inhibitor in gas phase, decreasing the effective heat of combustion of the volatiles (THE/TML) and increasing the amount of CO.
Keywords: Poly(2, 6-dimethyl-1, 4-phenylene oxide) (PPO); Thermoplastic polyurethane (TPU); Polypropylene (PP); Flame retardancy; Aluminium phosphinate; Fire behaviour;

Biodegradable aliphatic copolyesters containing PEG-like sequences for sustainable food packaging applications by Matteo Gigli; Nadia Lotti; Massimo Gazzano; Valentina Siracusa; Lara Finelli; Andrea Munari; Marco Dalla Rosa (96-106).
A series of novel random copolymers of poly(butylene 1,4-cyclohexanedicarboxylate) (PBCE) containing triethylene glycol sub-unit (P(BCEmTECEn)) were synthesized and characterized in terms of molecular and solid-state properties, among these barrier properties to different gases (oxygen and carbon dioxide). In addition, biodegradability studies both in soil and in compost and ecotoxicological analysis, by means of the Lepidium sativum test, have been conducted.The copolymers displayed a high and similar thermal stability with respect to PBCE. At room temperature, all the copolymers appeared as semicrystalline materials: the main effect of copolymerization was a lowering of crystallinity degree (χ c) and a decrease of the melting temperature compared to the parent homopolymer. The Baur's equation well described the T m-composition data. Final properties and biodegradation rate of the materials under study were strictly dependent on copolymer composition and χ c. As a matter of fact, hydrophilicity regularly increased with the increasing of TECE mol%, due to the PEG-like portion. The elastic modulus and the elongation to break decreased and increased, respectively, as TECE unit content was increased. As to the barrier properties, the selectivity ratios for the examined samples increased with the increasing of TECE mol%, confirming the correlation between the permeability and the chemical composition. The copolymers with lower TECE unit content (up to 30 mol%) showed improved barrier properties with respect to polylactide films tested under the same conditions.Lastly, the biodegradation rate of P(BCEmTECEn) copolymers increased with the increasing of TECE mol%, while PBCE remained almost undegraded in the explored conditions.
Keywords: Poly(butylene 1,4-cyclohexanedicarboxylate); Triethylene glycol; Random copolymers; Solid-state properties; Polymer gas permeability;

This study evaluated new experimental parameters and end-point criteria for determining the thermal endurance of fibreglass-reinforced epoxy laminates via thermal analysis. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) were used in these experiments. The composite was exposed to temperatures ranging from 170 to 200 °C for times ranging from 10 to 480 h in accord with IEC 60216. The maximum heat flow temperature (DSC T max) for the first thermo-oxidative reaction, the maximum weight loss temperature (DTGA T max), and the maximum decomposition rate were investigated. The change in the glass transition temperature after the thermal ageing was also determined using DMA. The structural changes in the samples were examined via Fourier transform infrared spectroscopy and microscopic analysis. Oxidative degradation at the surface accompanied by pyrolytic degradation in the bulk of the sample was observed. The end-point criteria were derived for all applied methods based on the time required for the composite structure to delaminate considerably. The obtained data were used to construct Arrhenius diagrams, and cross-correlation was sought among all experimental parameters. These measurements demonstrated that the DTGA T max, DMA T g, and DSC T max characterizes the ageing process sufficiently well within the applied temperature interval and satisfy the IEC 60216 requirements.
Keywords: Thermal endurance; Epoxy laminate; PCB FR4; Thermal analyses; DSC; TGA;

Polymer degradation during continuous ink-jet printing by Joseph S.R. Wheeler; Stuart W. Reynolds; Steven Lancaster; Veronica Sanchez Romanguera; Stephen G. Yeates (116-121).
Results are reported for the first time on the possibility and cause of polymer degradation in a full commercial inkjet printer. The behaviour of three linear poly(methyl methacrylate) (PMMA) samples, having M w 90, 310 and 468 kDa respectively, in a continuous inkjet (CIJ) Domino A-Series+ printer is investigated and compared with earlier reported results for two experimental drop on demand (DOD) printers, a Dimatix DMP-2800 and a Microfab single nozzle glass capillary. Despite all three printheads having equivalent strain rate at the nozzle tip (ε) no degradation is observed within the CIJ head alone whereas single pass degradation is observed in both DOD printheads. This can be attributed to a consequence of a number of factors including the slightly greater nozzle diameter, and different nozzle geometry, which includes cone angle and nozzle cylinder length, for CIJ, the different mode of drop generation or the higher polymer concentration investigated. It should also be noted that the flow through the CIJ nozzle is continuous, where it is pulsed in the case of DOD. The calculated maximum strain rates are similar, but in DOD it is being periodically ramped up and switched off.The main source of polymer degradation in CIJ printing through a CIJ Domino A-Series+ printer is found to be the continuous recycling of ink through the pump resulting in mechano-chemical polymer degradation. Molecular weight degradation proceeds by random scission, and is obtained at the lower shear rates experience as a consequence of the longer residence time due to mechano-chemical damage in the pump. These results have significance in the total design of inkjet systems for the delivery of high molecular weight polymers and materials sensitive to mechano-chemical degradation and highlight the need for careful consideration when moving from laboratory based print tools to full scale application.
Keywords: Ink-jet printing; Polymer degradation; Extensional flow; Poly(methyl methacrylate);

Attenuated total reflection Fourier transform infrared (ATR-FTIR) and two dimensional correlation (2D-COS) spectroscopies were used to follow the structural alteration occurring upon ion irradiation (H+ and He2+) of films of poly (ether ether ketone), PEEK. Samples were exposed to ion irradiation doses up to 75 MGy in air atmosphere, and IR spectra were measured after ion irradiation and also for the gels after solvent extraction experiments. With the help of high resolution and high sensitivity 2D COS it was possible to obtain useful information about the different effects, types and mechanisms of reactions accompanying ion irradiation. Three main different effects of ion irradiation were observed. Oxidation manifested itself by the production of new carbonyl species absorbing in the IR at 1715 and 1745 cm−1 that were mainly present in the irradiated samples and attributed to fluorenone structures and to ester groups. Crosslinking occurred with the progressive development of new aromatic species absorbing at 1470, 870 and 810 cm−1 that were mainly present in the gels formed on irradiation. The formation of intermolecular crosslinks resulted in the increase in local ordering within the amorphous phase and orientation was observed to increase after ion irradiation by the progressive development of new bands at 1316, 1288, and 1240 cm−1.The different structures produced on irradiation with proton and helium ions were discussed and the analysis showed that helium ions were more effective in introducing the observed changes than protons. The infrared spectroscopy combined with 2D correlation provides a fast and powerful tool for polymer structure characterization.
Keywords: Poly (ether ether ketone); Irradiation; Two dimensional FTIR correlation spectroscopy; Degradation; Crosslinking;

The storage stability of polyvinylbutyral solutions from an electrospinnability standpoint by Petra Peer; Martin Stenicka; Vladimir Pavlinek; Petr Filip (134-139).
The quality of electrospun fibres is subject to many factors ranging from the characteristics of the materials used to processing conditions. Although an important parameter for applicability, less attention has been paid to the storage stability of applied polymer solutions and its impact on the quality of electrospun webs. The aim of this study is to analyse the storage stability of polyvinylbutyral solutions in methanol and ethanol for the formation of undisturbed nanofibres. The quality of nanofibrous mats produced over a period of 197 days, during which the solutions were stored under constant conditions, was investigated. Using rheological measurements, SEM, FTIR, and DSC techniques, it was shown that the storage period for the solutions used had almost no influence on the quality of electrospun fibres, which is a positive result for practical use.
Keywords: Electrospinning; Nanofibres; Polyvinylbutyral; Ageing; Stability;

Considering environment protection and economic requirements, the reuse of glass fiber reinforced flame retardant PBT (GFFRPBT) is of significant importance. In this paper, the properties of reprocessed GFFRPBT (RGFFRPBT) including rheological, mechanical, thermal and flame retardant properties were evaluated. To explore the relationship between structure and properties of RGFFRPBT, the carboxyl content and intrinsic viscosity of PBT, average length of glass fiber and its distribution, and the microscopic appearance of RGFFRPBT were investigated. The results demonstrated that when GFFRPBT was injection molded for five cycles, the intrinsic viscosity of PBT, average length of the glass fiber and the percentage of glass fiber length, which was higher than critical length decreased, whereas, the carboxyl content of PBT increased significantly. The rheological and mechanical properties became sensitive to these variations: the shear viscosity, impact strength, tensile and flexural strength of RGFFRPBT decreased. Furthermore, the influence of degradation on the PBT molecular weight and the glass fiber length after the reprocessing cycles were negative on the thermal properties of RGFFRPBT. However, the flame retardant properties of RGFFRPBT was independent on the degradation; RGFFRPBT with five injection molding cycles could achieve a UL-94 V-0 classification 32.0 LOI, and pass the GWIT (775 °C) test. The results showed that, when GFFRPBT was reprocessed twice, its properties matched the requirements of electronic and electric fields well.
Keywords: Glass fiber reinforced flame retardant PBT; Reprocessed; Intrinsic viscosity; Average length of glass fiber; Properties;

Effects of microencapsulated APP-II on the microstructure and flame retardancy of PP/APP–II/PER composites by Lin Yang; Wenlong Cheng; Jian Zhou; Huilin Li; Xinlong Wang; Xiaodong Chen; Zhiye Zhang (150-159).
In this study, crystalline form II ammonium polyphosphate (APP-II) was microencapsulated with melamine-formaldehyde (MF) resin, which was prepared by in situ polymerization. The results of Fourier transform infrared spectra (FTIR), thermogravimetry (TG), energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) analyses demonstrated that APP-II was successfully microencapsulated with the MF resin. Polypropylene (PP)/APP-II/pentaerythritol (PER) and PP/MFAPP-II/PER composites were prepared and the flame retardancy, thermal stability, and microstructure of the corresponding composites were investigated based on the limiting oxygen index (LOI), UL-94 testing, TG, EDS, SEM, and cone calorimetry. Compared with PP/APP-II/PER composites, the PP/MFAPP-II/PER composites had a higher LOI value and passed the V-0 rating more easily. The results of the TG, EDS, SEM, and cone calorimetry analyses demonstrate that MFAPP-II is beneficial for forming a compact and strong intumescent char, thereby reducing the rates of the maximum-rate decomposition temperature (T max), heat release rate (HRR), total heat release rate (THR), and mass loss (ML) for the PP/MFAPP-II/PER composites, as well as improving the thermal stability, compatibility, and dispersion of MFAPP-II in PP/MFAPP-II/PER composites.
Keywords: Microencapsulation; Ammonium polyphosphate; Polypropylene; Intumescent flame retardant; Melamine-formaldehyde;

The thermal decomposition behavior of the terpolymer of ethylene, propylene, and carbon monoxide (EPCO), stabilized by calcium hydroxyapatite (CHA) as an acid scavenger and 2,2′-oxamidobis-[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (OHP) as a radical scavenger, was investigated in terms of shear, temperature and stabilizer composition. The optimum composition of two stabilizers was affected by shear condition as well as thermal history. The thermal stability at the static state evaluated by DSC indicated that the simultaneous use of CHA and OHP produced a synergistic effect and the optimum composition of CHA/OHP ranged from 4/1 to 8/1 by wt at the total content of 0.5 wt%. However, dynamic rheological analysis revealed that shearing changed the optimum composition of the stabilizers to 7/1 by wt but had little effect on the total stabilizer content. In addition, the synergistic effect was not observed at the particular composition of 1/4 by wt. The increase of melt viscosity of EPCO with time ascertained that the thermal decomposition of EPCO accompanied crosslinking through the intermolecular aldol condensation reaction.
Keywords: Polyketone; Calcium hydroxyapatite; 2,2′-oxamidobis-[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]; Thermal stability;

In this paper, the flame retarding mechanism of novolac as char agent and the phosphorous–nitrogen (P–N) flame retardant system was investigated in thermoplastic poly(ether ester) elastomer(TPEE) composites containing aluminum diethylphosphinic (AlPi) and melamine polyphosphate (MPP). The fire resistance of TPEE containing P–N flame retardant and novolac was analyzed by the limiting oxygen index (LOI) and the vertical burning (UL94) test. The result shows that the flame retardants containing P–N increased the LOI of the material from 17.3 to 27%. TPEE containing P–N flame retardants just got UL94 V-2 ranking, which resulted in the flaming dripping phenomenon. On the other hand, TPEE containing P–N flame retardant and novolac achieved UL94 V-0 rating. The mechanism of thermal decomposition and char formation was studied by thermal gravimetric analysis (TGA), temperature-dependent FTIR and Pyrolysis/GC/MS. TGA and SEM-EDX measurements have demonstrated that novolac results in the increase of char yield and the formation of the thermally stable carbonaceous char. The results of FTIR and Pyrolysis/GC/MS analyses indicated that cross-linking reaction between the novolac and P–N flame retardant and polyaromatisation of the novolac itself which resulted in a strong compact carbonaceous char. Therefore, novolac is a promising synergist for the P–N flame retardant in TPEE.
Keywords: Halogen-free flame retarding; Thermoplastic poly(ether ester) elastomer (TPEE); Novolac; Flame retarding mechanism;

A series of novel ureido organic stabilizers for poly(vinyl chloride) (PVC) with different length of alkyl chains, including N,N'-bis(phenylcarbamoyl)ethylenediamine (NA2), N,N'-bis(phenylcarbamoyl)butylenediamine (NA4) and N,N'-bis(phenylcar- bamoyl)hexamethylenediamine (NA6) were designed and synthesized, which have greater stabilizing efficiency compared with Ca/Zn stabilizers and phenylurea at the same concentration in PVC mixtures. The results of Congo red test, discoloration test, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectra showed that the ureido moieties of NAn (n = 2, 4, 6) have stronger ability to replace the labile chlorine atoms in PVC chains, but weaker ability to absorb hydrogen chloride (HCl) than those in phenylurea. On the other hand, longer alkyl chains in the synthesized organic stabilizers had positive effect in stabilizing efficiency for PVC, which was proved by the results that NA6 was the most efficient stabilizer among the present study, followed by NA4 and NA2. Furthermore, mixing the model compound NA6 with zinc stearate in different mass ratios led to a true synergistic effect, the “zinc burning” of PVC products was remarkably postponed.
Keywords: Poly(vinyl chloride); N,N'-Bis(phenylcarbamoyl)alkyldiamines; Organic thermal stabilizer; Stabilization mechanism; Synergistic effect;

Degradation markers of fibroin in silk through infrared spectroscopy by M.A. Koperska; D. Pawcenis; J. Bagniuk; M.M. Zaitz; M. Missori; T. Łojewski; J. Łojewska (185-196).
Infrared spectroscopy (FTIR) is a commonly available tool in laboratories dealing with both degradation of materials and conservation of art objects to evaluate their condition. In this paper FTIR was engaged to study degradation of fibroin included in silk samples (Bombyx mori) artificially aged at various conditions (oxygen, water vapor and volatile organic products) at temperature of 150 °C. The results collected by Attenuated Total Reflectance/Fourier Transform Infrared Spectroscopy (ATR/FTIR) were validated by UV/Vis, XRD and SEC analyses. Based on the results, the degradation estimators were verified and classified as: (1) crystallinity defined as ratio of absorbance at 1620 and at 1656 cm−1, A 1620 /A 1656 [1], or at 1620 and 1699 cm−1, A 1620 /A 1699 [2]; or ratio of areas under fitted curves of band at 1261 and 1230 cm−1, P 1261 /P 1230 [3], (2) oxidation – A 1620 /A 1514 and (3) depolymerization – P 1318 /P 1442 . Degradation gauges defined in such a way indicate that upon artificial aging water vapor and oxygen has the most profound impact on the progress of silk degradation. It also indicates that oxygen-lean conditions stabilize silk at elevated temperature.
Keywords: Fibroin; ATR–FTIR spectroscopy; UV/Vis spectroscopy; XRD; SEC; Degradation estimators;

Stabilization of highly crosslinked ultra high molecular weight polyethylene with natural polyphenols by Jie Shen; Luigi Costa; Yuhao Xu; Yang Cong; Yajun Cheng; Xincai Liu; Jun Fu (197-205).
In the present work, dodecyl gallate (DG) and gallic acid (GA) were blended with UHMWPE and consolidated by compression moulding prior to e-beam irradiation. Stabilisation of highly crosslinked UHMWPE with these polyphenols was examined by tracing post-irradiation oxidation kinetics of UHMWPE at room temperature with Fourier transform infrared (FTIR) spectroscopy, in comparison to highly crosslinked vitamin E (VE)-blended and virgin UHMWPE. Phenol loss upon e-beam irradiation depended on the polyphenol chemistry and compatibility with the polyethylene matrix: the oleophilic DG and VE showed higher phenol loss than GA. Nevertheless, all the antioxidant-containing materials exhibit improved oxidation stability compared to virgin material. The formation kinetics of ketones, hydroperoxides, carboxylic acids, esters, and ketoacids were analysed in detail over time in order to understand the effect of polyphenols on the oxidation mechanism of highly crosslinked UHMWPE. Our results suggest that these polyphenols show limited phenol loss and are protective for highly crosslinked UHMWPE, which may be promising alternative for UHMWPE biomaterials with improved stability.
Keywords: UHMWPE; Oxidation; Polyphenols; Ageing; FTIR; Crosslinking;

We investigate the influence of TiO2 in the anatase (ATiO2) form on the chemical and mechanical properties of clear wood coatings based on a high T g/low T g multiphase acrylic binder dispersion. The photooxidation rates were compared using ATR-FTIR techniques and tension tests. The partial least square regression (PLS-R) used showed to be a suitable method to monitor the chemical changes of the polymeric binder and to investigate the influence of the photocatalyst on the photooxidation behaviour. The results obtained by comparing the relative photooxidation rates of the coating systems with and without ATiO2 showed that ATiO2 led to higher photooxidation rates, especially at the beginning of the exposure cycle. Tension tests proved that samples containing ATiO2 are characterized by a significant change of the elastic behaviour at the initial phase of the Xenon arc exposure. After 150 h of Xenon arc exposure, the change of the Young's modulus, which can be attributed mostly to the high T g component of the multiphase binder, increased at a higher rate. We conclude that the photooxidation of the acrylic binder was strongly accelerated by ATiO2, whereas the effect of increasing concentration of ATiO2 is limited.
Keywords: Wood coatings; Self-cleaning surfaces; TiO2; Anatase;

Undoped, cast films of PolyBenzoImadazole (PBI) were investigated as a function of humidity using both H2O and D2O, and as a function of temperature up to 100 °C in order to better understand the infrared response of this polymer, as well as to provide benchmark data for subsequent studies on acid doped PBI. Marked changes across the mid-IR range were observed during the uptake of water and D2O. The use of D2O proved extremely useful in terms of deconvoluting the complex IR response observed and allowed the IR data to be rationalised in terms of the disruption of the N–H … N inter-chain hydrogen bonded network and changes in the morphology of the polymer.
Keywords: Infrared; Spectroscopy; PBI; Hydrogen; Bonding;

Aging life prediction system of polymer outdoors constructed by ANN. 1. Lifetime prediction for polycarbonate by Han Liu; Mingyong Zhou; Yuli Zhou; Shan Wang; Guangxian Li; Long Jiang; Yi Dan (218-236).
By the application of artificial neural network (ANN), the concept of constructing polymers' aging life prediction system has been proposed for the first time in the present work. Such a system can be designed via integrating several independent ANN modules playing different roles: the S module for calculating environmental stress level, the F module for outputting the feature of aging life distribution, the S a module for computing the accelerated environmental stress level, the a T module for studying the correspondence between life distribution of certain accelerated and natural aging tests, and the structure module for converting polymer structures into structure parameter matrix. Here polycarbonate, as a widely used engineering thermoplastic with complex aging behavior and various aging mechanisms, has been researched to constructing its aging life model with the help of the systematic ANN method above, which well reflects huge potential of ANN's application in the field of polymers' aging life prediction for practical application.
Keywords: Aging life prediction; Natural aging; Accelerated aging; Artificial neural network (ANN); Polycarbonate;

Seawater accelerated ageing of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Morgan Deroiné; Antoine Le Duigou; Yves-Marie Corre; Pierre-Yves Le Gac; Peter Davies; Guy César; Stéphane Bruzaud (237-247).
The aim of this study is to establish a baseline for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) lifetime prediction in a marine environment, by means of mechanical and physico-chemical characterization of specimens immersed in continuously renewed and filtered natural seawater in the laboratory at different temperatures (4, 25 and 40 °C). Samples were also aged at sea in Lorient harbour in order to compare laboratory and natural degradation mechanisms and kinetics. Due to its morphology, hydrolysis of PHBV in natural seawater is quite slow, and samples were observed to undergo preferentially an enzymatic surface degradation. Increasing the aging temperature in the laboratory promotes the water uptake and causes hydrolysis. As two degradation mechanisms occur in parallel, the choice of test conditions is critical, and the lifetime of PHBV in a marine environment is difficult to predict accurately.
Keywords: Poly(3-hydroxybutyrate-co-3-hydroxyvalerate); Accelerated ageing; Hydrothermal degradation; Seawater;

Comparative study on the flame retarded efficiency of melamine phosphate, melamine phosphite and melamine hypophosphite on poly(butylene succinate) composites by Hongyu Yang; Lei Song; Qilong Tai; Xin Wang; Bin Yu; Yao Yuan; Yuan Hu; Richard K.K. Yuen (248-256).
The main aim of this work was to investigate the flame retarded efficiency of melamine phosphate (MP), melamine phosphite (MPi) and melamine hypophosphite (MHP) on poly(butylene succinate) (PBS) composites. The flame retardant, thermal degradation and combustion properties of PBS composites were characterized by limiting oxygen index (LOI) test, vertical burning (UL-94) test, thermogravimetric analysis (TGA) and cone calorimeter (Cone), respectively. The LOI results showed that the LOI values followed the sequence of PBS/MP < PBS/MHP < PBS/MPi at the same additive loadings. TGA results indicated that the initial decomposition temperature of PBS composites decreased with the decrease of phosphorus valence state and the incorporation of all three compounds could promote the char formation. Adding these three compounds into PBS matrix can decrease the peak heat release rate (PHRR) obviously from cone calorimeter results. Scanning electron microscopy (SEM) was employed to characterize the morphology and structure of the char residues. The flame-retardant mechanism in gaseous phase and condensed phase were investigated by thermogravimetric analysis/infrared spectrometry (TG-IR) and in situ Fourier transform infrared spectroscopy (in situ FTIR), respectively, and the possible flame-retardant mechanism was proposed.
Keywords: Phosphorus-containing melamine salts; Phosphorus valency; Poly(butylene succinate); Flame retarded efficiency; Flame-retardant mechanism;

Interactions with volatile organic compounds (VOCs) are one of the main issues within the field of the preventive conservation of artworks. VOCs deriving from wooden frames and museum furniture consist in several aldehydes, formic acid and a high abundance of acetic acid. The aim of this study was to evaluate the interactions between alkyd paints and acetic acid that take place during the curing process of the paint layers. A set of reference Winsor & Newton alkyd paint layers was exposed to acetic acid vapour for six months to model these interactions. In order to evaluate the main degradation pathways occurring during the artificial ageing, a multi-analytical approach based on chromatographic and spectroscopic techniques was used. The results describe the main degradation processes of the organic and inorganic components used in the production of the alkyd resin paint.
Keywords: Alkyd paints; Phthalic acid loss; VOCs; GC/MS; HPLC–MS; ATR-FTIR;

A series of flame retardant acrylonitrile-butadiene-styrene copolymer (FR ABS) composites were prepared by melt blending using aluminum hypophosphite (AHP) and melamine cyanurate (MCA) or silicone flame retardant (SiFR) as synergistic flame retardant. The thermal behavior, flame retardancy of FR ABS composites were investigated by thermogravimetric (TGA), the UL-94 vertical burning test, limiting oxygen index (LOI) and cone calorimeter test. The FR ABS composite showed good flame retardancy, from no vertical rating of ABS to V-0 rating of FR ABS containing 25 wt% AHP in the UL-94 test. The results showed that ABS/22wt%AHP composites presented lower peak heat release rate (PHRR), lower total heat release (THR) and higher char residue (CR) than those for ABS. Adding small amount of MCA or SiFR, PHRR and THR values for ABS/20wt%AHP/2wt%MCA and ABS/20wt%AHP/2wt% SiFR composites decreased compared with ABS/22wt%AHP composite, which indicated that the incorporation of MCA or SiFR led to a synergistic effect on the ABS/AHP flame retardant composites. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) measurement results showed that the residual structure for ABS/20wt%AHP/2wt%MCA and ABS/20wt%AHP/2wt%SiFR composites presented very different surface morphology and surface element composition, which were attributed to different synergistic flame retardant mechanisms.
Keywords: ABS; Flame retardancy; Aluminum hypophosphite; Synergistic agent; Flame retardant mechanisms;