Fourier transform infrared micro spectroscopy mapping studies of weathered PVC capstock type formulations. II: Outdoor weathering in pennsylvania

FTIR micro spectroscopy coupled with mapping techniques is a powerful methodology to evaluate dimensionally dependent changes such as those encountered in PVC weathering processes. It is based on the complexity and specificity of the infrared spctrum and the dimensional resolution of the microscope. This paper will outline a systematic FTIR study of changes observed during outdoor photo degradation of PVC siding capstock formulations, as a function of exposure time and TiO₂ level. The results are compared with previously obtained accelerated QUV data. Profiles through the thickness dimension were analyzed to identify degradation species and depth distribution.     

Structural changes and mechanical performance of recycled poly(vinyl chloride) bottles exposed to ultraviolet light at 313 nm

The structural changes and mechanical performance of virgin poly(vinyl chloride) (PVC) bottle (VB) compounds blended with postconsumer PVC bottles collected from a specified factory (RB‐F) and houses (RB‐H), were examined before and after UV irradiation at 313‐nm UV wavelength for different periods of time up to 28 days. The results indicated that, when exposed to UV light, the RB‐F/VB blends containing greater conjugated double bonds with higher yellowness index appeared to exhibit better mechanical performance than that of the RB‐H/VB blends. It was found that the amount of conjugated double bonds was not a linear function of the discoloration level of PVC compounds. Tensile strength of the VB compounds was not affected when incorporated with RB‐F recyclate, but progressively decreased with increasing RB‐H recyclate. An optimum concentration for RB recyclates to be added into the virgin compound was recommended for obtaining a maximum impact strength. Both tensile and impact strengths decreased with increasing UV exposure time, a severe degradation being obvious after a UV exposure time of 21 days. Hardness was not affected significantly by the addition of PVC recyclate, but increased with increasing UV exposure time. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 84–94, 2004     

Polyhedral oligomeric silsesquioxane as a novel plasticizer for poly(vinyl chloride)

This study focuses on investigating the use of polyhedral oligomeric silsesquioxanes (POSS) to plasticize poly(vinyl chloride) (PVC). Conventional organic plasticizers for PVC, such as dioctyl phthalate (DOP), are somewhat volatile, leading to plasticizer loss and unwanted deterioration of the material properties over time. Previous experimental results indicate that methacryl-POSS, which is much less volatile due to its hybrid organic-inorganic structure, has the ability to plasticize PVC. Methacryl-POSS is miscible in the PVC only up to 15 wt%, thereby limiting its suitability as a plasticizer. However, through the use of ternary compositions it is possible to increase the proportion of methacryl-POSS in PVC substantially. The T_g of appropriately formulated ternary PVC/POSS/DOP compounds can be reduced to near room temperature, and these materials exhibit desirable ductile behavior. Binary (PVC/DOP) and ternary (PVC/POSS/DOP) compounds formulated to the same T_g values showed considerably different mechanical properties. Such findings reveal the possibility of using POSS to engineer the mechanical properties of plasticized PVC.     

MoO3 additives for PVC: A study of the molecular interactions

The detailed molecular interactions occurring during thermal degradation of PVC polymer formulations containing MoO₃ additives are investigated using laser microprobe techniques coupled with mass analysis of the volatile pyrolysis products. Comparison with Sb₂O₃–PVC compounds indicate that the additive effects exhibited by MoO₃ are fundamentally different from those observed for Sb₂O₃. Thermal decomposition of MoO₃–PVC is characterized by (1) catalyzed dehydrochlorination of PVC at a lower temperature and increased rate; (2) marked reduction in evolution of benzene, the major fuel species from PVC; and (3) decreased evolution of volatile hydrocarbon species from the polymer plasticizer component. Vapor-phase interactions involving volatile molybdenum species are found to be unimportant. The experimental data indicate that condensed-phase mechanisms and heterogeneous reactions involving MoO₃(s) control polymer decomposition processes. Molecular level details of these reactions are presented and their implications to polymer flame retardance and smoke suppression discussed.     

The functional role of molybdenum trioxide as a smoke retarder additive in rigid poly(vinyl chloride)

The most effective smoke retarders for poly(vinyl chloride) are compounds of transition metals, such as molybdenum trioxide. MoO₃ when added to a rigid PVC compound shows three general effects. First, smoke formation is reduced dramatically as measured either by the NBS smoke chamber test or Goodrich smoke–char test. Second, volatile aromatic pyrolyzate formation is also reduced dramatically. The “pure” conjugated aromatic compounds (particularly benzene and naphthalene) are reduced more than the “mixed” aliphatic–aromatic compounds (such as toluene). Third, char formation is effectively promoted. Based on results from studying MoO₃ (and other metal-;based additives) in regular, perdeuterated, and syndiotactic PVC, we propose a “reductive coupling” scheme as the dominant mechanism to explain the smoke retarder action. In this mechanism the MoO₃ acts in the condensed phase to promote extensive crosslinking of the PVC polymer chains very early in the thermal degradation process. Specifically, the metal additive forms a redox catalyst system which promotes intermolecular crosslinking of polymer chains to form char, rather than the conventional degradation process which gives rise to aromatics and smoke.     

Nanocomposites of PVC/TiO2 nanorods: Surface tension and mechanical properties before and after UV exposure

In this study, nanocomposites of poly(vinyl chloride) (PVC), using the synthesized titanium dioxide (TiO₂) nanorods and commercial nanopowder of titanium dioxide (Degussa P25) were produced by melt blending. The presence of TiO₂ nanorods in PVC matrix led to an improvement in mechanical properties of PVC nanocomposites in comparison with unfilled PVC. The photocatalytic degradation behavior of PVC nanocomposites were investigated by measuring their structural change evaluations, surface tension, and mechanical properties before and after UV exposure for 500 h. It was found that mechanical and physical properties of PVC nanocomposites are not reduced significantly after UV exposure in the presence of TiO₂ nanorods in comparison with the presence of TiO₂ nanoparticles, which can be due to the amorphous structure of the synthesized nanorods. Therefore, it can be concluded that TiO₂ nanorods led to an improvement in photostability and mechanical properties of PVC nanocomposites. The interfacial adhesion between TiO₂ nanorods and PVC matrix was also investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Laser-induced decomposition of PVC

A laser probe–molecular beam experimental technique devised to investigate the dynamic characteristics of polymer decomposition processes is described. Results are presented from application of the technique to the laser vaporization of pure poly(vinyl chloride) (PVC). Vaporization products are sampled directly from the source cell using modulated molecular beam mass spectrometry. Only signals arising from the PVC species in the molecular beam appear in the modulated mass spectra; background species from the residual gas are automatically rejected. Time-resolved spectra provide information on the relative evolution characteristics of the PVC decomposition products. Hydrogen chloride, benzene, and toluene are found to evolve concurrently from the irradiated PVC sample. PVC monomer species are not detected in the laser-vaporized products. The presence of loosely bound water in the sample is distinguished from the evolution of volatile decomposition products by its burst-like release mode. The effect of plasticizer and flame retardant additives on the evolution characteristics of the laser-vaporized species from PVC are also presented.     

UV stabilizers: Their effects on vinyl compounds

Poly(vinyl chloride) (PVC) is the polymer of choice in a wide variety of applications on account of its comparatively low cost, high chemical resistance, good mechanical properties and electrical insulating capabilities. The even wider application of the material has been restricted by its low thermal and photolytic stability. This paper reviews the various light degradation and stabilization mechanisms that have been postulated recently for PVC. The importance of the thermal stabilizer system to the photostabilization of the material is also stressed. Finally the market opportunity for a cost effective UV stabilizer system for rigid PVC is discussed emphasizing the versatility that such a product would give to the vinyl siding manufacturer.     

Some effects of irradiation on properties of filled PVC compounds

Compounds based on poly(vinyl chloride) (PVC), and containing CaCO₃ filler and trifunctional acrylic crosslinking agent have been crosslinked by exposure to γ-rays at dosages to 70 kGy. The crosslinking agent was found to be essential for crosslinking to proceed, only minor sensitivity to the irradiation having been found in compounds omitting the chemical. The presence of filler somewhat inhibits crosslink effectiveness, as measured by solvent uptake data. Elastic moduli and elongations at rupture respond to crosslinking processes, the latter being particularly sensitive to the effects of irradiation. The presence of filler was found to raise modulus, while ductilities of compounds were greater than expected, owing to adhesion at polymer/filler interfaces. Favorable acid/base interaction forces appear responsible for the effect. The reduced sensitivity of filled PVC compounds to γ-ray exposure is attributed to polymer immobilization, the consequence of strong interfacial bonding with the filler.     

Effect of the combination of a benzotriazole‐type ultraviolet absorber with thermal stabilizers on the photodegradation of poly(vinyl chloride)

The effect of the combination of a benzotriazole type of UV absorber (UV326) with different types of thermal stabilizers, including an organic calcium complex and an organotin mercaptide, on the photodegradation of poly(vinyl chloride) (PVC) was investigated by color difference measurements, UV‐vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and viscosity‐average molecular weight (M_η) determinations. Films of PVC containing 0.5 phr of UV326, with or without 2 phr of thermal stabilizer, were prepared by solution casting and subjected to accelerated UV weathering under xenon light with an irradiance of 0.51 W/(m² nm) at 65°C. The results revealed that both UV326 and the mixture of UV326 with the organic calcium complex displayed good performance in inhibiting the photodehydrochlorination and photooxidation of PVC. In contrast, the combination of UV326 and the methyltin mercaptide remarkably accelerated the discoloration of PVC when the irradiation time increased from 300 to 400 h because of the UV sensitivity of the organotin. However, carbonyl index data indicated that a hydrogen abstraction reaction did not take place between UV326 and the methyltin mercaptide, so that the photooxidation of the PVC film was prevented effectively during the whole period of exposure, a result which may be attributed to the strong steric hindrance effect of the tert‐butyl group at the 3‐position of the phenyl ring in UV326. The changes of M_η were in good accordance with the results obtained from other characterizations. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Detailed study of distribution patterns of polycyclic aromatic hydrocarbons and isocyanates under different fire conditions

This study has examined the distribution patterns between gas phase and particle phase of some chemical compounds produced in fires. It has also addressed the question of the distribution of individual particle‐associated species between the different size‐ranges of particles. The chemical compounds studied and discussed in this paper are polycyclic aromatic hydrocarbons (PAHs), and isocyanates. The steady‐state tube furnace, ISO/TS 19700, was chosen as the physical fire model in order to study the production of particles from different types of fire exposure, that is, oxidative pyrolysis, well‐ventilated flaming fires and under‐ventilated flaming post‐flashover fires. Two materials were chosen for investigation, a polyvinyl chloride ( PVC) carpet and a wood board. The particle production from the two materials investigated varied concerning both the amounts produced and the particle size distributions. The analysis of PAHs showed that volatile PAHs were generally dominant. However, when the toxicity of the individual species was taken into account, the relative importance between volatile and particle‐associated PAHs shifted the dominance to particle‐bound PAH for both materials. The substantial degradation in the tests of the low polyurethane content of the PVC carpet, and the (4,4′‐methylenediphenyl diisocyanate)‐based binder in the wood board resulted in no or very small amount of quantifiable diisocyanates. Copyright © 2013 John Wiley & Sons, Ltd.     

Vinyl chloride formation from the thermal degradation of poly(vinyl chloride)

The volatile products from the thermal degradation of poly(vinyl chloride) (PVC) resins and compounds are shown to contain trace amounts of vinyl chloride. Data presented show the effect of temperature and resin type on the amount of vinyl chloride formed. At the maximum temperatures involved in PVC processing which may reach 210°C, vinyl chloride monomer (VCM) evolution amounts to less than 1 ppm (resin basis). A technique employing a thermogravimetric balance and charcoal adsorption of volatiles is described for studying thermal degradation of PVC. The volatiles are analyzed for vinyl chloride by gas chromatography. Peak identity was confirmed by mass spectrometry.     

Vinyl chloride formation from the thermal degradation of poly(vinyl chloride)

The volatile products from the thermal degradation of poly(vinyl chloride) (PVC) resins and compounds are shown to contain trace amounts of vinyl chloride. Data presented show the effect of temperature and resin type on the amount of vinyl chloride formed. At the maximum temperatures involved in PVC processing which may reach 210°C., vinyl chloride monomer (VCM) evolution amounts to less than 1 ppm (resin basis). A technique employing a thermogravimetric balance and charcoal adsorption of volatiles is described for studying thermal degradation of PVC. The volatiles are analyzed for vinyl chloride by gas chromatography. Peak identity was confirmed by mass spectrometry.     

Volatiles from thermal degradation of PVC compounds

Several methods were developed to measure and identify the volatile species generated when PVC is heated to decomposition temperatures. PVC film compound containing various organotin stabilizers was processed under a range of typical conditions. The film samples were subjected to degradation temperatures of 210 to 230°C in both enclosed sampling systems (for optimum collection efficiency) and open systems that were designed to mimic working conditions. The collected samples were analyzed for amounts of hydrogen chloride, organotin compounds and organics in general. Variables such as type of stabilizer, degradation time and temperature, and sample thickness and fusion time were studied.     

Comparison of QUV accelerated weathering to outdoor exposure for PVC compounds

Weathering characteristics of the PVC compounds used for exterior applications, such as house siding, window and door frames, must be determined in order to predict their performance in actual use. In this study color weatherability of various PVC compounds, determined in the QUV accelerated weatherometer, was compared to the outdoor exposure in Arizona, Ohio, and Florida. The effect of the compound base formulation and color on correlation of the QUV to the outdoor weathering has been also analyzed.     

Oilseed volatile analysis by supercritical fluid and thermal desorption methods

A knowledge of the volatile components present in an oil sample can provide important information relative to supercritical fluid extraction (SFE) process design, the current oxidative state of the oil, as well as the concentration and presence of important flavor volatiles in the oil. Volatile compounds from supercritical fluid-extracted oils were analyzed by headspace gas chromatography (GC) methods to determine if there were differences in the volatile profiles when two different methods of desorption were used. Canola, corn, soybean and sunflower seeds were extracted with supercritical carbon dioxide at 8000 psi and 50°C. Tenax porous polymer traps, attached at the exhaust port of the SFE apparatus, were utilized to collect the volatile components during the extractions. The volatile compounds on the Tenax trap were desorbed onto a GC column by both thermal and supercritical fluid techniques. Desorption temperature for the thermal method was 150°C, while conditions for the SFE technique were 50°C and 2000 psi. The lower-boiling volatiles from each oilseed were greater when desorbed by thermal means from the Tenax than by SFE; however, SFE desorbed the highermolecular weight compounds that were not removed by the thermal desorption method. Hexanal tended to be desorbed in comparable amounts by both methods. The SFE-based desorption technique provides a unique analysis method for the determination of both volatile and semivolatile compounds, as well as executing desorption under nonoxidative, low-temperature conditions that do not contribute to the degradation of lipid components.     

XPS and SEM study of UV laser surface modification of polymers

Several commercial polymers—poly(ethylene) (PE), poly(propylene) (PP), poly(vinylidene fluoride) (PVF₂), poly(vinyl chloride) (PVC) and polystyrene (PS)—were treated in air with an argon-fluorine UV excimer laser (λ = 193 nm). The polymer etch rate was investigated by two methods: quartz crystal microbalance (QCM) and piercing of films. X-ray photoelectron spectroscopy (XPS) analysis was performed on the modified surfaces after laser exposure at various fluences. Samples were subsequently analysed by scanning electron microscopy (SEM). From our results, polymers may be classified into two categories concerning their reactivity towards UV laser light. — the weakly absorbing polymers (e.g. PE, PP, PVF₂) where a photothermal process (thermal degradation) dominates the interaction. — the strongly absorbing polymers (e.g. PVC, PS) where a photochemical process (photoablation) dominates the interaction.     

Effect of nanocalcium carbonate on the impact strength and accelerated weatherability of rigid poly(vinyl chloride)/acrylic impact modifier

Poly(vinyl chloride) (PVC) composites filled with nano‐ and micro‐CaCO₃ particles were prepared via a melt blending method. Transmission electron microscopy images revealed better dispersion of nano‐CaCO₃ than micro‐CaCO₃ in the PVC matrix. With more than 5 phr (parts per 100 parts of resin) of nano‐CaCO₃ content, both impact strength and heat stability were improved. Accelerated weathering tests were performed to investigate UV stability. The impact strength and white index obtained upon weathering exposure of PVC/(80 μm CaCO₃) nanocomposites showed a significant improvement upon incorporating nano‐CaCO₃. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Zinc maleate and calcium stearate as a complex thermal stabilizer for poly(vinyl chloride)

Zinc maleate (ZnMA) and calcium maleate (CaMA) were synthesized by reaction of maleic acid with the corresponding metal oxides and were characterized by X‐ray diffraction, thermal analysis, and Fourier‐transform infrared (FTIR) spectroscopy. The thermal stabilizing effects of ZnMA and CaMA on poly(vinyl chloride) (PVC) were investigated at 180°C in air by a static stability test. The stabilization mechanism of ZnMA and the synergism of ZnMA/CaSt₂ (St = stearate) were also studied by UV‐visible and FTIR spectroscopies, as well as a thermal stability test. The PVC with the ZnMA stabilizer exhibited good thermal and color stability caused by the ability of ZnMA to replace the labile chlorine atoms in PVC chains, absorb hydrogen chloride, and react with the polyene intermediates via a Diels–Alder mechanism. The gel content of the PVC/ZnMA samples reached 31% after 2 min of heating and 44% after 10 min, thereby indicating that crosslinking could easily occur with ZnMA, probably owing to catalysis by Zn species. The static and dynamic stability results showed that the synergistic effect of the ZnMA/CaSt₂ stabilizer was greater than that of ZnSt₂/CaSt₂. J. VINYL ADDIT. TECHNOL., 20:1–9, 2014. © 2014 Society of Plastics Engineers     

Photoaging and stabilization of rigid PVC/wood‐fiber composites

Ultraviolet (UV) weathering performance of unpigmented and rutile titanium dioxide pigmented rigid polyvinyl chloride (PVC)/wood‐fiber composites has been studied. The composite samples were manufactured by dry‐blending PVC, wood fibers, and other processing additives in a high‐intensity mixer. The dry‐blended compounds were extruded and compression molded into panel samples. The manufactured samples were artificially weathered using laboratory accelerated UV tests. Composite samples were exposed to 340‐nm fluorescent UV lamps and assessed every 200 h, for a total of 1200 h of accelerated weathering. Each assessment consisted of a visual examination of surface roughness or erosion, a contact angle measurement, a FTIR collection, and a color measurement. The experimental results indicated that wood fibers are effective sensitizers and that their incorporation into a rigid PVC matrix has a deleterious effect on the ability of the matrix to resist degradation caused ultraviolet irradiation. The light stability of these composites could be improved quite efficiently with the addition of rutile titanium dioxide photoactive pigment during formulation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1943–1950, 2001