The mechanism for inorganic fillers accelerating and inhibiting the UV irradiation aging behaviors of rigid poly(vinyl chloride)

The UV irradiation aging behaviors of PVC composites with several inorganic fillers were studied through Fourier transform spectroscopy (FTIR), ultraviolet spectroscopy (UV‐Vis), differential scanning calorimeter (DSC), scanning electron microscopy (SEM), and mechanical property test. It was found that incorporation of a small amount of the inorganic fillers such as CaCO₃, talc and SiO₂ could hold up the UV aging behaviors of PVC. Those filler‐filled PVC composites sheets after 20 days UV irradiation maintain lower carbonyl index (CI) and good appearance of surfaces, as compared with the corresponding neat PVC sheets, ascribed to high reflection of those fillers to UV light. While montmorillonite (MMT) and pyrophyllite fillers could accelerate the UV aging behaviors of PVC, which could be concluded from both the sharp increase of the CI and lower T_g due to the chain scission reactions because of their high absorbance of these fillers to UV light in 290–400 nm. In these two PVC composites, UV irradiation caused the deterioration of their mechanical properties and the appearance of rough, cracked and chalked surfaces after 20 days UV irradiation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical and fracture behavior of an artificially ultraviolet‐irradiated poly(ethylene‐carbon monoxide) copolymer

In this work, 1 wt % carbon monoxide (CO) poly(ethylene‐carbon monoxide) (ECO) copolymer sheets were artificially exposed to ultraviolet (UV) light with a power density of 3 mW/cm² for up to 130 h. A thorough mechanical characterization of the irradiated material was conducted, in which both the stress–strain data and the values of the quasistatic crack initiation and growth toughness were measured and correlated with companion uniaxial tensile tests and single‐edge‐notched fracture tests. Average values of the elastic modulus, failure strain, and failure stress were determined from the tensile tests. The full‐field optical technique of digital image correlation was used to quantify in‐plane deformation (displacements and displacement gradients) during the fracture experiments and to extract values of the crack initiation and growth fracture toughness. The elastic modulus increased monotonically with UV irradiation for the exposure times used in this investigation. In addition, for low irradiation times of less than 5 h, both the failure strain and failure stress of ECO decreased, and this caused a corresponding decrease in the crack initiation and growth toughness. However, for longer irradiation times, the failure strain remained almost invariable, whereas the failure stress increased by about 25% over that of unirradiated ECO. As a result, for longer irradiation times (>5 h), 1 wt % CO ECO became not only stiffer but also stronger and tougher, as quantified by companion fracture experiments. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 139–148, 2004     

Stress photo‐oxidative aging behaviour of polyamide 6

The long‐term stress accelerating aging behaviour of polyamide 6 (PA6) was studied by exposure to UV irradiation. The aging behaviour and mechanism were investigated in terms of creep behaviour, mechanical properties, chemical structure, crystallization and orientation behaviour. It was found that the creep deformation of PA6 under stress/UV irradiation was lower than that of the sample aging only under stress, resulting from crosslinking and low mobility of molecules under UV irradiation. The tensile strength of PA6 under stress and stress/UV irradiation substantially increased at the primary aging stage due to stress‐induced molecular orientation. The oxidation of PA6 may also be inhibited by orientation, leading to a relatively low content of carboxylic groups. Under UV irradiation, stress accelerates the degradation of PA6, resulting in strengthening UV absorption due to formation of isolated carbonyl groups. The melt temperature and crystallinity both showed an increase with time, which were much higher for the sample aged under stress/UV irradiation than for that aged only under UV irradiation. Wide‐angle X‐ray diffraction analysis also showed that the orientation factor and crystallinity of PA6 increased with aging time before 16 days, indicating a clear orientation and crystallization of molecules induced by stress. The UV‐induced crosslinking reduced the mobility of PA6 chains, resulting in a lower crystallinity and orientation factor of the sample aged under stress/UV irradiation compared with that under stress aging only. Copyright © 2011 Society of Chemical Industry     

Syntheses and properties of photodegradable polystyrene-containing carbonyl group

The copolymerizations of styrene (St) and methyl vinyl ketone (MVK) or phenyl vinyl ketone (PVK) were carried out in benzene by using azobisisobutylonitrile (AIBN). The synthesized copolymers, poly(St-co-MVK) and poly(St-co-PVK), were identified by infrared (IR) spectroscopy. Under the presence of oxygen, the copolymers containing carbonyl group after UV irradiation showed photodegradable properties that caused by Norrish Type II reaction. The new IR characteristic peaks, such as carbonyl and vinyl groups of the photooxidized copolymers, increased by increasing UV irradiation time. In the photodegradation property, the color differences of the synthesized copolymers were higher than those of polystyrene with increasing UV irradiation time, which was caused by the inherent photodegradable property of carbonyl unit in copolymers. The average molecular weights of samples after UV irradiation for 300 h decreased, as compared with polymers before irradiation. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1237–1242, 1998     

Ozone treatment of water-soluble polymers. V. Ultraviolet irradiation effects on the ozonization of polyacrylamide

Polyacrylamide was ozonized in aqueous solution (at pH 2, 7, and 11) under UV irradiation with a low-pressure mercury lamp. The breakage of the polymer chains by ozone was strongly accelerated by UV irradiation under acidic and neutral conditions. Formaldehyde was produced characteristically in the UV ozonization. From the correlation between the amount of formaldehyde and the number of breaks of polymer chains, it was presumed that one molecule of formaldehyde resulted from the chain breakage, at least under acidic conditions. The intensity of the UV absorption peak at 266 nm (285 nm in the UV ozonization at pH 2), which was presumed to be due to the carbonyl groups, namely, ketone and terminal aldehyde produced by ozonization, was very much stronger than that in simple ozonization. Oxamic acid and oxamide as end products were observed in the solution which was ozonized exhaustively under UV irradiation.     

竹纤维/MUF复合材料的老化性能研究

以质量损失率、机械强度、羰基指数及乙烯基指数的变化作为综合指标,采用紫外光加速老化试验研究纳米SiO2和纳米TiO2对竹纤维(BF)/三聚氰胺-甲醛-尿素(MUF)复合材料紫外光老化性能的影响。结果表明,随着紫外光老化时间的延长,竹纤维/MUF复合材料的质量损失率、羰基指数和乙烯基指数增加,弯曲强度和冲击强度下降;纳米SiO2和纳米TiO2对竹纤维/MUF复合材料的紫外老化有一定的延缓作用。     

Gloss and degradation of hydroxyl polyacrylic resin/hexamethylene‐1,6‐diisocyanate coatings under ultraviolet and natural‐exposure aging

Reactive coatings of hydroxyl polyacrylic resin (HPAR) with hexamethylene‐1,6‐diisocyanate were carried out under accelerated 313‐nm ultraviolet (UV) aging for 2000 h and under natural exposure in Lhasa, Tibet, for 24 months. With UV irradiation and exposure time, the gloss changes in coatings with HPAR containing 3.0% or less hydroxyl groups decreased exponentially, whereas the gloss decay of coatings with HPAR containing over 4.5% hydroxyl groups decreased linearly. During 254‐nm UV aging, the gloss changes in coatings with HPAR containing 1.4% or less hydroxyl groups decreased as a Gaussian function. The weather resistance of a coating was correlated to the HPAR, UV irradiation, temperature, and humidity. Scanning electron microscopy indicated that there were degradation reactions and that some substance was lost in the matrix polymer during accelerated UV aging; then, uneven surfaces appeared and caused decreased gloss. Accelerated UV aging was faster than natural‐exposure aging, and the aging velocity of 254‐nm UV was 3–5 times faster than that of 313‐nm UV. Through the changes in the gloss, the aging tolerance of a coating could be monitored, and its aging resistance could also be predicted. The dynamic mechanical thermal analysis results showed that the coatings had good properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1271–1278, 2007     

Effect of pro‐oxidants on biodegradation of polyethylene (LDPE) by indigenous fungal isolate,Aspergillus oryzae

Proxidant additives represent a promising solution to the problem of the environment contamination with polyethylene film litter. Pro‐oxidants accelerate photo‐ and thermo‐oxidation and consequent polymer chain cleavage rendering the product apparently more susceptible to biodegradation. In the present study, fungal strain, Aspergillus oryzae isolated from HDPE film (buried in soil for 3 months) utilized abiotically treated polyethylene (LDPE) as a sole carbon source and degraded it. Treatment with pro‐oxidant, manganese stearate followed by UV irradiation and incubation with A. oryzae resulted in maximum decrease in percentage of elongation and tensile strength by 62 and 51%, respectively, compared with other pro‐oxidant treated LDPE films which showed 45% (titanium stearate), 40% (iron stearate), and 39% (cobalt stearate) decrease in tensile strength. Fourier transform infrared (FTIR) analysis of proxidant treated LDPE films revealed generation of more number of carbonyl and carboxylic groups (1630–1840 cm⁻¹ and 1220–1340 cm⁻¹) compared with UV treated film. When these films were incubated with A. oryzae for 3 months complete degradation of carbonyl and carboxylic groups was achieved. Scanning electron microscopy of untreated and treated LDPE films also revealed that polymer has undergone degradation after abiotic and biotic treatments. This concludes proxidant treatment before UV irradiation accelerated photo‐oxidation of LDPE, caused functional groups to be generated in the polyethylene film and this resulted in biodegradation due to the consumption of carbonyl and carboxylic groups by A. oryzae which was evident by reduction in carbonyl peaks. Among the pro‐oxidants, manganese stearate treatment caused maximum degradation of polyethylene. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and fluorescence studies of dual-responsive nanoparticles based on amphiphilic azobenzene-contained poly (monomethyl itaconate)

Here photo- and pH-responsive behavior of polymer micelles formed by synthesized azo-modified poly (monomethyl itaconate)s (PMMI-Azo) with appropriate amounts of azobenzene side groups (DS_Azo) were reported. The PMMI-Azo polymer with DS_azo?=?20 was used for the preparation of micelles using dialysis method. Self-assembly behavior of the PMMI-Azo was studied by transmission electron microscopy (TEM), fluorescence spectroscopy, dynamic light scattering (DLS) and UV–Vis spectrophotometry techniques. It was found that the PMMI-Azo polymers self-assembled into spherical micelles with core-shell structures. TEM images and DLS analysis of the PMMI-Azo-20 micelles showed regular spherical micelles which increased in size and polydispersity index after UV irradiation, caused by isomerization. It was also found that with increasing the polymer concentration, the fluorescence intensity decreased obviously which could be attributed to the interactions between the closely located pyrene and azobenzene in the micelles core. Experimental results suggested that the micellization-enhanced fluorescence was caused by a slowdown in the rate of the trans-to-cis photoisomerization. Furthermore, it was found that the fluorescence intensity of the aqueous micellar solutions was sensitive to stimulus such as pH change and UV light irradiation, as a result of alteration in aqueous micellar association. The results clearly indicated the role of UV irradiation and pH in the state of the polymer micellar association which is responsible for fluorescence intensity.     

The photodegradation and biodegradation of rEPS/curaua fiber composites

The development of composite materials comprised of postconsumer polymers and natural fibers is important for the possibility to obtain materials that are more compatible with the environment. Depending on the application of these materials and their final disposal, the relevant degradation processes must be considered in the studies of these materials. The aim of this work is to evaluate the effect of the degradation process in simulated soil and in the aging accelerated UV chamber on the properties (tensile strength, chemical, morphology) of the composites developed with recycled expanded polystyrene matrix reinforced by curaua fiber. In the tensile strength tests, it was found that the presence of the curaua fiber and the coupling agent did not have significant effect in the degradation processes of the polymer matrix. However, the use of the coupling agent without the addition of fiber curaua promoted the accelerated degradation of the matrix. The carbonyl index was used as the main assessment parameter of the degradation of the composites, since an increasing in the carbonyl index was observed in the initial periods of degradation decreasing for longer time periods. The presence of cracks in the samples following exposure to UV was observed, but no biofilm formation was identified in the samples exposed to the simulated soil. POLYM. COMPOS., 34:967–977, 2013. © 2013 Society of Plastics Engineers     

自制光稳定剂HWPAN-g-TiO2与几种光稳定剂对聚丙烯性能的对比研究

利用废旧腈纶织物制备了一种聚丙烯（PP）用大分子紫外屏蔽吸收类型光稳定剂,利用其和通用的受阻酚类光稳定剂分别制备耐候性PP复合材料,并进行了人工加速老化实验。探究了大分子紫外屏蔽吸收类型光稳定剂在PP老化过程中对PP老化降解的影响,并与通用的受阻酚类光稳定剂进行了对比研究。结果表明,大分子紫外屏蔽吸收类型光稳定剂效果明显,在人工加速老化500 h之后,PP的羰基指数高达150.3;而PP/HWPAN-g-TiO2仅为53,与此同时,PP的拉伸强度从25 MPa降至6.9 MPa,下降了72.4 %;而PP/HWPAN-g-TiO2的拉伸强度从29 MPa降至25 MPa,下降13.8 %。     

Synthesis and photodegradable properties of methyl vinyl ketone–EPDM–styrene graft terpolymer

The graft terpolymerization of methyl vinyl ketone (MVK) and styrene (St) onto ethylene–propylene–diene terpolymer (EPDM) was carried out under various polymerization conditions. The synthesized graft terpolymer, MVK–EPDM–St (MVES), was identified by infrared (IR) spectroscopy. The effects of monomer concentration, mole ratio of MVK to St, reaction time, reaction temperature, and initiator concentration on the graft terpolymerization were examined. Upon UV irradiation in the presence of oxygen, the MVES-containing carbonyl group showed photodegradable properties caused by Norrish type II reaction. The new IR characteristic peaks, such as carbonyl, vinyl, and hydroxy groups of the photodegraded MVES, increased with increasing UV irradiation time. The tensile strength and elongation at break of MVES after UV irradiation were lower than those of before UV irradiation. The color difference of the irradiated MVES was higher than that of EPDM. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1721–1727, 1998     

Variations of regular conformation structures in melt of syndiotactic polypropylene

Regular structures in polymer melt play important roles during crystallization and subsequently influence performances of polymer materials. In the present work, differential scanning calorimetry (DSC) and variable temperature Fourier transform infrared spectroscopy (VT-FTIR) were used to characterize the variations of regular structures in melt of syndiotactic polypropylene (sPP) during heating. It was found that during heating, the structural transition in sPP melt undergoes four stages: (1) destruction of long regular structures; (2) formation of short regular structures; (3) transition from short regular structures to isotropic state; and (4) isotropic state. These regular structures in sPP melt have distinct memory effects on the crystallization behaviors. By using Flory's RIS model, it was found that in final isotropic state, the most common conformers are ttgg and tttt, corresponding to helical and planar-zigzag conformations, respectively. These findings are helpful to deeply understand the essence of structures in sPP melt and microstructure variations during melting.     

Design of organic electroluminescent displays with ultraviolet‐shielding filters

The electroluminescence properties of polymer light‐emitting devices with and without an ultraviolet (UV)‐shielding filter were studied. The polymer light‐emitting devices were fabricated with poly(2‐methoxy‐5,2′‐ethyl‐hexyloxy‐1,4‐phenylene vinylene) as the light emitter and poly(ethylenedioxy thiophene) as the hole‐transporting material. The UV‐shielding filter was composed of alternating TiO₂ and SiO₂ dielectric multilayers made by a physical vacuum deposition process. The current density, brightness, and photometric efficiency decreased significantly for the polymer light‐emitting device without the UV‐shielding filter after irradiation by UV light. The decay of PLEDs due to UV degradation was greatly reduced by the UV‐shielding filter. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1432–1436, 2004     

Different photodegradation processes of PVC with different average degrees of polymerization

The influence of ultraviolet (UV)‐irradiation on the photodegradation mechanism of different average degrees of polymerization (DP ) of poly(vinyl) chloride (PVC) with UV‐irradiation time was investigated by viscosity‐average molecular weight determination, UV‐vis spectroscopy, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), contact angle measurement, and scanning electron microscopy (SEM). PVC films with different DP (800, 1000, 1300, 3000) were prepared by solution casting. It was carried out exposing specimens to a xenon‐arc light source with a spectral irradiance of 0.68 W/(m² ·nm) at 63°C. It was found that the photodegradation mechanism of the lower DP of PVC (DP = 1000) was different from the higher DP of PVC (DP = 3000). This was because the lower DP of PVC was a homopolymer, while the higher DP of PVC was often produced by copolymerizing with a certain quantity of crosslinking agent (e.g., DAP and DAM). UV‐vis and FTIR spectroscopy studies provided some results concerning the structure of the irradiated PVC, and the carbonyl index and C? Cl index were induced to study the process of PVC photodegradation with different DP . TGA showed that the degradation temperatures of different weight loss increased with the irradiation time. The surface morphology of the irradiated polymer films with different DP was observed by contact angle measurement and SEM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photocrosslinking of an ethylene–propylene–diene terpolymer and the characterization of its structure and mechanical properties

An ethylene–propylene–diene terpolymer (EPDM) was photocrosslinked under UV irradiation with benzil dimethyl ketal (BDK) as a photoinitiator and trimethylolpropane triacrylate (TMPTA) as a crosslinker. The efficiency of the photoinitiated crosslinking system EPDM–BDK–TMPTA, various factors affecting the crosslinking process (the photoinitiator and crosslinker and their concentrations, the irradiation time, the temperature, the atmosphere and UV‐light intensity, and the depth of the UV‐light penetration), and the mechanical properties of photocrosslinked EPDM were examined extensively through the determination of the gel contents, infrared spectra, and mechanical measurements. EPDM samples 3 mm thick were easily crosslinked with a gel content of about 90% after 30 s of UV irradiation under optimum conditions. The photoinitiating system of a suitable initiator combined with a multifunctional crosslinker such as BDK–TMPTA enhanced the efficiency of the photocrosslinking reaction, especially by increasing the initial rate of crosslinking. The gel content of photocrosslinked EPDM, which was determined by the content of diene in EPDM, the depth of the UV‐light penetration, and the light intensity, played a key role in increasing the mechanical properties of the photocrosslinked samples in this work. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1837–1845, 2004     

Transport properties of organic vapors in nanocomposites of organophilic layered silicate and syndiotactic polypropylene

Syndiotactic polypropylene (sPP) nanocomposites were obtained by melt blending synthetic fluorohectorite modified octadecyl ammmonium ions (OLS), and maleic-anhydride-grafted isotactic polypropylene (iPP-g-MA) as compatibilizer. The composition of the inorganic material was varied between 5 and 20 w/w%. Films of the composites were obtained by hot press molding the pellets. Melt-direct polymer intercalation of sPP into the OLS gave rise to nanocomposites in which the silicate layers were delaminated at low clay contents, and ordered to intercalated structures at the highest clay content. The elastic modulus was higher than for the pure polymer in a wide temperature range and increased with the inorganic content. The transport properties were measured for dichloromethane and n-pentane. The sorption was reduced compared to pure sPP. There were not significative differences between the samples having different inorganic contents. The diffusion coefficient decreased with increasing clay content. Permeability (P) showed a strong decreasing dependence on the clay content. The improvement of the barrier properties was largely caused by the reduced diffusion.     

Stabilizations of molecular structures and mechanical properties of PVC and wood/PVC composites by Tinuvin and TiO2 stabilizers

Three different UV stabilizers, 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐ditertpentylphenol (Tinuvin XT833), 2‐(2H‐benzotriazol‐2‐yl)‐p‐cresol (Tinuvin P), or rutile–titanium dioxide (TiO₂) were incorporated into poly(vinyl chloride) (PVC) and wood/PVC (WPVC) composite, and mechanical and physical properties and photostabilities were monitored. The polyene and carbonyl sequences of PVC increased with UV weathering time and with presence of wood flour. The yellowness index increased because of polyene and carbonyl productions, whereas the brightness increased because of the photobleaching of lignin in wood. The photostabilities of PVC and WPVC could be improved through the use of UV stabilizers. Tinuvin P was recommended in this work as the most effective stabilizer for PVC and WPVC composites. The stabilization effect was interfered by presence of wood particles. The mechanical property changes corresponded well to the structural changes under UV for neat PVC. For WPVC composites, the presence of wood particles played more significant effect on the mechanical properties during UV aging than the UV stabilizer. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Electroactive polymer patterns with metal incorporation on a polymeric substrate

Electroactive polymer patterns on a polymeric substrate were fabricated using either a UV lithographic approach or plasma polymerization method. For the lithographic patterning technique, photosensitive thin films comprising polyaniline (PANI) coatings on viologen‐grafted low‐density polyethylene (LDPE) substrates were first prepared. The composite film was subsequently exposed to UV irradiation through a mask. Under UV irradiation, reactions between PANI and viologen occurred, resulting in the conversion of the PANI to a doped state. The PANI micropatterns were developed by using N‐methylpyrrolidinone (NMP) to dissolve the soluble‐unexposed (and hence undoped) parts. The use of Ar plasma treatment of the composite film instead of UV irradiation was not successful in inducing the doping reaction between PANI and viologen. On the other hand, plasma polymerization was shown to be another convenient way for the selective surface deposition of aniline polymer on the surface of the LDPE substrate through a mask. The further incorporation of metal/metal ions in both the PANI‐viologen and plasma polymerized aniline system was successfully carried out on the micropatterns. Polym. Eng. Sci. 44:2061–2069, 2004. © 2004 Society of Plastics Engineers.     

FeSt_3对煤基聚乙烯薄膜光-热降解性能的影响

通过拉伸强度和断裂伸长率、TG以及FTIR的测试分析,研究硬脂酸铁(FeSt_3)含量不同的4种煤基聚乙烯薄膜在模拟自然先条件下的光.热降解性能.结果表明:光照时薄膜中添加的煤粉在FeSt_3作用下发生自由基反应,引发聚乙烯大分子断链,产生羰基;羰基指数随薄膜中FeSt_3含量的增加而增大,但薄膜力学性能相应降低,热稳定性则有所增强;聚乙烯大分子链结构在光照作用下发生脱羰基反应,断裂成小分子链;降解薄膜在光照72小时前处于衰变期,72小时后进入脆变期.