Photo-oxidation of polystyrene in dichloromethane solutions

Photo-oxidation of polystyrene in dichloromethane solution irradiated with light absorbed by the polymer was investigated. The quantum yields of the formation of acetophenone-type carbonyl compounds as well as α, β-enone and dicarbonyl products were calculated based on the analysis of u.v. absorption spectra of irradiated solutions. The relationship between the concentration of these products was found.     

Photo-oxidation of polystyrene film: 1. Photo-oxidation of polystyrene films with light absorbed by polymer

The photo-oxidation of polystyrene films irradiated with light absorbed by the polymer has been studied. The overall quantum yield of hydroperoxide as well as the relationship between the concentration of acetophenone-type carbonyl products and α,β-enone and diketone products were found. The spatial distribution of the different types of carbonyl products was investigated.     

Photo-oxidation and photoreduction of bis(dithiobenzil)nickels

Photo-oxidation and photoreduction of bis(dithiobenzil)nickels have been investigated. The quantum yields for photo-oxidation of anionic bis(dithiobenzil)nickels by u.v. irradiation (313 nm) were in the range 0.07–0.14 in dichloromethane, and this photo-oxidation on poly(methylmethacrylate) was also observed. Some of the neutral bis(dithiobenzil)nickels in acetonitrile/benzene mixture were photoreduced in the presence of methylene blue as a sensitiser by irradiation in visible light (>390 nm), and a significant substituent effect was observed.     

Photo-oxidation stabilization of polystyrene by aromatic ultraviolet light absorbers forming charge transfer complexes

Summary The aim of this work was to investigate the influence of UV light absorbing additives on the rate of ultra violet light initiated degradation of polystyrene (PS) in solutions. Anthracene (ANT), chloranil (CA) nitrobenzene (TNB) which can form cnarge transfer complexes between each other were used. It was found for illuminated PS-solutions by light of =254 nm that independently of the screening efficiency of these compounds, tne formed CT complexes ANT-CA and ANT-TNB cause a decrease of tne rate constant of degradation and of the value of the number average of chain scission S. This effect is due to the energy transfer from the excited polymer chain segments to the low energy triplets of these CT-complexes thus hindering the rection of polymer chain segments with oxygen leading to slowing down of photodegradation.     

XPS studies of poly(acrylic acid) grafted onto UV photo-oxidized polystyrene surfaces

UV photo-oxidation of polystyrene was achieved with 253.7 and 253.7/184.9?nm radiation in the presence of an atmospheric pressure of oxygen and analyzed by X-ray photoelectron spectroscopy as a function of treatment time. A methodical increase in the atomic percentage (at.%) of oxygen occurred during 253.7?nm activation up to 2?h of treatment time. Photo-oxidation with the 253.7/184.9?nm lamps resulted in a saturation level of ca. 35 at.% O. Initially, C–O and C=O groups were formed and then O–C=O type moieties. Poly(acrylic acid) was partially and/or thinly grafted onto the oxidized polystyrene surfaces.     

Effect of dicumyl peroxide on photo-oxidation of polystyrene films: 2

The effect of dicumyl peroxide on the photo-oxidation of polystyrene film has been studied using light of a wavelength absorbed by the polystyrene—oxygen complex. Energy transfer from the excited polystyrene—oxygen complex to the peroxide present in polystyrene film was considered to be the process of most importance in the initiation of polystyrene long-wave photo-oxidation.     

Photo-oxidation of phenoxy resin

A study has been made of the photolysis and photo-oxidation of phenoxy resin. Photolysis results in the evolution of hydrogen, methane, ethane, propene, propane, toluene, and the oxides of carbon. Also observed are increased yellowing, a rapid rise in gel content, and a decrease in intrinsic viscosity and elongation. Photo-oxidation causes similar changes, but produces oxidized chain fragments, more gel, and less yellowing as well as broad absorptions in the hydroxyl and carbonyl regions of the infrared spectrum. A free-radical mechanism is proposed in which both chain scission and crosslinking occur.     

星状支化PS的合成与表征

利用原子转移自由基聚合方法,以α-溴代苯乙烷为引发剂,CuBr／2,2'-联二吡啶作为催化体系,合成星状支化聚苯乙烯(PS)。引发二苯甲烷双马来酰亚胺／苯乙烯电荷转移络合物体系就地优先生成多官能团引发剂,再引发苯乙烯聚合。采用核磁共振、凝胶渗透色谱、多角度激光散射和特性黏数等分析方法对聚合过程、聚合物结构、聚合物相对分子质量及其分布进行分析与表征。由多角度激光散射法测定的绝对重均分子量是由凝胶渗透色谱测定的4倍左右,相同相对分子质量的线型PS的特性黏数是星状PS的20倍,证实聚合产物确实具有支化结构。     

Orientation development in tubular film extrusion of polystyrene

The tubular film extrusion of atactic polystyrene is described. The in-plane and out-of-plane birefringence of the polystyrene film was determined and compared with both the kinematics (drawdown, blow-up ratio) and applied tensions and bubble pressures. The data can be correlated by comparing the birefringences with the stresses acting in the film at the position of vitrification. The data compare quantitatively with Oda, White, and Clark's correlation developed for the birefringence of samples vitrified during shear and uniaxial extensional flow. The experimental results are interpreted in terms of White and Spruiell's biaxial orientation factors.     

Chemical modification of polystyrene,III. Electrophilic substitution of polystyrene with aromatic anhydrides

Polystyrene has been chemically modified by Friedel-Crafts acylation reaction with trimellitic anhydride in the presence of anhydrous aluminium chloride as catalyst. The product has been characterized in respect of its structure and physicochemical properties by measuring its total capacity, thermal stability and the behaviour to pH metric titration. The thermal characteristics of the trimellitic anhydride modified polystyrene have been compared with the same for phthalic anhydride and pyromellitic dianhydride modified polystyrene in the light of their structural characteristics.     

Photo-oxidation mechanisms of poly(2,6-dimethyl-1,4-phenylene oxide).

A re-examination of the photo-oxidation mechanism of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) at both long and short irradiation wavelengths under accelerated conditions is reported. The formation rate of poly-2,6-dimethylphenoxy (PDMP) radicals, have been observed by esr spectroscopy, while benzylic-type radicals have been detected by spin trapping experiments using nitrosodurene under UV irradiation conditions. The changes of FTIR spectra obtained under accelerated photo-oxidative conditions show the formation of primary oxidation products such as aromatic aldehydes and quinones. The direct formation of radical cations and superoxide anions by a photo-induced electron-transfer reaction is suggested under our conditions. In addition, some results on the of photo-oxidation PPO/PS blends as a function of polystyrene tacticity are also reported. In the case of syndiotactic polystyrene the blend photostability shows some differences in comparison with the blend containing atactic polystyrene. This effect has been ascribed to the absence of excimers in syndiotactic polystyrene which are not revealed by fluorescence measurements. Finally, the chemical modification of PPO with bromine gave a bromomethylated PPO with different amounts of CH₂ Br groups, which has been used for further substitution reactions with alkoxy sodium salts of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and 4-hydroxy-1,2,2,6,6-pentamethylpiperidine (PMPP). The accelerated photo-oxidation of a modified copolymer PPO-PMPP containing a 60% PMPP moieties as side groups and its blends with pure PPO has been followed by FTIR and esr spectroscopies. Some comparisons with a commercially available hindered amine light stabilizers (HALS) and a modified copolymer PPO-PMPP are also reported under the same photo-oxidative conditions.     

Polymer thin film integrated optics: Fabrication and characterization of polystyrene waveguides

The fabrication and characterization of 1–3 μm polystyrene thin film integrated optical (IO) waveguides is presented. The polymer films were spun-cast onto quartz and glass microscope slides, yielding waveguides of varying quality. The majority of defects in the polymer films appeared to be introduced during the curing process. Laser light (488 nm) was coupled into the polymer films using the prism coupling technique. The collected Raman emission was used to characterize physical and light guiding properties of acceptable polymer films. The Raman intensity spectra collected as a function of the coupling angle supplied data for the calculation of polymer film thickness and refractive index as well as providing general measure of waveguide suitability. The intensity loss due to scatter of several waveguides was also determined to rigorously evaluate waveguide quality.     

肥料用聚苯乙烯包覆膜的制备及其性能的研究

利用废弃聚苯乙烯泡沫塑料为主要材料,对尿素进行包膜来生产缓释化肥。筛选乙酸乙酯或甲苯为溶剂,邻苯二甲酸二丁酯为的增塑剂降低聚苯乙烯的脆性,SBS树脂为增强剂提高聚苯乙烯膜的附着力。结果表明,包膜液的浓度12 %,增塑剂的用量3 %,增强剂用量1 %,包膜肥料的包膜量为10 %。用氮素水中溶出率法和土壤淋溶法研究包膜尿素缓释效果,肥料初期溶出率均低于40 %,在土壤中累计溶出率比普通尿素有大幅降低。说明聚苯乙烯经过改性后对尿素包膜,制得缓释肥的缓释性能良好。     

Photodegradable vinyl plastics. II. Effect of arylmethyl halides,phenyl halomethyl ketones,and haloalkene additives

Three classes of active halogen compounds were effective in promoting photodegradation of polystyrene, polypropylene, and polyethylene. The classes are arylmethyl halides, phenyl halomethyl ketones, and haloalkenes. The additives were blended with the polymers and fabricated into films which were irradiated 66–200 hr with a 275-watt RS sunlamp. Photo-oxidation, as determined by IR spectroscopy, was used as a measure of photodegradation. The relationship between the structure of the additive and its effectiveness as a photoinitiator within each of the three classes of compounds is discussed. In general, photoactivated polystyrene was degraded the most, followed by polypropylene and then polyethylene. Viscosity measurements on irradiated polystyrene containing the additives showed significantly greater molecular weight loss than a polystyrene control.     

The effect of clay particles on film formation from polystyrene latex

Film formation from surfactant‐free polystyrene (PS) latex was performed in the presence of 5% Na‐montmorillonite (NaMMT). The composite films were prepared from pyrene (P)‐labeled PS particles at room temperature and annealed at elevated temperatures above the glass‐transition (T_g) temperature of polystyrene. Scattered light (I_s) and fluorescence intensity (I_P) from P were measured after each annealing step to monitor the stages of composite film formation. Minimum film formation temperature, T₀, and healing temperatures, T_h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were measured. From these results, it was found that the presence of NaMMT in the PS latex film only affects the minimum film formation, but does not affect the void closure and backbone motion activities. POLYM. COMPOS., 27:299–308, 2006. © 2006 Society of Plastics Engineers     

Polyisoprene modified polystyrene

Polyisoprenes have been used to prepare modified polystyrenes in an attempt to improve impact strength. It has been determined that polyisoprene reinforces polystyrene by the formation of complex rubber phase particles, similar to those in commercial polybutadiene reinforced polystyrenes. These particles, however, are subject to breakdown by melt shearing, resulting in a significant drop in impact strength and an increase in tensile strength. This particle destruction is due to the fact that polyisoprene does not crosslink during the polymerization process. It is significant that before shearing these uncrosslinked rubber particles satisfactorily toughen polystyrene.     

Synthesis of polystyrene encapsulated nanosaponite composite latex via miniemulsion polymerization

The synthesis and characterization of polystyrene encapsulated nanosaponite composite suspension via miniemulsion polymerization are reported in this study. The particle size of nanoclay and its pre-modification are critical to successfully producing a stable complex suspension. The final products were characterized by X-ray diffraction spectra, transmission electron microscopy (TEM), scanning electron microscopy (SEM), thin window energy dispersive spectroscopy (EDS), and light scattering. The results show that ar-vinylbenzyltrimethylammonium chloride (VBTAC) modified nanosaponite could be fully exfoliated and encapsulated inside the polystyrene latex via in situ miniemulsion polymerization. When the concentration of hexadecane (a co-stabilizer used in the miniemulsion polymerization) was high, the final composite particles are composed mainly of spherical particles with size less than 100 nm, and a small number of hemispherical or bowl-structured particles of size ∼100 nm to 1000 nm. The phase separation due to the existence of large amounts of hexadecane accounted for the formation of a variety of morphologies.     

Chain conformation of polystyrene in bulk by small-angle X-ray scattering

Small-angle x-ray scattering from solid solutions of different molecular weight fractions of partially brominated polystyrene in polystyrene has been studied. The results of this study indicate that polymer chains in bulk have a radius of gyration proportional to the square root of molecular weight, which is consistent with the random coil model. However, these radii are approximately 20% larger than the unperturbed radii deduced by light scattering in dilute solutions.     

浅色高纯聚苯乙烯磺酸钠阳离子交换树脂的制备

聚苯乙烯磺酸钠阳离子交换树脂是降血钾树脂。用市售的经常规磺化工艺生产的聚苯乙烯磺酸钠阳离子交换树脂(SPSR)为原料,经过脱除苯乙烯、漂白和净化联合工艺处理,得到了浅色高纯SPSR。该浅色树脂达到日本药典(第14版)规定的药用SPSR标准。     

Transparent multiphasic polystyrene/epoxy blends

Blends of polystyrene (PS) with an epoxy monomer (DGEBA) and a tertiary amine (BDMA), were initially miscible at 120°C but phase‐separated at very low conversions in the course of polymerization. Although there was a significant difference between the refractive indices of polystyrene and the DGEBA/BDMA solution, the refractive index of the epoxy network increased in the course of polymerization, attaining a value close to that of PS at complete conversion. A sharp decrease of the light transmittance was observed at the cloud‐point, observed at very low conversions. However, the continuous increase of the refractive index of the epoxy phase with conversion produced an approximate matching of both refractive indices, leading to transparent materials at complete conversion. Morphologies generated by reaction‐induced phase separation depended on the molar mass distribution of polystyrene and its mass fraction in the blend. For a PS with a high value of the mass‐average molar mass (M_w), it was possible to generate a dispersion of PS particles in the epoxy matrix (blends containing 5 wt% PS), phase‐inverted morphologies (blends containing 15 wt% PS) and double‐phase morphologies (blends with 10 wt% PS). Therefore, PS/DGEBA/BDMA blends could be used to obtain transparent epoxy coatings toughened by polystyrene particles or transparent polystyrene parts reinforced by a dispersion of epoxy particles.