The side effects of UV light stabilizer on properties of polypropylene based composite tape yarn

Initial consuming properties of polypropylene (PP) based composite tape yarns having different portions of ultraviolet (UV) light stabilizer are studied. In many cases, the samples with different portions of UV light stabilizer exhibit changes at level of initial properties, that is, the statistically significant side effects are obtained. When portion of the additive increases, the initial values of width, thickness and linear density of the modified samples are found to be reduced. The additions of UV light stabilizer also generate the statistically significant changes for the most tensile characteristics. The linear and second order polynomial equations are suggested to show the side effects on the properties. Some visual changes in morphology, that is, the differences in smoothness of the surfaces of the samples are also noticed. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44400.     

Influence of different types of UV absorber/UV stabilizer combination on the photodegradation of PC/ABS blend

The polycarbonate/poly(acrylonitrile butadiene styrene) blends, (PC/ABS), are mainly degraded by sunlight known as photodegradation when exposed to outdoor conditions. It is the ultraviolet (UV) radiation that is responsible for the degradation of the blend. To stabilize against the harmful UV radiation and to scavenge the radical species which arise from UV or thermally induced degradation of the PC or the ABS, UV absorbers, and UV stabilizers are used. In this article three different UV absorbers namely, Tinuvin 1577—hydroxyphenyl triazine type, Cyasorb 5411—benzotriazole type, Uvinul 3030—cyanoacrylate type, and two different UV stabilizers, Tinuvin 765—monomeric hindered amine type, Tinuvin 622—oligomeric hindered amine were compounded in different combinations with PC/ABS blend at 240°C using a twin screw extruder. Accelerated aging of the compounded sample was done by Atlas Suntest apparatus. The photodegradation studies were done using UV–vis, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy, and Yellowing index measurement. The molecular weight of the compounded sample before aging was determined by gel permeation chromatography (GPC). It was found that samples protected with hydroxyphenyl triazine type UV absorber and oligomeric hindered amine show the best result for decreasing the degradation products, oxidation rate, and yellowing of the PC/ABS blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanism of the benzophenone-sensitized photodegradation of polypropylene

The photodegradation of polypropylene sensitized by benzophenone has been studied under accelerated light-aging conditions using a Xenotest 150. Degradation of the polymer and consumption of the benzophenone was monitored by infrared spectroscopy. The results indicate that hydrogen stom abstraction from the polymer, by photo-excited benzophenone, is the major primary process in the mechanism of sensitized photodegradation.     

聚丙烯结构与光降解研究进展

主要论述了均聚聚丙烯(PPH)、嵌段共聚聚丙烯(PPB)和无规共聚聚丙烯(PPR)的结构和特点。重点介绍了聚丙烯(PP)在氧气、氮气和含有光敏剂时的紫外光降解机理及紫外光降解研究进展。     

The effects of chemical structure and synthesis method on photodegradation of polypropylene

The effects of chemical structure and synthesis method on the photodegradation behavior of polypropylene (PP) were investigated in injection‐molded samples exposed to ultraviolet radiation (UV) at 60°C. For this purpose, three PP samples with different chemical structures were chosen: two homopolymerized PP samples (H₁P, synthesized by bulk polymerization; whereas H₂P was synthesized by Ziegler–Natta catalyst) and copolymerized PP sample (CP). The photodegradation was characterized by melt flow rate and mechanical properties and Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and scanning electron microscopy. The results showed that CP possesses the most superior resistance to UV‐irradiation, followed by H₂P and then H₁P, which indicates that copolymerization with a small amount of ethylene monomer is an effective approach to obtain high stability of PP to UV‐irradiation, and synthesis methods of PP play an important role in the resistance to UV‐irradiation. Moreover, the effect of photodegradation on the thermal behaviors of H₂P was also investigated using X‐ray diffraction, differential scanning calorimetry, and dynamical mechanical thermal analysis. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 270–279, 2005     

Stereoblock polypropylene/isotactic polypropylene blends. IV. Cocrystallization and phase separation

The blending process of stereoblock isotactic polypropylene and isotactic polypropylene (sbiPP/iPP) including a well distribution of the components (by solvent mixing), posterior hot pressing (shear mixing), and a final quenching into ice water freezing these blends at room temperature in a particular flow oriented cocrystallized structure. This structure gives rise to a birefringent pattern which is stable up to 170°C when it disappears by melting. In the molten state the two components segregate destroying the original flow oriented structure. In the following cooling the iPP crystallizes in a spherulitic form and the sbiPP phase crystallizes only partially disturbed by the restrictions imposed by the iPP crystals. © 1996 John Wiley & Sons, Inc.     

Photostabilization of commercial polypropylene by a hindered amine stabilizer

The photostabilization of commercial polypropylene by a hindered amine stabilizer is examined by luminescence and ESR spectroscopy. The presence of the amine stabilizer inhibits the photolysis of the α,β unsaturated carbonyl impurity groups present in the polymer. Examination by ESR, of the stabilized polymer before and after irradiation shows the development of a highly stabilized free radical indicating that the stabilizer can act as an ultraviolet stable antioxidant. Possible mechanisms whereby the hindered amine inhibits the photolysis of the α,β unsaturated carbonyl groups are discussed.     

金红石型TiO2对聚丙烯纤维紫外光降解的影响

分析了聚丙烯(PP)／金红石型二氧化钛(TiO2)共混纤维在人工加速紫外光降解中断裂伸长率、断裂强度、质量损失和表面形态的变化,与PP纤维进行对比,研究了纳米级和微米级金红石型TiO2对共混纤维光降解的影响。结果表明,在紫外光照射下,共混纤维中金红石型TiO2的含量越高,PP纤维断裂伸长率、断裂强度的降低和质量损失速率就越快;同时由扫描电镜照片发现,经紫外光照射120 h后,纤维表面损伤程度也随着TiO2添加量的增多而加深。纳米级和微米级金红石型TiO2都对PP的光氧化降解具有一定的催化作用,而且其含量越高,催化作用越强,但纳米级TiO2的催化作用比微米级TiO2大。     

纳米ZnO 对 PP自然光降解的影响

在PP中添加O～1.2%的纳米ZnO粉体,通过共混熔融纺丝纺制成纤维,研究了共混纤维在自然光照射条件下的力学性能变化。结果表明,随着纳米ZnO用量的增加,共混纤维的断裂伸长率、断裂强度都迅速地降低,快速降解的起始点和断裂仲长率降低一半所需要的时间也逐步缩短。说明纳米ZnO对PP的自然光降解具有一定的催化作用,可用作PP材料可控光降解的光敏剂。     

Radiation-modified atactic polypropylene as a sensitizer for photodegradation of polyethylene

Atactic polypropylene (APP) was dissolved in CCl₄ and irradiated with ⁶⁰Co gamma rays in various gas atmospheres (air, O₂, N₂, and Cl₂). A small amount of the irradiated APP was blended with polyethylene (PE) as a sensitizer for photodegradation of PE. There was no significant acceleration of decrease in yield strength of PE with UV exposure when oxidized APP or chlorinated APP was used. On the contrary, the use of the APP which was both oxidized and chlorinated caused a considerable acceleration of decrease in both yield strength and elongation. From the fact that the amount of carbonyl groups formed in the matrix PE with UV light exposure was closely related to both the amount of carbonyl groups and the amount of C? Cl bonds existing in the APP before the UV exposure, it was concluded that the combined action of carbonyl groups and C? Cl bonds in the sensitizer is important in the promotion of the photodegradation of the matrix polymer.     

Oligomer of o-xylene as a heat stabilizer for isotactic polypropylene

Oligomers of o-xylene (molecular weight ～400) have been shown to be novel heat stabilizers for isotatic polypropylene film. In contrast to unstabilized films which failed after exposure of 5 hr in a 150°C air oven, a film containing 0.5 and 1.0 wt-% of the o-xylene oligomer survived 100 and 226 hr, respectively. Furthermore if 0.25% dilauryl thiodipropionate (DLTP) was also present, only 0.1 wt-% of the o-xylene oligomer was necessary to maintain a film intact up to 124 hr. In absence of DLTP, this low level of o-xylene oligomer was not effective. Oligomers of toluene, m-xylene, p-xylene, and 1,2,4-trimethyl benzene were found less effective.     

Physical chemistry of a phosphite processing stabilizer in polypropylene. Part 1: Solubility

The solubility of a commercial aryl phosphite processing stabilizer for ployolefins, {tris (2,4‐di‐t‐butylphenyl)} (irgafos 168, Ciba Speciality Chemicals), has been measured in polypropylene over a range of temperatures. Measurements are complicated by hydrolsis of the phosphite, releasing 2,4‐di‐t‐butylphenol, which is much more soluble in the polymer. We have measured the solubility of this phenol, and of the phosphate oxidation product of the stabilizer. The result are interpreted on the basis of a regular solution model. They show that the phosphite has a very low solubility but that it is not particularly anomalous in comparison with other stabilizers of similar molecular weight and polarity. The phosphate is significantly more soluble than the phosphite at 70°C, but their solubiliies are comparable at 25°C. This is mainly due to the lower heat of fusion and melting point of the phosphate, whose compatibility is actually lower than that of the phosphite. The phenol is much more soluble because of its low melting point.     

Effect of stabilizer on the radiation grafting of methylmethacrylate onto polypropylene

The effects of the molecular weight of polypropylene, nucleating agent, and types of stabilizers on the grafting of methylmethacrylate onto polypropylene sheets were examined. The oxidation of polypropylene sheet surfaces exposed to air after irradiation was studied by measuring survey scan spectra with an X-ray photoelectron spectrometer (XPS). The 1,1-diphenyl-2-picrylhydrazyl (DPPH) technique was utilized to evaluate the concentration of peroxide formed on the irradiated polypropylene sheet by counting the quantity of DPPH consumed by the reaction of peroxide radicals with DPPH. Plastics stabilizers caused a decrease in the concentration of peroxide in the polymer as well as trapped radicals. It was shown that the stabilizer in polypropylene markedly decreased the grafting of methylmethacrylate onto polypropylene. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2323–2330, 1998     

The influence of light on the thermal decomposition of polypropylene fibers

The influence of exposure to artificial light (ultraviolet and visible spectrum) on the thermal degradation process of polypropylene fiber has been investigated. The activation energy E as a kinetic parameter of the fiber thermal decomposition has been defined by means of the Flynn–Wall and Freeman–Carroll methods. The fiber melting temperature range was also defined. The investigations have been made on the basis the of thermal gravimetric analysis and differential thermal gravimetric analysis curves determined at various heating speeds, in the temperature range from 100°–600°C. It was found that thermal stability of polypropylene fiber is reduced by light treatment (i.e., fiber softens and melts at a lower temperature). Activation energy values determined for thermal decomposition of the fiber samples exposed to the influence of light are considerably higher than the values determined on unexposed samples. The decomposition process of aged fiber is more complex and occurs in a larger temperature range. Both the methods used show almost similar results. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2237–2244, 1999