外文翻译---关于混有二氧化钛的氧化镁在PVC门窗型材中的可用性研究.docx

外文资料翻译 A study on usability of magnesium oxide with titanium dioxide in PVC door and window profiles1. IntroductionPolyvinyl chloride is among the most widely used synthetic organic polymer materials. Plasticized polyvinyl chloride compositions are widely encountered as, for instance,vinyl sheet goods and as objects formed from plastisols.Polyvinyl chloride is commercially available in a variety of grades, some of which are suitable for preparing rigid,plasticizer-free compositions for extrusion .For plastics, prolonged exposure to the suns electromagnetic radiation in the ultraviolet (UV) region can lead to photooxdiation and degradation of physical properties, often manifested by color change and embrittlement. Similarly,the UV component of ordinary fluorescent lighting can degrade polymers and many of the additives used with them.The effective UV radiation that does reach the earths surface extends from about 290400 nm. This range happens to include the highest energy component UV band, and the segment around 300 nm, which is the most distractive to plastics. Some man-made high-energy radiation sources mercury arc lamps, xenon arcs, carbon arcs, and various sun-lamps can emit radiation at wave lengths below 290 nm and these can degrade plastics even more severely than natural sun light. Hence, they are often used for accelerated testing of plastics.The energy content of UV radiation in the 290400 nm can rupture most of the chemical bonds present in polymer structures. Not all the polymers are equally affected by UV radiation, and some have a degree of resistance, otably polymethyl methacrylates and fluorocarbons. Others, that in their pure forms could be expected to be resistant to UV, are degraded because of contaminants present that act as sites for UV energy absorption.Absorption of radiation energy by polymer produces molecular excitations: if the level of absorbed energy is high enough, it can activate a chemical reaction whereby internal bonds (carbon to carbon, carbon to hydrogen, carbon to halogen, etc.) are broken so that polymer degradation results. PVC is damaged by dehydrochlorination (release of hydrogen chloride), autooxidation and echanochemical chain scission. This degradation is caused by the simultaneous sequence of these reactions.Dehydrochlorination, prevailing reaction during processing,leads to increasing discoloration. In the course of the proceeding degradation the physical properties are also changed in the direction of increasing embrittlement. PVC of ideal constitution should be thermally stable, which was concluded from investigations with model substances. Therefore, it has to be assumed that the damage, articularly the dehydrochlorinations, starts from sites of the macromolecule with labile chlorinecarbon bonds. PVC can be degraded by heat and sun lights. The release of hydrogen chloride, which is the indication of PVC degradation in prolonged exposure to the suns electromagnetic radiation in the UV region, is occurred according to the following reactions:The color of PVC-based article is changed from yellow to black according to degrees of the degradation. Once the reaction has started, polymers quickly and progressively experience changes in appearance: surface qualities, gloss, chalking, color, electrical properties, tensile strength and elongation; and can reach the end points of embrittlement and total disintegration.The degradation of polymers exposed to UV, often described as photodegradation and frequently identified as photooxidation, can follow various routes. By absorbing UV radiation directly, a polymer molecule can reach a high-energy excited state where it becomes unstable. If the excess energy can be dissipated in a fashion that does not affect the molecule by making it phosphoresce or fluoresce, or by converting the energy to heat that can be carried away, or by transferring the energy to another molecule, photochemical reaction does not started and thus, polymer degradation will not happen. However, such actions occur only rarely, since most polymers cannot dispose of the excitation energy without undergoing a chemical reaction that sets off a degradative process.In theory, many pure polymers should not absorb UV radiation, and thus, not be subject to photodegradation. However, in practice the most polymers contain impurities such as carbonyl or carboxy groups or hydroperoxides that readily absorb radiation in the 290400 nm range causing them to break down. Thus, generating sites within the polymer structure where chemical reactions can be initiated and propagated by free radicals. The active groups may be unavoidably present as a result of reactions that occur during polymerization. Similarly, metallic ions are present in most polymers as residues from polymerization catalysts, or as constituents of compounding additives such as heat stabilizers, antioxidants, colorants, fillers and others. The metal ions are highly receptive to the absorption of UV radiation, and are efficient in transferring the absorbed energy to the polymer molecules around them, thus, they act as photo-sensitizers and can promote degradation at the same time that they perform their desired functions.Another contributor to photodegradation of polymers is oxygen, which helps any free radicals that may be liberated by the UV to initiate and propagate oxidation of the polymer, hence, the term photooxidation.Polyvinyl chloride suffers from poor heat stability. Its degradation occurs by autocatalytic dehydrochlorination initiated at the labile sites in the polymer chains. This leads to severe discoloration and loss of mechanical properties. The dehydrochlorination most probably proceeds by a chain mechanism involving radical intermediates. Various defect sites in PVC are branching.Inorganic and organic thermal stabilizers are commonly added to protect the polymer from heat degradation. Among the most widely used ultraviolet stabilizers is titanium dioxide pigment. Filling a polyvinyl chloride composition with this pigment substantially reduces the effective depth of penetration of ultraviolet light into the surface of an article formed from such a composition.Mohamed et al. pointed out that barbituric acid and thiobarbituric acid are nontoxic organics, thermally stable materials of high melting point. Both contain active methylene groups, and can act as H-donor through their enolic hydrogen groups, which can intervene with the radical species derived from the thermal degradation of PVC. They investigated the possibility of using barbituric acid and its thioanalogue as thermal stabilizers for rigid PVC.The effective stabilization often requires a combination of antioxidant system in which complementary overlap of different mechanistic pathways involved. This act often referred to as synergism, is the motivation for the use of admixing composition of dibutyltin maleate and trinitro and its ester homologues. The stabilization agents of dibutyltin maleate and trinitro esters could retard somewhat the photodegradation of PVC. It is hoped that the total stabilizing effect of this admixed system should be greater than the sum of the individual effects when PVC is subjected to an environment where the effects of heat and UV are combined. Turoti et al. investigated the effect of the stabilizing action of admixed mixtures of dibutyltin maleate and trinitro and its ester homologues on polyvinyl chloride exposed to natural atmosphere. In their study, the degradation and stabilization reactions were monitored by color formation, tensile strength and elongation at break, reduced viscosity as well as determination of time to embrittlement. It is observed that the stabilized PVC sample has an effective reduction in degradation reactions.Titanium dioxide is by far the most important of white inorganic pigments and possesses all-round suitability. While rutile titanium dioxide is highly reflective at visible wavelengths, it is also highly absorptive at ultraviolet wavelengths. However, although titanium dioxide is a highly effective ultraviolet light stabilizer for polyvinyl chloride compositions, it does have several serious drawbacks. An important disadvantage is the cost of titanium dioxide which has historically tended to be high compared with filler or extender pigments such as calcium carbonate and talc. Another significant disadvantage of using titanium dioxide as an ultraviolet stabilizer in unplasticized polyvinyl chloride compositions is that historically titanium dioxide has been periodically in short supply.The relatively high cost of titanium dioxide is an especially significant disadvantage for the manufacture of articles for exterior use from unplasticized polyvinyl chloride compositions because such articles must often have substantially greater dimensions, for structural reasons than the effective penetration depth of ultraviolet light in the articles. Thus, it is highly desirable to able to reduce the level of titanium dioxide in such a composition without experiencing an accompanying increase in the rate of degradation and reduction in service life. Although it seems to decrease the level of titanium dioxide in the PVC composition will tend to increase the effective penetration depth of ultraviolet length and will consequently accelerate the degradation of the PVC, the experimental observations do not support such an expectation. Since PVC compositions consist generally of from about 0.55 parts by weight of rutile titanium dioxide per hundred parts by weight of the polyvinyl chloride, there is no guarantee for the bulk of titanium dioxide to locate near the external surfaces of articles exposed to sun lights.In this study, usability of magnesium oxide with titanium dioxide in the PVC compositions for forming of the exterior articles such as door and window profile is investigated in terms of determining discoloration and some mechanical properties of the articles under accelerated weathering test.2. Materials and methodsPVC compositions widely used to form the exterior articles such as door and window profiles consist essentially of about five parts (by weight) stabilizers, five parts rutile titanium dioxide, five parts fillers, and 0.1-3 parts process aids per hundred parts by weight of the polyvinyl chloride resin.Polyvinyl chloride is subject to thermal degradation by dehydrochlorination. Since many processes for forming useful objects from polyvinyl chloride compositions, such as extrusion and molding, subject the composition to elevate temperatures, most include thermal stabilizing agents that tend to inhibit thermal degradation of the polymer during processing. Example of commonly employed thermal stabilization agents includes barium/cadmium and organotins including mercaptides, maleates and carboxylates.Polyvinyl chloride is also subject to degradation by exposure to ultraviolet light. Articles formed from polyvinyl chloride compositions, which are exposed to ultraviolet light such as vinyl siding and vinyl window and window frame components typically include an ultraviolet stabilizer.In this study, five different compositions of PVC were used to fabricate door and window profiles. These profiles are faded under accelerated weathering conditions. Discoloration and some mechanical properties of the profiles are determined to choose the most suitable polyvinyl chloride composition used to form the exterior articles.For window profiles up to nine repeated extrusion processes were investigated. The properties like impact strength, modulus, Vicat temperature, thermal stability, etc. of recycled window frame profiles from 20 to 25 years old windows are determined, it is shown that such recycled PVC is suitable for reprocessing. The heat impact of PVC bottle materials during the recycling process at 160 180 was investigated by IR- and UV-spectroscopy and by DSC. The bottle samples are slightly and considerably affected at these temperatures as shown by determination of the formed decomposition products, colour change, loss of volatile components and peroxide formation in air. However, since these decompositions occurred at about 30 min of experimental time which is about six-fold of that of real process times, the reclaimed material was found recyclable which makes the use of this material in the production of window sections, profiles, pipes and even bottles possible. Investigations on the mechanical properties of recycled PVC bottle material separated from the postconsumer waste stream show significant reduction in strength and ductility. It is believed that the main reason for this is the presence of impurities, especially PET, which although present at levels below 0.5% had a large effect on the properties. Also investigated was the degradation that occurs during multiple reprocessing of recycled PVC from post-consumer bottles using IR-analysis and molecular weight measurements. Batches of recycled flake and powder as well as pure but processed bottle flake materials were subjected to simulated multiple recycling using a torque rheometer. The results indicated a rapid degradation of the recycled material compared with purer bottle flake PVC. Multiple recycling of bottle flake mixed with 0.2% polyethylene showed that the PE impurities accelerate the degradation process. Restabilization by adding new bottle flake material surprisingly prevented degradation even at small levels of new material (30%) and even after 15 recycling steps. Recycled PVC bottle material can be used successfully in calciumzinc stabilized PVC foam formulations to produce profiles of saleable quality. Increasing amounts of bottle recyclate had no significant effect on gelation time, melt rheology or plate-out characteristic and gave rise to an improvement on thermal stability. Foam blends can be extruded to produce profiles of good surface finish and low foam density. Up to 100% PVC bottle recyclate did not affect the density, cell structure or impact properties of co-extruded foam profiles. Foamed PVC recyclate can also be used for inner layers in tubes where densities at about 0.5 g/cm3 arepossible. The reuse of recycled PVC in cable insulations is described in Ref. For this purpose, it is necessary to recover copper and PVC from cable forms originating from used motor cars. PVC can be dissolved and separated to be reused in cable and wire insulating. It is reported that cables using 100% recycled PVC have successfully passed preliminary tests. Cable forms with 50% PVC recyclate have been released for the production of new cars by several manufacturers. Since 1990 PVC floor coverings were collected and recycled in Germany. First results and practical experiences are reported in Ref. Other recycling concepts have been developed for use of recycled PVC packaging or bottle material as core in co-extruded cellular profiles. The products had satisfactory density, foam structure, colour and surface finish. Using up to 100% bottle recyclate did not affect the impact properties of the foam profile.Recycled supermarket trays actually gave an improvement in impact properties, probably due to high levels of impact modifier used in tray formulation. Also, recovery and reuse of waste PVC coated fabrics is described, extracting PVC with a selected aqueous ethyl methyl ketone solution. This so-called swelling method is a simple procedure with minimum environmental impact. The behaviour of the swelling system and the swelling properties of recovered components can be characterized by refractive index, swelling degree and the average particle size of recovered PVC. A detailed analysis of the components separated from PVC coated PET fabrics is also described. The recovered PET staple fibre scrap can directly be used to reinforce epoxides or to form a non-woven fabric on a special machine.2.1. MaterialsPVC used in the experiments was obtained from Petkim (PVC S27/R-63). The rutile titanium dioxide (Kronos 2220 TiO2) was supplied by Sayman Chemical Materials. Acrilic polymer used in the experiments as a impact modifier was obtained from LG Chemical Ltd (IM 808). TThe tin stabilizer (TIN-41) used in the study was supplied by Kimfor Chemical Ltd. The internal lubricants coded by ESKAY-4 (polyethylene oxide, compound of calcium stearate) and the external lubricants coded by WCBA (polyethylene wax) were also supplied by Kimfor Chemical Ltd. Magnesium oxide was supplied by MAGOX company.中文翻译关于混有二氧化钛的氧化镁在PVC门窗型材中的可用性研究1 简介聚氯乙烯是最广泛使用的合成有机高分子材料。增塑聚氯乙烯很常见，如乙烯基板材产品和从塑料溶胶中提取的对象。而市面上的各种聚氯乙烯中还有一些可以用于挤出具有刚性且不含增塑剂成分的产品。塑料长期暴露在阳光下，阳光中的紫外线辐射会导致其物理性能的下降，这种物理性能的下降可以通过颜色变化和脆化降解体现出来。同样，普通荧光灯的紫外线也可以降解聚合物以及聚合物中所使用的多种添加剂。地表的有效紫外线辐射波波长约为290-400纳米，对塑料降解作用最强的波长为300纳米左右的高能紫外线恰好在这个范围内。而一些人造高能量辐射源如汞弧灯、氙弧灯、碳弧灯以及各种日晒灯能发出波长低于290纳米的辐射波，这些辐射波对塑料的降解作用比自然阳光更强。因此，它们通常用于塑料的加速试验。波长为290-400纳米的紫外线所含的辐射能可以使目前聚合物中绝大多数的化学键断裂。聚合物对于紫外线辐射的抗性并不相同，如聚甲基丙烯酸酯和碳氟化合物对于紫外线辐射的抗性就比较低。另外有一些能够抗紫外线的纯聚合物则由于会吸收紫外线形成污染源而已经被淘汰。聚合物分子吸收辐射能会产生跃迁，如果吸收的能量足够多，达到化学键断裂所需要的能量，就会造成碳碳、碳氢、碳卤等内键的断裂，从而使聚合物降解。PVC的降解是脱氯化氢、自动氧化和断链等反应共同作用的结果。脱氯化氢现象在PVC的加工过程中普遍存在。在降解的过程中PVC的物理性质会发生脆化。通过实物模型得到的理想的PVC的结构应该是稳定的，这就需要假定脱氯化氢的反应是从含有不稳定氯碳键的高分子开始的。热和阳光都可以导致PVC的降解。PVC若长期暴露在阳光中的紫外线下会根据下述反应方程而释放出氯化氢：随着反应程度的加剧，PVC的颜色会逐渐由黄色变为黑色。一旦该反应开始，PVC就会迅速并逐步发生外观（如表面质量、光泽、粉化、颜色、电性能、拉伸强度和延伸率）上的变化，并最终达到完全脆化和降解。聚合物由于暴露于紫外线中而发生的降解可以按照不同的方式进行，这种降解通常被称为光降解，也经常被认定为光氧化反应。聚合物分子可以通过吸收紫外线辐射达到高能量激发态而变得不稳定。如果多余的能量通过一种不影响聚合物分子本身的方式被消耗掉，例如使它发出荧光或磷光，或者将能量转换成可以被带走的热，或将或将能量转给另一个分子，这样光化学反应就不会发生，聚合物降解也就不会发生。但是，这种方式很少发生，因为大多数的聚合物不能够不经过发生降解反应过程就消耗掉激发能量。从理论上讲，许多纯聚合物不应该吸收紫外线辐射，因此就不会产生光降解。然而，在实践中大多数聚合物，如含有羰基或羧基或氢过氧化物的聚合物，很容易吸收290-400nm范围内的辐射而导致降解。因此，化学反应可以通过自由基在聚合物结构内发生并扩大。聚合反应过程中产生活性基团是不可避免的。同样，金属离子也会作为催化剂残留物，或复合添加剂（如热稳定剂，抗氧化剂，着色剂，填料和其它助剂）的成分而出现在大多数聚合物中。金属离子极易吸收紫外线辐射，并快速将吸收的能量转移给周围的聚合物分子，因此，金属离子作为光增敏剂，同时能促进降解。另一种使聚合物产生光降解的是氧气。氧气有助于紫外线产生自由基并传播氧化作用，因此，氧气造成的光降解是长效的。聚氯乙烯热稳定性很差。其降解以自催化