氯化聚乙烯环保型添加剂的研究

主要研究了氯化聚乙烯中添加无毒、无味、无铅的配合体系,着重从无味硫化体系、无铅增稳定体系、无毒增塑体系入手调整配方,并试制出达环保标准的配方.     

ESR study of the spin labeled polyethylene crosslinking system

Summary The reactivity ratios for the radical Copolymerization of N-tert-butyl acrylamide with acrylonitrile and with methyl methacrylate were determined at 60°C.     

Effects of additives on fire properties of polyethylene

Low-density polyethylene, with and without an antimony–bromine synergistic fire retardant or aluminium hydroxide, was subjected to standard fire tests and to experiments which determined the smoke and harmful fumes emitted on overheating. Both additives improved most fire properties but the fire retardant increased the smoke generated by intense radiant heat. The onset of smoke, flammable gas, carbon monoxide and acids was generally delayed by the additives. The total amounts and maximum values of these volatiles were lessened. Sample weight and form affect the results of these experiments. Observations during heating show that the additives reduce spreading of the melt, thus reducing the surface area available for oxidation.     

Reducing the flammability of ultra-high-molecular-weight polyethylene by triphenyl phosphate additives

The thermal degradation and combustion of ultra-high-molecular-weight polyethylene (UHMWPE) doped with triphenyl phosphate (TPP) at atmospheric pressure was studied by molecular beam mass spectrometry, dynamic mass spectrometric thermal analysis, microthermocouples, thermogravimetry, gas chromatography/mass spectrometry. The kinetics of thermal degradation of pure UHMWPE and that mixed with TPP at high (≈150 K/s) and low (0.17 K/s) heating rates was investigated. The effective values of the rate constant and activation energy of the thermal degradation reaction were determined. Burning velocity and temperature profiles in UHMWPE and UHMWPE + TPP flames were measured. The composition of the combustion products in a flame zone adjacent to the burning surface of the sample was determined. TPP vapor in the flame was detected. The addition of TPP to UHMWPE was found to reduce the flammability of the polymer. It is shown that TPP acts as a fire retardant in both the condensed and gas phases.     

Effects of additives on gel-spinning of ultra-high molecular weight polyethylene

Conclusions As judged from the fibre tensile strength-extrudate draw speed relationship for UHMWPE solutions in paraffin oil, carbon black particles diminish flow instabilities and extrudate irregularities as does EPDM rubber. Reductions in fibre tensile strength by both additives is caused by their weakening the fibre structure.Increasing the shear rate at the wall by using a more abrupt die geometry lowers drastically the mechanical properties of the fibres.     

Accelerated photo-oxidation of polyethylene. I. Screening of degradation-sensitizing additives

Numerous simple compounds have been shown to be capable of accelerating the photo-oxidation of polyethylene upon exposure to wavelengths near 300 nanometers. Probable mechanisms of photo-initiation by the principal classes of degradation-promoting additives are discussed.     

Mechanical and friction properties of glass-filled thermoplastics modified by polyethylene additives

Temperature and concentration dependences of elasticity modulus, wear and wearability of industrial glass-filled thermoplastics modified by low-density polyethylene were studied. It is shown that polyethylene additive reduces the elasticity modulus in the solid aggregate state of polymer matrix and enhances it in the softening region. For the first time a possibility was found to reduce friction, wear, and wearability of glass-filled thermoplastic materials by incorporating optimum amount of alloying polymer additive thermodynamically incompatible with the polymer matrix.     

Effect of filler content and additives on the extrudate swell of polyethylene pipe resin

In certain extrusion operations, particularly the production of plastic pressure pipe, it would be desirable to be able to control the degree and direction of molecular orientation. While dies can be designed to generate various types of orientation, most of this is lost at the die exit due to extrudate swell. It is known that substantial loadings of nonreinforcing filler can inhibit swell, and the objective of this study was to examine the effects of particle size and loading and of the use of coupling agents on extrudatee swell of CaCO₃-filled medium-density polyethylene pipe resin. Swell was measured as a function of time by extruding into oil having the same density and temperature as the extrudate. In addition, the storage and loss moduli of all samples were measured, and, the relaxation spectra were calculated. The maximum degree of swell suppression was observed for a compound containing 30 wt. percent of 0.4 micron particles treated with stearic acid. Surprisingly, the use of coupling agent increased the degree of swell.     

Accelerated photo-oxidation of polyethylene. II. Further evaluation of selected additives

A number of additives previously observed to promote photo-oxidative degradation of polyethylene films have been evaluated with respect to their relative photoinitiating effectiveness at wavelengths near 300 nm and their effects on thermal-oxidative stability of polyethylene. Depending on the nature of the additive, the photo-oxidation process may display autoretarding or autoaccelerating behavior. Thermomechanical analyses and gel content measurements on UV-exposed films containing substituted anthraquinones suggest that at short exposure times, photo-oxidative degradation is accompanied by photochemical crosslinking.     

Effect of antistatic additives on mechanical and electrical properties of polyethylene foams

Polyethylene foams with different antistatic additives (Atmer 7325, Atmer 7105, and Atmer 190) were prepared by extrusion and stored during 6 months of time span in a real life environment. The antistatic performance was evaluated by measuring the surface resistivity and throughout decay‐time experiments. Mechanical properties and migration tests were also performed. It was found that the migration of antistatic agents is in general low enough, which allows to maintain the antistatic performance for periods of time larger than 6 months. The tests revealed that the desired low surface resistance and required low static decay time could be achieved with all the antistatic agents under test. Moreover, the additives with amina (Atmer 7105 and 7325) as an active agent showed slightly better antistatic performance than the one with the ionic agent (Atmer 190). The addition of an antistatic agent does not significantly affect the mechanical behavior of the foam indicating a desired feature concerning industrial applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

A study of brittle-ductile transition in polyethylene

The brittle-ductile transition temperatures (BDTT) of polyethylenes with different degrees of crystallinity, such as LDPE, LLDPE, MDPE, and HDPE, were evaluated using Charpy impact test. The effect of the specimen cooling condition on the BDTT was a main concern in the study. A rise in the cooling plate temperature (Tp) for high density resins brought about a fall in BDTT and an increase in the Charpy impact value Et. However, embrittlement was observed during a tensile test for HDPE samples with a rise in Tp. A crack shielding effect by microvoid formation is proposed as the toughening mechanism for HDPE.     

Effect of different additives on the cloud point of a polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer in aqueous solution

Cloud point studies on aqueous solutions of a polyethylene oxide (PEO)-polypropylene oxide-PEO triblock copolymer (Pluronic^® L64: EO₁₃PO₃₀EO₁₃, total m.w.=2900, PEO=40%; EO=ethylene oxide; PO=propylene oxide) in the presence of different additives show some interesting features. The effect of various inorganic salts was an increase or decrease in cloud point based on their salting in and salting out action and followed the Hofmeister lyotropic series. Nonelectrolytes and hydrotropes increased the cloud point by influencing water structure. Hydrotropes altered the cloud point of the copolymer at much lower concentrations than inorganic salts. Ionic surfactants produced a marked increase in the cloud point of copolymer solutions. The effect was greater for surfactants with greater hydrophobicity. Alcohols and other organic liquid additives that are infinitely miscible with water increase the cloud point of the copolymer, whereas additives that are partially miscible in water decrease the cloud point.     

磷酸蒸发浓缩助剂的实验研究

实验研究各种表面活性剂作为磷酸浓缩蒸发的助剂,用以提高水的蒸发强度,加入量只需磷酸质量的200×10-6,以TWEEN+NNO和TWEEN+GC效果较好。同时实验研究了各种阻垢剂,其中以SO-3和十二烷基苯磺酸钠最佳,对氟硅酸钾(钠)的阻垢率可达60%以上。湿法磷酸浓缩过程中同时加入上述表面活性剂,可提高蒸发强度,减少蒸汽用量,提高浓缩酸浓度,并有一定的阻垢作用。     

助剂对滚塑专用茂金属聚乙烯树脂MPE6性能的影响

研究了抗氧剂和紫外光吸收剂用量对滚塑专用茂金属聚乙烯(PE)树脂MPE6老化性能的影响;探讨了MPE6的滚塑加工性能,并与进口滚塑专用茂金属PE树脂PE1及用Ziegler-Natta催化剂生产的进口滚塑专用PE树脂PE2进行了对比。结果表明:MPE6的加工流动性和滚塑设备适应性好,且其滚塑制品的基本性能与用PE1生产的制品相当,常温简支梁缺口冲击强度和高处跌落性能优于用PE2生产的制品。