Extrusion-rotomolding of plasticized PVC formulations

In this work, we present a novel process to produce plasticized PVC articles. Plasticized PVC dispersion resin (dry blend) was extruded and poured into a hot mold. The mold was transferred to a rotomolding machine, where the final geometry was obtained. Formulations using commercial PVC suspension resin and three different types of plasticizers were prepared under different processing conditions. The physical appearance of the articles and the tensile properties of the materials were evaluated.     

Time temperature equivalence in plasticized PVC

The viscoelastic response of plasticized PVC was determined from stress-relaxation data over a wide range of time at different temperatures. The relaxation modulus as a function of time was determined from these data. The relaxation curves were then shifted horizontally to obtain a master curve at a reference temperature. The amount of shift was evaluated using the WLF equation. The coefficients C and C used in the equation for the PVC were determined according to the method of reduced variables.     

Antioxidant effects in PVC plasticized with DIDA

Antioxidants such as bisphenol A (BPA) have long been recommended for retention of physical properties on oven-aging of PVC plasticized with certain plasticizers. We have shown how BPA inhibits oxidative fragmentation of plasticizers such as diisodecyl adipate (DIDA) and thus decreases apparent volatility, and how it improves retention of modulus, elongation, and low temperature flexibility. Low concentrations are more beneficial than either zero or high concentrations, especially on longer aging. At higher concentrations, although the plasticizer is retained in the PVC, it becomes less efficient at low temperature, and low-temperature flex is impaired while elongation is preserved. DIDA exudes during oven-aging unless oxidation occurs to prevent it. When BPA is present, exudation is worst at the most efficient concentrations of antioxidant. This appears to be the normal incompatibility of DIDA at 105°C which is permitted by the antioxidant. On oxidation, the dielectric constant of DIDA rises into the 4–8 range, signifying compatibility with PVC, and the DIDA does not exude.     

Crosslinking studies in plasticized epoxies by means of dynamic measurements

A class of amine-cured epoxy resins containing various amounts of polysulfide plasticizer were subjected to dynamic testing during curing at high temperature. Both E modulus and loss factor were determined simultaneously. It was proved that the method allowed for rapid determination of the general pattern of the crosslinking procedure and the necessary curing time and, in general, that dynamic methods are most suitable for the mechanical characterization of polymers under curing at each stage of the curing cycle.     

The dc volume resistivity of plasticized PVC

A study has been made of the dc volume resistivity of plasticized PVC using a guarded-electrode system in a sensitive vibrating capacitor–electrometer circuit. Transient effects were found to be pronounced in all but the least plasticized compositions, and the behavior in general was non-Ohmic. The resistivity decreases with plasticizer concentration and with temperature; an Arrhenius-type relationship is observed and resistivity undergoes an inflection at the glass transition temperature. The mechanism of conduction appears to be electrolytic rather than charge injection or semiconduction.     

Crosslinking of PVC and NBR blends

The purpose of our work is to control the interfacial bonds between PVC and NBR using the ammonium salts of triazine thiols and dithiodimorpholine (DTDM) and thereby reveal the relation between the interfacial bonds and the final mechanical properties of products. In the experimental work a two-stage process was used. At first, an NBR/PVC blend was mixed with a mono-tetra-n-butylammonium salt of triazine trithiol at a temperature of 100°C on a two-roll mill to give the branching structure of triazine thiols into PVC. In the second stage branched NBR/PVC reacted with DTDM to afford the branched PVC containing trithiomorphonyl groups. In the presence of ZnO at 160°C trithiomorphonyl groups react with NBR to form a crosslinking structure between NBR and PVC. The mechanical properties of cured NBR/PVC blends were markedly improved by the treatment process and after addition of tetramethylthiuram monosulphide also. The mechanical properties were not improved by increasing the concentration of TT-TBA (tetrabutylammonium salt of 1,3,5-triazine-2,4,6-trithiol) over 4.2 phr.     

Rates of property change in plasticized filled PVC compounds

Rheological and mechanical properties of polyvinyl chloride (PVC) compounds vary with the polymer entanglement state at the time of testing. Controlled shearing episodes and thermal histories applied to the compounds produce major property variations. These then relax toward steady-state values at rates which are consistent with diffusion-controlled processes, presumably connected with the development of steady-states in entanglement couplings. Activation energies of 4–7 kcal/mol apply to the proposed re-entanglement processes. Rates of property variation can be altered by the addition of fillers to the compounds, the interactions between polymer and filler being an important factor in this regard. CaCO₃ samples with strong affinity for the PVC retard the rate of property variations (i.e., the filler tends to stabilize non-steady-state entanglement couplings). Fillers, surface treated so as not to interact strongly with the polymer, produce lesser effects on relaxation rates. The data indicate the feasibility of controlling both the sensitivity of polymer properties to processing variables, and the rates of property change associated with the attainment of steady-state polymer entanglement morphologies.     

Leaching of plasticized PVC: Effect of irradiation

Highly irradiated (2–26 MGy) polyvinyl chloride (PVC) was leached in an alkaline solution to investigate the impact of high doses on the leaching process and on the nature of the leaching products. The results show that leaching is controlled by diffusion phenomena as described by Fick's second law. The apparent diffusion coefficient (D_a) of plasticized PVC leaching products can be calculated for each sample. Irradiation at high dose causes D_a to diminish; this can be attributed to crosslinking and grafting reactions occurring during irradiation. The material microstructure thus becomes less permeable during radiolysis, which slows down the migration of species. Organic products of leaching are plasticizers contained in plasticized PVC or their degradation products. The main organic leaching products are phthalic ions formed by the hydrolysis of phthalic esters in alkaline leaching solution. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Crosslinking and scission in thermooxidative degradation of PVC

Summary Crosslinking and chain scission in thermooxidative PVC degradation have been studied. Gel formation was found to give linear Charlesby-Pinner plots, consistent with the constant rate of crosslinking and scission. Similarly to thermal degradation, partial reversibility of crosslinking was observed also in oxygen.     

软质PVC电缆料的辐射交联

以三甲氧基丙烷三甲基丙烯酸酯（ＴＭＰＴＭＡ） 为交联剂,以Ｃｏ６０γ射线为辐照源,研究了偏苯三酸三辛酯（ＴＯＴＭ） 增塑的ＰＶＣ电缆料的辐射交联。结果表明该辐射交联反应符合ＣｈａｒｌｅｓｂｙＰｉｎｎｅｒ 无规交联模型,ＴＭＰＴＭＡ１０ 分,辐照剂量４０ｋＧｙ 是较合适的配方与工艺条件,该材料经辐射交联后拉伸强度增加 ,断裂伸长率下降,１５５ ℃的热老化失重与１２０ ℃热变形率减小。     

Photocrosslinking of azidated poly(vinyl chloride) coated onto plasticized PVC surface: Route to containing plasticizer migration

The migration of phthalate esters which are commonly employed for plasticizing poly(vinyl chloride) (PVC) is a significant problem in PVC-based medical devices as well as in packaging used for food stuffs and pharmaceuticals. Medical-grade PVC resin was treated with sodium azide in dimethylformamide (DMF) to prepare the azide polymer. The polymeric azide was coated onto the surface of plasticized PVC sheets by dipping in a solution of the polymer in tetrahydrofuran (THF). Crosslinking of the azide polymer was accomplished by irradiating the surface using a 125 W UV lamp for various lengths of time. Migration of the plasticizer di 2-(ethylhexyl phthalate) (DEHP) from coated and uncoated samples was examined in n-hexane at 30°C. It was found that 50–80% reduction in migration of DEHP could be effected from plasticized PVC in comparison with the controls in 72 h by this technique depending on the concentration of the coating solution, coating thickness, azide concentration, and irradiation dose. © 1995 John Wiley & Sons, Inc.     

The biodeterioration of plasticized PVC and its prevention

Plasticized polyvinyl chloride will be attacked by microorganisms. The microorganisms will use the plasticizer as a carbon source, whereas favorable growth conditions, like water and oxygen, promotes their growth. A clear effect of the temperature of the water used in leaching experiments on the rate of fungal growth on the foil surface could be demonstrated. Studies also showed a difference in susceptibility of several types of plasticizers to fungal attack. The plasticizers can be divided into several classes based on their susceptibility to fungal attack. Detailed studies on the microbiological population on foil surfaces showed the predominating position of fungi. This indicated a metabiotic system between fungi and bacteria on foil surface. Addition of biocides, during manufacturing of PVC, primarily must have fungistatic properties. The fungistatic activity of 10,10′-oxybisphenoxyarsine (OBPA) is very high, and in consequence, very low concentration must be available on foil surfaces which will prevent fungal growth. These low amounts on foil surfaces are directly correlated to the amount of OBPA insite of the foil. The transport process of the insite OBPA to the surface of the foil will principally be determined by the recepe of the foil. Therefore the application concentration recommended to ensure to achieve the minimum inhibitory concentration for fungi on the foil surface will be determined from where the application actually manifests itself.     

PVC塑化木粉及其吸水性

将木粉和PVC共混，同时加入相容剂POE—MAH，三者经挤出机挤出形成化学反应相容。生成PVC塑化木粉。研究了该塑化木粉的吸水性。研究表明：体系中PVC比例增加、木粉比例减小时。临界含水量变小，即吸水性变小。     

Stress-cracking resistance of polycarbonate in contact with plasticized PVC compounds

Polymeric polyester plasticizers cause less cracking in polycarbonate than monomeric esters. Certain high-viscosity polymeric plasticizers over 100,000 centipoise, and several in the 10,000 to 25,000 range, did not stress-crack polycarbonate. But viscosity is not the only determinant. Chemical type, level of use, polarity, and severity of the environment all contribute to crack development in stressed polycarbonate.     

亚乙基硫脲对PVC和PVC/ENR共混物的交联作用

从交联速率、压缩永久变形、凝胶质量分数、强伸性能和耐热性能等方面考察了亚乙基硫脲（ＥＴＵ）和ＥＴＵ／硫黄对ＰＶＣ及其与环氧化天然橡胶（ＥＮＲ）共混物的交联作用。结果表明,ＥＴＵ和ＥＴＵ／硫黄对ＰＶＣ及其与ＥＮＲ的共混物有明显的交联作用;交联后共混物的物理性能和耐热性能均有较大提高;适当增大ＥＮＲ用量,有利于提高共混物的热变形性能;ＰＶＣ／ＥＮＲ的共混比为７０／３０时,硫黄的最佳用量为１５份,促进剂选择促进剂ＤＭ／ＴＭＴＤ体系为佳。     

环境友好型增塑剂增塑聚氯乙烯体系的性能表征

以传统增塑剂邻苯二甲酸二辛酯(DOP)为比较对象,研究了对苯二酸二辛酯(DOTP)、乙酰柠檬酸三丁酯(ATBC)、己二酸二辛酯(DOA)、癸二酸二辛酯(DOS)4种环境友好型增塑剂对聚氯乙烯(PVC)体系的力学性能和耐油、耐溶剂性能的影响,并采用傅里叶变换红外光谱法和差示扫描量热法对试样分子结构进行了表征。结果表明:①ATBC/PVC体系的Tg最高(-22.1℃);DOS/PVC体系的Tg最低(-65.4℃),耐寒性最佳;②ATBC、DOA、DOS增塑PVC的力学性能整体上优于DOP增塑的PVC;③在异辛烷、正己烷和ASTM 1#标准油3种萃取剂中,5种增塑剂在正己烷中的最终抽出率最大;在同一萃取剂中,ATBC的最终抽出率最小;④针对不同使用领域,DOPT、ATBC、DOA、DOS可替代DOP增塑PVC。     

Colorimetric analysis of black coated fabrics

In this article, two visual evaluation methods, i.e., the rank-ordering and pair comparison techniques, are sequentially used to investigate the effect of hue, lightness, and chroma values on the preference of blackness of 216 black coated fabrics. Based on the colorimetric attributes of specimens, the blackness preference of samples is assessed by 18 amateur observers through different predesigned experiments. Results show that while the lightness of samples performs a very important role in the blackness preference, it does not individually influence the results, and irrespective of the effect of chroma, observers perceive bluish-cyanish black fabrics as the preferred black samples. However, the specialized functionality of lightness is evident for black coated fabrics with very close hue and chroma attributes, and the blackness preference of samples increases when lightness is decreased. Finally, the validity of some suggested blackness indices is evaluated with comparison to the visual results.     

Crosslinking of PVC formulations treated with UV light

Typical wire and cable formulations of plasticized Poly(vinyl chloride) were prepared with three different stabilizer systems: Ca/Zn (2:1 or 1:1) and dibasic lead phthalate. The mixtures contained trimethylolpropane trimethacrylate (TMPTMA) as crosslinking agent and a UV photoinitiator (Irgacure 819). Mixtures were dry‐blended, then roll‐milled and to finally hot‐pressed at 180°C to obtain sheets of 1 and 1.5 mm thickness. Small specimens (3 × 3 cm) were irradiated with UV light for up to 10 days while monitoring changes at different time intervals. The presence of TMPTMA in the samples, as expected, influenced the storage modulus (E′) and gel content percentage, specifically for the thinner samples. These results indicated that UV irradiation produced surface crosslinking. The samples with crosslinking agent also reached higher carbonyl index values. The Ca/Zn formulations showed higher mechanical properties with respect to the Pb ones, thus suggesting that during the stabilization period of the Ca/Zn mixtures, an effective crosslinking was promoted. Irregular behavior was observed during the last days of treatment for both types of formulations, thereby suggesting an optimum irradiation time for this procedure. J. VINYL. ADDIT. TECHNOL. 12:49–54, 2006. © 2006 Society of Plastics Engineers.     

聚氯乙烯化学交联方法的研究

从机理、工艺条件、分子结构和性能等几个方面对聚氯乙烯的化学交联方法进行了较深入的探讨,并对交联实施过程中可能发生的副反应及其控制进行了讨论