Dimensional stability of oriented,rigid poly(vinyl chloride)

Oriented PVC has enhanced properties, but on heating it begins to shrink and eventually reverts to its original dimensions. Thermomechanical analysis was used to study the effects of orientation variables and subsequent annealing or aging on the shrinkage of rigid PVC. The thermal history of the oriented PVC affected its crystallinity and the free volume in the oriented structure. These changes modified the temperature at which the oriented samples began to shrink (i.e., their dimensional stability.) Higher draw and annealing temperatures can be used to improve dimensional stability; however, their effective use is limited because PVC has a peak elongation at 90°C. Increased annealing time also increases dimensional stability. Aging greatly improves the dimensional stability of the material; this process can be accelerated at temperatures up to 60°C. The shrinkage onset temperature can be increased without compromising the enhancement of mechanical properties achieved by orientation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3859–3867, 2003     

Synergistic effect of metal soaps and natural zeolite on poly(vinyl chloride) thermal stability

The synergistic effect of metal soaps (zinc stearate and calcium stearate) and/or natural zeolite (clinoptilolite) on PVC thermal stability was investigated. For this purpose, PVC plastisol was prepared by mixing poly(vinyl chloride) (PVC) and dioctyl phthalate (DOP) and stabilized with different amounts of metal soaps and zeolite. Kinetic studies of dehydrochlorination at 140 and 160°C were done for unstabilized and stabilized PVC plastigels using 763 PVC Thermomat equipment. The stabilizing effect of zeolite on the increase in the induction period of the sample was considered to result from the absorption of HCl, a property that was thought to reduce the autocatalytic effect of HCl evolved at the initial stages of dehydrochlorination. Since the induction time of the sample having 0.53% of zinc stearate and 0.53% of zeolite was higher than those of the PVC plastigels having only zinc stearate or zeolite, the synergistic effect on thermal stability was observed at low levels of these additives. J. VINYL. ADDIT. TECHNOL., 11:47–56, 2005. © 2005 Society of Plastics Engineers     

Environmental concerns with vinyl medical devices

More and more jurisdictions generate increasingly strict air quality regulations that, almost without exception, include limitations on vinyl chloride. Processors frequently express concerns about their ability to meet environmental and occupational safety VCM limits. To address these concerns, the paper traces residual VCM levels through various stages of conversion from raw PVC resin to finished product storage. Another environmental concern often raised involves the reusability of molded or extruded vinyl devices. While plant regrind is routinely fed back into virgin production and its effect on physical properties is well known, solid waste management considerations increasingly involve postsale reuse of devices, an area not well explored. This paper looks at the reprocessing following long-time storage of devices, not only on physical performance but also on thermal and radiolytic (gamma sterilization) stability.     

Radiation sterilization compatibility of medical packaging materials

We have examined gamma sterilization compatibility for many of medical packaging materials. Techniques used include thermal analysis, physical testing, optical property evaluations, and failure analysis. For a variety of PVC formulations, gamma radiation often leads to discoloration. This results from conjugated poly-ene sequences formed through dehydrohalogenation degradation during ionizing radiation. In addition to unacceptable color formation, excessive pH shifts and high extractables are often observed. For most polylefins, radiations was found to deplete the antioxidant package and lead to discoloration and/or mechanical failures. For polypropylenes, the degradation can lead to the well-publicized catastrophic failures during post radiation shelf life storage. These examples and methods to ensure radiation compatibility and shelf-life stability are presented.     

Enhanced flame retardancy and thermal stability of zinc borate and magnesium carbonate as a promising alternative for Sb2O3 toward polyvinyl chloride

Inorganic zinc compounds such as zinc carbonate (ZC) and zinc borate (ZB) are considered as promising alternatives for harmful antimony trioxide in the future, but may result in poor thermal stability for flexible polyvinyl chloride (PVC). To enhance the flame retardancy and static thermal stability of flexible PVC, zinc compounds with environmentally friendly magnesium carbonate (MC) were introduced into PVC matrix. Findings reveal that the simultaneous use of 5 phr ZB and 5 phr MC for flexible PVC exhibits satisfactory properties containing pronounced flame retardancy with a limiting oxygen index of 30.2% and a UL-94 V-0 rating without dripping, enhanced static thermal stability with high color stability by discoloration tests, reduced smoke emission, and decent mechanical properties, which are advantageous over the standalone use of ZC, ZB, and MC. The enhancement mainly due to that the incorporation of ZB can accelerate the dehydrochlorination and promote the charring of flexible PVC in the early stage of flame burning, and MC can perform the long-term static thermal stability due to the HCl absorption capacity.     

Unique antimicrobial/thermally conductive polymer composites for use in medical electronic devices

The common neglect of the prominent bacterial growth and accumulation on polymer-based thermal conductive materials used in medical electronic devices will hurt the functionality and lifetime of medical devices, and sometimes even lead to medical accidents. In this study, we developed a novel ternary composite with excellent antimicrobial and thermal conductive properties to solve this problem. This composite was composed of antimicrobial functionalized hexagonal boron nitride (AB@h-BN) nanoplatelets, low melt alloys (LMAs), and epoxy. Antimicrobial testing showed that the AB@h-BN/LMAs/epoxy composites were 100% against both Escherichia coli and Staphylococcus aureus; their antibacterial mechanism was contact killing and was harmless to the environment. Besides enhancing the antimicrobial property, the AB@h-BN nanoplatelets connected the mutually independent LMAs, forming the continuous network for heat conduction in the epoxy. Benefited from this distinctive structure, the thermal conductivity of AB@h-BN/LMAs/epoxy can reach 2.66 Wm⁻¹ k⁻¹, which represented an enhancement of about 1141% over the pure epoxy.     

氧化铈复合热稳定剂

采用煅烧碳酸铈的方法制备氧化铈,将其单独用作热稳定剂,并与三碱式硫酸铅、硬脂酸钙二元或三元复配,应用刚果红法考察其对PVC热稳定性的影响.研究结果表明:单一氧化铈具有一定的热稳定作用,这主要是由于稀土可与多个氯原子配住,使PVC中的C-Cl稳定,从而提高了PVC的热稳定性;氧化铈(0.67%)+硬脂酸钙(1%)+三碱式硫酸铅(0.33%)三元复配效果最好,PVC热降解温度为206℃,热稳定时间为1 450 s.     

对甲基苯甲酸铈对PVC热稳定性能的影响

用复分解法制备了对甲基苯甲酸铈,确定产物的分子式为Ce（C₈H₇O₂）₃·2H₂O。研究了对甲基苯甲酸铈对聚氯乙烯（PVC）的热稳定性能的影响。结果表明,对甲基苯甲酸铈单独作为PVC热稳定剂时,其热稳定性和抗变色性都不强。将对甲基苯甲酸铈与其他热稳定剂联合进行二元、三元及四元复配,产物的协同作用良好,热稳定性有所提升;当复合稳定剂按对甲基苯甲酸铈∶钙锌复合体系∶季戊四醇=2∶1∶2的比例添加到PVC中,PVC样品的热稳定时间和抗变色性能最好,热稳定时间为42 min;对甲基苯甲酸铈的塑化能力良好,对甲基苯甲酸铈作为热稳定剂加入PVC后,PVC混料的塑化时间缩短,动态热稳定时间增加,塑化扭矩和平衡扭矩下降;对甲基苯甲酸铈与PVC降解过程中产生的HCl反应而生成CeCl₃,降低了HCl对PVC降解的催化作用,从而达到增强PVC热稳定性能的目的。     

二元羧酸有机锡对聚氯乙烯的热稳定作用——性能递变规律与机理

用烘箱变色法测试了几种二元羧酸二烷基锡对聚氯乙烯（PVC）的热稳定作用。结果表明,其热稳定性能随分子中羧酸根羰基C原子正电性的增强而提高;如果分子中含有亲双烯结构单元,则其所稳定的PVC试片在最终黑化前呈现较轻的着色;二元羧酸二烷基锡是通过其带正电荷的羧酸根羰基C原子和（或）二烷基锡离子作为亲电中心与PVC发生亲电反应（简称亲电反应机理）对PVC产生热稳定作用;而如果分子中含有亲双烯结构单元,则同时以亲电反应和Diels-Alder反应机理发挥热稳定作用,但前者为主而后者为辅。     

Thermal stability and chemical durability of PVC‐based biomedical devices

Poly(vinyl chloride) (PVC)‐based blood circuits for extracorporeal hemodialysis were investigated for the assessment of their thermal stability as well as their chemical durability towards ionizing radiation sterilization and environmental conditions of storage and transportation. Thermal degradation was monitored by measuring the amount of hydrochloric acid (HCl) evolved as a function of different thermal stresses. HCl was extracted from the internal lumen of the blood circuits, and then quantitatively evaluated under the corresponding form of chloride ions by chromatographic technique (HPLC‐IC). Behavior of PVC heat stabilizers was evaluated as well, determining also the concentration of calcium and zinc released by the investigated materials, by flame atomic absorption spectroscopy (FAAS) technique. Electron beam irradiation revealed an impact on blood tubing higher than that of environmental storage conditions. Nevertheless, real operative cases of sterilization and storage conditions turned out to be quite safe, and all blood circuits displayed good performances in terms of thermal stability. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5378–5387, 2006     

亚磷酸酯和季戊四醇对聚氯乙烯热稳定作用的研究

通过热老化法、白度测试、电导法及热重分析法,研究并对比了亚磷酸-苯二异辛酯(PDOP)和季戊四醇(PER)作为辅助稳定剂对PVC的热稳定作用。结果表明:PDOP能有效抑制锌烧,当PDOP/Zn比例为4:2时抑制效果最好;硬脂酸钙与硬脂酸锌存在协同效应,最佳Ca/Zn配比是2:1;三元热稳定剂的热稳定效果明显好于二元热稳定剂,且PDOP与Ca/Zn较PER与Ca/Zn有更优良的协同效应,PER/Ca/Zn体系在加热25min时出现泛黄现象P,DOP/Ca/Zn体系在加热45min时仍保持较高白度;证明PER有吸收氯化氢的作用。     

Weatherable rigid PVC: The effect of light and thermal stabilizers

Rigid PVC compositions used in outdoor applications such as siding, profiles, windows, and soffit predominantly contain a tin mercaptide thermal stabilizer. It is well known that tin mercaptides impart outstanding thermal stability to vinyl compounds, however, it is also well known that they provide only marginal light stability. Mercaptides can be used in these applications primarily because they are combined with high levels of titanium dioxide. They are not well suited for dark colored PVC and compositions without titanium dioxide. These require a more weatherable thermal stabilizer, such as a tin carboxylate. In this paper, principles for formulating rigid weatherable vinyl will be discussed. The influence of thermal stabilizers and the interdependence of light stabilizers and thermal stabilizers on PVC photostability will be emphasized. Data will be presented showing how one can formulate weatherable dark brown and pastel PVC through the use of tin carboxylate thermal stabilizers, the appropriate light stabilizers, and pigments. Traditional approaches to achieving weatherability will be compared to what can be attained by capitalizing on the latest advances in stabilization technology. Finally, methods for reducing TiO₂ concentration will be shown.     

Stability of a-C:H:SiOx coating on polypropylene to chemical sterilization

Polypropylene (PP) is traditionally used in the production of medical devices, such as catheters, dialyzers, syringes due to its good chemical and thermal resistance, biocompatibility, and low cost. Sterilization can however damage these devices, when the polymer additive releases into physiological fluids, thereby harming the patient health. This article proposes to deposit biocompatible a-C:H:SiO_x coatings onto PP surfaces and studies the coating stability after chemical sterilization. Five different chemical sterilizers, namely, hydrogen peroxide, ethanol, miramistin, formaldehyde, and ethylene oxide are used to compare their effect on the coating stability on the PP substrate. Untreated and sterilized samples are incubated in a liquid synthetic nutrient to obtain extracts that are used for sterility testing and determining the degree of interaction of samples with the nutrient medium. The changes in the coating functional groups and surface morphology are examined by using the Fourier transform infrared spectroscopy and the scanning electron microscopy, respectively. It is shown that the a-C:H:SiO_x coating has a protective effect on the PP substrates subjected to chemical sterilization. The experiment results clearly showed that the ethanol sterilization causes the most serious changes in the structure of PP, and also leads to the barrier coating failure. On the other hand, ethylene oxide sterilization has a minimal effect on the structure of both uncoated and coated PP substrates.     

Insights into the use of zinc–mannitol alkoxide as a novel thermal stabilizer for rigid poly(vinyl chloride)

Zinc–mannitol alkoxide (Zn–Man) was synthesized through alcohol exchange reaction, and investigated by means of Fourier transform infrared spectroscopy and elemental analysis. The thermal stability of Zn–Man for rigid poly(vinyl chloride) (PVC) was evaluated by Congo red testing, conductivity measurements, thermal aging testing, thermogravimetric analysis (TGA), and ultraviolet–visible (UV–vis) spectroscopy test. The experimental results demonstrate that the addition of Zn–Man not only apparently prolonged the static thermal stability time to approximately 96.5 min but also evidently improved the initial color of PVC. More importantly, the color of the PVC sheets stabilized with Zn–Man did not change to black within 180 min; this showed that no zinc‐burning phenomenon occurred. In addition, the results of TGA reveal that Zn–Man raised the initial degradation temperature of PVC to about 273.4°C. UV–vis testing indicated that the presence of Zn–Man decreased the content and shortened the length of the conjugated double bonds of PVC. The possible thermal stability mechanism is discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42038.     

聚氯乙烯热稳定性测试方法的研究

热稳定性是影响聚氯乙烯(PVC)加工和使用的重要性能之一,PVC热稳定测试方法的研究对PVC热稳定剂的研发起到至关重要的作用.从介绍PVC的降解机理入手,系统介绍和论述了白度法、变色法、刚果红法和电导法等聚氯乙烯稳定性能的测试方法,指出了不同测试方法的优缺点与适用范围.这些方法都以高温下聚氯乙烯降解释放HC l并生成共轭双键导致其颜色变化这一降解机理为依据来测试其稳定性.     

Stabilization of poly(vinyl chloride). VIII. Synergisms between epoxy compounds and metal soaps

Effects of bisphenol A type epoxy compounds involving various average molecular weights on the zinc stearate/calcium stearate and the cadmium stearate/barium stearate synergetic soaps induced thermal stabilization of poly(vinyl chloride) (PVC) were investigated by colorimetry. The remarkable stabilization effects of epoxides could not be observed on the PVC films without synergetic soaps, while the stabilization of PVC was markedly enhanced by combined use of epoxides and synergetic soaps. The appearance of excessive coloration of cool color producing metal chloride–polyene complexes which were an origin of abrupt discoloration of stabilized PVC was retarded by using epoxides together with synergetic soaps. Moreover, as for PVC with or without synergetic soaps, the epoxy compounds did not inhibit the formation of longer polyene chains which were a chromophore for yellow orange of aged PVC. Further colorimetries and IR or X-ray photoelectron spectroscopies on the various PVC containing epoxy compounds and zinc chloride indicated that the epoxy groups caught the zinc chloride. The synergetic effect between epoxy compounds and synergetic metal soaps is ascribed to the action that the epoxides serve as an acceptor for the excessive cool color producing metal chloride produced from zinc stearate and cadmium stearate to retard the abrupt discoloration of stabilized PVC.     

SiC nanograins stabilized Si–C–B–N fibers with ultrahigh-temperature resistance

Continuous ceramic fibers with ultrahigh-temperature stability are in high demand for applications in advanced space propulsion and thermal protection systems. In this study, SiC nanograins stabilized Si–C–B–N ceramic fibers were prepared using chemically modified polyborosilazane via a polymer-derived method. The fabricated Si–C–B–N fibers exhibited a rather high tensile strength of approximately 1.8 GPa and a high strength retention of approximately 90% after annealing at 2100°C for 0.5 h under a nitrogen atmosphere. The ultrahigh-temperature stability can be contributed to the presence of thermodynamically stable SiC nanograins and the encapsulation of SiC nanograins by the BN(C) phase and amorphous Si–C–B–N matrix. Our work offers a convenient strategy for preparing Si-based ceramic fibers with ultrahigh-temperature stability at beyond 2000°C.     

Tensile properties,thermal stability,and the mechanism of PVC stabilized with zinc and calcium oxolinic complexes

Two novel thermal stabilizers, zinc and calcium oxolinic complexes (Zn(Oxo)₂ and Ca(Oxo)₂), with superior tensile properties and notable thermal stability effect for polyvinyl chloride (PVC) are reported here. The complexes are synthesized without any organic solvents, and the structures are confirmed as Zn(C₁₃H₁₀NO₅)₂·H₂O and Ca(C₁₃H₁₀NO₅)₂·3H₂O by Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray fluorescence spectrometry, and elemental analysis. The PVC samples stabilized with the complexes show superior tensile strength and elongation at break compared with zinc and calcium stearates by tensile test. The results of Congo red test, dehydrochlorination test, and discoloration test show that: (1) Zn(Oxo)₂ is better than zinc stearate as thermal stabilizer for PVC; (2) Zn(Oxo)₂ and Ca(Oxo)₂ show notable synergistic effect with calcium stearate and zinc norfloxacin respectively. The mechanism of the superior tensile properties and notable thermal stability effect is due to the ability of the complexes to absorbing HCl and reacting with PVC chains, which result in the special chain extension of PVC and the delay of autocatalytic effect and zipper-like dehydrochlorination. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47004.     

RF welding of PVC and other thermoplastic compounds

Many of the acclaimed advances in medical sciences have been possible because of the improvements in material sciences, particularly plastic. Radio frequency (RF) sealing of plastics has adopted an increasingly important role as a means of manufacturing medical devices. A high intensity radio signal is used to impart increased molecular vibration in two similar or dissimilar polymers. RF sealing is one of the methods for fabrication that allows the designer to seal or connect different types of plastics. This study addresses the effectiveness of this welding method applied to various commercially significant medical grade polymers with emphasis on PVC of varying hardness. The study compares measured weld strength and weld quality (inspected microscopically) at ambient and elevated temperatures. Also, selected samples of polymeric compounds were exposed after RF welding to gamma radiation, a method of medical device sterilization, in order to study the effects on the weld strength and color shift in the weld area. Of prime interest is the determination of optimum welding parameters for various constructions of plastic compounds.     

Thermal properties and processability of talc‐ and calcium carbonate‐filled poly(vinyl chloride) hybrid composites

The main objective of this investigation was to study and compare the thermal rigidity, thermal stability, and processability of poly(vinyl chloride) (PVC) composites filled with single fillers of talc and uncoated ground CaCO₃ (SM 90) or a hybrid filler consisting of talc/SM 90. To produce the composites, the PVC resin, fillers, and other additives were dry‐blended in a laboratory mixer before being milled into sheets by using a two‐roll mill. Test specimens were prepared by compression molding, after which the thermal properties and processability of the composites were determined. Single and hybrid filler loadings used were fixed at 30 phr (parts per hundred parts of resin). Talc‐filled PVC composite showed slightly better thermal stability and rigidity than the composite filled with SM 90, and its thermal stability and rigidity slightly decreased with SM 90 content increasing from 5 to 25 phr in order to replace talc filler in the hybrid composites. The fusion time of talc‐filled PVC composite was shorter than that of SM 90‐filled PVC composite; thus, the fusion time of hybrid composites increased with increasing SM 90. The fusion torque showed an opposite behavior. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers