Calcium silicate hydrate—in-situ development of the silicate structure followed by infrared spectroscopy

In the current study, the development of the silicate structure of synthetic calcium silicate hydrates with different calcium contents was followed by in-situ infrared (IR) spectroscopy and correlated to the in-situ phase development evaluated by X-ray diffraction (XRD). A baseline correction method initially developed for X-ray diffractograms was successfully adapted for the complex background of the fingerprint region in in-situ IR, which significantly contributed to signal quality and reproducibility. The development of separate silicate infrared bands could be monitored over 24 h of reaction. These bands could be assigned to oligomeric and dimeric species based on their time and stoichiometry-dependent development. It was clearly shown that the main peak of the dimeric silicate species was overlooked in the literature. The correlation of time-dependent events to in-situ XRD revealed that changes in the unit cell of calcium silicate hydrate are related to silicate polymerization. The results were compared to ²⁹Si-MAS-NMR, which highlighted the benefits of in-situ IR spectroscopy.     

Modification of porous suspension‐PVC particles by stabilizer‐free aqueous dispersion polymerization of absorbed monomers

The modification of porous PVC particles by an in‐situ stabilizer‐free polymerization/crosslinking of a monomer/crosslinker/peroxide solution absorbed within the PVC particles is presented. The modifying crosslinked polymers are polystyrene (PS) crosslinked with DVB (divinyl benzene), polymethyl methacrylate (PMMA) crosslinked with ethylene glycol dimethacrylate (EGDMA), and styrene‐MMA copolymer crosslinked with DVB. The modified PVC particles characterization includes polymerization yield, non‐extractables, ¹³C solid‐state CPMAS NMR, porosity measurements and also morphology and dynamic mechanical behavior (DMTA). The levels of nonextractable fractions found and ¹³C solid‐state CPMAS NMR results are indicative of low chemical interaction in the semi‐IPN PVC particles. Particle porosity levels and SEM observations indicate that styrene and MMA mainly polymerize within the PVC particles' bulk and just small amounts in the pores. MMA polymerization in the PVC pores is as crusts covering the PVC pore surfaces, whereas styrene polymerization in the PVC pores is by filling the pores. Dynamic mechanical studies show that tanδ and the storage modulus curves are influenced by the incorporation of PS and XPS but not by the incorporation of PMMA and XPMMA.     

Mechanism of stabilization of poly(vinyl chloride). I. The cleavage of organotin compounds by aqueous hydrochloric acid

A number of organotin compounds with the general formula R_nSnY_4-n where R = alkyl and aryl, Y = thiolate, carbothiolate, and carboxylate, and n = 0, 1, 2, 3 were cleaved with aqueous hydrochloric acid to give the corresponding organotin chlorides and thiols, carbothiolic acids or carboxylic acids. The organotion salts were also evaluated as thermal stabilizers for PVC, and their efficiency was compared with the nature of the aqueous acid cleavage products.¹     

The mechanism of stabilization of poly(vinyl chloride). II. Cleavage of organotin sulfur compounds by anhydrous hydrogen chloride

A number of organotin compounds of the type R_nSn Y_4–n, where R = alkyl or aryl; Y = alkylthio, arylthio or carbothiolate; and n = 1, 2, 3 have been prepared and treated with hydrogen chloride at 180°C in o-dichlorobenzene solution. The organotin compounds were also tested at 190°C as thermal stabilizers for PVC. Cleavage of tin–carbon bonds by hydrogen chloride was demonstrated in some cases by analysis of the organotin–hydrogen chloride reaction products. The formation of monoalkyl(aryl)tin chlorides or stannic chloride, or both, in the model system was shown to correspond to a catastrophic mode of degradation in the polymer. The use of stabilizers with fewer than two alkyl or aryl groups on tin also gave this mode of degradation.     

Photodegradation of plasticized poly(vinyl chloride) stabilized by different types of thermal stabilizers

Photodegradation of plasticized poly(vinyl chloride) (PVC) stabilized by different thermal stabilizers including organic calcium complex and mercaptide organotin was investigated. Plasticized PVC sheets prepared by an open twin‐roller mill and plate vulcanizing machine were exposed to xenon‐arc light with the irradiance of 0.51 W/(m²·nm) at 65°C. A much better color stability displayed by mercaptide organotin than organic calcium complex has been confirmed by digital photos and color difference. This can be explained that the more effective mercaptide organotin minimizes the amount of thermal damage from processing thus favours subsequent UV weathering. Carbonyl index and decomposition activation energy (E_a1) obtained from attenuated total refection‐Fourier transform infrared spectra (ATR‐FTIR) and thermogravimetric (TG) analysis, respectively, further indicate that plasticized PVC sheets containing mercaptide organotin have more excellent UV resistance. Mechanical tests reveal that photodegradation of PVC is accompanied by the predominant process of chain scission on the surface of samples. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Improving mechanical properties of poly(vinyl chloride) by doping with organically functionalized reactive nanosilica

Nanosilica particles are functionalized by in situ surface‐modification with trimethyl silane and vinyl silane. Resultant reactive nanosilica (coded as RNS) contains double bonds and possesses good compatibility with vinyl chloride (VC) and polyvinyl chloride (PVC). This makes it feasible for RNS to copolymerize with VC generating RNS/PVC composites via in situ suspension polymerization. As‐prepared RNS/PVC composite resins are analyzed by means of FTIR. The tensile strength and impact strength of compression‐molded RNS/PVC composites are measured and compared with that of compression‐molded PVC composites doped with dispersible nano‐SiO₂ particles (abridged as DNS) surface‐modified with trimethyl silane alone. Moreover, the thermal stability of compression‐molded RNS/PVC and DNS/PVC composites is evaluated by thermogravimetric analysis. It has been found that RNS/PVC composites possess greatly increased impact strength and tensile strength than PVC matrix, while DNS/PVC composites possess higher impact strength than PVC matrix but almost the same tensile strength as the PVC matrix. This implies that DNS is less effective than RNS in improving the mechanical strength of PVC matrix. Particularly, RNS/PVC composites prepared by in situ suspension polymerization have much higher mechanical strength than RNS/PVC composites prepared by melt‐blending, even when their nanosilica content is only 1/10 of that of the melt‐blended ones. Besides, in situ polymerized RNS/PVC and DNS/PVC composites have better thermal stability than melt‐blended nanosilica/PVC composites. Hopefully, this strategy, may be extended to fabricating various novel high‐performance polymer‐matrix composites doped with organically functionalized nanoparticles like RNS. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Development of antifouling poly(vinyl chloride) blend membranes by atom transfer radical polymerization

In this study, antifouling poly(vinyl chloride) (PVC) blend membranes were prepared by blending the PVC based amphiphilic copolymer PVC‐g‐poly(hydroxyethyl methacrylate) (PVC‐g‐PHEMA), synthesized by atom transfer radical polymerization (ATRP), into the hydrophobic PVC matrix via the nonsolvent‐induced phase separation method. The in situ ATRP reaction solutions were also used as the blend additives to improve membrane performance. Attenuated total reflectance–Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy indicated that the blend membranes based on the two blend routes exhibited similar surface chemical compositions. The membrane morphology and surface wettability were determined by scanning electronic microscopy and water contact angle measurement, respectively. The blend membranes showed improved water permeability, comparable rejections and enhanced antifouling properties compared with the pure PVC membrane. The PVC blend membranes also had excellent long‐term stability in terms of chemical compositions and fouling resistance. The results demonstrated that ATRP was a promising technique to synthesize amphiphilic copolymer and prepare stable blend antifouling membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45832.     

Effects of component addition protocol on the reactive compatibilization of HDPE/PET blends

Polyethylene terephtyalate (PET) and high-density polyethylene (HDPE) constitute a major portion of the thermoplastic materials currently being used in the packaging industry. Blends of HDPE/PET can be compatibilized by utilizing ester groups or terminal carboxyl and hydroxyl groups present in PET. An ethyleneglycidyl methacrylate copolymer (EGMA) was found to be very effective in compatibilizing this blend by forming a compatibilizer in-situ. The in-situ formation of the compatibilizer and its distribution could be affected by different sequences and modes of component addition. To determine the best protocol of component addition for such a reactive compatibilization process, different sequences and modes of component addition were tried out in an intensive batch mixer and in a twin-screw extruder. All these experiments resulted in blends with vastly different dispersion of the minor phase and mechanical properties. In general, sequences where the reactive polymer was grouped with the nonpolar component of the blend initially resulted in the best compatibilization.     

Effect of the combination of a benzotriazole‐type ultraviolet absorber with thermal stabilizers on the photodegradation of poly(vinyl chloride)

The effect of the combination of a benzotriazole type of UV absorber (UV326) with different types of thermal stabilizers, including an organic calcium complex and an organotin mercaptide, on the photodegradation of poly(vinyl chloride) (PVC) was investigated by color difference measurements, UV‐vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and viscosity‐average molecular weight (M_η) determinations. Films of PVC containing 0.5 phr of UV326, with or without 2 phr of thermal stabilizer, were prepared by solution casting and subjected to accelerated UV weathering under xenon light with an irradiance of 0.51 W/(m² nm) at 65°C. The results revealed that both UV326 and the mixture of UV326 with the organic calcium complex displayed good performance in inhibiting the photodehydrochlorination and photooxidation of PVC. In contrast, the combination of UV326 and the methyltin mercaptide remarkably accelerated the discoloration of PVC when the irradiation time increased from 300 to 400 h because of the UV sensitivity of the organotin. However, carbonyl index data indicated that a hydrogen abstraction reaction did not take place between UV326 and the methyltin mercaptide, so that the photooxidation of the PVC film was prevented effectively during the whole period of exposure, a result which may be attributed to the strong steric hindrance effect of the tert‐butyl group at the 3‐position of the phenyl ring in UV326. The changes of M_η were in good accordance with the results obtained from other characterizations. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

A new strategy for plasticizing and stabilization of PVC mixtures

This study was undertaken to examine possible use of classic tetravalent tin‐based heat stabilizers for the preparation of a polymer plasticizer: poly(ε‐caprolactone) (PCL) and simultaneous stabilization of PVC in PVC/PCL mixtures. PCL was prepared from ε‐caprolactone (CL) by polymerization initiated by tin‐containing organic compounds and successfully used to simultaneously plasticize and stabilize PVC. Moreover, conditions under which the polymerization of CL took place directly in situ during PVC/CL mixture processing were found. The procedure yielded homogeneous plasticized PVC/PCL mixtures, which were stable and contained >90% of the original monomer content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41066.     

Liquid-phase degradation of poly(vinyl chloride)

The main kinetic regularities of the thermal and thermal-oxidative degradation of poly(vinyl chloride) (PVC) in the liquid phase have been analyzed in comparison with the solid-phase degradation of PVC. The thermal (in an N₂ atmosphere) degradation of PVC in the form of dilute solutions is characterized by a number of essential distinctions, the primary peculiarity consisting of a lower dehydrochlorination rate due to the retarded reaction of the formation of bond polyconjugated systems. The same is observed for the thermal degradation of PVC plasticized with di- and polyesters. On the contrary, in an oxygen-containing atmosphere the solvents promote PVC decomposition. Accelerated PVC degradation under such conditions is due to the solvent oxidation that causes the appearance, within the system, of products activating the PVC macromolecular decomposition. The intensified degradation processes are accounted for, in the first place, by an increased reaction rate of the statistical (by the random law) detachment of HCl from normal macromolecular units. In general, the kinetics of the thermal-oxidative liquid-phase degradation of PVC is determined by the partial pressure of oxygen in the reaction zone, by the quantity of the solvent introduced into the polymer, as well as by the oxidative stability of the solvent. It has been shown that an effective stabilization of PVC in the liquid phase, particularly in the systems highly plasticized with esters, can be achieved through stabilizing the solvent, first of all, rather than the polymer, against oxidative decomposition. In this case the PVC dehydrochlorination rate decreases sharply and may reach an essentially lower value than under similar conditions of the solid-phase thermal degradation of PVC. PVC stabilization with respect to the reaction of HCl elimination achieved through the solvent stabilization against thermal-oxidative decomposition has been called the effect of “echo-stabilization” of PVC.     

In-situ generation and application of nanocomposites on steel surface for anti-corrosion coating

Thin organic coatings directly on steel sheets provide excellent barrier protection in saline environment and meet deformability demands, but fail in providing active corrosion protection. We have put an effort to solve this problem by formulating composite coatings using in-situ generation of metal oxide nanoparticles (NPs) in the polymer matrix. Here we present a new synthesis method of high performance polyetherimide composite with TiO₂, MgO, and Al₂O₃ nanoparticles and their application for anti-corrosion coatings in saline environment. We observed that in-situ synthesis of these metal oxide NPs in the polymer curing process leads to evenly distribution and uniform size of nanoparticles. Thermo-mechanical property was analyzed for these three kinds of free-standing composite film to assess elasto-plastic behaviour and compared to mother polymer film. Results indicated that thermal stability and elastic behaviour of composites film are not affected to the great extent by the presence of NPs. The potentiodynamic and the electrochemical impedance studies on these composite coated steel panels were carried out to identify active–passive behaviour. Results showed active corrosion protection from nanocomposite coating based on TiO₂ and barrier protection was noticed from nanocomposite coating based on MgO and Al₂O₃.     

Fusion bonding of maleated polyethylene blends to polyamide 6

Blends of linear low-density polyethylene (LLDPE) and linear low-density polyethylene–grafted maleic anhydride (LLDPE-gMA) were used to promote the adhesion to polyamide 6 (PA) in a three-layer coextruded film without using an additional adhesive or tie layer. The effect of bonding time and molecular weight (MW) of different maleated polyethylenes on the peel strength of the joints was analyzed. Direct evidence of a copolymer formed in-situ at the interfaces is also considered. The peel strength of fusion bonded layers of LLDPE/LLDPE-gMA blends with PA strongly depends on bonding time and molecular weight of the maleated polymer. Tensile properties of three-layer films, made up of PA as the central layer and LLDPE/LLDPE-gMA blends as the two external layers, are improved with increases in the maleic anhydride (MA) content in the blend. The in-situ formation of a copolymer between the MA in the blend and the terminal amine groups of the PA was confirmed by the Molau test, infrared (IR) spectroscopy, and thermal analysis (DSC).     

新型聚氯乙烯热稳定剂—水滑石的研究

在国内首次研究了水滑石类镁铝层状双氢氧化物（LDH）对硬质和软质聚氯乙烯的热稳定作用,介绍了该稳定剂的共沉淀合成方法,并对其进行了X射线衍射分析及热量分析。结果表明,该种新型热稳定剂具有重要的环保价值和经济效益,LDH与有机复配,对硬质PVC具有协同稳定作用,并且降低了制品成本;LDH对软质PVC的热稳定效果优于Ba－Zn／环氧在豆油体系,具有广阔的应用前景。     

Chemical Grafting of Crosslinked Polypyrrole and Poly(vinyl Chloride) onto Modified Graphite: Fabrication,Characterization, and Material Properties

ABSTRACT

Conjugated polymer/graphite nanocomposites have been known as high performance materials owing to improve the physicochemical properties relative to conventional once. Multilayered polymer nanocomposites based on polypyrrole (PPy), polyvinylchloride (PVC) as matrices and p-phenylene diamine (PDA) as linker were prepared via chemical in situ polymerization process and subsequently investigated the physical characteristics of fabricated nanocomposites at various loadings. The structural characterization and morphology of prepared nanocomposites were inspected by Fourier transform infrared spectroscopy (FTIR), X-ray photon spectroscopy (XPS), energy dispersive X-ray spectroscope (EDX), field emission scanning electron microscope (FESEM), respectively. The composite III showed higher thermal stability at 10 wt% loading of PPy. According to differential scanning calorimetry (DSC), the glass transition temperature (T_g), melting temperature T_m, and crystallization temperature (T_c) of nanocomposites increases with PPy loading (2–10 wt%) owing to crosslinking and chain rigidity. Moreover, higher surface area was displayed by the multilayered PPy/PVC/PDA@FG nanocomposites. Remarkably, electrical conductivity of ultimate nanocomposites was also found to be a function of PPy loading.     

Preparation of cardanol based epoxy plasticizer by click chemistry and its action on poly(vinyl chloride)

In recent years, the using of reproducible resource and economical and efficient synthesis method has got wide concern. Herein, an environmental‐friendly plasticizer originated from cardanol was synthesized by click chemistry. First, the cardanol sulfide (CS) was obtained by click chemistry reaction between the double bond of the side chain of cardanol and mercaptoethanol. The degree of the click reaction was estimated to reach 84.7% by testing the content of sulfur. Then, the epoxidation of the hydroxyl was performed to get cardanol based epoxy plasticizer (CEP) in the presence of epichlorohydrin. The epoxy value was 0.32. The structure of CS and CEP was confirmed by FT‐IR and NMR techniques. A Haake torque rheometer was used to research the action of CEP on polyvinyl chloride (PVC). Results showed that it possessed favorable plasticization effect and stabilization effect on PVC. CEP had good heat stabilization in PVC, and could decrease the T_g of PVC significantly. Moreover, CEP could increase the tensile strength of PVC when in a small amount, and could increase the plasticity of PVC when in a larger quantity significantly. The characteristics of volatile, migration and solvent extraction of PVC plasticized by CEP is similar to by dioctyl phthalate (DOP). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44890.     

A study of PVC stabilization with epoxides using dynamic pH determinations

The activation energy (E_a) for the dehydrochlorination of PVC and PVC stabilized with an epoxide was determined by a method involving dynamic pH measurements. The E_a increase was 5 kcal/mole between unformulated PVC (E_a = 22.6 kcal/mole) and any of the other formulations (E_a = 27.7–28.6 kcal/mole). On the basis of this and data contained in the literature, research alternatives for the stabilization mechanism are proposed using model compounds.     

Synthesis of 2-Organylchalcogenopheno[2,3-b]pyridines from Elemental Chalcogen and NaBH4/PEG-400 as a Reducing System: Antioxidant and Antinociceptive Properties

An alternative method to prepare 2-organylchalcogenopheno[2,3-b]pyridines was developed by the insertion of chalcogen species (selenium, sulfur or tellurium), generated in situ, into 2-chloro-3-(organylethynyl)pyridines by using the NaBH₄/PEG-400 reducing system, followed by an intramolecular cyclization. It was possible to obtain a series of compounds with up to 93 % yield in short reaction times. Among the synthesized products, 2-organyltelluropheno[2,3-b]pyridines have not been described in the literature so far. Moreover, the compounds 2-phenylthieno[2,3-b]pyridine ( 3 b ) and 2-phenyltelluropheno[2,3-b]pyridine ( 3 c ) exhibited significant antioxidant potential in different in vitro assays. Further studies demonstrated that compound 3 b exerted an antinociceptive effect in acute inflammatory and non-inflammatory pain models, thus indicating the involvement of the central and peripheral nervous systems on its pharmacological action. More specifically, our results suggest that the intrinsic antioxidant property of compound 3 b might contribute to attenuating the nociception and inflammatory process on local injury induced by complete Freund's adjuvant (CFA).     

Synthesis of protective coatings on steel by surface spontaneous polymerization. 3: Process development and coating property studies

We have previously reported a new method for applying protective coatings on metal surfaces, the Surface Spontaneous Polymerization Process (1). In this process, polymerization occurs spontaneously on the substrate upon immersion into a monomer solution, forming a layer of uniform coating in-situ. No initiator is added. In this paper, studies on the development of the process and coating properties are reported. A monomer reaction system containing phenylmaleimide/styrene/bismaleimide/2-(methacryloyoxy)ethyl acetoacetate has been developed to afford protective coatings on steel. The coatings obtained from this system have good thermal, dielectric, and adhesion properties. Corrosion resistance of 4CPMI coatings, as measured by the ASTM B-117 salt spray test, is excellent after 700 hours of salt spray. The effects of several process variables on the polymer molecular weight were also studied, including monomer concentration, solution temperature, solution pH, and monomer feed composition. Solution stability studies indicate that polymerization occurs only on the surface and does not propagate into the solution.     

Effect of thermotropic copolyesteramide on the properties of polyamide‐66/liquid crystalline copolyester composites

Liquid crystalline copolyester‐polyamide 66 (LCPES/PA66) composites compatibilized by liquid crystalline copolyesteramide (LCPEA) were prepared by injection molding. The LCPES employed was a commercial copolyester, Vectra A950, and the LCPES was a semiflexible thermotropic copolyesteramides based on 30 mol% of p‐amino benzoic acid (ABA) and 70 mol% of poly(ethylene terephthalate) (PET). Thermal analysis, mechanical characterization, and morphological investigations were conducted on the blends. The dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) tests showed that LCPEA is an effective compatibilizer for the LCPES/PA66 composites. The mechanical measurements showed that the stiffness, tensile strength and Izod impact strength of the in‐situ composites are improved by adding LCPEA because of the compatibilization and reinforcement to LCPES/PA66 composites. However, the properties improvement vanished when LCP content reached 10 wt%. The drop weight dart impact test was also applied to analyze the impact fracture characteristics of these composites. The results showed that the maximum impact force (F_max), crack initiation and propagation energy all improved with the addition of a small percent of LCPEA. From these results, it appeared that LCPEA prolongs the time for crack initiation and propagation. It also increases the energies for crack initiation and propagation, thereby leading to toughening of the LCPES/PA66 in‐situ composites. Finally, the correlation between the mechanical properties and morphology of the composites is discussed.