THE EFFECT OF MONOMERS FEEDING METHODS ON EMULSION COPOLYMERIZATION OF VINYLIDENE CHLORIDE AND ACRYLATES

The emulsion copolymerization of vinylidene chloride (VDC) with methyl-methacrylate(MMA) and acrylonitrile (AN) was carried out by batch, seeded batch and semicontinuous pro-cesses,respectively. Significant differences were found in the physical and mechanical propertiesof the latexes and films, depending on the methods of monomer feeding. The results both intheory and experiments demonstrated that the copolymer composition and the length of the VDC sequences in the copolymer could be controlled by the modes of monomer feeding process.

PARTICLE MORPHOLOGY OF POLY(VINYL CHLORIDE)RESIN PREPARED BY SUSPENDED EMULSION POLYMERIZATION

Suspended emulsion polymerization was used to prepare poly(vinyl chloride) (PVC) resin. Fine PVC particleswere formed at low polymerization conversions. The amount of fine panicles decreases as conversion increases anddisappears at conversions greater than 30%. Scanning electron micrographs show that PVC grains are composed of looselycoalesced primary particles, especially for PVC resins prepared in the presence of poly(vinyl alcohol) dispersant. The size ofprimary particles increases and porosity decreases with the increase of conversion. In view of the particle features of PVCresin, a particle formation mechanism including the formation of primary particles and grains is proposed. The formationprocess of primary particles includes the formation of particle nuclei, coalescence of particle nuclei to form primary particles,and growth of primary particles. PVC grains are formed by the coagulation of primary particles. The loose coalescence ofprimary particles is caused by the colloidal stability of primary particles and the low swelling degree of vinyl chloride in the primary particles.

Influence of Suspended Emulsion Polymerization Conditions on Particle Characteristics of Polyvinyl Chloride Resin

Suspended emulsion polymerization of vinyl chloride was carried out in a 5 L autoclave. The influence of agitation, polymerization conversion, dispersant and surfactant on the average particle size (PS) and particle size distribution (PSD), particle morphology and porosity of polyvinyl chloride (PVC) resin was investigated. It showed that the agitator had great influence on the smooth operation of polymerization, PS and PSD. The PS increased and PSD became narrow as polymerization conversion became high. The porosity decreased with the increase of conversion. A convenient choice of additives, both dispersants and non-ionic surfactants, allows one to adjust PS and PSD. The PS decreased with the addition of polyvinyl alcohol or hydroxypropyl methylcellulose dispersants,and increased with the addition of Span surfactants. The addition of dispersants or surfactants also affected the morphology and porosity of resin, and PVC resin with looser agglomeration and homogeneous distribution of primary particles was prepared.

Rotational Isomeric State Model of Poly(vinylidene chloride) Based Upon ab Initio Electronic Structure Calculations

The rotational isomeric state（RIS） model was constructed for poly（vinylidene chloride）（PVDC） based on quantum chemistry calculations. The statistical weighted parameters were obtained from RIS representations and ab initio energies of conformers for model molecules 2,2,4,4-tetrachloropentane（TCP） and 2,2,4,4,6, 6-hexachloroheptane（HCH）. By employing the RIS method, the characteristic ratio C∞ was calculated for PVDC. The calculated characteristic ratio for PVDC is in good agreement with experiment result. Additionally, we studied the influence of the statistical weighted parameters on C∞ by calculating δC∞/δlnw. According to the values of δC∞/δlnw, the effects of second-order Cl-CH2 pentane type interaction and C1--C1 long range interaction on C∞ were found to be important. In contrast, first-order interaction is unimportant.

Rare Earth Stearates as Thermal Stabilizers for Rigid Poly(vinyl chloride)

A series of stearates with different rare-earth ion were investigated as thermal stabilizers for rigid PVC at 180 ℃ in air. Their stabilizing efficiency was based on measuring the rate of dehydrochlorination. The resulted revealed the higher stabilizing efficiency of the investigated rare-earth stearates as thermal stabilizers for rigid PVC compared with the thermal stabilizers for industry: calcium stearate, zinc stearate, butyl stannum mercaptide, phosphite esters, β-diketone and epoxidized sunflower oil. This was well illustrated by longer incubation period (T_S) values and lower rate of dehydrochlorination. The stable efficiency was affected by the nature of rare-earth element's individual electronic shell. The mechanism for the stabilizing effect of rare-earth stearates was proposed. The result was experimentally proved based on IR spectrum.

Creep Behaviour of Wood Flour/Poly(vinyl chloride) Composites

The experimental creep data were focused on wood-flour （WF）/poly vinyl chloride （PVC） composites with the variations in additive concentrations of wood flour, silane coupling agent, organomodified montmorillonite （OMMT） and nano-cacium carbonate （nano-CaCO3）. Their effects were analyzed using the Four-element Burger Model incorporating microscopic mechanisms. Total creep strain was low with increasing WF while elastic strain was high and plastic flow strain was low in modeling. Modification of WF with silane was beneficial to creep resistance, so did adding low ratio of OMMT （1.5 wt%） and nano-CaCO3 in composites. Thus, it was effective in reducing creep either by stiffening the PVC matrix using rigid nano-particles or by improving their adhesion with resin. However, superfluous quantity of any additament did not benefit the improvement owing to either earlier destruction of their agglomerates or stress-concentrated cracks in the over-incrassated interface.

Antiplasticizing Effect of MOCA on Poly(vinyl chloride)

An obvious antiplasticizing effect has been observed in PVC with small amount of MOCA, 3,3’-dichloro-4,4’-diamino-diphenylmethane. PVC-MOCA interaction and crystallization behavior of PVC/MOCA blends were investigated in detail to explain the mechanism of antiplasticization on the basis of a series of techniques including DMA, FTIR, and DSC. The results of mechanical properties tests show that the tensile strength of PVC with 5 phr of MOCA reaches a maximum value, 69.5 Mpa, which is about 23 % higher than that of pure PVC. The rise in tensile strength was attributed to an antiplasticizing effect of MOCA on PVC as confirmed by DMA measurements. The evidences from FTIR reveal that a strong hydrogen-bonding interaction takes place between the nitrogen atom of –NH2 groups in MOCA and the methine proton of PVC repeat units. The results of DSC analysis indicate that crystallization behavior of MOCA is suppressed completely and the crystallinity of PVC decreases with the increase of MOCA amount.

Influence of Annealing and Additives on the Crystallization Behavior and Properties of Poly(vinyl chloride)

Acetanilide （AC）, adipic acid （AA） and potassium hydrogen phthalate （PHP） were chosen as additives to accelerate PVC crystallization and improve its mechanical properties. The influences of the additives and annealing on the crystallization behavior, micromorphology and the tensile properties were investigated by the thermal analysis, scanning electron microscopy （SEM） and the tensile test. Based on the analysis results, it was concluded that the melting peaks ranging from 110 to 200 ℃ and 200 to 240 ℃ were caused by the fusion of the fringed micelle crystals and chain-folded crystals respectively. AC advanced the fringed micelle crystal to develop, while AA and PHP promoted obviously the chain-folded crystal to grow. The addition of the foreign additives did not change the growth pattern ofPVC crystallites, the growth of the micelle crystal was favorable at 110 ℃, and the chain-folded crystal was developed at higher temperature. For PVC/ AA and PVC/PHP, when annealed at 110 ℃, a regular nest like network was formed, the crystallinity and the crystallite size were increased as well, and as a result, the tensile strength, Young＇s modulus and the elongation at break point were improved simultaneously and greatly.

Structures of LDHs Intercalated with Ammonia and the Thermal Stability for Poly(vinyl chloride)

MgAl-NH3 LDHs (layered double hydroxides), ZnAl-LDHs and ZnAl-NH3 LDHs with different molar ratio of Al/ammonia were synthesized by co-precipitation method. The synthetic LDHs samples were characterized by XRD, FT-IR, TGA-DTG and SEM techniques and tested by Congo red method. In addition, after PVC (Poly vinyl chloride) and DOP (Dioctylphthalate) were added to LDHs, the thermal stability for PVC was characterized by TGA-DTG. The results indicated that LDHs intercalated with ammonia improved thermal stability for PVC significantly, MgAl-NH3 LDHs (Mg2+:Al3+: NH3·H2O = 3:1:0.5) and ZnAl-NH3 LDHs (Zn2+:Al3+:NH3·H2O=2:1:1.5) showed the best thermal stability for PVC, interlayered space of LDHs became larger by intercalating ammonia.

UV enhanced gas–solid synthesis of chlorinated poly vinyl chloride characterized by a UV–Vis online analysis method

Dynamic characteristics of UV enhanced gas–solid PVC chlorination process were revealed by a UV–Vis spectral online analysis method. Experimental results showed an instantaneous increase of the chlorination rate as soon as UV light was affiliated, which demonstrated the intensified effect of UV radiation on PVC chlorination directly.Different affiliation methods of UV light were then studied, proving that continuous UV radiation could enhance the chlorination process significantly while intermittent UV radiation was able to initiate the chlorination reaction once it was conducted. Besides, experiments were carried out to study the influences of parameters on the chlorination process such as UV wavelength, chlorination temperature, partial pressure of chlorine gas and PVC raw materials. Among all the parameters, chlorination temperature and partial pressure of chlorine gas were testified as two key factors to determine the chlorination performance. Thermal analysis of CPVC products showed that their corresponding properties such as the glass transition temperature(Tg) and the homogeneity of chlorine distribution in polymer phase were improved with the increase of chlorine content.

Synthesis of CaZnAl-CO3 ternary layered double hydroxides and its application on thermal stability of poly(vinyl chloride)resin

In this work,hydrothermal method was used to prepare the CaZnAl-CO3 ternary layered double hydroxides(CaZnAl-CO3-LDHs)with various Ca/Zn/Al molar ratios,which were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscope(FT-IR)and scanning electron microscopy(SEM)techniques.The obtained results demonstrate that the samples were well-crystallized and flake-structured.The CaZnAl-CO3-LDHs used alone for thermal stability of poly(vinyl chloride)(PVC)resin,with different Ca/Zn/Al molar ratios and varying additive amounts,were investigated through the tests such as static thermal aging,mass loss and congo red,respectively.The optimum Ca/Zn/Al molar ratio and additive amount were 3.6:0.4:2 and 5 phr(parts per hundred PVC resin),respectively.In addition,the synergistic effects of Ca3.6Zn0.4Al2-CO3-LDHs and CaSt2 were discussed in detail,showing better thermal stability compared with Ca3.6Zn0.4Al2-CO3-LDHs used alone,and the optimum additive amounts of Ca3.6Zn0.4Al2-LDHs and CaSt2 were 6 and 1.0 phr,respectively.

Synthesis of Bio-Plasticizer from Soybean Oil and Its Application in Poly(Vinyl Chloride) Films

Herein,epoxidized soybean oil methyl ester(ESOM)plasticizer was synthesized for the preparation of plasticized poly(vinyl chloride)(PVC)films by the alcoholysis and epoxidation.The chemical structure of ESOM was investigated by infrared spectrum and 1 H nuclear magnetic resonance.The effect of content of ESOM and petroleum based plasticizer di-2-ethylhexyl phthalate(DEHP)on the performance of plasticized PVC films was studied.The result showed that substituting DEHP with ESOM can improve the thermal stability of plasticized PVC films.When the weight ratio of ESOM and PVC is fixed at 1:2,plasticized PVC film presents higher elongation at break(350.8%vs.345.1%)and lower tensile strength(14.21 MPa vs.15.8 MPa)compared with PVC plasticized with DEHP.ESOM showed less weight loss than DEHP in all solvents.The excellent migration resistance of ESOM is helpful to improve stability of plasticized PVC films.In all,the obtained bio-based plasticizer will be potential to replace petroleum based plasticizer DEHP in flexible PVC materials.

Effect of phosphite and epoxy soybean oil on heat stability of poly （vinylchloride） composite stabilizers

The influences ofphosphite and epoxy soybean oil in combination with liquid calcium/zinc isocaprylates on the thermal stability of flexible poly （vinyl chloride） were studied. The stabilizing effect of poly （vinyl chloride） was evaluated by Congo red method, thermoaging test and Thermogravimetric-differential Scanning Calorimetry （TG-DSC）. The results showed that the addition of the phosphite or epoxy soybean oil improved the thermal stability of PVC with the calcium/zinc isocaprylates stabilizing system, especially epoxidied soybean oil exhibited a remarkable effect, and the synergism on PVC thermal stability for 3：2 phenyl dioctyl phosphite to epoxidized soybean oil weight ratio was acquired. Accordingly, the rapid mass loss in TG curve occured between 258.9 ℃ and 334.4 ℃, which corresponded to the enthalpy of the pyrogenation of 609.2 J/g. It was also found that the stabilized PVC of the best ratio gave better mechanical and processing properties.

PHASE EQUILIBRIUM FOR THE TERNARY SYSTEM VINYL CHLORIDE-CHLORINATED POLYETHYLENE-POLY(VINYL CHLORIDE)

Swelling capacity of vinyl chloride (VC) in chlorinated polyethylene (CPE) with 25—40 wt% Cl at temperature 30—57℃ was studied and their relationships were correlated with Langmuir and Freundlich adsorption equations. A ternary phase diagram for VC-CPE-PVC was also established. In-situ polymerization conditions of CPE-g-VC were proposed and CPE content control was analyzed for the manufacturing process of CPE-g-VC graft product based on results of phase equilibrium study.

Preparation of MgAl LDHs Intercalated with Amines and Effect on Thermal Behavior for Poly(vinyl chloride)

MgAl LDHs intercalated with CO(NH2)2, NH4Cl and NH3·H2O were prepared by co-precipitation and XRD, FT-IR, TGA-DTA and SEM techniques were employed for characterization. The results indicated that the layer-layer spacing of LDHs was enlarged by 0.169, 0.285 and 0.227 Åwith the intercalation of CO(NH2)2, NH+4 and NH3, separately. The effects on thermal stability and degradation behavior of synthesized LDHs where mole ratios of Mg/Al/urea = 3:1:1, Mg/Al/NH4Cl = 3:1:1.5 and Mg/Al/NH3·H2O = 3:1:0.5 were investigated by Congo Red Method and thermogravimetric analysis (TGA) from 25°C - 800°C under N2. The TGA and DTA results showed, by incorporating 5% MgAl-CO(NH2)2 LDH, the dehydrochlorination temperature of PVC composites is 12°C higher than MgAl-NH+4 and MgAl-NH3 LDHs. MgAl-NH3 LDH enhances the ending temperature of the first degradation stage of PVC composites by 8°C compared with MgAl LDH. The LDH intercalated with CO(NH2)2 is proved to be an effective thermal stabilizer for PVC processing.

Microstructure and Mechanical Properties of Poly (Vinyl Chloride) Modified by Silica Fume /Acrylic Core-Shell Impact Modifier Blends

This research explored replacing acrylic core-shell impact modifier （AIM） by silica fume to toughen PVC. 100%, 75%, 50% and 25% of AIM （8 phr） were substituted by silica fume in PVC respectively, and then processed by dry blending and twin-screw extrusion. Severe silica fume agglomeration was observed by scanning electron microscope （SEM） in the PVC matrix when 8 phr pure silica fume was used and processed by screw speed of 20 rpm. Its tensile strength was thereby reduced by 38% comparing to unmodified PVC. The silica fume was successfully dispersed while the screw speed was slowed down to 10 rpm to give a stronger screw torque and a longer melt residential time in the extruder. The tensile strength was ’recovered’ to a level comparable to unmodified PVC. Impact test were performed on all formulations extruded at 10 rpm screw speed and synergetic toughening effect was found with 50% substitution and it had the impact strength that was comparable to 8 phr pure AIM toughened PVC.

Development of a Poly(vinyl chloride)-based Nitrate Ion-selective Electrode

The authors developed a nitrate ion-selective electrode（ISE） based on poly（vinyl chloride）（PVC） membrane with methyltrioctylammonium nitrate as a carrier and 1-decanol as a plasticizer.The performance of the nitrate-sensitive membranes was optimized by tuning the composition of components.The electrode exhibits a linear response with a Nernstian slope of（52±1.0） mV per decade for the nitrate ion concentration ranging from 5.8×10-5 mol/L to 1.0 mol/L.The electrode can be used to detect a low concentration of nitrate ions down to 3×10-5 mol/L in a pH range of 2.1―11.5 without any compensation.The advantage of the electrode includes simple preparation,short response time and good repeatability.The detection performance of the novel electrode on nitrate ions has been tested for water samples.

Surface Modification of Poly Vinyl Chloride (PVC) Using Low Pressure Argon and Oxygen Plasma

In this study, commercial poly vinyl chloride （PVC） films were treated by oxygen and argon plasmas in a cylindrical glass tube which was surrounded by a DC variable magnetic field, with different sample positions in the plasma reactor and also different exposure durations. Effects of the plasma treatment on the hydrophilic properties of the films were studied by mea- suring the water drop contact angle on the surface of the samples. The surface topography of the untreated and plasma treated films was analyzed and compared by atomic force microscopy （AFM）. The optical characteristic changes in treated samples were investigated using reflective spectrophotometry. Also, the chemical changes which appeared on the surface of the samples were investigated using Fourier transform infrared spectroscopy （FTIR）. The results show that the plasma treated PVC becomes more hydrophilic with an enhanced wettability. A sharp de- crease in the water contact angle may also be a consequence of the surface texturization. The aging effect on wettability of the samples was also investigated. The results show that the effect of oxygen plasma on the surface properties of the samples is more pronounced compared with that of argon plasma.

Kinetics of Vinyl Chloride Polymerization with Mixture of Initiators

Kinetic models for the rate constants of vinyl chloride polymerization in the presence of initiator mixtures were proposed. They may be used to design the initiator recipes for the vinyl chloride polymerization with uniform rate at different temperatures at which various grades of poly(vinyl chloride) will be prepared.

Microwave Synthesis of Inulin Acetate as Potential Bio- Based Additive for Poly(Vinyl Chloride)

The paper presents the findings of an experimental study on the microwave synthesis (MW) of inulin acetateand its possible application as bio-additive in poly(vinyl chloride) (PVC). The obtained inulin acetate has beenidentified and characterized by spectroscopic methods. Advantages of the MW compared with the conventionalsynthesis were defined. In order to evaluate possible application of the product as bio-based additive forpolymers, effect of the inulin ester on PVC behavior and characteristics has been investigated by differentialscanning calorimetry (DSC) and deformation upon extension. Experimental results show that in concentrationrange up to 30.0 wt. % the inulin ester influences positively the properties of PVC causing effect similar toplasticizing one. At concentration over 30 wt.% the ester shows more specific behavior, which will be furtherinvestigated. Conclusions about potential application of MW synthesized inulin acetate as bio-based additive forPVC have been drawn.