Single phase polymer systems: CPVC/styrene copolymer alloys

Random copolymers of styrene and maleic anhydride are miscible with chlorinated poly(vinyl chloride) [CPVC] in all blended proportions. Miscibility was evident in a single glass transition temperature investigated by thermal and mechanical studies. This degree of miscibility differs from the partial miscibility obtained with PVC/styrene copolymers reported previously, where single phase morphology was present only at low blend proportions. Tailoring of physical properties such as heat resistance, flamability resistance, and processability are achieved by varying the relative proportions of CPVC and styrenic copolymer in this miscible alloy system.     

Mechanical properties of recycled PVC blends with styrenic polymers

The aim of this study is to improve the performance of blends made from recycled polyvinyl chloride (PVC), coming from credit card waste, so that these blends can be used for those applications that must fulfil some requirements with regard to mechanical properties and stability with temperature alterations. With this aim in mind, two polymers of styrenic origin have been combined: styrene acrylonitrile (SAN) and acrylonitrile butadiene styrene (ABS). These polymers are characterized by a satisfactory balance of mechanical properties and thermal stability. PVC blends with both virgin and recycled styrenic polymers have been studied throughout the entire range of compositions. The prior degradation of the recycled materials has been studied by means of Fourier transformed infrared spectroscopy (FTIR).The behavior of the observed T_g values has been analyzed using differential scanning calorimetry (DSC), and the existence of partial miscibility between the different components has been studied. The mechanical properties have been determined using tensile and Charpy impact tests. The thermal stability of the PVC blends with temperature changes has been determined using the Vicat softening temperature (VST). Finally, the fracture surface of the various blends has been analyzed using scanning electron microscopy (SEM). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2464–2471, 2006     

High‐impact toughness poly(vinyl chloride)/(α‐methylstyrene)‐acrylonitrile‐butadiene‐styrene copolymer/acrylic resin blends: Thermal properties and toughening mechanism

High impact toughness poly(vinyl chloride) (PVC)/(α‐methylstyrene)‐acrylonitrile‐butadiene‐styrene copolymer (70/30)/acrylic resin (ACR) blends were prepared. Incorporation of ACR did not play a negative role in thermal properties. The glass transition temperature, heat distortion temperature, and thermal stability remained constant as ACR content increased. With the addition of 10 phr (parts by weight per hundred parts of resin) of ACR, the impact strength increased by 20.0 times and 7.2 times compared with that of pure PVC and that of PVC/(α‐methylstyrene)‐acrylonitrile‐butadiene‐styrene copolymer (70/30) blends, respectively. However, tensile strength and flexural properties decreased. The morphology changed from domain distortions to crazing with fibrillar plastic deformation as ACR content increased. The toughening mechanism varied from “shear yielding” to “craze with shear yielding,” which depended on the content of ACR. This study presents the finding that addition of ACR drastically improved impact toughness without sacrificing any heat resistance, and the enhanced impact strength could be at the same level of supertough nylon. J. VINYL ADDIT. TECHNOL., 21:205–214, 2015. © 2014 Society of Plastics Engineers     

High heat vinyl alloys for injection molding applications

Excessive distortion, warpage, and sagging resulting from heat generation by electrical components and transporting environments has limited the penetration of PVC into high flow injection molding applications such as business machine, appliance, and electrical housings. High flow PVC formulations lose their rigidity at temperatures typical of these applications because the application temperatures are very close to the glass transition temperature (T_g) of PVC. In addition, thermal stresses built in during processing relax near the T_g of the material. Adding a glutarimide acrylic copolymer increases the T_g of PVC; consequently, raising the temperature at which the PVC/glutarimide copolymer blend loses its rigidity well above required application temperatures. This paper describes the effect of adding a glutarimide copolymer on the heat distortion properties and other physical and rheological properties important to high flow injection molding applications.     

热变形改性剂的合成及表征

用乳液聚合法合成了聚丁二烯胶乳／丙烯酸丁酯／α-甲基苯乙烯／丙烯腈／苯乙烯接枝共聚物。该共聚物在低温时显示出良好的抗冲击性能，并具有良好的耐热性能。通过自动热变形温度试验机、凝胶渗透色谱分析等手段对共聚物的热变形温度、分子量及其分布进行了表征。考查了弹性体含量对共聚体系的耐热性及抗冲击性能的影响。该热变形改性剂用于PVC共混改性，取得了较好的效果。     

Blends of poly(vinyl chloride) with α‐methylstyrene‐acrylonitrile‐butadiene‐styrene copolymer: Thermal properties,mechanical properties,and morphology

Binary blends of poly(vinyl chloride) (PVC) with α‐methylstyrene‐acrylonitrile‐butadiene‐styrene copolymer (AMS‐ABS) were prepared via melt blending. A single glass transition temperature (T_g) was observed by differential scanning calorimetry, thus indicating that PVC is miscible with the α‐methylstyrene‐acrylonitrile‐styrene in AMS‐ABS. The results from attenuated total reflection Fourier transform infrared spectra indicated that specific strong interactions were not available in the blends. With increasing amounts of AMS‐ABS, both heat distortion temperature and thermal stability were increased considerably. With regard to mechanical properties, flexural and tensile properties decreased with increasing AMS‐ABS content. A synergism was observed in impact strength. The morphology of both impact‐fractured and tensile‐fractured surfaces, observed by scanning electron microscopy, correlated well with the mechanical properties. It is suggested that there was a transition of fracture mechanisms with the changing composition of the binary blends—from shear yielding for blends rich in PVC to cavitation for blends rich in AMS‐ABS. J. VINYL ADDIT. TECHNOL., 19:1–10, 2013. © 2013 Society of Plastics Engineers     

Dynamic mechanical properties and morphology of styrene-divinylbenzene copolymer/poly(vinyl chloride) systems. (II). Effect of polymerization temperature

Effect of polymerization temperature on the phase-separated structure of the composite materials [P(St-DVB)/PVC systems] prepared by copolymerization of styrene (St) and divinylbenzene (DVB) in the presence of fine poly(vinyl chloride) (PVC) powder was studied by electron microscopy and dynamic mechanical test. P(St-DVB)/PVC systems have the two-phase nature with a styrene-divinylbenzene copolymer as the continuous phase [P(St-DVB) phase) and a PSt/PVC composite as the dispersed phase (PSt-PVC phase), in which PSt penetrates into the PVC domain. The crosslinking density of the P(St-DVB) phase is larger than that estimated from the recipe in the feed, suggesting that there exists a difference of the diffusion constants of styrene and divinylbenzene into the PVC particles on the paste formation and the polymerization process. The changes of the phase-separated structure of P(St-DVB)/PVC systems polymerized at various temperatures are also explained on the basis of the difference between the diffusion behavior of styrene and that of divinylbenzene into fine PVC particles at these temperatures.     

Adhesion of styrenic triblock copolymers to miscible blends of polystyrene and a phenylene ether copolymer

The adhesion of a triblock copolymer having short styrene end-blocks and a hydrogenated mid-block to a polystyrene containing substrate was studied using both lap shear and peel test methods. The two approaches gave very similar results. Within the limits examined, the adhesive bond strength did not depend significantly on bonding temperature or time. However, the adhesive strength did increase substantially as a phenylene ether copolymer or PEC, essentially poly(phenylene oxide), was added to the substrate. This effect is believed to be the result of the exothermic mixing of PEC with polystyrene that causes an additional driving force, other than combinatorial entropy, for interpenetration of segments of the substrate and the styrenic phase of the block copolymer at the interface. Attempts to use a block copolymer having longer styrenic segments resulted in adhesive bond strengths so large that cohesive failure occurred first.     

Studies of poly(2,6-dimethyl-1,4-phenylene oxide blends): I. Copolymers of styrene and maleic anhydride

Blends of poly(2,6-dimethyl-l,4-phenylene oxide) and copolymers of styrene and maleic anhydride have been characterized by differential scanning calorimetry, dynamic mechanical analysis, and tensile measurements. Differential scanning calorimetry measurements indicate a single broadened glass transition for each blend of a 8 wt.% maleic anhydride copolymer, P(S-8MA), but two glass transitions when the copolymer composition is 14 wt.% MA, P(S-14MA). The glass transition temperatures of the former blends follow a sigmoidal dependence on blend composition, which is explained on the basis of evidence for phase separation from their dynamic mechanical tan 8 spectra. Tensile moduli of both blends reach a maximum at intermediate blend compositions; however, large-strain mechanical properties are highly dependent on blend compatibility and the method of sample preparation. The more homogeneous P(S-8MA) blends yield at low-to-intermediate copolymer compositions but fail in a brittle mode at higher compositions. All heterogeneous P(S-14MA) blends undergo brittle failure, but comparison of experimetal values of ultimate stress and strain with predictions from empirical relationships developed for composites indicate that interfacial adhesion is strong in these systems.     

Improvement in the heat resistance of poly(vinyl chloride) profile with styrenic polymers

The styrenic polymers poly(α‐methylstyrene‐acrylonitrile) (α‐MSAN) and poly(acrylonitrile‐butadiene‐styrene) (ABS) and (three types) were used to improve the heat resistance of poly(vinyl chloride) (PVC). The glass transition temperature (T_g) and miscibility were analyzed by dynamic mechanical thermal analysis (DMTA). Effects of composition on heat distortion temperature (HDT) were investigated with the different styrenic polymers. Other physical properties such as mechanical properties and melt flow rate (MFR) were also determined. Morphology was observed by scanning electron microscopy (SEM) in order to support the mechanical property results. The PVC was miscible with α‐MSAN but partially miscible with the ABS series, and α‐MSAN was much more effective in enhancing the T_g and HDT of rigid PVC than the ABS series as for mechanical properties, the addition of α‐MSAN could improve the tensile strength, bending strength, and bending modulus but decrease the impact strength of the materials compared with the addition of the ABS series. Improvement in processability was observed in the MFR results with the addition of the styrenic polymers. On the basis of all the properties, the formulation with an α‐MSAN content of 30 phr (parts per hundred parts of resin) was superior for heat‐resistant PVC profile. The HDT of PVC could be increased from 76.9°C to 85.4°C (measured under the maximum bending stress of 0.45 MPa) and combined with good mechanical properties and processability by the addition of 30 phr of α‐MSAN. Also, a heat‐resistant PVC profile was successfully fabricated. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Dynamic mechanical properties and morphology of styrene–divinylbenzene copolymer/poly(vinyl chloride) systems

The morphology and dynamic mechanical properties of the composite materials [P(St–DVB)/PVC systems], prepared by copolymerization of styrene and divinylbenzene in the presence of fine PVC powder, were studied by electron microscopy and the dynamic mechanical test. The composite material (PSt/PVC composite), prepared by the polymerization of styrene in the presence of fine PVC powder, contains grafting polystyrene (PSt) onto PVC, which improves the compatibility of PSt and PVC. This result also suggests the formation of the graft copolymer of styrene–divinylbenzene onto PVC in the P(St-DVB)/PVC systems. Electron microscopy and the dynamic mechanical test indicate that P(St-DVB)/PVC systems have the two-phase nature with a styrene–divinylbenzene copolymer as the continuous phase [P(St-DVB) phase] and a PSt/PVC composite as the dispersed phase (PSt-PVC phase), in which PSt penetrates into the PVC domain. The domain size of the dispersed phase is 0.5–2μ. The crosslinking density of the P(St-DVB) continuous phase is larger than that estimated from the recipe. One of the reasons for this is ascribed to the difference of the diffusion constants of styrene and divinylbenzene into the PVC particles on the paste formation and polymerization process.     

Epoxy-based divinyl ester resin/styrene copolymers: Composition dependence of the mechanical and thermal properties

Epoxy-based divinyl ester resins (DVER) were obtained by reacting diglycidyl ether of bisphenol A (DGEBA) with methacrylic acid (MA) and characterized by FTIR and ¹H-NMR spectroscopies and gel permeation chromatography (GPC). The densities and viscosities of the DVER in styrene (S) solutions were measured at different temperatures, 25, 40, and 60°C and compositions, 3.4 to 100% by weight of styrene. Dynamic mechanical measurements (DMA) and differential scanning calorimetry (DSC) were used to determine the glass transition temperatures of the homopolymers and the DVER/S copolymers: 20, 40, 60, and 80% by weight of styrene. The values obtained are in the range limited by the homopolymers glass transition, 100°C for polystyrene and 173°C for the cured DVER. The data were well fitted if two contributions to the glass transition are taken into account: the “linear copolymer” contribution (Fox eq.) and the “crosslinking” contribution (Nielsen model). Uniaxial static compression tests were carried out to determine the modulus, yield stress, and ultimate stress in samples with different compositions. All the mentioned properties decrease with an increase in the styrene concentration in the final copolymer. It was found that the volumetric contraction during curing increases with styrene concentration. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1059–1066, 1997     

Toughening modification of poly(vinyl chloride)/ α‐methylstyrene‐acrylonitrile‐butadiene‐styrene copolymer blends via adding chlorinated polyethylene

In this study, poly (vinyl chloride) (PVC)/α‐methylstyrene‐acrylonitrile‐butadiene‐styrene copolymer (AMS‐ABS) (70/30)/chlorinated polyethylene (CPE) ternary blends was prepared. With the addition of CPE, it did not exert a negative influence in both the glass transition temperature and heat distortion temperature. Thermogravimetric analysis showed that addition of CPE did not play a negative role in the thermal stability. With regard to mechanical properties, high toughness was observed combined with the decrease in tensile strength and flexural strength. With the addition of 15 phr CPE, the impact strength increased by about 21.0 times and 8.5 times in comparison with pure PVC and PVC/AMS‐ABS (70/30) blends, respectively. The morphology correlated well with the impact strength. It was also suggested from the morphology that shear yielding was the major toughening mechanisms for the ternary blends. And there existed a change in the fibril structures that are observed in scanning electron microphotographs. Our present study shows that combination of AMS‐ABS and CPE improves the toughness without sacrificing the heat resistance, and the value of notched impact strength can be enhanced to the same level of super‐tough nylon. POLYM. ENG. SCI., 54:378–385, 2014. © 2013 Society of Plastics Engineers     

Melt rheological properties of polypropylene/SEBS (styrene–ethylene butylene–styrene block copolymer) blends

Study of melt rheological properties of the blends of polypropylene (PP) with styrene–ethylene butylene–styrene block copolymer (SEBS), at blending ratios 5–20% SEBS, is reported. Results illustrate the effects of (i) blend composition and (ii) shear rate or shear stress on melt viscosity and melt elasticity and the extrudate distortion. In general, blending of PP with SEBS results in a decrease of its melt viscosity, processing temperatures, and the tendency of extrudate distortion. However, the properties depend on blending ratio. A blending ratio around 5–10% SEBS seems optimum from the point of view of desirable improvement in processability behavior.     

Properties of random and block copolymers of butadiene and styrene. II. Melt flow

Flow curves, log (rate of shear) versus log (shear stress), as functions of temperature were obtained for several butadiene-styrene copolymers of fixed (25%) styrene content, differing in monomer sequence distribution. A random copolymer of constant composition along the polymer chain and narrow molecular weight distribution (MWD) exhibited behavior similar to linear, narrow MWD polybutadienes; the flow was Newtonian at low shear stresses, and the flow curves for various temperatures were accurately superimposable by a shift along the log (shear rate) axis. In a random copolymer varying in composition along the polymer chain, non-Newtonian behavior was more pronounced, and temperature-shear rate superposition did not succeed, a trend further perpetuated in copolymer of a single long styrene block sequence. The latter resemble branched polymers, as would be expected from association of the styrene blocks. With two styrene blocks, association produces network structures below the glass transition of polystyrene with consequent loss of flow. Disruption of these associations above T_g (styrene) imparts the greatest thermoplasticity to these elastomers. There is evidence, however, that some of the associations persist at temperatures well in excess of T_g (styrene).     

PSA performances and viscoelastic properties of SIS‐based PSA blends with H‐DCPD tackifiers

Hotmelt pressure sensitive adhesives (PSAs) usually contain styrenic block copolymers like styrene–isoprene–styrene (SIS), SBS, SEBS, tackifier, oil, and additives. These block copolymers individually reveal no tack. Therefore, a tackifier is a low molecular weight material with high glass transition temperature (T_g), and imparts the tacky property to PSA. The SIS block copolymer with different diblocks was blended with hydrogenated dicyclopentadiene (H‐DCPD tackifier), which has three kinds of T_g. PSA performance was evaluated by probe tack, peel strength, and shear adhesion failure temperature. PSA is a viscoelastic material, so that its performance is significantly related to the viscoelastic properties of PSAs. We tested the viscoelastic properties by dynamic mechanical analysis and the thermal properties by differential scanning calorimeter to investigate the relation between viscoelastic properties and PSA performance. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 2839–2846, 2006     

Untersuchungen an kautschukmodifiziertem PVC

The composition-morphology-property relationships are investigated for a series of ABS-, MBS- and AMBS-graft copolymer blends with PVC. The dispersibility of the graft copolymers in PVC improves with increasing grafting levels, while both impact resistance and tendency to stress whitening decrease. With respect to particle size, an optimum in the properties is found for particles of 200 nm. The grafting composition in ABS polymers giving the best results is a 75 S/25 AN copolymer, which is highly compatible with PVC. This high compatibility coincides with the good agreement between the solubility parameters for this SAN copolymer (δ = 9,8) and PVC (δ = 9,6). In MBS polymers increasing styrene levels lead to more transparent blends with PVC because of better matching of the refractive indices. However, impact strengths decrease at the same time because of deteriorating compatibility. Methyl methacrylate, having just the opposite effects to styrene, can be favourably used in combination with styrene or SAN by a stepwise addition of the graft monomers which is shown to result in optimum properties for MBS or AMBS polymers. Electron micrographs of the stress whitened areas reveal that the degree of crazing is negligible in comparison to other rubber modified thermoplastics. Instead of crazes, many cavities within the graft copolymer particles are found which correlate in size and frequency with the extent of stress whitening. Measurements of the density decrease in the stress whitened areas agree quantitatively with evaluations of the volume increase determined from the changes of the particles sizes in the electron micrographs. An analysis of the polymerization of the scattered light shows that shear bands or birefringence effects can be excluded as the cause of stress whitening. Based on the direct observation of the stress whitened areas and on the dependence of the scattering on wavelength and angle, the light scattering effects must be caused by the accumulation of the cavitiesin bandlike zones. These zones mark the otherwise invisible shear bands occurring on strong deformations of the PVC matrix. The initiation of the shear bands is facilitated by the incorporation of the graft copolymer particles which in this way enhance the impact strength of PVC.     

Synthesis and property behavior of dioctyl phthalate plasticized styrene–acrylate particles by Shirasu porous glass emulsification and subsequent suspension copolymerization

Two‐phase model styrene–acrylate copolymers were synthesized with a soft phase consisting of methyl acrylate, butyl acrylate, and butyl methacrylate. Besides the styrenic copolymers, copolymers containing a hard phase of methyl methacylate and methyl acrylate were also synthesized. Comonomer droplets with a narrow size distribution and fair uniformity were prepared using an SPG (Shirasu porous glass) membrane having pore size of 0.90 μm. After the single‐step SPG emulsion, the emulsion droplets were composed mainly of monomers, hydrophobic additives, and an oil‐soluble initiator, suspended in the aqueous phase containing a stabilizer and inhibitor. These were then transferred to a reactor, and subsequent suspension polymerization was carried out. Uniform copolymer particles with a mean diameter ranging from 3 to 7 μm, depending on the recipe, with a narrow particle size distribution and a coefficient of variation of about 10% were achieved. Based on the glass‐transition temperatures, as measured by differential scanning calorimetry, the resulting copolymer particles containing a soft phase of acrylate were better compatibilized with a hard phase of methyl methacrylate than with styrene with dioctyl phthalate (DOP) addition. Glass‐transition temperatures of poly(MMA‐co‐MA) particles were strongly affected by the composition drift in the copolymer caused by their substantial difference in reactivity ratios. Incorporation of DOP in the copolymer particles does not significantly affect the glass‐transition temperature of MMA‐ or MA‐containing copolymer particles, but it does affect the St‐containing copolymer and particle morphology of the copolymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3037–3050, 2003     

Grafting of poly(vinyl chloride) and polypropylene with styrene in a supercritical CO2 solvent medium: Synthesis and characterization

Graft copolymerization of styrene onto poly(vinyl chloride) (PVC) and polypropylene (PP) was carried out in a supercritical CO₂ medium using AIBN as a free radical initiator. The supercritical CO₂ medium served as a reaction medium in addition to being a solvent for the styrene monomer and the free radical initiator. The reaction temperature and pressure were kept above the critical points of the solvent‐monomer mixture to form a homogeneous single‐phase medium. The resulting graft copolymers were characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR) techniques. The weight percent of grafting was determined using IR absorbance ratio technique. TGA results showed that the thermal stabilily of grafted copolymer of PVC was better than that of PVC, while grafted copolymer of PP had poorer thermal stability than PP. DSC results showed that glass transition temperatures (T_g's) of the grafted copolymers were higher than those of the starting polymers PVC and PP. The presence of polystyrene attached to the backbone polymer was confirmed by ¹H NMR and ¹³C NMR analyses.     

Some considerations concerning the dynamic mechanical properties of cured styrene–butadiene rubber/polybutadiene blends

The dynamic mechanical response of several binary mixtures of a styrene–butadiene copolymer and high cis‐polybutadiene has been studied. The loss tangent and shear modulus were measured with a free damping torsion pendulum at temperatures between 143 and 343 K in argon atmosphere. From the loss tangent data the glass transition temperature of each sample was evaluated. The results can be represented by the Fox equation that relates the glass transition temperature of the blend with that of constituent polymers. The influence in the loss tangent data of the crystallization of the high cis BR used in the blend is discussed. A study of the separation of the crystalline and amorphous parts in the polybutadiene using the storage modulus data is presented. Finally, the loss of crystallinity at different contents of SBR in the blend is analysed using the dynamic mechanical data. © 2000 Society of Chemical Industry