Poly (alpha-methylstyrene) as a processing aid for rigid poly (vinyl chloride)

Poly (alpha-methylstyrene) (PAMS) is a new approach to process improvement in rigid poly (vinyl chloride) (PVC)—the use of a low molecular weight polymer as a process aid. PAMS can reduce fusion time, melt viscosity and improve heat stability of rigid PVC compounds. The reduced melt viscosity allows the addition of fillers to PVC without adverse effect on extrusion rates. This polymer also improves the resistance to melt fracture and shear “burning” at high shear rates. When used within the optimum concentration range, physical properties such as tensile strength, Izod impact and heat distortion are maintained. In addition, PAMS gives, improved production rates in both pipe extrusion and injection molding processes without sacrifice in properties.     

Rheological behavior of poly(vinyl chloride) mixtures. I. Viscous behavior

An investigation of the viscous flow properties of mixtures of low molecular weight materials, such as lubricants and plasticizer, with PVC has been carried out. In all examples studied the PVC exhibited a discontinuity in flow with increasing temperature. This was interpreted as a phase change in the melt. A diffusion fractionation of the low molecular weight species was used to rationalize the shear rate dependent viscous behavior of these melts.     

硬质PVC挤出发泡材料的塑化性能研究

采用Haake转矩流变仪测定了挤出发泡PVC混合料的恒温、升温熔融塑化性能，结果表明：随着PVC树脂聚合度增加，塑化时间和加工转矩增加；随着ACR加工助剂用量和分子质量的增加，塑化时间缩短，转矩增加；ACR抗冲改性剂具有类似ACR加工助剂的塑化改良行为；添加填充剂碳酸钙促进PVC熔融塑化；ADC发泡剂可延缓PVC混合料的塑化速率、提高熔体粘度，添加发泡剂NaHCO3将大大延缓混合料的塑化速率。     

Mechanical and thermal properties of poly(vinyl chloride)/α‐methyl‐styrene‐acrylonitrile blends prepared by melt extrusion

In this article, we have examined the physical and mechanical properties of poly(vinyl chloride) (PVC)/α‐methyl‐styrene‐acrylonitrile (αMSAN; 31 wt % AN concentrations) blends with different blend ratios. And, we also examined the effect of the molecular weights of PVC on the miscibility and material properties of the blends prepared by melt extrusion blending. Our results showed that the PVC/αMSAN blends have good processing properties and good miscibility over all blend ratios because of the strong interaction between PVC and αMSAN. And, the blends showed enhanced mechanical and thermal properties. In addition, high molecular weight PVC showed reasonable processability when melt blended with αMSAN, which resulted in enhanced mechanical and physical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of molecular weight and molding conditions on the replication of injection moldings with micro‐scale v‐groove features

Injection molded optical plastic parts require accurate replication of micro‐scale features. The effects of melt viscosity and molding conditions on replication of microscopic v‐groove features in injection molded parts were examined for PC with different molecular weight. The micro‐scale feature size was a continuous v‐groove with 20 μm in depth and 50 μm in width. For injection molding conditions, melt temperature, mold temperature, injection velocity and holding pressure were varied in three levels. As the result, the mold temperature had significantly affected replication for all polymers with different molecular weight. Additionally, the molding conditions that lower melt viscosity led to improved replication. In the case of polymer with high molecular weight, the viscosity decreased with increasing melt temperature. It has been found that high replication of micro‐scale features could be achieved by higher mold temperature and higher melt temperature even with high viscosity PC. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

聚甲基丙烯酸甲酯包覆纳米CaCO3改性聚氯乙烯研究

研究了聚甲基丙烯酸甲酯(PMMA)包覆纳米CaCO3复合粒子填充聚氯乙烯(PVC)复合材料的加工塑化和力学性能，并与未改性纳米CaCO3的改性效果进行比较。结果发现，填充纳米CaCO3使PVC平衡扭矩和平衡熔融温度均会有所提高，填充未改性碳酸钙增加更大，填充PMMA包覆CaCO3使材料冲击性能提高的幅度大于填充未改性纳米CaCO3，而拉伸强度下降幅度较小。当PMMA包覆CaCO3填充量为8％时缺口冲击强度增加到未改性PVC的194％。冲击缺口断面形态分析表明，采用PMMA包覆CaCO3时，纳米CaCO3在PVC基体中分散均匀、团聚少。     

Properties of glass‐filled thermoplastic polyesters

The thermal, mechanical, and rheological properties of glass‐filled poly(propylene terephthalate) (GF PPT) were compared to glass‐filled poly(butylene terephthalate) (GF PBT). The impetus for this study was the recent commercial interest in PPT as a new glass‐reinforced thermoplastic for injection‐molding applications. This article represents the first systematic comparison of the properties of GF PPT and GF PBT in which differences in properties can be attributed solely to differences in the polyester matrices, that is, glass‐fiber size and composition, polymer melt viscosity, nucleant content and composition, polymerization catalyst composition and content, and processing conditions were kept constant. Under these controlled conditions, GF PPT showed marginally higher tensile and flexural properties and significantly lower impact strength compared to GF PBT. The crystallization behavior observed by cooling from the melt at a constant rate showed that GF PBT crystallized significantly faster than did GF PPT. Nucleation of GF PPT with either talc or sodium stearate increased the rate of crystallization, but not to the level of GF PBT. The slower crystallization rate of GF PPT was found to strongly affect thermomechanical properties of injection‐molded specimens. For example, increasing the polymer molecular weight and decreasing the mold temperature significantly increased the modulus drop associated with the glass transition. In contrast, the modulus–temperature response of GF PBT was just marginally influenced by the polymer molecular weight and was essentially independent of the mold temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 889–899, 1999     

Impact strength and morphology in poly(vinyl chloride) window profiles –relationship with gelation level

Abstract

The impact strength resistance of extruded PVC window profiles is a result of the combined effects of the interaction of their intrinsic material properties and processing/fabrication variables. Intrinsic variables include all the components of the formulation, such as the type and level of impact modifier and filler. As such, an appropriate level of toughness can be achieved by selecting the type and amount of rubber particles present in the matrix. However, the impact properties of poly(vinyl chloride) (PVC) profiles are also drastically affected by the thermal and shear history of the PVC matrix. The effect of processing on mechanical properties is explored by altering the temperature profile set on the extruder, and by varying the shear heating phenomena using different lubrication balances. The gelation level of any PVC formulation tends to increase with the level of work on the material, i.e. with increased melt temperature and shear history. The study reported in the present paper is intended to quantify the degree of fusion of the primary crystallites as a function of the melt temperature, and show the dependence of the toughness of the extruded profiles on the resulting free volume. Free volume in PVC extruded profiles depends on the degree of the gelation of the matrix and also on the cooling rate of the melt. As extrusion output increases, cooling of the melt is so fast that polymer chains have much less time to recover and reach a state of minimum entropy. Upon physical aging, the free volume tends to decrease. The reduction in free volume changes the non-equilibrium state of the glass phase, thus reducing the toughness of the material, and causing embrittlement under certain test conditions.

Finally, the effect of filler level and type of impact modifier (two intrin sic variables) on the impact strength of extruded profiles with various levels of free volume are presented.     

Enhanced toughness of multilayer graphene‐filled poly(VInyl chloride) composites prepared using melt‐mixing method

In order to improve toughness of rigid poly(vinyl chloride) (PVC), we prepared multilayer graphene (MLG) filled PVC composites through conventional melt‐mixing methods by taking advantages of easy dispersion and high flexibility of graphene. Microstructure, static, and dynamic mechanical properties of the MLG/PVC composites were investigated in details. We found that a small amount of MLG loadings (0.36 wt%) could greatly increase tensile fracture toughness and impact strength of the MLG/PVC composites, which is mainly attributed to high flexibility of the crumpled MLG throughout PVC matrix. Moreover, the presence of MLG can weaken intermolecular interactions and improve segmental motion of PVC chains, consequently resulting in low glass transition temperature and high toughness of the MLG/PVC composites. By virtue of its enhanced toughness and easy operation, the MLG/PVC composites show great potential to be used as high‐performance composites in many fields. POLYM. COMPOS., 38:138–146, 2017. © 2015 Society of Plastics Engineers     

Synthesis of amphiphilic PVC‐b‐poly(hydroxypropyl acrylate) (PHPA)‐b‐PVC block copolymers with low PHPA contents and different molecular weights by (Single Electron Transfer)—(Degenerative Chain Transfer) living radical polymerization

The aim of this work was to synthesize new amphiphilic block copolymers, based on poly(vinyl chloride) (PVC) and containing poly(hydroxypropyl acrylate) (PHPA), by using the controlled/“living” radical polymerization (CLRP) method. Various block copolymers containing a small proportion of PHPA were prepared, each having a different molecular weight. The technique used was the same as that employed in the production of commercial PVC made by free‐radical polymerization. The materials were characterized in terms of their molecular structure, morphology, particle size, and surface and thermal properties. The CLRP preparation of block copolymers that are based on PVC and have low contents of other monomer units opens the possibility of synthesizing new materials whose properties are close to those of PVC but have new properties that may considerably enhance their performance. The incorporation of small amounts of PHPA into PVC block copolymers provided greater surface hydrophilicity and improved thermal stability while maintaining relevant processing properties, such as particle size and average molecular weight, so that they close to those of conventional PVC homopolymers. J. VINYL ADDIT. TECHNOL., 19:157‐167, 2013. © 2013 Society of Plastics Engineers     

Effects of poly(butylene succinate) and ultrafine wollastonite on the physical properties of plasticized poly(vinyl chloride)

In this study, diisononyl phthalate (DINP), a conventional plasticizer of poly(vinyl chloride) (PVC), was partially replaced by a polymeric plasticizer, poly(butylene succinate) (PBS), in order to reduce the leaching out of low‐molecular‐weight plasticizer from the plasticized PVC. Samples were prepared by melt mixing on a two‐roll mill followed by compression molding into a 3‐mm thick sheet. The DINP/PBS‐plasticized PVC provides a dose‐dependent increase in the tensile properties (tensile strength, Young's modulus, and elongation at break), tear strength, and thermal stability, as compared with the DINP‐plasticized PVC. According to the overall properties, PVC plasticized with 10/30 phr (parts by weight per hundred parts of resin) DINP/PBS was selected for preparing composites with varied loadings of an ultrafine wollastonite (particle size of 1,200 mesh). Their tensile properties, tear strength, thermal stability, and morphology were evaluated and compared with the 40 phr of DINP‐plasticized PVC composites. The results showed an increase in the Young's modulus and thermal stability but a decrease in the tensile strength, elongation at break, and tear strength of either 40 phr of DINP‐ or 10/30 phr of DINP/PBS‐plasticized PVC composites. Therefore, the products may be useful where the dimensional and thermal stability of the plasticized PVC are needed. J. VINYL ADDIT. TECHNOL. 21:220–227, 2015. © 2014 Society of Plastics Engineers     

Evaluating effects of biobased 2,5‐furandicarboxylate esters as plasticizers on the thermal and mechanical properties of poly (vinyl chloride)

We synthesized 2,5‐furandicarboxylate esters [i.e., dibutylfuran‐2,5‐dicarboxylate, diisoamylfuran‐2,5‐dicarboxylate, and di(2‐ethylhexyl)furan‐2,5‐dicarboxylate] and investigated their potential application as plasticizers of commercial poly(vinyl chloride) (PVC) products. Fourier transform infrared analysis, mechanical tests, scanning electron microscopy investigation, differential scanning calorimetry analysis, dynamic mechanical thermal analysis, thermogravimetric analysis (TGA), melt flow rate (MFR) measurement, and plasticizer migration measurements were used to the evaluate the comprehensive properties of the blended products. The results of the tensile tests demonstrate that the blends exhibited antiplasticization and flexible plastic characteristics at 10 and 50 phr in PVC, respectively. Moreover, flexural and impact test data indicate that the three types of blends exhibited a similar tendency: the hardness decreased continuously as the amount of plasticizer increased. Their morphology indicated that all of the plasticizers had good compatibility with PVC. The resulting glass‐transition temperature of the investigated plasticizers was lower than that of pure PVC, and reduction was largest for the plasticizer with the highest molecular weight. TGA revealed that the thermal degradation of blended polymers occurred in three stages and that all of the blends were stable up to 180°C. Finally, the MFRs of all of the specimens indicated that the addition of a higher concentration of lower molecular weight biobased esters resulted in improved fluidity, but these compounds migrated more easily from the blends. Hence, 2,5‐furandicarboxylic acid derived from biomass has potential as a plasticizer. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40938.     

Effects of poly(methyl methacrylate-co-n-butyl acrylate) on the properties and processing behavior of poly(vinyl chloride)

Random copolymers of methyl methacrylate/n-butyl acrylate with a BA content of 0–50% and M?_v = 0.16–4.04 × 10⁶ were synthesized and evaluated as a processing aid (PA) for poly(vinyl chloride) (PVC). Their effects on the processability and properties of PVC were investigated with respect to the composition, molecular weight, and the amount of the copolymer added. It was found that the fusion rate of PVC could be improved (i) by increasing the amount of the copolymer used, (ii) by increasing the butyl acrylate content in the copolymer, and (iii) by lowering the molecular weight of the copolymer. The effect of molecular weight, composition, and amount of copolymer on the ultimate mechanical properties of PVC was investigated. The presence of copolymer did not affect the impact strength. However, the tensile strength and elongation at break were improved, particularly at high temperature (125°C). It was also found that the “plate out” phenomenon of PVC could be significantly reduced in the presence of the processing aid.     

Rheology of poly(vinyl chloride) blends

PVC/EVA blends were studied with an extrusion plastometer in order to examine the effect of EVA on the processability of PVC. The melt flow of PVC/EVA blends containing from 4 to 30 weight percent EVA follows a simple power law between 160 and 180°C. EVA reduced the melt viscosity and enhanced processability. Blends of PVC and EVA were morphologically incompatible. The molecular weight of extruded PVC in the blends was unchanged.     

Formation mechanism of microvoids and microcracks of poly(vinyl chloride) under an artificial aging environment

Degradation behaviors of both the unplasticized and plasticized poly(vinyl chloride) (UPVC and PPVC) under an artificial accelerating aging condition were extensively studied. The dependence of mechanical properties, average molecular weight (MW), and surface morphology of the earlier PVC on aging time was investigated by tensile tests, gel penetrate chromatogram (GPC), and scanning electron microscope (SEM), respectively. Fourier transform infrared and ultraviolet (UV)–visible spectroscopy were used to evaluate the probable formation of both the oxygen-containing groups and the conjugated sequences during aging. The results reveal that UPVC is much easier to be degraded than PPVC under the same testing conditions. The irradiated surface is detected to change from an even topology into a rough topology initially, and then follows the appearance of many voids even cracks in the SEM morphology. During the aging process, oxygen-containing groups and conjugation of PVC molecular chains around the cracks are observed, and noticeably increase with aging time. However, visible difference of the corresponding MWs of PVC before and after aging is not detected. Moreover, a novel degradation mechanism nearly related to the formation of microvoids and microcracks based on the cohesion energy of groups along PVC molecular chains is developed and semiquantitatively discussed. It is detected that the formation of microvoids and microcracks is attributed to both the thermodynamic changes of PVC backbone during the aging and the aggregation of oxygen-containing groups with relatively large volumes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of poly(epichlorohydrin) on the thermal and mechanical properties of poly(vinyl chloride)

Five kinds of polyepichlorohydrin (PECH) of different molecular weights were synthesized and characterized by gel permeation chromatography (GPC). Mechanical blending was used to mix PECH and poly(vinyl chloride) (PVC) together. The blends of different PVC/PECH ratios were characterized by thermogravimetric analysis (TGA), tensile tests, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). TGA results show the thermal stability of PVC/PECH blends is desirable. Tensile tests indicate elongation at break is raised by increasing both the amount and the molecular weight of PECH. DSC is used to determine the glass transition temperature of PECH, and a quite low T_g is obtained. DMA results indicate that PECH has a perfect compatibility with PVC, when PECH concentration is below 20 wt %. There is only one peak in each tan δ curve, and the corresponding T_g decreases as PECH amount increases. However, above 20 wt %, phase separation takes place. The molecular weight of PECH also has a great influence on the glass transition temperature of the blends. This study shows that PECH is an excellent plasticizer for PVC, and one can tailor the glass transition temperature and tensile properties by changing the amount and the molecular weight of PECH. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of thermal degradation on the impact properties of PVC compounds

An instrumented drop weight impact test was used to study the effect of thermal degradation on the impact properties of PVC compounds. The impact resistance of the aged compounds related well with their weight loss and hence, with thermal degradation. Each compound showed a specific weight loss percentage that correlated with a 50% loss in its impact properties (failure point), irrespective of the aging temperature. The results were also used to estimate a thermal index (TI) of each compound in a rapid and reliable way.     

The effects of processing parameters on the tensile properties of weld lines in injection molded thermoplastics

Weld or knit lines result wherever two or more polymer flow fronts unite. This results in a region of a different level of molecular entanglements than the bulk material. Consequently, weld regions have been observed to have inferior mechanical properties compared to the bulk. Although this phenomenon occurs in almost all the commercially important polymer processes, there has been little systematic investigation. The effects of melt temperature, mold temperature, injection speed and injection pressure on the tensile properties of commercial grades of polystyrene (GPS), high impact polystyrene (HIPS) and polypropylene (PP) are examined. The most important processing parameters seemed to be melt and mold temperature; injection speed and pressure had little effect on the tensile properties of any of the samples. A higher melt temperature increased both the strain and stress at break considerably in GPS. In HIPS increased melt temperature increased only the elongation to break substantially. Increased mold temperature improved the stress and elongation to break in GPS but not as much as melt temperature. Polypropylene showed improved weld yield strength with increased mold temperature. Under the conditions examined, injection pressure and injection speed showed no effect on the tensile properties of any of the materials investigated.     

Analysis of low‐density polyethylene‐g‐poly(vinyl chloride) copolymers formed in poly(vinyl chloride)/low‐density polyethylene melt blends with gel permeation chromatography and solid‐state 13C‐NMR

Gel permeation chromatography (GPC) and solid‐state ¹³C‐NMR techniques were used to analyze the structural changes of poly(vinyl chloride) (PVC) in blends of a low‐density polyethylene (LDPE) and PVC during melt blending. The GPC results showed that the weight‐average molecular weight (M_w) of PVC increased with LDPE content up to 13.0 wt % and then decreased at a LDPE content of 16.7 wt %, whereas the number‐average molecular weight remained unchanged for all of LDPE contents used. The ¹³C‐NMR results suggest that the increase in M_w was associated with the formation of a LDPE‐g‐PVC structure, resulting from a PVC and LDPE macroradical cross‐recombination reaction during melt blending. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3167–3172, 2004     

Soil burial degradation of new bio‐based additives. Part I. Rigid poly(vinyl chloride) films

Commercial sunflower oil was epoxidized, and the epoxidized sunflower oil (ESO) was used as a thermal stabilizer for poly(vinyl chloride) (PVC). Rigid formulations stabilized with ESO as a new stabilizer and epoxidized soybean oil (ESBO) as a commercial stabilizer for comparison were prepared. The aging of the PVC samples was investigated in landfill soil for 24 months. The structure modifications of the polymer were followed by Fourier transform infrared spectroscopy (FTIR). Furthermore, the variations of density and mechanical properties (tensile and Shore D hardness) were considered. The variations of the mass of the samples, the glass transition temperature (T_g), the molar mass distribution, and the weight loss were followed as a function of time of soil burial. The soil burial test showed the loss of additives by migration and biodegradation that led to the modification of density, mechanical properties, molar mass distribution, and weight loss of the PVC samples. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers