聚氯乙烯木塑复合材料加速老化性能的研究

对4种聚氯乙烯木塑复合材料进行加速老化试验,随着老化时间增加,木塑复合材料铅盐体系冲击强度和拉伸强度的保持率最高。     

The enhancement performances of cotton stalk fiber/PVC composites by sequential two steps modification

In the present study, the cotton stalk fiber (CSF) was modified by sequential two steps of alkali and copper ethanolamine (CE) solution treatment. The unmodified and modified CSF/poly(vinyl chloride) (CSF/PVC) composites were prepared. The mechanical and physical performances of the various CSF/PVC composites were studied comparatively. By the modification of CE solution, all the tensile strength, tensile modulus, impact strength, water resistance, and heat distortion temperature of samples were enhanced continuously. The sample with comprehensive properties was obtained using 2% concentration of CE. The composites were also prepared with different CSF content. By increasing the CSF loading, all the tensile strength, elongation at breakage, tensile modulus, and heat distortion temperature of samples were enhanced. The existence of copper on the surface of CSF improved the thermal stability of the CSF/PVC composites. Water retention value, oil retention value, and scanning electron microscope were applied to reveal the components and microscopic change of the composites. The possible reaction mechanism of modification was proposed based on the experimental results and according to the previous literature. This method reported here may provide a new way for the fabrication of CSF/PVC composite in engineering applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46090.     

黏土结构对聚氯乙烯/黏土复合材料性能的影响

用两种不同结构的黏土伊利石和海泡石作为填料填充到聚氯乙烯(PVC)树脂中,研究黏土结构对PVC性能的影响。结果表明:黏土的结构不同,对PVC的性能影响也存在明显差异。伊利石对提高PVC的拉伸强度优于海泡石;而海泡石对提高PVC的冲击强度优于伊利石。伊利石提高了PVC的弯曲强度,对弯曲模量的影响不大;而海泡石降低了PVC的弯曲强度,但明显加大了PVC的弯曲模量。海泡石对提高PVC的热变形温度优于伊利石。     

Changes in properties of rigid PVC during weathering

Changes in properties of PVC compounds upon weathering are categorized as due to physical aging or due to chemical change. PVC's tensile strength, flexural strength, tensile modulus, and flexural modulus generally rise slightly with weathering. DSC data on weathered samples show an annealing effect identical to physical aging. The impact strength of weathered PVC is substantially lower than expected from physical aging. Molecular weight of PVC on the weathered surface is lowered upon weathering. Thus the loss of impact strength of PVC upon weathering is mainly due to chemical change.     

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     

Structure and properties of microcomposites and macrocomposites from block polymers

The incorporation of a rubber phase in glassy polymers, as is well known in the case of high impact polystyrene, leads-to an increase in their impact strength. Block polymers offer three principal approaches for obtaining multiphase glassy polymers in which an elastorner phase is present in the matrix of the glassy polymer. They are: (1) control ofblock polymer composition, (2) blending of block polymer with homopolymers, and (3) polymerization of a solution.of a block polymer in the monomer corresponding to one of the blocks. The observed properties, such as impact strength, modulus, and heat distortion temperature, desired in rubber modified glassy polymers are discussed for block polymer systems prepared using the above approaches.     

Block polymers from isocyanate-terminated intermediates. IV. Properties of cured butadiene–ε-caprolactam block polymers

Butadiene–ε-caprolactam block polymers containing a high proporation of 1,2 units in the butadiene-segments were synthesized and physical properties were measured on the cured copolymers. Flexural strength and impact resistance both increase regularly with increasing ε-caprolactam content in peroxide cured copolymers. This behavior is explained by the higher values of flexural modulus and impact resistance for poly(ε-caprolactam) compared with peroxide-cured polybutadiene resins. Copolymers reinforced with silica showed higher heat distortion temperatures but lower impact resistance than corresponding unfilled samples. Arrhenius plots of flexural properties at various test temperatures were linear. Both flexural modulus and strength decreased regularly with increasing test temperature. Flexural properties of filled copolymers were relatively unaffected by heat aging up to 204°C for several weeks, however, dramatic decreases in these properties were noted in a matter of days when heat aging was done at 260–316°C. These results are explained by the rapid degradation of poly(ε-caprolactam) above its melting point. Block polymers whose butadiene segments contained a high proportion of 1,4 units were also synthesized. These copolymers were elastomeric when cured with either sulfur or peroxide.     

三唑二巯基铵盐交联聚氯乙烯的制备及性能

选用三唑二巯基铵盐(FSH)作为聚氯乙烯(PVC)的交联剂,考察了模压温度、模压时间和交联剂用量对PVC交联的影响,并通过红外分析、无转子硫化仪、电子万能试验机、维卡软化温度试验机和扫描电镜等,研究了交联PVC的化学结构、交联过程、力学性能、耐热性能和断面形貌。结果表明:FSH能使PVC交联且凝胶率较高;交联程度受模压温度和模压时间影响很大,当模压温度为180℃、模压时间为120 s时比较适宜;交联后PVC的拉伸强度和缺口冲击强度提高,断裂伸长率降低。交联剂用量为1.5份时,综合性能最好,拉伸强度达48.9 MPa,缺口冲击强度达16.3 kJ/m^2,维卡软化点达到75.9℃,较未交联PVC提高了18.4℃。     

Effect of filler addition and weathering conditions on the performance of PVC/CaCO3 composites

This study deals with the effects of calcium carbonate (CaCO₃) fillers and hygrothermal aging on the performance of polyvinylchloride (PVC). The properties of the PVC/CaCO₃ composite were studied before and after aging in water up to 3 months at 24°C ± 3°C, 70°C, and 90°C. In terms of fillers effect, it was found that the incorporation of fillers in PVC induces an increase in both T_g value and storage modulus; however, it had no significant effect on the water absorption. However, the addition of fillers has resulted in an improvement in the elastic modulus, whereas it has shown harmful effect on the tensile strength and elongation at break. Concerning flexural properties, an important filler percentage, that is, 35 wt%, is proved to be the optimum content to achieve maximum strength and modulus as well as wear properties. In terms of aging impact, it was found that shift in color on aging occurs noticeably. Elastic modulus, tensile strength, flexural strength, and flexural modulus increase with increasing temperature from ambient to 70°C, whereas they decrease at 90°C. Dynamic mechanical thermal analysis confirmed that at high temperature, the absorbed water affects the PVC matrix during aging. As a result, a loss in strength and stiffness but a gain of ductility was observed. The great quantity of absorbed water acts as a barrier layer and, thus, minimizes the wear. POLYM. COMPOS., 37:2171–2183, 2016. © 2015 Society of Plastics Engineers     

Cold-rolling of polymer: 4. Toughness enhancement in amorphous polymers

Several types of amorphous polymers have been cold-rolled to various thickness reductions and the notched Izod impact behavior has then been studied. It has been determined that whereas some polymers exhibit large increases in impact strength with modest reductions in thickness other polymers only exhibit small increases in impact strength. For example, PVC, ABS, poly (phenylene oxide), and polysulfones show large increases in impact strength whereas rubber-toughened acrylics show only a small increase in impact strength.     

Vinyl composites—fiberglass reinforced PVC

Glass fiber reinforced PVC has several distinctive and useful properties. Its tensile strength can be twice that of unreinforced PVC. Excellent coupling of the glass fibers to the PVC matrix is required for good retention of tensile strength when exposed to warm water, Its modulus can be twice that of unreinforced PVC and equal to that of wood. PVC's high load carrying capability is not significantly increased to higher temperatures by adding glass fibers as judged by its 264 psi heat deflection temperature. However, by changing the polymeric matrix, glass reinforced vinyl with an increased HDT of 86°C has been produced for higher use temperature. The coefficient of linear thermal expansion of PVC can be cut in half by the addition of glass fibers and has a coefficient equal to that of aluminum. Glass fiber reinforced PVC has exceptionally good resistance to crack propagation and resists shattering as judged by sawing, punching, stapling, and hammering. When properly formulated for weathering resistance, glass fiber reinforced PVC has good color retention, impact retention, and outstanding dimensional stability. As for all glass fiber reinforced plastics, processing equipment must be built for high abrasion resistance for long economical manufacturing runs.     

Ultraviolet light aging properties of PVC/CaCO3 composites

The ultraviolet radiation aging behaviors of PVC/CaCO₃ and PVC/CaCO₃/macromolecular modifier composites were studied through whiteness measurement, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, scanning electron microscopy, and mechanical properties test. It was found that nano‐CaCO₃ particles used as ultraviolet light screening agents could significantly enhance the antiaging properties of PVC materials. Due to the macromolecular modifier coated on nano‐CaCO₃ particles, the compatibility of nano‐CaCO₃ and PVC matrix was improved, resulting in uniform dispersion of nano‐CaCO₃ in PVC matrix. Therefore, the PVC/CaCO₃/MP composite exhibited better antiaging properties than PVC/CaCO₃ composite. After 12 h of ultraviolet irradiation, the tensile strength retention, elongation at break retention, and impact strength retention of PVC/CaCO₃/MP composite were 79.5%, 74.5%, and 75.3%, which were much higher than that of neat PVC and PVC/CaCO₃ composite. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Impact strength of polymers: 1. The effect of thermal treatment and residual stress

The effect of thermal annealing and quenching on the notched Izod impact strength of several polymers has been studied. Primary emphasis was placed on polycarbonate, but ABS, PVC, polysulfone, and polymethylmethacrylate were also studied. It was determined that residual stresses created by thermal quenching from above the glass transition temperature can have a great effect on impact strength for the polycarbonate, PVC, and polysulfone polymers studied. In fact, it is shown that the thickness transition observed in impact strength for polycarbonates is governed by the residual stresses and not by thickness. In polycarbonates, quenched sheets up to 3/8 in. in thickness have shown impact strengths of 18 ft-lb/in. whereas sheets 1/8 in. in thickness can be embrittled by annealing, showing an impact strength of 2 ft-lb/in. However, it has been shown that this embrittlement results from the absence of residual stress. Residual stresses having maximum values up to 3000 psi (in Compression) have been determined at the polycarbonate sheet surface using birefringence measurement techniques. The existence of these compressive stresses is postulated to restrict the extent of craze growth at the notch tip, and the impact specimen can yield rather than fail in a brittle manner if the stress state is sufficient.     

The effect of physical aging on properties of rigid polyvinyl chloride

This paper describes the effects of physical aging on properties of rigid PVC, such as tensile strength, tensile modulus, Izod impact, coefficient of thermal expansion, specific gravity, differential scanning calorimetry, and heat deflection temperature.     

Influence of various molding conditions on the uni‐, bi‐, and triaxial impact properties of poly(vinyl chloride) (PVC)

This study discusses the influence of molecular weight, melt temperature, mold temperature, and aging on the impact characteristics of molded PVC. Tensile impact (uniaxial), instrumented drop‐dart impact (biaxial), and Izod impact (triaxial) methods were utilized to assess the impact properties of the material under investigation. It was found that the impact properties were affected by aging more than by the changes in the melt temperature or the mold temperature. Additionally, the molecular weight played a significant role in influencing the impact properties of PVC.     

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.     

玻纤增强尼龙66的抗高温热氧老化研究

用熔融共混法制备了不同抗氧剂体系改性的玻璃纤维增强尼龙66复合材料,采用热烘箱老化法研究了180℃下老化时间对复合材料高温热氧老化性能影响。结果表明,随着老化时间的延长,未添加抗氧剂的复合材料的拉伸强度和缺口冲击强度保持率显著下降,而添加了1098/168抗氧体系和LS-21抗氧体系的复合材料的相应力学性能保持率明显提高,其中LS-21抗氧体系的效果更佳,对复合材料具有更为优异的初期加工稳定化和长期抗高温热氧老化作用。     

纳米蒙脱土对PVC微发泡体系的影响

研究了纳米蒙脱土对PVC微发泡体系的力学性能和泡孔结构的影响。试验表明：纳米蒙脱土具有成核作用，当纳米蒙脱土用量为6份时。材料体内孔洞较多，且分布均匀。微孔达到最好状态，此时材料的冲击强度较好，热变形温度较高；当蒙脱土用量为8份时。界面有丝络状结构，蒙脱土与基体树脂之间的相容性较好，此时，材料的弯曲强度和拉伸强度较好；电镜试验验证了此结论。     

氯乙烯共聚弹性体对聚氯乙烯的改性及性能影响

以氯乙烯-丙烯酸丁酯-甲基丙烯酸甲酯共聚弹性体（VCE）增韧改性PVC树脂提高聚氯乙烯（PVC）的抗冲击性能,并与传统抗冲击改性剂甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物（MBS）、ACR及氯化聚乙烯（CPE）改性的PVC材料比较。对改性PVC的流变性能、力学性能、热变形性能及断面结构进行表征和微观观察。结果表明,随着VCE含量的增加,PVC的拉伸强度与弯曲强度逐渐减小,抗冲击强度与断裂伸长率逐渐增加,热变形温度逐渐降低;在相同用量的条件下,VCE对 PVC的改性效果优于ACR及CPE,达到MBS改性PVC的水平,VCE能够增韧PVC,提高PVC的抗冲击性能,是一种性能优异的新型PVC抗冲击改性剂。