Effect of stabilizer type on artificial weathering of rigid PVC. II

The determination of the effectiveness of lead (Pb) and mercaptotin (MT) stabilizers on the useful service life of poly(vinyl chloride) PVC in outdoor applications, necessitates testing the mechanical properties of the polymer before and after weathering, to learn its behavior in the outdoor environment. Artificial weathering was used, and four mechanical tests were carried out, namely tensile, flexure, impact, and fracture toughness tests. The Pb stabilizer system used gave better fracture toughness and impact strength after exposure. The tensile strength and modulus of elasticity of MT-stabilized specimens increased significantly after exposure, unlike Pb-stabilized specimens. Brittleness in unplastisized PVC can be attributed to a number of factors, such as unsaturation, carbonyl group concentration, stabilized concentration, crystallinity, and extent of dehydrochlorination. The tensile strength and modulus of elasticity increase in tin mercaptide stabilizers significantly with increased UV exposure, while the increase in Pb specimens is less significant. There is a continuous diminution of the percent of elongation at break in both types of Pb or MT specimens, with increased exposure. The ductility of Pb may be accounted for by PbO and Pb stearate (C₁₇H₃₅COO)₂Pb. One of the possible causes for the brittleness of tin mercaptide stabilized specimens is antiplasticization.     

紫外光对PVC/MBS共混物性能的影响

研究了紫外光对PVC／MBS共混物力学性能及缺口冲击断面形貌的影响。结果表明：适当紫外光照射有利于提高共混物的冲击强度、拉伸强度，冲击断面出现明显增强的韧性断裂；过度光照射导致冲击强度、拉仲强度降低，断裂面的韧性特征明显降低，呈现很明显的脆性断裂特征。     

Relationship of fracture behavior and morphology in polyolefin blends

High-density polyethylene (HDPE) and isotactic polypropylene (PP) were mixed either with a stabilizer or with a stabilizer and a compatibilizer in different mixing ratios. The structure and properties of these blends were analyzed by methods such as torsion pendulum measurements, mechanical short time experiments, electron microscopy, and fracture mechanical toughness tests. The results display a strongly increased impact strength in the HDPE/PP blend with compatibilizer within a specific mixing region. The deformation behavior and the mechanism leading to the increased impact strength of the blends were investigated in tensile tests by acoustic emission analysis and scanning electron microscopy: Increased fibrilation and strong strain was registered in the blend with compatibilizer. The impact strength was modeled, using experimentally measured properties such as energy release rate, matrix and inclusion volumes, the impact strength of each component. The inclusion volume that causes plastic deformation was chosen as an additional parameter. The calculated results are in good agreement with the experimental ones.     

Studies on fracture behavior of tough PA6/PP blends

Fracture toughness of injection-molded PA6/PP blends compatibilized with SEBS-g-MA was studied using deeply double-edge notched tension (DDENT) specimens according to the essential work of fracture procedure. The fracture mechanical studies also included tensile impact tests on the DDENT specimens and characterization of the fracture surfaces by electron microscopy. The results were compared with those of traditional tensile tests and Izod impact tests on single-edge notched samples, and the sensibility of the methods was evaluated. Effects of sample position, ligament length, testing direction, and test speed were studied as well. It was found that the essential work of fracture concept, earlier applied to thin sheets, can also be applied to injection-molded tough blends. High deformation of the skin may, however, interfere with the measurements and cause a “tail” in the load-deformation curves. The plastic work of fracture (w_p) was found to correlate with the impact strength, and thus, it described the toughness. The highest values for work of fracture were recorded for the compatibilized blend with a PA6/PP ratio of 80/20. The essential work of fracture (w_e) in turn increased with increasing PA6 content and behaved like tensile strength. The test speed was found to affect the fracture behavior substantially: differences between the materials were more pronounced in high-speed tensile impact tests, which revealed signs of cavitation in addition to large-scale plastic deformation for the tough PA6-rich blend compositions. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2209–2220, 1997     

Long fiber reinforcement of polypropylene/polystyrene blends

The recycling of inseparable polymer mixtures usually results in blends with poor mechanical properties. A mixture of PP and PS was taken as a model compound for a recyclate. The effect of adding glass fibers to a mixture of PP/PS (70/30) was studied, with special attention to long glass fiber reinforcement. Test specimens were made in three different ways: by dry blending (direct injection molding), mild compounding with a single screw extruder, and compounding with a twin screw extruder. The fiber concentration was varied from 0 to 30 wt%. The fiber lengths were determined to investigate fiber attrition. The fiber lengths in the samples were 1.09 mm for dry blending, 0.72 mm for single screw compounding, and 0.33 mm for twin screw compounding. The mechanical behavior was studied by unnotched and notched Izod impact and tensile tests. The PP/PS blend had a low fracture strain and low unnotched Izod impact strength compared with a PP homopolymer. With an increasing fiber concentration and fiber length, the modulus, tensile strength, and particularly the impact strength increased. With a 30 wt% glass fiber of the long fiber compound (dry blended), the modulus was raised by a factor of 3.5, the fracture stress by a factor of 2.5 and the unnotched Izod impact strength by a factor of 10. The product quality as judged by the scatter of the data was best for the twin screw compound and poorest for the dry blend. Compounding with a single screw extruder gave fairly constant injection molding product properties, combined with excellent mechanical properties.     

Micro/nanocellular polyprolene/trans-1,4-polyisomprene (PP/TPI) blend foams by using supercritical nitrogen as blowing agent

Toughed polypropylene (PP) foams, with the combination of blending with trans-1,4-polyisoprene (TPI) and micro/nanocellular structure in the matrix, were prepared using a batch foaming process and N₂ as the blowing agent. The incorporation of TPI in the PP matrix induces the enhanced formability and the slightly improved ductility and toughness compared to the neat PP. The simultaneous existence of the TPI phase and micro/nanocellular structure makes the fracture behavior follow the shear yielding of a bundle of fibrils in the tensile load direction. The results of mechanical properties measurements show that the notched Izod impact strengths of foamed PP/TPI blend are two to three times larger than those of the unfoamed counterparts. The PP/TPI blend foam with 5phr TPI content shows the highest impact strength when the foaming temperature is 140°C, which is fivefold increase over that of the neat PP. The enhanced ductility and toughness of PP/TPI foams were found with the increasing foaming temperature. The insert of micro−/nanocellular in PP/TPI blends simultaneously makes the notched impact strength increase significantly, tensile strength decrease, and elongation at break increase obviously, which provides the possibility to combine the higher impact strength and toughness with the advantage of microcellular foaming. POLYM. ENG. SCI., 60:211–217, 2020. © 2019 Society of Plastics Engineers     

Fracture behavior of glass bead-filled poly(oxymethylene) injection moldings

The mechanical properties of glass bead filled poly(oxymethylene) were investigated as a function of glass bead content and glass bead diameter using injection molded test pieces. Fracture toughness measurements were made using single edge-notched tension and single edge-notched bend specimens. The effect of notch orientation with respect to the mold fill direction on fracture toughness was studied using single gate and double gate moldings. Tensile strength and flexural modulus were measured using standard test pieces. It was found that; (i) fracture toughness of the filled and unfilled polymer was relatively independent of notch orientation, (ii) the presence of weldlines in the molded test pieces did not affect the fracture toughness of unfilled polymer or its composites, (iii) fracture toughness of filled polymer was always considerably lower than that of the unfilled polymer; fracture toughness decreased sharply with increasing bead concentration, (iv) fracture toughness was not a sensitive function of glass bead diameter; it decreased slightly as bead diameter increased, (v) strain energy release rate as measured under impact decreased with increasing bead concentration, (vi) tensile strength decreased linearly with increasing glass bead concentration and was inversely proportional to the square root of the bead diameter, (vii) weldlines did not affect the tensile strength of the polymer or its composities, (viii) flexural modulus increased linearly with increasing glass bead concentration according to the Einstein equation.     

Mechanical properties of polypropylene composites reinforced with long glass fibres and mineral fillers

Abstract

The mechanical behaviour of long discontinuous glass fibre (LGF) reinforced polypropylene (PP) composites filled with talc or calcium carbonate fillers was studied. Sample specimens were processed by injection moulding, after which tensile and impact properties were analysed. In addition, scanning electron microscopy was used to analyse the morphology of the fracture surfaces. The results showed that the use of talc as a hybrid filler in LGF reinforced PP leads to a better tensile strength and toughness than in a corresponding hybrid composite based on calcium carbonate. Furthermore, it was observed that the matrix had a dominant role at low fibre content, whereas at high fibre loading, the effect of fibres was more evident.     

Fiber reinforcement and fracture resistance of PC/PBT/LCP ternary in situ composite

The microstructures, mechanical properties, and fracture toughness of LCP (Vectra B950) reinforced PC/PBT blend with a 60/40 weight ratio have been studied. LCP of varying concentrations were investigated as rigid fillers in matrices of multiphase polymer blends. In this study, differences in microstructures and morphology between samples of two thicknesses (4 mm thick and 6 mm thick) and two geometries (dumbbell and rectangular) were compared using scanning electron microscopy (SEM). Given identical processing conditions, fibrous LCP structures were evident in the 4-mm-thick injection molded, dumbbell-shaped samples, whereas the 6-mm-thick rectangular samples displayed spherical dispersion of LCP aggregates that embrittled the preblended ductile matrix. Tensile properties of the dumbbell specimens showed superior strengthening and stiffening whereby the tensile strength increased twofold and the modulus increased fourfold. Plane strain fracture toughness was slightly enhanced as the LCP content increased because of the fiber strengthening effect but the overall fracture performance of the in situ composites was relatively poor compared with PC/PBT. Experimental results were compared with those predicted in composite theory. Simplified micromechanics equations were developed to describe the tensile moduli of injection molded LCP reinforced blends that exhibited a strong skin-core morphology.     

环氧树脂对PVC/ABS共混物性能的影响

研究了固体环氧树脂(EP)对聚氯乙烯(PVC)/丙烯腈-丁二烯-苯乙烯共聚物(ABS)/EP共混物力学性能和热稳定性的影响,重点考察了EP环氧值和固化剂DDM对共混物性能的影响。结果表明:PVC/ABS/EP共混物表现为脆性断裂;加入DDM后,共混物的拉伸强度明显提高,但冲击性能影响不大;对于PVC/ABS/EP/DDM共混物,随着EP含量的增加,共混物的拉伸强度上升,且环氧值高的EP704对共混物拉伸强度的提高更大;加入2%的低环氧值EP903后,共混物的冲击强度达到最大值,而EP704的加入则对共混物的冲击性能影响不大;环氧树脂的加入在一定程度上削弱了PVC/ABS共混物的热稳定性。     

Effect of the talc filler content on the mechanical properties of polypropylene composites

This research examines the effect of a microsize/nanosize talc filler on the physicochemical and mechanical properties of filled polypropylene (108MF10 and 33MBTU from Saudi Basic Industries Corp. and HE125MO grade from Borealis) composite matrices. A range of mechanical properties were measured [tensile properties, bending properties, fracture toughness, notched impact strength (at the ambient temperature and ?20°C), strain at break, and impact strength] along with microhardness testing and thermal stability testing from 40 to 600°C as measured by differential thermal analysis and thermogravimetric analysis. Increasing filler content lead to an increase in the mechanical strength of the composite material with a simultaneous decrease in the fracture toughness. The observed increase in tensile strength ranged from 15 to 25% (the maximum tensile strength at break was found to be 22 MPa). The increase in mechanical strength simultaneously led to a higher brittleness, which was reflected in a decrease in the mean impact strength from the initial 18 kJ/m² (for the virgin polypropylene sample) to 14 kJ/m², that is, a 23% decrease. A similar dependency was also obtained for the samples conditioned at ?20°C (a decrease of 12.5%). With increasing degree of filling of the talc–polypropylene composite matrix, the thermooxidative stability increased; the highest magnitude was obtained for the 20 wt % sample (decomposition temperature = 482°C, cf. 392°C for the virgin polymer). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

利用回收LDPE/PVDC复合薄膜制备共混材料的研究

以回收低密度聚乙烯/聚偏氯乙烯(LDPE/PVDC)复合薄膜为基体材料,低密度聚乙烯接枝丙烯酸(LDPE-g-AA)为相容剂,线型低密度聚乙烯(LLDPE)为改性剂,再加入液体钙-锌(Ca-Zn)热稳定剂,通过混合、挤出、注塑工艺制备共混材料。采用刚果红法分析了Ca-Zn稳定剂对复合薄膜中PVDC热稳定性能的影响,并对共混材料的力学性能、阻隔性能和微观形态进行了测试与分析。结果表明:加入1.2份Ca-Zn稳定剂后,共混材料的刚果红试纸起始变色时间和完全变色时间分别延长了67 s和354 s,起始变色温度和完全变色温度分别提高了8℃和11℃;含3%LDPE-g-AA的共混材料,PVDC嵌入LDPE材料中,相容性明显改善,其缺口冲击强度和断裂伸长率提高,吸油率下降;含20%LLDPE及3%LDPE-g-AA的共混材料,其拉伸强度为14.43 MPa、断裂伸长率为389.11%、缺口冲击强度为29.51 kJ/m2、吸油率为14.40%,力学性能和阻隔性能优良。     

CPVC热稳定性能研究

采用转矩流变仪、冲击试验机、力学试验机、维卡热变形仪研究了主热稳定剂、辅助热稳定剂、内润滑剂和外润滑剂对氯化聚氯乙烯（CPVC）体系的热稳定性能和流变性能以及最终制品的力学性能的影响。结果表明,主热稳定剂复合铅盐稳定剂为3. 0份,辅助热稳定剂Pb-St和Ba-St分别为0. 7~1. 1份、内润滑剂H-St为0. 5份、外润滑剂石蜡为0. 6份时,体系的加工性能和热稳定性能最好,最终制品的冲击强度、拉伸强度、维卡软化点分别为20. 19 kJ/m2、67. 36 MPa、122.3℃。     

Toughening of immiscible PPE/SAN blends by triblock terpolymers

The mechanical performance of immiscible blends of poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and poly(styrene-co-acrylonitrile) (SAN) and the subsequent influence of compatibilisation by tailored polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock terpolymers (SBM) on the mechanical performance under static and dynamic loads is analysed in detail. A PPE/SAN 60/40 blend was selected as a base system for the compatibilisation experiments. The observed static tensile behaviour is described by micromechanical models and correlated to the blend microstructures as observed by transmission electron microscopy. In most cases, the addition of the SBM triblock terpolymers further enhances the ductility of the blend while only leading to a minor reduction of modulus and strength. Triblock terpolymers with symmetric end blocks, mainly located at the interface between PPE and SAN, led to nearly isotropic specimens. In contrast, SBM materials with a longer polystyrene block predominantly formed micelles in the PPE phase and the blends revealed a highly anisotropic morphology. Comparative investigations of the fatigue crack growth behaviour parallel to the direction of injection also reflected this variation in mechanical anisotropy of the compatibilised blends. A poor toughness and a predominant interfacial failure were observed in the case of the SBM with a long polystyrene block. In contrast, a considerable improvement in properties as a result of pronounced plastic deformations was observed for blends compatibilised by triblock terpolymers with symmetric end blocks. The systematic correlation between morphology and mechanical performance of compatibilised PPE/SAN blends established in this study provides an efficient way for the desired selection of suitable and effective compatibilising agents, ensuring both a superior multiaxial toughness as well as a high strength and modulus of the overall system.     

超韧PA6/ABS合金的制备

以苯乙烯-马来酸酐（SMA）共聚物为增容剂，考察了ABS及SMA的含量对PA6／ABS共混体系的力学性能的影响；并利用SEM研究了PA6／ABS冲击断面的相结构。研究表明：SMA是PA6／ABS共混体系的有效增容剂。随着其含量的增加，分散相ABS粒子的尺寸减小，分散更加均匀，能显著地改善PA6／ABS共混物的冲击、拉伸和弯曲性能。在该共混体系中，ABS含量的增加能够大幅度地提高PA6／ABS共混物的冲击韧性；但当ABS含量超过10％时，将使PA6／ABS共混物的拉伸和弯曲性能明显下降。SMA的添加量为0．5％，且质量比为90／10的PA6／ABS共混体系能保持较好的加工性能，制备的PA6／ABS合金具有最佳的综合力学性能和超高韧性．Izod缺口冲击强度高达1200J／m。     

Fracture toughness of modified polypropylene/poly(styrene‐ran‐butadiene) blends

Fracture toughness of polypropylene (PP)/poly(styrene‐ran‐butadiene) rubber (SBR) blends as a function of concentration of maleic anhydride (MA) in the maleated polypropylene (MAPP) compatibilizer was investigated under uniaxial static and impact loading conditions. The addition of MAPP to the unmodified PP/rubber blend enhanced the tensile modulus and yield stress as well as the Charpy impact strength. The maximum values were recorded at 1.0 wt% grafted MA in the compatibilizer. V‐shaped blunt‐notched specimens exhibited typical ductile behavior and no breakage of the specimens occurred during the impact fracture tests. Sharp‐notched specimens of uncompatibilized and low‐content MA blends broke in a semibrittle manner, supported by a rapid crack propagation process. Increasing MA content in the blends led to semibrittle‐to‐ductile transition characterized by stable crack propagation. Fracture mechanics experiments, supplemented by scanning electron microscopy (SEM), were also employed to obtain a better understanding of the fracture and deformation behavior. Copyright © 2005 Society of Chemical Industry     

Ternary polymer composites: PA6,6/maleated SEBS/glass beads

Polyamide 6,6 (PA6,6)/maleated styrene–hydrogenated butadiene–styrene (SEBS) blends filled with up to 20% spherical glass beads (GBs) were prepared by extrusion and subsequent injection molding. Tensile and impact tests were used to examine the effect of GB additions on the mechanical behavior of PA6,6/SEBS–g–MA 80/20 blend. Tensile measurements showed that the GB additions improve the stiffness of the PA6,6/SEBS–g–MA 80/20 blend but had little effect on its tensile ductility. The impact test revealed that the impact strength of PA6,6/SEBS–g–MA 80/20 blend tends to decrease with increasing GB content. Therefore, the GB additions were beneficial to maintain a stiffness-to-toughness balance of the PA6,6/SEBS–g–MA 80/20 blend. Finally, the correlation between the experimental tensile stiffness and strength with various theoretical models is discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3231–3237, 2001     

i-PB/PP共混物和SP179型PP性能比较

比较了高全同聚丁烯-1/聚丙烯(i-PB/PP)共混物和SP179型PP的力学性能和微观结构。共混物的拉伸强度、屈服强度、断裂伸长率、弯曲模量等力学性能都要优于SP179,而韧性却大大低于SP179。SP179中乙烯嵌段对PP结晶影响较大,而共混物中i-PB对PP结晶影响较小;SP179可溶物中含有较多的抗氧剂,并且含有聚乙烯长嵌段;SP179的热稳定性优于共混物。     

不同受阻胺光稳定剂改性聚丙烯耐光老化性能研究

分析了4种受阻胺光稳定剂在聚丙烯(PP)加工过程中的热稳定性,并研究其单一和复合使用对PP其光稳定性能和力学性能的影响。以失重率为10%时的热分解温度衡量受阻胺光稳定剂的热稳定性,结果表明,受阻胺光稳定剂的加入,使PP的光稳定性能增强;高低分子量受阻胺复合使用,可降低PP的黄变因数和羰基指数,增加其拉伸强度及冲击强度保持率;GW622、GW944和Tinuvin144复合使用效果最佳。     

自制光稳定剂HWPAN-g-TiO2与几种光稳定剂对聚丙烯性能的对比研究

利用废旧腈纶织物制备了一种聚丙烯（PP）用大分子紫外屏蔽吸收类型光稳定剂,利用其和通用的受阻酚类光稳定剂分别制备耐候性PP复合材料,并进行了人工加速老化实验。探究了大分子紫外屏蔽吸收类型光稳定剂在PP老化过程中对PP老化降解的影响,并与通用的受阻酚类光稳定剂进行了对比研究。结果表明,大分子紫外屏蔽吸收类型光稳定剂效果明显,在人工加速老化500 h之后,PP的羰基指数高达150.3;而PP/HWPAN-g-TiO2仅为53,与此同时,PP的拉伸强度从25 MPa降至6.9 MPa,下降了72.4 %;而PP/HWPAN-g-TiO2的拉伸强度从29 MPa降至25 MPa,下降13.8 %。