Composites of high density polyethylene and different grades of calcium carbonate: Mechanical,rheological, thermal,and morphological properties

Calcium carbonate (CaCO₃)/high density polyethylene (HDPE) composites were prepared in a HAAKE twin screw extruder, using the experimental conditions defined by the factorial experimental design presented in a prior study. In this study, the effect of different grades (Ca₁ and Ca₂) and CaCO₃ content (varying from 0 to 15 wt %) on the mechanical, rheological, thermal, and morphological properties was evaluated. The results showed that the addition of the filler provoked a decrease on the impact strength, stress at break, and yield stress properties in relation to the pure HDPE. A consequent increase on the modulus of elasticity, indicating an increase on the rigidity of the composite, was observed. It was also verified a tendency to increase the toughness and the viscosity of the composites as CaCO₃ was added. Scanning electron micrographs showed that as the filler was incorporated to HDPE matrix, CaCO₃ particles tended to agglomerate, especially that grade constituted of particles of smaller size. The thermal analysis showed that the addition of mineral filler caused a decrease on the crystallinity degree. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2559–2564, 2006     

The effect of precipitated calcium carbonate nanoparticles in coatings

The insertion of nanoparticles into some industrial materials can give them special properties due to their high reactivity. These nanoparticles interact with other particles, changing and/or improving the final product properties. The aim of this work is to study the effects of nanoparticles of precipitated calcium carbonate (NPCC) with sizes between 40 and 60 nm on the characteristics of architectural paints when used as nanofillers together with micrometric fillers. For this study, two types of emulsion paints were prepared, one without and the other with NPCC. The emulsion paint prepared with NPCC showed better wet-state storage stability of the coating, greater abrasion resistance, lower roughness, and lower wettability than the conventional paint.     

Comparison of polylactide/nano-sized calcium carbonate and polylactide/montmorillonite composites: Reinforcing effects and toughening mechanisms

Semicrystalline polylactide (PLA) exhibits high tensile strength and modulus but very low strain-at-break and toughness. In this study, PLA nanocomposites with nano-sized precipitated calcium carbonate (NPCC) and organically modified montmorillonite (MMT) clay were prepared by melt extrusion. Morphologies, tensile mechanical properties, dynamic mechanical and rheological properties, polymer–nanoparticle interactions, and toughening mechanisms of the PLA/NPCC and PLA/MMT nanocomposites were compared. MMT and NPCC showed significantly different effects on the strength, modulus and elongation of the PLA nanocomposites. Different toughening mechanisms were first elucidated for the two types of nanocomposites based on the evidence from both macroscopic and microscopic observations. Under uniaxial tension, large quantities of microvoids were created in both PLA nanocomposites. The microvoids in PLA/NPCC caused massive crazing, while in PLA/MMT they resulted in shear yielding, particularly in the nanocomposite with 2.5 wt% MMT. The MMT stacks and platelets were found to be located between the microvoids in the extended specimens and prevented them from collapsing and coalescing.     

A comparative study on the effect of different reactive compatibilizers on injection-molded pieces of bio-based high-density polyethylene/polylactide blends

The present study reports on the development of binary blends consisting of bio-based high-density polyethylene (bio-HDPE) with polylactide (PLA), in the 5–20 wt % range, prepared by melt compounding and then shaped into pieces by injection molding. In order to enhance the miscibility between the green polyolefin and the biopolyester, different reactive compatibilizers were added during the melt-blending process, namely polyethylene-grafted maleic anhydride (PE-g-MA), poly(ethylene-co-glycidyl methacrylate) (PE-co-GMA), maleinized linseed oil (MLO), and a combination of MLO with dicumyl peroxide (DCP). Among the tested compatibilizers, the dual addition of MLO and DCP provided the binary blend pieces with the most balanced mechanical performance in terms of rigidity and impact strength as well as the highest thermal stability. The fracture surface of the binary blend piece processed with MLO and DCP revealed the formation of a continuous structure in which the dispersed PLA phase was nearly no discerned in the bio-HDPE matrix. The resultant miscibility improvement was ascribed to both the high solubility and plasticizing effect of MLO on the PLA phase as well as the crosslinking effect of DCP on both biopolymers. The latter effect was particularly related to the formation of macroradicals of each biopolymer that, thereafter, led to the in situ formation of bio-HDPE-co-PLA copolymers and also to the development of a partially crosslinked network in the binary blend. As a result, cost-effective and fully bio-based polymer pieces with improved mechanical strength, high toughness, and enhanced thermal resistance were obtained. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47396.     

Effect of mechanical recycling on crystallization,mechanical, and rheological properties of recycled high-density polyethylene and reinforcement based on virgin high-density polyethylene

This study investigated the effects of mechanical recycling on the crystallization, mechanical, thermal, and rheological properties of recycled high-density polyethylene (rHDPE), as well as vHDPE/rHDPE pellets and films made by different compositions. The results confirmed the presence of contaminants in rHDPEs, and the crystalline diameter of rHDPE is smaller than that of virgin high-density polyethylene (vHDPE), with diameters ranging from 0.60 to 0.72 μm. The content of 75 wt% vHDPE in rHDPE film could repair the defects of crystalline morphology to approximate that of vHDPE films and significantly improve the elongation at break. The temperature required for the transition from crystalline to amorphous state of rHDPE film was 2°C lower than that of vHDPE, and the crystallization time and crystallinity declined compared to that of vHDPE. For rheological performance, the apparent shear viscosity and melt fluidity of rHDPE were worse than those of vHDPE. The blending of low rHDPE with vHDPE is a feasible option not only to reduce plastic waste but also to maintain acceptable properties of the blend composition.     

Structure‐rheology responses of polylactide/calcium carbonate composites

Polylactide (PLA) and calcium carbonate (CaCO₃) were melt blended using a twin‐screw extruder. The morphology of PLA/CaCO₃ composites was observed by scanning electronic microscopy. The linear and nonlinear shear rheological behaviors of PLA/CaCO₃ melts were investigated by an advanced rheology expended system. The results show that the CaCO₃ particles are evenly dispersed in the PLA matrix. The incorporation of low CaCO₃ content (<20%) causes the reduction of the storage moduli, loss moduli, and dynamic viscosities whereas high CaCO₃ content (>30%) leads to the increase of the storage moduli, loss moduli, and dynamic viscosities. The composites with high CaCO₃ content show pseudo‐solid‐like behaviors at low frequency. High CaCO₃ content also results in a significant increase of flow activation energy and a dramatic decrease of flow index n, which is in consistent with the more serious shear‐thinning tendency of high‐filled PLA composites melts. The particular rheological responses might be attributed to the formation and destruction of the percolating network. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of polyethylene glycol on phase and morphology of calcium carbonate

Calcium carbonate (CaCO₃) with different phases and morphologies were prepared and characterized by scanning electron microscopy (SEM), powder X‐ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. The effect of polyethylene glycol (PEG) with different molecular weight and concentrations on the phase and morphology of CaCO₃ was studied. The results showed that aragonite was the only phase in the solution without PEG, while calcite phase could be obtained by the use of PEG as the additive. The possible crystallization mechanism for the formation of CaCO₃ polymorphs in the presence of different PEG was also discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Orientation stretching of a composite fibre based on high-density polyethylene and polyethylene terephthalate

Conclusions An effect of the components on the possible stretch ratio of a composite fibre based on high-density polyethylene (HDPE) and polyethylene terephthalate (PET) has been detected, depending on the orientation stretch temperature, and on the composition and phase structure of the composite.In spite of the fact that the total degree of stretch of the composite fibre is greater than the possible degree of stretch for pure PET, the actually attained degree of orientation of the PET component does not exceed the degree of orientation of the homopolymer.The presence of two types of HDPE has been detected in the oriented fibres — weakly oriented and strongly oriented.Translated from Khimicheskie Volokna, No. 1, pp. 17–19, January–February, 1988.     

Linear low-density polyethylene/high-density polyethylene blends: Effect of high-density polyethylene content on die swell and flow instability

This work aimed to evaluate the effect of high-density polyethylene (HDPE) content and of shear rate on the die swell and flow instability of linear low-density polyethylene (LLDPE)/HDPE blends. The results showed that the die swell of the LLDPE/HDPE blends increased with the increase in the shear rate. At high shear rates, the increase in the HDPE content led to an increase in the die swell of LLDPE/HDPE blends. The surface morphology analysis of the extrudates by optical and scanning electron microscopy revealed the presence of sharkskin and stick–slip flow instabilities in LLDPE and LLDPE/HDPE blends at the shear rates investigated. These instabilities were attenuated with the addition of HDPE and almost disappeared in the LLDPE/HDPE blend containing 50 wt% of HDPE.     

高密度聚乙烯/硅烷偶联剂改性硫酸钙晶须复合材料的制备与性能

以γ-甲基丙烯酰氧基丙基三甲氧基硅烷（KH570）改性的硫酸钙晶须（CSW）为高密度聚乙烯（HDPE）的填料,采用熔融共混法制备了HDPE/CSW复合材料。通过SEM、XRD、TG、DSC表征了KH570改性的CSW对复合材料HDPE/CSW的性能影响。结果表明,改性CSW质量分数为20%时,HDPE/CSW的拉伸和弯曲强度比纯HDPE分别增加9.28%和33.04%,且易产生异相结晶,提升了HDPE/CSW复合材料的耐热性和结晶度。纯HDPE的热降解反应活化能为244.11 k J/mol,改性CSW质量分数为50%时,HDPE/CSW复合材料的热降解反应活化能降到236.99 kJ/mol,表明CSW提升了HDPE/CSW复合材料的热降解反应速率,扩展了复合材料的使用范围。     

Three-dimensional large-strain tensile deformation of neat and calcium carbonate-filled high-density polyethylene

The large-strain tensile deformation of high-density polyethylene and high-density polyethylene filled with two volume fractions (f) of calcium carbonate particles is studied via an optical method. Digital image correlation is used to determine the local displacement gradients and full-field displacements during uniaxial tension tests on specimens of rectangular cross-section. A novel technique measures simultaneously, with a single camera, the deformation in all three dimensions. Full-field strain contours, macroscopic true stress-true strain behavior, and local volumetric strains are reduced from the raw test data. The true stress-true strain data shows an increase in modulus, but a decrease in yield stress and subsequent strain hardening, with increasing f. These results are strong evidence of particle debonding and are corroborated by an increase in volumetric strain with increasing f.     

碳酸钙对氯化聚乙烯发泡性能及发泡体微观形貌的影响

以氯化聚乙烯(CM)为基体、偶氮二甲酰胺为发泡剂、碳酸钙为填料,采用模压法制备了发泡CM,研究了CM的最佳硫化和发泡温度,考察了碳酸钙种类及用量对CM发泡性能及发泡CM微观形貌的影响.结果表明,制备发泡CM的最佳硫化发泡温度为170℃.不同种类碳酸钙对CM发泡性能及发泡CM微观形貌的影响不同,填充量较低(20 份)时,...     

碳酸钙和淀粉对聚乙烯薄膜降解性能影响研究

目的:研究淀粉和CaCO3对塑料薄膜的降解影响。方法:将CaCO3填充膜和淀粉填充膜经自然曝露、紫外线照射和土埋处理,测试拉伸强度、断裂伸长率和分子量的变化。结果:自然曝露30d,CaCO3填充膜和淀粉填充薄膜的平均拉伸强度分别下降80.8%和54.4%,平均断裂伸长率分别下降99.4%和98.3%,分子量分别下降25.3%和13.8%;紫外光照120h,CaCO3填充薄膜和淀粉填充薄膜的平均拉伸强度分别下降14.7%和45.9%,断裂伸长率分别下降97.3%和97.0%,分子量分别下降66.7%和48.3%;土埋203d,CaCO3填充薄膜和淀粉填充薄膜的失重率分别为2.2%和15.0%。结论:CaCO3和淀粉均能加速聚乙烯塑料薄膜的降解,其中CaCO3的光降解性能方面优于淀粉,而淀粉的生物降解性能优于CaCO3。     

Stearic acid as interface modifier and lubricant agent of the system: Polypropylene/calcium carbonate nanoparticles

The toughness and the rheology of polypropylene (PP)‐calcium carbonate (CaCO₃) nanocompounds using stearic acid as an interface modifier were studied in this work. Compounding of the nanocomposites was carried out with a twin‐screw extruder. The benchmark samples (untreated) and stearic acid‐treated CaCO₃ nanoparticles were characterized by Fourier transform infrared (FTIR) spectroscopy. The nanocompounds were characterized by impact test, tensile test, scanning electron microscopy (SEM), rheological analysis, and differential scanning calorimetry (DSC). The elongation‐at‐break and impact resistance were increased in nanocompounds with interface modifier (stearic acid in hopper of the extruder). Nanocompounds with stearic acid showed the best dispersion state. Stearic acid helps to reduce complex viscosity acting as a lubricant, reducing frictional forces between nanoparticles of calcium carbonate (NCC) and PP chains. Nanocompounds with better dispersion state had crystallization temperatures very similar to the PP homopolymer. POLYM. ENG. SCI., 59:E279–E285, 2019. © 2019 Society of Plastics Engineers     

Isothermal crystallization of high density polyethylene and nanoscale calcium carbonate composites

High density polyethylene (HDPE) and calcium carbonate (CaCO₃) nanocomposites with maleic anhydride grafted HDPE (manPE) as a compatibilizer were prepared via compounding in a twin‐screw extruder. The CaCO₃ are well dispersed in the HDPE matrix from the observation of transmission electron microscope. The isothermal crystallization kinetics was studied by differential scanning calorimetry and simulated by Avrami and Tobin models. The nucleation constants and fold surface free energy were estimated from Lauritzen–Hoffman relation. The results indicate that both manPE and well‐dispersed CaCO₃ particles would act as nuclei to induce heterogeneous nucleation and enhance crystallization rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nonisothermal crystallization of high density polyethylene and nanoscale calcium carbonate composites

Nonisothermal crystallization of high density polyethylene (HDPE)/maleic anhydride‐modified HDPE(manPE)/nanoscale calcium carbonate (CaCO₃) nanocomposite was investigated by means of wide angle X‐ray diffraction (WAXD), polarized optical microscopy (POM), and differential scanning calorimetry (DSC). WAXD indicated that the crystallinity was reduced with the addition of CaCO₃. The spherulite size of HDPE increased in the presence of manPE, but decreased when CaCO₃ was added from observation of POM. A modified Avrami analysis, Ozawa analysis, and Liu analysis were applied to the nonisothermal crystallization process. Crystallizability followed the order: HDPE/manPE/CaCO₃ > HDPE/CaCO₃ > HDPE/manPE > HDPE when undercooling was taken into account. Dependence of the effective activation energy on the relative crystallinity was estimated by the Friedman equation, and the results were used to calculate the parameters (K_g and U*) of Lauritzen‐Hoffman's equation by Vyazovkin's method. These results indicate that the addition of maleic anhydride groups and CaCO₃ tend to promote the nucleation of spherulites on their surfaces and lead to epitaxial growth of the crystallites. But at the same time, manPE and CaCO₃ particles may hinder the transport of the molecule chains resulting in a decrease of the crystallization growth rate. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

An investigation of chemical crosslinking effect on properties of high-density polyethylene

High-density polyethylene (HDPE) was chemically crosslinked with various amounts of di-tert butyl cumyl peroxide (BCUP). Crosslink density determined by rubber elasticity theory using hot set test showed an increase with increasing BCUP. Glass transition temperature (T_g), thermal stability, crystallization, melting behavior and tensile properties were studied. The results showed a new finding about decrease in T_g as a consequence of the ‘chemical crosslinking’ of HDPE. This was explained by observed reduction in crystallinity and expected increase in free volume as a result of restriction in chain packing. However, chemical crosslinking had no significant effect on the thermal stability. The stress at break, Young's modulus yield strength and elongation at break generally decreased with increase in BCUP. By increasing the temperature for slightly crosslinked HDPE, the elongation at break was increased but by increasing the crosslinking level an opposite effect was observed. Crosslinked HDPE showed an decrease in creep strain and an increase in creep modulus with increasing BCUP.     

Melt-neutralization of maleic anhydride grafted on high-density polyethylene compatibilizer for polyamide-6/high-density polyethylene blend: effect of neutralization level on compatibility of the blend

Blends of polyamide-6 (PA-6) and high-density polyethylene (HDPE) with blend ratios of 80/20 (wt/wt) and 20/80 (wt/wt) were studied using zinc-neutralized maleic anhydride (MAH) grafted HDPE as compatibilizers. MAH groups were hydrolyzed and neutralized with different amounts of zinc acetate dihydrate in a twin-screw extruder to produce different levels of zinc-neutralization (0, 14, 41, 69, and 95 %) at one and ten parts per hundred of resin of compatibilizer. Melt neutralization of MAH was confirmed by X-ray fluorescence, FT–IR, and rheological properties. SEM micrographs showed a large reduction in the dispersed phase size in the compatibilized blends. Tensile measurements showed improvement of tensile strength for all compatibilized blends; moreover, the elongation at break of compatibilized blends at 10 phr of compatibilizer was improved. Blending increased the crystallization temperature for the PA-6, and the addition of compatibilizer reduced the crystallization temperature slightly. A significant increase in melt viscosity of the compatibilizer was found with zinc addition and adding compatibilizer increased the viscosity of the blends. However, the addition of zinc to the compatibilizer did not change the viscosity in the PA-6-rich blends and actually led to a decrease in viscosity in the HDPE-rich blends.     

Fibre materials based on ultrahigh-molecular-weight polyethylene and montmorillonite nanoparticles

The effect of the thermodynamic quality of the solvent on the properties of polymer solutions was determined. Thermal annealing affects formation of the structure and the mechanical properties of UHMPE. Fourier transform IR spectroscopy revealed the effect of the filler on the structure of the polymer matrix. The morphology of filled UHMPE fibres was characterized by optical microscopy; the fibres have a longitudinally oriented structure and the filler aggregates in particles up to 50 μm in size, which does not allow classifying the materials obtained as nanocomposites. Translated from Khimicheskie Volokna, No. 3, pp. 4–8, May–June, 2008.