Vicat Softening Temperature Research Articles

Ultrahigh performance polylactide achieved by the design of molecular structure

Poor melt strength and crystalline properties are the key barrier for polylactide (PLA) toward broader applications. Long chain branched PLA (LCB-PLA) with high foamability and heat resistance are prepared by employing dual-functional 4-vinylbenzyl glycidyl ether (VBGE) as branching coagent with cyclic peroxide. As a result, the branched chains with same length of original PLA chains are uniformly dispersed on PLA backbones via both the free-radical grafting reaction of the vinyl group in VBGE with one PLA backbone and end-group reaction of the epoxy group in VBGE with the carboxyl group of the other PLA chain. Not only the significantly enhanced foamability and heat resistance of LCB-PLA induced by the largely improved melt strength and crystallization performance but also the excellent processing flowability due to a relatively slight increase in the shear viscosity are found. Specifically, as compared to the pure PLA, the expansion ratio of LCB-PLA with 0.6 wt% VBGE is increased by 17.4 times, and the Vicat softening temperature is enhanced by 95.5 °C. Thus, this study paves a novel one-step continuous strategy to design LCB-PLA with ultrahigh foamability and heat resistance, which is valuable for the large-scale popularization of foamed PLA packaging products.

Fully biodegradable polylactide foams with ultrahigh expansion ratio and heat resistance for green packaging

Long chain branching (LCB) structures are efficiently introduced into polylactide (PLA) by employing sustainable soybean oil (SO) under the initiation of trace amount of cyclic peroxide, which displays robust foamability and heat resistance. It is discovered that with the introduction of 0.6 wt% SO, the expansion ratio and Vicat softening temperature of LCB PLA are sharply raised to 75.2-fold and 155.8 °C, respectively, which is about 17.9 and 2.6 times those of linear PLA. This is because that the amounts of LCB structures are significantly increased in LCB PLA by the addition of SO with low reactivity of internal CC bonds, which can avoid the oligomerization reaction, resulting in more dramatically improved melting strength and crystallization performance of LCB PLA. Moreover, the hydrolytic degradation of LCB PLA is largely expedited as compared to linear PLA, owing to the more rapid water permeation caused by the loose packing of LCB structures. Finally, the PLA foam tray with light weight and good heat resistance is successfully developed by using LCB PLA with 0.6 wt% SO through extrusion foaming with supercritical carbon oxide and thermoforming techniques. Hence, this research offers a green route to produce eco-friendly light-weight and high-heat-resistance LCB-PLA foam with full biodegradability, which is an ideal alternative to the non-degradable oil-based plastics in the field of disposable packaging products.

Semi-aromatic polyamides containing fluorenyl pendent toward excellent thermal stability, mechanical properties and dielectric performance

Semi-aromatic polyamides (SaPAs) combining each advantages of aliphatic and aromatic polyamides received ever-increasing development in both academia and industrial circles. In this work, four kinds of SaPAs with fluorenyl pendent and different length of aliphatic spacers, named P–FPB, P–FPH, P–FPO and P–FPD respectively, were designed and synthesized via the aromatic nucleophilic substitution (SNAr) polycondensation. The effects of both the rigid pendent and flexible methylene (4, 6, 8, 10) spacers on the comprehensive properties of the SaPAs were comprehensively investigated. At the presence of the rigid fluorenyl pendent and the intermolecular π–π stacking thereof, the resulting SaPAs exhibited enhanced glass transition temperature (Tg), thermal stability, solubility in typical organic solvents and mechanical properties compared with the commercially available 6T based SaPa. Also with increasing the number of the methylene units of the SaPAs, their Tg, Vicat softening temperature, tensile strength and modulus gradually decreased; while the initial decomposition temperature and impact strength anomalously increased. Rheological investigations and solubility tests further confirmed that the resulting SaPAs were suitable for processing either in melt or in solution. In addition, these polyamides displayed favorable dielectric properties for potential availability in electric and electronic applications.

Synthesis of tri-functional allyl-endcapped triphenylmethane crosslinker and evaluation of crosslinking effect on properties of high-density polyethylene

Herein, we reported the synthesis of tri-functional allyl-endcapped triphenylmethane crosslinking agent for the preparation of crosslinked high-density polyethylene (X-linked HDPE) via di-tert-butyl peroxide initiated free radical polymerization. The less reactive allyl functionality was selected, an attribute that was essential to attain a more uniform crosslinked network. A synthesis route was planned to make the high purity allyl-endcapped triphenylmethane crosslinker by the reaction of 4-(2-propenyloxy) benzoic acid (PBA) and a diamine (DA). The purity and chemical structure of synthesized crosslinker was established with help of its physical data, infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H-NMR/13C-NMR), elemental (CHN), and thermogravimetric analysis (TGA). The synthesized allyl-endcapped triphenylmethane monomer was found to be thermally stable up to 315 °C due to its aromatic ring structure. Further, X-linked HDPE sheets were prepared with allyl-endcapped triphenylmethane crosslinker via melt blending followed by compression molding techniques. The investigation of various thermomechanical properties of X-linked HDPE sheets suggested improved thermal stability by 49 °C attributed to thermally stable allyl-endcapped triphenylmethane crosslink units, enhancement in vicat softening temperature by 1 °C, high gel content of 2.33%, high tensile strength, lower modulus of elasticity, and reduction in elongation break as compared to control sample, prepared without allyl-endcapped triphenylmethane crosslinker.

Influence of nucleation and growth mechanisms on the heat deflection temperature of a reactively processed polypropylene nanocomposite

AbstractThe development of a reactively processed polypropylene nanocomposite (PPNC) with consequential improvements in the heat deflection temperature (HDT), Vicat softening temperature (VST), and crystallization peak temperature (Tc) is reported herein. Neat PP without nanoclay was also reactively processed to elucidate the effects of fillers on the improvement in physical properties. The results show a considerable improvement in the HDT of PPNC (77.9 °C) compared to those of neat PP (62.6 °C) and reactively processed branched PP (BPP; 69.2 °C). Moreover, the Tc of PP in PPNC improved by ~14% compared to that of neat PP. Various models of nonisothermal crystallization kinetics were employed to elucidate the nucleation and crystal growth mechanisms, and to correlate them with the observed HDT improvement in PPNC. Thermal transitions investigated by modulated differential scanning calorimetry explained the changes observed in the VSTs of all the samples. To the best of our knowledge, this is the first report on a significant improvement in HDT along with a marked increase in Tc. Such simultaneous improvements in HDT, VST, and Tc are highly desirable for applications involving the use of PP‐based materials in rigid packaging.

Spray-formed polyurea composites filled with basalt powder as inorganic waste filler

ABSTRACT The effect of basalt powder (BP) as a waste filler on the properties of polyurea (PUA) has been investigated. The BP was added into a two-component quick-setting polymeric matrix and formed by spray forming. The characterisation of the composites manufactured using waste inorganic particulate filler was performed using mechanical testing (static tensile test and hardness measurement), thermomechanical analysis (Vicat softening temperature – VST and dynamic thermomechanical analysis – DMA) and thermogravimetric analysis (TGA). Properties of the pure PUA and PUA-composites were discussed in reference to structural analysis proceeded by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The addition of BP into PUA allows improving the overall performance of spray-formed material properties. Composite filled with 20 wt-% of the BP showed the most beneficial set of mechanical properties with simultaneously improved thermomechanical and thermal properties.

Lifting the quality of fused filament fabrication of polylactic acid based composites

The development of well-designed polylactic acid (PLA) based composite filaments through fused filament fabrication (FFF) is crucial, as PLA printed parts are characterized by a high brittleness. Here we focus on FFF composite formation using ductile poly (butylene adipate-co-terephthalate) (PBAT), the nanoclay cloisite and the chain extender Joncryl. A high modulus, flexibility, toughness and notched impact strength result upon combining PLA/PBAT (80:20; mass basis) with a sufficiently high cloisite amount (1–5 phr) supported by a suited Joncryl amount (0.3 phr). A fine PBAT dispersion is then ensured, as confirmed by scanning and transmission electron microscopy. For high cloisite amounts (e.g. 10 phr) the crystallinity and vicat softening temperature enhance but cloisite aggregation is unavoidable, leading to a strong reduction in tensile strain and toughness. Annealing increases crystallinity thus material strength, rigidity and impact, at least partially overruling the need of a fine dispersion. Novel radar charts are also reported to select an optimal bio-based blend suitable for different end-user applications by adjusting the composition and possible post-annealing of printed products.

Annealing efficacy on PLA. Insights on mechanical, thermomechanical and crystallinity characters

Poly (lactic acid) (PLA) is widely used biodegradable thermoplastic in the additive manufacturing, mainly on manufactured products through 3D printing. However, PLA is highly fragile and presents low impact strength; hence improvements on this way are industrially and technologically important. Aiming to develop proper methodology for higher PLA performance, this work investigated the effects of thermal annealing on the mechanical properties (impact, tensile, Shore D hardness), heat deflection temperature (HDT), Vicat softening temperature (VST) and crystallinity (X-ray diffraction) of PLA. Injected specimens were annealed in greenhouses at 70, 80, 90 and 100 °C. Annealing at 70 °C was not effective, without verified significant changes. On the other hand, annealing at 80, 90 and 100 °C provided crystalline peaks in DRX, indicating development of structural organization. Expressive results were achieved, at 90 °C, for impact strength, HDT, VST, Shore D hardness and tensile strength, related to non-annealed PLA. Provided results in this work have scientific and technological importance, since the mechanical and thermomechanical properties of PLA were improved using a simple methodology which may render higher performance products mainly for the 3D printing industry of PLA.

Влияние способа переработки на теплостойкость вторичного блок-сополимера пропилена и этилена, наполненного рисовой шелухой

Polymer composites based on secondary thermoplastic polymers filled with biodegradable components of plant origin was developed. Repeated thermal and mechanical action on polymers during their processing in the presence of dispersed phase particles leads to a change in the thermophysical and strength characteristics of finished products. The paper studies the regularities of changes in the heat resistance of polymer composites based on a secondary block copolymer of propylene and ethylene, and rice husks, processed by injection molding and pressing. It is shown that filling the secondary polymer with rice hulls leads to an increase in the heat resistance of composites, which is characterized by an increase in the bending temperature under load, Vicat softening temperature, and decomposition temperature during thermogravimetric analysis in an inert atmosphere. Compared to the injection molding method, the processing of polymer composites by pressing makes it possible to obtain more heat-resistant plastic products. Obviously, this is due to the different degrees of crystallinity of the polymer phase. The high cooling rate of the polymer composite melt during the filling of the injection mold reduces the time required for the corresponding change in the conformation of macromolecules and the formation of the crystalline phase. As a consequence, an increase in the content of the amorphous phase of the secondary block copolymer of propylene and ethylene decreases the heat resistance of the prototypes.

Highly Toughened and Heat-Resistant Poly(lactic acid) with Balanced Strength Using an Unsaturated Liquid Crystalline Polyester via Dynamic Vulcanization

Poly(lactic acid) (PLA) is a well-known sustainable plastic but with an inherent brittleness, slow crystallization rate, and poor heat resistance, which significantly limits its application. In this work, toughened PLA with a balanced tensile strength, fast crystallization rate, and great heat resistance was obtained by dynamic vulcanization with an unsaturated liquid crystalline polyester (PBDPSM) in the presence of a free radical initiator of dicumyl peroxide (DCP). PBDPSM is efficient in enhancing the tensile toughness of PLA in that the elongation at break of PLA significantly increased from 15 to 179% while adding only 1 wt % PBDPSM. When adding 8 wt % PBDPSM, the PLA/PBDPSM8 blend has an elongation at break of 265%, tensile toughness of 107.2 MJ/m3, and notched Izod impact strength of 22.5 kJ/m2. Moreover, it keeps a high tensile strength of 62.6 MPa. In addition, the crystallization rate of PLA has dramatically accelerated due to the apparent nucleation effect induced by DCP and PBDPSM. PLA/PBDPSM3 shows the highest crystallinity with 44.4%. Furthermore, it shows a high Vicat softening temperature of 152.2 °C, which is 92.2 °C higher than that of neat PLA. Finally, highly toughened PLA materials with balanced tensile strength and good heat-resistant properties were realized.

Enhanced thermo-mechanical, thermal and EMI shielding properties of MWNT/MAgPP/PP nanocomposites prepared by extrusion

In this work, multiwalled nanotube/maleic anhydride–grafted polypropylene/polypropylene (MWNT/MAgPP/PP) nanocomposites are produced using an industrially relevant twin-screw extrusion process. The composites with varying nanotube content in the range of 0.5 wt% to 2 wt% were synthesized and evaluated for their thermo-mechanical (i.e., Vicat softening temperature (VST), heat deflection temperature (HDT)), thermal (i.e., Melting (Tm) temperature, crystallization (Tc) temperature and thermal decomposition (Td) temperature), and electromagnetic interference (EMI) shielding properties. The scanning electron microscopy (SEM) of composite cross-sections reveal uniform dispersion of MWNTs in the polymer matrix. Overall, the MWNT content in the composites was found to influence the composite properties with higher nanotube loadings resulting in a higher increase in the measured properties over the MAgPP/PP sample. The composite containing 2wt% MWNTs exhibited the highest increase of 33.42%, 15.52%, 15.42%, 10.23%, over the pure MAgPP/PP sample in its Tdi, Tdf, VST and HDT values, respectively. The electromagnetic interference (EMI) shielding effectiveness of 2 mm thick sample containing 2wt% MWNTs content was measured to be 5.9 dB in the X-Band frequency range of 8–12.4 GHz, which corresponds to 74.29% attenuation of incident wave power. The results obtained suggest the viability of the masterbatch based extrusion method as a potential strategy for the large-scale production of nanocomposites.

Bio-Based Packaging Materials Containing Substances Derived from Coffee and Tea Plants.

The aim of the research was to obtain intelligent and eco-friendly packaging materials by incorporating innovative additives of plant origin. For this purpose, natural substances, including green tea extract (polyphenon 60) and caffeic acid, were added to two types of biodegradable thermoplastics (Ingeo™ Biopolymer PLA 4043D and Bioplast GS 2189). The main techniques used to assess the impact of phytocompounds on materials’ thermal properties were differential scanning calorimetry (DSC) and thermogravimetry (TGA), which confirmed the improved resistance to thermo-oxidation. Moreover, in order to assess the activity of applied antioxidants, the samples were aged using a UV aging chamber and a weathering device, then retested in terms of dynamic mechanical properties (DMA), colour changing, Vicat softening temperature, and chemical structure, as studied using FT-IR spectra analysis. The results revealed that different types of aging did not cause significant differences in thermo-mechanical properties and chemical structure of the samples with natural antioxidants but induced colour changing. The obtained results indicate that polylactide (PLA) and Bioplast GS 2189, the plasticizer free thermoplastic biomaterial containing polylactide and starch (referred to as sPLA in the present article), both with added caffeic acid and green tea extract, can be applied as smart and eco-friendly packaging materials. The composites reveal better thermo-oxidative stability with reference to pure materials and are able to change colour as a result of the oxidation process, especially after UV exposure, providing information about the degree of material degradation.

From disposal to sustainable development: technological potential of poly(lactic acid) (PLA) blends with 3D filament waste

Additive manufacturing is growing rapidly in the automotive, medical, and aerospace industries as an option for the manufacturing of products. However, there is a continuous growth in the amount of waste generated by 3D filaments, thus, the reuse practice becomes important, since it brings environmental and economic gains. The present research evaluated the mechanical, thermal, thermomechanical and rheological properties of PLA/PLAr blends containing post-consumption 3D filament. The blends were prepared in a co-rotational twin screw extruder and, subsequently, the extruded granules were injection molded. As the PLAr content in the blends (PLA/PLAr) increased, there was a reduction in viscosity, indicating an improvement in manufacturability. The PLA/PLAr blend (75/25 % wt.) increased the degree of crystallinity compared to neat PLA, indicating that PLAr acted as a nucleating agent. As a consequence, the PLA/PLAr blend (75/25 % wt.) showed performance comparable to neat PLA in thermal stability, elastic modulus, tensile strength, Shore D hardness, impact strength, heat deflection temperature (HDT) and Vicat softening temperature. The reuse of post-consumption 3D filament PLA is feasible for the development of materials with good properties. In addition, value is added to the post-consumption material and there is a contribution to sustainable development.

Effect of poly(lactic acid) crystallization on its mechanical and heat resistance performances

Poly (lactic acid), a promising biodegradable polymer, is restricted by poor heat resistance, which is determined by the crystallization. It is important to expound the relationship between crystal structure and thermal, mechanical performance. Several PLA specimens were prepared by fully crystallized at different temperature (100 °C, 110 °C, 115 °C, 120 °C, and 130 °C) from melt state. The morphology, crystallization behaviors, thermal and mechanical properties were evaluated by polarizing optical microscope (POM), wide-angle X-ray diffraction (WAXD), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and Vicat softening temperature (VST), respectively. It was found that the PLA crystal shows the characterization of spherulite and many nuclei are generated at low temperature (100 °C and 110 °C). The nuclei gradually decrease and the spherulites grow as the crystallization temperature increases. Compared with the amorphous PLA specimens, the tensile strength of crystallized samples gradually decreases from 29.4 MPa to 25.8 MPa and the VST is improved from 51.6 °C to 64.9 °C. It confirms that the crystallization is an effective way to enhance the heat resistance. However, when the temperature reaches 130 °C, the crystalline and amorphous region aggregate, forming the distinct two phases, which leads to a decrease in VST (53.2 °C). Meanwhile, the spherulites become irregular, larger, and imperfect at high temperature, resulting in the further deterioration of mechanical performance. In addition, the molecular dynamics was further used to simulate the structural evolution during the crystallization and reveals the mechanism behind the relationship.

Direct Preparation of High Thermal Stable PLA‐Based Nanocomposite via Extra‐Low Loading of In Situ Exfoliated Ultrathin MWW Zeolite Nanosheets

AbstractPoly(lactic acid) (PLA)‐based nanocomposite incorporated with zeolite MCM‐22 precursor at extra‐low loading of 0.2–0.8 wt% is directly prepared by melt compounding and injection moulding method. The Vicat softening temperature raises up to >155 °C, much higher than that of pure PLA (63 °C), which is very beneficial for its application in many fields such as a container for hot food due to its environmentally friendly property. The high heat resistance property is believed to not be caused by the improvement of crystallinity and glass transition temperature but resulting from the obstruction of PLA polymer chain movement originating from >CO···HOSi hydrogen bonding between PLA molecules and the in situ exfoliated MWW zeolite nanosheets with abundant exposed surface silanol groups. Such a method would pave a new way not only for designing more types of thermal stable polymer composites but also for delaminating multi‐layered zeolite precursors.

Rheological study of EPDM/silicone rubber blends phase inversion and characterization of resultant mechanical and thermal properties

AbstractThis study was committed to the characterization of the rheological, thermal, mechanical, and morphological properties of ethylene‐propylene‐diene monomer (EPDM)/silicone rubber (SR) blends. These blends are a potential new class of materials for the insulation of circuits and electrical components that actuate in environments with high heat generation. The blends were produced in a torque rheometer with a Banbury type rotor, varying the concentration of EPDM and SR. Results obtained by capillary rheometry were applied to three theoretical models to analyze the phase inversion threshold, which was confirmed by scanning electron microscopy images. Such analyzes were important to describe the consequence of phase inversion on the evaluated properties. It was reported that the increase in SR concentration decreased the elastic modulus and increased the tensile strength of the blends. For blends with composition situated after phase inversion, the SR becomes the matrix, leading to a significant rise in the Vicat softening temperature and reduced thermal conductivity. Such improvements extend the range of applications of these materials as electrical insulators in environments with higher heat generation.

Polypropylene/wood powder/ethylene propylene diene monomer rubber‐maleic anhydride composites: Effect of PP melt flow index on the thermal, mechanical, thermomechanical, water absorption, and morphological parameters

AbstractEnvironmental damage promoted trough post‐consumer waste from the wood industry has worried the society, while its inadequate disposal has raised concerns of the scientific community. Environmentally and economically effective alternative is reusing this residue to produce smart composites. Therefore, this work aimed to investigate the performance of polypropylene (PP)/Jatobá Wood Powder (WP) composites compatibilized with ethylene propylene diene monomer rubber‐maleic anhydride (EPDM‐MA). The effect of distinct melt flow index (MFI) (PP H103 and PP H503) was also investigated. The composites were characterized using differential scanning calorimetry, thermogravimetry, mechanical properties (tensile, flexural, impact, and Shore D hardness), heat deflection temperature, Vicat softening temperature, water absorption and scanning electron microscopy (SEM). Addition of EPDM‐MA, increased impact strength. The best performance was observed for the composition with 10% EPDM‐MA and PP with lower MFI (PP H503). EPDM‐MA also decreased the water absorption for both PP, most due to the chemical interactions among composite phases. SEM images suggest encapsulation of wood particles by EPDM‐MA, promoting better composites performance. Reported results are valuable for the recycling industry, as well as are economically and environmentally promising.

Performance Parameter Analysis of Power Cable Modified Polypropylene (MPP) Conduit

Modified polypropylene (MPP) conduits are increasingly used as protection conduits for trenchless power cables. In order to ensure the performance and quality of MPP conduits used in the field of power cables, this article has carried out research on its performance parameters and test methods. First of all, in view of the problem of excessive deviation of the MPP conduits appearance and size inspection, the relationship between the conduits wall thickness and the mechanical performance ring stiffness parameter was studied. Then, through the MPP conduits density, ring stiffness, Vicat softening temperature, and flattening test results, the correlation between the three parameters of density, ring stiffness, and Vicat softening temperature is analyzed. It also concluded that the ring stiffness and Vicat softening temperature have a moderate positive correlation. Finally, the article compares some similarities and differences between the MPP conduit and the CPVC conduit for two power cable protection conduits in terms of performance parameter test items.

Studying the Influence of the Mixing Speed of the Polymer Blend of General-Purpose Polystyrene and Acrylonitrile-Butadiene Styrene with the Applications of Artificial Neural Networks

General Purpose Polystyrene (GPPS) has weak properties and this weakness made the applications of this polymer be limited. Therefore, the use of the mixtures of polymers can improve these properties. Different parameters like the mixing speed can affect the quality of the properties of preparing polymer from the mixture of several polymers. In this research, the polymer blend of GPPS and Acrylonitrile-Butadiene Styrene (ABS) has been investigated. In order to prepare this polymer mixture, GPPS has been considered as the main phase (base polymer) and ABS has been considered as the scattered phase (additive). Firstly, the blended polymers with different weight percentages (0, 0.04, 0.08 and 0.12) of ABS/GPPS in different mixing speeds (30, 40, 50 and 60 rpm) have been prepared and for each mixture, the Melt Flow Index (C), Vicat Softening Temperature, Tensile at Break and impact test have been measured. The laboratory data collected from different tests, has been simulated by the Multi-Layer Perceptron (MLP) method of Artificial Neural Networks (ANN) and the results of the simulated data covered the laboratory data perfectly. The results declare that the presence of ABS in the mixed polymer improved the Tensile strength and thermal properties. In order to reach the highest quality in carried out tests, it is considered to use ABS in a high percentage (0.12) and the maximum possible mixing speed (60 rpm).

Characterization of polyethylene terephthalate wastes/Acrylonitril-Butadiene styrene (PETW/ABS) composites with applications of artificial neural networks

During the processes done in petrochemical plants, high amount of polyethylene terephthalate (PET) as PET Waste remains. In this research in order to reuse PET and reduce the environmental problems, PET Waste in different weight percentages (0, 5, 10, 15) has been combined with ABS in different conditions of temperature, time and speed of extruder. Different tests have been performed on polymer mixture like: Impact Test, Elongation at Break, Modular Melt Flow, vicat softening temperature and Yellow Index. The results declared that in condition with constant temperature and time and speed of mixing with increasing PET Waste in ABS the number of Impact Test and Elongation at Break decreases and the number of Modular Melt Flow, vicat softening temperature and Yellow Index increases.When the percentage of PET Waste in ABS is constant, according to the change in each of the conditions of the mixing, it is possible that the amount of the change for different tests to be investigated and the laboratory data to be simulated by the MLP artificial neural networks. The results of the simulation covered the laboratory data perfectly and the information of this article can be used as a reference in order to improve the specifications of the mixed polymer according to the need of increasing polymer properties.