Effect of Micro-Mold Cavity Dimension on Structure andProperty of Polylactic Acid/Polycaprolactone Blend underMicroinjection Molding Conditions

Microinjection molding is a novel frontier polymer processing strategy different from conventional ones. In this paper, three different cavity-sizes of micro-mold tools were firstly fabricated, and the influences of micro-mold cavity dimension on the phase morphology structure, crystallization and orientation, and mechanical performance of the microinjection molded polylactic acid (PLA)/polycaprolactone (PCL) blend microparts were carefully investigated accordingly. The results show that the reduction of the cavity size would result in much higher shear stress field and cooling temperature gradient, which is advantageous to the fibrillation and orientation of PCL-dispersed phase. Consequently, with decreasing the micro-mold cavity dimension from length 26 mm to 15 mm, the interfacial compatibility is improved, significantly increasing number of PCL fibers with smaller diameter are in situ formed in PLA matrix and their orientation degree also obviously increases, which is verified by SEM and 2D-WAXD measurements. The Differential Scanning Calorimetry (DSC) analysis shows that the decrease in cavity dimension causes the enhancement of PLA crystallization property due to shear-induced crystallization, which is reflected by the decreasing PLA cold crystallization temperature and increasing PLA crystallinity (almost doubling that of conventional macropart). As a result, the dynamic/static mechanical property measurements exhibit that with decreasing the cavity size, the storage modulus, and the loss modulus of PLA/PCL blend micropart increase, and the corresponding tensile strength, elongation at break, and Young’s modulus also present an obviously increasing tendency. The related investigations would provide some new spaces and insights for realization of high-performance of PLA/PCL blend micropart.

Download Full-text

Mechanically Robust Hybrid POSS Thermoplastic Polyurethanes with Enhanced Surface Hydrophobicity

Polymers ◽

10.3390/polym11020373 ◽

2019 ◽

Vol 11 (2) ◽

pp. 373 ◽

Cited By ~ 4

Author(s):

Xiuhuan Song ◽

Xiaoxiao Zhang ◽

Tianduo Li ◽

Zibiao Li ◽

Hong Chi

Keyword(s):

High Performance ◽

Mechanical Performance ◽

Loss Modulus ◽

Surface Hydrophobicity ◽

Hexamethylene Diisocyanate ◽

Scanning Calorimetry ◽

Hybrid Filler ◽

Remarkable Effect ◽

Thermoplastic Polyurethanes ◽

Static Contact

A series of hybrid thermoplastic polyurethanes (PUs) were synthesized from bi-functional polyhedral oligomeric silsesquioxane (B-POSS) and polycaprolactone (PCL) using 1,6-hexamethylene diisocyanate (HDI) as a coupling agent for the first time. The newly synthesized hybrid materials were fully characterized in terms of structure, morphology, thermal and mechanical performance, as well as their toughening effect toward polyesters. Thermal gravimeter analysis (TGA) and differential scanning calorimetry (DSC) showed enhanced thermal stability by 76 °C higher in decomposition temperature (Td) of the POSS PUs, and 22 °C higher glass transition temperature (Tg) when compared with control PU without POSS. Static contact angle results showed a significant increment of 49.8° and 53.4° for the respective surface hydrophobicity and lipophilicity measurements. More importantly, both storage modulus (G’) and loss modulus (G’’) are improved in the hybrid POSS PUs and these parameters can be further adjusted by varying POSS content in the copolymer. As a biodegradable hybrid filler, the as-synthesized POSS PUs also demonstrated a remarkable effect in toughening commercial polyesters, indicating a simple yet useful strategy in developing high-performance polyester for advanced biomedical applications.

Download Full-text

Effect of Nanofiller Content on Dynamic Mechanical and Thermal Properties of Multi-Walled Carbon Nanotube and Montmorillonite Nanoclay Filler Hybrid Shape Memory Epoxy Composites

Polymers ◽

10.3390/polym13050700 ◽

2021 ◽

Vol 13 (5) ◽

pp. 700

Author(s):

Muhamad Hasfanizam Mat Yazik ◽

Mohamed Thariq Hameed Sultan ◽

Mohammad Jawaid ◽

Abd Rahim Abu Talib ◽

Norkhairunnisa Mazlan ◽

...

Keyword(s):

Shape Memory ◽

High Performance ◽

Loss Modulus ◽

Decomposition Temperature ◽

Hybrid Nanocomposites ◽

Mechanical And Thermal Properties ◽

Scanning Calorimetry ◽

Hybrid Filler ◽

Dynamic Mechanical ◽

Tan Δ

The aim of the present study has been to evaluate the effect of hybridization of montmorillonite (MMT) and multi-walled carbon nanotubes (MWCNT) on the thermal and viscoelastic properties of shape memory epoxy polymer (SMEP) nanocomposites. In this study, ultra-sonication was utilized to disperse 1%, 3%, and 5% MMT in combination with 0.5%, 1%, and 1.5% MWCNT into the epoxy system. The fabricated SMEP hybrid nanocomposites were characterized via differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The storage modulus (E’), loss modulus (E”), tan δ, decomposition temperature, and decomposition rate, varied upon the addition of the fillers. Tan δ indicated a reduction of glass transition temperature (Tg) for all the hybrid SMEP nanocomposites. 3% MMT/1% MWCNT displayed best overall performance compared to other hybrid filler concentrations and indicated a better mechanical property compared to neat SMEP. These findings open a way to develop novel high-performance composites for various potential applications, such as morphing structures and actuators, as well as biomedical devices.

Download Full-text

Mechanical Strength Enhancement of Polylactic Acid Hybrid Composites

Polymers ◽

10.3390/polym11020349 ◽

2019 ◽

Vol 11 (2) ◽

pp. 349 ◽

Cited By ~ 4

Author(s):

Ji-Won Park ◽

Jae-Ho Shin ◽

Gyu-Seong Shim ◽

Kyeng-Bo Sim ◽

Seong-Wook Jang ◽

...

Keyword(s):

Composite Material ◽

Mechanical Strength ◽

Polylactic Acid ◽

Mechanical Performance ◽

Natural Fiber ◽

Hybrid Composites ◽

Structural Characteristics ◽

Scanning Calorimetry ◽

Environmental Friendliness ◽

Research Attention

In recent years, there has been an increasing need for materials that are environmentally friendly and have functional properties. Polylactic acid (PLA) is a biomass-based polymer, which has attracted research attention as an eco-friendly material. Various studies have been conducted on functionality imparting and performance improvement to extend the field of application of PLA. Particularly, research on natural fiber-reinforced composites have been conducted to simultaneously improve their environmental friendliness and mechanical strength. Research interest in hybrid composites using two or more fillers to realize multiple functions are also increasing. Phase change materials (PCMs) absorb and emit energy through phase transition and can be used as a micro encapsulated structure. In this study, we fabricated hybrid composites using microcapsulated PCM (MPCM) and the natural fibrous filler, kenaf. We aimed to fabricate a composite material with improved endothermic characteristics, mechanical performance, and environmental friendliness. We analyzed the endothermic properties of MPCM and the structural characteristics of two fillers and finally produced an eco-friendly composite material. The PCM and kenaf contents were varied to observe changes in the performance of the hybrid composites. The endothermic properties were determined through differential scanning calorimetry, whereas changes in the physical properties of the hybrid composite were determined by measuring the mechanical properties.

Download Full-text

Preparation and Characterization of Three-Element Compound Plasticizing Bamboo Fiber-g-Polylactic Acid/Polylactic Acid Composite

Materials Science Forum ◽

10.4028/www.scientific.net/msf.956.201 ◽

2019 ◽

Vol 956 ◽

pp. 201-211 ◽

Cited By ~ 2

Author(s):

Wen Hao Li ◽

Xiao Yu He ◽

Shu Wang ◽

Bing Jie Xu ◽

Yi Qiang Wu ◽

...

Keyword(s):

Polylactic Acid ◽

Interfacial Adhesion ◽

Water Resistance ◽

Bamboo Fiber ◽

National Standards ◽

Scanning Calorimetry ◽

Elongation At Break ◽

X Ray ◽

Interfacial Compatibility

In view of the phenomenon that the interfacial adhesion between bamboo fiber（BF）and polylactic acid (PLA) is poor and incompatible. Firstly the BF-g-PLA structure with hydrophobicity is synthesized through grafting lactic acid into bamboo fiber, then plasticizing the composite. Three-element compound plasticizer was prepared by mixing glycerol, tributyl citrate and formamide. The effect of the proportion and addition content of three-element plasticizer on the interfacial compatibility of the composite was investigated. The BF-g-PLA/PLA composites were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and rotational rheometer (RC) The composites were tested for their bending properties, tensile properties and water resistance properties using national standards. The experimental results show that the best interfacial adhesion between BF-g-PLA and PLA was obtained when the addition content of glycerol, tributyl citrate, formamide was 10%. At the same time, the flexural strength, elastic modulus, tensile strength and elongation at break of composites all reached the maximum, as well as the thermal stability and the storage modulus.

Download Full-text

An insight on the process–property relationships of melt spun polylactic acid fibers

Textile Research Journal ◽

10.1177/0040517519845684 ◽

2019 ◽

Vol 89 (23-24) ◽

pp. 4959-4966 ◽

Cited By ~ 1

Author(s):

AM Ali ◽

HM El-Dessouky

Keyword(s):

Polylactic Acid ◽

High Performance ◽

Polarized Light ◽

Degree Of Crystallinity ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

Laser Diffractometry ◽

Wide Range ◽

Innovative Materials ◽

The Degree Of Crystallinity

Polylactic acid (PLA) fibers are receiving growing interest as one of the recent innovative materials being developed for various applications. The inherent biodegradability of PLA makes it highly attractive for the biomedical and health care sectors. PLA fibers need to be partially and/or highly oriented to allow high performance and readiness for a wide range of manufacturability. In this study, the structure and properties of PLA fibers, manufactured at different spinning speeds, were studied. Laser diffractometry, polarized light microscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to determine the diameter, birefringence, molecular orientation, enthalpy and degree of crystallinity of as-spun and drawn PLA fibers. The results of DSC and XRD showed that the degree of crystallinity of the PLA fibers is significantly improved for the drawn PLA fibers compared to the as-spun fibers and leveled off in the case of changing the take-up speeds of drawn fibers.

Download Full-text

Mechanical Analysis of Polybenzoxazine Matrix in Fiber Metal Laminates

Materials Science Forum ◽

10.4028/www.scientific.net/msf.869.215 ◽

2016 ◽

Vol 869 ◽

pp. 215-220

Author(s):

Cristiane Vilas Boas ◽

Felipe Moreno ◽

Demetrio Jackson dos Santos

Keyword(s):

Mechanical Properties ◽

Carbon Fiber ◽

High Performance ◽

Mechanical Performance ◽

Maximum Load ◽

Fiber Reinforced ◽

Scanning Calorimetry ◽

Fiber Metal Laminates ◽

Carbon Fiber Reinforced ◽

Fiber Metal

In this work we investigated the application of a novel high performance polymer, polybenzoxazine, as a polymeric matrix in Fiber Metal Laminates (FML). This polymer, when applied on the development of FMLs, generated higher mechanical properties in comparison to fiber metal laminates obtained with epoxy. To investigate the mechanical performance of the polybenzoxazine matrix in FMLs, a mechanical behavior comparison was carried out among epoxy matrix laminates - glass fiber reinforced aluminum laminate (GLARE) and carbon fiber reinforced aluminum laminate (CARALL) - and FML constructed with aluminum and carbon fiber reinforced polybenzoxazine. The mechanical properties were characterized by drop weight impact and flexural methods, and the polybenzoxazine curing behavior through differential scanning calorimetry (DSC). Polybenzoxazine FML generated increasing of: 18% of maximum load, 11% of maximum elongation under flexure and 7.5% of impact energy absorption compared to other fiber metal laminates.

Download Full-text

Polymer/Iron-Based Layered Double Hydroxides as Multifunctional Wound Dressings

Pharmaceutics ◽

10.3390/pharmaceutics12111130 ◽

2020 ◽

Vol 12 (11) ◽

pp. 1130

Author(s):

Mariana Pires Figueiredo ◽

Ana Borrego-Sánchez ◽

Fátima García-Villén ◽

Dalila Miele ◽

Silvia Rossi ◽

...

Keyword(s):

Drug Release ◽

High Performance ◽

Mechanical Performance ◽

Release Kinetics ◽

Wound Dressings ◽

In Vitro Drug Release ◽

Improved Performance ◽

Double Hydroxide ◽

Double Hydroxides

This work presents the development of multifunctional therapeutic membranes based on a high-performance block copolymer scaffold formed by polyether (PE) and polyamide (PA) units (known as PEBA) and layered double hydroxide (LDH) biomaterials, with the aim to study their uses as wound dressings. Two LDH layer compositions were employed containing Mg2+ or Zn2+, Fe3+ and Al3+ cations, intercalated with chloride anions, abbreviated as Mg-Cl or Zn-Cl, or intercalated with naproxenate (NAP) anions, abbreviated as Mg-NAP or Zn-NAP. Membranes were structurally and physically characterized, and the in vitro drug release kinetics and cytotoxicity assessed. PEBA-loading NaNAP salt particles were also prepared for comparison. Intercalated NAP anions improved LDH–polymer interaction, resulting in membranes with greater mechanical performance compared to the polymer only or to the membranes containing the Cl-LDHs. Drug release (in saline solution) was sustained for at least 8 h for all samples and release kinetics could be modulated: a slower, an intermediate and a faster NAP release were observed from membranes containing Zn-NAP, NaNAP and Mg-NAP particles, respectively. In general, cell viability was higher in the presence of Mg-LDH and the membranes presented improved performance in comparison with the powdered samples. PEBA containing Mg-NAP sample stood out among all membranes in all the evaluated aspects, thus being considered a great candidate for application as multifunctional therapeutic dressings.

Download Full-text

Preparation of Long Sisal Fiber-Reinforced Polylactic Acid Biocomposites with Highly Improved Mechanical Performance

Polymers ◽

10.3390/polym13071124 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1124

Author(s):

Zhifang Liang ◽

Hongwu Wu ◽

Ruipu Liu ◽

Caiquan Wu

Keyword(s):

Mechanical Properties ◽

Polylactic Acid ◽

Mechanical Performance ◽

Tensile Elongation ◽

Sisal Fiber ◽

Fiber Reinforced ◽

Impact Performance ◽

The Matrix ◽

Blending Process ◽

Extension Direction

Green biodegradable plastics have come into focus as an alternative to restricted plastic products. In this paper, continuous long sisal fiber (SF)/polylactic acid (PLA) premixes were prepared by an extrusion-rolling blending process, and then unidirectional continuous long sisal fiber-reinforced PLA composites (LSFCs) were prepared by compression molding to explore the effect of long fiber on the mechanical properties of sisal fiber-reinforced composites. As a comparison, random short sisal fiber-reinforced PLA composites (SSFCs) were prepared by open milling and molding. The experimental results show that continuous long sisal fiber/PLA premixes could be successfully obtained from this pre-blending process. It was found that the presence of long sisal fibers could greatly improve the tensile strength of LSFC material along the fiber extension direction and slightly increase its tensile elongation. Continuous long fibers in LSFCs could greatly participate in supporting the load applied to the composite material. However, when comparing the mechanical properties of the two composite materials, the poor compatibility between the fiber and the matrix made fiber’s reinforcement effect not well reflected in SSFCs. Similarly, the flexural performance and impact performance of LSFCs had been improved considerably versus SSFCs.

Download Full-text

Wastes from Agricultural Silage Film Recycling Line as a Potential Polymer Materials

Polymers ◽

10.3390/polym13091383 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1383

Author(s):

Jerzy Korol ◽

Aleksander Hejna ◽

Klaudiusz Wypiór ◽

Krzysztof Mijalski ◽

Ewelina Chmielnicka

Keyword(s):

Vinyl Acetate ◽

Thermal Performance ◽

Mechanical Performance ◽

Ethylene Vinyl Acetate ◽

Tensile Tests ◽

Solid Particles ◽

Polymer Materials ◽

Slight Reduction ◽

Scanning Calorimetry ◽

Crystallinity Degree

The recycling of plastics is currently one of the most significant industrial challenges. Due to the enormous amounts of plastic wastes generated by various industry branches, it is essential to look for potential methods for their utilization. In the presented work, we investigated the recycling potential of wastes originated from the agricultural films recycling line. Their structure and properties were analyzed, and they were modified with 2.5 wt % of commercially available compatibilizers. The mechanical and thermal performance of modified wastes were evaluated by tensile tests, thermogravimetric analysis, and differential scanning calorimetry. It was found that incorporation of such a small amount of modifiers may overcome the drawbacks caused by the presence of impurities. The incorporation of maleic anhydride-grafted compounds enhanced the tensile strength of wastes by 13–25%. The use of more ductile compatibilizers—ethylene-vinyl acetate and paraffin increased the elongation at break by 55–64%. The presence of compatibilizers also reduced the stiffness of materials resulting from the presence of solid particles. It was particularly emphasized for styrene-ethylene-butadiene-styrene and ethylene-vinyl acetate copolymers, which caused up to a 20% drop of Young’s modulus. Such effects may facilitate the further applications of analyzed wastes, e.g., in polymer film production. Thermal performance was only slightly affected by compatibilization. It caused a slight reduction in polyethylene melting temperatures (up to 2.8 °C) and crystallinity degree (up to 16%). For more contaminated materials, the addition of compatibilizers caused a minor reduction in the decomposition onset (up to 6 °C). At the same time, for the waste after three washing cycles, thermal stability was improved. Moreover, depending on the desired properties and application, materials do not have to go through the whole recycling line, simplifying the process, reducing energy and water consumption. The presented results indicate that it is possible to efficiently use the materials, which do not have to undergo the whole recycling process. Despite the presence of impurities, they could be applied in the manufacturing of products which do not require exceptional mechanical performance.

Download Full-text

Star-shaped arylacetylene resins derived from silicon

Journal of Polymer Engineering ◽

10.1515/polyeng-2020-0083 ◽

2020 ◽

Vol 40 (8) ◽

pp. 676-684

Author(s):

Niping Dai ◽

Junkun Tang ◽

Manping Ma ◽

Xiaotian Liu ◽

Chuan Li ◽

...

Keyword(s):

High Performance ◽

Room Temperature ◽

Mechanical Test ◽

Flexural Modulus ◽

Mechanical Analysis ◽

Reinforced Composites ◽

Scanning Calorimetry ◽

Chemical Structures ◽

Structures And Properties ◽

High Performance Resin

AbstractStar-shaped arylacetylene resins, tris(3-ethynyl-phenylethynyl)methylsilane, tris(3-ethynyl-phenylethynyl) phenylsilane, and tris (3-ethynyl-phenylethynyl) silane (TEPHS), were synthesized through Grignard reaction between 1,3-diethynylbenzene and three types of trichlorinated silanes. The chemical structures and properties of the resins were characterized by means of nuclear magnetic resonance, fourier-transform infrared spectroscopy, Haake torque rheomoter, differential scanning calorimetry, dynamic mechanical analysis, mechanical test, and thermogravimetric analysis. The results show that the melt viscosity at 120 °C is lower than 150 mPa⋅s, and the processing windows are as wide as 60 °C for the resins. The resins cure at the temperature as low as 150 °C. The good processabilities make the resins to be suitable for resin transfer molding. The cured resins exhibit high flexural modulus and excellent heat-resistance. The flexural modulus of the cured TEPHS at room temperature arrives at as high as 10.9 GPa. Its temperature of 5% weight loss (Td5) is up to 697 °C in nitrogen. The resins show the potential for application in fiber-reinforced composites as high-performance resin in the field of aviation and aerospace.

Download Full-text