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1.
Three series of crosslinked octadecyl acrylate and acrylic acid copolymers were prepared through suspension copolymerization based on acrylic acid content (10, 30, 50%wt. ratio). Divinyl benzene (DVB) was used as a crosslinker with different weight ratios (1, 4 and 10%). Isopropyl alcohol or dioctyl phthalate and methyl benzoate were used as two different reaction solvents in the presence of ABIN as initiator. The prepared crosslinked copolymers were characterized by SEM, TGA and FTIR spectroscopic analyses. The prepared polymers were coated onto poly(ethylene terephethalate) nonwoven fiber (NWPET). The effect of copolymerization feed composition, crosslinker wt% and reaction media or solvent on swelling properties of crosslinked polymers were studied through the oil absorption tests in toluene and 10% of diluted crude oil with toluene. It was noticed that the maximum swelling of crosslinked copolymers was increased from 30 to 100 g/g after grafting of copolymers onto NWPET.  相似文献   

2.
Summary: A new class of fibre reinforced commodity thermoplastics suited for injection moulding and direct processing applications has been developed using man-made cellulosic fibres (Rayon tire yarn, Tencel, Viscose, Carbacell) and thermoplastic commodity polymers, such as polypropylene (PP), polyethylene (PE), high impact polystyrene (HIPS), poly(lactic acid) (PLA), and a thermoplastic elastomer (TPE) as the matrix polymer. For compounding, a specially adapted double pultrusion technique has been employed which provides composites with homogeneously distributed fibres. Extensive investigations were performed with Rayon reinforced PP in view of applications in the automotive industry. The Rayon-PP composite is characterized by high strength and an excellent impact behaviour as compared with glass fibre reinforced PP, thus permitting applications in the field of engineering thermoplastics such as polycarbonate/acrylonitrile butadiene styrene blends (PC/ABS). With the PP based composites the influence of material parameters (e.g. fibre type and load, coupling agent) were studied and it has been demonstrated how to tailor the desired composite properties as modulus and heat distortion temperature (HDT) by varying the fibre type or adding inorganic fillers. Man-made cellulose fibers are also suitable for the reinforcement of further thermoplastic commodity polymers with appropriate processing temperatures. In case of PE modulus and strength are tripled compared to the neat resin while Charpy impact strength is increased five-fold. For HIPS mainly strength and stiffness are increased, while for TPE the property profile is changed completely. With Rayon reinforced PLA, a fully biogenic and biodegradable composite with excellent mechanical properties including highly improved impact strength is presented.  相似文献   

3.
伍聪  杨丹丹  吴刚  陈思翀 《高分子学报》2021,(2):176-185,I0004
通过将双端羟基的聚己内酯(PCL)、聚乳酸(PLA)预聚物以及苯基次磷酸离子盐扩链得到一种含苯基次磷酸盐的离子共聚物,将其与聚磷酸铵(APP)复合用于协同改性聚乳酸,离聚物中苯基次磷酸盐结构与APP具有优异的协同阻燃PLA的作用,同时该离聚物中PLA与苯基次磷酸盐结构有效提升了APP在PLA中的分散能力,最后该离聚物中PCL柔性链段有效改善了PLA的韧性,最终得到更高效阻燃性能且韧性也较好改善的PLA/PCLA-PIU/APP复合材料.一方面,离聚物中苯基次磷酸盐结构与APP协同有效促进了PLA的成炭,形成更连续致密的炭层从而阻隔可燃气体的释放,达到更好的阻燃效果.锥形量热、残炭的扫描电子显微镜(SEM)、能谱分析(EDS)、拉曼光谱等测试证实了这一结果,与纯PLA以及仅使用APP的PLA/APP相比,PLA/PCLA-PIU/APP的热释放速率与总热释放均降低,同时残炭的石墨化程度更高,形成了更为致密的炭层.另一方面,力学性能测试结果表明,离聚物中PCL柔性链段的存在使得与APP复合改性后的PLA的韧性相比纯PLA和PLA/APP有较大的提升;SEM测试表明,离聚物中PLA与苯基次磷酸盐结构起到增容作用,提升了APP在PLA中的分散性.  相似文献   

4.
A new phosphorus‐based organic additive (PDA) was designed and successfully synthesized using a three‐component reaction for improvement of the thermal and combustion resistance of polylactic acid (PLA). For compensate for mechanical properties of PLA, hydroxyapatite nanoparticles was modified via in situ surface modification with PDA and was used for preparation of PLA nanocomposites. The structure and morphology as well as thermal, combustion, and mechanical properties of the all PLA systems were investigated. The X‐ray diffraction (XRD) and field‐emission scanning electron microscopy (FE‐SEM) results indicated that the presence of PDA as surface modifier has been necessary for a desirable dispersion of hydroxyapatite (HA) nanoparticles in the PLA matrix. The thermal, combustion, and mechanical properties of the PLA system films were investigated using thermogravimetric analysis (TGA), microscale combustion calorimeter (MCC), and tensile test, respectively. The initial decomposition temperature and char residue of PLA containing 6 mass% of PDA along with 2 mass% HA nanoparticles were increased 20°C and 12% respectively, compared with that of the neat PLA. The peak of heat release rate was decreased from 566 W/g for the neat PLA to 412 W/g for PLA containing 2 mass% of PDA along with 6 mass% HA nanoparticles. By incorporation of only 2 mass% HA nanoparticles and 6 mass% of PDA, the tensile strength was obtained 51 MPa higher than that of the neat PLA.  相似文献   

5.
Mixtures of two cleavable dimethacrylate crosslinkers, the hydrolyzable di(methacryloyloxy‐1‐ethoxy)methane (DMOEM) and the thermolyzable 1,1‐ethylenediol dimethacrylate (EDDMA), were used for the preparation of neat crosslinker polymer networks, randomly crosslinked polymer networks of methyl methacrylate (MMA), and star polymers of MMA, using group transfer polymerization in tetrahydrofuran (THF). All star polymers and randomly crosslinked polymer networks containing mixtures of the hydrolyzable DMOEM and the thermolyzable EDDMA crosslinkers gave THF‐soluble final products when subjected to sequential thermolysis and hydrolysis, in this order. When applying sequential hydrolysis and thermolysis, only the star polymers with an EDDMA crosslinker content equal to or higher than 50% gave THF‐soluble final products. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5853–5870, 2009  相似文献   

6.
The tensile strength and thermal stability of polylactide (PLA) were significantly improved through chemical crosslinking. However, it became much more rigid and brittle. To obtain a material with good thermal stability and enhanced ability to plastic deformation, chemical crosslinked PLA with 0.5 wt % triallyl isocyanurate and 0.5 wt % dicumyl peroxide was blended with different contents of dioctyl phthalate (DOP). The advantage of using DOP is that it does not crystallize, has low glass transition temperature, and is miscible with PLA. The morphology and the thermal and mechanical properties of the crosslinked PLA and the blends of crosslinked PLA with various contents of DOP were investigated by means of scanning electron microscope, differential scanning calorimetry, tensile test, and dynamic mechanical analysis. The rheological properties of samples were also explored by using a capillary rheometer. The results showed that the DOP was an effective plasticizer for the chemical crosslinked PLA, resulting in a significantly decreased Tg, lower yield stress, and improved elongation at break. The plasticization effect was enhanced by adding higher DOP content. In addition, the DOP enhanced the crystallinity of crosslinked PLA, and all the crosslinked samples showed better heat stability than neat PLA. The apparent viscosity of the blends decreased with the increase of DOP content and a phase separation occurred when the content of DOP exceeded 12.5 wt %. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1136–1145, 2009  相似文献   

7.
Green and renewable foaming poly(lactic acid) (PLA) represents one of the promising developments in PLA materials. This study is the first to use the lignin graft PLA copolymer (LG‐g‐PLA) to improve the foamability of PLA as a biobased nucleating agent. This agent was synthesized via ring‐opening polymerization of lignin and lactide. The effects of LG‐g‐PLA on cell nucleation induced by the crystallization, rheological behavior, and foamability of PLA were evaluated. Results indicated that LG‐g‐PLA can improve the crystallization rate and crystallinity of PLA, and play a significant nucleation role in the microcellular foam processing of PLA. LG‐g‐PLA improved the foam morphology of PLA, obtaining a reduced and uniform cell size as well as increased expansion ratio and cell density. With the addition of 3 wt% LG‐g‐PLA content, the PLA/LG‐g‐PLA foams increased the compressive strength 1.6 times than that of neat PLA foams. The improved foaming properties of PLA via a biobased nucleating agent show potential for the production and application of green biodegradable foams.  相似文献   

8.
Crosslinked materials derived from poly(lactide) (PLA) have been produced by radiation modification in the presence of a suitable crosslinker (triallyl isocyanurate) (TAIC). The crosslinking structure introduced in PLA films has not only much improved the heat stability but also their mechanical properties. The properties of crosslinked samples are governed by crosslinking density and these improvement seemed to increase with radiation dose. This implied that the three dimensional networks have been introduced in material by radiation and the crosslinking density depended on the structure and length of PLA chains. Biodegradability of PLA was also determined by an enzymatic degradation test and burying in compost at 55 °C. Differing with PLLA, PDLA was insignificantly degraded by proteinase K. The degradation rate of PLA in compost was postponed with the introduction of crosslinks.  相似文献   

9.
Poly(lactic acid)‐grafted multiwalled carbon nanotubes (MWNT‐g‐PLA) were prepared by the direct melt‐polycondensation of L ‐lactic acid with carboxylic acid‐functionalized MWNT (MWNT‐COOH) and then mixed with a commercially available neat PLA to prepare PLA/MWNT‐g‐PLA nanocomposites. Morphological, thermal, mechanical, and electrical characteristics of PLA/MWNT‐g‐PLA nanocomposites were investigated as a function of the MWNT content and compared with those of the neat PLA, PLA/MWNT, and PLA/MWNT‐COOH nanocomposites. It was identified from FE‐SEM images that PLA/MWNT‐g‐PLA nanocomposites exhibit good dispersion of MWNT‐g‐PLA in the PLA matrix, while PLA/MWNT and PLA/MWNT‐COOH nanocomposites display MWNT aggregates. As a result, initial moduli and tensile strengths of PLA/MWNT‐g‐PLA composites are much higher than those of neat PLA, PLA/MWNT, and PLA/MWNT‐COOH, which stems from the efficient reinforcing effect of MWNT‐g‐PLA in the PLA matrix. In addition, the crystallization rate of PLA/MWNT‐g‐PLA nanocomposites is faster than those of neat PLA, PLA/MWNT, and PLA/MWNT‐COOH, since MWNT‐g‐PLA dispersed in the PLA matrix serves efficiently as a nucleating agent. It is interesting that, unlike PLA/MWNT nanocomposites, surface resistivities of PLA/MWNT‐g‐PLA nanocomposites did not change noticeably depending on the MWNT content, demonstrating that MWNTs in PLA/MWNT‐g‐PLA are wrapped with the PLA chains of MWNT‐g‐PLA. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

10.
Polylactide (PLA) crosslinked by using both triallyl isocyanurate (TAIC) and electron radiation or using dicumyl peroxide (DCP) was studied with the aim of examining the behaviour of the modified polymer under various environmental conditions. Thus, the polymer samples were subjected to composting in an industrial pile, exposed to proteinase K, or incubated in sea water. The number-average molecular weight (Mn), melt flow index (MFI), crystallinity (χ), tensile strength (σM) and mass loss (in the case of samples treated with proteinase K) were determined. It was found that neat PLA irradiated with high-energy electrons underwent degradation that increased during composting. As a result, the value of Mn of this polymer dramatically decreased. It appeared that PLA crosslinked with TAIC and electron radiation contained, in addition to the crosslinked phase, a phase strongly degraded by this radiation, which facilitated hydrolytic degradation during composting. The σM value of PLA crosslinked with TAIC and electron radiation rapidly decreased during composting, whereas that of PLA crosslinked chemically and composted for three weeks slightly increased. As the electron radiation dose increased, the mass loss of PLA containing TAIC and treated with proteinase K decreased, which indicated that the physical crosslinking of PLA hindered enzymatic degradation of this polymer. Important changes in both neat and physically crosslinked PLA incubated in sea water for nine weeks were not detected.  相似文献   

11.
以丙三醇、己二酸为原料,通过熔融缩聚合成了新型聚乳酸(PLA)增韧改性剂聚己二酸丙三醇酯(PGA).利用傅立叶变换红外光谱(FT-IR),核磁共振氢谱(1H-NMR)及凝胶渗透色谱(GPC)等方法对不同反应温度条件下PGA的分子结构进行了表征.同时通过熔融共混制备了PGA/PLA共混物,并测试了共混物的冲击性能,利用差示扫描量热仪(DSC)和扫描电子显微镜(SEM)对其热性能及相形貌进行了表征.结果表明:PGA可以有效增韧聚乳酸,160℃下合成的PGA增韧性最佳,冲击强度达到48.0 J/m,较纯聚乳酸提高了3倍.PGA分子支化结构的差异对PGA/PIA的共混形态有明显的影响,从而进一步影响其增韧效果.  相似文献   

12.
Polylactic acid (PLA) and thermoplastic starch (TPS) are known as bio‐based and biodegradable thermoplastic polymers that can be used in different applications owing to their inherent physical and mechanical properties. In order to reduce the higher costs of PLA and tuning its physical and mechanical properties suitable for short life packaging applications, blending of PLA with the TPS, more economical biodegradable polymer, has been considered in academic and industrial researches. However, melt blending of PLA with TPS without compatibilization process caused some drawbacks such as coarsening morphology and declining mechanical properties and ductility because of thermodynamic immiscibility, which may restrict its usage in packaging applications. Subsequently, our approach in this research is compatibilization of PLA/TPS blends by utilization of primary well tuning of TPS formulation with a combination of sorbitol and glycerol plasticizers. In this work, the wide composition range of melt mixed PLA/TPS blends was prepared using a laboratory twin screw extruder. The effects of microstructure on the rheological and mechanical properties of PLA/TPS blends were studied using different methods such as scanning electron microscopy (SEM) images, contact angle, oscillatory shear rheological measurements, and tensile and impact strength mechanical tests. The rheological and mechanical properties were interpreted according to the morphological features and considering the possibility of plasticizer migration from TPS to PLA phase during melt blending. Reduction in complex viscosity and storage modulus of PLA matrix samples indicates the improved melt processability of blends. Finally, in comparison with mechanical results reported in literature, our simple approach yielded the blends with elastic modulus and ductility comparable with those of chemically compatibilized PLA/TPS blends.  相似文献   

13.
《高分子科学》2019,37(12):1273-1282
Polylactide(PLA), methyl methacrylate-butadiene-styrene copolymer(MBS), and poly(propylene carbonate) polyurethane(PPCU) were blended and subjected to blown film process. The rheological, mechanical, morphological, thermal, and crystalline properties of the PLA/MBS/PPCU ternary blends and the mechanical properties of the resulting films were studied. Results of mechanical test showed that PPCU and MBS could synergistically toughen PLA. The impact strength of 50/10/40 PLA/MBS/PPCU blend(74.7 k J/m~2)was about 7.5 times higher than that of the neat PLA(10.8 k J/m~2), and the elongation at break of 50/10/40 PLA/MBS/PPCU blend(276.5%) was higher by about 45 times that of PLA(6.2%). The tear strength of PLA/MBS/PPCU films was 20 k N/m higher than that of PLA, and the elongation at break(MD/TD) of 50/10/40 PLA/MBS/PPCU films was 271.1%/222.3%, whereas that of PLA was only 2.7%/3.0%. POM observations displayed that the density of spherulite nucleation increased and the size of crystalline particles decreased with the addition of MBS. With increasing PPCU content from 5% to 20%, the density of spherulite nucleation increased and the size of crystalline particles decreased continuously, but the nucleation density of spherulites was slightly lowered with increasing PPCU content from 30% to 40%. The PLA/MBS/PPCU films exhibited excellent mechanical properties, which expanded the application range of these biodegradable films.  相似文献   

14.
Crosslinking structures can be partly introduced into PLA by melt mixing in a twin screw extruder with dicumyl peroxide (DCP) and ethoxylated bisphenol A dimethacrylates (Bis‐EMAs) as a crosslinking coagent. The study of DCP and Bis‐EMA contents on the melt rheology, thermal properties, dynamic mechanical properties and morphology of the reactive extruded pellets is presented. The results show that PLA with a DCP content higher than 3 phr exhibits increases in both the melt modulus and complex viscosity as compared with PLA. The introduction of DCP into PLA improved the thermal stability of the PLA. PLAs with various Bis‐EMA contents showed the optimum storage modulus and complex viscosity to occur at 5 phr Bis‐EMAs. Moreover, the glass transition, cold crystallization and melting temperature of PLAs decreased with increasing Bis‐EMA content. The crystallinity of the partly crosslinked PLAs was lower than that of PLA. Similar to the rheological results, the thermo‐mechanical properties showed that the storage modulus and loss modulus of the partly crosslinked PLAs increased with increasing Bis‐EMA contents up to 5 phr. In addition, these partly crosslinked PLAs showed rough surface or sea island‐like structure. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

15.
The research focused on enhancing the mechanical properties and thermal stability of bio-composites with natural flours and improving the interfacial adhesion between biodegradable polymer and flour. The tensile and flexural strength of the PLA bio-composites decreased with increasing flour addition. However, a 3% loading of the compatibilizer in the PLA bio-composite increased this strength up to that observed with the 10% loading flour. The degradation temperature of PLA was decreased by the flour but destarched cassava flour had higher thermal stability on account of its higher lignin content than pineapple flour. This means that the PLA bio-composites with destarched cassava flour had higher thermal stability than those with the pineapple flour. In addition, the thermal degradation temperature was increased by adding MAPLA. The compatibilizer improved the crystallinity of PLA, which enhanced the mechanical strength of the PLA bio-composites. As the pineapple flour and destarched cassava flour 30% loading was increased, the HDT of the PLA bio-composites increased from 56.8?°C to ~66.3 and 69.7?°C, respectively. The thermal aging test showed no reduction in strength of the neat PLA. However, the PLA bio-composites showed a gradual decrease in tensile strength with increasing number of cycles. Moreover, the shrinkage ratio of the neat PLA was 5% of that found with the PLA resin.  相似文献   

16.
The invention of inverse vulcanization provides great opportunities for generating functional polymers directly from elemental sulfur, an industrial by‐product. However, unsatisfactory mechanical properties have limited the scope for wider applications of these exciting materials. Here, we report an effective synthesis method that significantly improves mechanical properties of sulfur‐polymers and allows control of performance. A linear pre‐polymer containing hydroxyl functional group was produced, which could be stored at room temperature for long periods of time. This pre‐polymer was then further crosslinked by difunctional isocyanate secondary crosslinker. By adjusting the molar ratio of crosslinking functional groups, the tensile strength was controlled, ranging from 0.14±0.01 MPa to 20.17±2.18 MPa, and strain was varied from 11.85±0.88 % to 51.20±5.75 %. Control of hardness, flexibility, solubility and function of the material were also demonstrated. We were able to produce materials with suitable combination of flexibility and strength, with excellent shape memory function. Combined with the unique dynamic property of S?S bonds, these polymer networks have an attractive, vitrimer‐like ability for being reshaped and recycled, despite their crosslinked structures. This new synthesis method could open the door for wider applications of sustainable sulfur‐polymers.  相似文献   

17.
This study is aimed to explore the properties of cellulose nanocrystals (CNC)/polyvinyl alcohol (PVA) composite films with and without 1,2,3,4‐butane tetracarboxylic acid (BTCA), a nontoxic crosslinker. CNC and CNC‐PVA nanocomposite films are prepared using solution‐casting technique. Differential scanning calorimetry (DSC) analyses show that crosslinking increased the glass transition temperature but reduced the melting temperature and crystallinity. Furthermore, high CNC concentrations in the PVA matrix interfere with PVA crystallinity, whereas in specific ratio between CNC and PVA, two different crystalline structures are observed within the PVA matrix. Film surfaces and fracture topographies characterized using scanning electron microscope indicate that at certain CNC‐PVA ratios, micron‐sized needle‐like crystals have formed. These crystalline structures correlate with the remarkable improvement in mechanical properties of the CNC‐PVA nanocomposite films, that is, enhanced tensile strain and toughness to 570% and 202 MJ m?3, respectively, as compared to pristine PVA. BTCA enhances the tensile strain, ultimate tensile stress, toughness, and modulus of CNC films compared to pristine CNC films. Water absorption of crosslinked CNC and CNC‐PVA nanocomposite films is significantly reduced, while film transparency is significantly improved as a function of PVA and crosslinker content. The presented results indicate that CNC‐PVA nanocomposite films may find applications in packaging, and though materials applications.  相似文献   

18.
Poly(lactic acid)-based ternary blends consisting of poly(lactic acid)(PLA),cellulolytic enzyme lignin(CEL),and polyolefine grafting maleic anhydride(PGMA) were prepared by extrusion blending and the mechanical properties and the morphology of the ternary blends were investigated.It was found that the mechanical properties varied with various loading of the components in the blends.Compared to neat PLA,the tensile strength and the Young’s modulus of the ternary blends were decreased,but the elongation at break and the impact strength were effectively improved.Scanning electron microscope observations revealed that the CEL plays a bridging role between PLA and PGMA,enhancing the miscibility between them and resulting in the improvement of ductility and toughness of the ternary blends.Considering the cost and performance,we obtained the optimal blend PLA/CEL/ PGMA(80/20/20,w/w/w),of which the impact strength and the elongation at break were doubled as that of neat PLA,and the tensile strength remained moderate.  相似文献   

19.
A novel polyacrylamide/polyacrylic acid (PAAm/PAA) double network (DN) nanocomposite (NC) hydrogel had been synthesized by two‐step solution polymerization. The PAAm network was crosslinked by inorganic clay while the PAA network was crosslinked by a chemical crosslinker. The chemical structure of the network was confirmed by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and transmission electron microscopy (TEM). The swelling and mechanical strength properties of PAAm/PAA hydrogels were examined. The results showed that a DN hydrogel achieved both a high swelling capacity of 1219 g/g in deionized water and 124 g/g in 0.9 wt% NaCl solution and high compressive stress of 21.5 kPa in a high water content of 99.58%. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

20.
The objective of this work is to enhance the toughness of In the current study, inherently brittle polylactic acid (PLA) has been toughened using a biobased polyester without compromising the biocompatibility, renewability, strength and thermal properties of PLA. For this purpose, biodegradable Renewable resources resource based flexible aliphatic polyester (BBPE) has been synthesized and the same has been confirmed by FTIR and 1H NMR. Melt blending of BBPE elastomer with PLA in presence of free radical initiator dicumyl peroxide (DCP) leads to the development of crosslinked PLA/BBPE (PBE) blends of tunable properties. Additionally, the mechanical, morphological, thermal, crosslink density and water absorption behaviour of PBE blends were explored. It was observed that the synthesized biobased BBPE elastomers contribute to toughening of the PLA matrix consequently, improving the its impact strength and elongation at break. of the blend  相似文献   

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