Effects of porosity,fiber size,and layering sequence on sound absorption performance of needle‐punched nonwovens

The relationships between the material parameters, i.e., the fiber fineness, porosity, areal density, layering sequence, and airflow resistivity with the normal‐incidence sound absorption coefficient of nonwoven composites consisting of three layers have been studied. The monofiber or multifiber needle‐punched nonwovens included poly(lactic acid) (PLA), polypropylene (PP), glass fiber, and hemp fibers. Air flow resistivity was statistically modeled and was found to increase with decreasing fiber size and nonwoven porosity. The former models developed for glass fiber mats in the literature were found to be inconsistent with the air flow resistance of the nonwovens reported below. The effects of the layering sequence on air flow resistivity and sound absorption were obtained. It was found that when the layer including reinforcement fibers, i.e., hemp or glass fiber, faced the air flow/sound source, the air flow resistance and the absorption coefficient were higher than the case when the layer including reinforcement fibers was farthest from the air flow/sound source. The difference was more pronounced if there was a greater difference between the resistivity values of the constituent layers of the nonwoven composite. Sound absorption coefficient was statistically modeled in terms of air flow resistivity and frequency. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Three‐dimensional nonwoven flax fiber reinforced polylactic acid biocomposites

Three‐dimensional (3D) shell‐structured PLA/Flax biocomposites were fabricated using a novel method incorporating the 3D nonwoven web‐forming process. PLA and flax fibers were blended in the fiber opening stage and converted to webs on the 3D mold using the air‐laying principle. The 3D webs were then consolidated by through‐air thermal bonding. The compression molding technique was used finally to convert the 3D webs to the biocomposites. The relationship between the main process parameters and the properties of the biocomposites was investigated. The results show that with increasing flax fiber content, the crush failure load, total energy absorption, specific energy absorption, and crush efficiency increased. The crushing properties decreased with increased molding temperature, but the crushing properties are not significantly affected by the molding time. The physical properties of 3D biocomposites were also evaluated and the appropriate processing parameters for 3D biocomposites were established. POLYM. COMPOS., 35:1244–1252, 2014. © 2013 Society of Plastics Engineers     

Development,characterization, and modeling of environmentally friendly open‐cell acoustic foams

This study shows the development of new polymeric open‐cell foams from polypropylene (PP) and polylactide (PLA) resins with a focus on sound absorption properties and modeling of these foams. The objective is to develop new environmentally friendly foams to replace the existing non‐recyclable Polyurethane foams are currently used for sound insulation in industry. Through this research, open‐cell foams of about 90% porosity were fabricated from PP and PLA. These resins were selected since PP is a recyclable thermoplastic polymer, and PLA is a bio‐based thermoplastic polymer made from renewable resources. Polyurethane (PU) foam which is currently used for sound absorption and noise control in industry was compared to the fabricated PP and PLA foams. As the first attempt to fabricate environmentally friendly acoustic foams, the resulting foam structures show improved properties as compared to the existing materials. The average absorption of PP and PLA foams fabricated is in the range of 0.42–0.55 which is comparable or even higher than the average absorption of PU foam. To better understand the effect of structural and material properties on sound absorption and further improve the acoustic performance of bio‐based foams, an analytical model based on Johnson–Champoux–Allard model was used to numerically simulate the acoustic performance of foams under study. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Mechanical and acoustic performance of compression‐molded open‐cell polypropylene foams

Open‐cell materials are lightweight and multifunctional capable of absorbing acoustic energy and supporting mechanical load. The acoustic and mechanical performance of open‐cell materials can be optimized through processing. In this article, the relationships between processing parameters and acoustic and mechanical performance are shown for polypropylene (PP) foams. PP foam samples are fabricated using a combined compression molding and particulate leaching process. The results from a parametric study showed that both salt size and salt to polymer ratio affect the acoustic and mechanical performance of open‐cell PP foams. As salt size increases, cell size increased and cell density decreased. The salt to polymer ratio had opposite affect on cell density, and increasing the salt to polymer mass ratio increased the open‐cell content. The airflow resistivity decreased significantly by increasing the cell size, which means that foam samples with smaller cell size have better sound absorption. When foam samples were thin, smaller cell sizes produced better sound absorption; however, as thickness of the sample increases, medium cell size offered the best acoustic performance. The compressive strength of the foams was increased by increasing the relative density. Acoustic performance results from the parametric study were compared to the Johnson‐Allard model with good agreement. Finally, optimal cellular morphologies for acoustic absorption and mechanical performance were identified. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical and thermal characterization of compression moulded polylactic acid natural fiber composites reinforced with hemp and lyocell fibers

This research evaluates the effects of PLA/PP blend ratio and Lyocell/hemp mixture ratio on the morphology, water absorption, mechanical and thermal properties of PLA‐based composites. The composites were fabricated with 30 mass % hemp using compression moulding. As a reference composites made from PP were also studied. Combining of hemp and Lyocell in PLA composite leads to the reduction of moisture absorption and can improve the impact, tensile, flexural properties when compared with PLA/hemp. Composite based on the PLA/PP blend‐matrix could not improve the tensile and flexural properties compared with PLA/hemp, however; the lighter composite with better impact properties was obtained. The crystallization temperature of the PLA‐PP/hemp increased compared with pure PLA. This result was also confirmed by the SEM micrographs. The moisture absorption of PLA‐PP/hemp was higher than PLA/hemp. Based on theoretical analysis of DMTA data, there was favorable adhesion in all composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40534.     

羊毛粉/PP共混纺丝和复合纺丝纤维的研究

采用高压空气粉碎羊毛制得的羊毛粉,与聚丙烯(PP)熔融共混纺丝和皮芯型复合纺丝,分别制得羊毛粉/PP共混纤维和复合纤维。对比分析了羊毛粉/PP共混纤维、复合纤维及纯PP纤维的结构和性能。结果表明:羊毛粉/PP共混纤维的断裂强度、初始模量高于复合纤维及纯PP纤维,其大小顺序依次为共混纤维、纯PP纤维、复合纤维;羊毛粉/PP共混纤维的表面染色深度(K/S值)高于复合纤维及PP纤维,其大小顺序依次为共混纤维、复合纤维、纯PP纤维;羊毛粉/PP共混纤维和复合纤维的回潮率均高于纯PP纤维,其大小顺序依次为复合纤维、共混纤维、纯PP纤维。     

Nonwoven polylactic acid and flax biocomposites

Flax fiber‐reinforced polylactic acid (PLA) biocomposites were made using a new technique incorporating an air‐laying nonwoven process. Flax and PLA fibers were blended and converted to fiber webs in the air‐laying process. Composite prepregs were then made from the fiber webs. The prepregs were finally converted to composites by compression molding. The relationship between the main process variables and the properties of the biocomposite was investigated. It was found that with increasing flax content, the mechanical properties increased. The maximum tensile strength of 80.3 MPa, flexural strength of 138.5 MPa, tensile modulus of 9.9 GPa and flexural modulus of 7.9 GPa were achieved. As the molding temperature and molding time increased, the mechanical properties decreased. The thermal and morphological properties of the biocomposites were also studied. The appropriate processing parameters for the biocomposites were established for different fiber contents. POLYM. COMPOS., 34:1611–1619, 2013. © 2013 Society of Plastics Engineers     

Structural characterization of polypropylene/poly(lactic acid) bicomponent meltblown

The bicomponent meltblown process offers to associate two polymers in the same fiber generating fibrous media with new properties. In this study, we associate polypropylene (PP) and poly(lactic acid) (PLA), from renewable sources, polymers. The influence of primary air flow rate and the structural properties of the PP/PLA bicomponent meltblown are compared to PP and PLA monocomponent meltblown. The structural properties include fiber morphology and diameter, packing density, permeability, thermal shrinkage and crystallization. The results relate that the PP/PLA bicomponent meltblown fiber diameters are thinner than those of PLA monocomponent. Moreover, it has higher resistance to thermal shrinkage compared to PP monocomponent meltblown. The packing density and permeability are not affected by the association of PP and PLA due to low crimp effect. Two different filament formations of PP/PLA bicomponent meltblown at low and high primary air flow rate have also been observed. Lastly, this study illustrates that PP and PLA association is viable, showing the production of PP/PLA bicomponent microfiber and limited thermal shrinkage at high temperature. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44540.     

聚丙烯/分子筛共混纤维的结构与性能

用钛酸酯偶联剂对分子筛进行表面处理,按一定比例与聚丙烯(PP)切片共混纺丝,制得PP/分子筛共混纤维,研究PP/分子筛共混纤维的结构与性能。结果表明:当纤维中分子筛的质量分数为1%时,PP/分子筛共混纺丝纤维的可纺性好,断裂强度比纯PP纤维提高31.85%,上染率提高44.86%,初始模量、断裂功、回潮率均有所提高;与纯PP纤维相比,PP/分子筛共混纤维的结晶度略小、晶粒变大,取向度降低,纤维的染色性、吸湿性得到改善。分子筛与偶联剂发生化学反应,有利于分子筛和PP的结合,适当的分子筛含量时,纤维的力学性能有所提高。     

In situ fiber‐reinforced composites from blends containing polypropylene and polycaprolactone

Our study was focused on the presupposition that morphology control in immiscible polymer blend could give rise to reinforcement in composites. To investigate the effects of shear and elongational flow in polymer processing, observation of the mechanical properties and the morphology of the polypropylene/polycaprolactone (PP/PCL) blend system was performed. PP/PCL sheets were fabricated by means of a single‐screw extruder equipped with a slit‐type die to which high shear and elongational stresses were applied. For the sake of comparison, a second series of composites of identical composition was compression molded with a hot‐press machine that transmits lower shear and elongational stresses. The results indicate that the extruded sheets have better mechanical properties than those of the compression‐molded sheets, a result attributed to the generation of in situ dispersed long fiber minor phases and cocontinuous phases in the extruded composites. The differences in the crystallization behavior of the fibrous and spherically shaped components were indicated clearly by DSC curves. A PP crystalline peak indicative of in situ PP fiber formation is conspicuous around 980 cm⁻¹ (PP crystalline band) in the FTIR spectrum. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 833–840, 2004     

The effect of process parameters on the properties of elastic melt blown nonwovens: Air pressure and DCD

An elastic masterbatch and elastic melt blown nonwovens are prepared based successively on styrene-ethylene/butylene-styrene (SEBS) and polypropylene (PP) blend. The phase separation morphology, rheological properties and crystal structure of the elastic masterbatch are investigated. The results show that a compatible and stable structure is obtained in molten SEBS and PP blend with excellent mobility in the temperature range of 210–230°C. The crystallization of PP slows down resulting in a finer structure due to the restriction of the SEBS network structure with rarely change of crystalline structure. The relationship between process parameters and properties of the elastic nonwoven is also studied in detail. Air pressure and die to collector distance (DCD) have discernible effects on fiber diameter and bonding between fibers, further influencing the performances of nonwovens including porosity, tensile strength and elastic recovery. Elastic recovery is shown to be significantly more affected by DCD than by air pressure.     

Unidirectional hemp and flax EP‐ and PP‐composites: Influence of defined fiber treatments

In some technical areas, mainly in the automotive industry, glass fiber reinforced polymers are intended to be replaced by natural fiber reinforced polymer systems. Therefore, higher requirements will be imposed to the physical fiber properties, fiber‐matrix adhesion, and the quality assurance. To improve the properties of epoxy resins (EP) and polypropylene (PP) composites, flax and hemp fibers were modified by mercerization and MAH‐PP coupling agent was used for preparing the PP composites. The effects of different mercerization parameters such as concentration of alkali (NaOH), temperature, and duration time along with tensile stress applied to the fibers on the structure and properties of hemp fibers were studied and judged via the cellulose I–II lattice conversion. It was observed that the mechanical properties of the fibers can be controlled in a broad range by using appropriate mercerization parameters. Unidirectional EP composites were manufactured by the filament winding technique; at the PP matrix material, a combination with a film‐stacking technique was used. The influence of mercerization parameters on the properties of EP composites was studied with hemp yarn as an example. Different macromechanical effects are shown at hemp‐ and flax‐PP model composites with mercerized, MAH‐PP‐treated, or MAH‐PP‐treated mercerized yarns. The composites' properties were verified by tensile and flexural tests. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2150–2156, 2004     

Poly(L‐lactide)/polypropylene blends: Evaluation of mechanical,thermal, and morphological characteristics

Poly(L lactide) (PLA) was blended with polypropylene (PP) at various ratios (PLA:PP = 90 : 10, 80 : 20, 70 : 30, and 50 : 50) with a melt‐blending technique in an attempt to improve the melt processability of PLA. Maleic anhydride (MAH)‐grafted PP and glycidyl methacrylate were used as the reactive compatibilizers to induce miscibility in the blend. The PLA/PP blend at a blend ratio of 90 : 10, exhibited optimum mechanical performance. Differential scanning calorimetry and thermogravimetric analysis studies showed that the PLA/PP/MAH‐g‐PP blend had the maximum thermal stability with the support of the heat deflection temperature values. Furthermore, dynamic mechanical analysis findings revealed an increase in the glass‐transition temperature and storage modulus with the addition of MAH‐g‐PP compatibilizer. The interaction between the compatibilizers and constituent polymers was confirmed from Fourier transform infrared spectra, and scanning electron microscopy of impact‐fractured samples showed that the soft PP phase was dispersed within the PLA matrix, and a decrease in the domain size of the dispersed phase was observed with the incorporation of MAH‐g‐PP, which acted as a compatibilizer to improve the compatibility between PLA and PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Investigation of fiber orientation states in injection‐compression molded short‐fiber‐reinforced thermoplastics

Injection‐compression molding (ICM) has received increased attention because of its advantages over conventional injection molding (CIM). This article aims to investigate the effects of five dominating ICM processing parameters on fiber orientation in short‐fiber‐reinforced polypropylene (SFR‐PP) parts. A five‐layer structure of fiber orientation is found across the thickness under most conditions in ICM parts. This is quite different from the fiber orientation patterns in CIM parts. The fibers orient orderly along the flow direction in the shell region, whereas most fibers arrange randomly in the skin and the core regions. Additionally, the fiber orientation changes in the width direction, with most fibers arranging orderly along the flow direction at positions near the mold cavity wall. The results also show that the compression force, compression distance, and compression speed play important roles in determining the fiber states. Thicker shell regions, in which most fibers orient remarkably along the flow direction, can be obtained under larger compression force or compression speed. Moreover, the delay time has an obvious effect on the fiber orientation at positions far from the gate. However, the effect of compression time is found to be negligible. POLYM. COMPOS., 31:1899–1908, 2010. © 2010 Society of Plastics Engineers.     

聚丙烯/聚酯熔喷非织造材料的保暖性与透气性

通过对比研究了10种规格聚丙烯(PP)/聚酯(PET)熔喷非织造材料的厚度及单位面积质量分别对其透气性和保暖性的影响,并分析了透气性与保暖性之间的关系.结果表明:一定范围内,非织造材料的厚度和单位面积质量减小,有利于材料透气,但保暖效果减弱;非织造材料的透气性越好,保暖性越差;PP/PET混合型熔喷非织造材料是一种很好的保暖性材料.     

Experimental study and numerical simulation the air jet flow field of a dual slot sharp blunt die in the melt blowing nonwoven process

In this work, the physical model of a polymer in a melt blowing process is established and solved by introducing the numerical computation results of the air jet flow field of the dual slot sharp inset die. The influence of the melt blowing processing parameters and the die design parameters on the fiber diameter is also studied. A lower polymer throughput rate, higher polymer melt initial temperature, higher air initial temperature, higher air initial velocity, smaller angle between slot and axis of the spinneret, smaller width of the die head, and larger width of the slot can all produce finer fibers. At the same time, the air jet flow field model of the dual slot sharp inset die of polypropylene polymer nonwovens fabrics in melt blowing process was also established. The air jet flow field model was solved by using the finite difference method. The computational simulation results of the distributions of the z‐components of air temperature and air velocity along the spinline during melt blowing process are in accordance with the experimental data. The air drawing model of melt blowing process was simulated by means of the numerical simulation results of the air jet flow field. The predicted fiber diameter agree with the experimental data. The effects of the air initial velocity and air initial temperature on the fiber diameter were studied and discussed. The results demonstrate that a higher air initial velocity and a higher air initial temperature are beneficial to the air drawing of the polymer melt and thus to reduced fiber diameter. The results show the great potential of this research for computer assisted design in melt blowing nonwoven process and technology. POLYM. ENG. SCI., 57:417–423, 2017. © 2016 Society of Plastics Engineers     

Biodegradability of nonwoven flax fiber reinforced polylactic acid biocomposites

Biocomposites of flax reinforced polylactic acid (PLA) were made using a new technique incorporating an air‐laying nonwoven process. PLA and flax fibers were mixed and converted to the webs in the air‐laying process. Prepregs were then made from the fiber webs by thermal consolidation. The prepregs were finally converted to composites by compression molding. This study was investigated the biodegradability and water absorption properties of the composites. The composites were incubated in compost under controlled conditions. The percentage weight loss and the reduction in mechanical properties of PLA and biocomposites were determined at different time intervals. It was found that with increasing flax content, the mechanical properties of the biocomposites decreased more during the burial trial. The increasing of flax content led to the acceleration of weight loss due to preferential degradation of flax. This was further confirmed by the surface morphology of the biodegraded composites from scanning electron microscope image analysis. Morphological observations indicated severe disruption of biocomposites structure between 60 and 120 days of incubation. POLYM. COMPOS., 35:2094–2102, 2014. © 2014 Society of Plastics Engineers     

Controlling micro‐ and nanofibrillar morphology of polymer blends in low‐speed melt spinning process. Part III: Fibrillation mechanism of PLA/PVA blends along the spinline

The effects of spinning conditions on the fibrillation process of poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA) polymer blends in an elongational flow within the fiber formation zone are systematically and thoroughly investigated. By considering the relationship between the changes in filament parameters with the focus on the maximum axial strain rate (ASR) and tensile stress at maximum ASR and the morphological evolution of the dispersed PLA phase along the spinline, the fibrillation process from rod‐like to nanofibrillar structures of the dispersed PLA phase in a binary blend with PVA matrix is elucidated. The final morphology of the dispersed PLA phase in PLA/PVA blends is controlled by the changes in the spinning conditions. The lengths and diameters of the PLA fibrils are caused not only by the deformation of their initial sizes but also by the combination of the deformation, coalescence, and break‐up process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44259.     

Influence of PANI‐complex on the mechanical and electrical properties of carbon fiber reinforced polypropylene composites

The aim of this work was to determine the influence of PANI‐complex on the mechanical and electrical properties of CF‐PP composites. As expected, an increase in tensile strength and modulus of the PP matrix could be achieved with an increasing fiber weight fraction. On the other hand, the PANI‐complex decreased the tensile strength and modulus of the fiber reinforced composites; however, these values remained on a better level than the value of the neat PP. Further, by using a long carbon fiber (LCF) reinforcement instead of short carbon fibers (SCF) the percolation threshold was moved towards a lower fiber weight content. In addition, a synergy effect between PANI‐complex and LCF in the PP‐matrix regarding the electrical properties occurred. In particular, an abrupt decrease in the surface resistivity could be avoided. Also, the surface resistivity of a blend is better when the blend consists of both PANI‐complex and LCF instead of only one of these fillers.     

Compression molding and melt‐spinning of the blends of poly(lactic acid) and poly(butylene succinate‐co‐adipate)

Poly(lactic acid) (PLA) is a biobased polymer made from biomass having high mechanical properties for engineering materials applications. However, PLA has certain limited properties such as its brittleness and low heat distortion temperature. Thus, the aim of this study is to improve toughness of PLA by blending with poly(butylene succinate‐co‐adipate) (PBSA), the biodegradable polymer having high toughness. Polymer blends of PLA and PBSA were prepared using a twin screw extruder. The melt rheology and the thermal property of the blends were examined. Further the blends were fabricated into compression molded parts and melt‐spun fiber and were subjected to tensile and impact tests. When the PBSA content was low, PBSA phase was finely dispersed in the PLA matrix. On the other hand, when the PBSA content was high, this minor phase dispersed as a large droplet. Mechanical properties of the compression molded parts were affected by the dispersion state of PBSA minor component in PLA matrix. Impact strength of the compression molded parts was also improved by the addition of soft PBSA. The improvement was pronounced when the PBSA phase was finely dispersed in PLA matrix. However, the mechanical property of the blend fibers was affected by the postdrawing condition as well as the PBSA content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41856.