基于再生聚乳酸的3D打印可持续生物复合材料外文文献

Recycled poly lactic acid ebased 3D printed sustainable biocomposites a comparative study with injection molding Q10 Q9E O Cisneros L opez a A K Pala A U Rodrigueza F Wua M Misraa b D F Mielewskic A Kiziltas c A K Mohantya b aBioproducts Discovery and Development Centre Department of Plant Agriculture Crop Science Building University of Guelph 50 Stone Road East Guelph Ontario Canada bSchool of Engineering Thornbrough Building University of Guelph 50 Stone Road East Guelph Ontario Canada cResearch and Innovation Center Ford Motor Company Dearborn MI 48124 USA a r t i c l e i n f o Article history Received 8 May 2019 Received in revised form 22 October 2019 Accepted 7 November 2019 Available online xxx Keywords Poly lactic acid Microcrystalline cellulose Recycling 3D printing Injection molding Chain extender Q2 a b s t r a c t With the objective of giving a new economic life to postindustrial waste poly lactic acid PLA bio composites based on recycled PLA were manufactured using conventional melt blending and the strands produced were successfully used for three dimensional 3D printing of ASTM samples by Q1 means of the fused deposition molding FDM method This article further discusses the processing advantages and challenges associated with void formation anisotropic behavior and the quality of the 3D printed 3DP samples in comparison with injection molded IM counterparts The blends were manufactured con taining 30 wt of recycled PLA in a matrix of virgin PLA Similarly blends were also prepared with addition of an epoxy based chain extender CE and as well as with the CE and a reinforcing phase of microcrystalline cellulose MCC One of the limitations of recycled PLA in FDM based 3D printing is its high melt fl ow due to the reduced molecular weight after recycling which results in excessive material fl ow during extrusion and hence limits its application in FDM based 3D printing Consequently the main effect of the CE Joncryl was to control the Melt Flow Index MFI of the biocomposites containing the recycled PLA The addition of CE also resulted in improvement of the impact strength of 3DP samples In general the CE in combination with the natural fi bers MCC allowed the incorporation of postindustrial PLA Data suggest that more recycled PLA may be incorporated by using this blend combination In general owing to the void formation 3DP samples presented lower values of density lightweight and mechanical properties as compared with IM samples However the tensile strength modulus and Izod impact strength of 3DP biocomposites were increased by up to 88 127 and 11 respectively by the addition of 5 wt MCC as compared with 3DP samples based on postindustrial PLA without additives 2019 Elsevier Ltd All rights reserved 1 Introduction The production of complex geometries as available in advanced computer aided design software has emerged as a research area in three dimensional 3D printing The limitations in 3D printability and mechanical properties of virgin polymers encourage the sci entifi c community to continue developing high performance 3D printable polymer composites that impart various advantages such as cost effectiveness high precision reduction in polymer waste minimal chemical usage and customized complex geometries Such developed materials can be used in many industries such as housing construction packaging biomedical tissue engineering automotive electronics and aerospace engineering where there is demand 1 2 The 3D manufacture of objects is a form of layer by layer additive manufacturing AM by various techniques including polymer jetting 3 There are three main factors that characterize objects printed by these techniques which are as follows densifi cation printing resolution and the capability of using multiple materials 1 2 One of the most common rapid prototyping tech niques in 3D printing is fused deposition modeling FDM which has the main advantage of multiple usage of materials As compared with stereolithography and selective laser sintering the density and resolution are not as good because FDM adds more Corresponding author Corresponding author E mail addresses mmisra uoguelph ca M Misra mohanty uoguelph ca A K Mohanty Contents lists available at ScienceDirect Materials Today Sustainability journal homepage materials today sustainability https doi org 10 1016 j mtsust 2019 100027 2589 2347 2019 Elsevier Ltd All rights reserved Materials Today Sustainability xxx xxxx xxx 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 MTSUST100027 proof 9 December 2019 1 12 Please cite this article as E O Cisneros L opez et al Recycled poly lactic acid ebased 3D printed sustainable biocomposites a comparative study with injection molding Materials Today Sustainability https doi org 10 1016 j mtsust 2019 100027 points of contact failure by adding lines during the printing of the layers FDM based 3D printing is used mainly with plastic strands or pellets commonly poly lactic acid PLA polycarbonate and acrylonitrile butadiene styrene ABS 4 The production of actual parts using 3D printing has accelerated in the automotive and biomedical industries The motivation behind FDM based 3D printing is to promote sustainability by exploring new materials for sustainable composite manufacturing 2 reduction in material waste negligible tooling cost and shorter supply chain 5 The awareness of polymer recycling and material utilization with less processing steps increases the demand for 3D printers and furthermore analysis of the properties of the printed materials can be used to optimize operating conditions which helps to increase the use of sustainable materials on an industrial scale 6 and also allows the use of waste from biomass feedstock 7 With regard to this Zeidler et al 8 used renewable biobased fi lers such as wood fl our rice husk and miscanthus with a binder to fabricate high biomasseloaded biodegradable parts by a 3D print ing technique known as powder bed however the use of postindustrial biopolymers represents an area of opportunity Anderson 21 compared me chanical properties of 3DP parts of virgin PLAwith those of recycled PLA produced by re extrusion of virgin PLA and concluded that the tensile strength and hardness of recycled PLAwas reduced upto 11 and 2 respectively However shear strength showed an in crease of up to 6 8 without affecting the tensile modulus of elas ticity which encourages further research on use of postindustrial biopolymers for 3D printing of polymer composites In this work a comparison of thermomechanical properties and surface morphology of 3DP and injection molded IM specimens has been made for biocomposites based on recycled postindustrial PLA from coffee pod waste Joncryl ADR 4368C was added to PLA recycled PLA composite as an epoxy based chain extender CE to improve its processability and mechanical performance Further more the addition of microcrystalline cellulose MCC as a rein forcing agent to the PLA recycled PLA biocomposites imparted thermal stability The overall target of this research work is to use 3D printing technology to promote sustainability and recycling of bioplastic waste by the addition of recycled PLA to virgin PLA without affecting the thermomechanical properties The compari son established among the properties of IM and 3DP specimens will encourage the use of sustainable polymer composites for 3D printing 2 Experimental section 2 1 Materials The matrix was produced by using a blend of postindustrial PLA waste and virgin PLA Postindustrial PLA waste was the leftover material after cutting circular fi lters for the manufacture of com postable coffee pods PurPod100 Club Coffee Canada The pristine PLA used for the blend was fi lm grade PLA 4043D MFI 6 g 10 min 210 C 2 16 kg melting temperature Tm 160 C supplied from Nature Works USA The processing window for this PLA is be tween 180 and 210 C MCC in powder form with an average par ticle size of 74mm 200 mesh a purity of 97 a moisture content of 5 and a bulk density of 0 6 g cm3was supplied by MP Bio medicals LLC USA MCC and Joncryl ADR 4368C BASF Ger many were used as reinforcing fi ller and as epoxy based CE respectively The thermal stability of PLA recycled PLA rPLA and MCC was measured by thermal gravimetric analysis TGA using a TA Q500 Instrument The experiments were performed from 30 to E O Cisneros L opez et al Materials Today Sustainability xxx xxxx xxx2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 MTSUST100027 proof 9 December 2019 2 12 Please cite this article as E O Cisneros L opez et al Recycled poly lactic acid ebased 3D printed sustainable biocomposites a comparative study with injection molding Materials Today Sustainability https doi org 10 1016 j mtsust 2019 100027 800 C at 10 C min under an inert atmosphere N2 For all the samples the mass weight was as near as possible to 10 mg 2 2 Methods The fabricated strands of three formulations were designated as 70 PLA 30 rRPLA PLA RPLA 70 PLA 30 RPLA 0 5phr epoxyebased CE PLA RPLA 0 5J and 95 70 PLA 30 RPLA 5 MCC 0 5 phr epoxy based CE PLA RPLA 5MCC 0 5J Table 1 sum marizes these blends The loadingof MCC in the blend was optimized based on the MFI results as shown in Table S1 available in the supporting infor mation However the Joncryl in the blend was fi xed based on prior research performed on the PLA based composites by other researchers in our group 22 Fig 1 shows the processing meth odology for recycled PLA The as received postindustrial PLA mesh Fig 1 a was extruded in a twin screw Leistritz extruder Leistritz Advance Technologies Corporation USA with L D length diam eter ratio and screw diameter of 48 1 and 27 mm respectively Fig 1 b After passing through a water bath the extruded recycled PLA strands Fig 1 c were pelletized as shown in Fig 1 d Q3 Before blend processing both types of PLA and MCC were placed at 75 C in a drying oven till trapped moisture content reached less than 0 5 The materials were manually mixed in the ratios as shown in Table 1 and the blends were processed by twin screw extrusion The main feeder of the extruder was used at a rate of 5 kg h The processing temperature profi le was set from 165 C to 180 C 165 170 170 175 180 180 180 180 180 175 170 165 from zone 1 to zone 12 with a screw speed of 100 rpm The particular confi gura tion of the available machine has a die with 3 openings each of 3 mm diameter After coming from the die the strands passed through a water bath and the excess water removed by using an air drier Scheer model WA04 US The extrusion parameters were fi xed to ensure the production of fi laments with a regular average diameter of 2 2 mm The dimensional stability of the strands is a key factor to obtain a good qualityeprinted piece The surface of the prepared fi laments was smooth The strands were collected and kept for further drying for 24 h in an oven at 70 C before 3D printing The MFI of all the samples was evaluated in a Melt Flow Indexer Qualitest MFI 2000A in accordance with ASTM D1230 at 190 C under a load of 2 16 kg The tests were replicated three times per sample and the averagevalue and standard deviation tabulated Table S1 2 2 1 Injection molding Half of the extruded fi laments were pelletized using a pelletizer Bullet 64 US before injection molding After pelletization the pellets were kept at room temperature before injection molding using a single screw minijector MPM model 55 US operated at 180 C all zones with pressure settings of 1000 900 and 400 psi to form tensile fl exural and impact test pieces fi ve specimens of each type for each formulation The Izod impact samples were notched immediatelyafter molding Before characterization the IM pieces were conditioned during 48 h at 25 C and 50 RH 2 2 2 3D printing Half of the extruded strands 2 2 mm diameter of each formulation as shown in Table 1 were used for 3D printing by means of fused fi lament fabrication or FDM of the ASTM tensile type IV fl exural and impact test pieces using a LulzBot TAZ 6 The 3D printer was operated at a nozzle temperature of 200 C with in built plate temperature print speed layer height infi ll density and raster angle of 60 C 60 mm s 0 38 mm 100 and 45 45 respectively Five specimens of each type of test piece and each formulation were printed This particular model of printer uses a movable bed in the XeY direction whereas the head or printing device moves in the X Y and Z directions Before characterization the 3DP specimens were conditioned during 48 h at 25 C and 50 RH 2 3 Characterization 2 3 1 Surface morphology Samples of all the formulations were analyzed on their cross section after impact testing described in the following para graph The images were collected using a scanning electron mi croscope SEM Phenom ProX The Netherlands operated at 10 kV A gold coating was applied on the surface of the samples before analysis to avoid charging The images were recorded in the magnifi cation range of 250X to 2000X at different locations on the surface 2 3 2 Density The density of all the fabricated specimens was measured by weighing in airand water using an electric densimeter Alfa Mirage MD 300S The tests were replicated using fi ve specimens of each formulation 2 3 3 Mechanical properties The mechanical properties tensile and fl exural of the speci mens prepared by both the techniques were analyzed using a universal test machine Instron 3382 at room temperature The tensile tests were performed as per ASTM D638 The type IV specimens gauge length 25 mm were analyzed at 5 mm min The fl exural test of the specimens was conducted in accordance with ASTM D790 at 14 mm min and with a span to depth ratio of 16 1 52 mm The Izod Impact testing of notched samples was per formed based on ASTM D256 using an impact test instrument TMI Testing Machines Inc US The tests were performed using a 5 ft lb pendulum on fi ve specimens of each material The averagevalues together with their standard deviations were recorded The mechanical properties and density results were analyzedusingamultifactorstatisticalanalysis ofvariance ANOVA in MATLAB software To distinguish signifi cant differ ences among homogeneous subsets a Tukey s honest signifi cance test was conducted using a confi dence interval of 95 In the fi gures related to mechanical properties and density different letters a b c indicate signifi cantly different homogeneous subsets p 05 2 3 4 Differential scanning calorimetry The effect of reinforcing phase and CE on the thermal behavior particularly for glass transition Tg cold crystallization Tc and Tmof the waste PLA based matrix was measured in a differential scanning calorimeter TA Q200 under inert atmospheric condi tions The fi rst heating cycle was performed from 0 to 200 C at 10 C min followed by holding isothermallyat 200 C for 2 min The sample was then brought to 0 C at the same scan rate followed by heating from 0 to 200 C again at 10 C min The data from the fi rst heating cycle are presented here to analyze the effect of processing Table 1 Blends and acronyms used in this study BlendAcronyms 70 PLA34043D 30 RPLAPLA RPLA 70 PLA34043D 30 RPLA 0 5 phr chain extenderPLA RPLA 0 5J 95 70 PLA34043D 30 RPLA 5 MCC 0 5 phr chain extender PLA RPLA 5MCC 0 5J PLA poly lactic acid RPLA recycled PLA MCC microcrystalline cellulose E O Cisneros L opez et al Materials Today Sustainability xxx xxxx xxx3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 MTSUST100027 proof 9 December 2019 3 12 Please cite this article as E O Cisneros L opez et al Recycled poly lactic acid ebased 3D printed sustainable biocomposites a comparative study with injection molding Materials Today Sustainability https doi org 10 1016 j mtsust 2019 100027 on thermal properties The proportion of crystalline PLA Xc was estimated using Eq 1 23 Xc DHm DHcc DHref 100 w 1 whereDHm DHccrepresents the difference in enthalpy at melting and enthalpy at Tc DHrefis related to enthalpy at melting of fully crystalline PLA 93 J g 23 and w is PLA weight fraction in each formulation 2 3 5 Heat defl ection temperature and dynamic mechanical analysis The heat defl ection temperature HDT of fabricated specimens was measured using a dynamic mechanical analyzer TA Q800 in static mode scanning from 25 C to 120 C at 2 C min under 3 point bending deformation applying a stress of 0 455 MPa to obtain the temperature for a defl ection of 250mm The HDT test for each formulation was conducted three times to check repeatability The trends of the observed values for storage modulus E0 and damping factor tand from dynamic mechanical analysis DMA testing of PLA RPLA blend matrix and its biocomposites were analyzed after the addition of MCC reinforcing phase and Joncryl CE by using a dynamic mechanical analyzer TA Q800 with temperatures between 30 C and 120 C at 3 C min with an oscillation amplitude of 15 mm and a frequency of 1 Hz Two rep licates of each sample were tested 2 3 6 Rheology The dynamic rheological properties were