Khảo sát khả năng trộn hợp của polyolefine với pvc

ĐẠI HỌC QUỐC GIA THÀNH PHỐ HỒ CHÍ MINH TRƯỜNG ĐẠI HỌC BÁCH KHOA -o0o - NGUYEÃN BÁ HOÀNG HUY KHẢO SÁT KHẢ NĂNG TRỘN HP CỦA POLYOLEFINE VỚI PVC Chun ngành : Vật liệu cao phân tử tổ hợp LUẬN VĂN THẠC SĨ Tp HCM, Tháng 6/2008 CÔNG TRÌNH ĐƯC HOÀN THÀNH TẠI TRƯỜNG ĐẠI HỌC BÁCH KHOA ĐẠI HỌC QUỐC GIA TP.HCM Cán hướng dẫn khoa học: T.S VÕ HỮU THẢO Cán chấm nhận xét 1: T.S HUỲNH BẠCH RĂNG Cán chấm nhận xét 2: T.S NGUYỄN ĐẮC THÀNH Luận văn bảo vệ HỘI ĐỒNG CHẤM BẢO VỆ LUẬN VĂN THẠC SĨ, TRƯỜNG ĐẠI HỌC BÁCH KHOA, ngày 15 tháng năm 2008 ĐẠI HỌC QUỐC GIA TP HCM TRƯỜNG ĐẠI HỌC BÁCH KHOA CỘNG HOÀ XÃ HỘI CHỦ NGHIÃ VIỆT NAM Độc Lập - Tự Do - Hạnh Phúc -oOo Tp HCM, ngày 30 tháng năm 2008 NHIỆM VỤ LUẬN VĂN THẠC SĨ Họ tên học viên: NGUYỄN BÁ HỒNG HUY Giới tính : Nam Ngày, tháng, năm sinh : 17/09/1982 Nơi sinh : Long An Chuyên ngành : Vật liệu Cao phân tử tổ hợp Khoá (Năm trúng tuyển) : K2005 1- TÊN ĐỀ TÀI: KHẢO SÁT KHẢ NĂNG TRỘN HỢP CỦA POLYOLEFINE VỚI PVC 2- NHIỆM VỤ LUẬN VĂN: Là khảo sát khả trộn hợp Polyolefine ( PE,PP) với PVC nhằm xem xét tính chất chung hỗn hợp sau trộn lẫn Sử dụng chất tương hợp Chlorinated Polyethylene (CPE), Polypropylene graft Maleic Anhydric (PP-g-MA), Ethylene propylene dien monomer (EPDM) cho trình trộn hợp Blend PE/PVC, PP/PVC, PP/PE Khảo sát hàm lượng chất tương hợp, thời gian trộn, nhiệt độ trộn ảnh hưởng đến tính chất lí hỗn hợp Khảo sát tính chất hỗn hợp Blend sau thay đổi hàm lượng thành phần 3- NGÀY GIAO NHIỆM VỤ : 20/6/2007 4- NGÀY HOÀN THÀNH NHIỆM VỤ : 30/6/2008 5- HỌ VÀ TÊN CÁN BỘ HƯỚNG DẪN (Ghi đầy đủ học hàm, học vị ): TS VÕ HỮU THẢO Nội dung đề cương Luận văn thạc sĩ Hội Đồng Chuyên Ngành thông qua CÁN BỘ HƯỚNG DẪN (Họ tên chữ ký) CHỦ NHIỆM BỘ MÔN QUẢN LÝ CHUYÊN NGÀNH (Họ tên chữ ký) LỜI CẢM ƠN Trước tiên, xin gửi lời cảm ơn sâu sắc đến thầy TS.Võ Hữu Thảo tận tình giúp đỡ hướng dẫn thực đề tài Tôi xin chân thành cảm ơn thầy cô Trung tâm Polymer thầy cô khoa Công Nghệ Vật Liệu – ĐH Bách Khoa TPHCM tạo điều kiện cho truyền đạt kinh nghiệm q báu cho để hoàn thành luận văn Cảm ơn anh phòng thí nghiệm trọng điểm quốc gia – ĐH Bách Khoa TPHCM giúp đỡ cho nhiệt tình Cảm ơn Giám đốc đồng nghiệp giúp đỡ nhiều để thực tốt luận văn Cảm ơn ba mẹ động viên dìu dắt suốt trình học tập, động lực để vươn lên sống lúc bên cạnh vượt qua khó khăn Cảm ơn tất người bạn, anh em tốt giúp đỡ nhiều học tập sống Xin chân thành cảm ơn Học viên Nguyễn Bá Hoàng Huy LỜI MỞ ĐẦU Việc trộn loại nhựa lại với tạo loại nhựa có tính cân tính chất hóa học vật lí Đây phương pháp đơn giản mà mang lại hiệu cao Quá trình không cần thiết bị phức tạp áp dụng qui mô nhỏ đáp ứng yêu cầu cụ thể tính lí hóa Tuy nhiên polymer thành phần có xu hướng không trộn lẫn tốt với không phát huy hiệu Ngành công nghiệp nhựa tìm kiếm cách làm giảm chi phí Trong số trường hợp, số loại nhựa mắc tiền có tính tốt mức cần thiết trộn với loại nhựa rẻ tiền hay chất độn để giảm giá thành cần chất tương hợp hay chất tạo liên kết để đảm bảo tính lí mà hỗn hợp hình thành có chi phí thấp Ứng dụng linh động việc thiết kế sản phẩm Từ loại nhựa nguyên sinh tạo nhiều loại nhựa đáp ứng nhu cầu đa dạng Hiệu kinh tế chi phí thấp nhiều so với việc phát triển loại nguyên liệu từ nhựa nguyên sinh Có thể kết hợp nhiều loại nhựa có giá thấp vào loại nhựa có giá cao chất độn để giảm giá thành Ngoài trộn loại nhựa nhẹ vào loại nhựa nặng để giảm tỷ trọng, giảm khối lượng sản phẩm thể tích không giảm để giảm chi phí nguyên liệu Tuy nhiên, có nhiều trở ngại cho phát triển dòng sản phẩm nguyên liệu nhựa áp dụng cho công nghệ Vì cấu trúc phân tử polymer phức tạp đa dạng nên việc trộn lẫn chúng để tạo sản phẩm nhiều khó khăn Việc nghiên cứu vật liệu nhiều mẻ Trộn nguyên liệu đòi hỏi phải có phụ gia Các phụ gia, việc giúp cho loại nhựa tương thích có tác dụng hay tương tác với thành phần khác hỗn hợp nhựa thành phần Một số có tác dụng theo hướng tích cực i có tác dụng tiêu cực làm giảm khả ứng dụng chúng Tuy nhiên việc chọn lựa áp dụng chế độ gia công phù hợp khắc phục nhược điểm chúng Cùng với nhu cầu thực tế xã hội, lựa chọn loại nhựa phổ biến PE (polyethylene), PP (polypropylene) PVC (polyvinylcloride) để khảo sát khả trộn hợp cặp thông qua chất tương hợp để chúng kết hợp với Giới hạn luận văn này, khảo sát PE trộn hợp với PVC sử dụng chất tương hợp CPE (cloridepolyethylene), khảo sát PP trộn hợp với PVC sử dụng chất tương hợp PP-g-MA (polypropylene graft Maleic Anhydride), khảo sát khả tương hợp PP PE sử dụng chất tương hợp EPDM Để định hướng cho nghiên cứu sau sâu hơn, để hoàn thiện hỗn hợp sau trộn hợp ii TÓM TẮT Sử dụng chất tương hợp Chlorinated polyethylene (CPE), Polypropylene graft Maleic anhydric (PP-g-MA), Ethylene propylene diene terpolymer rubber (EPDM) cho trình trộn hợp blend PE/PVC ; PP/PVC ; PE/PP Khảo sát hàm lượng chất tương hợp, thời gian trộn, nhiệt độ trộn ảnh hưởng đến tính chất lí hỗn hợp, Khảo sát tính chất hỗn hợp thay đổi hàm lượng thành phần Quá trình thí nghiệm thực máy trộn Brabender Đánh giá trình trộn hợp thực thông qua phương pháp đo tính chất lí ABSTRACT Chlorinated polyethylene (CPE) is used as a modifier for blends of PVC/ PE Polypropylene graft Maleic anhydric (PP-g-MA) is used as a modifier for blends of PVC/ PP.Ethylene propylene diene monomer (EPDM) is used as a modifier for blends of PP/ PE They have been found to be particularly effective in upgrading the mechanical and physical properties of blends Besides, how it affects to its compatibilization action, constitutes an important point to be analyzed Several studies examine the effect of the molecular architecture, in general, on the efficiency of the copolymers Compatibleness qualitive contents survey, Time and temperature compound affect blends Process experiment is realized on Brabender machine iii MỤC LỤC Trang NHIỆM VỤ LUẬN VĂN LỜI CẢM ƠN Lời mở đầu………………………………………………………………………………………………………………………………… i Tóm tắt luận văn…………………………………………………………………………………………………………………… iii Mục lục……………………………………………………………………………………………………………… iv Kí hiệu………………………………………………………………………………………………………………………………………….viii Danh mục hình ……………………………………………………………………………………………………………………… ….x Danh mục bảng biểu………………………………………………………………………………………………………………xiv PHẦN 1: TỔNG QUAN CHƯƠNG 1: POLYVINYLCLORIDE Polyvinylchloride (PVC) ………………………………………………………………………….………………….…1 1.1 Phân huỷ ổn định PVC ………………………………………………………………….………………… …1 1.1.1 Phân hủy PVC……………………………………………………………………………….……………………………….1 1.1.1.1 Đặc điểm………………………………………………………………………………….…….………………1 1.1.1.2 Cơ chế phân hủy…………………………………………………………………………………….……2 1.2 Phụ gia cho PVC …………………………………………………………………………………………………………… 1.2.1 Chất ổn định (PVC Stabilizers) ……………………………………………………………………4 1.2.2 Chất hóa dẻo (Plasticizers)……………………………………………………………………………9 1.2.3 Chất bôi trơn (Lubricants)………………………… ………………………………………………12 1.2.4 Màu sắc (Colorants)………………………………………………………………………… ….…….13 1.2.5 Chất ổn định quang (Light stabilizers)……………………………………………………17 1.2.6 Độn (Fillers) ………………………………………………………………………….……………………….18 iv CHƯƠNG 2: POLYETHYLENE 2.1 PolyEthylene 19 2.1.1 Khái niệm 19 2.1.2 Nguyeân liệu để sản xuất PE .19 2.1.3 Sản xuất PE 19 2.1.4 Cấu tạo tính chất 21 2.1.5 Phaân loaïi 26 2.1.6 Ứng dụng 27 CHƯƠNG 3: POLYPROPYLENE 3.1 Công thức cấu tạo…………………………………………………………………………………………………………….29 3.2 Cấu trúc PP…………………………………………………………………………….………………………………….29 3.3 Phân loại PP…………………………………………………………….………………………………………………………….29 3.3.1 Homopolymer PP (HPP)………………………………………………………………………………….29 3.3.2 PP Impact copolymer (HPP)………………………………………………………………………….30 3.3.3 PP random copolymer (PP-R)……………………………………………………………………….30 3.4 Tính chất……………………………………………………………………………………………………………………………….31 3.4.1 Tính chất lý nhiệt………………………………………………………………………………………………31 3.4.2 Độ bền hoá học…………………………………………………………………………………………………31 3.4.3 Tính chất học…………………………………………………………………………………………………33 3.5 Tính chất PP-R…………………………………………………………………………………………………………36 3.6 Sản xuất polypropylene…………………………………………………………… ………………………………….36 CHƯƠNG 4: BLEND HỖN HP 4.1 Giới thiệu…………………………………………………………………………….……………………………………………….40 4.1.1 Polymer blend không trộn lẫn……………………………………………………………………………… 40 4.1.1.1Hình thái học polymer blend không trộn lẫn……………………………… 41 4.1.1.2Tính chất hỗn hợp polymer không trộn lẫn……………………………….….42 v 4.1.2 Polymer trộn lẫn……………………………………………………………………………………………………………45 4.1.3 Chất tương thích nhựa – trợ thủ đắc lực để trộn loại nhựa với nhau…………………………………………………………………………………………………………………………….45 4.2 Giới thiệu số hỗn hợp…………………………………………………………………………………………….50 4.3 Mục đích ứng dụng polymer blend ………………………………………………………….50 4.3.1 Mục đích…………………………………………………………………………………………………………………………….50 4.3.2 Ứng dụng……………………………………………………………………………………………………………………………51 4.3.3 Các phương pháp phối trộn polymer blend …………………………………………………………51 4.3.4 Các yếu tố ảnh hưởng lên trình blend ………………………………………………………… 52 PHẦN 2: THỰC NGHIỆM CHƯƠNG 1: NGUYÊN LIỆU 1) Polyethylene (PE)…………………………………………………………………………………………………………… 53 2) Polypropylene (PP)……………………………….……………………………………………………………………………53 3) Polyvinylcloride (PVC)………………………………………………………………….…………………………………54 4) Cloride polyethylene (CPE)………………………………………………………….………………………………54 5) DOP plasticizer……………………………………………………………………………….………………………….…… 55 6) ESO 81 – Epoxidized Soya Bean Oil……………………………………………….……………………….56 7) Chất Ổn Định Xà Phòng Kim Loại……………………………………………………………….………….56 8) Chất Tương Hợp PP-g-MA……………………………………………………………………….……….……… 56 9) EPDM…………………………………………………………………………………………………………………… …………… 57 CHƯƠNG : QUI TRÌNH THỰC NGHIỆM – Mục đích nghiên cứu…………………………………………………………………………………………………….58 – Nội dung nghiên cứu………………………………………………………………………………………… ……… 62 – Phương pháp đánh giá thực nghiệm………………………………………………………………………62 3.1 – Đo độ bền kéo………………………………………………………………………………….…………… 62 vi xd Năng lượng va đập tính: E xo Fx dx h RHEOLOGICAL STUDY OF THE COMPATIBILIZATION OF PVC/PE BLENDS WITH CLORINATED POLYETHYLENE INTRODUCTION Polyethylene and PVC differ in many aspects making them difficult to blend together Large contrasts in polarity, crystallinity and viscosity, together with the presence of microcrystallytes in the molten state, lead to incompatibility During mixing, a domain structure with a low adhesion (1-6) between phases is generated This gives rise to poor mechanical properties which limit the practical use of the blends of two of the most widely utilized polymers, PVC and PE, which are interesting for recycling purposes As in the case of other incompatible polymers, the addition of a third component which “compatibilises” the blend, as it improves its mechanical properties, constitutes a route, which has given good results Notwithstanding recently new compatibilizers, like poly (butadiene-block-(styrene-coacrylonitrile)) (7), and the use of butadiene rubber solid phase dispersant (8), have been proposed, chlorinated polyethylene (CPE) remains as a very suitable choice The work of Schramm and Blanchard (9) was a pioneering contribution for the use of chlorinated polyethylene (CPE) to improve the properties of PVC/PE blends The solid-state procedure developed by these authors to chlorinate polyethylene leads to a multiblock copolymer with polyethylene segments and blocks similar to PVC This is termed usually as a “block” CPE copolymer (bCPE) This type of CPE was employed by several authors (1, 5-6, 10-11) who analyzed the effect of chlorine content on the mechanical properties of PVC/PE blends Instead of block CPE copolymers, random CPEs (rCPE), obtained from PE in solution, have been also employed (6) It is generally accepted that the addition of small amounts of this CPE increases both ductility and tensile strength of PVC/PE blends However, the rheological effects of the incorporation of a compatibilizer to these binary blends is a subject that has not been treated in depth The double role, that is to say particle-size reduction and improvement of interfacial adhesion, assigned in general to compatibilizers, leads to assume that they can cause a viscosity increase Recent examples of this enlargement are observed in polyethylene/polystyrene blends compatibilized by non-reactive styrene-ethylene block copolymers (12) On the other side of the balance, we remark that the addition of a certain amount of a multiblock copolymer compatibilizer to 50/50 wt.% liquid crystalline polymer/ polysulfone blend does not alter the melt viscosity (13) PROBLEM Chlorinated polyethylene (CPE) is used as a modifier for blends of waste plastics It has been found to be particularly effective in upgrading the mechanical properties of polyethylene/poly (vinyl chloride) blends However, the rheological effects, in particular the fundamental mechanism of action, of adding CPE to the aforementioned blend have not been studied in depth yet Besides, the distribution of chlorine along the chain of CPE and how it affects to its compatibilization action, constitutes an important point to be analyzed Several studies examine the effect of the molecular architecture, in general, on the efficiency of the copolymers, but no consistent studies about this blend (PVC/PE) and this compatibilizer (CPE) in particular have been found So, the objective of the present work is to use different rheological techniques to elucidate the role played by block and random CPE-s in the rheology of practical devoted HDPE/PVC/CPE systems Small-amplitude oscillatory measurements, creep and recoil experiments, capillary extrusion flow and shrinkage measurements, have been performed to elucidate the effect of block and random chlorinated polyethylene (CPE) on the rheological properties of ternary high density polyethylene (HDPE)/poly (vinyl chloride) (PVC)/CPE system METHODS Materials The materials used in this study were poly(vinyl chloride), PVC (Mw=8.3 104, Mw/Mn=2.39), supplied by Aiscondel S A., Spain, (Etinox 650), high-density polyethylene, HDPE (Mw=1.7 105, Mw/Mn=7.70), supplied by Repsol S A., Spain, (PE6006L) and two chlorinated polyethylenes with 40% Cl content: a block chlorinated polyethylene, bCPE, supplied by Dow Chemical Products (Tyrin BH9000) and a random chlorinated polyethylene, rCPE, supplied by Aldrich The complex viscosities obtained in oscillatory experiments and the flow curves (apparent shear stress and shear rate values) obtained in capilary extrusion of the materials involved in the blends are presented in Figure 10 T=160ºC PVC η* (Pa.s) 10 10 b CPE r CPE HDPE 10 10 10 -2 10 -1 ω (Hz) 10 10 a) T=160ºC σap(Pa) 10 PVC b CPE 10 r CPE HDPE 10 10 10 10 10 10 γ ap (s -1) b) FIG The complex viscosity as a function of frequency (1a) obtained in oscillatory flow and the flow curves (apparent values) obtained in capilary extrusion (1b) of pure materials involved in the blends The arrow in Fig.1b marks the “slip-stick” phenomenon (double value of shear stress) in HDPE sample Compounding HDPE/PVC with a proportion in weight 50/50 has been used as the basic blend in this study In order to elucidate the effect of low amounts of CPE (block or random) on its behavior, different amounts of CPE (block or random) have been added to the basic blend (5 and 10 phr, parts per hundred of resin based on the total amount of the basic blend) obtaining ternary blends HDPE/PVC/bCPE and HDPE/PVC/rCPE with the aforementioned compositions (50/50/5 and 50/50/10) For the glass transition temperature measurements, blends of HDPE/bCPE, HDPE/rCPE, PVC/bCPE and PVC/rCPE with proportion in weight 50/50 have been used All the blends have been premixed in the form of powder and, then, milled in a counter-rotating Two Roll Mill at 170ºC for Concerning the pure materials, they have been treated in the same way as the blends in order to have the same thermomechanical history Morphology The morphology of the blends was characterized using a Scanning Electron Microscopy (SEM) with an accelerating voltage of 15 Kv The samples were cryogenically fractured under liquid nitrogen and then sputtered with a gold in vacuum The morphology of the sheets obtained directly from the two-roll mill, of the filaments obtained in extrusion rheometry for shrinkage measurements and of the mentioned filaments after shrinkage was observed Dynamic mechanical measurements Dynamic mechanical properties were measured in a Dynamic Mechanical Analyzer DMTA Scans of temperature from –150 to 150°C at a frequency of Hz and a heating rate of 4ºC/min were carried out in bending mode with samples of dimensions of approximately 10x5 mm, and width of 1-2 mm Small amplitude oscillatory experiments Small amplitude oscillatory measurements were carried out in a strain controlled viscoelastometer in the temperature range 150-180ºC and frequency range 0.01-15 Hz operating in the oscillatory shear mode with parallel plate geometry (diameter 25 mm) The strain applied was 1%, which was verified to be in the linear viscoelastic region with a previous strain sweep No degradation was observed The reproducibility was checked by repeating the measurements at least two times: the repeatability was within 3% The test specimens with the appropriate geometry were obtained in a compression-molding machine, being preheated at 170ºC for and then pressed with a pressure of 30 MPa for Creep and recovery Creep and recovery measurements were performed in a stress controlled viscoelastometer at T=180ºC with parallel plate geometry (diameter 20 mm) Creep measurements were performed applying σ=2000 Pa, 3000 Pa, 4000 Pa and 5000 Pa The behavior was not linear and the obtained steady-state viscosity displayed a shearthinning effect Samples were allowed to relax up to a constant value of compliance in the recovery measurements No degradation was observed The reproducibility was checked by repeating the measurements at least two times: the repeatability was within 3% Test specimens were obtained by compression-molding, being preheated at 170∫C for and then pressed with a pressure of 30 MPa for Extrusion rheometry Extrusion rheometry measurements were carried out in a capillary rheometer using three capillary tungsten dies of mm diameter and length to diameter ratios (L/D) of 10, 20 and 30, in order to allow us to obtain the so-called Bagley plots A reservoir for a 9.5 mm diameter piston and a flat entrance angle (180º) were used The flow curves were obtained in the temperature range 150-180ºC and shear rate 7.22-3610 s-1 The shear stress and shear rate were corrected with the habitual Bagley and Rabinowitsch corrections respectively (14) The reproducibility was checked by repeating the measurements at least two times: the repeatability was within 3% Shrinkage measurements Filaments for both, HDPE and PVC pure polymers and their blends, with average values of Lo=10 cm and Ro=1 mm, were prepared by extrusion in the capillary rheometer at a temperature of T=160ºC and a shear rate of γ 21 =72.2 s-1 Drawdown by gravity, which could introduce a non-desirable orientation in the samples, was avoided by collecting carefully the extrudates with a tray The filaments were placed in a silicone oil bath at a temperature of T=180ºC and allowed to shrink: the length of the filament, L(t) was measured optically at various times up to 1200 s No degradation was observed The reproducibility was checked by repeating the measurements at least two times: the repeatability was within 3% RESULTS AND DISCUSSION Basic Mechanical and Morphological Characterization The effect of the addition of CPE on the mechanical properties of 50/50 wt HDPE/PVC blend is very noticeable in our case: both, block and random, CPE copolymers show similar capacity to improve the elongation at break (15) This result has been explained considering, as a general argument, that CPE addition increases adhesion via interactions with the blend components (10) However, although the effect of CPE on PE/PVC blends is evident in mechanical tests like stress-strain curves, dynamic mechanical measurements not always are able to reflect clearly the effect of the addition of CPE on this system Comparing PVC/PE and PVC/PE/CPE systems, drifts of the tanδ peak of polyethylene of approximately 20 degrees (while the Tg of PVC does not move) have been reported in the literature (6, 16) But in our case the spectra are very similar, with no alteration of tanδ peaks of PVC and HDPE respectively The only possible symptom of morphological changes is an increase in damping between the glass transition peaks, when small amounts of block or random CPE are added to our HDPE/PVC blend On the other hand, a certain interaction between CPE and HDPE can be deduced from the fact that tanδ peak of both, block and random CPE shifts from 8°C to 0°C and from 25°C to 18°C, respectively, in the presence of HDPE It is also symptomatic that the height of the observed maxima is lower than that which corresponds to CPE phase proportionality On the contrary, no interaction of CPE with PVC can be envisaged, since the position of CPE tanδ peak is not affected by the presence of PVC and the height of this peak reduces proportionally to CPE content a) b) c) FIG SEM microphotographs of blends prepared in a two-roll miller a) 50/50 wt HDPE/PVC b) 50/50/10 wt HDPE/PVC/bCPE c) 50/50/10 wt HDPE/PVC/rCPE SEM results reveal a morphological change when either block CPE or random CPE is added to HDPE/PVC blend As can be seen in Fig.2a, in the case of nonmodified blends the capacity of PVC particle-particle association is strong, which gives rise to aggregates of particles that constitute a network in a co-continous phase However, when CPE is incorporated a much better dispersion is obtained and PVC particles of average size 2µm, microgranules according to PVC nomenclature (17), are observed (Figures 2b-c) Association between PVC particles is therefore considerably reduced by the presence of CPE Melt elasticity measurements: creep recovery and shrinkage Strain recovery after cessation of steady flow at shear stresses of, respectively, 2000, 3000, 4000 and 5000 Pa has been measured to analyze melt elasticity of our binary blend and ternary systems As it could be expected, considering the heterogeneity of the samples, we not obtain master curves when strain recovery, γr, is plotted against the product of steady-state shear rate (prior to recoil experiment) by time However, similar trends in melt elasticity are observed, whatever is the previously applied shear stress Representative results of strain recovery are shown in Figure 3, which also includes steady state compliance, Je0= γ ∞ /σ21, data It is observed that the elastic behavior of both pure polymers differ severely, since HDPE gives rise to much higher recovery values than PVC Binary and ternary systems approach more to PVC strain recovery values than to HDPE values, which can be considered as a symptom of the filler-role played by PVC particles Since PVC particles are not deformed, because PVC is much more viscous than HDPE, recovery is associated to the rubbery deformation of HDPE, which should be reduced when the relative volume of this polymer lessens But the effect is stronger when PVC particles constitute an aggregate network, as can be deduced from the fact that the inclusion of CPE (which reduces particle capacity of association) gives rise to a noticeable increase of strain recovery and steady state compliance HDPE σ = 3000 Pa 1.6 γ rec 1.2 r CPE 0.8 0.4 b CPE PVC 0 10 t (min) FIG Creep recovery after cessation of a flow at σ21=3000 Pa and T=160°C Pure ) 50/50 wt HDPE/PVC and ( ) 50/50/10 wt samples (lines) and blends: ( HDPE/PVC/rCPE The effect of CPE on steady state compliance determined at 3000 Pa is inserted Extrudate swelling during annealing at high temperatures constitutes another procedure to evaluate melt elasticity The shrinkage of an extrudate, obtained in a capillary rheometer and introduced into an oil bath at a temperature above glass transition temperature or melting temperature, can be analyzed using the Hencky measure of strain: ξ r = ln L () L t (1) where L0 is the original length of the extrudate and L(t) is the length at time t The retraction is due to the relaxation of residual stresses (produced by elongational flows at the entrance of the capillary) and to the oil-polymer interfacial tension The stress relaxation gives rise to the elastic strain recovery, ξre, which can be separated from interfacial effect because whereas elastic response is completed rapidly, interfacial tension causes a linear variation of the strain with time (18) The elastic response, ξre, of the sample to orientation produced at the entrance of the capillary is, therefore, determined by subtracting the linear part from the experimentally determined Hencky strain Actually our strain recovery measurements reveal the portion of strain that recovers when an unconstrained extrudate is inmersed in oil, but the other portion of the strain is recovered inmediately at the exit of the die in the form of extrudate swell Measurements of the latter are not accurate enough to allow to observe differences between the binary and ternary blends Only a small number of papers deal with the shrinkage at high temperatures of polymer blend extrudates Reported results on polyethylene based blends are striking Polyethylene/polypropylene, polyethylene/ethylene vinyl acetate copolymer, polyethylene/ polybutene and polyethylene/polystyrene blends at intermediate compositions show enormous shrinkages (ξr close to 3), very much severe than that of pure polymers (19-20) In these systems, dispersed droplets deform in the converging flow at the entrance of the capillary giving rise to minifibres, in a way which was explained by Ablazova, et al (21) Shrinkage then corresponds to the superposition of the recoil of microfibres and the interfacial tension between the microfibres and the surrounding polymer matrix Hencky strain (Eq 1) experimental results of pure PVC, 50/50 wt HDPE/PVC, 50/50/5 wt HDPE/PVC/rCPE and 50/50/10 wt HDPE/PVC/rCPE system samples are presented in Figure A value of ξr=0.91, which represents a considerable length reduction (from 10 to cm) is obtained for HDPE, but PVC extrudates show very small retraction, due probably to the anchoring effect of crystallites, similar to other cases observed in the literature (22) As can be seen in Figure 4, the response of binary and ternary blends resembles to that of PVC, with a rapid stabilization and a much lower recovery than would correspond to the application of a single additive law Neither effect of oil-polymer interfacial tension nor polymer-polymer interfacial tension, is noticed, since the slope of the linear part is zero and consequently the retraction is exclusively due to elastic strain recovery Apparently the presence of PVC particles locks the stress recovery of HDPE, because shrinkage is considerably reduced Moreover Figure shows that shrinkage is larger in the case of HDPE/PVC/CPE ternary systems than in HDPE/PVC binary blends This result reflects that the anchoring or locking effect of PVC is less effective when particles are better dispersed and the interaction of the interface increases, a morphological state which is reached by the addition of either random or block CPE (Figures 2b-c) 1.00 HDPE 0.80 0.60 ξr r CPE b CPE 0.40 0.20 PVC 0.00 10 15 20 t (min) FIG Hencky strains (Equation 4) obtained in shrinkage measurements at 180°C ) 50/50 wt HDPE/PVC, ( ) 50/50/5 wt Pure samples (lines) and blends: ( HDPE/PVC/rCPE and ( ) 50/50/10 wt HDPE/PVC/rCPE Dynamic Viscoelastic Measurements Since superposition method does not hold for PVC based blends, due to their thermorheological complexity (23), in Figure we only show data of storage modulus, G’, and complex viscosity η* at one temperature, T=160°C The interpretation of the results is, however, extensible to the rest of temperatures (150, 170 and 180°C) considered in this work Actually for these temperatures, storage (elastic) modulus, G’, of PVC exceeds the loss modulus, G’’, over all the frequency range, which is a clear symptom of the existence of ordered microdomains or randomly dispersed microcrystallites that have been reported to melt above 200°C (24-26) This “solid-like behavior” (G’>G’’) of PVC, associated to its high elastic modulus, determines the rheological response of the blends T=160ºC 10 * (Pa.s) G' (Pa) 10 10 10 -2 10 -1 10 ω (Hz) 10 FIG Storage modulus and complex viscosity as a function of frequency at 160°C ( ) 50/50 wt HDPE/PVC, ( ) 50/50/10 wt HDPE/PVC/rCPE The results obtained with block CPE superpose with those of random CPE 0.9 T=160ºC tan δ 0.8 0.7 0.6 0.5 10 10 10 G* (Pa) FIG Loss tangent versus complex modulus at 160°C for:( ) 50/50 wt HDPE/PVC, ( ) 50/50/5 wt HDPE/PVC/rCPE, ( ) 50/50/10 wt HDPE/PVC/rCPE Figure shows that the inclusion of small amounts of random CPE on HDPE/PVC blends provokes a slight decrease on storage modulus and complex viscosity, noticeable at low frequencies Similar reductions are observed when block CPE is used The effect of CPE on dynamic viscoelasticity is also noted when tanδ is plotted as a function of complex modulus G*: ternary systems display a higher loss factor (tanδ) than binary blends, as can be seen in Figure Our results differ from those of Park, et al (5) who compare the same ternary and binary blends (except that their CPE is Cl content 36 wt%) observing that complex viscosities of the ternary blends ( with CPE up to 10 wt%) are higher than those of the binary blend They consider that interlayer slip takes place in the incompatible binary blends and that adding a compatibilizer increases the interaction of the interface, thereby increasing the viscosity of the blend Dynamic Mechanical results indicate that no interaction of CPE with PVC can be considered in our case, which leads us to assume that CPE acts rather like a coating agent on PVC particles, decreasing the capacity of PVC particle-particle association As can be seen in Figures 2b and 2c this reduces the ability of PVC particles to form a network, leading to a decline of dynamic viscoelastic functions, in particular G’, at low frequencies It is worthily pointing out the similarity with some coated fillers, which give rise to a decrease in yield stress and viscosity, with respect to non-coated filler systems (27-29) But, on the other hand, we have to admit that compatibilizers provoke particle-size reduction and improvement of interfacial adhesion and can cause, therefore, a viscosity increase There are, hence, two possible opposite effects on the viscosity when CPE is included: a viscosity reduction due to the decrease of the capacity to form particle-particle associations and a viscosity increase caused by particle-size reduction and improvement of interfacial adhesion Viscosity results obtained at low shear rates, in torsion mode, and at high shear rates (extrusion rheometer), seem to confirm the double effect of CPE, as set out below The viscoelastic effects we have shown could also be interpreted as a result of a modification of the HDPE phase by CPE However this hypothesis is discarded since, as can be seen in Figure 1, the complex viscosity of CPE samples is considerably higher than that of HDPE and therefore what we could expect from this hypothesis is an increase in the complex viscosity of HDPE/PVC blend with the inclusion of CPE, the contrary that we observe in Figure Steady flow in torsion Creep experiments in a stress-controlled rheometer allow to determine steadystate viscosity, provided that linear part of strain-time is reached, as is the case of the samples considered in our work It is observed that in the low shear rates range (from 10-3 to 10-1 s-1) obtained in creep experiments, the viscosity decreases when block or random CPE is incorporated to HDPE/PVC blend This confirms dynamic viscoelastic results and can be explained by the reduction of PVC particle-particle association (observed in Fig 2) induced by CPE, which leads to a decrease of the viscosity in a way similar to that observed in the rheology of highly filled polymers (27, 30) or in the deflocculation process of emulsions (31) Steady flow in a extrusion rheometer Extrusion capillary rheometry measurements are relevant from a practical point of view, because they involve non-linear flows in similar conditions to industrial processing It is expected that the information one can get from this type of experiment, which typically include shear rates above 103 s-1, complements that of low shear rates and small amplitude oscillatory flows, especially when we are dealing with complex systems like binary and ternary blends σap(Pa) 10 10 10 10 10 10 10 -1 γ ap (s ) FIG Apparent flow curves (non corrected from ends effects neither from nonnewtonian behavior) obtained in extrusion flow with a L/D=30 capillary at 160°C ( ) ) 50/50 wt HDPE/PVC and ( ) 50/50/10 wt HDPE/PVC/rCPE Double HDPE, ( values of apparent shear stress are observed between 100 and 500 s-1 due to “slipstick” effect η (Pa.s) 10 10 10 γ (s -1) 10 FIG Viscosity function obtained from Bagley’s plots (see experimental) at 160°C Lines are drawn to guide the eye ( ) 50/50 wt HDPE/PVC and ( ) 50/50/10 wt HDPE/PVC/rCPE The shear rate has been corrected from non-newtonian behavior In Figure we present three set of data corresponding, respectively, to pure HDPE, 50/50 wt HDPE/PVC binary blend and 50/50/10 wt HDPE/PVC/rCPE ternary system, at T=160°C as a representative temperature Data of ternary systems which include block CPE, are indistinguishable from those of the ternary system of Figure It is noticed that the inclusion of small amounts of block or random CPE in HDPE/PVC blends increases slightly the viscosity, instead of decreasing it, as it is observed in torsion flow This viscosity growth is much smaller than that which could be envisaged, considering results of Figure 1b, by the hypothesis of a modification of the HDPE phase by CPE Actualy our result is similar to that reported by Francis and George (11), also for CPE modified HDPE/PVC blends To analyze the hypothesis of a possible effect of pressure or length to diameter ratio, L/D, on viscosity results, plots of the applied 10 pressure against L/D at constant shear rate (Bagley’s plots) have been obtained for binary and ternary systems Only shear rates corresponding to smooth extrudates (free of instabilities) are considered In all the cases straight lines with very good correlations (r>0.999) are obtained, which make us to discard pressure effects on viscosity and backpressure effects due to relaxation (32) True wall stresses, independent of L/D and obtained from the slopes of Bagley’s plots, allow us to determine the true viscosity, which is represented in Figure These results confirm the higher viscosity of ternary system in extrusion flow, in contrast to the higher viscosity of binary blend, obtained at low shear rates in torsion flow Considering the aforementioned opposite effects on the viscosity, we can assume that in extrusion flow at high shear rates, the effect of particlesize reduction is more important than the effect of decreasing the capacity of association of the particles promoted by CPE This explanation is supported by SEM microphotographs of the extrudates, shown in Figure According to our morphological results of Figures and the following assumptions can be made: a) In torsion flow, at low shear rates or small amplitude oscillatory measurements, the morphologies of Figure are maintained; that is, PVC aggregate network in binary blend (2a) and dispersed PVC microgranules in ternary systems (2b-c) remain unaltered This explains the dynamic viscoelastic (Figure 5) and creep results, where lower viscosity values are observed for the ternary system b) In capillary extrusion flow, which involves high shear rates and convergent flow at the entrance of the capillary, PVC aggregates of the binary blend are broken (compare Fig.9a with 2a) and, on the other hand, the size of PVC particles of ternary systems is reduced while interaction with the matrix is improved (compare Fig.9b-c with 2b-c) A particle size reduction implies an increase of the specific surface and consequently an increase of the effective volume (so a viscosity growth), since more liquid adsorption will be possible Therefore, at high shear rates larger viscosities must be found for ternary systems, because morphological reasons: on one hand, the disruption of PVC network favors viscosity decline in binary blend, and on the other, the decrease of particle size supports viscosity increase in ternary systems a) b) c) FIG SEM microphotographs of extrudates a) 50/50 wt HDPE/PVC b) 50/50/10 wt HDPE/PVC/bCPE c) 50/50/10 wt HDPE/PVC/rCPE CONCLUSIONS Small-amplitude oscillatory measurements, creep and recoil experiments, capillary extrusion flow and shrinkage measurements, have been performed to elucidate the effect of block and random chlorinated polyethylene (CPE) on the rheological properties of ternary high density polyethylene 11 (HDPE)/poly (vinyl chloride) (PVC)/CPE system It is observed that the storage modulus, the complex viscosity and the steady state viscosity at low shear rates, decrease when a small amount of CPE is incorporated to 50/50 wt HDPE/PVC binary blend However at high shear rates, in experiments performed in extrusion flow, the trend is reversed and the incorporation of CPE to the binary blend increases viscosity The high melt elasticity of HDPE is severely reduced when this polymer is mixed with PVC, but when CPE is included as a third component, elastic recovery is considerably increased All these rheological results, which are independent of what kind (block or random) of CPE is used, are explained considering the morphological changes produced by CPE and during extrusion flow The viscosity lessening at low frequencies and shear rates, as well as the viscosity growth at high shear rates, observed when CPE is added to 50/50 wt HDPE/PVC blend, can be explained considering the following morphological changes: a) The inclusion of either block or random CPE in HDPE/PVC blend, disrupts PVC particle-particle aggregation b) During extrusion of binary blends, PVC particles are better dispersed as aggregate network is disrupted c) During extrusion of ternary HDPE/PVC/CPE systems, particle size is reduced and the particle-matrix interaction is increased Melt elasticity, associated to the rubbery deformation of HDPE, is drastically reduced in 50/50 wt HDPE/PVC blend denoting an anchoring effect or PVC particles during recovery A better dispersion of the particles, promoted by the incorporation of CPE to the blend, enlarges recovery In the aforementioned rheological effects and morphological changes, promoted by the addition of CPE to binary blend, we have not found difference between block or random copolymer REFERENCES D R Paul, C E Locke, C E Vinson, Polym Eng Sci., 13, 202 (1973) D R Paul and S Newmann, S., Polymer Blends, Academic Press, New York (1978) A Ghaffar, C 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Technology, in Advances in Polymer Science 96., Springer-Verlag, Berlin (1990) 30 G A Vinogradov, A Y Malkin, Rheology of Polymers, Springer-Verlag, Berlin (1980) 31 R Pal, E Rhodes, J Rheol., 33, 1021 (1989) 32 C McLuckie, M G Rogers, J Appl Polym Sci., 13, 1049 (1969) 13 LYÙ LỊCH TRÍCH NGANG Họ tên: Nguyễn Bá Hoàng Huy Ngày, tháng, năm sinh: 17/ 09/ 1982 Nơi sinh: Long An Địa liên lạc: Trung tâm Kỹ thuật Chất dẻo & Cao su – Sở Công Nghiệp, TPHCM 156 Nam Kì Khởi Nghóa, phường Bến Nghé, Quận 1, TPHCM QUÁ TRÌNH ĐÀO TẠO Năm 2000 – 2005: Học tập Khoa Công Nghệ Vật Liệu – ĐH Bách Khoa TPHCM, chuyên ngành polymer Năm 2005 – : Học cao học chuyên ngành Vật liệu Cao phân tử tổ hợp trường ĐH Bách Khoa TPHCM QUÁ TRÌNH CÔNG TÁC Năm 2005 – nay: Làm việc Trung tâm Kỹ thuật Chất dẻo & Cao su – Sở Công Nghiệp, TPHCM ... tử tổ hợp Khoá (Năm trúng tuyển) : K2005 1- TÊN ĐỀ TÀI: KHẢO SÁT KHẢ NĂNG TRỘN HỢP CỦA POLYOLEFINE VỚI PVC 2- NHIỆM VỤ LUẬN VĂN: Là khảo sát khả trộn hợp Polyolefine ( PE,PP) với PVC. .. này, khảo sát PE trộn hợp với PVC sử dụng chất tương hợp CPE (cloridepolyethylene), khảo sát PP trộn hợp với PVC sử dụng chất tương hợp PP-g-MA (polypropylene graft Maleic Anhydride), khảo sát khả. .. (EPDM) cho trình trộn hợp blend PE /PVC ; PP /PVC ; PE/PP Khảo sát hàm lượng chất tương hợp, thời gian trộn, nhiệt độ trộn ảnh hưởng đến tính chất lí hỗn hợp, Khảo sát tính chất hỗn hợp thay đổi hàm