Multicomponent Polymer Systems - ACS Publications

2 Compatible High Polymers: Poly(vinylidene fluoride) Blends with Homopolymers of

Downloaded by UNIV OF SYDNEY on May 3, 2015 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0099.ch002

Methyl and Ethyl Methacrylate J. S. N O L A N D , N . N.-C. H S U , R. S A X O N , and J . M. S C H M I T T Plastics Division, American Cyanamid Co., Stamford, Conn. 06904

The homopolymers poly(methyl methacrylate) and poly— (ethyl methacrylate) are compatible with poly(vinylidene fluoride) when blended in the melt. True molecular com patibility is indicated by their transparency and a single, intermediate glass transition temperature for the blends. The T results indicate plasticization of the glassy metha crylate polymers by amorphous poly(vinylidene fluoride). The T of PVdF is consistent with the variation of T with composition in both the PMMA-PVdF and PEMA-PVdF blends when T is plotted vs. volume fraction of each com ponent. PEMA/PVdF blends are stable, amorphous systems up to at least 1 PVdF/1 ΡΕΜΑ on a weight basis. PMMA/ blends are subject to crystallization of the PVdF component with more than 0.5 PVdF/1 PMMA by weight. This is an unexpected result. g

g

g

g

T n the early 1960s it was discovered in our laboratory (20) that poly(methyl methacrylate) ( P M M A ) and poly(vinylidene fluoride) ( P V d F ) were compatible when blended in the melt. Similarly, com patibility was found for poly (ethyl methacrylate) (ΡΕΜΑ) with P V d F . Blends of the fluorinated polymer with higher alkyl methacrylate poly mers, however, were nonhomogeneous. A t about the same time, Koblitz and co-workers (14) observed the formation of a "homogeneous physical mixture of P V d F and a solid P M M A resin," although they placed primary emphasis upon minor amounts of P M M A as a processing aid for P V d F . Our work, which is described below, was chiefly concerned with P M M A - r i c h systems, i n A

15 In Multicomponent Polymer Systems; Platzer, N.; Advances in Chemistry; American Chemical Society: Washington, DC, 1971.

16

M U L T I C O M P O N E N T P O L Y M E R SYSTEMS

recognition of the possible technological advantages inherent in having a light-stable, durable, polymeric plasticizer for P M M A (17).


Experimental Materials. The P M M A used was Acrylite H-12 molding compound (American Cyanamid C o . ) . This material was available as pellets. P V d F was Kynar 401 (Pennwalt Chemicals C o . ) , a powder of high but un specified molecular weight. ΡΕΜΑ was polymerized in bulk in the lab oratory from ethyl methacrylate (Rohm & Haas) by a laboratory scale adaptation of the P M M A process (22). Preparation of Blends. Blends were most conveniently made by fluxing a weighed amount of the acrylic component on a two-roll mill at 165°-170°C, followed by the addition of the P V d F and working for a few minutes until the blend was homogeneous. It was then removed from the mill, cooled, granulated in a Cumberland chopper, and either used in the form of irregular granules or passed through a small single- or twin-screw extruder to provide pellets or thin film. Differential Thermal Analysis (DTA) and Thermochemical Analysis (TMA). Differential Thermal Analysis ( D T A ) measurements were car ried out on a du Pont model 900 differential thermal analyzer. Measure ments on P M M A - P V d F polyblend samples annealed at room temperature were carried out by heating at 10°/minute over the range 25° to ca. 170 °C. Samples of melt extruded P V d F , annealed several weeks at am bient temperature, exhibited no definitive changes characteristic of the glass transition when heated at 10°/minute from —100° to 100°C, ap parently owing to the large portion of crystalline material. The samples of P V d F were heated to 190°C (which is above the melting region observed at 156°C) and quenched rapidly to —195°C These quenched samples were heated through the recorded range of —110° to 20°C. In four heating cycles, transitions in the range —43° to —47°C were ob served. The average of — 46 °C was chosen as T . A du Pont model 940 thermomechanical analyzer was employed for the T measurements on the P E M A / P V d F polyblends by the T M A tech nique. The sample specimens were cut from 30-mil, melt pressed sheets of the respective blends and examined by heating from —60° to 100°C at a rate of 5°C/minute. Sharp, unambiguous transitions were observed. g

g

Dilatometry. Conventional dilatometric equipment was used (10), J shaped with a 60 cm long, 1 mm diameter, graduated capillary, with the specimen section in an inverted position to reduce hydrostatic pres sure on the sample. After introduction of the sample, the sample section was sealed, and the dilatometer was evacuated to 0.01 mm H g and heated to 190°C at l°-2°C/minute. It was removed from the bath and cooled rapidly to the specified quench temperature, at which point the mercury confining liquid was allowed to flow into the evacuated dilatometer. In cases where the quench temperature was lower than the freezing point of mercury, ethanol was used as the confining liquid, and straight dilatometers of the same size were used. The dilatometric data for T —i.e., the point of inflection of the resulting volume vs. temperature plots for the P V d F - P M M A blends—are presented in Table I. g

In Multicomponent Polymer Systems; Platzer, N.; Advances in Chemistry; American Chemical Society: Washington, DC, 1971.

2.

Table I.

Dilatometric Data for PVdF/PMMA Blends Average T „ °C

Run No.

Quench Temp., °C

T . , °c

a b c d e

-30 -30 -30 -30 26

73.5 80.0 80.0 75.0 82.0

78.1

a b c d e

26 46 26 50 26

61.0 66.8 53.0 67.0 62.0

62.0

50

a b c

-30 -30 26

39.5 38.0 43.0

40.2

70

a b c d

-30 -30 -70 -70

0.0 5.0 1.5 3.0

2.4

PVdF,

% 15

35 Downloaded by UNIV OF SYDNEY on May 3, 2015 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0099.ch002

17

Compatible High Polymers

NOLAND E T A L .

Ultraviolet Exposure. A combination fluorescent ultraviolet and fluorescent blacklight lamp assembly (2) was used which yields an ultra violet spectrum similar to that of the ultraviolet portion of sunlight (9). Light Transmission. This was determined on a G E recording spectro photometer using thin films, followed by integration of the transmission over the visible range. Mechanical Tests. These were determined on an Instron model T M using thin films. Discussion Physical Properties of PMMA-PVdF and PEMA-PVdF Polyblends. The compatibility of these pairs of homopolymers is illustrated both by their clarity and by the fact that single glass transition temperatures, intermediate between the two homopolymer values, are observed. Τ data for the blends are shown in Figure 1. Results obtained by D T A on P M M A - P V d F blends which had been melt extruded and "an nealed" at room temperature appeared to be anomalous i n terms of the theory for glass transition of copolymers or compatible polymer blends (6). These data indicated a limiting value for T of ca. 40°-45°C. H o w ever, x-ray examination showed that samples with more than ca. 3 5 % P V d F exhibited a crystalline phase, indicating that some of the P V d F had precipitated. W h e n these systems were re-examined by dilatometry g

g


18

M U L T I C O M P O N E N T P O L Y M E R SYSTEMS


100

-20

-40 20 40 60 WEIGHT % PVdF IN •

80 BLEND

100

DETERMINED D I L A T O M E T R I C A L L Y

•

DETERMINED BY D T A ON A N N E A L E D SAMPLES

Ο Φ

M A N D E L K E R N et al DTA QUENCHED SAMPLE

Figure 1.

Glass transition temperature of PMMA-PVdF blends

with rapid quenching from the melt to —30° or — 70°C, a more con tinuous variation with composition was observed. A t least two different glass transition temperatures have been re ported for P V d F homopolymer. Owing to the large proportion of crys talline structure in this polymer and the rapid crystallization which occurs while heating quenched amorphous samples, it is difficult experimentally to obtain an unambiguous, well-defined second-order transition. Mandelkern, Martin, and Quinn (16) reported a value "below — 40°C" based upon an extrapolation of the T data for vinylidene fluoride-chlorotrifluoroethylene copolymers in accordance with the Fox equation (6), 9

1 Τα

Τη.

+

Tg.

where W and W are the weight fractions of the respective comonomers in the copolymer. They arrived at a somewhat higher T —35° to x

2

gy


2.

NOLAND E T A L .

19

Compatible High Polymers

—40°C, by dilatometric experiments on annealed P V d F . Peterlin and Holbrook ( 18) have reported a value of 13°C. Our own data, established by D T A on samples quenched rapidly from the melt, gave an average value of —46°C, in agreement with the extrapolation of Mandelkern and co-workers. Using this experimental value for P V d F and the value of 95 °C for P M M A , and plotting the experimental T data for the blends vs. wt % composition, the observed values show large deviation from the behavior which would be predicted by the Fox equation (Figure 2). It appeared


ff

-50 I 0

ι 20

ι ι 40 60 % PVdF BY WEIGHT

ι 80

1 100

Ο DETERMINED D I L A T O M E T R I C A L L Y •

DETERMINED BY DTA

-

PREDICTED BY FOX EQUATION

Figure 2. Comparison of experimental T values of PMMAPVdF blends with theoretical curve based on Fox equation G


20

MULTICOMPONENT POLYMER ι

1

I

SYSTEMS

I

\

à\ Λ" \ \I

\

-

\


-

\

\

\ \

-

\

\

,

.

.

\

\

\

,

" *

0 0.2 0.4 0.6 0.8 1.0 VOLUME FRACTION, PVdF IN BLEND $ •

DETERMINED DILATOMETRICALLY DETERMINED BY DTA C A L C U L A T E D BY MODIFIED K E L L E Y - B U E C H E EQUATION

Observed vs. calculated T of PVdF blends

Figure 3.

z

PMMA-

to us that the present situation involving a polymer blend might be de scribed more accurately by equations developed for polymer-diluent systems and represented a special case of the Kelley-Bueche ( 13 ) equa tion: rp _ °

VpTop((Zi — OLg) + v (a/ p

—

Multicomponent Polymer Systems - ACS Publications

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